Insulating Problem

hot_rod

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hot rod

Patrick North

Insulating stone

A bit off topic, but you all are batting 1000 with my frantic questions this week, so...

The first floor of our house is 1' thick limestone. 2X4's (more like 3X6's) fir out the inside walls, with lathe and plaster over top. We're in Central PA- warm in the summer, cold in the winter. We had great success blowing in cellulose insulation in the attic and upper floors, and now want to finish the job- or do we? I've seen enough info cautioning against insulating behind various types of masonry, but this usually seems to pertain to filling air gaps between wythes of brick structures. Concerns of sweating masonry fouling the insulation, etc. Plus, I've seen lots of contradictory information about why one should/shouldn't insulate the inside of thick stone walls (they retain lots of heat- no, they require too much heat to bring to temp!). In other words, lots of science that doesn't quite seem to pertain, and LOADS of contrary "common sense."

So what should I _really_ be doing, here? Yes, there may be more important insulating projects in this case, but we hope to wallpaper soon and it's now or never in terms of drilling holes in the walls.
thanks,
Patrick

Patrick North

good info

I've checked this out before, and it's the source of some of my fretting. From the one pertinant article (I think it was referenced on these boards recently) they seemed to be arguing for filling the space between the masonry (stone in my case) and plaster completely with spray-in foam, not just the first X inches with dimensional insulation like bats or boards. The key point seemed to be filling the gap completely. Didn't get an idea of what they thought about celulose, and wasn't sure what to make of the recommendations for vapor permeability with regards to the interior walls.
Anybody out there read this article with a better idea of the recommendations than I could decipher? Seemed very authoritative: http://www.buildingscience.com/documents/digests/bsd-114-interior-insulation-retrofits-of-load-bearing-masonry-walls-in-cold-climates

Mike T., Swampeast MO

The best place to insulate a solid masonary structure--be it stone or brick, above or below grade--is from the outside. Once you have the indoor air, the contents of the structure and the walls themselves at a comfortable temperature, they tend to stay that way. Indoor heat doesn't like to leave and outdoor heat doesn't like to enter.

With proper flashings/etc. an EIFS (exterior insulation/finish system) will prove both effective and relatively inexpensive. Of course such will drastically alter the outside appearance of the structure...

If you insulate the interior surfaces there is a BIG difference between above-grade and below-grade. Above-grade, I believe that Icynene or similar will be best. Below grade, you're probably best off leaving it uninsulated and uncoated by anything except latex paint. If you must finish and insulate (interior insulation) below-grade, the proper detailing is both finicky and quite expensive.

Patrick North

Icynene is best...

...but would cost me thousands more than cellulose. Other than lesser insulating value, think there's any reason not to use it?
Thanks,
Patrick
ps- another cool window rad:
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