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Community and Q&A

Managing overheating in a 1.5-story home

mfredericks | Posted in General Questions on

I’ve purchased a small 1950’s 1.5 story (or Cape style) house, where the second floor has knee walls and sloped ceilings. We’re in Nova Scotia, Canada which is a cold climate but spring/summers can get hot. We plan to super insulate the house using the PERSIST/REMOTE approach when we can afford to, but in the meantime the house has no mechanical ventilation and minimal insulation. The second floor bedrooms are already getting uncomfortably warm on sunny days. I’m curious what methods can be used to manage the overheating in this type of building. Currently we have a fan blowing fresh air into one of the upstairs rooms, and we’re considering installing two-way window fans.

Are we stuck running fans all summer? should we keep the windows open or closed? Any clever ways to deal with this situation would be appreciated. Thanks for any help!

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  1. GBA Editor
    Martin Holladay | | #1

    The most important step you can take is to reduce air leaks in your home -- a measure that is best performed with the help of a blower door -- and to increase the amount of insulation in your roof assembly. (For more information on insulating sloped roofs, see How to Build an Insulated Cathedral Ceiling.)

    If you can't afford to make these improvements now, you might consider installing a whole-house fan. This approach only works if temperatures drop to comfortable levels at night. For more information on whole-house fans, see Fans in the Attic.

    Finally, a sure-fire solution to overheating -- but one that uses a lot of energy -- is to install an air conditioner.

  2. homedesign | | #2

    In addition to Martin's comments....
    Try to shade your glass from the outside to reduce the radiation BEFORE it goes thru the glass.
    If you can't shade from the outside use curtains on the inside.
    If it is warmer outside than inside ... windows should be closed.
    When it is cooler outside (and assuming it is not-so-humid outside)then open windows upstairs AND downstairs...
    It's important to open windows downstairs in order for the cooler denser outside air to spill into the house down low so it can push the warm air up and out the upstairs window(s).
    If you feel you must use a window fan upstairs...orient the fan to blow OUT not in.

    (a fan or ceiling fan that blows air directly on the occupants can add comfort)

  3. GBA Editor
    Martin Holladay | | #3

    Good suggestions.

  4. mfredericks | | #4

    Thanks Martin and John! I've been thinking of switching the fan around to exhaust the hot air from the upstairs to pull cooler air from below - thanks for confirming this. We'll also try closing the windows at strategic times. Other have also suggested it, but I'm not interested in installing an AC unit.

    We've participated in a couple efficiency programs and have reduced the home's air leakage from 10 ach @50 pa when we bought the house, to around 7 ach when it was last tested in November. It's still a very leaky house and the air tightness improvements were all made in the basement/crawl space because they were easily accessible. Our hope is to continue with air sealing and insulation using the advice we've gained from GBA, but for now we need to make due.

    Thanks again

  5. Expert Member
    Dana Dorsett | | #5

    Window gains usually dominate the cooling load, but with barely-insulated framed houses the roof gains and wall gains are going to be at least as big. Top floor rooms get it the worst, the southwest corner more so than the southeast, since it gets more wall gain at a hotter part of the day, after the low-R head-banger sloped roof is already smoking-hot. It'll get a lot better if you insulate the roof from the exterior and bring the kneewall spaces fully inside the conditioned pressure & thermal envelope.

    Night ventilation and closing (and shading) all windows during the day will help a lot, but often the upstairs rooms will be cooking while the downstairs is still below the outdoor temps, so you'll be having some trade-offs to contend with if relying primarily on convection cooling. If it's possible to cross-ventilate the upstairs with a fan while keeping the downstairs windows closed (at least until the outdoor temps drop below the first floor temps) it can work OK.

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