How To Properly Insulate & Ventilate Double Block/Brick Walls

[doglover]

I have read alot of threads that start a discussion of this but never complete it. If one plans to have an air conditioned home utilizing double walls with a cavity for services plus possible insulation what is the best method of having it constructed. Here is a list of questions many people would like the correct answer to: (add more if I've missed yours)

1. Is it true that foam sheets or even spray in foam will end up having issues with water build up and mold if used inside of the cavity in walls built from bricks or blocks? If that is case are the only options to install the insulation on the exterior surfaces of the double wall. Which would be better - inside or outside house?
2. Does the aerated white block with an R value also allow moisture to leech through it?
3. Could a vapour/moisture barrier be utilized successfully to allow the insulation to be installed within the wall cavity without moisture reaching it?
4. What are the implications of using a double concrete block wall that has been sealed (using only concrete and stucco) with no insulation except trapped air? Is there any ideal gap for this space? Will mold build up and make transfer through the walls?
5. If ventilation is required what is the proper way to do this?
6. How about the exterior wall from block, brick or aerated block and the interior wall built from tin metal studs, batt insulation and gypsum board. Is this a better alternative in regards to sound and temperature insulation? Would a moisture barrier installed on the cavity side of this metal stud and gypsum wall protect the insulation and gypsum from moisture? Would a moisture barrier also be required between the gysum and the metal studs?

Now down to a raised concrete building foundation say 1 metre off the ground that will be walled in:

1. Should this be filled in with sand and concrete poured and tiled for flooring?
2. Or is it necessary or preferred to leave the sub-floor open and appropriately ventilate the space to remove moisture?
3. If it is an open space is it even necessary to ventilate it at all?

Alot of questions but I am not asking for an answer to each one from every poster, just answers in the area(s) they are sufficiently educated or experienced.

:jap:

[kamalabob2]

Good questions from the O.P. I can comment on

2. In the house built with CPAC brand 12.5 thick single wall Aerated white blocks for our exterior walls absolutely no moisture has come through any wall surfaces that I can see from inside the home. Granted both sides of the blocks have been coated with the recommended plaster / skim product, both sides of the wall surfaces were allowed to cure for weeks prior to primer with Dulux Super Primer and then painted with two coats of Dulux high grade paint. I can comment that these exterior wall blocks are much cooler in the hot season than the single wall red brick exterior walls in our former rental house. In this "cool season" it is not bitterly cold inside our current home, but in our former home it was very cold near the red brick walls.

Regarding a home first floor raised up one meter.

1- I would not fill in with any material, I would recommend you consider a "crawl space", especially under any water or waste pipes as they will leak at some point. Buried pipes are no fun in my observation. If you have a crawl space then you can consider a Termite spray pipe system that would be installed PRIOR to your ground floor being installed.

2- We have just over a one meter crawl space under our home and in fact on the advise of a plumber from Canada, we had a two meter access area dug under our first floor bathrooms with an access hole to make it easy to observe water or waste pipe conditions or for any repairs to such pipes.

3- It was easy and inexpensive for the builder to ventilate our crawl space area. The builder contracted a local window/screen/glass door firm to fabricate aluminum mesh ventilation covers for the ventilation points that were strong enough to prevent any critters from gaining access to under our home.

Other Thai Visa members may have valid and more experienced views on all your questions, but these were my experiences for a home completed in 2008 in Isaan, not near the Ocean.

Keep access of BIRDS into your attic as a genuine concern and the specific type of glue used to connect any PVC water pipes or waste pipes as a priority.

[doglover]

Thanks for the reply and great info kamalabob2. Quite the mansion you have there, very nice. Nice straight lines on your rows of blocks. I have actually completed my house already but I will renovate this house to address lack of insulation and ventilation issues that I was clueless about at the time I built. Or I will just start over again. At present time I live in a beautiful oven! I have double cement block walls with a minimalist gap between them 1-2cm as I caved under pressure to do this by the builder when I found some supporting positive info of a small air gap on the net about restricting air movement. I would have prefered to have the double wall extend to the far edges of the columns allowing straight lines on the interior walls and space in the cavity for services and future spray in insulation if recommended. I had this small space sealed with concrete and stucco at the top of the double wall. A proper curing time was allowed however there would have been moisture sealed in (not really sealed as there are bound to be cracks somewhere in the rough top section of wall that extends up into the attic) when this gap was closed and the second wall having just been completed. Half way through construction of this second wall I discovered the white aerated block! Too late. I also used high quality elastic sealing paints interior and exterior and do not have any surfaces cracks. Or there are small ones and the elastic paint is really just that. It has been almost 3 years and I still do not see or smell any mold issues but I worry it will only be a matter of time. I plan on carrying out some renovations on the interior and exterior. New flooring, painting, more trim installed, kitchen retrofit, more aircon units and installing siding on the exterior. (Yes I should have just done it right the first time!) So I will have to decide to leave the double block wall as is or break out the sledgehammer. So I want to ensure I get the wall right this time. I will cut open some small sections of the walls on the exterior prior to installing siding and check the condition of the little cavity between the walls prior to installing siding. And want to be armed with knowledge in the event of a nasty finding.

Your advice on the crawl space makes all kinds of sense and I will be installing some vents at one end of the house and drawing air into the space and out the the other end of the house with small 12v subfoor ventilation fans from Edmonds. My regret is that the top of the ground floor is not quite at the 1 metre mark and does not leave enough room under the horizontal columns (whatever they're called) to allow proper access. I will have to dig to get access for any inspection of water and sewer lines and to remove the termite colony! Also found out about termite control systems like yours after the fact. The sub-floor was not filled in and I will have to install a termite system after removing the present termite mounds. I just tell my story to help people who are unaware as I was to not make the mistakes I did. And also to figure out how to correctly correct the situation.

Just to add a tidbit from another thread that I found informative. If you are going to insulate your attic with batts of insulation, spray in or on insulation, etc. on top of your gypsum ceiling. Be sure to insulate the sections of walls (more so for standard brick or block) that protrude up into the attic as the heat will makes its way into your living space through convection in the wall if left uninsulated.

Also should mention that my first shack was single wall concrete block and the double wall of concrete block in my now second house does keep the home much cooler than the single wall. But there is still much too be desired with no insulation in or around the walls. I believe most of the heat comes from the uninsulated ceiling and inadequate ventilation of the attic. But hopefully this discussion can stick to walls and sub-floor to completely cover the topic of proper construction of these important aspects. More experiences, advice and or opinions very welcome!

Edited January 12, 2011 by doglover

[PattayaParent]

Your number 4 is the way that most houses in UK are built.

ventilation is provided by not blocking over the top of the cavity wall.

You can put ventilation bricks in the lower courses about 150mm above ground level also, only a couple per wall are needed.

Can't remember the size of the cavity offhand but it's something simple, like based on the size of a trowel (so hairy arsed brickies don't have to bother with tape measures and other engineering instruments they don't understand how to use.)

[doglover]

I understand this construction method now. But I wasn't familiar with it when I built my house. Any idea what will happen if someone ignorant like me seals up that cavity between the walls allowing no ventilation into the space whatsoever? I assume mold but it would be better for me not to assume and hear from someone whom has been there and seen the result of this scenario.

....worked around enough brickies to get where you're coming from...lol

(have only installed conduit in single wall block construction in Canada however)

Edited January 12, 2011 by doglover

[Naam]

Your number 4 is the way that most houses in UK are built.

ventilation is provided by not blocking over the top of the cavity wall.

You can put ventilation bricks in the lower courses about 150mm above ground level also, only a couple per wall are needed.

Can't remember the size of the cavity offhand but it's something simple, like based on the size of a trowel (so hairy arsed brickies don't have to bother with tape measures and other engineering instruments they don't understand how to use.)

thus reducing the insulation factor of a double wall by 85%!

[bbradsby]

Good questions! See my responses in bold italics.

-bbradsby

bdb/a

• • Is it true that foam sheets or even spray in foam will end up having issues with water build up and mold if used inside of the cavity in walls built from bricks or blocks? If that is case are the only options to install the insulation on the exterior surfaces of the double wall. Which would be better - inside or outside house? Vapor barriers are to be installed on the warm side of an assembly (wall/ceiling/floor), and should not be waterproof membranes as they need to breathe at the molecular level to release vapor pressure while keeping water from passing through. If installed on the cold side, they form a very effective condensation surface (think a cold glass of ice tea on the Sala in 33 degree heat) and create dampness, mold & mildew in the building envelope and/or interior space. Proper analysis, design & material specification are key!
  • Does the aerated white block with an R value also allow moisture to leech through it? It's concrete, so it passes moisture easily via capillary action. A properly spec'd membrane is required to stave off moisture infiltration into the building envelope.
  • Could a vapour/moisture barrier be utilized successfully to allow the insulation to be installed within the wall cavity without moisture reaching it? Yes- see above comments.
  • What are the implications of using a double concrete block wall that has been sealed (using only concrete and stucco) with no insulation except trapped air? Is there any ideal gap for this space? Will mold build up and make transfer through the walls? Concrete & stucco don't 'seal' a block or masonry wall from moisture passage, only slow it a bit... if there are no cracks. Further, one or two layers of block won't make a huge difference if you don't protect them from sun exposure. The air gap breaks the thermal bridge for conducted heat, but is not a effective insulator. Cost-benefit-wise, it's better to use a single wythe of block, keep the wall out of the sun, and insulate.
  • If ventilation is required what is the proper way to do this? WIth a breathable vapor barrier, or none, the normal air infiltration will 'air-out' the wall system effectively. No further wall system ventilation is required for a block wall.

• • How about the exterior wall from block, brick or aerated block and the interior wall built from tin metal studs, batt insulation and gypsum board. Is this a better alternative in regards to sound and temperature insulation? Would a moisture barrier installed on the cavity side of this metal stud and gypsum wall protect the insulation and gypsum from moisture? Would a moisture barrier also be required between the gysum and the metal studs? Depends on your climate zone & temperature differential, so the system must be designed to respond properly. Wherever the air temperature reaches dew point, its moisture will condense. This would likely be at the outside face of your wall's insulation in coastal effect-dominated climate zones in Thailand. The result in S.E. Asian mountain zones' differing seasons may differ. Proper climate analysis & design are key!

Now down to a raised concrete building foundation say 1 metre off the ground that will be walled in:

• Should this be filled in with sand and concrete poured and tiled for flooring?
  Either is OK for concrete floor system. Raised wood structures cool quickly, but a shaded mass of concrete in direct ground contact is an effective heat sink - just ask your bare feet! Slab on grade is also much cheaper than an elevated slab. Install a 6-12mil poly vapor barrier directly under the slab & over a 5cm sand bed to stop rising moisture. If using a concrete structure, I'd only raise the floor if there are flood concerns at your site.
• Or is it necessary or preferred to leave the sub-floor open and appropriately ventilate the space to remove moisture?
  If elevated & not filled, air must be able to circulate through the cavity/crawlspace.
• If it is an open space is it even necessary to ventilate it at all?
  Again, i
  f elevated
  & not filled,
  air must be able to circulate through the cavity/crawlspace.

Alot of questions but I am not asking for an answer to each one from every poster, just answers in the area(s) they are sufficiently educated or experienced.

I'm an architect & construction manager with several decades' experience, just to answer your question. Best of luck with your project and let us know what direction you go on the above issues!

Edited January 18, 2011 by bbradsby

[doglover]

Thank you bbradsby for bringing your education and experience to this thread and taking the time to address my long list of questions. I still remain confused on some points and if you could elaborate on them it would be much appreciated. Also, it is my intention that this thread explain this subject to an extent that a typical homeowner has enough knowledge to perform his own general contracting and not require the services of an architect or construction co-ordinator (no offence). Some of your answers are a little elusive and still require further explanation (for myself). If this is a conlict of interest for you, as in the case of trying to garner clients, I would expect no further explanation.

If you could "dumb it down" somewhat into a generalized double wall building concept for Thailand it would be greatly appreciated.

-Is this poly vapour barrier simply a roll of really thick plastic?

-Can you clarify a list of materials for the double (or single) wall? Say from exterior to interior.....example:

• rendering or stucco
• stucco wire
• 2" thick sheets of styrofoam insulation
• vapour barrier from rolls of plastic
• outside whythe of aerated concrete block
• 3" air gap (unventilated)
• inside whythe of aerated concrete block
• rendering or stucco

Expensive example!

I found your responses on the sub-floor easy to follow and I have no questions there.

[doglover]

(This is from some emails with another TV member that allowed me to copy into this thread....)

There are two or three manufacturers of lightweight 'autoclaved' blocks in Thailand now. They use them a lot in the newer constructions.

Q-Con are based on the Bang-Pa-In Industrical estate joust north of Bangkok, after Rang Sit. You can order and buy direct from the factory and they will deliver for additional fee. Cut out the middle man. They also can supply

to any thickness. The common one being 100mm (4") then 150mm (6"), but they will make thicker and can also pre-fabricate very large sections to order. They have a good display at their premises.

Cavity walls are mandatory as per the building regulations where I originally come from in the UK. I think most of northern Europe has similar.

here are two main resons for the cavity wall. Firstly, damp proofing. Water penetrates the outer 'skin' by capiliary action then runs down the inner surface and evaporates inside the cavity, thus preventing damp from penetrating

through to the inside of the inner 'skin' and stopping mould. Of course, a damp-proof course should always be used above ground (but below floor) level. Damp proof courses are usually bitumen layer/sheet or can be painted

bitumen onto the top of your base course - you do this on both skins, the continue the damp proofing with a membrane over the entire floor - this prevents damp from rising and keeps it below the structure. Most building

materials will act as a 'wick' and damp will penetrate after a few years through nearly everything (including concrete) except 'vitreous' materials - like granite, etc.

By the way, older buildings (100 years or more) used a thin layer of slate laid on top of the base course as dampproofing - if done properly this also works.

Ventilating the cavity was not always done in the UK but in newer buildings it is. There are a number of means to do this. The first is air-bricks. These were seen in the outer skin below damp proof course level but above the

ground and out of the water. They are standard size bricks with holes made into them. Another method was to leave every fourth or fifth vertical joint empty with no mortar, again below damp proof course level.

What worries me about air bricks and other such ventilation in Thailand is two things. First, you're using blocks and so even if you could get air bricks they would be about 9 times too small. You could always inprovise. The

second thing is that by trying to do the right thing, you are making a pathway for all kinds of nasty creatures to come and make a home in the cavity. I don't know the answer to this one. Myself, I would probably seal the cavith

and hope that any moisture would find its way back outside by diffusion through the outer skin. This would happen naturally if the humidity of the air outside was lower than that within the outer skin - which is likely.

Cavities can be between 25mm and 75mm. 50mm (2") is common. Remember the two skins (sometimes called 'leaves') have to be connected every so often by a 'wall tie'. These brace the two skins together so that they share

the load between them and it stops 'bellying' of one or other of the skins. Wall ties are put in during brick laying (or block laying). You normally put one across the two skins as you build them up simultaneously, say one tie

every 6 bricks. The next course you place a tie between those of the previous course, so that they are staggered. Actually, with bricks you don't need to use every course or you will use a lot of wall ties. Wall ties were made of

carbon steel and galvanised for corrosion protection. Nowadays, if you have money, you can get stainless steel ties. A few of the lder buildings in the UK are suffering from wall tie corrosion. When the ties goes, then sections

of the wall can bulge outward due to lack of lateral support. You see traditionally the load of joists and roof was taken by the inner skin and the outer skin braced (via wall ties) to it.

Personally, I don't think damp is such a problem in Thailand because of the higher air temperatures, but it still exists. My reason for a cavity wall would be to keep the inside of the house cooler (the reverse of using them in the

UK) and for sound insulation. I really don't think a 4" thick foam block can be used in the traditional way (i.e. with no concrete columns as they build in Thailand) as a load-bearing wall. There is a chance of bellying and

collapse and their crushing strength is too low. Normally they are used as in-fill panels where the reinforced concrete frame post method is used - not my favourite. If it was me, I would use 6" blocks as load bearing for the

inner skin (more stable) and 4" for the outer (non-load bearing skin) since this is there for thermal and sound benefits only.

Oh yes, they don't take point-loads too well, such as joists resting on their surface. So you build up to about a foot below where your joists are going and put in three courses of high strength bricks - lay the joists on these -

then carry on up with the 6" blocks.

What I've been talking about here is the traditional method of building - without the concrete posts and lintels as is usual in Thailand. There's nothing wrong with using a hybrid sort of concept, which should make for a rigid

strong structure.

There's a lot more to it than this of course. There are a l,ot of good books available, in Thailand I'm not so sure, but maybe on the Internet. The UK building regulations cover it quite well, and there are books which provide

good illustrations.

One last thing about the foam blocks. You can get a cement type adhesive, which is what they use most. Usually a very thin bed is used, and since the blocks are all very accurately made, it works okay. So they technique of

laying them is not as you would use for normal brick/blocks, with a thick bed that allows a bit of adjustment of each block. Personally I don't like this and prefer to use a normal bed of mortar - 5 to 7mm thick. These blocks

tend not to stick when you use this method. To make it work you have to soak the blocks in water until ready to use, take them out of the water a minute or so before you use them. This way they get good adhesion and you

don't get a 'dry' joint with the block becoming loose when the mortar has gone off. The same goes when rendering them after. A good soaking with a hose, then get your render on quickly. You can even use a 50/50 solution

of PVA adhesive painted on the surface before rendering, then trowel on your render before the glue goes too tacky. That way the render will never spall off in a few years.

All the above sounds a lot, but you have to ask yourself - what kind of a bulding do you want to end up with? If you want to save money initially, go for the Thai style construction and regret it later. If you build a cavity wall with

Q-Cons, expect a significant reduction in Air Conditioning bills. Also, you won't get woken up at 5 am when Somchai drives his truck with the boom box on the back touting the latest marvel on sale at Tesco Lotus.

Don't forget double glazing units. You gain a lot of heat (and noise) through the windows.

[doglover]

Your number 4 is the way that most houses in UK are built.

ventilation is provided by not blocking over the top of the cavity wall.

You can put ventilation bricks in the lower courses about 150mm above ground level also, only a couple per wall are needed.

Can't remember the size of the cavity offhand but it's something simple, like based on the size of a trowel (so hairy arsed brickies don't have to bother with tape measures and other engineering instruments they don't understand how to use.)

thus reducing the insulation factor of a double wall by 85%!

Maybe I'm not so ignorant afterall... From reading your posts in other threads I understand that you built double exterior walls from aerated concrete blocks with a sealed cavity between them. Did you use any sort of vapour/moisture barrier anywhere in your walls or floors Naam? Did you still build with load bearing concrete columns and fill in the walls between them or did you build a load bearing wall as another poster suggested?

Edited January 23, 2011 by doglover

[bbradsby]

Thank you bbradsby for bringing your education and experience to this thread and taking the time to address my long list of questions. I still remain confused on some points and if you could elaborate on them it would be much appreciated. Also, it is my intention that this thread explain this subject to an extent that a typical homeowner has enough knowledge to perform his own general contracting and not require the services of an architect or construction co-ordinator (no offence). Some of your answers are a little elusive and still require further explanation (for myself). If this is a conlict of interest for you, as in the case of trying to garner clients, I would expect no further explanation.

If you could "dumb it down" somewhat into a generalized double wall building concept for Thailand it would be greatly appreciated.

-Is this poly vapour barrier simply a roll of really thick plastic?

-Can you clarify a list of materials for the double (or single) wall? Say from exterior to interior.....example:

• rendering or stucco
• stucco wire
• 2" thick sheets of styrofoam insulation
• vapour barrier from rolls of plastic
• outside whythe of aerated concrete block
• 3" air gap (unventilated)
• inside whythe of aerated concrete block
• rendering or stucco

Expensive example!

I found your responses on the sub-floor easy to follow and I have no questions there.

Oops, just checking back in after a few days out & about! Cheers & happy to join in the shared knowledge of the TV group. It's clear many here have built professionally.

Not meaning in my post to be elusive. Since building system mistakes are expensive, I just want to help self-builders to not apply too general an approach to situations which may require a bit more analysis of the forces (i.e., water & water vapor migration, site micro-climate, thermodynamics...) at play so they can determine a proper course of design-construction for their projects and have a successful outcome.

When employing building systems [concrete floors/walls/tile roofs] starkly different from the locals' Timeless Way of Building (great book, BTW) which have evolved in response to climate over the generations, a methodical approach is required. With a high thermal mass component such as concrete, in a tropical environment, caution is advised when thinking about building up an assembly for sound or thermal insulation since condensation within the assembly is a risk. Using your choice of materials, and assuming a tropical, coastal influenced climate versus a Thai mountain climate, here's what you could do, and be aware you'll likely find no Thais who have built this assembly:

• rendering or stucco; 2 to 2.5cm 3-part cement plaster & lathe w/ the lathe nailed or screwed to exterior grade wood battens - see below;
• vapour barrier from rolls of asphalt-impregnated building paper (if you have to use plastic, may be ok, but don't tape the seams else you may trap vapor in the assembly. It should shed water like a duck, but still breathe); nail/screw to wood battens/nailers;
• exterior wood nailers, 60cm on center 'shot' into, or securely affixed to, the concrete block
• 1" to 1.5" thick sheets of styrofoam insulation epoxied to the block substrate between the wood nailers. YOur 2" is excessive since the temperature differential (Delta-T) from say 35 deg. C to a conditioned interior design temp of 22 deg C is relatively slight compared to fighting off a winter where Delta-T can be huge!
• outside whythe of aerated concrete block
• 3" air gap (unventilated) - superfluous, not required. cavity walls are a cold climate response, pre-dating proper insulating technologies, that worked fine til modern aircon & sealed wall assemblies started to create condensation inside them... mold! Will they work here? IMHO the Bang-per-Baht isn't optimal for a double wall CMU system, as CMU isn't a good insulator, and cavities are mold hazards in a CMU-wood and/or gypsum board composite assembly. Remember that water condenses at the surface where dew point occurs (see a glass of iced tea). In a tropical climate, place insulation on the outside of your wall.
• inside whythe of aerated concrete block - not required.
• rendering or stucco; typical Thai interior plaster/rendering, painted. wallpaper & its glue are potential mold farms.

Not to discourage anyone... but, the above is assuming you have some Western building experience in your tool belt, as not all details [nail spec/spacing, affixing wood to CMU...] are covered else this'd be a textbook. Total neophytes can do their own construction... but do the requisite homework, be OK with likely inferior visuals of the finished product and a slow process. they should really ask themselves whether the time-risk-reward quotient is worth it versus what money they could make in the same amount of time in their area of expertise.

If you have to go cheap & DIY, just use micro-fibre entrained plaster on chicken wire (to minimize cracking) over single-wythe Q-Con block. But... exterior paint to be elastomeric for water & hairline crack bridging... AND keep the sun off your walls with proper building orientation & overhangs and use landscaping to create exterior shading. Keep the sun from loading thermal energy into your building envelope and you'll not have to fight it all night with sweat or A/C

Many paths through the woods. Enjoy yours!

Edited January 23, 2011 by bbradsby

[doglover]

The response I've been waiting for... Thank you very much Mr. Bradsby! Your education and experience will be a great asset in this forum. Of course if someone can trump your response it is welcomed. But I won't hold my breath....:jap:

[bbradsby]

The response I've been waiting for... Thank you very much Mr. Bradsby! Your education and experience will be a great asset in this forum. Of course if someone can trump your response it is welcomed. But I won't hold my breath....:jap:

Thanks, but someone could easily have a good, completely different building solution - many paths are explored in building envelope design. Main thing is that it is a rational response to the project & site-specific criteria, to put in its most general terms.

[Naam]

Maybe I'm not so ignorant afterall... From reading your posts in other threads I understand that you built double exterior walls from aerated concrete blocks with a sealed cavity between them. Did you use any sort of vapour/moisture barrier anywhere in your walls or floors Naam? Did you still build with load bearing concrete columns and fill in the walls between them or did you build a load bearing wall as another poster suggested?

-moisture barrier only floors.

-two rather short load bearing walls because i did not want concrete columns in these areas (niches) and because the span (width) of the house is nearly 26 meters. otherwise the typical thai construction with a zillion concrete columns. however, i made sure that all walls reached the steel roof structure.

-no moisture anywhere even though my house is continously fully airconditioned with a delta t of up to 10ºC during the hot months and a daily several hours lasting delta t in the master bedroom of up to 18ºC. naturally i have provided a few inspection access holes to check on potential moisture of the outside walls.

i had however moisture problems on some parts of the walls but outside because the drainage around the house was done style which could not be rectified due to existing water pipes and (pissed off and nerve wrecked me) looking for an easy and fast solution. problem was solved by adding a skirting of ceramic tiles, respectively marble.

[Naam]

Raised wood structures cool quickly, but a shaded mass of concrete in direct ground contact is an effective heat sink - just ask your bare feet! Slab on grade is also much cheaper than an elevated slab. Install a 6-12mil poly vapor barrier directly under the slab & over a 5cm sand bed to stop rising moisture. If using a concrete structure, I'd only raise the floor if there are flood concerns at your site.

HA! finally somebody agrees with me that the local perception "raise your home and will be cooler" is

[Naam]

1. If you want to save money initially, go for the Thai style construction and regret it later.

2. If you build a cavity wall with Q-Cons, expect a significant reduction in Air Conditioning bills.

3. Also, you won't get woken up at 5 am when Somchai drives his truck with the boom box on the back touting the latest marvel on sale at Tesco Lotus.

1. correct

2. correct

3. unfortunately the best double or triple glazed windows and cavity walls with aerated blocks do not protect from noise which is transferred via roof tiles, steel roof construction and ceiling suspension fixed to roof structure. in my case the gypsum ceilings are working like amplifiers especially as far as low frequency outside noise is concerned

[doglover]

Maybe I'm not so ignorant afterall... From reading your posts in other threads I understand that you built double exterior walls from aerated concrete blocks with a sealed cavity between them. Did you use any sort of vapour/moisture barrier anywhere in your walls or floors Naam? Did you still build with load bearing concrete columns and fill in the walls between them or did you build a load bearing wall as another poster suggested?

-moisture barrier only floors.

-two rather short load bearing walls because i did not want concrete columns in these areas (niches) and because the span (width) of the house is nearly 26 meters. otherwise the typical thai construction with a zillion concrete columns. however, i made sure that all walls reached the steel roof structure.

-no moisture anywhere even though my house is continously fully airconditioned with a delta t of up to 10ºC during the hot months and a daily several hours lasting delta t in the master bedroom of up to 18ºC. naturally i have provided a few inspection access holes to check on potential moisture of the outside walls.

i had however moisture problems on some parts of the walls but outside because the drainage around the house was done style which could not be rectified due to existing water pipes and (pissed off and nerve wrecked me) looking for an easy and fast solution. problem was solved by adding a skirting of ceramic tiles, respectively marble.

Interesting. So it could be as the another poster suggested that any moisture that does build up in the walls during high humidity periods will find it's way out of the cavity during dryer times of the year. Although, as bbradby mentioned, it may be more cost effective to go with the single wall and insulate the exterior. Also would give a higher R value with his suggested system. But it is good to hear that a cavity wall will not necessarily be a mold cesspit.

[doglover]

1. If you want to save money initially, go for the Thai style construction and regret it later.

2. If you build a cavity wall with Q-Cons, expect a significant reduction in Air Conditioning bills.

3. Also, you won't get woken up at 5 am when Somchai drives his truck with the boom box on the back touting the latest marvel on sale at Tesco Lotus.

1. correct

2. correct

3. unfortunately the best double or triple glazed windows and cavity walls with aerated blocks do not protect from noise which is transferred via roof tiles, steel roof construction and ceiling suspension fixed to roof structure. in my case the gypsum ceilings are working like amplifiers especially as far as low frequency outside noise is concerned

#2 - Of course your statement is true. Yet, to be on the safe side, the exterior walls could be built from a single whythe of 25 - 30 cm wide aerated block. Not as effective as a dual wall of similar thickness of block with an air cavity, yet still effective. And peace of mind that there cannot be any problematic issues that could be associated with a wall cavity. Too contradict my last post, supporting bbradsby's concept... Back when I was building my house I intended to line one of the wall faces within the cavity with styrofoam sheets. The building supply shops did not carry it and the only place I could find styrofoam sheets was in the large stationary stores. The owner of one shop had large fish aquariums with a layer of white styrofoam sheets laying between the stand and the aqaurium. He was in the process of replacing the styrofoam as ants had made nests within this foam layer (the best of 3 qaulity/insulation grades). They chewed tunnels and rooms all throughout. The thought of having massive ant colonies in my walls stopped me from purchasing (although ants and termites could still make a home in the cavity regardless). I now know that insulation within the cavity is not such a good idea either as it will hinder the cavity from breathing. So with bbradsby's wall concept, with a crack in the stucco, ants could make a nice home within the styrofoam layer of the wall.

Thanks for the #3. I didn't even think of that. As sound insulation is also high on my list of desirables. Possibly a layer of that acoustiblock product installed prior to the gypsum would help. Probably only marginally as everything is still tied together as you mentioned. And sound insulation works best having an air gap in the setup (another goal scored for cavities )And I can just imagine the gypsum installers trying to secure the gypsum blinded by the acoustiblock. Probably end up with a good 75% of the screws not making contact the supports. This could be the birth of a new thread.... Ceiling sound insulation methods...

[bbradsby]

Only mass efficiently attenuates low frequency noise. In resorts, we've hung three layers of 15mm gyp board on acoustic isolators (fancy springs, basically) in an entertainment lounge to isolate hotel guest rooms above. That's even with a concrete slab above the lounge ceiling!

Airport/urban traffic noise attenuation requires mass for low freq, and for the high freq use at least double (triple is better) glazed windows with thicker glass and about 20mm space between each glazing panel. Then add continuous, airtight sealant at all building cracks/wall penetrations & serious gasketing of the door leaves & window sashes.

[doglover]

Only mass efficiently attenuates low frequency noise. In resorts, we've hung three layers of 15mm gyp board on acoustic isolators (fancy springs, basically) in an entertainment lounge to isolate hotel guest rooms above. That's even with a concrete slab above the lounge ceiling!

Airport/urban traffic noise attenuation requires mass for low freq, and for the high freq use at least double (triple is better) glazed windows with thicker glass and about 20mm space between each glazing panel. Then add continuous, airtight sealant at all building cracks/wall penetrations & serious gasketing of the door leaves & window sashes.

Thanks Bruce. It's good to know how to deal with the different frequencies of noise and the areas to focus the effort of sound reduction on. I realize most of us won't be dealing with noise levels of this magnitude. So what I take from this is to not skimp on the thickness of the ceiling gypsum, for the average home owner.

[bbradsby]

Right, every bit of mass helps for low freq attenuation - the ridiculously thin ceiling gyp panels used by Thai merchant builders would come crashing down if a cat got up there and started padding about not much of a fire barrier either...

Which brings up my favorite Off-Topic Harp: look above your top floor's ceiling if it's a townhouse. Make sure there are NO holes/vents/gaps through or at the perimeter of the property line wall (that separates your home from the next) in the attic. These would be a huge smoke & fire safety risk to you and yours if your neighbor's electrical fire came knocking at your property line. Similarly for apartment or condo walls & slabs separating dwelling units. These must be sealed completely airtight with non-flammable fire-stopping materials. For masonry wall holes/vents, use cement grout; for roof-to-wall gaps, stuff with fire-stopping mineral wool batts or spray-on fireproofing. And for some very cheap insurance: install smoke detectors in all bedrooms & at the top flight of stairs.

[bbradsby]

OK, replete with coffee buzz & some spare time, here's another acoustics thought:

There is a US product that basically glues two sheets of gyp board together with a non-hardening, flexible adhesive, possibly using a sealant (layman's term: caulk) , such that low frequency sound is absorbed by the resilient panel decoupled from the structure via the adhesive. It's a mass damper that absorbs the low freq sound energy which is trying to move the whole wall like a speaker diaphram. I've used this (in combo w/ a larger, holistic approach of course) in my hotel & resort remodels & upgrades since inter-room noise is the largest customer complaint in hotels, even as it can prove entertaining at times.

A creative type could possibly fashion something similar in LOS for a problem wall. Just do some homework to pick the right adhesive/sealant so the panel doesn't fall off! A ceiling... uh, don't try this at home, kids! or if you do, put it up on YouTube for our benefit

[doglover]

BB if I am so fortunate as to require an architect in LOS in the future you'll be my choice. I really appreciate the dedication you have to your career, it's very apparent.

*There you are Dr. Naam. Going to have to glue another layer of gypsum on your ceiling.....

[Naam]

BB if I am so fortunate as to require an architect in LOS in the future you'll be my choice. I really appreciate the dedication you have to your career, it's very apparent.

*There you are Dr. Naam. Going to have to glue another layer of gypsum on your ceiling.....

the thai gypsum chaps had huge problems to carry out my various tray ceilings and arches. it is something next to impossible now to do the same job again for the recommended "glue part". it was easier but not easy for them in my Florida house (thai house is nearly identical) because they just had to follow the framers who did an excellent job.

[klikster]

There is a US product that basically glues two sheets of gyp board together with a non-hardening, flexible adhesive, possibly using a sealant (layman's term: caulk) , such that low frequency sound is absorbed by the resilient panel decoupled from the structure via the adhesive. It's a mass damper that absorbs the low freq sound energy which is trying to move the whole wall like a speaker diaphram. I've used this (in combo w/ a larger, holistic approach of course) in my hotel & resort remodels & upgrades since inter-room noise is the largest customer complaint in hotels, even as it can prove entertaining at times.

I think that you will find that the sound is not "absorbed" by the caulked layer, but that the structure has beed detuned .. been made to not retransmit sound, ala the cone of a speaker. Generally, resonant cavities or porous / fibrous materials are used to prevent the reflection / reverberation of sound.

Other things to think about if you can find proper builder's solutions to install.

1 - very light gauge electrogalv steel sheet than has a layer of some visco-elastic mastic applied (painted on it). Something like "Henry's" may work. The best is something that never hardens 100%. If the composite can act as a separate sealed barrier with an air space above the gypsum. Maybe install as a suspended ceiling .. it need not be pretty.

2 - Same as above but using sheared pieces of steel sheet bonded directly to the gypsum by the mastic. The method is called "constrained layer damping". In constrained layer damping, 100% coverage is not required.

Sealing cracks is by far the most effective .. and cost effective method in reducing noise.

There are some great solutions available to the innovative builder who can think "out of the box". Mostly, builders don't understand sound attenuation except in common architectural acoustical treatments. Delve into solutions used by industrial acousticians and the industrial noise control industry.

Examples might include a sandwich of: gypsum panels, dense fiberglass, light gauge steel sheet with mastic. Or bond the steel to the gypsum panel, add the fiberglass bat and glue on a foil barrier. Seal the edges with fiberglass tape.

[cheeryble]

Raised wood structures cool quickly, but a shaded mass of concrete in direct ground contact is an effective heat sink - just ask your bare feet! Slab on grade is also much cheaper than an elevated slab. Install a 6-12mil poly vapor barrier directly under the slab & over a 5cm sand bed to stop rising moisture. If using a concrete structure, I'd only raise the floor if there are flood concerns at your site.

HA! finally somebody agrees with me that the local perception "raise your home and will be cooler" is

Generally speaking I agree with you about "stone floors" historically being a very practical heat sink.....we all know cathedrals or mosques feel cool when you walk in in hot countries. Likewise in a cold night they will tend to warm things a little. A good easy solution.

But if you're using aircon a big heat sink is not the optimum. You want to be cooling the least "heat mass" possible......so rather surface insulation that effectively reduces the sink. Something with an appropriate U value.

Like wood perhaps?

Likewise for walls if one is concerned about aercrete blocks lettinf damp through.....foam backed plasterboard (is this available here in LOS?) on regular blocks, so the effective heat sink is only the 12mm of plasterboard. Once it's cool that's it.

cheers Cheeryble

Edited March 6, 2011 by cheeryble

[cheeryble]

BTW I'd be interested in ideas for a related topic...........insulating a flat walkable concrete roof.

Can't get much past foam backed plasterboard lining the ceiling, which is why I asked in the last post if foam backed gyproc is available. I suppose one could put in a dropped ceiling and insulate it but it's a loss of height. With foam backed board one could nailgun or screw wood battens to the concrete ceiling then screw the boards directly up onto them.....thus also adding a small insulating air gap. (Never done it yet I might add but would like to build a large concrete roof soon)

cheers

[doglover]

BTW I'd be interested in ideas for a related topic...........insulating a flat walkable concrete roof.

Then maybe you should START a new topic called 'how to insulate a flat walkable concrete roof'!

Of which I would be an active reader as I find DIY topics rather interesting .

[bbradsby]

BB if I am so fortunate as to require an architect in LOS in the future you'll be my choice. I really appreciate the dedication you have to your career, it's very apparent.

*There you are Dr. Naam. Going to have to glue another layer of gypsum on your ceiling.....

Wow, sorry to have ignored your compliment, Doglover - I just now saw it!

Please note that the adhered system is recommended only for walls- not ceilings - unless you really trust your glue-job! For ceilings, I'd use two layers of 12mm min thickness gypsum - the first affixed to the structure above, and the second one screwed to resilient channels which act to de-couple the ceiling from the structure and thus attenuate the sound. I'd also line the cavity of the floor-ceiling assembly with ±4"/100mm of mineral wool batts.

But if you have a THX home theatre system owner with a rap/rambo fetish living above, you need to bring out the big guns... so to speak, to resolve these big problems with low freq from above. I'd use the three layers of gyp screwed to framing that is itself hung from acoustic isolators and an insulated cavity. But if its a big area, do it right and hire an acoustic engineer (klikster?) to run sound tests in situ & design to the frequencies & sources present. In any case you'd need an architect or engineer to check the loads and existing structure's capacities, then spec the fasteners, framing & detail it out. It's all solvable with good process, elbow grease & a few Baht

[bbradsby]

BTW I'd be interested in ideas for a related topic...........insulating a flat walkable concrete roof.

Then maybe you should START a new topic called 'how to insulate a flat walkable concrete roof'!

Of which I would be an active reader as I find DIY topics rather interesting .

maybe first Google low-slope insulated roof deck and/or tapered rigid roof insulation... then post away