Roof Insulation

[TS79]

Hi All,

Came across an interesting advertisement in the newspaper for a company that installs a product called PU Foam onto the underside of the roof (a type of expanding polyurathane foam). The foam has an R Value of 9.09. which gives good insulation, and claims to have soundproofing properties, can prevent water ingress, vermin getting in the ceiling etc.

My house gets pretty hot in the summer time and wonder if anyone has any experience with this insulation method, good / bad points etc.

Cheers,

TS.

[bazmlb]

R9 sounds good, would be interested myself

[DMC1]

Got it sprayed under my roof tiles.

It does work, however, in the really hot months the house still gets fairly hot. Then you have the problem of the heat being stuck inside under the foam. This is where you need to have a few of those spinning vents on the roof. During the rest of the year it works quite well and I often get comments from friends who say they can notice the difference.

The best thing about it is the speed at which the bedroom cools in the evening with the AC on. My electric bills are noticeably cheaper.

And yes, it makes the roof very secure and watertight.

[juehoe]

The foam has an R Value of 9.09

Which dimension has this R-Value, [sqmK/W] (ISO) or [sqftFh/Btu] (USA)?

For R-ISO = 9, you need about 25 cm of PU foam, which would be perfect and would fulfil the highest building standards. For R-USA = 9, you need only 4.5 cm of foam.

I asume that it is the R-USA value. In Thailand the foam is generally sprayed in a thickness of 1 to 2 inches (2.5 to 5 cm).

[TS79]

The foam has an R Value of 9.09

Which dimension has this R-Value, [sqmK/W] (ISO) or [sqftFh/Btu] (USA)?

For R-ISO = 9, you need about 25 cm of PU foam, which would be perfect and would fulfil the highest building standards. For R-USA = 9, you need only 4.5 cm of foam.

I asume that it is the R-USA value. In Thailand the foam is generally sprayed in a thickness of 1 to 2 inches (2.5 to 5 cm).

R-USA.

@DMC1, is it expensive to have done? Good point about it trapping the heat in during the very hot summer months.

[beechstreet]

My roof is about to be installed and sprayed with 3 inches of foam. Our guy said that was the max that could be sprayed in one layer, anything over that starts to get too much mass and will drip/droop/gloop off before it has a chance to dry.

[aussiebebe]

My Father in law got his roof sprayed three years ago and also had extraction fans installed. It's really good as long as you find a reliable contractor so look for one which offers a warranty; the foam insulation is waterproof and the energy savings are great but you do need decent roof ventilation which is an additional expense.

The difference is remarkable; I remember the second-floor of his house used to get so hot during the afternoon it was almost uninhabitable. After the foam and ventilation the second-floor became cooler and the air-conditioned ground floor became extremely comfortable with just one 30000BTU unit seeming to easily cool over 150m2. I don't think he'll ever recoup the costs of the installation through energy savings, mind you, as it's so expensive, but it's made his house much nicer to live in.

The good thing about the company he used is that they provided a warranty; he called them back last year and they simply washed and resprayed over one particular bad area (I was surprised you can do this) and they also simply cut out and refoamed another bad area near the spinning silver roof ventilator. I guess after you have it for many years you can just get the old layer sprayed over again. I'm also surprised the foam hasn't cracked, so it must be soft enough to move with the roof as it naturally expands and contracts over the course of the day.

Edited September 17, 2011 by aussiebebe

[Guest]

Of course, if possible, painting the roof with white color is pretty effective way to cool down the house.

[kwonitoy]

I had the interior of my roof sprayed 2 years ago.

If the windows and doors are kept shut when it's hot outside it gives me a 5C lower temp than outside. Before the application was done it got HOT inside the house. Makes a huge difference.

If I had to upgrade a house again I would look at using the heat barrier film attached to the underside of the roof framing

I also checked the temp in my attic space and didn't find it trapped heat, the temp inside doesn't exceeded ambiant temp outside now. I would like to add to add a evacuation fan on both sides of the house and in the evening evacuate the air from the attic and draw air in from the living area. Still looking for someone that I can trust to knock holes in my attic walls without destroying things.

This cool season I'm going to install a roof sprayer system to cool the tiles when its super hot outside. I think that will make a bigger difference, if the roof tiles don't get hot to start with it won't transfer into the house.

Cost for spraying a 150sq m house with single pitched roof was 150,000 baht, and took them 2 days to do.

[DMC1]

The foam has an R Value of 9.09

Which dimension has this R-Value, [sqmK/W] (ISO) or [sqftFh/Btu] (USA)?

For R-ISO = 9, you need about 25 cm of PU foam, which would be perfect and would fulfil the highest building standards. For R-USA = 9, you need only 4.5 cm of foam.

I asume that it is the R-USA value. In Thailand the foam is generally sprayed in a thickness of 1 to 2 inches (2.5 to 5 cm).

R-USA.

@DMC1, is it expensive to have done? Good point about it trapping the heat in during the very hot summer months.

It cost me about 500 baht per square meter. This was nearly 3 years ago. Also, they included 3 spinning vents into the cost.

[TS79]

The foam has an R Value of 9.09

Which dimension has this R-Value, [sqmK/W] (ISO) or [sqftFh/Btu] (USA)?

For R-ISO = 9, you need about 25 cm of PU foam, which would be perfect and would fulfil the highest building standards. For R-USA = 9, you need only 4.5 cm of foam.

I asume that it is the R-USA value. In Thailand the foam is generally sprayed in a thickness of 1 to 2 inches (2.5 to 5 cm).

R-USA.

@DMC1, is it expensive to have done? Good point about it trapping the heat in during the very hot summer months.

It cost me about 500 baht per square meter. This was nearly 3 years ago. Also, they included 3 spinning vents into the cost.

I've just had a quote back for one company, it is 580 baht a square meter, no mention of any extras though. Now to mull it over.

[Naam]

experts have foam sprayed on the ceilings to reduce heat transfer from the hot attic to the rooms below, "lesser experts" have the foam sprayed on the lower side of the roof tiles and then claim they experience thermal miracles

p.s. "faith can move mountains"

[Alcat]

I hope you never have a fire in your roof. These foams are very inflammable and highly toxic. 2 breaths of the black fumes and you are history. Do some fire research first.

[TS79]

I hope you never have a fire in your roof. These foams are very inflammable and highly toxic. 2 breaths of the black fumes and you are history. Do some fire research first.

PU Foam contains a fire retardant agent. Tested to B2 (DIN 4102).

Edited September 26, 2011 by TS79

[beechstreet]

I hope you never have a fire in your roof. These foams are very inflammable and highly toxic....Do some fire research first.

PU Foam contains a fire retardant agent. Tested to B2 (DIN 4102).

My understanding (based on my extensive interweb research skillz) is that the foam is self-extinguishing under "normal" conditions, it won't burn without a continuous flame present. HOWEVER it is apparently possible to create a 'perfect storm' condition where the great insulating qualities of the material can allow a fire to build up such an intense heat that the foam basically spontaneously combusts regardless of the addition of any fire retardants (my interpretation of what I've read). The simple solution according to ASTM E-119 Section R314.5.3 ATTICS is to use an "ignition barrier"...protect the foam with gyp board, sheet metal, even particleboard board can apparently work for this. This is easier to accomplish when you spray on the underside of the roofing and have a vaulted "cathedral" type ceiling. I am a fan of a sealed attic condition (and this crusty old ASHRE paper (pdf) seems to support that), Crossy however appears to prefer a vented type attic. Which ever makes you sleep better at night, just don't mix the two approaches.

Please feel free to correct me or draw your own conclusions. We all like to prove ourselves right but I would certainly appreciate links to articles or tests that both support or refute anything about this topic.

[bbradsby]

PU, or polyurethane is, i believe, the new polyisocyanurate foam, which gives off cyanide gas under high heat. Any chemical engineers pls correct me.

For these plastics, pls note that smoke is the killer, and flames need not be present for plastics to smoke. PVC has the same problem, which is why learned fire marshals wont allow PVC windows/doors/trim in multifamily buildings. PVC window vendors say its non-inflammable to sell their wares. But the smoke can kill even if no flames ever show. The required heat is produced by carpet, drapery, furniture, clothing, bedding, paint on walls.

Polyiso, maybe PU, degrades in presence of water, so it wont stop a leak for long. Polyiso is good vermin food, or at least gets chewed through for some reason.

It is a great insulator at [from memory] over R6/inch. But at least R30 is recommended in this climate's heat. Two inches wont be enough.

Ceiling is the proper location and the gyp board forms the thermal/gas barrier between living space and the toxic material, in combo with proper attic ventilation. The big problem is it'd be exposed in the attic alongside all that Thai electrical workmanship. If anyone has the exact material used/proposed for their house, post it - I'll happily do a tech literature research effort as this is especially important to get right.

[bbradsby]

I hope you never have a fire in your roof. These foams are very inflammable and highly toxic. 2 breaths of the black fumes and you are history. Do some fire research first.

PU Foam contains a fire retardant agent. Tested to B2 (DIN 4102).

pls post your source data if you don't mind.

[sezze]

I hope you never have a fire in your roof. These foams are very inflammable and highly toxic. 2 breaths of the black fumes and you are history. Do some fire research first.

PU Foam contains a fire retardant agent. Tested to B2 (DIN 4102).

pls post your source data if you don't mind.

I will do for him ...

http://www.polyurethanes.basf.de/pu/Nederland/Producten/hardschuim/sproeischuim

Translate or look in english if you want .

Also , PU is at many many places in a house. You can burn it , and probably will give of toxic smoke , but burning other things in the house are not very healthy also . I think about TV's , lightbulbes ( CFL and led ) , sofas , paint , PVC pipes , etc etc . PU foams are much used as insulation materials throughout the world , not only in Thailand and not only as spray on stuff . I'm not b4 or against using the PU foam , i'm only saying that it is a good material to insulate ,next to all the other stuff available on the market .

I do not have the foam and due to price issues i'm not interested at all using it .

[bbradsby]

pls post your source data if you don't mind.

I will do for him ...

http://www...

Translate or look in english if you want .

Also , PU is at many many places in a house. You can burn it , and probably will give of toxic smoke , but burning other things in the house are not very healthy also . I think about TV's , lightbulbes ( CFL and led ) , sofas , paint , PVC pipes , etc etc . PU foams are much used as insulation materials throughout the world , not only in Thailand and not only as spray on stuff . I'm not b4 or against using the PU foam , i'm only saying that it is a good material to insulate ,next to all the other stuff available on the market .

I do not have the foam and due to price issues i'm not interested at all using it .

all good points. to me, it is a question of degree and quantity. wood smoke is dangerous, but not nearly as much as cyanide-laced smoke, else bbq fatalities would be off the hook. if one wanted to live like a monk with a blanket on the floor in a bare structure you'd be safe from toxics, but die of pneumonia or loneliness as you'd never get a girl past the front door. I just want people to know the facts and make informed decisions for themselves versus being sold something they had no idea of the risks in order to mitigate - such as having a [reasonably] airtight, taped & finished gyp board ceiling between them and a fire/smoke hazard such as foam insulation.

[Naam]

I hope you never have a fire in your roof. These foams are very inflammable and highly toxic. 2 breaths of the black fumes and you are history. Do some fire research first.

the average house in Thailand has a steel roof structure. nothing much to burn in the attic.

[Kwasaki]

If you have a steep roof well fixed and have used a light colour and it is well ventilated for air flow it should be no problem.

Rockwool fibre rolled out and laid on the ceilings will be cheaper and sufficient for insulation purposes.

External cavity walls built up to the roof area will assist insulation.

If only single wall paint it white and improve it with internal dry lining.

Double glazing will assist cooling also.

[bbradsby]

The listed DIN 4102 procedure is a burn test in a gas oven purpose built for the test.

Following are the 4102 flammability categories in order of degree of combustibility as well as flammability. Note that some PU foam is advertised as having a fire retardant admixture and a B2 rating, which actually means it is as combustible as wood. Unmitigated PU foam is listed as easily ignitable with a B3 Rating.

A1 100% noncombustible (nichtbrennbar); rockwool

A2 ~98% noncombustible (nichtbrennbar)

B1 Difficult to ignite (schwer entflammbar) intumescents and some high end silicones

B2 Normal combustibility; wood

B3 Easily ignitable; PU foam

Flammability is only one factor in the safety analysis, as smoke development is independent of actual flame-propagation and spread. Plastics such as PVC develop toxic smoke before combustion. Without the name of the actual product, a review of the engineering characteristics is impossible. If in doubt, ask for a small sample and try to ignite it outdoors in a safe location with a torch.

Here's my take-away:

PU foam in Thai home attics should not be installed in contact with electrical wiring, light fixtures or wiring device boxes in my opinion. If it is installed to the underside of a roofing membrane, not very effective thermally, a smoke detector should be installed close to an access panel in the attic as well as in the typical locations in the occupied space.

Edited September 29, 2011 by bbradsby

[Kwasaki]

As I said forget the expensive foam that will have to be maintained and repair from time to time.

The have a cool house in Thailand it has to be built in from the ground up and can stop at the ceilings the roof is just part of the application.

[DMC1]

As I said forget the expensive foam that will have to be maintained and repair from time to time.

The have a cool house in Thailand it has to be built in from the ground up and can stop at the ceilings the roof is just part of the application.

That's right mate. My roof may be nice and cool underneath but you could fry an egg on my back wall in the hot season!!

[Kwasaki]

As I said forget the expensive foam that will have to be maintained and repair from time to time.

The have a cool house in Thailand it has to be built in from the ground up and can stop at the ceilings the roof is just part of the application.

That's right mate. My roof may be nice and cool underneath but you could fry an egg on my back wall in the hot season!!

Yes, some of the heat transfer problems are from single constructed walls even if there painted white.

Where practical it can be overcome with building another tied in wall with a face brick of your choice and insulating the cavity as you progress.

I intend to do this to one of my walls that gets hot.

Alternatively you can dry line from the inside which helps if you have enough room for a good cavity.

[bbradsby]

insulation in concrete or block construction should ideally/thermally be located such that the concrete or block are kept cool, as shaded and possibly air-conditioned thermal mass. So this would imply an externally-applied rigid insulation under some exterior finish system. this is non-typical means & methods in LoS, so not for the uninitiated. To keep it simple, use double, lightweight block walls with polystyrene rigid insulation in the cavity, and make sure you have a water-resistant vapor barrier on the warm side of your insulation and good base-wall detailing to direct water OUT of your envelope.

These measures will be most effective when integrated into a custom house design with:

-proper overhangs, or external shading devices according to orientation

-proper solar & breeze orientation of site, house and rooms

-vapor barrier located on the warm side of insulation

-good window [exterior] shading since a nicely insulated wall will do nothing for you if your windows are single glazed cheapos that receive direct sun

-well-insulated ceilings, not roofs.

-weather-sealed doors & windows since in a leaky house infiltration replaces your 22C air with 34C air every half-hour or so in a light breeze.