Roof Ventalation

[BillyBobThai]

I will be building a small house, 100 sq. meter, later this year 50 km south of Pichit.

I want this house to hold as much cold as I generate each day as possible. I have read through all of the postings in this forum , and not seen any that address the design that I plan to use. Being from the south of Mississippi in the U.S. , I am used to the heat. I have seen this design used on many commercial buildings that do not use air conditioning. My intent is to passively remove as much heat as possible. It does not matter to me if the local people see my design as weird.

I would like to hear from others on the design.

Thanks to all.

Roof_Diag..bmp

[Naam]

I would like to hear from others on the design.

you won't find the treated cellulose blow-in insulation in Thailand which is quite common in the U.S. of A. i tried my best 2½ years ago. what you get is 15cm (6") thick insulation mats, both sides backed with aluminium foil. not suitable for suspended gypsum ceilings but suitable for your planned concrete ceiling. you will give most probably your builder problems with your roof vent design and i can't see any soffits enabling ambient airflow into the attic.

p.s. roof/attic ventilation (natural and forced) was discussed in a couple threads. please use the search function and you'll find a lot of information.

[tjo o tjim]

The general concept is ok. One idea that is appropriate for Thailand is to provide plantings on the roof to keep down solar absorption, but if you do this I would strongly caution against your clerestory vent set-up because you will attract bugs. You would be better off with a fan in the gable end if that is your intent, or a single square clerestory with a power ventilator.

Despite (some of) the conventional wisdom with insulation and mass for construction, in the tropics you are really best off promoting shade and using lightweight materials that don't absorb heat. The insulation is appropriate mainly if you are going to keep the AC low so there is a significant temperature difference. If you have the brick and concrete ceiling then you will want to bring air into the house from the crawl space at night and vent it up high to cool that mass down for daytime comfort. Moisture barriers are another story though depending on your tolerance for humidity.

[Artisi]

I think you are better off constructing a building with brick / concrete block or lightweight concrete cavity walls, overhanging verandahs and steel roofing with a reflective barrier under. The aim should be to keep as much heat out of the building during the day and be able to shed as much heat from the building as you can during the evening / night. With highly insulated building this is not possible as unfortunately insulation works in both directions.

Your aim should be to keep the inside of the house to the minimum temp. during the day and to get the house back to the lowest overnight temp by morning using the least amount of energy to do it (aircon.)

[Rimmer]

I think you are better off constructing a building with brick / concrete block or lightweight concrete cavity walls, overhanging verandahs and steel roofing with a reflective barrier under. The aim should be to keep as much heat out of the building during the day and be able to shed as much heat from the building as you can during the evening / night. With highly insulated building this is not possible as unfortunately insulation works in both directions.

Your aim should be to keep the inside of the house to the minimum temp. during the day and to get the house back to the lowest overnight temp by morning using the least amount of energy to do it (aircon.)

This is exactly correct, I have lived in a so called insulted house and night time is hotter than h*ll and nothing will cool the place down as the walls are leaching the days heat out of them.

Present house has a 70cm space under the floor, large overhangs, Q Con cavity walls and vented roof space and it is like a meat locker during the day and a deep freeze at night with no aircons.

[tjo o tjim]

Rimmer-- single wythe of Q Con bricks for the walls?

[Rimmer]

Rimmer-- single wythe of Q Con bricks for the walls?

I used 2 x 7.5 mm Q Con with a 7.5mm space in the middle but you can buy Q Con in 7.5mm. 15mm or 20mm if you don't want the bother of making a cavity. Insulation and sound proofing excellent.

I do however have some single 7.5mm Q Con walls that get the sun all day and even those do not get warm on the inside.

[BillyBobThai]

Rimmer- I would like to know what temperature you consider a meat locker and a freezer to be. Not trying to be a smart a*s, but would like some sort of a number.

I would like to maintain a temperature of 76F to 78F, 24/7, and plan to use air conditioning to do this. The idea of a concrete ceiling that is well insulated, is to add a heat sink that will hold my cold at a constant level. With a concrete block wall covered with 2 inches of foam insulation, that should keep out the heat and hold in the cold. Am I wrong in my thinking? In south Mississippi, houses are built with an insulation factor of R-13 in the walls and R-30 or more on the ceiling. My thought is to use the concrete to hold the cold in.

Thanks

[MaximumSecurity]

I am not a builder but have tackled this problem in several locations around the world. From your diagram, it looks like you will be trapping the heat absorbed by the sides of the house below the concrete planking ceiling. Instead you want the heat from the house itself to be able to travel freely up into the raised roof and out the vent on top. The insulation should go on the insides of the roof and walls to prevent heat transfer into the house during the day.

You can put photovoltaic driven exhaust fans in the peaks at each end/corner of the roof that will blow the hot air out all day. The more sunshine they get, the faster they blow.

Another possibility is to put 10cm pvc pipes vertically in the corners of the house with small fans at each end that suck the cooler air from the floor up to the ceiling where it is blown out and cools the hotter air at ceiling level. Air movement is important in cooling.

Be sure to plant bushes and trees to keep direct sunlight off the house. Use the lightest color roofing you can find. There are roof "paints" available to coat the roof and reflect even more heat. If you can afford it, install double glazed gas filled windows and patio door with the darkest tinting you can find. If not, get in the habit of opening and closing windows and curtains to maximize cool air coming in and hot air staying out depending on the position of the sun.

If you do have a/c be sure to build something to keep the sun off of it. That can save as much as 30% of the electricity usage.

[Naam]

Rimmer-- single wythe of Q Con bricks for the walls?

I used 2 x 7.5 mm Q Con with a 7.5mm space in the middle but you can buy Q Con in 7.5mm. 15mm or 20mm if you don't want the bother of making a cavity. Insulation and sound proofing excellent.

I do however have some single 7.5mm Q Con walls that get the sun all day and even those do not get warm on the inside.

i guess that all your "mm" are "cm".

[Naam]

Another possibility is to put 10cm pvc pipes vertically in the corners of the house with small fans at each end that suck the cooler air from the floor up to the ceiling where it is blown out and cools the hotter air at ceiling level.

? ?

[Rimmer]

Rimmer-- single wythe of Q Con bricks for the walls?

I used 2 x 7.5 mm Q Con with a 7.5mm space in the middle but you can buy Q Con in 7.5mm. 15mm or 20mm if you don't want the bother of making a cavity. Insulation and sound proofing excellent.

I do however have some single 7.5mm Q Con walls that get the sun all day and even those do not get warm on the inside.

i guess that all your "mm" are "cm".

They are indeed but then I still think in inches so maybe they are some of those in there as well

[Rimmer]

Rimmer- I would like to know what temperature you consider a meat locker and a freezer to be. Not trying to be a smart a*s, but would like some sort of a number.

I would like to maintain a temperature of 76F to 78F, 24/7, and plan to use air conditioning to do this. The idea of a concrete ceiling that is well insulated, is to add a heat sink that will hold my cold at a constant level. With a concrete block wall covered with 2 inches of foam insulation, that should keep out the heat and hold in the cold. Am I wrong in my thinking? In south Mississippi, houses are built with an insulation factor of R-13 in the walls and R-30 or more on the ceiling. My thought is to use the concrete to hold the cold in.

Thanks

When we had the cold spell it was too cold to walk on the floor without socks on, so cold my cat's hopped from chair to

chair !

Temperature right now mid day sun no air con in the house is 77 degrees, maybe during April it will reach 80 during the day but cools off quickly at night because of the big high ceiling and roof vents. Q Con block is aeriated concrete it is probably better that straight concrete blocks and foam. You will also get condensation with foam.

Friend walked through the door two days back and said it's cold in here do you have the air con on? Don't have air con...

A concrete ceiling is a second floor by another name right? The trick is to use the rising heat to suck out warm air while the cold air falls. I don't have a ceiling as such just a very high vaulted ceiling/roof with imitation wood beams across it.

At the risk of being boring again maybe you can see the general idea on the second picture at http://www.flickr.com/photos/banjopicker/page4/

[Artisi]

Hi Rimmer;

I have sent a private message to you - trust this is Ok.

[Naam]

The idea of a concrete ceiling that is well insulated, is to add a heat sink that will hold my cold at a constant level. With a concrete block wall covered with 2 inches of foam insulation, that should keep out the heat and hold in the cold. Am I wrong in my thinking?

yes BillyBob, your thinking is indeed wrong as far as the heat-sink that "holds the cold" is concerned. the outside insulation is a good idea but you won't find a builder who can attach the insulation and stucco over it. if you want to insulate your house then take Rimmer's advice and build double walls. but make sure that the the airgap on top of the walls is closed. before i built my house i talked to several builders who claimed they do double walls all the time but had no idea that the airgap has hardly any r-value if the air can move. ideal would be double outside walls and the gap filled with insulation.

another not exactly brilliant idea are the concrete walls. but that's a different story.

[Naam]

Q Con block is aeriated concrete it is probably better that straight concrete blocks and foam. You will also get condensation with foam.

looking at one of your pictures i don't see any aerated but quite common hollow cement/sand concrete blocks Rimmer

http://www.flickr.com/photos/banjopicker/309477339/

[longball53098]

This view looks like Q-con

Block

[Rimmer]

Q Con block is aeriated concrete it is probably better that straight concrete blocks and foam. You will also get condensation with foam.

looking at one of your pictures i don't see any aerated but quite common hollow cement/sand concrete blocks Rimmer

http://www.flickr.com/photos/banjopicker/309477339/

Oh OK if you insist

[Rimmer]

One more double wall shot North west facing wall.

[Rimmer]

Q Con block is aeriated concrete it is probably better that straight concrete blocks and foam. You will also get condensation with foam.

looking at one of your pictures i don't see any aerated but quite common hollow cement/sand concrete blocks Rimmer

http://www.flickr.com/photos/banjopicker/309477339/

We used those blocks for the perimiter wall and to break down for hard core under pathways. That's all they are any good for.

[JimmyGreaves]

Rimmer.

I am thinking of doing the same cavity on my outside walls using cpac aac or qcon blocks. To try and save on the cost of build I am thinking of putting normal blocks on the interior walls. Do you think I will have any problems where the two diffent type of blocks join?

[Rimmer]

Rimmer.

I am thinking of doing the same cavity on my outside walls using cpac aac or qcon blocks. To try and save on the cost of build I am thinking of putting normal blocks on the interior walls. Do you think I will have any problems where the two diffent type of blocks join?

You can indeed use normal blocks on the inside layer of the cavity, also nothing wrong with using them as inside walls as well, they are around three to five baht each only. Cinder blocks use cement to stick them together but Q Con uses glue.

But I can't see a situation where the two types of block would actually join though

The downside is that would loose a little on the insulation but my guess not much. Only other thing I can think of which may be important to you is that the inside walls are not nearly as soundproof.

You could also use the slightly bigger Q Con 15 cm blocks at 39 baht each vs 19.5 baht for 7.5 cm block. My guess is that if you work it out one will equal the other because you will save the difference on labor cost by using the bigger block.

Be aware though that a typical sow poon is 20 cm square so a 15 cm block will give you those funky corners. Of course If the house is not two story it is still quite OK to use 15 cm sow poons (Concrete corner posts) then the 15 cm blocks will fit perfectly.

[JimmyGreaves]

Sorry Rimmer didn't make myself clear.

The two layers forming the cavity will be qcon and it is 2 storey. The partition of room walls I am thinking of cinder. Just wondering about when they meet each other what to use glue or mortar and if I will be liable to craking on the joins.

[Naam]

You could also use the slightly bigger Q Con 15 cm blocks at 39 baht each vs 19.5 baht for 7.5 cm block. My guess is that if you work it out one will equal the other because you will save the difference on labor cost by using the bigger block.

Be aware though that a typical sow poon is 20 cm square so a 15 cm block will give you those funky corners. Of course If the house is not two story it is still quite OK to use 15 cm sow poons (Concrete corner posts) then the 15 cm blocks will fit perfectly.

a question Rimmer. the concrete pillars of my home are all 20cm and i used 20cm thick as i didn't trust the builder with double walls. do you have any hairline cracks where the blocks meet the concrete pillars? i had them several times and attributed them to a quite normal settling procedure. but this is now the third year they turn up again. i therefore conclude that not settling causes the cracks but the different expansion/contraction factor of Q-con and concrete. will have the crack repaired now with an elastic instead of a brittle medium. opinions?

[Rimmer]

Sorry Rimmer didn't make myself clear.

The two layers forming the cavity will be qcon and it is 2 storey. The partition of room walls I am thinking of cinder. Just wondering about when they meet each other what to use glue or mortar and if I will be liable to craking on the joins.

Wall corners are normally joined at a sow poon but if you have to butt cinder block to Q Con you will have to use cement mortar with appropriate ties into the Q Con. Use the Q Con mesh plates.

[Rimmer]

You could also use the slightly bigger Q Con 15 cm blocks at 39 baht each vs 19.5 baht for 7.5 cm block. My guess is that if you work it out one will equal the other because you will save the difference on labor cost by using the bigger block.

Be aware though that a typical sow poon is 20 cm square so a 15 cm block will give you those funky corners. Of course If the house is not two story it is still quite OK to use 15 cm sow poons (Concrete corner posts) then the 15 cm blocks will fit perfectly.

a question Rimmer. the concrete pillars of my home are all 20cm and i used 20cm thick as i didn't trust the builder with double walls. do you have any hairline cracks where the blocks meet the concrete pillars? i had them several times and attributed them to a quite normal settling procedure. but this is now the third year they turn up again. i therefore conclude that not settling causes the cracks but the different expansion/contraction factor of Q-con and concrete. will have the crack repaired now with an elastic instead of a brittle medium. opinions?

Q Con offer a mesh plate that you are supposed to put over any concrete to Q Con joints I suspect that is the answer to your question. I have just one place with a crack such as you describe. It is certainly a thought about the different expansion rates of concrete and Q Con. The answer is I really don't have an answer

With my one crack in mind I was browsing the paint section at Global House for crack covering paints and I found the following manufacturers do crack covering paint.

Berger Elastomer 1341 per can

Nissan Vinalux 1555 per can

Nissan Vinalux 2530 per can different texture from above.

TOA Elastometric 7 in 1 1095 per can

TOA HP Elastometric 2490 per can

per can is not the BIG can it's the one size under it duh.

[Swelters]

I will be building a small house, 100 sq. meter, later this year 50 km south of Pichit.

I want this house to hold as much cold as I generate each day as possible. I have read through all of the postings in this forum , and not seen any that address the design that I plan to use. Being from the south of Mississippi in the U.S. , I am used to the heat. I have seen this design used on many commercial buildings that do not use air conditioning. My intent is to passively remove as much heat as possible. It does not matter to me if the local people see my design as weird.

I would like to hear from others on the design.

Thanks to all.

Sure, if you want to leave your air conditioner on all day. But if you don't, say you want to go to the beach for the day, when you come back you've got a hot, heavy solar heated box and your air conditioner is going to work half the night cooling the thing down.

Try light construction, as the man says.

Swelters

[BillyBobThai]

Swelters I do understand about using light construction. My air conditioner will be running 24/7 which is why I wanted to put up a concrete ceiling. My wife sleeps under

3 covers and I sleep with out any. I once lived in a 2 story house built in 1826 in Mississippi. The exterior walls were brick, 7 to 8 inches thick, with stucco on the inside.

O the second floor where I slept, in the summer, it was allways cooler outside at night. It took several of those hand rolled things, to get to sleep.

Thanks again for the help.

[Swelters]

Swelters I do understand about using light construction. My air conditioner will be running 24/7 which is why I wanted to put up a concrete ceiling. My wife sleeps under

3 covers and I sleep with out any. I once lived in a 2 story house built in 1826 in Mississippi. The exterior walls were brick, 7 to 8 inches thick, with stucco on the inside.

O the second floor where I slept, in the summer, it was allways cooler outside at night. It took several of those hand rolled things, to get to sleep.

Thanks again for the help.

Man, I will tell you that I'll help anyone who leaves me happily wondering what a hand rolled thing is, even if they lived in a hot house from the days of Huck Finn.

Swelters

[BillyBobThai]

Man, I will tell you that I'll help anyone who leaves me happily wondering what a hand rolled thing is, even if they lived in a hot house from the days of Huck Finn.

Swelters

Like one of my former presidents, I never inhaled. Come to think of it, he never had sex with that woman either.