How to insulate main floor walls without destroying look of house?

[djenkins6]

I have a 1.5 storey house poured concrete foundation, main floor walls built from a single layer of 'Angelstone' - actually hollow concrete blocks with a stone look face, they are about 8*8*16 inches. Inside the walls are strapped with 1" furring and some sort of fibreboard with a coat of plaster. The house is 1950's and have beutiful handcrafted coving so I don't want to destroy the interior cove or exterior 'stone' look (even if it is fake it matches all the other houses).

I have already insulated the basement to r20 with solid foam and spray foam around the rim joists. Also as part of major reconstruction the attic has been insulated with spray foam on the old roof deck and a new roof deck added with air gap before the final plywood and shingles (we also spray foamed on top of the outside walls.

So the only part not insulated in the 8ft high main walls - I was thinking of drilling holes in the drywall on main floor and spraying in the foam in a can made for doors/windows so as not to expand the drywall. Is it worth adding this 1" of insulation as the exterior wall is currently estimated as only r4? I read some articles that said that first inch gives a great reduction in energy and then falling return - I would do it myself over a period of time so labour is free and as only 1" gap not going to take much foam.

David

[m Ransley]

Don`t you have 3+ " of wall space for foam.

What is attic R value, 60R+ is helpfull , I put in R 110 attic , and it settled down 20% to maybe R 80.

What Zone are=A0 you, whats your bill for Ng. Windows are a major issue next.

[djenkins6]

I'm in Canada, Southern Ontario so we get some cold days and some hot (-20 to +40 degrees C at extremes but only a few days like that each year. Winter I'd says a usual cold day would be nearer -10C and summers in the +30C quite often. I have r20 in basement, and must be close to r50 attic. the windows are vinyl with low-e double glazing.

Yes it really is a single layer of concrete blocks, each block has 3 cavities in it but I think it would be nearly impossible to fill those holes with insulation, and anyway there is so much webbing in the block there would be a thermal bridge of concrete to transmit the cold.

The block is a bit like the 'Split Face Scored' 16*8*8 on this page except with three cavities

Then inside is the 1" strapping (true 1" gap as it's 50 year old wood) then layer of felt and then the layer os some sort of fibreboard about half inch thick and a layer of plaster.

Most of the winter it's ok but we get some condensation on inside of walls on the very cold days, and the fact when we get a windy day the side of the house receiving the winter wind stays cold. Would 1" foam in the gap be enough to make the walls warm enough not to condense? would filling the air gap cause problems - e.g trapping moisture and actually make things worse by making somewhere for mold to grow and stopping the wind drying the inside of the wall.

[Don Young]

I personally feel that trying to foam the 1" space would be a waste of time and money. I do not think you can get any significant filling of this type of space without a lot of openings and even then there is no easy way to know if there are large gaps. As you mentioned, moisture could be a problem. I would just live with it unless I was willing to install solid foam board and re-do the walls.

Don Young

[djenkins6]

These folk are recomending a technique here

but of course they are selling the stuff.

I also have an MT4 IR temperature sensor

look for gaps (I got it on ebay for $35 but it works)

Apparently a 12oz can of great stuff = 13 litres so a wall 12ft wide by

8ft high and 1" cavity should take 16 cans according to my calculations (lets say 20 to be safe) and they are about $10 each in home depot so about $200 to insulate a wall. and I'd have 12 to 15 small holes to fill. I have the equivalent of 6 sections of wall like that to fill.

Alternative, rip off the drywall, leaving the nice cove at top and the baseboard... spray behind nice cove and skirting board = 5 tins spray = $50, 3 sheets of 1" foam board = $50, 3 sheets drywall about $50 = about $150.

Ok now the big question is so how much energy have I saved by spending my $1200..... basically going from r4 to r8 walls.

PS. gas bills were $350 a month but that was before I insulated the basement and roof and put in the 94% furnace, old furnace was 60% efficient at most.

I found this

seems to say that using 1" of foam boards you get your money back fairly quickly (1 to 3 yrs) as it would halve the heat loss through the walls, and then diminishing return as you get thicker board.

Now if I saved 50-60% by doing the roof and basement and furnace already, my annual gas bill should be $1000 or so instead of $2000 - or maybe it will end up at $2000 with rising/falling gas prices, and if I hadn't insulated I would be looking at $3500 dollar bills this year :)

So if doing the walls saves 20% a year... equals 6 year payback at last years gas price, or 3 year payback if the gas price is high. And hopefully nice and warm and no wall condensation!

[HeyBub]

Can you build, or plant, a wind break on the outside?

[Nick Hull]

I have a concrete block house, I put 6" of insulation on the outside and have a warm house that is cheap to heat. You can live with a different exterior and re-doing the exterior is probably cheaper and more effective than messing with the interior.

[DT]

You don't want to try it with Great Stuff. Tiger Foam makes a cavity fill foam in do-it-yourself kits:

You can also fill the block with perlite, although you have to be able to get at the top of the blocks to do it, so that is probably a problem.

-- Dennis

[djenkins6]

It's certainly a lot cheaper buying in bulk, Tiger Foam even have a Canadian site! - I'll follow up with them about a smaller pack, 600 board feet for slow rise is double what I need, plus I'd have to do the whole house in 5 or 6 days. I don't think my wife will appreciate holes all over the house in one go, probably better if I can do one wall section at a time or at least one room at a time and fill the holes and paint then move onto the next room.

David