Which Insulation Material under the Roof?

[gejohesch]

One question for the "roof insulation experts" (I know there are quite a number on this forum ????). I am planning to improve the roof of one of my wife's houses, somewhere in Isan. It gets terribly hot as soon as the heat builds up outside above the 30 Celsius mark. Maybe we have made the situation worse by having a ceiling built to achieve a more western style habitation - as opposed to the usual Thai style of houses where, being inside the house, one can look up straight at the roof and the supporting beams, struts and what have you (apologies if I'm not using the correct terms, I'm not a building technician). So I'm planning to do 2 things to achieve some heat insulation :

1 - replace the old roofing sheets with new roofing sheets that have a 25mm layer of insulation material glued underneath (some sort of foam?). I have a factory ready to make them at 274 THB / m, the sheets being 75cm in width.

2 - as the old roof will be lifted off, we will have access to the ceiling we had built to separate the habitation from the roof (as explained above). My plan is then to lay insulation material on the ceiling before putting the new roofing sheets in place. For that insulation material (I believe you call it "batts"?), I have found the 2 possible products in Home Pro, and that is my question. Material A is SCG "Stay Cool Green-3 Insulation - Rt 27" at 369 THB per roll. Material B is Sunshield "Extra Cool - Rt 37" at 279 THB per roll. The rolls are 4m long by 60cm wide, i.e. 2.4 sq metres each. I'm talking here of material at 3 inches (75mm) thickness, there is material at double that thickness but I would be worried about the weight and load that would impose on the ceiling, besides coming obviously at a higher price.

 

Now, the total ceiling area to cover is 95 sq metres. I would add 10% to take account of the losses when cutting out for edges and other irregularities. 95 * 110% = 105 sq metres, which means I would need 44 rolls. A = SCG Green stuff would cost me 16,236 THB; B = Sunshield stuff would cost me 12,276 THB, i.e. 3,960 THB less than A which is not negligible. The question is : is there a compelling reason I should chose A = SCG rather than B = Sunshield and fork out those extra 3,960 THB?

 

[itsari]

You need plenty of airflow in the roof space above the ceiling before you need to think of insulation .

[JAS21]

Your suggesion #1 can be bad news ... I have seens several times where this insulation un-glues itself and its very noisy when it rains.

 

We had build a cover over our driveway and also a shed. We used a company called Hollo Roof, they have a very good produce ... it doesnt appear to allow much heat transfer AND reasonably quite when it rains. Various colours. UPVC In Bang Bua Thong, Nonthaburi if I remember correctly.

 

Just google for info. Sheets are not exactly cheap, but very easy to fit yourself.    

 

edit ... I now see that a somewhat similar?  product is being produced in China .....

[gejohesch]

1 hour ago, itsari said:

You need plenty of airflow in the roof space above the ceiling before you need to think of insulation .

We already have installed those sort of screens (looks like slatted windows a bit) on the gables (there are 2 gables on the roof in question). The screens that one can find anywhere in Thailand, in all-made kits, made out of wood. So that already allows some airflow, to some extent. I'm aware that it would be ideal to have an outlet higher up, by the roof ridge - something like a turbine vent - but maybe we can wait to see if we really need one and, if necessary (i.e. we still have an insulation problem after replacing the roofing sheets and placing the insulation batts), put one in place at a later stage to improve the air circulation?

Edited February 4, 2022 by gejohesch
forgot sthg

[gejohesch]

1 hour ago, JAS21 said:

Your suggesion #1 can be bad news ... I have seens several times where this insulation un-glues itself and its very noisy when it rains.

 

We had build a cover over our driveway and also a shed. We used a company called Hollo Roof, they have a very good produce ... it doesnt appear to allow much heat transfer AND reasonably quite when it rains. Various colours. UPVC In Bang Bua Thong, Nonthaburi if I remember correctly.

 

Just google for info. Sheets are not exactly cheap, but very easy to fit yourself.    

 

edit ... I now see that a somewhat similar?  product is being produced in China .....

Hmmm, thanks for the feedback. Have to ask again the factory, and our builder (we have a very good one, based on past experience) if they think there could be a problem with the "ungluing" you mention.

[Klonko]

Solution 2 on the ceiling reduced temperature in our hose by 3-6°C.  The hot air can circulate through the roof tiles.

 

I would organize/buy a meter to measure temperatures on walls, windows and ceilings before making a decision. In our case, the one glassed windows had  the same temperature like the walls but the ceiling was up to 6°C warmer.  Avoiding direct sun exposure of walls and windows also makes a big difference. Roof extensions pay off. 

Edited February 4, 2022 by Klonko
Typos

[CharlieH]

MOVED TO DIY

[4MyEgo]

23 minutes ago, gejohesch said:

I'm aware that it would be ideal to have an outlet higher up, by the roof ridge

I call them whirly birds, have two and they work 24/7 spinning around most of the day, they are great at extracting excess hot air trapped in the roof.

 

The stuff you mention under the roof sheets is to stop the crackling of the roof sheets in the heat, if you do not put in a decent product of sisalation under the roof sheets, then the heat will just come straight in from your roof sheets, so in effect you are reducing the time it takes for the heat to enter into the ceiling space using sisalation.

 

The ceiling batts in your picture are fine, I have the highest rating ones, I believe they are R38 if memory serves me correct, and the higher the rating, the thicker the sheeting so as to also reduce the heat time coming down to your living areas.

 

You might also consider white roof sheeting, as boring as they sound, it does deflect the heat, that and painting any rendered walls white, again to deflect the heat, on top of that, shade clothes are good around the walls that get that afternoon sun.

 

We rarely turn on any air conditioners during the day, at night for 20 minutes tops then allow the fan to take over, if you do it right the first time, you will enjoy the comfort of being cool within the house, but it all depends on how much your prepared to spend to be comfortable.

[OneMoreFarang]

Just in case you think about this option...

 

[DaLa]

 

 

 

Used this in our new shop. No idea if it works as we ended up with a wall of glass down one side ( it appears customers like to window shop here too) and ended up with a great greenhouse.

 

[bankruatsteve]

For the insulation... it's the reflective quality that will help most.  The thickness is insignificant, IMO.  Our upper rooms used to get quite hot from conduction from the attic space.  I covered with reflective bats 5 years ago and the ceilings no longer conduct heat.

[Cake Monster]

I used some of this Insulation Foam quite a while back, and found it to be not what was described.

Firstly, I must say that I cannot remember the exact product name, as I said, it was a while ago.

The " Aluminium Foil " on the outerside of the Foam - was not.

It was a layer of thick paper that was painted Silver

Check this out before you buy, as the paper degrades very quickly.

[sometimewoodworker]

40 minutes ago, OneMoreFarang said:

Just in case you think about this option...

 

That criticism is relevant in the U.K. where wood is extensively used and houses are commonly bought second hand also maintain their value. Here neither is true wood is not used in most roofing and the market for used houses is small and the value almost always drops over time.

A relevant criticism is the cost of spray insulation compared to other forms.

Edited February 4, 2022 by sometimewoodworker

[pagallim]

7 minutes ago, sometimewoodworker said:

That criticism is relevant in the U.K. where wood is extensively used and houses are commonly bought second hand also maintain their value. Here neither is true wood is not used in most roofing and the market for used houses is small and the value almost always drops over time.

A relevant criticism is the cost of spray insulation compared to other forms.

Agreed, here it's typically galvanised steel frame and cement tiles.   I had spray foam installed in our place some 7 years ago and it's proved excellent.   We had no previous leaks anyway, but the foam has effectively locked the tiles in position.

 

[itsari]

1 hour ago, gejohesch said:

We already have installed those sort of screens (looks like slatted windows a bit) on the gables (there are 2 gables on the roof in question). The screens that one can find anywhere in Thailand, in all-made kits, made out of wood. So that already allows some airflow, to some extent. I'm aware that it would be ideal to have an outlet higher up, by the roof ridge - something like a turbine vent - but maybe we can wait to see if we really need one and, if necessary (i.e. we still have an insulation problem after replacing the roofing sheets and placing the insulation batts), put one in place at a later stage to improve the air circulation?

In my opinion do more with the airflow before insulation . More air flowing the cooler the roof space will be .

[Kwasaki]

Put a reflective product to underside of roof area. 

Then line the underside with suitable board material. 

Lay fibreglass / rockwool minimum of 10cm thick over area of room ceiling areas. 

Job done. 

You have vented gable ends good. 

[bankruatsteve]

1 hour ago, itsari said:

In my opinion do more with the airflow before insulation . More air flowing the cooler the roof space will be .

Ventilation is necessary and does help. But, no amount of ventilation, even with fans or whatever, is going to cool an attic space in 40C ambient. Reflecting the radient and convection works best for underlying space. 

[itsari]

6 minutes ago, bankruatsteve said:

Ventilation is necessary and does help. But, no amount of ventilation, even with fans or whatever, is going to cool an attic space in 40C ambient. Reflecting the radient and convection works best for underlying space. 

Air flowing through the roof space is far superior to insulation in a tropical climate . That has been my experience 

[Kwasaki]

28 minutes ago, itsari said:

Air flowing through the roof space is far superior to insulation in a tropical climate . That has been my experience 

Air flow through roof with insulation also on the ceiling is my experience along with noise insulation.

[gejohesch]

3 hours ago, Klonko said:

Solution 2 on the ceiling reduced temperature in our hose by 3-6°C.  The hot air can circulate through the roof tiles.

 

I would organize/buy a meter to measure temperatures on walls, windows and ceilings before making a decision. In our case, the one glassed windows had  the same temperature like the walls but the ceiling was up to 6°C warmer.  Avoiding direct sun exposure of walls and windows also makes a big difference. Roof extensions pay off. 

Roof extensions : indeed, and that's also part of the plan!

[gejohesch]

3 hours ago, 4MyEgo said:

I call them whirly birds, have two and they work 24/7 spinning around most of the day, they are great at extracting excess hot air trapped in the roof.

 

The stuff you mention under the roof sheets is to stop the crackling of the roof sheets in the heat, if you do not put in a decent product of sisalation under the roof sheets, then the heat will just come straight in from your roof sheets, so in effect you are reducing the time it takes for the heat to enter into the ceiling space using sisalation.

 

The ceiling batts in your picture are fine, I have the highest rating ones, I believe they are R38 if memory serves me correct, and the higher the rating, the thicker the sheeting so as to also reduce the heat time coming down to your living areas.

 

You might also consider white roof sheeting, as boring as they sound, it does deflect the heat, that and painting any rendered walls white, again to deflect the heat, on top of that, shade clothes are good around the walls that get that afternoon sun.

 

We rarely turn on any air conditioners during the day, at night for 20 minutes tops then allow the fan to take over, if you do it right the first time, you will enjoy the comfort of being cool within the house, but it all depends on how much your prepared to spend to be comfortable.

Thanks for all this.

 

[I call them whirly birds, have two and they work 24/7 spinning around most of the day, they are great at extracting excess hot air trapped in the roof.]

Whirly birds : yes, exactly. I’m really thinking about getting at least 1 to install when replacing the roof sheets. And indeed, choice of colours : either white or a very light cream colour. And indeed, we are also painting everything around with very light colours as they reflect heat better.

 

 [The stuff you mention under the roof sheets is to stop the crackling of the roof sheets in the heat, if you do not put in a decent product of sisalation under the roof sheets, then the heat will just come straight in from your roof sheets, so in effect you are reducing the time it takes for the heat to enter into the ceiling space using sisalation.]

I don’t really understand that. Especially the bit about “reducing the time it takes for the heat…. etc”

 

[The ceiling batts in your picture are fine, I have the highest rating ones, I believe they are R38 if memory serves me correct, and the higher the rating, the thicker the sheeting so as to also reduce the heat time coming down to your living areas.]

Do you mean that the higher the rating (Rt), the more heat transmission down there will be?

 

 

[You might also consider white roof sheeting, as boring as they sound, it does deflect the heat, that and painting any rendered walls white, again to deflect the heat, on top of that, shade clothes are good around the walls that get that afternoon sun.]

Choice of colours : I agree, as said above. And I don't see any issue with "boring white", we do not see the roof from above after all, hahaha!

Shades etc : we are already building roof extensions and arranging plants and bushes where possible to add shade as much as possible.

 

 

[We rarely turn on any air conditioners during the day, at night for 20 minutes tops then allow the fan to take over, if you do it right the first time, you will enjoy the comfort of being cool within the house, but it all depends on how much your prepared to spend to be comfortable.]

A little AC supplemented by fans : yes, that’s the way we like doing it. We never liked having the AC’s on during the night, we don’t find them comfortable.

[gejohesch]

3 hours ago, Cake Monster said:

I used some of this Insulation Foam quite a while back, and found it to be not what was described.

Firstly, I must say that I cannot remember the exact product name, as I said, it was a while ago.

The " Aluminium Foil " on the outerside of the Foam - was not.

It was a layer of thick paper that was painted Silver

Check this out before you buy, as the paper degrades very quickly.

Thanks, good advice indeed as there is a lot of "talking bigger than what it actually is" in this country (at least that's my opinion...)

[gejohesch]

2 hours ago, itsari said:

In my opinion do more with the airflow before insulation . More air flowing the cooler the roof space will be .

Sure. Thinking of those "whirly birds"....

[gejohesch]

1 hour ago, itsari said:

Air flowing through the roof space is far superior to insulation in a tropical climate . That has been my experience 

Maybe that's correct, as I'm thinking of the rationale for those high pitched traditional roofs in Thailand, allowing hot air to move upwards, hence reducing the heat in the living areas.

[Kwasaki]

7 minutes ago, gejohesch said:

Maybe that's correct, as I'm thinking of the rationale for those high pitched traditional roofs in Thailand, allowing hot air to move upwards, hence reducing the heat in the living areas.

Also with any pitch roof and hip roof construction vented ridge tiles and vented hip tiles help. 

[4MyEgo]

8 minutes ago, gejohesch said:

Whirly birds : yes, exactly. I’m really thinking about getting at least 1 to install when replacing the roof sheets. And indeed, choice of colours : either white or a very light cream colour. And indeed, we are also painting everything around with very light colours as they reflect heat better.

That's the way, now if you have a gable roof, one whirly bird on each opposite side of the roof, and away from each other is the way to go, say like 3 metres apart on the opposite side which will allow a wind tunnel effect so to speak. This would be backed up with one of those saloon type looking wooden slats at the front just under the faced that helps the air push through if you know what I mean.

 

8 minutes ago, gejohesch said:

[The stuff you mention under the roof sheets is to stop the crackling of the roof sheets in the heat, if you do not put in a decent product of sisalation under the roof sheets, then the heat will just come straight in from your roof sheets, so in effect you are reducing the time it takes for the heat to enter into the ceiling space using sisalation.]

I don’t really understand that. Especially the bit about “reducing the time it takes for the heat…. etc”

Ok, so you can buy the roof sheets with that silver stuff under it, that stuff is only for stopping the noise from when the sheets expand in the heat, they make this crackling sound, so it stops it, but is not good for reducing the heat coming into the ceiling space from the roof sheets. Sisalation goes on before the roof sheeting goes on and Sisalation, depending on the quality helps to "delay" for a better word, the heat penetrating downwards from your roof sheets into the ceiling space below. "My bad for using "reducing" the time it takes for the heat to enter the ceiling", so it's the opposite. Sisalation helps to delay the heat entering into the ceiling. I have concrete tiles with the Sisalation under the roof tiles, sort of like a bubble wrap which is 3mm thick on the upside and 3mm thick on the bottom side, so it delays the heat entering from the concrete tiles once they heat up then enter under the roof tiles, the heat then has to work it's way through the Sisalation before it enters the ceiling space, and then it has to work it's way down through the ceiling batts, but not before the hot air is being pushed about by the air circulating through those saloon style looking panels and being sucked up by the whirly birds, sorry I don't have the name for those saloon style (fixed) door type wooden things, but if you look up at any gable roof you will see them sitting there.

 

All of the above said, I can stand easily in the middle of our ceiling space, so the more room you have, the better chances of the air leaving via the whirly birds.

 

9 minutes ago, gejohesch said:

Do you mean that the higher the rating (Rt), the more heat transmission down there will be?

The higher the (Rt) the thicker the batt is which helps slow the heat down, suffice to say if yours are say 27 (Rt), 38 (Rt) will be thicker and it will take longer for the heat in the ceiling space to work it's way down through the batt and then the ceiling.

 

9 minutes ago, gejohesch said:

Choice of colours : I agree, as said above. And I don't see any issue with "boring white", we do not see the roof from above after all, hahaha!

Shades etc : we are already building roof extensions and arranging plants and bushes where possible to add shade as much as possible.

Great stuff, we only have one single room at the front that the sun hits, albeit it is shaded by a tree at times, the rest, extensions on every wall, bar one which the sun doesn't see and they are all the bedroom and bathroom walls.

 

9 minutes ago, gejohesch said:

A little AC supplemented by fans : yes, that’s the way we like doing it. We never liked having the AC’s on during the night, we don’t find them comfortable.

The Sisalation, along with the batts, the whirly birds and the eaves do there jobs better than I expected, that said, we have air cons in every room, the girls room we leave it on at 26 which is a nice feel and is big enough for them not to wake up with dry eyes, sore throats and the like, ours will as mentioned only be on for 20 minutes and then the fan will take over, and sometimes the wife will want it on all night, that is when she will go and sleep with the girls, no issues as she knows I don't like to sleep with the air con unless it's absolutely necessary. 

[4MyEgo]

1 hour ago, itsari said:

Air flowing through the roof space is far superior to insulation in a tropical climate . That has been my experience 

I went one year without insulation batts to see if the whirly birds were enough for moving the air out, I knew this wouldn't work 100% because heat also travels downwards if and when there isn't any air movement, but thought I would give it a go.

 

The Sisalation worked well, but after 10am in the morning in this Isaan Thai summer, the air cons had to go on, but once I installed the whirly birds, i.e. on the very hottest days, I would crank them on at around 2pm-3pm, one air con at the front of the house and one at the back of the house for about an hour at the same time and closing off doors around the house and setting up fans to force the air along in the same direction, front to back and back to front, we have a house which is long, about 40 walking steps to reach the back from the front, and then off after about an hour and the place would be cool enough till it was bed time, i.e. and as mentioned in another post, 20 minutes of air con in the bedroom, then the fan would take over, but without ceiling batts, air cons would have to be on at night at the cool air disappears into the ceiling space, whereas having batts pushes the cool air back down into your room, hence the reason the air cons only on for 20 minutes and the fan then circulates that cool air around for the night. 

[gejohesch]

8 hours ago, 4MyEgo said:

That's the way, now if you have a gable roof, one whirly bird on each opposite side of the roof, and away from each other is the way to go, say like 3 metres apart on the opposite side which will allow a wind tunnel effect so to speak. This would be backed up with one of those saloon type looking wooden slats at the front just under the faced that helps the air push through if you know what I mean.

 

Thanks for all this feedback. I have a question re. the whirly birds. My roof ridge from gable to gable, is 7 metres : could I get away with only 1 whirly bird in the middle, or should I rather think of 2 whirly birds, one at each end?

 

 

The "saloon type windows" : I know what you're talking about. These are the "slatted windows" I mentioned earlier. They are made of wood and can be bought in kits anywhere in Thailand, costs somewhere like 1500 - 2000 THB a piece if I remember right. We have 2 in place, one at each gable. I had them painted with teak colour paint and they look great.

 

The height from the ceiling to the roof ridge is 1.4 metre, we can definitely not stand up. I hope that's enough to make the "slatted windows / saloon style" + whirly bird (1 or 2?) effective nonetheless.

Edited February 4, 2022 by gejohesch
adding a line

[gejohesch]

8 hours ago, 4MyEgo said:

Great stuff, we only have one single room at the front that the sun hits, albeit it is shaded by a tree at times, the rest, extensions on every wall, bar one which the sun doesn't see and they are all the bedroom and bathroom walls.

Another good reason for roof extensions where possible is protection against the rain. With the heavy rains we get here, often enough, I find the house walls end up soaking up the humidity and it shows with the paint deteriorating even on the inside of the house.

 

Also, we've got a lot of wooden stuff around the house, terraces connecting to another house etc, they are all roofed up but I get worried part of the wood ends up being damaged after a few years. Obviously, heat and rain end up being a major recurrent issue around in Thailand!

[gejohesch]

8 hours ago, 4MyEgo said:

The higher the (Rt) the thicker the batt is which helps slow the heat down, suffice to say if yours are say 27 (Rt), 38 (Rt) will be thicker and it will take longer for the heat in the ceiling space to work it's way down through the batt and then the ceiling. 

I see recommendations for attic insulation in the USA : What R-value Do I Need? | Johns Manville (jm.com) Obviously, it would not be straightforward to compare between any US state and Thailand, however I find it interesting that the USA recommendations vary between Rt 30 and Rt 60 (increasing from south to north). 

Coming back to the 2 options I described in my OP:  "Material A is SCG "Stay Cool Green-3 Insulation - Rt 27" at 369 THB per roll. Material B is Sunshield "Extra Cool - Rt 37" at 279 THB per roll"

I find it strange that the material with the higher Rt value (A) is also the cheaper. Maybe it's the quality of the material, apart of the Rt value? Maybe I'm missing sthg in the specs? Not knowing better, I would opt for Sunshield at Rt 37 since it is cheaper and has the higher Rt factor.