Monday, July 25, 2016

NW Code Requirements

The State of Washington has issued a new building code that affects, among other spaces, office buildings. The code is very specific about ventilation and building energy use in that it mandates “the use of decentralized ventilation systems using dedicated outdoor air systems (DOAS) to deliver 100 percent outside air independent of heating and cooling systems”.

What this means is that DOAS systems are mandated and that conventional VAV systems, which mix ventilation and return air at an air handler, are essentially prohibited. While there is an exemption for “High Performance VAV systems”, which I have described in an ASHRAE Journal article and in earlier blogs, it tends to favor those that are disconnected from the ventilation supply, such as VRV and chilled beams.

What is particularly interesting is the requirement that states “ECM motors that vary with load are required for all fan powered VAV terminal units”. This, of course, is what I have been advocating for some time – variable volume series fan box control. When employed with 100% outside air through the VAV inlet (and a sensible cooling coil on the induction port), all the requirements of the new Washington code are met. I’m willing to bet that this will not be the only such code requirement that we’ll see in the future.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Tuesday, July 12, 2016

ADPI and Standard 55

I have been campaigning for 40 years to get a correlation between ASHRAE Standard 55 and the concept of ADPI. I chaired Standard 70, (Method of Test, Air Diffusers), Standard 113 (Method of Test, Room Air Distribution, including ADPI) and Standard 55 itself. I also chaired TC 2.1, Thermal Comfort and TC 5.3, Space Air Distribution. I Chaired TC 4.10, Calculation of room air motion (CFD), when it moved from a TG to a TC.

In prior blog posts, I have described the issues with the 40 fpm limit on using the graphical method of Standard 55 to show compliance and wrote an ASHRAE Journal article on how to manage the process. After several false starts, ASHRAE finally approved the creation of a user’s manual for Standard 55. While I was listed as a reviewer during its creation, I was either on the Technical Activities Committee or Standards Activities Committee and felt some conflict of either jurisdiction or time. I have been on ASHRAE’s board for the past two years and have attempted to remain neutral. The process of creating a user’s manual was not without conflicts of opinions.

The document, nonetheless, has been approved for publication. I couldn’t be more pleased with the result. I have attached a tiny piece of the user's manual:

Example 1: Using ADPI for overhead air distribution systems, the diffuser manufacturers often rate their products based on the Air Diffuser Performance Index (ADPI). ADPI is defined by ASHRAE Standard 113 as the percentage of points measured in a room that are within both the ASHRAE temperature and velocity ranges for comfort. ADPI is based on the acceptance and recognition that it is not possible to achieve a comfort level of 100 percent, but 80 percent acceptance is achievable and measurable. Using the example space identified in Figure 3-B, in cooling mode the designer needs to provide 79.6 W/m2 (25.2 Btu/h-sf) of sensible cooling.

As seen in Figure 3-E, the diffuser type is ceiling-mounted with 4-way throw and the return is at the ceiling. Characteristic length of the diffuser is 1.07m (3’-6”) to the wall, 2.23m (7’-4”) to midpoint between diffusers. From Table 4 Chapter 57, ASHRAE Handbook – HVAC Applications, 2011, the closest room load is 63 W/ m2 (20 Btu/h-ft22), with a maximum achievable ADPI of 93, a T50/L of 0.8 for maximum ADPI, and a range of T50/L of 0.7 to 1.3 to achieve an ADPI greater than 90. The designer has selected a diffuser with an isothermal throw of 1.2m (4-ft) to 0.25 m/s (50 fpm). X50/L for this selection is 1.12, which is within the range needed to have ADPI > 80, therefore ADPI requirements are met. Based on ADPI > 80, the designer can conclude that the average airspeed is less than 0.35 m/s (70 fpm) for greater than 80% of the space. The designer can also conclude from the ADPI calculations that the temperature stratification is less than 2.8 °C (5 °F) for locations between ankle and head level (1.8m (6-ft) above floor level) and at least 0.6m (2-ft) away from the exterior wall. In many cases, achieving ADPI of this value will also meet the requirement to not exceed 0.2 m/s (40 fpm) and even 0.15 m/s (30 fpm) if the operative temperature (to) is below 22.5°C (72.5°F). ADPI does not predict air speeds in heating mode, but if the overhead air system is the only potential source of elevated air speed (window drafts have been accounted for with perimeter baseboard heating systems), then it is also likely that the air speed criteria will not be exceeded in heating as the terminal box has been tuned to minimum vent rate in heating mode. See Section 5.5 for more discussion of this point.

The above is what I have been campaigning for as long as I have been in ASHRAE (since 1974). I was asked if referencing the user’s manual was the same as referencing the Standard itself. It would appear that it could. So at last, we have a path to use performance data in our catalog and design documents to be able to claim compliance to major portions of Standard 55.

Authored by: Dan Int-Hout, Chief Engineer Krueger


Wednesday, November 4, 2015

CO2 is a problem?

I recently received a link to a new paper on the effect of elevated levels of CO2 on the cognitive ability of building occupants. This explains why student test scores are reported to be higher as ventilation rates increase. While LEED gives a point for increasing ventilation 30% above the 62.1 minimums, the implication here is that the ventilation rate needs to be quite a bit higher than that.

http://thinkprogress.org/climate/2015/10/26/3714853/carbon-dioxide-impair-brain/?utm_source=newsletter&utm_medium=email&utm_campaign=tptop3&utm_term=5&utm_content=5

Currently, outdoor CO2 levels are approaching 400ppm. The report states that while no ‘critical’ level is defined for indoor spaces, the 62.1 DCV (Demand Controlled Ventilation) suggests that it be “700 ppm above outside”, or no more than 1100 ppm total, which is quite a bit higher than what is found to be “safe”. They seem to believe that 600ppm is a good target.

Achieving this will require an efficient means of introducing outside air into a building.

One option is to simply increase the outdoor air setting of the air handler, but most units are designed to handle only about 30% of the unit’s air flow capacity for the climate in which it is installed, so this may not provide enough ventilation. Another option is to increase the percentage of outside air, but that would likely generate limitations with regard to dehumidification capacity and temperature. I believe the most effective method of introducing ventilation is to vary the quantity of ventilation air to the spaces that need it, which would imply the use of a Dedicated Outdoor Air System, or DOAS.

For this concept to work properly, the DOAS unit would likely need to be at a little larger than typical. It would also require an effective delivery system. For it to be energy efficient, it must only deliver as much outside air to each space as is required, which would involve a measured and controlled air flow damper at each zone. The VAV DOAS unit would then supply dry, cool ventilation. Doing this however comes with the risk of sub cooling spaces if the dehumidified ventilation air is not reheated (resulting from minimum ventilation rates that exceed the load). 

I’m sure there are other possible means of accomplishing this, but it’s likely that they would not be quite as cost effective as the DOAS solution. 

At Krueger, we call our DOAS unit a “Chilled Box”, which is an ECM variable speed, series flow, fan-powered terminal unit with a sensible cooling coil on the induction inlet. I encourage you to read my recent ASHRAE Journal article on this topic, as it not only provides a solution to address this CO2 issue, but it can also satisfy a number of other ventilation challenges you may come across.

Friday, October 2, 2015

Underfloor Products

With installations taking place in millions of square feet of office space, underfloor air distribution (UFAD) is seemingly gaining in popularity, at least when compared to where it was just a few years ago. In fact, Krueger just recently released their new and improved line of UFAD products that include interior, perimeter, partially stratified, and true displacement ventilation solutions.

As chair of the Technical Committee for the rewriting of ASHRAE’s UFAD design guide, I became much more familiar with the details surrounding underfloor air distribution, both good and bad.

- It provides a truly flexible solution and is great for high-churn applications.

- It allows users to be in more control of their comfort by way of controlling the flow of air in their immediate space.

- It requires careful coordination with all the construction trades to avoid the loss of conditioned air into unwanted spaces (leakage).

- Designs must take into account the perimeter to properly handle solar loads. (This can be said for any form of air distribution!)

- There must be controls in place to maintain humidity control. Should moisture issues arise, they may not be apparent until it has caused a more severe problem.

Luckily though, with proper planning and when you can find the right partners and product mix, all these details can be addressed to ensure a successful UFAD system. (Of course, with the products come the expertise and guidance from the supplier - like Krueger, who has installed many successful UFAD projects.) So, if you haven’t already, take another look at UFAD, it’s a proven technology that can offer many benefits to building owners and occupants.

Learn about Krueger’s new line of underfloor products.
https://www.krueger-hvac.com/Catalog%20Home/Underfloor

Friday, February 6, 2015

Top Ten HVAC Predictions Scores for 2014

Now that a certain event has past (weekend before last) I can finally score myself on my predictions for last year.

1. LEED V4, released last fall, includes a reference to either AHRI 885 or the ASHRAE Handbooks to prove compliance to acoustical requirements. The handbooks are missing a critical path table for the sound transmitted from a plenum noise source into a space. The incoming chair of TC 2.1 has indicated he will get the missing ceiling table included in the Handbooks. I predict he will fail in this effort for at least three years and that the 885 handbooks will be the only easy path to compliance. (One can hire an acoustician, of course, and TC 2.6 is populated with them). Yup. Nothing happening - 10 points.

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. If adjusted after balancing, rebalancing is required. It is the design engineer’s responsibility to provide the adjustment information. The installing contractor should be designated as the one responsible for setting the pattern deflectors. I saw close to 1000 Engineers last year. Only a couple admitted it was their responsibility to specify who was to adjust them and to provide instructions. The NEBB says in their basic instructions it is their responsibility. No balancer I spoke to knew this or did it - 10 points .

3. ASHRAE Thermal Comfort Standard (55-2013) has been modified to include Normative (mandatory) and Informative sections so that it can be referenced directly in codes. ADPI will be included by reference to the ASHRAE Handbooks, which will be updated to show the relationship between air distribution and thermal comfort. Well, this didn’t happen. The ball got dropped somewhere. My bad - 0 points.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems, to get LEED or Energy Star ratings. Yup. No data - 10 points.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will begin to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program. Underway. An excellent paper will be presented in June - 10 points.

6. The number 1 reason for not renewing the lease in high rise buildings will continue to be “occupant dissatisfaction with the building environment” (ie: comfort). It has been so for the past 20 years and is frankly a ‘gimmee’. One can hope that I miss this one. The BOMA public relations person now refuses to answer this question. I guess they are a bit embarrassed by the data. I’ll give myself 5 points.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back. Slowly but surely it is - 10 points.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load. ASHRAE RP 1515 will open a lot of eyes. The report from the ASHRAE MTG on Advanced Air Distribution will be circulated showing paths to optimize system design. The MTG says it has completed its work and has been dissolved. About 20% of the engineers I spoke to have lowered their interior design from 1.0 to 0.65cfm/sf. - 8 points

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of Engineers will finally get it. (ps: Hot air rises!) I still get push back on this issue, but some are getting it. It’s getting better, but we’re still not there yet - 8 points.

10. Sadly, I predict that the Cowboys will continue to wallow in the mud of disappointment. Ok. I blew this one. Of course, the Cowboys blew the last one! But, I’m still giving myself 0 points.

So I get 71 out 100. That’s just a barely passing grade… but seems familiar some how. I’ll try to do better this year.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, January 28, 2015

Top Ten HVAC Predictions for 2015

It’s time for my long awaited top 10 predictions for 2015. I am becoming a bit pessimistic in my predictions. If I get a high score next January, it will mean the industry has failed its customers - building occupants.

1. LEED V4 will get less and less buy-in. Since there is no enforcement or post construction check, the LEED rating has no teeth --- but it gets “feel good” points from the “greens”. None from me though.

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. Sadly, this is likely a gimmee. When asked, neither balancers, contractors, or design engineers take any responsibility for assuring this gets done. Building occupants will suffer, but everyone else gets paid.

3. The Variable Volume Series Fan Powered Box will be recognized as a really effective way to design an energy efficient HVAC system.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems to get LEED or Energy Star ratings. This is likely another gimmee, but I can hope.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will start to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program. This is one I hope I win.

6. The number 1 complaint I hear is that offices get cold in the afternoon. No kidding. Design loads are overestimated by likely a factor of five. I predict this will not change in 2015… Another one I wish to lose.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load.

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of engineers will finally get it.

10. The Cowboys will prove to be unpredictable. After last season, one has hope, but I wouldn’t bet any money. I predict a 9-7 season.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, September 3, 2014

Engineers Push Back

I recently received a nice letter from an engineer in California who said she had heard me speak a few years ago about overhead heating and had been following my advice (and that in 62.1 and the Handbook) about limiting discharge delta-t to 15oF. She then went on to say how surprised she has been at the push back from engineers on this recommendation. Sadly, I had to tell her that my experience has been similar.

In my role as an ASHRAE Distinguished Lecturer and in making engineering sales calls with Krueger Reps, I see an average of 1000 engineers a year. I almost always manage to bring this topic up in conversations or lectures and nearly every time, there’s an engineer that tells me, “I’ve been doing this for XX years and no one has complained”.

Apparently, the concept of hot air rising (and cold air falling) isn’t a universally accepted paradigm when it comes to air distribution. This person (California engineer) mentioned that there is disbelief in my stated rule on heating a room, where “the hotter the air delivered at the ceiling, the longer it takes to heat a room.” Sorry folks, but it’s true - overly hot air dispensed at the ceiling will most certainly want to stick to it. The hotter it is, the longer it will stay stratified, which means the longer it will take to cool enough to blend with the air below in the occupant space.

Every forced air project with a heating coil likely has an equipment schedule. Somewhere on that schedule is a column headed ‘Leaving Air Temperature’. If any values in that column are 15°F greater than the designed zone temperature (usually between 73°F and 75°F), the code official has the right to ask how the engineer intends to comply with the Standard 62.1 requirement for increased ventilation air and if that requirement was included in the building load calculations. If you recall, ASHRAE Standard 62.1 requires an additional 20% outside air if heating from the ceiling with a ceiling return, as is the case in most commercial buildings. The 62.1 Ventilation Rate Procedure has been adopted by many, if not most building codes.

It’s also worth noting that any space with a discharge to room differential exceeding 15°F will not comply with the vertical stratification limitation of ASHRAE Standard 55, which is often included in many codes, if not a minimum in building design assumptions. Still, engineers are pushing back. It’s no wonder the level of discomfort in commercial spaces is as high as it is. But as they say, “who’s checking?”

Do you work in a stuffy building? Are you using a space heater year round? Tweet us @KruegerHVAC and share your comments with the HVAC engineering community. Let them know that regardless of #whoschecking, proper air distribution matters.

Authored by: Dan Int-Hout, Chief Engineer Krueger