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Community and Q&A

Single point source heating with ductless minisplits worked for us in Minnesota (Zone 6A)

User avatar
Matthew Vetting | Posted in Energy Efficiency and Durability on

Not really a question

Just wanted to post to the Q/A that we successfully heated our entire house with a single head ductless minisplit. Firstly, in the build we had issues with HVAC people who didnt want to do our single point source heating, until they got sick of our persistence and gave in. Then we had issues with the code inspector who made us put in electric wall heaters in all rooms of the house except where the minisplit head unit was. We stood there with the guy trying to argue our points and case studies, but he just kept coming back to “whats going to happen when someone closes a door….. your pipes are going to freeze”. Round and round until we gave in and put in the wall heaters. Anyhow…. we survived the polar vortex with our Mitsubishi Hyperheat just fine, and only turned it off one night when it got to -30 F and coasted on the residual energy in the slab on grade till it warmed up to -15 F the next day. So everyone get out and advocate for building energy efficient and educating HVAC and building inspectors what is possible.

Also wanted to thank Green Building Advisor, as we relied on this website heavily when we were designing our home.

House Specifics
http://vettingwolfhomestead.com

18,000 BTU Mitsubishi 21 SEER ‘Hyper Heat’ H2i Heat Pump System
2 X Outdoor units MUZ-FH18NAH

2 X Indoor units MSZ-FH18NAH (one for heating one for cooling)

R-35 Double Stud Walls
Open Cell Spray Foam

R-90 Raised Heel Truss Roof
U-0.12-0.15 triple pane windows
ACH50 of 0.62
2/3rds slab on grade, 1/3 basement
HERS score pre-PV of 32

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Replies

  1. User avatar
    Dana Dorsett | | #1

    >"he just kept coming back to “whats going to happen when someone closes a door….. your pipes are going to freeze”. "

    ---

    >"R-35 Double Stud Walls
    Open Cell Spray Foam

    R-90 Raised Heel Truss Roof
    U-0.12-0.15 triple pane windows"

    Does the guy not believe arithmetic? The exterior walls have 10x the R-value of the partition walls, 20x the R value of the door. Even the windows have a slightly higher R-value than the partition walls. Unless it had a huge picture window or an operable window left open there's no way anything in that room is going to freeze! (Well, OK if it gets close to absolute zero outside it's going to freeze...)

  2. User avatar GBA Editor
    Martin Holladay | | #2

    Matt,
    Thanks for your report! Glad to hear the GBA was a useful resource for you. And congratulations on your successful project.

  3. Keith Gustafson | | #3

    Great info.

    Sure would have been tempted to call the building inspector over during the polar vortex

    I mean, he wasn't wrong per the code, but it would be instructive for him to see first hand what a high performance house looks like in diabolically cold weather

  4. User avatar
    Stephen Sheehy | | #4

    We had to change insurance companies because our old company didn't believe heat pumps would work in our Maine winters. Lots of people stuck in the last century. "Houses need to breathe." 😇

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