Two walls Vs Q-con blocks

Air conditioning, fans, and anything related to keeping it cool, such as insulation. This would include any posts generally discussing how to keep it cool, such as which types of blocks are better insulators.... ideal wall thickness for keeping an A/C house cool, etc.

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Two walls Vs Q-con blocks

Postby steady » Sun Feb 03, 2008 8:32 pm

Does anyone have info relating to building two walls with a cavity (with or without PU insulation) as opposed to 20 by 20cm Q-con blocks. I'm only trying to compare insulation qualities or any other technical reasons for choosing one over the other. It seems very much a grey area as each supplier tells me theirs is best (not surprisingly) but neither one came up with any figures or anything I could compare against. I've read things on the forum about window sizes, vents in the roof and direction the house is facing all have more effect on the temperature of a house. Anyone with firsthand experience or just good points of view?

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Postby dozer » Sun Feb 03, 2008 9:06 pm

I don't have a definitive answer and not sure if one exists out there. The light weight blocks are good insulators, and so is the double wall construction with either a air void or insulation in the void. IMHO, From being in both types of houses I would say they are both the same in this regard.
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Postby Vansana » Mon Feb 04, 2008 8:24 am

My fear is that the cavity between two walls will be a superhighway for termites, ants and other unwanted creatures.

Q-con has a lower thermal mass than Concrete blocks.
The only problem I see is that (at least in my region) construction workers can not handle Qcon properly. Even he architect i talked to so far wants concrete blocks and thinks this is the non pus ultra, since everybody else here is still using the small red clay bricks.

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Postby dozer » Mon Feb 04, 2008 8:42 am

Yes, the cavity can be filled to allay such fears, but if property done there is no entry path to the cavity, it should be sealed. I have seen burnt rice husk used to fill the cavity, which is a good solution, alternatively Styrofoam sheeting.

I used to have the same fear about QCON blocks, but they are really easy to use and most workers now have experience with them. It is just a matter of getting the right bonding material and render cements to use with the product.
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Postby Nawty » Mon Feb 04, 2008 9:12 am

They seem to be as mentioned, both similar results achieved.

The bonus with a cavity is that you get a path built in for all your services and then there is no cutting into walls repeatedly like with Qcon or Superblock.

I used superblock and very happy with it...except for the continual cutting when something forgotten or changed or just for fun so it seems.

The other factor is cost and I do not know the difference between the 2.

Another option is the superblock/Qcon on the outside and then a studded wall on the inside lined with gyprock sheets. You get the benefits of the new lightweight blocks and insulation qualities and the cavity for services.

I am going to use this method next time, dependant on what the costs work out at.
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Postby dozer » Mon Feb 04, 2008 9:51 am

Cost wise the QCON blocks are substantially higher than double wall cinder blocks or red brick. The raw cinder blocks are 3.5 baht each (x 2) where the QCON blocks are on an order of about 40 baht. The red brick is about .50 baht per brick. I do not have it worked out on a per square meter basis, if anyone does please post it.

The bonus with a cavity is that you get a path built in for all your services
Yes, the cavity is a very nice feature of double wall. This is why, in the end you wouldn't want to fill the cavity with concrete, to allow access in the case of repairs.
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Postby Rick B » Mon Feb 04, 2008 9:58 pm

I've recently seen 60x20x7 blocks similar to Superblock being sold in HomeMart and HomePro for considerably less than 40 baht each. I think the company's name is Thai Crete who makes this block. The salesperson at HomeMart says these blocks have all of the same features/characteristics of Superblock or QCon blocks, plus the additional benefit that you can use regular cement for mortar and for rendering. No special adhesive is needed. I was quoted a price of 14 baht per block if I buy more than 2,000 at a time.

Does anyone have any experience with these newer blocks?
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q-con

Postby cruzing » Wed Feb 06, 2008 12:27 am

Dozer, you'll remember our friends house across the canal that you were in the other day??? That is q-con but double walled q-con. They did it this way for several reasons. One they felt that our cavity walled concrete block house was cooler than the q-con single walled houses they had been in. Secondly, the builder usually builds in q-con.

If we would ever use q-con in a project we would probably use some interior wall as Nawty mentioned....but with supporting beams in the walls.

Q-con is not approved in CA. at least because it will not withstand an earthquake. I'm not sure about the rest of the u.s.a. but I haven't been able to find anyone that has it and a search on Yahoo u.s.a only says it's invalid.

I think the biggest blocks would offer the best results, but they are still rather pricey.

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Postby steady » Wed Feb 06, 2008 7:51 am

Cruzing,

I originally thought that the Q-con blocks were pricey. I have been quoted around 40 baht for one 20x20x60 block (with discount for buying a house load) but when I did my sums compared to a double wall with the cavity filled with PU foam insulation it then becomes a lot cheaper. Q-con is actually roughly half the price. The actual figures came out to roughly 70,000 baht for Q-con to 23,000 baht for enough small bricks for 2 walls but the insulation would have been about 120,000 baht.

So now I feel that the only way to improve on this would be to do as you said and make 2 walls of Q-con but then how much more benefit would you get for your baht?

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q-con

Postby cruzing » Wed Feb 06, 2008 4:12 pm

we used burnt rice husks.........all natural.......can't burn, bug won't eat it,
might even have some air purifying benefits who knows. Anyway, 4-5,000 baht for a truck load and when we were done we had a whole lot left over.............or you can do like our friends are going to do and leave the space empty and let the air flow......worried about critters, use screening.

I was kind of for the method of just let the air flow, but the Mr. wanted to insulate.

Also, if you do the q-con blocks and still want double walls, your interior second wall, like Nawty mentioned, doesn't have to be q-con.....it can be anything, it's the gap that matters.....and you need more than two inches in our opinion.

I for one would not be willing to pay 120,000 baht for foam insulation.

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Postby dozer » Wed Feb 06, 2008 7:25 pm

cavity filled with PU foam insulation it then becomes a lot cheaper.
I would agree with Cruzing that this is a very expensive option for insulation. I've seen the rice husks and foam sheeting used, both excellent insulators and not expensive.
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Postby steady » Wed Feb 06, 2008 9:49 pm

I'm trying to find things that are measurable (compared to each other) when it comes to insulation - and failing pretty miserably. I'm trying to look at all aspects, insulation value, how long it will remain in good condition, fire or smoke hazards etc etc. How do you measure rice husks for insulation value and how did you find out about them in the first place? Do you know how long they remain in a stable conditiopn? So with the Q-con insulation values is there any benefit of using rice husks over an air gap if one or both walls are Q-con?

It would be so much easier if someone published the insulation values of all of these materials......but then would we trust what they wrote anyway?

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Postby tung » Wed Apr 02, 2008 3:02 pm

Any idea what the recommended thickness for Q-Con on external walls is?

I would imagine that the thinner 7.5 cm ones are way to thin.

What is the normal thickness of an external support column for a 2 storey house, gives me an idea of how much of the column will be visible internally.
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double walls

Postby cruzing » Wed Apr 02, 2008 9:02 pm

tung wrote:Any idea what the recommended thickness for Q-Con on external walls is?

I would imagine that the thinner 7.5 cm ones are way to thin.

What is the normal thickness of an external support column for a 2 storey house, gives me an idea of how much of the column will be visible internally.


If you use the large Q-con type blocks and are doing a single wall, your columns won't even show inside. double walls, they definitely will not be exposed inside. Personally I don't know why anyone would even want them to show on the interior. As far as cleaning and being in the way they are a pain. Even if you are not using q-con type blocks, and still doing the thai style construction with pillars you can build it without the pillars being exposed inside.
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Postby jazzman » Thu Apr 03, 2008 10:36 am

As Dozer mentioned, the standard cinder blocks which have three holes in them, already have excellent insulating properties and are all that is needed if one is not building a load-bearing wall. A double cinder block wall will have even better insulation, and as Cruzing stated, filling with rice husk will add more - but it is essential to ensure that the gap will stay perfectly dry. If the rice husk gets damp it will lose its insulting effect.

The Jazzman house - a budget build - only has single cinder block walls, the house has no aircon, and is beautifully cool.

Reading back over this thread, it seems that the OP wants to know how much insulation he really needs, and at what price. Newcomers to the tropics often imagine they are going to need loads more insulation than neccessary. There are no tropics in Europe, but people who have lived in S. California or northern Australia will know what to expect from the heat in Thailand.

Building walls with the small red bricks is a labour intensive, cement costly solution that has much lower insulation than the cinder blocks. It's a leftover from the days when Thais build houses with mud bricks and before they came up with the idea of mass producing the cinder blocks, but there are still plenty of traditionalists that do it, as can be clearly seen from all the rows of new shop houses going up in Soi Country Club and Soi Neun Plub Wan.
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