Good morning.

  I recently had an engineer tell me,  energy efficiency goes out the window,  with large square foot commercial buildings , and with a large capacity of people.  His way of thinking, is you have to exchange air so many times a day, and the HVAC runs 18 of 24 hours a day. Then it doesn't matter if you use 2" or 12" of insulation.  

  My thought is if you use an air tight structure, with an Artic Entry, then the energy efficiency plays a huge part.

   Any one have any thoughts or case studies you can share?  

Alan;

Not entirely true, although I will say that because all commercial buildings are designed for occupancy load and required to introduce fresh make up air into the building. The HVAC system becomes less efficient as it is always battling the exterior air, either hot or cold.
Air or heat exchangers can aid in the equipment efficiency by pre-conditioning before entry to the inside.
These air exchangers are also available for residential use but are not mandatory.
2" or 12" does still matter as a matter of energy savings, but will not make much difference for the ability to downsize equipment like you can do in residential buildings.
You will notice that many air conditioned commercial buildings will feel cool and clammy - this is due to the oversized equipment cooling too quick and not dehumidifying, this also leads to sick building syndrome if not properly supplied with fresh air

Let me re-lierate on this.
This paticular building is a single story 80 to 100, 000 sq.ft. nursing home. In my opinion, there shouldn't be a lot of exterior air coming into this building.
Obviously, air quality is a big concern. Therfore, energy efficiency should come into play.

There are requirements for a certain volume of air exchange on this type of structure - right? So if it's a tight building and you obtain that air exchange through ERVs then I would think the insulation is indeed important for energy efficiencies. But if it's old school construction that gets it's air exchange through leakage and the amount of air exchange is substantial then he's probably right. He's the engineer so he should be able to show you the numbers on this building to defend his position.

Alan;

 

If air quality is a concern then you would want fresh air intruduced into the building. Energy efficiency takes a backseat to Indoor air quality. The cfms of fresh air are dictated by code

For a different take on this subject take a look at http://doas-radiant.psu.edu/. The Penn State prof who has this web site argues that commercial AC systems are 3 to 4 times bigger than they need to be. He advocates using radiant heating/cooling in a building to take care of the bulk of the sensible heating/cooling load, and an AC system that primarily brings in outdoor air and conditions it and exhausts stale air. This takes care of the latent load. The total energy demand is much less, and indoor air quality much higher.

The engineer is right on one count though. You do lose a lot of heat by way of air leaving the building and fresh air taking it's place. That's why the new mantra in building science is, "Build it tight, and ventilate it right." With controlled ventilation you can capture a good bit of the heat in the air leaving the building and put it into the air coming in. Almost too good to be true, swap out the air and keep the heat.

Thanks!

  Dmaceld - had the answer I was looking for. 
"The engineer is right on one count though. You do lose a lot of heat by way of air leaving the building and fresh air taking it's place. That's why the new mantra in building science is, "Build it tight, and ventilate it right." With controlled ventilation you can capture a good bit of the heat in the air leaving the building and put it into the air coming in. Almost too good to be true, swap out the air and keep the heat."

I will do some research on the website given.