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Community and Q&A

Effect of Reduced Infiltration on Heating/Cooling Load

jason_v | Posted in Energy Efficiency and Durability on

Thank you in advance for your time and consideration. This community has been invaluable to me with all the help and advice, it is greatly appreciated.

This question is in reference to a new build in climate zone 7A. Our strategy is to go for upgraded insulation via continuous exterior insulation (1 to 2 inches depending on exterior material) using Zip-R and EEIFs over 2×6 construction with r 2o batts (mineral wool if we can find it) and as much air tightness as we can get via construction techniques and Aerobarrier system. Insulation beyond this is not feasible for our design.

I have been trying to find resources on how much of a difference making a new build much more airtight (shooting for less than 1ACH@50) has on heating and cooling loads.

Right now at 3.5ACH@50 the manual J calculations show a 17K Btu/hr load for heating.  Can i assume that reducing that 3.5 to 1 also reduced that load by a similar factor?

Thank you

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  1. Expert Member
    NICK KEENAN | | #1

    Yes, but ...

    Infiltration heat loss is directly correlated to the infiltration rate. But at 1 ACH50 you will need to have mechanical ventilation. Unless you use a heat recovery ventilator you will lose energy from that.

    1. jason_v | | #2

      Thank you. We are doing balanced HRV with dedicated ducting 70% efficient (or higher) and are considering heating the supply side.

  2. Expert Member
    NICK KEENAN | | #3

    Reduced infiltration also makes for a more comfortable house, especially when it's very cold. It's less drafty and you don't get as many cold spots.

    1. jason_v | | #5

      thank you

  3. Jon_R | | #4

    Reducing the natural infiltration portion of the load (not the entire load) proportionally is about right.

    Note that Zip-R isn't "exterior insulation". Consider better performing plywood with all exterior unfaced EPS. And an interior side air barrier to keep interior moisture out of your cold climate walls/ceiling.

    1. jason_v | | #6

      Thanks for the clarification, I simplified the details in the original post.

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