I built an addition with 2x4, OSB, housewrap, 1" foam insulation, vinyl siding. Foam boards are used all the time so they must be to code.

You could build a frame around each door and window so you don't have to disturb them at all.

Thanks, hendricus. What kind of 1" foam? How much R value is it rated to provide? And, if you don't mind my asking, roughly how much did the insulation cost for how much wall area? (Estimations on these would be better than nothing - thanks.)

Joel

There are several aspects to what you propose. Adding external foam sheathing would allow you to increase your air infiltration control by an order of magnitude from what you presently are capable of. This could be accomplished by taping the seams of the sheathing or using a Tyvek/Typar type barrier as well. Fiberglass batts don't resist air washing/infiltration and this added control would increase their effectives as an insulation.

Next, adding external sheathing would allow you to bring your home up to the minimum recommended levels for your area. The government has a neat zip code program to recommend insualtion levels within homes. (The recommended 2x4 wall insulation for my area is R-13 stud insulation (we used cellulose) with an R-5 (1") foam sheathing for an R-18 wall.) There should be no code issue with doing any of this.

You need to be realistic, though, and look at what is cost effective. I'd suggest investing in a program called HVAC CALC, about $50 for a one-time home license, and do a heat loss/heat gain calculation on your present home. This way you could see where your heating/cooling dollars are actually going - walls, windows, ceiling, doors. Some have bad-mouthed this program, but I have used it on several homes and most recently on our new home and it came in dead-nuts the same as the programs the pro contractors had. I would guess it's going to be a toss up whether your walls or windows would be most cost effective to upgrade.

As far as the actual cost of doing the upgrade to the walls, there are so many variables. How much/how thick a foam insulation to use. Extruded polystyrene or a higher peformance polyisocyanurate foam board? Can the existing siding be reused or will that have to be replaced? Hardiboard siding or vinyl? Hardiboard needs to be painted. Is this a DIY job or will this be contracted out?

Finally, the Building Science Corp. website is full of useful information applicable to your situation.

http://www.hvaccalc.com/

http://www.buildingscience.com/index_html

Hope this helps!

Here is a link that might be useful: Zip Code Insulation Program

Thanks for the info, suggestions and link, formula1.

Has anyone here heard anything about the "nanotech" coatings that apparently can be painted on an exterior wall (under the finished surface, obviously) - and are said to have a very high R value? If so (and if they are efficient like the manufacturers' PR people claim), how effective are they? And, I've heard that somertimes they are painted onto the interior surface of an exterior wall (under the finish wall paint, panelling, or other surface treatment). So - contemplating painting such a product on as a sub-coat on the interior of a wall - have these coatings been determined to not gas-off or be toxic to the home's residents?

Joel

The pink stuff at Menards, tongue and groove, 10-12 dollars a 4x8 sheet. The room is heated with a 4"x25' insulated heat duct coming out of a 2"x12" floor register and has a 10' opening into the kitchen. No drafts or leaks.

I would compare the cost of removing exterior siding, adding XPS and detailing around the windows vs. the cost of removing interior finishes and spraying in closed-cell foam @ R6 per inch.

You might also consider removing the interior trim around the windows and sealing the space with low expanding foam. I'd bet the original windows are only sealed in with some fiberglass and maybe a vapour barrier. If the windows are metal, they're not very effective in insulating and might be changed too. At 30 years, they're probably due for replacement anyway.

Also, check the insulation (if any) between your floor joists at the rim and the first four feet down into your basement. Improvements here will make a big difference, with likely no problem with surface finishes.

There are some thin-coating materials coming on the market, that claim to be a product of (nano-technology( research. Apparently, these can be used as undercoatings to the decorative paint on an interior wall. According the the manufacturer, the R value is very high (though I have not run into a numer rating).

Here is a link that might be useful: Nano tech wall coating

According to the manufacturer, the R value cannot be determined because the coatings are too thin.

Instead, its claim--and those of the makers of ceramic paints--is that their coatings provide a reflective barrier to radiant heat.

Used on the warm side of the basement, the barrier would presumably reflect the warm interior air away from the cold wall thus blocking mould growth.

Here is a link that might be useful: Consumer's Guide to Radiant Barriers

I knew one fellow who thickened his walls by adding true 1" furring to the inside and putting foam sheets in the cavities. Then new drywall on the furring. Unconventional to be sure.