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Average quality built homes needing makeup air because they are airtight

Brian Ducharme | Posted in Energy Efficiency and Durability on

I have a question in regards to homes being built (not necessarily green homes) that are subject to the new energy code with air sealing and blower door tests. These homes are being built with average, code minimum building materials and after a blower door test it is showing the house is tight enough to require make up air.

Seeing as these are not green homes, there was no plan in place ahead of time for a system to bring fresh air into the house. Are you seeing this as a problem in other states as well?

I am in CT and a friend of mine building a house just dealt with this issue with his local building official.

What is the option for bringing in fresh air when you learn you need it at the end of your build? As I am looking to build in the near future I assume I will be running into this as well. In the example of my friend’s house, it is constructed with 2×6 walls, 1/2″ zip system sheathing, roxul batts in the walls. It is a cape style home.

Thank you,

Brian D.

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  1. NormanWB | | #1

    Look at AirCycler. It integrates with your existing HVAC and bath fans.

  2. GBA Editor
    Martin Holladay | | #2

    The need for a mechanical ventilation system is not limited to green homes. According to the 2012 International Residential Code, all homes (except hot climate homes in Zones 1 and 2) must include a whole-house ventilation system.

    For more information on this code requirement, see An Overview of the 2012 Energy Code.

    The same code requires that new homes in your climate zone pass a blower door test, with results of 3 ach50 or better.

    As far as I know, it's a code violation to build a new home in Connecticut that doesn't include a mechanical ventilation system. That said, you should verify this information with your local code enforcement authority.

    One more point: Just because a house has a mechanical ventilation system, doesn't mean that the house has adequate makeup air. Most mechanical ventilation systems are not designed to perform as a makeup air system. If a house includes a range hood exhaust fan rated in excess of 400 cfm, a separate makeup air system is required by code. For more information on this requirement, see Makeup Air for Range Hoods.

    For information on all of the different ways to provide mechanical ventilation for a house, see Designing a Good Ventilation System.

  3. Brian Ducharme | | #3

    Thank you for the information. I guess what I find strange about this is that people I know running into this problem after the blower door test were not asked at the design phase to include a whole house ventilation system. Seems like the building officials should be requiring this to be on the blue prints at the permitting stage.

    Norman Bunn, Thanks for the suggestion of Aircycler. I have been researching their products and it seems like a great option if I do in fact go with a traditional heating/cooling forced air system.

    If I decide to heat and cool the house with mini split units, what would be the recommended approach for ventilation?

  4. user-2310254 | | #4

    Zehnder gets a lot of positive mentions, but it is a little pricey.

  5. GBA Editor
    Martin Holladay | | #5

    Q. "If I decide to heat and cool the house with minisplit units, what would be the recommended approach for ventilation?"

    A. All of the various options are listed in the article I linked to ("Designing a Good Ventilation System").

    Your options include (a) an exhaust-only ventilation system, (b) one or more pairs of Lunos fans, or (c) an HRV or ERV.
    Zehnder is a brand of HRV, but there are many other brands to consider.

  6. Expert Member
    Dana Dorsett | | #6

    The tighter the house, the more potentially problematic an exhaust-only approach becomes, since the path of the incoming air may be unknown & not-so clean. As Joe Lstikburek wrote last year:

    "Exhaust-only ventilation leads to depressurization in houses, townhouses and row houses that are constructed to meet the 2015 International Residential Code and significant depressurization in apartment construction constructed to meet the 2015 International Building Code. In single family detached houses this leads to contaminants being pulled from attached garages – especially houses with bedrooms over garages. Contaminants are also pulled from under slabs – if radon was valuable we would mine it this way – and what better way to bring soil gas, herbicides and pesticides into a home?"

    Pairs of Lunos HRVs can work OK in simpler more open floor plans, but for houses with a lot of doored-off rooms a balanced ducted approach may be cheaper.

  7. Brian Ducharme | | #7

    Dana, thank you very much for the response. This is what I was hoping to hear. I'm looking for advice on the best approach seeing there are a lot of options. In the research I have been doing it seems the balanced ducted approach may be the answer for my build. The first floor is relatively open, though upstairs has three bedrooms a bathroom and a large closet. So there are lots of spaces behind doors up there. I originally was hoping to heat the house with a combination of mini split units though I am starting to think it is unrealistic for my build. It is not a high performance home that could get away with one or two minisplit units. I may install a traditional heating system with a mini split on the first floor so I can limit the use of the ducted system down there. Thanks again.

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