ROI for insulating 2nd floor walls
Hello GBA,
Fair warning that the answer to my question may be “as you wish” since there are very personal reasons for deciding one way or the other, but I am hoping for some advice that is able to balance the ideal and the practical.
We have been undergoing a VERY long renovation of a 50’s brick cape in Southern CT. For those areas that we have needed to demo (and some we didn’t) we have been insulating and air sealing as we have been going, with great results. Now we are down to one last bedroom which for several reasons was planned to be done last. It is a 2nd floor bedroom, approx 180sf, plaster-on-gypsum board walls which are in excellent shape for their age. There are three exterior walls pretty evenly split between a 2×4 wood dormer and brick on 4″ cinder block with a few air gaps in between (this is one gable end of the house, with a reverse gable in front, also brick/block). The attic is insulated to R38 and we plan to blow in cellulose later to bring to R49. The 2×4 dormer walls are insulated with 50’s era balsam wool, which I’ll kindly say is better than nothing at all. The block portions are unisulated save for the air gap.
This room when heated has always held heat fairly well despite itself, especially so now with better attic insulation. Where I am torn now is whether it is worth it to break down the exterior facing walls to properly insulate, or just to air seal as best I can (new windows have already been installed and trim is being replaced so I have access). My wife, whose patience has pretty well run out, has no further stomach for the typical dust/debris/hassle that doing this would bring. Me, wanting consistency, feel obliged to bring it up to modern standards, but I am also very tired.
And therein lies the question. I have seen others posit (maybe not here) that demoing a wall just to insulate it is seldom worth the trouble, especially for a 2nd floor room with an attic insulated to modern standards. Do you experts share that opinion? Alternatively, I would be willing to consider other solutions if they are not too obtrusive… the room WILL be getting SOME minor updating so drilling holes etc is not out of the question.
Sincere thanks for sharing any experience! This is a wonderful resource.
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Replies
G.S.,
The answer to this question lies in the realm of marital relations, not building science. Listen to your wife. Marital harmony is worth more than lower energy bills.
Excellent advice! Good for you, Martin. And I agree wholeheartedly!
If the balsam wool fill is fairly complete with no gaps, fuggedaboudit. It's doing something, and the difference "whole wall R" between R8-10 center cavity and R13 center cavity is much smaller than it seems. It's not worth re-doing unless you were going to gut the plaster for some other reason.
If you CAN detect gaps using an infra-red camera or IR thermometer, mark the locations lightly with a pencil, and discuss it with the cellulose contractor prior to doing the attic. It's possible to spot-fill the gaps with cellulose with a minimum of muss/fuss using a hole saw to drill. Competent dense-packers often do entire walls from the interior without creating a huge mess, are in and out in a day, and the up-charge for an hour of spot-drill & fill while they have the equipment & crew on site for the attic job will probably be pretty reasonable.
Perlite poured into the cores of CMU block delivers a modest improvement in thermal performance, and may be "worth it" if the access is easy. If the access is more difficult there are more expensive injection-foams that could be used too, which would also improve air tightness somewhat.
Martin... you are truly wise :)
Dana... thanks for the detailed answer. I suspect the balsam wool fared no better than it's brethren in the attic which were basically decimated by gravity (and squirrels, but mostly gravity). Guessing the bottoms of the cavities are quite full and the tops less so. I'll review with the contractor as suggested and see what's what.
thanks for the advice (and saving my marriage in the process! :P)