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 (http://www.krueger-hvac.com/lit/pdf/net_zero_acceptability.pdf) and expand on that. The new Krueger DOAS fan terminal, (http://www.krueger-hvac.com/ecatalog/model.aspx?refid=1569) 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