wall insulation

[Andyfteeze]

Most people will build to a compromise they are happy to live with. Lets face it, even a badly built thai style brick house can be made acceptably comfortable with an airconditioner. But that's not the point. Just a little more thought and effort can make it better built and cheaper to run. Win Win. Sorry if I appear blunt at times, but I hope I can inspire people to do a better job, not be happy with near enough. I am an aussie, I call BS for what it is.

[BKKBILL]

Just leaving a gap is lazy thinking. Even basic foil gives 50% better r rating.

just using common sense.

Sorry to tread on your toes pipoz, but if your happy with just an air cavity, that's fine. Not going to dispute that it is effective, but for not much more outlay ie foil, its 50% better.

Most people will build to a compromise they are happy to live with. Lets face it, even a badly built thai style brick house can be made acceptably comfortable with an airconditioner. But that's not the point. Just a little more thought and effort can make it better built and cheaper to run. Win Win. Sorry if I appear blunt at times, but I hope I can inspire people to do a better job, not be happy with near enough. I am an aussie, I call BS for what it is.

Andy, Andy, Andy in one thread you have us thinking lazily, not using common sense, tread on pipoz toes, then claim to inspire people to do a better job. We are talking about a gap of less than two inches between what red brick, cement block, ACC block, do we know yet you claim foil is 50% better, better than what?

I think you are just giving Aussies a bad name, but maybe that's just my thinking.

Why I even bothered to post, after a lot of research I built with double 7.5 wide ACC blocks that are sealed to create a dead air insulating space as have most of the posters here have done.

Think if you have a different opinion post it without trying to disparage other members, as that is BS IMHO.

[Sometimewoodworker]

I hope I can inspire people to do a better job, not be happy with near enough..

This is Thailand. If you can get to near enough. You're doing between good and fantastic already. Don't forget we have Thai workers.

[Andyfteeze]

Ahh come on! Read between the lines.
+foil is nearly 50% better R rating. do I have to do it again!

face brick r= .44
air cavity r= 1
total r=1.88

facebrick r=.44
aircavity r=1
foil r=.8
total r=2.68

1.88/2.68 = .7

A 70% improvement. You dont have to think too hard to see an improvement. Still cant see it BBKBILL?

[Andyfteeze]

I did make just a little mistake. I apologise for that.

2.68 -1.88=.8
.8/1.88=.42 42% improvement. In my excitement, I forgot some basic maths. But 42% is a worthwhile improvement for little extra thought or outlay.

[Andyfteeze]

" do we know yet you claim foil is 50% better, better than what?"
The OP said a double brick wall with a cavity. 42% improvement with foil in the cavity. BBK, are you still confused?

[BKKBILL]

Think if you have a different opinion post it without trying to disparage other members, as that is BS IMHO.

Ahh come on! Read between the lines.

BBK, are you still confused?

Still cant see it BBKBILL?/quote]


Ahh come on! Read between the lines.
+foil is nearly 50% better R rating. do I have to do it again!

face brick r= .44
air cavity r= 1
total r=1.88

facebrick r=.44
aircavity r=1
foil r=.8
total r=2.68

1.88/2.68 = .7

The things you can do with numbers.

First the OP is not using face bricks but common bricks that have an R factor of 0.80

Second the OP has not one but two walls with an air gap, possibly rockwool, the double bricks should have a combined R factor of 1.76

Third Aluminum foil doesn't have an R rating aluminum foil facing is a kind of radiant barrier material, it is capable of reflecting heat, which discontinues heat transfer or heat convection. So, it can effectively increase insulation materials' thermal insulation performance.

http://www.aluminumfoilcompany.com/service.html

I’m not sure how effective aluminum foil would be in a sealed double brick wall but am sure STWW would be able to answer that one without all the recalculations and fudge factors.

[Roger Ramjet]

I know one thing for sure and that's what the original poster said, let me quote him again:

I am looking for some material for insulating a double cavity brick wall, with a cavity of 5 centimeters.

(taken from when I posted his question the first time).
Now either the original poster has already built the wall, in which case he can't use either rockwool or aluminum and can only use spray foam between that 5 cm cavity, or he hasn't built the wall yet in which case the Thais will not be able to lay the second row of bricks because they'll have to squash the rockwool to be able to lay them, and Thais just wouldn't do that properly and neither would farang builders, they'd make the gap larger.
Everything else is guess work. If the original poster would clarify what sort of bricks he's used/using, the reason why he wants a cavity wall (I take it for insulation) then I would suggest using the air gap as the insulation if he's already built the walls, but, this argument can go around and around in circles with everyone being right or wrong because everyone is guessing at what he's done so far.
Perhaps the original poster would be kind enough to clarify at just what stage he's at without going off and talking about roof insulation. There's a lot involved in all this, especially if he's used red bricks, Superblock, concrete bricks, sealed the cavity wall, hasn't yet built the cavity wall, is thinking about building a cavity wall, because you can't fit 5 cm rockwool into an already built cavity wall and ........ well, I hope people get the picture now. Everyone should take one pace backwards and actually read the question.
This mentality we children have of saying "I don't like him, so he's wrong" is not answering the original question. Come on people act like men.

[preacher]

I start building my house and it will have cavity walls made from red bricks with a 5 cm gap for insulation purposes that I want to fill. (Uttaradit is the hottest province in Thailand and 40+C. is not rare here).

[Klondyke]

I do not believe that any special insulation material inserted in the double wall cavity will change anything on the resulting room temperature.

In a ruin I bought some 9 years ago I had made few extensions by walls of double cement blocks with cavity 3 cm filled in by saw dust (not everywhere 100%).
The existing original walls of simple bricks exposed to afternoon strong sunshine had heated the rooms inside every evening very substantially. The temperature difference by touching was some 5 deg., radiating inside long into the night.


On the original simple walls I had just recently realized an improvement by fixing outside polystyrene white foam 1"thick clad by 1 cm WPC planks (Shera). No difference of the surface temperature of the two wall constructions can be now felt, the temperature seems be same as the other inner walls not exposed to a sunshine. However, in these sunny days and the highest temperature of the year (in the shadow some 42 deg.) the room temperature is coming to 32 - 34 deg., by (simple) windows and other hot air movement entering the house (even if kept closed the whole day).