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