How to insulate or reduce thermal bridging of metal trusses

EnlightenedAtheist · November 30, 2017

I am going to build a house for the first time in LOS and have a few questions. I searched and read related threads (roof insulation and construction) on TV, but nothing on thermal bridging and there is not much that I could find on the internet as metal trusses are not usually used in the West for houses. Lots of info on metal studs. Wood is an excellent insulators and so for wood rafters this is not usually a concern (except for condensation/rot). Bridging is a concern with metal studs, windows, concrete (balconies and uninsulated floor fascias,...). Metal rafters are more common for industrial buildings in the west and maybe some of you have seen how they insulate those. Maybe there is some information for those.

Many engineers and architects will almost never bring up the topic, but my brother is in the insulation of building business and he has spoken to me at length about thermal bridging (for steel studs, glass windows and the aluminium frames, and even concrete). Thermal bridging is when the heat/cold is conducted along a structure made out of concrete, brick, or metal unimpeded as there is no insulation and heat radiates (especially with concrete long after). Bridging can reduce significantly the insulation value of an assembly. Have you touched a hot piece of metal lately? How hot does it get if the heat is in the attic is high and they can get hot?

Please read some of the info here.

"Attics can reach temperatures of 150 to 160 degrees F during a summer day, although outside air temperatures are only 95 to 97 degrees F." (True, the roof might not have the best tiles and such.)

I realize you can mitigate heat in many ways, but even if you are able to limit the damage, here in Chiang Mai, there will be little wind in March to May. Side venting through soffits and gables will not work or work well. The pollution will mean you will want to close those windows. Sure you can use a/c. But, can we do better than this?

We know we can use white or reflective tiles, but don't they get dirty? They will and will lose their power by at least 25%. Are those tiles going to be cool (25 degrees)? I doubt it.

We can spray foam the under belly of the tiles or use alum. foil to reduce the heat too. Are those tiles going be at 25 degrees? It seems to me that the tiles are going to be hot and release that radiant heat unless your reflective foil has some very powerful R foam value. How much is the R value of those foam reflectors? Those tiles are going to be really hot.

Most people think of using passive venting using soffits, gables,... But, it seems to me that they would defeat the purpose as they would --at best-- bring the heat into the cavity. If positioned high in the cavity, they might allow heat to escape a little, as the heat in the cavity should be higher than outside temp. even with reflective material. Ridge vent should be more efficient at removing the extra heat, but they would at best keep the heat at outside temperature levels. We could use some mechanical ways to remove the heat such as fans (all the types), but, from what I read from the experts at Green building advisor apparently they might draw the a/c air into the cavity and cool the neighbourhood, even, and mess up drafting and such.

Questions

I am not too sure where they usually put the insulation (the fibreglass type)? Beside the joists inside the roof cavity? If so, bridging is happening, I would think. No?
Couldn't ALL of insulation be put to better use in a false ceiling and prevent any bridging from occurring? How much can it take? It looks like the standard size height of a room is 3 meters and a false ceiling is about 50 cm in height. The roof cavity would be hot.
Still, aren't some of those rafter pieces connected to the bricks, heating up the bricks as well? Couldn't closed cell foam not be placed between the steel joists and the concrete?
Are there not able to minimize the connections to the wall? I read you can raise the rafters?
Putting foam around the rafter members will help, but I read closed-cell foam would be more suited for that (and it might be expensive). Isn't there better ways to address this (As in packing all of the insulation in false ceiling? )
Wouldn't it be a good idea to use closed-cell foam where the ceiling panels are connected to the perimeter of the roof cavity?

Do you have any other idea, apart from shading the bricks below the roof shadow line created by the roof?

Btw, I realize we can use a/c and I realize that the cost of the solution should see decent ROI. I do not want to spend on something that will be more costly that a/c. I plan to live another 30 years in that house.

Edited November 30, 2017 by EnlightenedAtheist

EnlightenedAtheist · November 30, 2017

Btw, here is some info on temperature of a house that was well insulated from this well documented bulding project: http://<URL Automatically Removed>/construction-in-thailand/127055-newbie-build-chiang-mai-don-kaew-78.html. They still have to use A/C. Can we do better? And, then, later on the month, he mentions that it is getting hot even downstairs: http://<URL Automatically Removed>/construction-in-thailand/127055-newbie-build-chiang-mai-don-kaew-83.html#post3001945! That should not be happening.

Edited November 30, 2017 by EnlightenedAtheist

Artisi · November 30, 2017

Quite a complex question and as to the best answer, I along with most house owners / builders can give you heaps of info, some good, some bad, some useless.

My house has a steel frame with concrete tiles, aluminium foil under tiles and on top of the frame (standard method I would think), and aluminium foil encasing thermal blanket on top of the ceiling support frame. Gables are vented - nothing special, just slotted cement fibre board.

The house is double wall with cavity and rendered on both sides. single glass pane alum. frame windows etc. Each room has wall vents accessing into the cavity with the cavity open at the top venting into the roof space. Living area has 4 metre ceiling height with 3.5m in bedrooms etc.

Just a quick summary on the house, on the hottest days in Phitsanulok anything up to 40c+ with the house closed up and without any aircon running - max inside temp. might get to 30 / 31c after a few days of constant high temp.

I have not noted excessive heat thru the ceiling.

A few points to consider:

Excluding heat from the house works for and against you, any heat build up during the day has to be lost overnight - nearly impossible in P/lok- on extremely hot days the night temp. may not drop below 30c - so a very well insulated house is insulated in both directions and over a few days the inside ambient rises to something over the minimum overnight temp. - aircon helps of course and can help to drop the inside overnight (sometimes).

Hope this gives you a few things to think on and if you are not aware of the site www.coolthaihouse.com I suggest you have a browse . Look up "your build story" all the build projects are listed there - my own story is

Our house project Phitsanulok

by Ians » Fri Mar 11, 2011 9:06 pm

Kwasaki · November 30, 2017

10 hours ago, EnlightenedAtheist said:

Many engineers and architects will almost never bring up the topic

Mainly because it's a matter of course.

10 hours ago, EnlightenedAtheist said:

my brother is in the insulation of building business and he has spoken to me at length about thermal bridging (for steel studs, glass windows and the aluminium frames, and even concrete)

So why cannot your brother tell you what to do if you show him your house roof section drawings.

Just line the underside of the internal roof area leaving a gap at ridge for venting & vent your soffits.

RB seems to be the in thing at the moment.

Venting roof areas and using quality insulation on ceiling areas is another way.

EnlightenedAtheist · December 4, 2017

On 12/1/2017 at 6:34 AM, Kwasaki said:

Mainly because it's a matter of course.

So why cannot your brother tell you what to do if you show him your house roof section drawings.

Just line the underside of the internal roof area leaving a gap at ridge for venting & vent your soffits.

RB seems to be the in thing at the moment.

Venting roof areas and using quality insulation on ceiling areas is another way.

Thnaks! I was thinking the same way. Packing as much fibreglass as I can in the drop ceiling area. They say for noise a 15 cm air gap (for walls) between an additional 3" on either side of it and 2 dry wall sheets on either side of that (or a 25 cm wall area or so) is best for noise (and heat as well). In a ceiling, you have a huge air gap, which should be great, but there is reverberation that I plan to kill with foam under the tile type. I will have a 30 degree pitch metal roof with white colour. Gable vents with aluminium grill/slits in the direction of the prevailing winds and some soffit vents to drive the vent out even further.

I wish I could ask my brother now, but I have discovered since then I talked to him (3 years ago) that he withheld some information and have since understood that his ego is too big for my taste.

I do not think that a ridge vent is possible on metal sheet roofs, hence the gable vent. The metal sheets are not likely to be damaged or moved by wind. Sadly raised-seams types of metal roof are not readily available here, but the 30 degrees pitch should help preventing any pooling of water. The al/zinc metal with a higher grade thickness should help as well. However, I will ask the builder to coat the screws with the best caulking for the temperature and cover every screw with a rubber cover they sell. I still have to find out how strong the bonding to the roof is.I suspect this is not a great solution as these are rubber and black (on white would be ugly). Painting the rubber might not work. Alternatively, I am thinking a V strip or a u strip the height of the screws fastened with the caulking over each screw) and a more permanent screwing at the top and the bottom of the roof panles would be a more permanent and resilient method. The screws are of the better type design that accommodate some play, which happens as metal expands (3 mm for 3 m per degree I read). I do not want to take the chance. The only think I can think is some ambient humidity being trapped within the strip and making things worse. I could put some dessicant in there to make sure that will not happen so much. I would be high;ly unlikely that water vapour cannot get out from those strips.

What do you think?

Crossy · December 4, 2017

Number one, you have your expansion coefficient way off, steel is 0.000012 (m/m^oC) so your 3m length will expand by about 0.4mm for a 10C rise, in the spans we are concerned with not worth worrying about.

You can calculate here https://www.engineeringtoolbox.com/linear-thermal-expansion-d_1379.html

Are you using the metal roofing with integral insulation that also provides significant noise reduction and has the foil radiation barrier on the inside?

I wonder just how much heat is going to bridge via the steelwork, the inside of our tiles get too hot to touch, the steel they sit on isn't much above ambient. Small contact areas and the like. No I've not done any actual measurements and we have massive gable vents coupled with ventilated "creature stoppers" at the roof edges.

I suggest there are much bigger heat leaks to worry about than the steelwork bridges.

EDIT Also, what is your anticipated indoor temperature? If you are happy with 25C inside when it's 32C outside we are well into "law of diminishing returns" territory.

Kwasaki · December 4, 2017

1 hour ago, EnlightenedAtheist said:

I do not think that a ridge vent is possible on metal sheet roofs,

yes it is and available in Thailand.

1 hour ago, EnlightenedAtheist said:

hence the gable vent.

If you have gables vent them as large as practical and eaves.

1 hour ago, EnlightenedAtheist said:

Sadly raised-seams types of metal roof are not readily available here,

No idea of terminology you are using.

1 hour ago, EnlightenedAtheist said:

I will ask the builder to coat the screws with the best caulking for the temperature and cover every screw with a rubber cover they sell.

Why, useless.

2 hours ago, EnlightenedAtheist said:

The screws are of the better type design that accommodate some play,

That's why top of corrugation roll fixing is best.

2 hours ago, EnlightenedAtheist said:

The only think I can think is some ambient humidity being trapped within the strip and making things worse.

No it won't, negligible at the lest

2 hours ago, EnlightenedAtheist said:

What do you think?

I think you think too much as others here anyone would think building in Thailand is rocket science.

EnlightenedAtheist · December 4, 2017

1 hour ago, Crossy said:

Number one, you have your expansion coefficient way off, steel is 0.000012 (m/m^oC) so your 3m length will expand by about 0.4mm for a 10C rise, in the spans we are concerned with not worth worrying about.

You can calculate here https://www.engineeringtoolbox.com/linear-thermal-expansion-d_1379.html

Are you using the metal roofing with integral insulation that also provides significant noise reduction and has the foil radiation barrier on the inside?

I wonder just how much heat is going to bridge via the steelwork, the inside of our tiles get too hot to touch, the steel they sit on isn't much above ambient. Small contact areas and the like. No I've not done any actual measurements and we have massive gable vents coupled with ventilated "creature stoppers" at the roof edges.

I suggest there are much bigger heat leaks to worry about than the steelwork bridges.

EDIT Also, what is your anticipated indoor temperature? If you are happy with 25C inside when it's 32C outside we are well into "law of diminishing returns" territory.

Thanks, Crossy.

Good to hear that you are a metal tile believer. I am not alone.

Sadly, I don't have access to tables and such. I am not an engineer. Thanks for the link. I will look into it. Personally, I think I know a lot more than the average person though. Building is not my profession. I don't profess to know everything, but I think most people. Does the average owner know about the clay tiles. You must control the wind flow carefully because wind moves them, I hear. If you don't have enough wind, the heat radiates for hours after sunset. As you know the key with metal is that its reflectivity and that they get much cooler much quicker after the sun has gone down. They do get hotter, all things being equal though. That is why I have 6"+ gap or 9" of fibreglass in the drop ceiling. The vent helps, but its is only as good as the wind is. Still, I have oriented the building in line with the wind. The utilities and the stores are not going to tell the whole truth, are they? (Like everyone is buying the marketing "Granito" tiles pitch and often paying more than the real granite tiles that offer better value. It seems to me that the 1mm coat is not as good as the 8 mm or more real tiles. Anyway,...)

I recall the figure being given for metal tiles. Now, either the guy given the figure got it wrong or he was talking about a different metal. The coefficient given was not for the steel. My builder/architect told me that the bricks (the first rows touching/near the steel should not bridge too much heat as there is usually a gap that they fill with cement. I would prefer acc as I know they are better for heat. I suggested to use the last row before the joists, but then I was told that there is usually a gap that is filled with cement. I still think acc should be better (but maybe it is overkill), but the sun/wind beating on the wall/windows are going to be more of an issue I think. I had planned to to double walls on key areas. I might even do a double windows with an air gap, but I don't know which is cheaper as I haven't priced them yet.

I am told that aluminium windows are stronger than plastic, but I am told that wood is better except for the termite/ant issue and paint peeling of course. I plan to have awnings in key areas though and see how that go. Worse comes to worse, if I can do it, I will add second cheap windows. Surely, the ROI will be better than using a/c 8 hrs a day.

Of course, I am not going to build something that has a poor ROI. Do I sound like I am an idiot? I am not a civil engineer. My grand-father was. I wish he were alive. I am a outside-of-the-box thinker as I am an outsider. However, I don't profess to know everything.

Am I smart to use white tiles VS bare tiles? I know white helps with heat, but both reflect. Not sure what the diff. is. The latter will not discolour, but it might rust quicker than the former. They are the same price. Any thoughts. What did you choose? What brand did you buy? Are you happy? How long have you had them for? You have foam and foil?

I thank you for your advice and ideas. Much appreciated.

EnlightenedAtheist · December 4, 2017

23 minutes ago, Kwasaki said:

yes it is and available in Thailand.

If you have gables vent them as large as practical and eaves.

No idea of terminology you are using.

Why, useless.

That's why top of corrugation roll fixing is best.

No it won't, negligible at the lest

I think you think too much as others here anyone would think building in Thailand is rocket science.

Oops! yes! I meant "standing-seams"! I am rather unfamiliar with this kind of roof as they are rarely used in Canada. I am just learning about this system.

Correct about the screws being placed on the top corrugation is best. The builder/system is using this location.

Thanks for the feedback and the corrections. Much appreciated.

EnlightenedAtheist · December 4, 2017

2 hours ago, Crossy said:

EDIT Also, what is your anticipated indoor temperature? If you are happy with 25C inside when it's 32C outside we are well into "law of diminishing returns" territory.

I think the temperatures in LOS reach higher temperatures than 32 c. In Chiang Mai they do and there is no wind to help most of the times and worse windows must be closed in March and April due when the fires are polluting the air. Where do you live? Thanks for the thought.

EnlightenedAtheist · December 4, 2017

1 hour ago, Kwasaki said:

Why, useless.

"I still have to find out how strong the bonding to the roof is.I suspect this is not a great solution as these are rubber and black (on white would be ugly). Painting the rubber might not work."

If the caulking becomes ineffective in 1 year, it might not be worth it. The builder has still to confirm that the rubber cover is indeed black. If that is the case, that would be rather unsightly. A V or U strip might be more effective, efficient (to place/repair), and paintable.

Artisi · December 4, 2017

I think you are being far too academic regarding the roof.

Australia was founded on galvanised iron roofs , walls, water tanks etc. and have it down to a fine art, Google Colorbond which is available in Thailand and give them the problem and be guided by their recommendations.

Bear in mind that outback Aus. can be a lot hotter than most of Thailand.

Edited December 4, 2017 by Artisi

EnlightenedAtheist · December 5, 2017

17 hours ago, Artisi said:

I think you are being far too academic regarding the roof.

Australia was founded on galvanised iron roofs , walls, water tanks etc. and have it down to a fine art, Google Colorbond which is available in Thailand and give them the problem and be guided by their recommendations.

Bear in mind that outback Aus. can be a lot hotter than most of Thailand.

Artisi,

I have never heard of Colorbond in Canada and I doubt any Canadians has. Now that I know, I can move forward. As it turns out, the builder/architect has recommended I use Bluescope/Colorbond. A bit confusing the marketing/branding, but ... never mind. She has been trained to use this, so she tells me.

EnlightenedAtheist · December 5, 2017

21 hours ago, Crossy said:

Number one, you have your expansion coefficient way off, steel is 0.000012 (m/m^oC) so your 3m length will expand by about 0.4mm for a 10C rise, in the spans we are concerned with not worth worrying about.

You can calculate here https://www.engineeringtoolbox.com/linear-thermal-expansion-d_1379.html

Oops! I was close, but a bit off by ... what a factor of 100! However, this expansion does take place everyday. Correct me if I am wrong, but your 10 degree rise is quite a bit --as you stated it-- because a tile can get very high. And the night temperature can be in the 20's or 30's. That's a 50 degrees difference. No?

Crossy · December 5, 2017

I used 10^oC delta-t as the calculator said "zero" when I used 1^oC

Anyway, if we use a nighttime low of 20^oC (Chiang Mai) as the minimum temperature maybe your roof space could get to 50^oC at the peak of the day so 30^oC delta-t, so 1.2mm over a 3m run of steel.

Your roof covering may well get a lot warmer than that, depending upon the colour, but even if your covering achieves 80^oC that's still only 2.4mm movement (1.2mm differential with the structure).

These movements are not significant, even a concrete column 2.5m high will absorb that much and it will be doing its own expanding and contracting at about 0.000013 (m/m^oC) which is very close to that of steel anyway (which is why steel reinforcing doesn't ping out all the time).

Our longest roof member is 9m on 2.5m concrete columns, roof steel is welded directly to the column re-bar although there is a concrete ring-beam, no cracking of the wall render after 6 years.

Unless you have really long structures I really wouldn't worry about managing expansion movements. The roof covering fixings will have enough movement as-is.

By the way, you asked earlier where we are, northern BKK is the answer so we don't get issues with smoke or really "cool" nights. We only have aircon in the bedrooms (usually set to 28^oC), never got round to installing elsewhere as we have windows/doors open 24/7/365 (and downstairs has no walls anyway).

Artisi · December 5, 2017

28 minutes ago, EnlightenedAtheist said:

Artisi,

I have never heard of Colorbond in Canada and I doubt any Canadians has. Now that I know, I can move forward. As it turns out, the builder/architect has recommended I use Bluescope/Colorbond. A bit confusing the marketing/branding, but ... never mind. She has been trained to use this, so she tells me.

Bluescope/Colorbond, one of the same. I believe that steel framing did cause a few headaches when first introduced into Aus. whether true / false or urban myth I don't know but believe there are no problems.

EnlightenedAtheist · December 5, 2017

5 minutes ago, Crossy said:

I used 10^oC delta-t as the calculator said "zero" when I used 1^oC

Anyway, if we use a nighttime low of 20^oC (Chiang Mai) as the minimum temperature maybe your roof space could get to 50^oC at the peak of the day so 30^oC delta-t, so 1.2mm over a 3m run of steel.

Your roof covering may well get a lot warmer than that, depending upon the colour, but even if your covering achieves 80^oC that's still only 2.4mm movement (1.2mm differential with the structure).

These movements are not significant, even a concrete column 2.5m high will absorb that much and it will be doing its own expanding and contracting at about 0.000013 (m/m^oC) which is very close to that of steel anyway (which is why steel reinforcing doesn't ping out all the time).

Our longest roof member is 9m on 2.5m concrete columns, roof steel is welded directly to the column re-bar although there is a concrete ring-beam, no cracking of the wall render after 6 years.

Unless you have really long structures I really wouldn't worry about managing expansion movements. The roof covering fixings will have enough movement as-is.

By the way, you asked earlier where we are, northern BKK is the answer so we don't get issues with smoke or really "cool" nights. We only have aircon in the bedrooms (usually set to 28^oC), never got round to installing elsewhere as we have windows/doors open 24/7/365 (and downstairs has no walls anyway).

Thanks. Okay. It looks like this is a pretty robust design then. Thanks for the explanation.

Crossy · December 5, 2017

This is our home, designed by my own fair hand (ok it's based on an existing certified design), the curved steel roof structure is copied from a factory in Ayutthaya (actually the place that made the teak barge-boards)

The roof isn't Bluescope, apparently there are issues with such a steep pitch and minds more important than mine (i.e. the wife) decided on more conventional cement tiles. Since the roof is her baby I couldn't really argue

Blow by blow construction saga here, lots of discussion and useful stuff.

maxpower · December 5, 2017

1 hour ago, Crossy said:

This is our home, designed by my own fair hand (ok it's based on an existing certified design), the curved steel roof structure is copied from a factory in Ayutthaya (actually the place that made the teak barge-boards)

The roof isn't Bluescope, apparently there are issues with such a steep pitch and minds more important than mine (i.e. the wife) decided on more conventional cement tiles. Since the roof is her baby I couldn't really argue

That above ground pool is interesting, ideal for the kids school we sponsor.

Crossy · December 5, 2017

26 minutes ago, maxpower said:

That above ground pool is interesting, ideal for the kids school we sponsor.

It came from pattaypools.net they carry (OK drop ship) a large selection of the Intex range, shipping is from Bangkok so no significant delays. Prices to suit all budgets.

EnlightenedAtheist · December 6, 2017

Someone mentioned using reflective foil under the metal tiles for heat. I also need soundproofing (although I will have 6 to 9" in the drop ceiling on the second floor). I guess every little bit helps with sound as the roof cavity will act as an echo chamber.

I wonder of the idea of using spray foam as the third/last layer after the foil to prevent sound/noise (from airplanes, dogs, chickens,...) entering from vents, but the thin structure as well. I think that is what people use. There might be a layer of foam on the Colorbond tiles as well. Not sure which is best for heat (order of the two layers), but I think foam in the last layer makes sense for sound. I understand hard-cell is expensive, but I also read soft-cell is okay. I am reading that soft-cell sprayed foam is unaffected by water, if water or water vapour were to come in contact with it. Would it be a good idea to put the foam around the joists/trusses as well to reduce heat transfer? I have no idea on pricing. The area of the house is 64m2.

EnlightenedAtheist · December 6, 2017

On 12/1/2017 at 6:34 AM, Kwasaki said:

Mainly because it's a matter of course.

Re: bridging not being mentioned or addressed by engineer/architect.

Well, that's easy to say, but in reality it is not. Do you want me to talk about beautiful balconies with metal rebar bridging into the condos or houses? Do you want me to talk about the slab layer of concrete (again with rebars) bridging into the 2nd floor area? Do you want me to talk about window frames (of aluminium) often here with 1 pane bridging into all areas of the house (especially if positioned on the sun exposed sides)? How about external concrete columns with rebar? Do not even attempt to tell me that this is insignificant. Or that it could not be easily address. The developers, builders, architects, and engineers are not talking or addressing this issue, if not I would not see so many flawed designs. But, hey, it looks good!

Kwasaki, action speaks louder than words. You can fool some of the people some of the times, but not all of the people all of the times. I wonder if you will make any retractions. People usually don't when they are found to be erring.

EnlightenedAtheist · December 6, 2017

On 12/4/2017 at 4:50 PM, Crossy said:

Number one, you have your expansion coefficient way off, steel is 0.000012 (m/m^oC) so your 3m length will expand by about 0.4mm for a 10C rise, in the spans we are concerned with not worth worrying about.

You can calculate here https://www.engineeringtoolbox.com/linear-thermal-expansion-d_1379.html

Btw, I did not make a computational error, but I might have FORGOTTEN that it was POINT/decimal 3 mm for 3 M. Btw, I had to quickly convert this info provided in imperial meas. to metric. But, I erred. And I thank you for correcting me.

Btw, are H-beam/channels in aluminium available. The length would need to be in around 5, but preferably 10 m or so. I would like the upper and lower cavity of the H to be long and slim (ideally 1 cm or 2 cm in thickness and 5 + cm in length? How slim and how long are they usually? Of course, they would need to support the weight of whatever I would slide into them. At this time it would be one light concrete panel and an aluminium sheet per section.

Here is a sketch of what I would need the H channel/beam to look like: https://docs.google.com/drawings/d/12D3V2Z4WbWc2pfNVV0gnBp1u9bw2L4QhmgBVn9klebk/edit?usp=sharing

Maybe there are stores in CM that have those or maybe I need to order them somewhere in BKK or from Alibababa.

kamalabob2 · December 6, 2017

Is the Op working on a budget issue to consider a bluescope roof instead of a CPAC Monier cement tile roof? I have slept in plenty of homes in Thailand and the bluescope metal roof homes with insulation could not compare to a home in Buriram with CPAC Monier or Diamond or Shera brand cement roof tiles. Yes you need more steel and have some limitations on roof pitch when your architect selects flat roof tiles. I own a home built with AAC autoclaved wall blocks, with a few a/c units, a swimming pool, and the PEA bill is under 3000 baht a month. I never hear the rain, and need to only run the a/c unit for a short period to cool down any upstairs bedroom. I installed 12 mm thick gypsum ceiling boards, and 3" insulation above the ceiling.

If the OP has already lived in Thailand in a home with CPAC Monier flat cement tiles with insulation and he has decided to live in a home with a metal roof it certainly is his choice. If the OP is keen on a metal roof he may wish to contact Matthew Springall who is a manager of Naspa Asia. He can look at their web site and realize Mathew is on the cutting edge of metal roofs in Thailand. One of the people I met at the Architect Expo in Bangkok. The booth at the Architect Expo showcased that Naspa Asia Co.,Ltd. is a leading producer of profiled metal sheet using only BlueScope steel products. Their product range includes AllSeasons and KaWa brands of roof and wall sheeting, Manik Composite Panels and Rhino Water Tanks. I wish the best to the OP and he may want to attend the free Architect Expo and met engineers who work for various steel companies, roof tile manufacturers and metal roofing companies.

EnlightenedAtheist · December 6, 2017

21 minutes ago, kamalabob2 said:

Is the Op working on a budget issue to consider a bluescope roof instead of a CPAC Monier cement tile roof? I have slept in plenty of homes in Thailand and the bluescope metal roof homes with insulation could not compare to a home in Buriram with CPAC Monier or Diamond or Shera brand cement roof tiles. Yes you need more steel and have some limitations on roof pitch when your architect selects flat roof tiles. I own a home built with AAC autoclaved wall blocks, with a few a/c units, a swimming pool, and the PEA bill is under 3000 baht a month. I never hear the rain, and need to only run the a/c unit for a short period to cool down any upstairs bedroom. I installed 12 mm thick gypsum ceiling boards, and 3" insulation above the ceiling.

If the OP has already lived in Thailand in a home with CPAC Monier flat cement tiles with insulation and he has decided to live in a home with a metal roof it certainly is his choice. If the OP is keen on a metal roof he may wish to contact Matthew Springall who is a manager of Naspa Asia. He can look at their web site and realize Mathew is on the cutting edge of metal roofs in Thailand. One of the people I met at the Architect Expo in Bangkok. The booth at the Architect Expo showcased that Naspa Asia Co.,Ltd. is a leading producer of profiled metal sheet using only BlueScope steel products. Their product range includes AllSeasons and KaWa brands of roof and wall sheeting, Manik Composite Panels and Rhino Water Tanks. I wish the best to the OP and he may want to attend the free Architect Expo and met engineers who work for various steel companies, roof tile manufacturers and metal roofing companies.

Oh! Thank you for the information.

I will investigate the options you gave me.

If there is no ridge vent, only 2 side gable vents and on the opposite side 2 soffit vents (typical A roof). A pyramid will have more soffit vents, but no gable vents (not sure if it is even possible with metal sheet --at a reasonable price, that is).

The builder certifies us that the bluescope system does not have a ridge vent system. Is she right?

Edited December 6, 2017 by EnlightenedAtheist

Kwasaki · December 6, 2017

3 hours ago, EnlightenedAtheist said:

Kwasaki, action speaks louder than words. You can fool some of the people some of the times, but not all of the people all of the times. I wonder if you will make any retractions. People usually don't when they are found to be erring.

Why would I retract my knowledge in building I really can't be bothered by wanna be builders like you in Thailand anymore I'm retired so lets just say good luck with your project, insults come cheap from people like you and go in one eye and out the other.

EnlightenedAtheist · December 6, 2017

1 hour ago, Kwasaki said:

Why would I retract my knowledge in building I really can't be bothered by wanna be builders like you in Thailand anymore I'm retired so lets just say good luck with your project, insults come cheap from people like you and go in one eye and out the other.

Insults? Where? For pointing out glaring errors in your information.

We are not able to critical assess information now? We must believe everything as truth. Goodbye critical thinking.

I don't have the right to disagree with you? Anyone? You are right and, by default, everyone is wrong. Sorry! I went to university and I don't believe everyone.

Crossy · December 6, 2017

Ok chaps let's play nicely shall we, opinions differ no need to trade insults or whatever.

Not wishing to rain on anyone's parade but something which it is vital to understand when building in sunny Thailand is that trying something unconventional and outside to comfort zone of your contractor is going to :-

Be expensive
Be painful
Probably not work as expected anyway

As I've noted before, the law of diminishing returns also come in to play. Yes, not having steel re-bar where slabs go from outside to inside will probably make a measurable (but slight) difference to heat transmission. But you can't build a structural slab with no re-bar so we're looking at alternative materials, carbon-fibre anyone?

Invariably the alternatives are:-

Less effective
More expensive
Difficult to work
Hard to get right
Made from "unobtainium"

In no particular order some of the most effective ways to reduce heat load:-

Shading of walls from direct sun using plants or shade structures (large overhangs are very effective against mid-day sun).
Similarly, a flying roof can make a massive difference to your attic temperatures if your design allows for it.
Loft insulation (both on the ceiling and inside the tiles) and ventilation.
Cavity walls (brick or AAC)
AAC block walls.
Double glazing.
Other things I've not thought of.

Also, look at the way the locals built homes in the past, there's a reason for the high ceilings and elevated living areas, and they do work.

Artisi · December 7, 2017

3 hours ago, Crossy said:

Ok chaps let's play nicely shall we, opinions differ no need to trade insults or whatever.

Not wishing to rain on anyone's parade but something which it is vital to understand when building in sunny Thailand is that trying something unconventional and outside to comfort zone of your contractor is going to :-

Be expensive

Be painful

Probably not work as expected anyway

As I've noted before, the law of diminishing returns also come in to play. Yes, not having steel re-bar where slabs go from outside to inside will probably make a measurable (but slight) difference to heat transmission. But you can't build a structural slab with no re-bar so we're looking at alternative materials, carbon-fibre anyone?

Invariably the alternatives are:-

Less effective

More expensive

Difficult to work

Hard to get right

Made from "unobtainium"

In no particular order some of the most effective ways to reduce heat load:-

Shading of walls from direct sun using plants or shade structures (large overhangs are very effective against mid-day sun).

Similarly, a flying roof can make a massive difference to your attic temperatures if your design allows for it.

Loft insulation (both on the ceiling and inside the tiles) and ventilation.

Cavity walls (brick or AAC)

AAC block walls.

Double glazing.

Other things I've not thought of.

Also, look at the way the locals built homes in the past, there's a reason for the high ceilings and elevated living areas, and they do work.

1st sentence post #3.

Kwasaki · December 7, 2017

13 hours ago, EnlightenedAtheist said:

Insults? Where? For pointing out glaring errors in your information.

We are not able to critical assess information now? We must believe everything as truth. Goodbye critical thinking.

I don't have the right to disagree with you? Anyone? You are right and, by default, everyone is wrong. Sorry! I went to university and I don't believe everyone.

No glaring errors at all and certainly not my problem if you do not agree, had the same rhetoric with Architects straight from University

Please do what think is right and so as I posted before lets just say good luck with your project,

15 hours ago, Kwasaki said:

I wonder if you will make any retractions.

Insult.

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