New roof advice

[simoh1490]

Also re. RB: I just cut a piece off (I couldn't tear it) and I held it over a gas flame. One side burned off, the other side which is silver foil remained intact and didn't burn - the side with the raised lines in it remained, the smooth side burned, I guess it's the first one must be considered to be the shiny surface.

[wayned]

47 minutes ago, Kwasaki said:

Just quick sketch to explain exploded one @ post #293.

If you look at the picture of the existing structure, it looks like the existing purlins/battens are 3 x 1.5 "C" section.  The short side, where the spacer would be attached, is effectively 1.25" wide, so if you use hat sections as pictured I think that they would have to be "custom" made as I don't think that they are readily available premade.  If they need to be custom made, and that's how the roof is going to be attached it's something the Sheryl could have them fabricating now while they are waiting for the roofing. Also, I would use screws on both side of the "hat" section to secure it to the batten.

[Sheryl]

SIMOH: Probably best to assume I know next to nothing .[emoji1]

 

I will return the 2 unopened rolls and use the opened one in the garden shed. Bummer...it was the most expensive foil they had at DO Home. Maybe better to stick with Home Pro brands.

 

For what it's worth I managed to get an answer to the "which side" question from the company that makes it. Answer was, smooth side towards the roof.

 

 

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[simoh1490]

Definitely, screws on both sides of the top hat are essential.

 

And yes, Sunshield from Hompro is very good.

[Sheryl]

If you look at the picture of the existing structure, it looks like the existing purlins/battens are 3 x 1.5 "C" section.  The short side, where the spacer would be attached, is effectively 1.25" wide, so if you use hat sections as pictured I think that they would have to be "custom" made as I don't think that they are readily available premade.  If they need to be custom made, and that's how the roof is going to be attached it's something the Sheryl could have them fabricating now while they are waiting for the roofing. Also, I would use screws on both side of the "hat" section to secure it to the batten.

The purlins are 3 x 2 so I think commercially bought spacer should work?

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[Sheryl]

I have a quick question about the above drawing. The new roof sheets will be attached to the "suitable spacers with the screws supplied.  How are the new spacers going to be attached to the existing purlins once the RB is installed?  Just a question as I don't think that "long" screws is the answer to get the spacing needed between the RB and the roof panels.

I was under the impression that the spacer alone would provide sufficient spacing and we'd just use short screws to affix the spacers to the purlins (screws passing thru the RB). Is that not the case?

 

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[wayned]

12 minutes ago, Sheryl said:

The purlins are 3 x 2 so I think commercially bought spacer should work?

As I said, I don't know if hat sections are available with the correct dimensions to fit the short side of the 3 x 2  "C" section.  Attaching them to the battens with short screws is fine as long as they have screws on both sides of the "top hat"!

[carlyai]

Here's some of the article from the reflective foil thread, which I have downloaded but can't open in TV.

"We examined, tore, ripped, stretched and burned the samples from Chang and OHO and could detect no difference at all between them other than the 2000 baht price. They really do look as if they came off exactly the same production line and I can't think of any way to justify buying the more expensive of the two.

The Cool Guard was so much stronger and easier to handle that it was the clear winner so that's one we're going with, although I think we will end up fitting it over the purlines and letting it sag between them as much as is practical to provide the air gap.

 

 

• It acts in two ways: (1) the side facing the roof reflects a proportion of the heat that builds up in your roof material and (2) the side that faces into the roof space emits less radiant heat because it is shiny.
  
  In order to work properly, there must be an air gap between the tiles and the reflective material. Where the hot tile touches the foil, heat is simply conducted and the benefit of the reflective surface is lost although it will still emit less than the tile would alone.

The last point is the tricky one, given Thai building techniques, and my guess is that the vast majority of installations get much less value for their spend on this material than if the contractors, owners and architects really knew the principles of radiant barriers (that's the thing to Google, btw). I have spent much of the last couple of days trying to devise a workable way to apply the material to the underside of either the purlines or the rafters (preferable) but so far without success. I can figure out how you could do it on a simple roof but ours is complex and I don't see the contractor's people being able to cope.

SCG has tackled this issue in two ways. Firstly, if you buy their expensive but attractive galvenised bolt together roofing system, the foil is placed over the rafters and the purlines bolted on top, leaving a very nice gap of about two inches. True, the part where the purline touches the foil will be ineffective as far as reflecting the radiant heat goes but then the rafter is directly below so it's really out of the running anyway. If you want to see this, go to your local HomeExpert branch and take a look at the mock up of their fancy roofing system. The second way is something I've not actually seen but I understand they have launched a foil product which is shaped so that it hangs down between the purlines in a controlled way, rather than just being fitted with a sag to try to create the air gap. I'm told this is even more expensive that the Chang brand reflective foil

The excellent diagram below is how I would like to have arranged it but it will have to wait for the next project!"

 

 

[Sheryl]

Quick question re RB -- I am standing in HomePro now. They have Sunshield brand. Comes in 1 ply and 2 ply. Which do I want? The stuff I bought previously (Nash brand) was 2 ply and I think that was why the paper in the middle so thinking just 1 ply?

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[simoh1490]

1 minute ago, Sheryl said:

Quick question re RB -- I am standing in HomePro now. They have Sunshield brand. Comes in 1 ply and 2 ply. Which do I want? The stuff I bought previously (Nash brand) was 2 ply and I think that was why the paper in the middle so thinking just 1 ply?

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The Sunshield I bought from Homepro is very strong and it's only one ply, until you burn it that is (see above), there's definitely no brown paper in the middle and it's not possible to separate the layers by hand, I imagined it was one ply......so the answer is.....one ply!

[simoh1490]

1 hour ago, carlyai said:

Here's some of the article from the reflective foil thread, which I have downloaded but can't open in TV.

"We examined, tore, ripped, stretched and burned the samples from Chang and OHO and could detect no difference at all between them other than the 2000 baht price. They really do look as if they came off exactly the same production line and I can't think of any way to justify buying the more expensive of the two.

The Cool Guard was so much stronger and easier to handle that it was the clear winner so that's one we're going with, although I think we will end up fitting it over the purlines and letting it sag between them as much as is practical to provide the air gap.

 

 

• It acts in two ways: (1) the side facing the roof reflects a proportion of the heat that builds up in your roof material and (2) the side that faces into the roof space emits less radiant heat because it is shiny.
  
  In order to work properly, there must be an air gap between the tiles and the reflective material. Where the hot tile touches the foil, heat is simply conducted and the benefit of the reflective surface is lost although it will still emit less than the tile would alone.

The last point is the tricky one, given Thai building techniques, and my guess is that the vast majority of installations get much less value for their spend on this material than if the contractors, owners and architects really knew the principles of radiant barriers (that's the thing to Google, btw). I have spent much of the last couple of days trying to devise a workable way to apply the material to the underside of either the purlines or the rafters (preferable) but so far without success. I can figure out how you could do it on a simple roof but ours is complex and I don't see the contractor's people being able to cope.

SCG has tackled this issue in two ways. Firstly, if you buy their expensive but attractive galvenised bolt together roofing system, the foil is placed over the rafters and the purlines bolted on top, leaving a very nice gap of about two inches. True, the part where the purline touches the foil will be ineffective as far as reflecting the radiant heat goes but then the rafter is directly below so it's really out of the running anyway. If you want to see this, go to your local HomeExpert branch and take a look at the mock up of their fancy roofing system. The second way is something I've not actually seen but I understand they have launched a foil product which is shaped so that it hangs down between the purlines in a controlled way, rather than just being fitted with a sag to try to create the air gap. I'm told this is even more expensive that the Chang brand reflective foil

The excellent diagram below is how I would like to have arranged it but it will have to wait for the next project!"

 

 

You can achieve the same end by installing vents in the gable ends instead of the ridge line vents, which I think is what most people do. Regardless of whether you have the vent at the ridge or at the gable, it wont work unless you get the air intake part to work. BTW nice house picture, well done.

[Sheryl]

The Sunshield I bought from Homepro is very strong and it's only one ply, until you burn it that is (see above), there's definitely no brown paper in the middle and it's not possible to separate the layers by hand, I imagined it was one ply......so the answer is.....one ply!

Does it look like this? I'm concerned because this looks exactly like what I got before



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[simoh1490]

Just now, Sheryl said:

Does it look like this? I'm concerned because this looks exactly like what I got before



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Yes, that's almost exactly the same as I purchased, guaranteed there's no brown paper in it and guaranteed it's very strong. Maybe see if the sales staff will let you open a roll to check it out.

[Sheryl]

Already asked answer no. Going ahead and buying 1 roll.

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[simoh1490]

1 minute ago, Sheryl said:

Already asked answer no. Going ahead and buying 1 roll.

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Perhaps buy it, take it outside and open it, satisfy yourself that it's kosher then go back and buy the rest?

[Sheryl]

I'm baffled. This has brown paper backing. And it can be easily torn.

It looks exactly like what I bought before except being 2 ply that had a second layer attached to the other side of the brown paper and with a smooth surface.

What am I missing hete? I seem to be buying what is supposed to be the right product but it looks and feels different from what you all describe.



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[simoh1490]

Is the brown paper an actual backing or is it there to separate the foil as it is rolled up? Is the brown paper actually attached to the foil is what I'm asking?

 

And can the foil be easily torn or does it take some effort?

[simoh1490]

The foil covering the fibreglass insulation is very easily torn both through handling and certainly, when laying, the RB is by comparison much much stronger. I can tear if I try but it's not something that will easily rip or tear if snagged.

 

From what I see from your photo's of the RB, it looks almost identical to what I have.

 

The existence of the brown paper makes no sense to me and I've never seen it before, unless it's something that serves as packing material and is layered into the roll to protect the surfaces, is that possible?

 

 

[Sheryl]

I have not fully unfurled the rolls but the brown paper seems quite securely fastened to the foil. In the case of the 2 ply it is in between the 2 plys. It is impossible to separate it from the foil, it is a backing.

 

The first one  tore accidently as I removed the tape holding to roll shut. The second, I tore deliberately but could very easily do so with bare hands working form the edge of it.

 

Seems what I bought in both instances is not in fact what you have then. But it is the only thing that was available at either Home Pro of DO Home.

 

I'm really at a loss now how to source the right thing.

[Kwasaki]

4 hours ago, wayned said:

If you look at the picture of the existing structure, it looks like the existing purlins/battens are 3 x 1.5 "C" section.  The short side, where the spacer would be attached, is effectively 1.25" wide, so if you use hat sections as pictured I think that they would have to be "custom" made as I don't think that they are readily available premade.  If they need to be custom made, and that's how the roof is going to be attached it's something the Sheryl could have them fabricating now while they are waiting for the roofing. Also, I would use screws on both side of the "hat" section to secure it to the batten.

 You question was answered if you study the sketch the problem on these type of threads is that participants don't really study and look at detailed sketches for any length of time because they only convincingly think about what they think is correct roof build.

[Kwasaki]

4 hours ago, simoh1490 said:

Also re. RB: I just cut a piece off (I couldn't tear it) and I held it over a gas flame. One side burned off, the other side which is silver foil remained intact and didn't burn - the side with the raised lines in it remained, the smooth side burned, I guess it's the first one must be considered to be the shiny surface.

Sorry buddy but this sort of thing your going on about is just sales hype there are many other-ways to insulate roof areas in construction.

[Sheryl]

I think that is not the point here. I want to put in a radiant barrier. I am trying to source it. What I have now twice bought seems not to be the same as what others have used and what I am seeing in videos, and we're trying to sort out why so I can get the right thing.

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[simoh1490]

5 minutes ago, Kwasaki said:

Sorry buddy but this sort of thing your going on about is just sales hype there are many other-ways to insulate roof areas in construction.

I don't understand what you wrote here or why.

[simoh1490]

2 minutes ago, Sheryl said:

I think that is not the point here. I want to put in a radiant barrier. I am trying to source it. What I have now twice bought seems not to be the same as what others have used and what I am seeing in videos, and we're trying to sort out why so I can get the right thing.

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I don't have an answer for this, the RB I have is Sun Shield (or similar) from Homepro and it's three years old, I find it hard to believe they've changed the manufacturing process that much. 

 

Worst case scenario, if you can't account for the differences, you have two rolls of RB so use it, the fact that it's different from what's been described here may not be that significant - the brown paper however, I really don't know what to do about that.

[Kwasaki]

4 hours ago, wayned said:

If you look at the picture of the existing structure, it looks like the existing purlins/battens are 3 x 1.5 "C" section.  The short side, where the spacer would be attached, is effectively 1.25" wide, so if you use hat sections as pictured I think that they would have to be "custom" made as I don't think that they are readily available premade.  If they need to be custom made, and that's how the roof is going to be attached it's something the Sheryl could have them fabricating now while they are waiting for the roofing. Also, I would use screws on both side of the "hat" section to secure it to the batten.

That's why if as always if people just took time to study the 2 options of roof spacer they can adapt and continue with the re-roof.

[Sheryl]

I don't have an answer for this, the RB I have is Sun Shield (or similar) from Homepro and it's three years old, I find it hard to believe they've changed the manufacturing process that much. 
 
Worst case scenario, if you can't account for the differences, you have two rolls of RB so use it, the fact that it's different from what's been described here may not be that significant - the brown paper however, I really don't know what to do about that.

The problem is that I don't think what I have is remotely sturdy enough or thick enough aluminum to use as an RB. You can scratch the surface and the brown paper shows through.

The only thing I can think of is that what I have and have wasted some 6,000 baht on is actually the wrapping that goes around fiber glass insulation. Why they would cell 60 meter rolls if it, I have no idea. It was on the shelves in the same area as the insulation batts and there was nothing else by way of rolls of aluminum foil but this. 2 different brands, Nash at DO Home and Sunshield at HomePro. Both are extremely thin aluminum glued tightly to brown paper.


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[Kwasaki]

4 hours ago, simoh1490 said:

Definitely, screws on both sides of the top hat are essential.

 

And yes, Sunshield from Hompro is very good.

So that is why a Zed spacer is used if the existing channel purlins do not accommodate a spacer that need fixing alternate sides.

AS SHOWN IN A POST SKETCH.

[simoh1490]

1 minute ago, Sheryl said:

 

The problem is that I don't think what I have is remotely sturdy enough or thick enough aluminum to use as an RB. You can scratch the surface and the brown paper shows through.

The only thing I can think of is that what I have and have wasted some 6,000 baht on is actually the wrapping that goes around fiber glass insulation. Why they would cell 60 meter rolls if it, I have no idea. It was on the shelves in the same area as the insulation batts and there was nothing else by way of rolls of aluminum foil but this. 2 different brands, Nash at DO Home and Sunshield at HomePro. Both are extremely thin aluminum glued tightly to brown paper.


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I just googled radiant barrier brown paper backing and there's lot of pictures out there of it but no explanation why it's made that way.

 

I've just looked again at the roll of RB I have nearby, remember it's 3 years old. It has two layers as said previously, one is silver foil that will not burn, the other is a paper of some sort that does burn but it's not obvious from looking at it that it is paper - the two layers are very firmly bonded together and only separate when burnt.

 

I'm wondering if it's possible that they have changed the manufacturing process and replaced the silver paper layer that I see with the brown paper layer you now see?

 

As for sturdiness: if I try to poke my finger through the RB I can't and I'm fairly strong, can you?

[Kwasaki]

10 minutes ago, Sheryl said:

 

The problem is that I don't think what I have is remotely sturdy enough or thick enough aluminum to use as an RB. You can scratch the surface and the brown paper shows through.

The only thing I can think of is that what I have and have wasted some 6,000 baht on is actually the wrapping that goes around fiber glass insulation. Why they would cell 60 meter rolls if it, I have no idea. It was on the shelves in the same area as the insulation batts and there was nothing else by way of rolls of aluminum foil but this. 2 different brands, Nash at DO Home and Sunshield at HomePro. Both are extremely thin aluminum glued tightly to brown paper.

 

Your started to understand the sales hype crap at last if you can forgive me for saying so.

I try to refrain from upsetting people.

 

[simoh1490]

From what I've read this evening, nearly all RB's have a kraft layer and a foil layer, it's the foil layer that must face the attic floor. All of them having a kraft paper coating is consistent with what we know about the two RB products we've seen, the one I have and the one you've just purchased. When I said I burnt mine over a stove and one side burned, what burned was the kraft paper albeit it didn't look like paper.

 

Sooo, it sounds like they have changed the manufacturing process and the appearance of the product. On that basis, you have purchased RB so I recommend you use it.