Double Walled Construction

[Trex52]

Am thinking of using an AAC block on all exterior walls with a possible inside red brick with air space between on west facing wall, especially. I know it would not be as efficient as AAC block for both courses, but cost is an issue. Have gleened most of the posts here related to AAC block construction. I have cut and pasted for file so I don't have to re-look up for later. But need to know if someone has done this and how good does it do the job? Thanks in advance. trex

[fremmel]

When I built my house I was thinking about using AAC block on the outside but then started reading about double walls and started to run some numbers. The R-value for 7.5 cm AAC is 3.25, thin concrete block is 0.8, and red brick less than 0.4. For a double wall you can add about 1.0 for the air space. But, 2" fiberglass has an R-value of 7.7 and fits nicely in the cavity when you're making up a 20 cm double wall. That gives an R-value of about 10 or 11 for a double block wall with stucco and fiberglass in between. Better than 3 times more than AAC block alone and at about the same price. So I went with that and have been very happy with the result. I have full sun exposure on the west wall and even late in the afternoon the inside of the wall is about the same temperature as the inside partition walls.

[Trex52]

When I built my house I was thinking about using AAC block on the outside but then started reading about double walls and started to run some numbers. The R-value for 7.5 cm AAC is 3.25, thin concrete block is 0.8, and red brick less than 0.4. For a double wall you can add about 1.0 for the air space. But, 2" fiberglass has an R-value of 7.7 and fits nicely in the cavity when you're making up a 20 cm double wall. That gives an R-value of about 10 or 11 for a double block wall with stucco and fiberglass in between. Better than 3 times more than AAC block alone and at about the same price. So I went with that and have been very happy with the result. I have full sun exposure on the west wall and even late in the afternoon the inside of the wall is about the same temperature as the inside partition walls.

Thanks for the input...great to hear. The two inch fiberglass you mention, is just regular FG insulation? I was going to go with a dead air space only, but having been involved in the recording studio construction business back in the 70's, we did use a lot of FG for various baffles and bass traps, come to think of it. Hmmmm....Well the Q-con has been ordered and I guess I will go with that and a sinlge red brick inner wall on the western wall. I have two big windows facing the mountains and plan to put up high trellises so as not to block the view, but give a filtered, shadow type shade for the blistering afternoon nuclear thermo zap. Now I am planning the roof system and it is looking like CPAC Monier is the only ball game here, or at least all I can find. Thanks again for the wonderful input....trex

[Trex52]

When I built my house I was thinking about using AAC block on the outside but then started reading about double walls and started to run some numbers. The R-value for 7.5 cm AAC is 3.25, thin concrete block is 0.8, and red brick less than 0.4. For a double wall you can add about 1.0 for the air space. But, 2" fiberglass has an R-value of 7.7 and fits nicely in the cavity when you're making up a 20 cm double wall. That gives an R-value of about 10 or 11 for a double block wall with stucco and fiberglass in between. Better than 3 times more than AAC block alone and at about the same price. So I went with that and have been very happy with the result. I have full sun exposure on the west wall and even late in the afternoon the inside of the wall is about the same temperature as the inside partition walls.

Thanks for the input...great to hear. The two inch fiberglass you mention, is just regular FG insulation? I was going to go with a dead air space only, but having been involved in the recording studio construction business back in the 70's, we did use a lot of FG for various baffles and bass traps, come to think of it. Hmmmm....Well the Q-con has been ordered and I guess I will go with that and a sinlge red brick inner wall on the western wall. I have two big windows facing the mountains and plan to put up high trellises so as not to block the view, but give a filtered, shadow type shade for the blistering afternoon nuclear thermo zap. Now I am planning the roof system and it is looking like CPAC Monier is the only ball game here, or at least all I can find. Thanks again for the wonderful input....trex

Addendum....CPAC Monier is the only one with a ridge vent system. I forgot to add that part. I know there are other roofing material companies, but I plan to go with a lot of soffit venting and if I can find it, continuous ridge venturi style vent. Gable louvers, even the type in the US that is a lot bigger with more area, than the little wooden shuttered looking ones I see here, are anything but efficient. I will be going to CM this weekend to look at CPAC's Monier Cool Roof System. trex

[fremmel]

Yes, the 2" fiberglass is just a plain fiberglass batt in a foil covered plastic envelope. I saw some this weekend at Global for about 120 baht a roll. I didn't pay much attention but that was probably a 60 cm x 4 m roll. It's really a cheap way to triple the R-value of your double wall.

[Rimmer]

Yes, the 2" fiberglass is just a plain fiberglass batt in a foil covered plastic envelope. I saw some this weekend at Global for about 120 baht a roll. I didn't pay much attention but that was probably a 60 cm x 4 m roll. It's really a cheap way to triple the R-value of your double wall.

Try holding a cigarette lighter under it, does the plastic burn? I did this in Homepro one time with a small sample the assistant gave me, the thing burst into flames and dripped hot melted plastic on to the floor.

[fremmel]

Are we talking about the same stuff here? I'm talking about the fiberglass batts that you can get here in the 60 cm by 4 m rolls that are 2", 4", and 6" thick. You can get them plain or enclosed in a very thin, what I'm guessing is, metalized mylar "tube" or bag. Not the foam backed foil radiant barrier. To check it out I cut a piece off of what I used and tried to light it. The fiberglass, of course, didn't catch fire. The mylar mostly just shriveled up. I did finally manage to light it when I crumbled up a wad of it.

If we're talking about the same product I'm not sure of the point you're making. Is it that fiberglass insulation in the mylar is a fire hazard?

[Hssl]

http://www.topinsulation.com/

Better than the fire hazard foil stuff!

[fremmel]

I guess you're talking about the Fibertex rockwool and not the Staycool fiberglass on that page. Looks like a good product with similar insulating properties. Haven't seen any in home center type stores so I don't know how much it is.

As far as the mylar bag being a fire hazard, that's a pretty negligable amount of combustible material between the walls. Just for comparison I tried lighting the insulation on the Bangkok Cable VAF, which I also put between the walls, and it lit pretty readily. Although it does seem to be self-extinguishing. Gave off a lot of fumes though. Every house I've lived in before coming to Thailand had hundreds, if not thousands, of kilos of highly flammable wood in the walls. A little bit of mylar doesn't seem unduly hazardous.