Foil Roof Insulation

[Swelters]

Foil insulation seems to be the roof insulation of choice in Thailand these days and I myself gave it a try in building a house with the usual tile roof which tends to seriously overheat. I have been not happy with the results, as explained at:

http://www.thaivisa.com/forum/blog/swelters/index.php?

If others have had similar (or contrary) experience, I'd be interested in hearing of it.

Swelters

[Lost in LOS]

used foil in my house in hawaii. as it was being installed [after the fact from the attic] i checked the plywood sheeting with an infared heat detecting gun and it read 95 degrees [mid morning] and when i shot the foil adjacent to it the reading was 10 degrees less on the house side. works well, but i would use fiberglass insulation as well if feasable

[lingling]

Foil insulation seems to be the roof insulation of choice in Thailand these days and I myself gave it a try in building a house with the usual tile roof which tends to seriously overheat. I have been not happy with the results, as explained at:

http://www.thaivisa.com/forum/blog/swelters/index.php?

If others have had similar (or contrary) experience, I'd be interested in hearing of it.

Swelters

Did you write "shiny side down"? ehh, kind of takes away the idea, doesn't it? Why not paint it black too?

[Swelters]

Did you write "shiny side down"? ehh, kind of takes away the idea, doesn't it? Why not paint it black too?

Nope, shiny side down is fine, as long as it faces an air space. Shiny side up is not good because the surface will soon get covered with soot and dust and become ineffective -- about one year in Bangkok. We made mistakes as the link shows, but down vs up wasn't the main problem.

[lingling]

Did you write "shiny side down"? ehh, kind of takes away the idea, doesn't it? Why not paint it black too?

Nope, shiny side down is fine, as long as it faces an air space. Shiny side up is not good because the surface will soon get covered with soot and dust and become ineffective -- about one year in Bangkok. We made mistakes as the link shows, but down vs up wasn't the main problem.

The shiny side is the reflective side. The idea of using foil is that the reflective side reflects heat (IR) back in the direction it came from. The matte side absorbs heat, the shiny side reflects it.

I am not surprised that they installed it upside down though - when packing food in foil, all thais turn it inside out too (shiny side out when wrapping hot food ).

But you're right, air or some insulating material on the cold side makes it a lot more efficient. Rock- or glass wool is probably the best/most cost effective. It comes pre-packed in foil here btw to keep moisture and bugs out of it. Other alternatives are PU foam, sprayed cellulose fiber etc, but that's more expensive.

[chownah]

I have no experience with foil insulation but I read on an Australian website about insulations that some foils have a different R value in different directions....i.e. it has a higher R value in one direction and a lower R value in the other direction...so it really does matter (I guess) which way these things are installed..although they would work somewhat either way only but there would be one way that would be best....

Chownah

[Nawtilus]

Anybody have experience with the spray on foam which basically dries rock hard I believe and is sprayed on the inside of the roof material ie: on the underside of tiles or steel sheeting.

It is supposed to be very good, waterproof and such claims as well as adding strength.

They claim that if you use this, you do not need any other material, so no fibreglass or wool or reflective foils etc.

I am thinking to use it, but it is expensive, so some feedback would be handy. Its priced at 475b per sqm.

[chownah]

I believe that this is rigid urethane foam....or something similar. It should have a high R value compared to other materials of similar thickness. The thing I've always wondered about is that since it is water proof and since they spray it right onto the bottom side of your wooden roof members then it would basically keep them from drying out and perhaps facilitate decay....of course if you have a metal roof you could be sure to coat the metal with a couple coats of waterproof paint before applying I guess....I don't really know if this would be a problem or not...its just a concern that I imagined.

Chownah

[tutsiwarrior]

if you've got a ceiling between your roof and your living space just use 6" thick fiberglass blankets available at HomePro...a bit pricey but does the trick...did for me in our shophouse; went from full time A/C with limited effectiveness to just a ceiling fan for the required interior comfort temp...

but these are cooler days now...have to check the insulation performance in March/April...

[suiging]

One other thing in favour for the set foam, is security. Little beggers can't take your tiles off and slip in quite so easily.

[tutsiwarrior]

One other thing in favour for the set foam, is security. Little beggers can't take your tiles off and slip in quite so easily.

if that's the problem set a trip wire with a few ounces of plastic explosive...don't bother with the bleddy insulation...

[dsfbrit]

if you've got a ceiling between your roof and your living space just use 6" thick fiberglass blankets available at HomePro...a bit pricey but does the trick...did for me in our shophouse; went from full time A/C with limited effectiveness to just a ceiling fan for the required interior comfort temp...

but these are cooler days now...have to check the insulation performance in March/April...

I didn't like the idea of the foil method - all the tests in the shops showed how great they worked in direct sunlight - not inside a roof space gathering dirt.

I thought I would do the same as I did with the roof insulation in the UK - but haven't got around to checking into this.

Its been 3 years now so I may as well do something.

How good is this approach?

Any downsides

thanks for your thoughts

[Gary A]

Anybody have experience with the spray on foam which basically dries rock hard I believe and is sprayed on the inside of the roof material ie: on the underside of tiles or steel sheeting.

It is supposed to be very good, waterproof and such claims as well as adding strength.

They claim that if you use this, you do not need any other material, so no fibreglass or wool or reflective foils etc.

I am thinking to use it, but it is expensive, so some feedback would be handy. Its priced at 475b per sqm.

A friend of mine just built a BIG house near Jomtien. He had the entire underside of his tile roof spray foamed. I expect his house is about 300 square meters so I really doubt that it cost him 475 baht per square meter. Unfortunately he is in the US right now or I would ask him.

[dsfbrit]

Anybody have experience with the spray on foam which basically dries rock hard I believe and is sprayed on the inside of the roof material ie: on the underside of tiles or steel sheeting.

It is supposed to be very good, waterproof and such claims as well as adding strength.

They claim that if you use this, you do not need any other material, so no fibreglass or wool or reflective foils etc.

I am thinking to use it, but it is expensive, so some feedback would be handy. Its priced at 475b per sqm.

A friend of mine just built a BIG house near Jomtien. He had the entire underside of his tile roof spray foamed. I expect his house is about 300 square meters so I really doubt that it cost him 475 baht per square meter. Unfortunately he is in the US right now or I would ask him.

I am not trying to be 'stupid' I promise you, but what happens if you want to remove the tiles for some reason?

To be honest it seems like a dumb question, because I cannot think of a reason to remove tiles anyway.

If there is no downside to this except the cost I am beginning to warm to this method. It will keep out the thieves as well.

If you could come back later on with the actual cost of yours friends place I would appreciate it.

thanks for your help

[Nawtilus]

Yes Gary A, please send your friend an email answers to questions we need to know !!

As for the need to remove a tile, well if one breaks you would need to I guess. My roof is steel sheet, so not have that problem.

Also the price he paid would be nice to know. As you mentioned his house is 300sqm, but I would presume the roof is not that full size...or is it only one level, then maybe it is. My house is 340sqm but the roof is only 205sqm.

As for the 475 baht psqm, this was supposedly the best material available, there are cheaper options for 200 to 250 baht around for sure, but not sure on what the difference is.

The 475b is only 1 inch thick, some others are 2 inch thick, but I would presume they are a lesser quality perhaps to require a thicker spread.

[Riley'sLife]

For roof insulation to work effectively in Thailand there should be an element of roof ventilation incorporated in the design. The laws of physics (heat rises) can be used to ventilate the roof space by providing ventilation at the eaves to allow cooler air to enter, and at the ridge (and/or the gable end wall if applicable),to allow the hot air to vent. For this to work well it's best not to insulate immediately beneath the roof covering. By not insulating immediately beneath the roof covering the air in the roof space will heat up- exactly what is required for the vented design to work. This "natural" ventilation is both free, and beneficial to the structure. In this design the use of spray applied Isocyanate foam, or aluminium and foam sandwich layers immediately underneath the roof covering would be counter productive.

The insulation in this design works best when placed immediately above the ceiling in the roof void.

- I use 4 inch thick, 600mm wide x 4m long fiberglass (rockwool) sealed inside aluminium foil which is rolled out on top of the ceiling (9mm thick, 2400mmx1200mm foil-backed plasterboard -gypsum, supported by an aluminium framed suspended ceiling).

It is essential to incorporate metal mosquito netting in the ridge and eaves ventilation to prevent the ingress of vermin.

This works really well and is a suitable technique for both refurb and new construction.

Personally, I would never use Isocyanate foam as future maintenance of the roof covering could become a nightmare if for any reason replacement is required, the cost is prohibitive and it requires specialist application.

Aluminium foil/foam sandwich insulation is ideal for appication immediatelt beneath the roof covering only where the roof projects beyond the walls externally, as this will reduce the heat transmitted to the walls. If the building is single storey, this will also make it more comfortable when sitting beneath a projecting roof.

Hope this helps.

Cheers Rick

[chownah]

are you sure its aluminum foil wrapping or is it aluminized plastic?

[Jai Dee]

For roof insulation to work effectively in Thailand there should be an element of roof ventilation incorporated in the design. The laws of physics (heat rises) can be used to ventilate the roof space by providing ventilation at the eaves to allow cooler air to enter, and at the ridge (and/or the gable end wall if applicable),to allow the hot air to vent.

You could add a ventilator as is being discussed in this thread.

[Naam]

Nope, shiny side down is fine

*****

of course! shiny side down is as efficient as a condom pulled over the left ear during sexual intercourse to prevent being infected with AIDS.

[Farma]

Swelters. Thanks for your advice on installing it shiny side down.

So when will you be lifting the tiles so you can turn the foil the right way round?

[Swelters]

Thanks for some good discussions.

There is a paradox here, foil can be very effective under certain circumstances. If you've got a hot tin (or cement tile) roof, a cheap layer of foil stuck to the underside, shiny side down, will do wonders, provided the space below is well ventilated.

I've added a new entry to the blog explaining the physics of this odd result.

http://www.thaivisa.com/forum/blog/swelters/index.php?

I believe some of the respondents are confusing reflectance and emittance.

Swelters

[Farma]

You might want to read some of the manufacturers websites. Shiny side down appears to be the recommencation for cold climates to reduce heat loss.

[tartempion]

I just applied aluminium foil under the roof tiles, will need to wait though until house finished to evaluate results. In the house I rent now we have 5 degrees Celsius more inside versus outside. I hope new house will be cooler. Cost was 15k baht for 300 sqm foil.

I issued a price request for foam and was quoted 110k baht for 120 sqm bungalow, I found this too expensive.

If results are poor I will add fiberglass in alu wrapping above ceiling (Staty cool from Home Market)

[Gary A]

If there is no downside to this except the cost I am beginning to warm to this method. It will keep out the thieves as well.

If you could come back later on with the actual cost of yours friends place I would appreciate it.

thanks for your help

I emailed my friend and he has already answered. He says 475 baht per sq. meter is a little high but not much, so it is expensive. He had it sprayed on one inch thick. All the exact figures and other information are at his new home in Jomtien. He will be back from the US the 1st of December and would be happy to show you what it looks like and give you all the details. PM me if you want to have a look or want further information.

[The Skipper]

The vapor barrior should be against the inside walls as to not trap moisture.

[dsfbrit]

If there is no downside to this except the cost I am beginning to warm to this method. It will keep out the thieves as well.

If you could come back later on with the actual cost of yours friends place I would appreciate it.

thanks for your help

I emailed my friend and he has already answered. He says 475 baht per sq. meter is a little high but not much, so it is expensive. He had it sprayed on one inch thick. All the exact figures and other information are at his new home in Jomtien. He will be back from the US the 1st of December and would be happy to show you what it looks like and give you all the details. PM me if you want to have a look or want further information.

Thanks for contacting him for me.

I think I am going to try the rockwool over just one room for now - the small bedroom first - see how that works.

To be honest, I dont really want to spend any money here until the land ownership thing is 'resolved' (whatever resolved means !).

In fact, because of the uncertaity, I dont spend any money on substantial improvements in LOS at all at the moment - just on necessary maintenance on house, car etc...

I would have to be sure I can live in this house 'legally' before I spend money on any significant improvements.

If I do decide I want to give the foam thing a try - I would very much like to take up your kind offer.

regards

[chownah]

This is what might happen if the vapor barrier is on the inside of a wall for a house with blanket insulation and airconditioning keeping the inside cool:

The outside air will often be hot/warm and moist. When this warm moist air infiltrates the blanket (since the vapor barrier is on the inside then I'm assuming that the outside of the blanket does not have a vapor barrier and so the air will slowly infiltrate the blanket) and as it gets nearer to the cooler inner surface of the wall it (the warm moist air) gets cooled as well. As air gets cooled it 's ability to hold water is reduced and if it gets cooled enough it will become saturated (100% relative humidity) and if it gets cooled even more then some of the water in the air will come out of the air and condense on the blanket material which will make the blanket material wet which not only reduces its effectiveness as an insulator but also is a perfect place for bacteria, fungus, and other critters to live.

Chownah

[Swelters]

This is what might happen if the vapor barrier is on the inside of a wall for a house with blanket insulation and airconditioning keeping the inside cool:

The outside air will often be hot/warm and moist. When this warm moist air infiltrates the blanket (since the vapor barrier is on the inside then I'm assuming that the outside of the blanket does not have a vapor barrier and so the air will slowly infiltrate the blanket) and as it gets nearer to the cooler inner surface of the wall it (the warm moist air) gets cooled as well. As air gets cooled it 's ability to hold water is reduced and if it gets cooled enough it will become saturated (100% relative humidity) and if it gets cooled even more then some of the water in the air will come out of the air and condense on the blanket material which will make the blanket material wet which not only reduces its effectiveness as an insulator but also is a perfect place for bacteria, fungus, and other critters to live.

Chownah

I believe Chownah is correct, moisture barrier (if any-not usual in Thailand) on the warm side of the insulation (outside).

impervious "house wraps" are now standard in the US, the goal is a completely sealed house. Big mistake, in my view, it became apparent that people were getting poisoned by formaldehyde and other stuff off-gassing from plastic furnishings. So next they introduced requirements for forced ventilation. Give us back that humid air! More complications, more money. The building code process in the US is suffused with the spirit of Thailand.

I find a completely sealed space kind of creepy (where are those soi dogs and roosters?). There is even a joint Chinese/MIT study suggesting that cutting people of from the natural rhythms of outdoor air movement might be mentally unbalancing!

On the other hand, the real work of an air conditioner in tropical climes is mostly moisture removal, it's what you really want (mostly), not heat reduction. Look at your aircon outlet, drip..drip..drip. That's where most of the energy is going, condensing all that water. So from the energy standpoint, you can justifiably argue that sealed spaces are great...which is how the whole cycle got started in the US.

Until folks began to notice their farts lingering on...

Swelters

[Nawtilus]

Submariners live with it.

[The Skipper]

Granted the houses I built in the US are made of wood studs, not concrete, so maybe the way to install it is different here?

We followed the mfgs instructions, stapled the vapor barrior against the studs, fiberglass side facing out and covered with drywall.

That's the proper way to do it there. No?

Insulation works wonders. I had a large garage in California, got so warm in the afternoons, couldn't really go in there.

Insulated the place and it was cool as a wine cellar after that.