Should I install HRV/ERV duct work for future-proofing?
DenmarkDave
| Posted in Mechanicals on
I am in the process of planning a new house to be built in Maine. The builder likes building leaky houses, but after lots of questions and discussion we are agreeing on some targets and construction plans to support the targets. I am not sure that the house will ever get down to passive house standards, but I am thinking that I should at least put the HRV/ERV ductwork in the walls to add mechanical ventilation if needed – we will be doing blower door tests. When is ventilation required? what is the ACH threshold?
thanks
Dave
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Replies
Dave: With good drawings, showing where the air barrier is and details showing how to install it, any competent contractor can get close to, or meet, Passivhaus air tightness. You should aim for that and plan on installing mechanical ventilation. You'll need it.
My contractor (also in Maine) had never been required to worry much about air tightness. But he's a smart guy, understood the concept, instructed his workers to be careful about maintaining the air barrier, and hit .59ach50 with the First blower door test he's ever been involved with. It's not rocket science, it's just attention to detail.
Dave,
Stephen is right. If you are building a new house, it's essential to make the house as tight as you possibly can.
Your new house will need a mechanical ventilation system. Here is a link that describes your options: Designing a Good Ventilation System.
IRC 2015 code MAXIMUM leakage is 3ACH/50, and that is a tightness level that demands mechanical ventilation. I beleve Maine is at IECC/IRC 2012, which makes 3ACH/50 a requirement, even if enforcement is lacking.
http://www.reca-codes.org/codes2012/Maine.pdf
Note, even leaky houses need ventilation, to ensure that the ventilation air and exhaust are provided where it's most needed. Balanced ventilation (including ERV or HRV) is preferred, to ensure clean paths for the entering ventilation air. Exhaust only schemes can provide the necessary air volumes, but if the leaks are bringing a significant fraction from the soil or a garage the quality of that air is highly suspect. See:
https://buildingscience.com/documents/building-science-insights-newsletters/bsi-012-balancing-act-exhaust-only-ventilation-does
Dana: As far as I know, Maine is still using the 2009 IRC and IEEC. You are correct that enforcement may be lacking in some places. And communities with fewer than 4000 residents, like mine, may decide to not enforce any code.
If course anyone spending the money on a new house is well advised to at least meet, if not exceed, the newer codes, enforceable or not.