[Greenbuilding] temperature stratification rule of thumb (in two-story house)?

John Salmen terrain at shaw.ca
Tue Jul 8 19:01:41 MDT 2014

Hate s/w windows (except in the wintertime). Suspect that is the culprit for interior heat gain. Given the sun angle a simple strategic window overhang might take the brunt of it (or shutters/blinds but they involve people). I like some of the lower sun west gain at the end of the day as it can be cooler here in summer evenings and an overhang can still allow for that as well as winter sun.



From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Reuben Deumling
Sent: July-08-14 5:47 PM
To: Greenbuilding
Subject: [Greenbuilding] temperature stratification rule of thumb (in two-story house)?


I'm working on a remodel/turn house into a duplex. In the upstairs apartment that is being carved out of the existing house (with 2x6 walls insulated with fiberglass batts) I've increased the exterior wall thickness by 4 inches and blown cellulose into the cavities ~3.6lbs/cf, leaving the drywall in place (now in the middle of the wall). I've also lofted the attic and created a double rafter setup with the interior set of fiberglass batts running horizontally. Total insulation thickness is about 10-1/2" in the vaulted part as well. White metal roof.

It is summer. I've finished all the insulation, and have temperature monitors in various places around the house. To my chagrin, the temperature in the now much better (more carefully and thicker) insulated portion is no different than in the equivalently oriented part of the upstairs. Both are only about 7 degrees cooler than the outside 80F vs 87F. Downstairs, also with R19 FG walls, it is 75F. 

By lofting the remodeled portion I've of course incorporated the attic-as-hotter-still upper layer, but I had hoped the extra insulation and attention to detail would overcome this. I did not leave any air gap between the vaulted insulation and the roof sheathing. 

There is a bank of windows (as yet un-shuttered) on the S/W gable of this remodeled part which gets the full brunt of the afternoon and evening sun. The Chestnut tree still has about three years to grow before it starts to shade that part of the house. Tomorrow I will experiment with makeshift shutters in the afternoon and see what difference that makes. 

Question 1: are there rules of thumb about heat stratification in a two story vaulted/unvaulted house, all else being equal? 

Question 2: from my description, are there things I should have done, could still do, to improve the summertime thermal performance of this space? 

Thanks very much.

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