A/C Question

[misirlou]

I have a 3 year old house built by Perry Homes. We have always had issues with high temperature gradients across the house. I have long suspected poor design in the installation or possibly insulation. An A/C coil recently went out (manufacturer design issue), and the A/C technician indicated that our distribution plenum is poorly designed. Looking at it, it seemed small, but this is the first air plenum I could easily see.

I would like to understand whether the building codes address HVAC quality and efficiency. I know that the government has requirements for compressor efficiency (i.e. SEER rating), but what about overall HVAC system efficiency?

I'm assuming that no regulations cover this, and I will not get reimbursed even if regulations do cover it. However, I'm mad enough to at least write a few angry letters. For all the talk about energy efficiency, this is an example of where a relatively simple regulation change that causes a small increase in HVAC installation cost can make a big difference in efficiency.

BTW, the other issue is that I of course have the cheap builder special HVAC unit, hence the coil going bad in 3 years.

 

[brntorng]

You can get an independent HVAC engineer to run a heat load analysis of your system. This will tell you whether it's properly designed or not and, if not, what the problem is before you go spending a lot of money to fix it. It's not that expensive to do and could save a lot of money while making your home more comfortable once the issues are resolved. Message me if you need a referral in Austin.

 

[accuratehorn]

Do you mean a proper Manual J calculation for the home? If so, this is what is needed to calculate the proper size of the compressor, and the size of the plenum and duct lengths/sizes should be part of the calculation, too.
The amount of "glazing," size and placement of windows, amount and type of insulation, and several other factors should be fed into this calculation.
Also, you can have the ducts tested for leakage and flow somehow, and the whole house can be tested for leakage, which checks for leaky weatherstripping and window losses.
Maybe you have too many windows facing west, which need to be shaded with an overhang-there's lots of things that could be wrong.

 

[brntorng]

Yes, a Manual J calculation. Couldn't remember the name, but that's what needs to be done first. Investing in anything else first is probably a waste of money.