Thursday, December 8, 2011

Heating in Residential Applications

Now that winter is upon us, we are getting the “How do I heat with a high ceiling?” questions. High ceilings in residences, especially here in Texas, are often the rule, not the exception. Heating is always a problem, especially from a 24 ft ceiling often found in Texas houses. Hot air rises and cold air falls, and with fixed air outlets and high ceilings this causes conflicts. In commercial spaces, I often recommend strategies not typically available in residences. These include using a VAV box to shut off interior located diffusers thus increasing the air flow from perimeter outlets, in heating.

Generally, residential diffusers are fixed deflection grilles. The use of an adjustable curved blade diffuser, such as the Krueger 180 (, is a much better solution, and should always be adjusted to direct the air horizontally, along the ceiling. Unfortunately, occupants are seldom aware of this, and often set the blades to blow supply air down into the space. Assuming the outlet is 24’ from the floor, this isn’t likely a problem if it is set up properly. Horizontally supplied air will have a much higher mixing ratio, result in more uniform room air temperatures, and will avoid drafts in summer. With high discharge temperatures in heating, however, there will likely still be stratification.

The most practical solution in residences seems to be the use of ceiling fans. While it depends on the room configuration, setting the fan to blow up in heating, while it would seem to be counter-productive, usually causes air to flow down the walls, and takes the warm air at the ceiling with it, and minimizes air motion in the room, which is usually objectionable when in heating mode. Chairs, of course, are best placed a short distance away from the walls. If a variable speed fan is employed in the central system, discharge temperatures in heating should be kept as low as possible, by running the fan at a high speed when heating from the ceiling, to minimize stratification.

In cooling, the ceiling fan is set to blow down, increasing room air motion (at least away from the walls) and this is often desirable, and may allow a slightly higher thermostat setting in the summer.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Thursday, December 1, 2011

The History of Krueger and Low Air Flow Measurement

When I (Dan Int-Hout) started working in this industry, in 1973, the standard of room airflow measurement was the “Anemotherm”, a hand held device specified for use in determining both diffuser throw and room air movement by the Air Diffusion Council. This device was a battery powered hot wire anemometer. In trying to meet a badly conceived minimum room air motion specification established by the GSA as part of a “Peach Book” performance specification, it was discovered that the Anemotherm was incredibly unreliable at air speeds below 100 fpm. The GSA spec was 20 fpm, minimum, at any point in the occupied zone! Later testing would determine that this was an unreachable goal with any air distribution system.

When I took over the Krueger Air Lab in 1982, we immediately embarked on a quest to get an accurate means to determine room air speeds. In my previous life at the research facility of Owens Corning Fiberglass in Ohio, in conjunction with TSI of Minneapolis, we had developed a complex, mutually perpendicular, twin-element anemometer requiring a specialized data acquisition system and sophisticated software to resolve low air flows from almost any direction.

TSI had developed a much more accurate portable hot wire anemometer somewhere around 1980. It was directionally sensitive, but accurate at 5 fpm. It was able to measure unidirectional airflows with excellent accuracy. It required significant time to properly record the highly variable low air speeds at the end of a diffusers throw. Room air motion, however, requires a probe less sensitive to air direction. The TSI linear probe was impractical in this area.

Working again with TSI, we came up with the idea of using a small heated sphere, instead of a linear element, and after solving the temperature compensation problems, TSI released the first omni-directional anemometer. It was accurate down to 5 fpm from almost any direction, but the output was a complex 4th order polynomial curve, different for every probe. At Krueger, we developed the first operational software for this new omni probe, utilizing the recently released MS-DOS operating system and the universal PC platform. We used a prototype data acquisition board from Burr Brown of Tucson, and a TSI provided Compaq “luggable” computer to develop effective software which stored calibration data and resolved the complex curves. TSI showed it at an ASHRAE show in 1984. The software development was finally spun off as a private operation, when Krueger management at the time (Leo Krueger) decided he didn’t want to invest in software development. The anemometers in the lab today are a direct descendent of that development and have become the industry standard. The software, however, went away in a few years as more advanced data acquisition systems (such as Lab View) took over the tasks. (Leo was correct!)

Prior to the development of the Omni probe, measurement of low air speeds was incredibly time consuming and both inaccurate and non-repeatable. After we started using the new equipment, however, we discovered that measured throw data for air outlets was typically much longer than previously reported (and could be completed in much less time). The result was a complete retesting of throw values with now much more sensitive (and accurate) devices. Manufacturers dropped Air Diffusion Council membership around that time, in favor of ARI; ASHRAE Standards were updated to require better instrumentation. The result is much longer reported throws for all devices, especially linear slots, which tend to have very long throws, across the industry.

Data acquired under the older ADC test code should be considered obsolete and will likely under report 50 fpm throw values. The new omni-probes, which are now internally linearized (making data acquisition very easy), allow for rapid measurement of the highly turbulent room air speeds and low diffuser throw air speed values with data being fed directly into spreadsheets for rapid analysis.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, November 28, 2011

End Reflection

Soon, every manufacturer of VAV terminals will be changing their discharge sound data to comply with a change in the way discharge sound in the reverb room is measured. This change came about as the industry started to measure octave band sound generation for many products. VAV terminals have been certified through AHRI for sound levels (for over 20 years); several years before that, it was through the Air Diffusion Council. The new test method for non-VAV terminals is AHRI 260. Part of the procedures call for adding the calculated “End Reflection” to the measured sound levels. End Reflection is a phenomenon that occurs when sound travels through a duct and encounters a rapid change in area. Some of the low frequency sound is reflected back, effectively cancelling some of the sound waves coming down the duct.

End Reflection has been a part of AHRI 885’s sound calculations from its inception in 1989. Originally, 885 used an ISO equation, but when ASHRAE completed a thorough analysis in a research project a few years ago, 885 adopted the ASHRAE equation (which was very similar to ISO). When testing discharge sound in a reverb room, the duct connecting the unit to the room is specified to terminate flush with the inside wall of the test chamber. There is an end reflection in this installation, but the ADC and AHRI procedures for VAV boxes were developed long before the ASHRAE or ISO equations had been verified. Now, however, it’s time to play catch-up.

AHRI has decided that all member manufacturers shall now include end reflection in their discharge sound data and must update the Certified Directory and on-line catalogs by January 1, 2012. The next printing of their catalogs shall also be corrected.

The impact will be to show a reported, calculated (estimated) NC increase of as much as 10 NC. The effect is greatest for the smallest units. The units won’t be any louder, but the data will show an increase. This will, no doubt, cause much concern. However, our experience is that discharge sound is seldom a cause of complaints. Engineers will need to modify their specifications accordingly and I expect there will be a lot of discussions. It should be an interesting start to the new year.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, November 7, 2011

"What type of air distribution should I use?"

I get these types of calls all the time. Typically it is a young engineer, often an EIT, who has no idea what is the best way. Often, I get a drawing showing a floor plan or space layout. The problem is that there are other issues that need to be understood.

One example is the theatre - typically stepped, with very high ceilings. It would seem that underfloor or displacement ventilation would be an obvious solution, especially as they are very quiet. But we need to know where the project is, how much heating will be required (typically not much), and what type of air handler is contemplated. Both displacement and underfloor require supply air no colder than 65F, but with a dew point of 55F. This means a typical DX rooftop will be challenged.

Overhead has the problem of getting any heat down to the floor for the warm-up period, but can employ low cost package rooftop systems. Typical ceiling diffusers are impractical to adjust between seasons and the flow to ceiling distance is quite different in the rear than near the front of the theatre.

There are solutions to all these issues, of course, but without knowing a lot more about the project, providing guidance will be difficult.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, October 31, 2011

People Still Don't Get It!!

I spent last week in Boston calling on engineers with our rep there. As I always do, I asked the question “What does ASHRAE recommend as the maximum delta-t between room and discharge, when heating from the ceiling?” Out of 60 engineers in 7 engineering offices, only one individual knew the answer. Sadly, this has been the pattern for as long as I have been asking the question.

The answer is, of course, 15 degrees-F. Discharges greater than 90F in a 75F room (87 in a 72F room) are going to result in significant temperature stratification in the room. ASHRAE Standard 62.1 requires that when this delta-t is exceeded, the system must increase the minimum ventilation air to the space to account for the inevitable loss of ventilation to the room due to short circuiting into the return air plenum. In Mass., as in many states, this is code, as the Ventilation Rate Procedure of 62.1 is referenced in the 2009 International Mechanical Code, which has been adopted by the state.

More importantly, ASHRAE Standard 55 (Occupant Comfort) cannot be met with high discharge temperatures. The 55 Standard only allows 5.4F vertical temperature difference between 6in and 6ft. I have never witnessed a test where this requirement was met with greater than 15 degree supply-room differentials, and I have conducted over a thousand such tests over the past 35 years.

While not code, ASHRAE 55 should be a concern to everyone. Occupant salaries in many buildings are at least $200/square foot/year. A building that uses more than $2/square foot/year in energy is a poor performer. BOMA has continually stated that the number one reason for not renewing the lease in a high rise office building is “occupant dissatisfaction with the environment”. Considering how few engineers apparently understand the very basic idea that hot air rises, I suppose this is not surprising. We continue to see VAV box schedules with design discharge temperatures in excess of 120F.

I will continue to pound on “the rules” as I call on engineers around the country. The ASHRAE Journal article on overhead heating was recently reposted as a link in the HVAC news weekly e-mail, and a version can be found at

Authored by: Dan Int-Hout, Chief Engineer Krueger

Friday, October 21, 2011

ASHRAE 113 & Standard 55

It has come to my attention that a number of engineers are requiring the use of ASHRAE Standard 113 to verify compliance to ASHRAE Standard 55. That is not likely to be a successful venture, as the 113 Standard is really intended as a laboratory method of test.

I was the original author of Standard 113, back in 1979. It was originally an appendix to an ASHRAE Technical paper on how to get repeatable measurements of room air motion in an office space mock up, written to prove compliance, or in this case, non-compliance, to a GSA specification. The tests conducted under the protocol which became Standard 113 proved that in fact it was not possible to meet the GSA specification with any air distribution system. The GSA subsequently modified the specification, and shortly after dropped the requirement entirely. It also proved that getting repeatable results required very expensive instrumentation, modifications to the controls of the space being measured, and the addition of simulated loads to maintain the steady-state conditions required for the measurements, which often took an hour or more. For a number of reasons, it is unlikely that one can conduct a true ASHRAE 113 test in an office space.

I was Chair of ASHRAE 55 Standards committee when the 2004 standard was released. Compliance paths have always been a goal, but have never been fully or properly defined, due to the inherent difficulties in measuring the highly variable and often non-steady state conditions that exist outside of laboratories. We are still working towards that end and are developing compliance paths for different types of air delivery systems. That is still a work in progress. They will not, however, include a requirement to conduct air distribution tests per ASHRAE 113.

The relationship between measures of room air motion and Standard 55 are not clearly spelled out in the literature. ADPI (Air Diffusion Performance Index) can be predicted from manufacturer’s throw data and an analysis of diffuser spacing from tables in Chapter 20 of the ASHRAE Fundamental’s Handbook. ASHRAE 113 data can, and has been used to calculate an ADPI under steady-state conditions. An ADPI of 80% or greater will ensure that there is less than the ASHRAE 55 vertical temperature stratification limit of 5.4 degrees F in the lower 6 feet of a space. That is only a small part of the Standard 55 requirements, however.

The likely steps to prove compliance to Standard 55 will involve temperature difference measurements only, as these are much more stable than velocity measurements, and can easily be taken in occupied spaces. Air speed measurements are so highly affected by local loads that any measures are unlikely to be repeatable or meaningful, in practice. There may be some meaningful data obtained at the midpoint between diffusers to look for jet collisions at high air flow rates, or under diffusers at low air flows looking for excessive drop (dumping). These would involve some visualization and single point measurements, a type of measurement not included in ASHRAE 113.

In short, the only practical way to place ASHRAE 113 in a specification is to require its use in a full scale mockup to verify the predicted ADPI from the ASHRAE handbook table calculations. This will likely be a very expensive test and should not be employed except for very large projects where the cost might be justified.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, October 10, 2011

Post Greenbuild Show

I spent last week in Toronto at the Greenbuild Product Show and Conference. We had a product booth again this year and showed examples of our Chilled Beam, Displacement, and Underfloor products, which are widely considered to be “green” products. In reality, of course, everything we make can be utilized in a “green” application. It’s all in the way they are used, of course. Once again, the product show was largely related to non-HVAC products, as it focuses on building materials and green software vendors.

I presented my portion of the panel talk “Can we have our cake and eat it too? Balancing Energy Efficiency and Occupant Comfort ” The room was packed with over 250 attendees. My portion was to present the history of bad decisions made in the name of energy conservation that resulted in poor occupant comfort (and no energy savings). The others on the panel discussed how we are getting occupant feedback on new projects, and proved that one can actually save energy with comfortable spaces. There were a number of interesting questions asked, and I believe we covered the subject well.

If you have been following my blog, you will know that I was concerned that the USGBC is putting Global Warming and energy use ahead of occupant needs, in their hierarchy of importance. Fortunately, I think we have convinced the Energy folks enough that they have finally agreed to increase the weighting for issues regarding comfort!

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, August 22, 2011

Visiting Reps in Montana

I spent the week travelling across Montana calling on our reps and doing presentations to a number of engineers. On Friday, I did an all day seminar on the Basics of Air Distribution for the NEBB organization. A number of engineers attended along with the NEBB air balancers. The presentation was well received.

Afterword, several balancers remarked that they wish the engineers who specify the work that they do had the benefit of the discussions I presented. They were pretty basic. It appears that many engineers, especially the younger ones, haven’t had any training in the basics of diffuser placement and proper selection. At least, in the eyes of the balancers who have to make their projects work.

I guess we need to get back to basics with the younger crowd, who in the complexity of computer aided design may lack general common sense and a few simple rules that can be obtained through proper education as well as experience.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Friday, August 12, 2011

ASHRAE Standards

I have been asked a number of times about why Addenda A to the 62.1 2010 Standard isn’t available from ASHRAE. This addenda gives Displacement Ventilation credit to UFAD diffusers if the throw to 50 fpm is less than 4 ft, on the assumption that the ventilation will remain in the occupied space, and is based on ASHRAE sponsored research using both physical measurements and CFD calculations. The DV credit allows a reduction in ventilation (outdoor) air of 20% (divide the minimum rate by 1.2).

ASHRAE Standards that are on “continuous maintenance”, which include Standards 90.1, 55, 62.1 and several others, are modified by addenda through the ASHRAE public review process. Once an addenda is approved, it becomes a part of the Standard. This has caused a number of complaints that it was hard to stay up with what constituted the “current” standard. As a result, ASHRAE has decided to ‘bundle’ addenda into a single release, at the mid point between reprints of the standard. This is typically 18 months. So while Addenda A to 62.1 was approved (there were no comments) before the 2010 Standard was released, it will not be printed and available for probably another 6 months. The change is noted below:

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, August 1, 2011

LEED 2012 Review

LEED 2012 is now out for a second public review. The section that most affects us in the HVAC/Air Distribution business is the IEQ credits. The following is excerpted from the USGBC announcement:

Indoor Environmental Quality
The Indoor Environmental Quality credit category has undergone significant structural reordering for second public comment, but retained familiar requirements in the new credits. This reorganization streamlines the credit category and more effectively addresses overlapping goals of the former credits.

Achieving the Indoor Environmental Quality credits now has more direct benefit to occupants by comprehensively addressing environmental quality impacts. The weightings tool helped to highlight that many of the Indoor Environmental Quality credits were competing with themselves for points when addressing the human health impact category. The reorganization more clearly shows that the category has 4 macro themes, ventilation, lighting, acoustics, and general occupant experience, all of which have holistic credits addressing how buildings can enhance health, safety, productivity, the ability to learn, and also continue to bring biophillic “outdoor” design elements to built spaces.

These changes include:
--- Thermal Comfort credit follows the Assessment credit so that all ventilation-related credits are in order. Interior Lighting is now in order with Daylight.

--- Acoustics. The credit has been significantly re-written with more exact requirements and more referenced standards for all of the sections.

I think the really important thing in the 2012 proposal is that by stating that “HVAC noise shall not exceed…”, and providing a couple of calculation paths, especially directly referencing AHRI 885, will go a long way for making the Engineering community sign on to this requirement. The specification of construction details instead of a ’guestimate’ of reverb time is also a major step. All the engineers I call on (I see about 1000/year) were concerned about the open resulting sound requirement, as there are a lot of sound sources they can’t control.

I encourage all of you reading this that are involved in the LEED process to review the 2102 draft, and would encourage your positive comments towards the acoustic requirements.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Thursday, July 21, 2011


There has been a lot of discussion about the impact of LEED Credit EQ5 and the necessity of a MERV13 filter on recirculated air devices (such as fan coils, Fan Boxes and even Chilled Beams). A MERV13 filter is likely to seriously degrade the performance of these devices. After a lot of back and forth, the following is the revised language which has been proposed, and is assumed to be adopted immediately. The wording is the same for Retail Commercial Interiors and Schools.

The impact is that to gain the point, only outdoor air must be MERV13 filtered, somewhere in the path between the outdoor air inlet and the occupant.

NC - EQ Credit 5: Indoor Chemical and Pollutant Source Control
1 Point

To minimize building occupant exposure to potentially hazardous particulates and chemical pollutants.

Design to minimize and control the entry of pollutants into buildings and later cross-contamination of regularly occupied areas through the following strategies:

--- Employ permanent entryway systems at least 10 feet long in the primary direction of travel to capture dirt and particulates entering the building at regularly used exterior entrances. Acceptable entryway systems include permanently installed grates, grilles and slotted systems that allow for cleaning underneath. Roll-out mats are acceptable only when maintained on a weekly basis by a contracted service organization.

--- Sufficiently exhaust each space where hazardous gases or chemicals may be present or used (e.g., garages, housekeeping and laundry areas, copying and printing rooms) to create negative pressure with respect to adjacent spaces when the doors to the room are closed. For each of these spaces, provide self-closing doors and deck-to-deck partitions or a hard-lid ceiling. The exhaust rate must be at least 0.50 cubic feet per minute (cfm) per square foot with no air recirculation. The pressure differential with the surrounding spaces must be at least 5 Pascals (Pa) (0.02 inches of water gauge) on average and 1 Pa (0.004 inches of water) at a minimum when the doors to the rooms are closed.

--- In mechanically ventilated buildings, each ventilation system that supplies outdoor air shall comply with the following:

1) Particle filters or air cleaning devices shall be provided to clean the outdoor air at any location prior to its introduction to occupied spaces.

2) These filters or devices shall be rated a minimum efficiency reporting value (MERV) of 13 or higher in accordance with ASHRAE Standard 52.2.

3) Clean air Filtration media shall be installed in all air systems after completion of construction and prior to occupancy.

--- Provide containment (i.e. a closed container for storage for off-site disposal in a regulatory compliant storage area, preferably outside the building) for appropriate disposal of hazardous liquid wastes in places where water and chemical concentrate mixing occurs (e.g., housekeeping, janitorial and science laboratories).

Authored by: Dan Int-Hout, Chief Engineer Krueger

Thursday, July 7, 2011

Rules of Thumb

Over the years, Engineers develop “rules of thumb” for quick estimates of engineering issues. We manufacturers often do the same. Here are a few of the ones I use in looking at air distribution issues:

Buildings cost about $2/sf/year for energy. This is of course, a wild guess. I’ve been using it for 20 years. It is likely less than this in modern buildings, but I’m not getting much push back from engineers. If you take 1 watt/sf * 8670 hours/year, you get 8.6 kwh/sfy. At $0.10/kwh, that is less than $1/sfy. I said this was rough. I recently visited a building in Canada that claimed less than 1W/sf HVAC load.

Currently, a commercial building HVAC system’s first cost is about $30/sf. It was $15-20 when I started in this end of the industry, about 1980.

Building loads are typically designed at 1 cfm/sf. With 55F supply air in a conventional overhead mixing system, that comes to 22 BTUH/sf load. I suspect most office building loads are 1/3 of that most of the time.

The ASHRAE 62.1 default ventilation rate is 17 cfm/person. At 55F (typically required to maintain a minimum of 60%RH), that is likely more BTU’s than a person generates, and likely has enough left over to handle his computer.

Most diffuser reported NC’s are 5NC below what you should expect. There is an ASHRAE research project that will provide more definitive data, but catalog data is collected with 10 diameters of straight duct, not the typical flex inlet. In addition, it assumes 10dB room attenuation in all bands, which is also unlikely. I recommend adding 5 NC to all manufacturers ceiling diffuser data.

If I can just barely hear a diffuser in an operating environment, it’s about NC=35. Specifications requiring NC 25 or less are typically too conservative, except in very quiet environments. Remember, however, that you add 3NC each time you double the number of similar diffusers when they are all in hearing distance.

75fpm throw is affected by temperature by about 1% /degree delta-t. This rule of thumb allows calculation of jet projections at differing temperatures. Cold air falls further, hot air falls less, compared to isothermal throw, which is what most manufacturers catalog. Along a ceiling warm air travels further.

I’m sure I’ll think of some more. Stay tuned….

Authored by: Dan Int-Hout, Chief Engineer Krueger

Thursday, June 30, 2011

Montreal ASHRAE Meeting Updates

Well, another ASHRAE meeting is behind us. There are a few interesting items to report:

Standard 55 (Thermal Comfort) is being made to be “more mandatory”. As it is referenced in many codes, there has been a concern that it is a bit wishy washy in its requirements. To clear up the concerns, changes are proposed that will make it clear that Standard 55 is intended to standardize how one calculates thermal comfort, not which conditions will be required. It may help the code guys, but will likely still be misinterpreted.

A study ongoing through the Thermal Comfort Technical Committee (TC 2.1) is showing, yet again, that buildings are operating at far lower loads than they are designed for. In many cases, VAV systems are showing satisfactory performance at less than 0.3 cfm/sq. ft. Airflows greater than that are causing systems to run in reheat in interior/cooling zones. This is further evidence that part load operation is the predominant condition and that we need to be designing for that eventuality.

The results of the Texas A&M study on Series vs. Parallel / ECM vs. PSC motor study has been donated to both ASHRAE and AHRI at the summer meeting. It is hoped (indeed expected) that these results (partly funded by Krueger and two other manufacturers) will result in a rewrite of Appendix G of 90.1 which currently favors Parallel boxes, to the exclusion of Series flow types.

AHRI’s ACDD section, which covers VAV terminals, has updated their Operations Manual. We will be seeing a change in everyone’s discharge sound performance in the next year to account for end reflection in the reverb room. Other standards take this phenomenon into consideration, but VAV boxes, which have been using test methods developed before ASHRAE, had a full understanding of End Reflection, do not. The result will be between 3 to 7 NC increase, depending on unit discharge duct size, in reported, and certified, discharge sound levels. The units won’t be any louder, but the sound data will increase. Typically, discharge sound is seldom critical, especially when there is lined duct present between the box and the diffuser.

TRG7 / UFAD which is a committee rewriting the Underfloor design manual (no longer available from ASHRAE) has uploaded all the first draft documents to a website where committee members can propose revisions and review changes to the entire draft. We should be able to have an approved document to turn over to ASHRAE (which will do an independent review) after the Chicago meeting. This is the first design guide written by a technical committee, not an independent contractor. Fortunately, I am rolling off as chair of this committee after this meeting and hand the reigns over to the very capable Jim Mergerson of Burns and McDonald of Kansas City, who has many successful UFAD projects to his credit.

I’ll be glad to get back to the USA, where at least I can read signs directing me where things are!

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, June 20, 2011

Accurate Sound Data Matters

For years, sound has been specified in terms of NC, or noise criterion. ASHRAE has published tables of recommended NC levels for many years, which are often the basis if sound specifications. A few years back some acousticians were promoting RC, or Room Criteria, and for a while, ASHRAE replaced the NC table with RC, which had the same numerical ratings, but added a letter (always an “N”) which described the shape of the sound curve. RC never took off in engineer’s specifications; it was flawed in that it didn’t really properly describe the sound shape of devices which contained fans (but worked ok for air outlets).

Fast forward to today where ASHRAE lists both NC and RC; however, most specifications still require NC. The problem with NC is that it is both a single number rating and an estimate based on assumptions. Manufacturer’s don’t actually measure NC. We measure octave band Sound Power in a reverb room and then use standard assumptions (outlined in AHRI Standard 885, 2008, Appendix E) to estimate NC (or RC or dBA or whatever is specified), as required by AHRI when data is presented in a catalog that also has certified data.

We can only guarantee Octave Band sound power as measured in a reverb room. In fact, VAV box sound levels are certified by octave band at a certification point and checked annually. At present, only VAV boxes are certified for sound generation through AHRI. Fan Coils, WSHP’s, and Chilled Beams are proposing to do so in the future, also in a reverb room.

Specifications, however, seldom require meeting stated maximum sound power levels, as would seem logical, since they could be both validated and verified. Instead, we typically see schedules based on manufacturer’s calculated NC values, and sometimes the required assumptions are listed, but more often not. This, of course, allows the suppliers to use whatever assumptions they wish, with the potential to underestimate the sound that will result in the space.

Worse, we see schedules generated by software that list NC for a single manufacturer’s device (the “basis of design”), often at very low NC levels for small units at low flows. Requiring an NC=21 in an office, because that is what was spit out of a manufacturer’s computer program, is pretty silly, as sound levels less than an NC=30 can’t likely be heard in most environments. There is often a note requiring the addition of a silencer if “NC falls below scheduled values”. Silencers are likely ineffective at the low frequencies that set the NC, add cost and pressure drop, and simply don’t make sense.

Finally, with fan powered terminals, which have an induction port open to the plenum, radiated sound levels will be significantly affected if the insulation inside the units is covered up by foil, or worse, sheet metal. We have seen increases as great as 12 NC in some reverb room tests. When the specification calls for the insulation to be covered up, and someone submits data with exposed insulation, there is likely to be a big surprise when the job is commissioned.

And the surprises will be discovered far more readily these days, as one can now download a real time sound analyzer, often for free, as an iPhone app! In the past, in order to validate a space sound level, it was necessary to hire someone with the real time sound analyzer equipment, which often costs at least $4,000. That also meant hiring the services of the guy who owned the equipment. Today, however, it seems everyone occupying the space can do their own sound analysis.

So in short, we need for engineers to produce meaningful and verifiable sound specifications, based on real needs (not some manufacturer’s computer output) and based on real product options, such as interior linings and expected inlet pressures. The AHRI 885 spreadsheet is available on the Krueger website ( to get realistic sound estimations, as well as a reverse spreadsheet ( to determine realistic octave band sound power limitations.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, June 13, 2011

Control Stategies for ECM Fan Powered VAV's

There are lots of opportunities to take advantage of ECM motors. Assuming you have the ability to custom program a DDC controller on a series (or parallel) fan powered box, the ECM motor can easily be controlled using an analog output on the controller and the analog input control card on the ECM motor.

An ECM motor's efficiency increases, in terms of watts/cfm, as it is turned down. A PSC motor doesn't share this advantage. At full flow, however, a PSC motor may use less real power than an ECM, so the secret is to minimize the fan airflow rate. With a series fan box, however, it is important to keep the fan flow equal to or greater than the primary air flow to avoid over pressurizing the unit and causing primary air to spill into the return air plenum. The ECM motor can be (and typically is) programmed for pressure independent operation, making the fan airflow directly controllable with an analog signal, without the need for a feedback control loop.

There are limits, of course. The main limit is the ability of the supply diffuser to properly provide uniform conditions in the space, which degrades at very low airflows as the cold air supplied at the ceiling falls into the space instead of hugging the ceiling. (Often referred to as "dumping", we have recently learned of alternate terms including "premature ceiling separation" and "failure of coanda". My marketing department prefers the term "horizontally challenged").

The best way to determine a given diffuser's turndown is to use ADPI analysis. I have a couple papers on this process on our website.

We are going to present some ideas on increasing occupant productivity at Greenbuild in Toronto in October. Without giving it all away in advance, occupant productivity has been shown to be greatly affected by ventilation, so one should strive to maximize ventilation. There is a trade off in energy, however. Conditioning outside air is expensive when it is humid, too hot, or too cold. Often, economizer operation has been abused by allowing space temperature and humidities to wander outside acceptable (or optimal) conditions, in an effort to minimize energy use.

Fan boxes are likely required in cold climates to manage perimeter zones when heating from the ceiling, if one is to comply with both Standards 62.1 and 90.1 (and many codes). By utilizing the variability, and pressure independence, of ECM motors, one can provide high ventilation rates when conditions permit, and reduce them when outside conditions are less favorable. Further control options can be realized if the terminal is supplied with a non-condensing (sensible) cooling coil on the induction port and DOAS air provided to the primary air valve. Alternately, a second DOAS inlet can be provided on a series fan box. Controlling wither two inlets or two coils can be a challenge, so Krueger offers a contact closure / 4 position, fresh air, pressure independent actuator option.

We also have a couple engineers using a parallel box with ECM motor where the fan is designed to operate at all times. This allows the induced air to be independent of the primary airflow rate, offering a number of advantages in controlling room conditions.

In my opinion, occupant satisfaction (and productivity) will be optimized when ventilation air is provided at the highest possible rate, outside conditions permitting, and when the system is operated within the limitations of the air distribution system installed in the space. Maximizing ventilation in the morning, then reducing it as the temperature rises during the day, is an excellent strategy. It will require a clever control strategy, taking advantage of both sensors and equipment options.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, June 6, 2011

A Visit with Engineers in Philly

I recently had the opportunity to visit a number of engineer’s offices in Philadelphia. We saw over 50 engineers in 7 different offices on this trip. It was great to get back to Philly where we hadn’t had a strong engineering presence for some time.

Philly is experiencing the same construction doldrums that the rest of the country is having, but I was glad they made time for me to visit and bring them up to date on the latest proposed LEED changes along with the impact of Standard 62.1 VRP (Ventilation Rate Procedure) being adopted as code by the IMC, and Pennsylvania as well.

Once again, I asked how many knew the recommended maximum delta-t when heating from the ceiling. I estimate I have asked 12,000 engineers this question over the past 10 years. The response in Philly was on par with the rest of the engineers I have questioned. Out of 57 engineers questioned, only 6 knew the answer (or were willing to guess, and guessed correctly). The answer, of course, is 15F delta-t (difference between room and discharge). Higher than this and two bad things happen:

1) ASHRAE 62.1 requires that 25% more outside air be brought into the zone being heated, to compensate for the ventilation air short circuiting that is sure to be happening as hot supply air is drawn into the ceiling returns and

2) ASHRAE 55 (Thermal Comfort) vertical stratification limitation will be compromised, and one cannot claim compliance to 55 in a LEED project.

ASHRAE 62.1 is a prerequisite for any LEED building, and code in Pennsylvania, so that is not optional. In LEED for 2012, outside air will likely require to be monitored (at least with VAV systems, so compliance can be verified.

We also discussed the impact of oversizing diffusers with VAV systems and the result at low flows. While the common term for the dropping of cold air into the occupied zone is “dumping”, I informed them, as I usually do, that diffusers may exhibit “excessive drop”. I was informed of a couple alternative terms for this phenomenon. These include:
- Premature Ceiling Separation (“PCS”)
- Failure of Coanda (“FOC”)

I have since been informed by our marketing department that the politically correct description is “horizontally challenged airflow”.

I’m glad that confusion is finally cleared up.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, May 23, 2011

Mid-Year Predictions Follow-up

In the interest of full accountability, I have provided an update to my January top 10 predictions, as we are half way through the year.

1. LEED 2012 will be approved, pretty much as it is in its first public review.
Update: Second public review due out in a couple of weeks. Nothing major proposed different - ventilation will likely be a restaurant menu – 1 from column A….

2. The ASA Classroom acoustics recommendation (essentially NC=26, ANSI 12.60 ) will become a requirement in many local codes and may be a part of the next IBC. It will also be a requirement of the ADA governing bodies, forcing a redesign of many school HVAC systems
On track. Good news is that AHRI 885 is designated as a primary method of estimating sound levels in schools and other places as well.

3. Over my objections, the ASHRAE Thermal Comfort Standard (55-2010) will be rewritten into code language. I predict this will result in gross misuse and misinterpretation of the requirements and will make lots of money for trial lawyers. (I hope I’m wrong on this one.)
A sub committee has been formed to implement this proposed change. I volunteered to be on it.

4. With any luck, we will get a rewritten ASHRAE UFAD Design Guide out of committee at the summer meeting. The current manual has been pulled from the ASHRAE bookstore following complaints, most noticeably from the GSA, over lack of discussion of the potential negative issues with this design concept.
Final first draft has been assembled and we will review it at the Montreal meeting. Really good news is that I will move to Vice Chair after the June meeting.

5. Displacement Ventilation will see significant use in classrooms (it’s quiet, see item #2 above).
This trend continues.

6. Chilled Beams will continue to be the “darling” of innovative engineers. We will not see validation of the calculated energy savings from this relatively new technology. That will not, however, prevent estimates of significant energy savings, resulting in LEED points.
Still no peer reviewed data on energy savings with this technology. Developing AHRI and ASHRAE test methods should put to rest some unfounded performance claims.

7. For the umpteenth year in a row, BOMA will state that the number 1 reason for not renewing the lease in high rise buildings is “occupant dissatisfaction with the building environment” (ie: comfort). See item #3 above.
Still waiting for the 2010 data from BOMA.

8. The market for HVAC components will continue to be relatively flat with local ups and downs.
It's looking better in some places, still flat in others. Fortunately, no major downturns seen, but pricing pressure is pretty grim everywhere.

9. VAV overhead air distribution will continue to be (by far) the most used system in new buildings.
Unchanged. While some other systems are seen in some specifications, most continue with the tried and true overhead VAV designs.

10. The Cowboys will continue to disappoint their fans.
I can’t even predict if there will be a season this year.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Tuesday, May 17, 2011

Observations of a Canadian LEED Certified Building

While I was in Canada a couple weeks ago, I was given a tour of an almost completed Quebec Government building. The building was an extension of a combined train station / administrative office complex. The addition was the equivalent of the Department of Transportation in the US (I have no idea how to translate that into French).

Language barriers aside, our tour guide was a manufacturer’s rep who had sold all of the air distribution in the new addition. We even got to meet the lead design engineer, as the building was going through the commissioning process, and he was overseeing that process. I was impressed with several things in the new building:

1) The addition was a very fast track construction project, completed in what may be record time, with 6 floors of offices and a parking garage. People were working in the building before it had been commissioned!

2) The open plan office had no closed offices at the perimeter, all conference rooms and executive offices were located in the core, resulting in excellent visibility.

3) There were no desks against the windows, and the spaces near the windows were all corridors.
Partitions were low height, except for some separating operational areas, and these 6ft partitions were all perpendicular to the window wall, allowing excellent daylighting into the interior.

4) The south facing wall had exterior shading and an interior light shelf (with a gap to allow airflow down the windows), again to increase daylighting into the interior.

5) The HVAC system was ECM powered fan coils with VAV boxes controlling ventilation air into the fan coils. The lead engineer said the result was less than 1Watt/SF load, and there were no true air handlers, only DOAS units bringing in and conditioning outside air.

6) The zone air distribution was European style fully adjustable radial pattern 2x2 fixtures with 2’cube plenum boxes on top. These constant volume air devices have very high induction and resultant short throws, and appear to minimize jet collision and resultant downdrafts. Air flow rates were relatively low, less than 1cfm/sf in interior zones.

There were also some issues:

1) It was also reported that the combination of ECM motors and digital lighting ballasts resulted in a building power factor of 0.85! As there is a power station in the basement, power was re-conditioned on site.

2) The air outlets have relatively high pressure drop (0.5”) and are at least 5x the cost of typical office diffusers in the US. This cost is typical in Europe, but would be considered prohibitive in most US designs. There is little data on the performance of this style of diffuser in terms that are comparable to US designs; nevertheless, we will be testing a unit to get comparable performance data.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, May 9, 2011

Comfort & Energy Savings

I was asked to post some thoughts to my fellow presenters at the upcoming Greenbuild, in October, in Toronto, on my part where we are doing a "yes, you can have comfort and energy savings" talk. Here is what I sent them:

I've been stuck in rainy Quebec province, with limited internet access, and time, but I've been noodling the subject of the somewhat diluted 30% proposed ventilation credit (for LEED 2012)and the "same degree of ludicriness as bicycle racks" comment we got from one of the energy mavens.

I won't try to come in on naturally ventilated buildings as I suspect they represent about 1% of available spaces.

I am of course concerned about the low comfort scores LEED buildings are getting, as its hard to argue for the availability of comfort options if we can't seem to be able to achieve it anyway.

I fear that part of the problem has been the emphasis on energy at the expense, or just plain ignorance of, comfort requirements. Nonetheless, I believe there are innovative options available to both improve energy efficiency and achieve a level of comfort. I am concerned that the calculations of energy savings are greatly overplayed, and never surprised when they aren't realized.

The reality is that when folks are not comfortable they don't just "make do". They bring in heaters, and sometimes fans, to increase their comfort level. Both are huge energy wasters, as the energy they use generates heat which then goes to the chiller, costing twice the energy used by the stopgap measure.

All that aside, I'd like to focus on the potential for innovative systems to maximize ventilation when outside conditions permit, minimize it when it doesn't, and ensure that economizer isn't mis-applied (pushing the economizer envelope resulting in high humidity in the space, as was alluded to by C Dorgan in one of our recent phone calls). At the same time, the real issue, I believe, is building operations in part load conditions (which are likely 90% of the time).

System design is not an unknown science. We know how to design for effective part load operation, but seem to get lost in design load strategies. Energy costs about $2/sfy in most climates (likely less in California). Saving half the energy (probably unlikely) has a really long payback in a building that costs $10/sf extra to build. At $30/sf, the payback is 60 years. Yet building owners continue to sign up for silly stuff. I suggest we get real, and discuss opportunities to design buildings without added first cost that actually work.

Radical, huh?

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, April 27, 2011

Engineering Specification Observations

I spent a few days in Albuquerque last week, doing an ASHRAE lunch and calling on mechanical engineers. I came away with some general observations about the market there, and on the current state-of-the-art in specifications.

1) New Mexico is apparently very dependent on government work, with several military bases and a couple Federal research laboratories keeping business at least flat. The state of Federal specification/requirements is in some flux. A couple years ago, it seems UFAD was the “advanced technology”, and today it is Chilled Beams. So far, most Chilled Beam projects we see are owner driven.

2) The message on delivering hot air from overhead is still a mixed one. Some are still surprised that if one delivers air more than 15F above room temperature, one must compensate with increased outdoor to remain compliant with 62.1, which is IMC code, and likely UMC code as well. It is certainly the “Acceptable Standard of Care”. Nonetheless, our reps still see lots of VAV box schedules with design discharge temperatures well over 100F. I contend that ASHRAE Standard 55 is unlikely to be met with high discharge temperatures. Some day….

3) Acoustics is still an issue. Many are aware that the ADA Classroom recommendation of 26NC (35dBA) is being proposed for LEED 2012. What they don’t know is that the ADA is considering upgrading that to a requirement, not a recommendation. Unfortunately, not all understand that duct lining will certainly be required, and there are still a few folks who unfortunately think that glass fibers are inherently dangerous, a myth which has been disproven over and over. Glass fiber is still the safest duct lining material available, and restrictions on its use should be removed. There was a noisy diffuser in an engineer’s office, and when I asked how loud they thought it was (I guessed 40NC), at least two in the room whipped out their iPhones and told me it was 50 dBA on their free download Real Time Sound Analyzer apps. (41NC). I was close.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Thursday, April 21, 2011

Balancing Energy Efficiency and Occupant Comfort

I received notice yesterday that our abstract for a talk at Greenbuild, to be held in Toronto this year, has been accepted. The subject will be “Can we have our cake and eat it too? Balancing Energy Efficiency and Occupant Comfort.” If you have been following my blog, you will know that I am concerned that the USGBC is putting global warming and energy use ahead of occupant needs, according to their hierarchy of importance. We will address the possibility that they are not mutually exclusive, as has been implied by some. I suspect that the LEED credit for 30% increase in minimum outside ventilation air will not make the cut for 2012. There is a lot of data, nonetheless, to indicate productivity is enhanced with an increase in ventilation rate. So, we will discuss sustainable designs that will allow for an increase in ventilation when there is no energy penalty, but it will likely not be in place all the time.

We will start with my article from December's ASHRAE Journal (a copy is available on the Krueger website ( and expand on that. The new Krueger DOAS fan terminal, ( along with today’s abundance of control options, allows for a very flexible response to weather and building loads. I envision a set of operating strategies, all of which are simple control variations.

1) At design load, the rooftop DOAS unit will deliver the minimum quantity of outside air in accordance with ASHRAE 62.1, in as efficient a manner as the rooftop make-up air unit can achieve. The zone DOAS Series terminal will meter the 62.1 minimum quantity of conditioned outside air to the space. The inlet temperature from the make-up air unit will likely be a function of both the local design day climate and the system employed. Additional zone cooling demand will be handled by the sensible cooling coil on the zone unit.

2) At conditions other than design, which are likely to be most of the time, the rooftop make-up air unit can flex to run in reduced compressor output (assuming a variable capacity digital scroll) economizer, direct evap, indirect evap, of a mix of all the above, again depending on the design of the unit. The zone unit, which has a pressure independent VAV inlet controller and an ECM fan motor, can do whatever is necessary to maintain conditions in the space. This includes increasing the quantity of ventilation whenever practical (when there is little energy penalty), which will have a payback on the occupant productivity side. Again, the sensible zone cooling coil will modulate to maintain comfort conditions in the space.

The really good news is that most of the hardware is presently available to provide an optimum balance between energy and ventilation rates. All that is needed is a set of operational sequences in the zone and roof control units.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Friday, April 8, 2011

Ventilation Wars

The battle continues on the value of ventilation. During the most recent USGBC conference call (establishing the IE Credits for 2012), we were again confronted with push back from the energy guys. The USGBC has received several responses to the point which can be earned for increasing ventilation 30% beyond the 62.1 minimum. One comment stated “continuing this credit is proof that the USGBC isn’t serious about saving energy”. Apparently this wasn’t the only one of this type.

So we challenged the crew to show evidence of correlations between ventilation and occupant satisfaction and we now have a handful of papers all showing the relationship between ventilation and illness. The correlation is there, but the magnitude is difficult to quantify, and while illness is certainly one measure of productivity, we are looking for more data on occupant satisfaction. Since salary in a commercial building is estimated to be at east $200/sf, and energy about $2/sf, it doesn’t take much of a correlation to prove payback.

One of the challenges is the misconception that economizer mode, which is essentially 100% outside air, is likely not correlated. This is because building operators often “push the envelope” to extend economizer operation as far as possible, often at the expense of occupant comfort, in the attempt to save energy.

Increasing the amount of fresh air while maintaining comfort conditions (meaning with the air being conditioned), seems to have sufficient benefits to warrant a LEED point, but there is still a need for data better linking non-illness related factors. Stay tuned….

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, March 30, 2011

LEED Calculations

We on the IE TAG of the USGBC, and members of ASHRAE SSPC 55 (Comfort) were recently tasked to assist some well meaning engineers in gaining the LEED 2009 point for designing for occupant comfort. As it turns out, there is a checklist now that requires the designer to predict/design the operative temperature, humidity, and air-speed in every type of space of their design. The question was asked, “Do we need to do calculations, or just a narrative?” A similar question has been asked about the proposed acoustical credits for New Construction posed in the draft of LEED 2012, which was out for public review in January.

While it would seem that there may be a future here for English Majors, especially those who specialized in creative writing, there are, in fact, many available tools to the engineer to do the necessary calculations.

The ASHRAE Comfort tool, which may be purchased from the ASHRAE bookstore, or even the Comfort Program available in the Krueger website,, can provide the conditions which will meet the criteria, based on assumed metabolic rates and clothing.

Space conditions can be easily predicted using a number of load calculation tools. Radiant asymmetry is typically the most difficult to predict and very time consuming, but it is seldom an issue, unless one is using radiant panels, then many manufacturers have calculation programs available. Vertical temperature stratification will never be an issue with overhead air supply if one uses ADPI (maintaining a level >80%) to space and select air outlets. The Krueger K-Select program, has a robust ADPI calculation program that is able to graph ADPI as a function of air supply rate, which can be used (by the aforementioned English Major) to prove compliance to that part of the standard.

Acoustics for HVAC components is easily verified using the ASHRAE 885 Acoustical Application standard. The spreadsheet calculating those parameters is also available on the Krueger site (

Validating LEED requirements is likely a bit time consuming, but the resources are available to perform the necessary calculations to prove compliance.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, March 23, 2011

Energy Savings vs. Productivity

I am on the Indoor Environmental TAG of the USGBC. We are working diligently to put together LEED 2012 and put the first draft out for public review in January. We discuss and debate Indoor Environmental issues in a weekly phone conference.

Included were a number of points for acoustics ventilation and daylighting. Some were proposed to be mandatory requirements, including the 40dBA requirement for schools. There was little pushback on many of these proposals, and we were feeling pretty good.

In the call yesterday, however, we learned that in the end, there will be a finite number of points, and weighting has been assigned to each of the proposed requirements. Sadly, while energy saving credits got a high priority, occupant issues, including comfort, ventilation, acoustics, and daylighting issues all got low scores.

The energy to run a commercial building costs a very rough average of $2/sq.ft./yr. Salaries typically run about $200/sq.ft./yr. Assuming we can achieve the desired 30% reduction in energy being mandated by the Federal Government, and both the USGBC and ASHRAE, that means we should expect to save $0.60 / sq.ft./yr. When compared to the $200/sq.ft./yr, it is easy to see that it wouldn’t take much of a drop in productivity due to reduced comfort, poor acoustics, or lousy lighting to wipe out any savings in energy.

It's also been shown that occupants will modify their environment to remain comfortable, using personal fans and heaters, which are incredibly inefficient. The old adage “follow the money” is apparently lost in the energy community. Let's hope that eventually, occupants of buildings will be found to be more important than a slight reduction in energy.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, March 21, 2011

Schools - Spending & Standards

I just completed a drive to South Florida from Dallas. I listened to public radio much of the way, and it was interesting that all 5 states I drove through had the same story. It seems that state revenues are down, and all are planning draconian measures to reduce spending on education. I see the same on national news, but you have to spend a little time in each state to get the local ‘flavor’ of the news reports.

In the past, when commercial construction was down, the state school construction budget always seemed to survive, and keep the local Architect / Engineer/ Contractor pipeline filled with projects. Not so any more, at least in Texas, Louisiana, Mississippi, Alabama, and Florida. I even heard that some schools are doing a rehab and (shudder) repainting diffusers rather than replacing them. That should, of course, be illegal (I jest).

On the other hand, school construction rules are tightening up, big time. Acoustics, often not well understood or simply ignored, is not going to be able to be ignored in the future. LEED for Schools, 2012, recently out for public review, proposes a mandatory 40 dBA limit in schools (about an NC=31), with strict rules for sound transmission through structure (STC) and clearly limiting reverberation time in the classroom. In reviewing the returned comments on this proposed mandatory requirement, there were no comments suggesting it was too strict. Indeed, a point can be gained for achieving 35 dBA (NC=26) in classrooms.

Meeting these requirements will be difficult. Traditional HVAC solutions including unit vents, small package rooftops, water source heat pump, ducted fan coils and even series fan powered VAV boxes cannot likely meet these new acoustical requirements. Florida is still paranoid about lined duct, which will be required if the sound levels are to be achieved. Displacement diffusers are certainly a valid solution, with the advantage of a reduced ventilation air requirement, but are often more expensive than conventional overhead air delivery.

The additional costs of complying with the new acoustical requirements may even preclude retrofits, as many codes require all retrofits to comply with new rules. It will be our children, of course, who will suffer in noisy and often over crowded classrooms.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, March 9, 2011

Those Who Forget the Past

A few years back, I wrote an essay for the ASHRAE Journal titled “Those Who Forget the Past” (, the punch line being “are doomed to repeat it”. Today, in responding to several technical inquiries and during my weekly conference call with the USGBC, I was reminded of that article. While it is said that wisdom comes with old age, it seems that along with it comes the realization that younger generations apparently have to go through the same painful learning experiences that us older folks did.

It is easy to say “I told you so”. Unfortunately, it gets real old, real fast. I wrote a couple of weeks ago about my dismay that some new energy design guides apparently ignore both comfort and acoustical guidelines and standards. We went through the learning experience after the unfortunate EBTR (Emergency Building Temperature Requirements) rules. These often resulted in occupants taking matters into their own hands, employing fans and heaters to remain comfortable (and productive) environments, resulting in an actual measured energy increase.

Today, I was reminded that those lessons are lost on today’s younger designers. We had a lengthy discussion of the subject of openable windows. While a potential energy saving strategy (zero energy use), one has to shut off the AC to that space to be effective as an energy strategy. The person advocating for giving a credit for having openable windows stated that an interlock with the HVAC was not necessary, as occupants surely would not leave the AC on with the window open. This person had apparently never ridden in a convertible with either the heater or AC on to maintain comfort.

In fact, data in buildings with an interlock have found that after the first few weeks, occupants would no longer open the windows, as it was much more comfortable, quiet, and less drafty with the windows closed. The discussion will continue, but the conclusion is obvious to those willing to look at the available data. Openable windows are more of a gimmick than an energy solution.

I also spent some time giving advice on overhead heating strategies, also covered in an ASHRAE Journal article, which is available on our site ( The engineer I was speaking to thought it was more of an art than a science. In fact, of course, there is plenty of science available to help with the design.

We are beginning to record our engineering webinars so that folks can download or stream them on demand. The first of these is available here :

Those of us who have been there need to be able to pass our experiences along to those entering this industry so that we don’t repeat our mistakes.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, February 14, 2011

Existing Buildings Guide

I recently received an e-mail from the chair of TC 2.1 (Thermal Comfort), advising us of a review on an energy Efficiency guide, prepared by a collaboration of The American Institute of Architects (AIA), the Illuminating Engineering Society of North America (IES), the U.S. Green Building Council (USGBC), and the U.S. Department of Energy (DOE). It came with this announcement:

Attached, please find information from the EEG-EB-TG Project Monitoring Committee regarding the Peer Review for the 60% Draft of the Energy Efficiency Guide for Existing Commercial Buildings: Technical Implementation.

The information includes the review input form and instructions along with a copy of the 60% Draft document. The document can also be downloaded from the AEDG web page on the ASHRAE web site ( starting Monday, February 14, 2011. The peer review period will be from Friday, February 11, 2011 through Friday, February 25, 2011.

After a quick glance through this guide, this version has yet to make any reference(s) to human comfort and/or Standard 55 (Thermal Comfort). While the guide is geared towards making an existing building more energy efficient, some proposed changes are likely to impact human comfort by incomplete and yet-to-be-developed recommendations under the “Proper (Reduce) Ventilation”, “Air systems distributions”, and “Lighting” sections on pages 41, 46, and 52, respectively.

There is a real potential for the occupant to suffer in the name of energy savings. As I point out in my recent ASHRAE Journal article (December), the cost of occupant salary is on the order of two magnitudes greater than the cost of energy in a building. The savings that can result in measurable energy reduction may be three orders of magnitude less than occupant salaries.

Those of us that remember the EBTR of 1979 (I was chair of 2.1 then) remember that actual energy savings from that ill conceived plan actually resulted in an increase in energy. The report from the DOE that discovered this fact has been successfully buried and was never published.

Non-validated energy model calculations can likely prove whatever the researcher wants to prove, especially where part load calculations come into play. It is distressing to learn that there are no references to comfort in the document. In the quest for Net Zero buildings (a term which I understand is being changed, much like “global warming” is now “global climate change”) we are likely to wind up with Net Zero Acceptability.

I strongly suggest that readers who are interested in good air distribution design, occupant comfort, and productivity take the time to read and review these proposed guides. Please note the review period.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, February 9, 2011

ASHRAE Winter Meeting Update

Another Winter ASHRAE meeting is behind us. I never made it to the show, as I was fully involved in technical meetings the whole time. Some actions that were taken on the committees I am involved in:

ASHRAE 62.1: Proposed changes will strengthen the requirement that ventilation must be added to VRV and fan coil units in apartments, multiple room dormitories, and multi room hotel spaces. It seems that ventilating a hotel room by sucking air from the corridor under the door by using the toilet exhaust isn’t all that effective.

VAV systems will be required to modulate the outdoor air damper to maintain the minimum ventilation rate at all times. It seems likely that measuring outdoor air quantity will be required in 62.1, as it is already required in 189.1. This should resolve issues some have had with VAV systems that they don’t provide proper ventilation at part load.

ASHRAE Standard 55 (Comfort): We are moving towards a form of mandatory language and better understanding of what is required for compliance. So far, the mandatory language will only be for design, not for current conditions. Mandating clothing and metabolic rate is of course, problematic.

TC 2.6 (Sound and Vibration) - Duct insertion loss being reevaluated for lengths longer than 10ft, in a research project at UNLV, which some of us toured on Tuesday morning. They have a very impressive facility, and are completing a study on inlet effects on diffuser performance.

TC 5.3 (Air Distribution) – Several Handbook chapters are being updated. If you haven’t looked at the ASHRAE Handbook chapters on Air Distribution in the past few years, now would be a good time. Lots of new stuff has been posted there.

TRG7 (Underfloor Design Guide Rewrite Task Group) – We have about 90% of first drafts in hand. Section ‘captains’ will be working towards closure on these drafts over the next few weeks. It is hoped we can have a final draft at the Montreal meeting in June.

As usual, the ASHRAE technical meetings could just as easily be held in a basement in Dubuque, as I seem to spend a lot of time locked in windowless rooms. Las Vegas was a fun place in the evenings, of course. The 6AM breakfast meeting was a challenge on Sunday, though.

It was great to see all the Krueger Reps at the Ghostbar on Sunday night!

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, February 7, 2011

An Engineering Showcase

I was visiting an Engineer’s office in Scottsdale to do a lunch and learn. They had just moved into a new space, designed by them. So new, in fact, that one of the conference rooms had yet to have the table installed. But what impressed me was the use of innovative technologies in the air distribution. Cases in point:

1) Conference room 1 utilized a set of variable flow linear grilles discharging against the inside (glass) wall, with returns located above the windows. This would “roll the room” and in fact, could be considered displacement ventilation, as the air enters the occupied zone at the floor, horizontally (the occupied zone is defined as starting 2ft from any wall).

2) Conference room 2 utilized 4 displacement diffusers located on the interior wall (not glass!) between the doors at each end of the room, for cooling, and floor grilles at the perimeter for heating. Again, the returns were above the window.

3) Closed offices, each with a glass wall and sliding glass door, surrounded three sides of the open office which had 4ft sound dividers and a 20 foot high open ceiling. Closed offices had a plaque diffuser in each.

4) There was no ductwork above the open cubicles. The open office area was conditioned by drum louvers located on the wall above the closed offices on three sides, with West facing glass on the 4th side. The drum louvers were adjusted to spread the air across and over the low partitioned offices. The drum louvers nearest the window wall conditioned that space from either side.

All too often I find Engineers’ offices have lousy air distribution systems. This was an exception to the rule, and should provide a showcase for different technologies for their prospective customers.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Tuesday, January 25, 2011

Visiting California

I spent a couple weeks in Northern California, San Diego and Los Angeles, calling on Mechanical Engineers with our sales reps. And after hitting 20 different engineering firms, and over 140 practicing mechanical engineers in S California, Sacramento and the S.F. Bay area, while I expected to get a lot of feedback on the new technologies being advanced across the US, with some expectation that California would be leading the way in innovation, that wasn’t the case.

What I found was a healthy respect for jumping into new technology without knowing all the ramifications of that jump. Many engineers either had or knew of bad experiences with new technologies and had already faced the issue of complex building systems’ inability to be properly installed or maintained.

On the whole, the concerns were less about the technology than about the ability of the technology being installed properly in the buildings they were designing. The more complex the system, it seems that there is a higher likelihood that something critical would be overlooked.

California, much like the rest of the country, has experienced a high flux in opportunities for mechanical engineers, and lots of shuffling of personnel is apparent. Everyone seems to have worked somewhere else recently. The result is a lot of cross pollination of ideas and experiences. And there is a bit of conservatism in designs. Having heard horror stories on every type of system imaginable, it is no surprise.

Apparently tried and trued HVAC designs (VAV, overhead well mixed air delivery) either has a greater safety factor or is simply the most familiar system, but seems to be less troublesome in commissioning and operation. It is certainly the more familiar installation.

While other system approaches have the potential, at least, to be more energy efficient, and can be less expensive to install, often it is not the case. I suspect what we are seeing is a lack of coordination between the Owner, General Contractor, and installing trades. All need to be on the same page, especially with complex technologies.

There was also a surprising (at least to me, in California of all places) push back on the advantages and general endorsement of LEED. Many see LEED as a time consuming endeavor for which they don’t get paid. Worse, I discovered that the LEED required (per ASHRAE 62.1, which is a prerequisite) Charcoal Ozone mitigation filters are never specified in LA County, which is clearly an Ozone “non-attainment” area under the EPA rules. Nonetheless, a number of buildings in LA are LEED certified without these items. One has to wonder what else that is LEED mandatory is overlooked.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Tuesday, January 4, 2011

Dan Int-Hout's Top 10 Predictions for 2011

1. LEED 2012 will be approved, pretty much as it is in its first public review (

2. The ASA Classroom acoustics recommendation (essentially NC=26, ANSI 12.60 ) will become a requirement in many local codes and may be a part of the next IBC. It will also be a requirement of the ADA governing bodies, forcing a redesign of many school HVAC systems.

3. Over my objections, the ASHRAE Thermal Comfort Standard (55-2010) will be rewritten into code language. I predict this will result in gross misuse and misinterpretation of the requirements and will make lots of money for trial lawyers. (I hope I’m wrong on this one.)

4. With any luck, we will get a rewritten ASHRAE UFAD Design Guide out of committee at the summer meeting. The current manual has been pulled from the ASHRAE bookstore following complaints, most noticeably from the GSA, over lack of discussion of the potential negative issues with this design concept.

5. Displacement Ventilation will see significant use in classrooms (it’s quiet, see item #2 above).

6. Chilled Beams will continue to be the “darling” of innovative engineers. We will not see validation of the calculated energy savings from this relatively new technology. That will not, however, prevent estimates of significant energy savings, resulting in LEED points.

7. For the umpteenth year in a row, BOMA will state that the number 1 reason for not renewing the lease in high rise buildings is “occupant dissatisfaction with the building environment” (ie: comfort). See item #3 above.

8. The market for HVAC components will continue to be relatively flat with local ups and downs.

9. VAV overhead air distribution will continue to be (by far) the most used system in new buildings.

10. The Cowboys will continue to disappoint their fans.

Authored by: Dan Int-Hout, Chief Engineer Krueger