[giansean]

Hi All,

Fair warning that the answer to my question may be "as you wish" (or maybe "shut up and listen to your wife" ) 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 2x4 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 2x4 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 uninsulated save for the air gap.

This bedroom 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 suggest 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. Does anyone have experience doing it, and was it worth it? As an alternative, I would be willing to consider other solutions if they are not too obtrusive or slow... the room WILL be getting SOME minor updating so drilling holes etc is not out of the question.

Thank you for any advice!

 

[Habeed]

So, ok, your question boils down to : in the Souther Connecticut biome, is it worth insulating cement block walls in a room that is 180 square feet. Several critical pieces of information are missing, but let's see what can be done :

I decided to use Waterbury Connecticut as your city. I used this page for the equations. I'm assuming your room is 13.4 x 13.4 feet, with 3 exterior walls and 10 foot ceilings. 402 square feet of exposed wall.

Loss per degree day : Q = ((402) * 1F) /(R= 3) * 24 hr/day. Q = 3216 BTU/degree day.

So the annual loss is 3216 * 5872 = 18.8 million BTUs.

You didn't say what your furnace was. If it's $1.10 per 100k BTU, this room costs $207 a year to heat.

This assumes a lot of things. Anyways, where you go from here is, you do a PV calculation to find out what the "present value" of saving $207 a year. Really you should redo my math first with more accurate numbers. An R factor of 3 was just a guess really - technically 4" brick is a lot less, but there's air gaps, part of the wall is wool, I don't know how thick the wool is - lots of other factors.

Anyways, once you calculate your present value - and your actual cost per BTU to heat your house, if you're using a geothermal heat pump it's a lot less than if you're burning heating oil - you'll know if it's worth it.

Using the number I gave -> $207/year, the present value is $2700 if you stay in the house 20 years with a 6% discount rate. So if the project costs less than that in materials and labor, it's worth it under those assumptions - you do need to account for your labor costing something. Since it's partially "fun" for you, maybe account for it at minimum wage.