Heat Pumps Work Miracles

Re:Heat Pumps Work Miracles by ip26 on Thursday February 28, 2019 @12:32PM (#19273122)

I've gone through the exercise of retrofitting insulation. Unfortunately there are a few things that are extremely hard to get past. 2x4 walls can only be insulated to R-13 or so unless you're replacing the siding. Subslab insulation can pretty much only be done when it's poured. Joist insulation & air sealing can be very hard to get to.

I can only hope 2x6 framing becomes more common, the subslab insulation has started to become code.

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Re:Heat Pumps Work Miracles by bluGill on Thursday February 28, 2019 @01:43PM (#19273865)

2x4 can be insulated much higher - around R26. You need to use expensive closed cell foam to do this. It is much cheaper to build with 2x6 which gets you to R19 with cheap insulation.

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Re:Heat Pumps Work Miracles by ip26 on Thursday February 28, 2019 @03:20PM (#19274736)

You can't easily retrofit spray foam though. Either the drywall or sheathing needs to come off, unless the cavity was empty, and even then it doesn't fill evenly if sprayed in a single hole.

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Re:Heat Pumps Work Miracles by rootusrootus on Thursday February 28, 2019 @12:36PM (#19273168)

2x6 framing should be nearly universal on new construction, which calls for R19 according to the international building code.

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Re:Heat Pumps Work Miracles by Scoundreller on Thursday February 28, 2019 @02:00PM (#19274040)

Ahh, so this is why building my 3 season shack is damn near impossible financially.

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Re:Heat Pumps Work Miracles by everial on Thursday February 28, 2019 @03:48PM (#19275028)

> I've gone through the exercise of retrofitting insulation.

Based on your experiences what do you recommend? (or what sources do you recommend consulting to learn more about retrofitting older buildings?)

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Re:Heat Pumps Work Miracles by ip26 on Thursday February 28, 2019 @04:55PM (#19275623)

finehomebuilding, familyhandyman, and greenbuildingadvisor are all valuable resources with a different bent to each.

Counter-intuitively, air sealing is usually the #1 improvement. A good audit with thermal scans is worthwhile, especially if your muni offers a subsidized audit.

Tough to go into more detail without a little more information.

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Re:Heat Pumps Work Miracles by Gibbon1 on Friday March 01, 2019 @02:05PM (#19284174)

> Counter-intuitively, air sealing is usually the #1 improvement.

I think the hard thing for people to think about is that heat transfer is exponential. But we don't measure it that way. In fact R values are really misleading[1].

Meaning transfer coefficients can vary by orders of magnitude. So it's easy for one source like air leakage to totally swamp every other source.

[1] Figure of merit is really 1/R (smaller is better) not R.

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Re:Heat Pumps Work Miracles by everial on Friday March 01, 2019 @11:31AM (#19282289)

Thanks for the recommendations.

> Tough to go into more detail without a little more information.

Have a ~1800 square foot single family Colonial located in Northeast USA built around 1910. It was partially renovated ~2000 but most of it's still uninsulated (afaict, still very new to this!).

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