metal roofing and reflective foil

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Re: metal roofing and reflective foil

Postby Sometimewoodworker » Mon Apr 28, 2014 5:32 pm

Mike Judd wrote:Re the clip method of fixing steel sheeting , I used on my factory in Sydney and it was the usual C sections as purloins spaced 1.2 mts apart with the clips fixed with the correct self tappers for what ever thickness of steel you are using, then the Cliplock sheeting just presses into the clips. There is no way they will blow off except maybe in a Hurricane when the whole building is blowing apart.

True if you have walls and celling. not so true if you just have the roof. as we do with the waterhouse and sunshade
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Re: metal roofing and reflective foil

Postby sirineou » Mon Apr 28, 2014 11:16 pm

Cheeryble wrote:
sirineou wrote:Ok so what you are considering is called a "Vaulted ceiling", and you want to do this so that you can access the area that would ordinarily be attic space and use it as a loft space.

In the west there is a vary simple and inexpensive way to vent the roof space between the rafters, there are baffles made out of Styrofoam
Image
to allow for air movement, and create convection cooling
I dont think you could easily find these in Thailand as there is not much of a demand, but I am sure you could fabricate such a system out of tin, In fact a piece of metal roofing turned upside down would provide the necessary air space for convection.
then of course you insulate the remaining cavity with fiberglass insulation, so I am not sure if Styrofoam insulation is necessary.
Colorbond metal roofing has a clip system, I am sure other metal roofs have it also.
Image
Not necessary for wood strips, (termite food) there are metal strips designed for that use.
http://www.lysaght.com/roofing/klip-lok-406/how-to-install


Thanks for the thoughts Sirineou
Do you have a simple sketching application you could help me visualise the layers in the roof to show where the convection/ventilation layer would fit in? It would be much appreciated.

Thanks for the Colorbond link (though it speaks of screwing the clip into the purlin. Where I come from the purlin is a large cross beam which supports the rafters half way up.)
So what does one screw the clip into……directly into the member behind the gutter board as it looks like on the link? Oris there a tin strip or section such as one screws sheetrock into for a ceiling using those very sharp "grabber" screws?

Thanks!

Yea difficult to follow some times as we al come from different countries and use different terms
Purlins are simply metal strips running horizontally on the rafters.
mettal strips.JPG


these metal strips can screwed on by self tapping screws or can be welded on
self tapping screw.JPG

on these metal strips the color bond metal roof is installed, either being screwed on, or with the clip system. Under the roof between the rafters there will be a space, in that space you can put fiberglass insulation, To prevent the insulation of completely feeling that space and preventing air from circulating
you can place baffles to crate a free airspace trough which air can flow.
roof system.JPG
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Re: metal roofing and reflective foil

Postby Sometimewoodworker » Tue Apr 29, 2014 6:00 am

Cheeryble wrote:Sirineou I just looked again at the coffee shop roof (BTW this is not an exemplary roof it is more a terrace shelter).

I note the sheets are screwed DIRECTLY into the bottom batten/beam (which is moderately substantial at 4x2in steel).
This surprises me as surely it would need a hole drilled specially through the steel for every hole.
Is this the normal arrangement and one screws the clips directly on?


The guides and manuals under will answer your questions

http://www.lysaght.com/files/dmfile/LysaghtRoofingWallingInstallationManualDec13v4.pdf
http://www.lysaght.com/files/dmfile/SupaPurlinsManualApril2013.pdf
http://www.lysaght.com/files/dmfile/LysaghtSupaPurlinsQuickSelectionGuideOpenFeb14.pdf
http://www.lysaght.com/files/dmfile/LysaghtArchitecturalDetailingManualRoofWallFlashingApril2014.pdf
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Re: metal roofing and reflective foil

Postby Cheeryble » Tue Apr 29, 2014 10:00 am

SometimeWW looked at yr Waterhouse......congrats.

In fact my little chalet will be in a worst case scenario for wind gust, on a fairly bare small hilltop above a big rice field area
However filling a roof with holes for screws seems ridiculous for the house, and as Mike Judd suggests if these roofs flew off no-one would buy them, and in any case I think I want them lined with some sort of ceiling or trim underneath so that should ease the force. (Though not sure about the covered verandah)
I think I'm opting for a long flat moderately sloped main roof (with a "lean to" on front for verandah) so metal with no horizontal seams seems intelligent and no more hailstone wrecking like they just had up there outside of Chiangrai.....though I did see a dented steel roof.

Is it safe?

Thanks to you both, and thanks STWW for the links I now have them all in iBooks ready for use.
BTW are all the colorbond sections I might need available here?
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Re: metal roofing and reflective foil

Postby Cheeryble » Tue Apr 29, 2014 10:12 am

sirineou wrote:
Cheeryble wrote:
sirineou wrote:Ok so what you are considering is called a "Vaulted ceiling", and you want to do this so that you can access the area that would ordinarily be attic space and use it as a loft space.

In the west there is a vary simple and inexpensive way to vent the roof space between the rafters, there are baffles made out of Styrofoam
Image
to allow for air movement, and create convection cooling
I dont think you could easily find these in Thailand as there is not much of a demand, but I am sure you could fabricate such a system out of tin, In fact a piece of metal roofing turned upside down would provide the necessary air space for convection.
then of course you insulate the remaining cavity with fiberglass insulation, so I am not sure if Styrofoam insulation is necessary.
Colorbond metal roofing has a clip system, I am sure other metal roofs have it also.
Image
Not necessary for wood strips, (termite food) there are metal strips designed for that use.
http://www.lysaght.com/roofing/klip-lok-406/how-to-install


Thanks for the thoughts Sirineou
Do you have a simple sketching application you could help me visualise the layers in the roof to show where the convection/ventilation layer would fit in? It would be much appreciated.

Thanks for the Colorbond link (though it speaks of screwing the clip into the purlin. Where I come from the purlin is a large cross beam which supports the rafters half way up.)
So what does one screw the clip into……directly into the member behind the gutter board as it looks like on the link? Oris there a tin strip or section such as one screws sheetrock into for a ceiling using those very sharp "grabber" screws?

Thanks!

Yea difficult to follow some times as we al come from different countries and use different terms
Purlins are simply metal strips running horizontally on the rafters.
mettal strips.JPG


these metal strips can screwed on by self tapping screws or can be welded on
self tapping screw.JPG

on these metal strips the color bond metal roof is installed, either being screwed on, or with the clip system. Under the roof between the rafters there will be a space, in that space you can put fiberglass insulation, To prevent the insulation of completely feeling that space and preventing air from circulating
you can place baffles to crate a free airspace trough which air can flow.
roof system.JPG


Thanks Sirineou

....above and beyond great pics.
As to the insulation:
I'm wondering if instead of a rockwool extra layer of insulation I might use that type of plasterboard (Sheetrock) which has stiff insulation bonded to one side.....I think it even has a layer of reflective film as well so it would double up on that.
Anyone know if the price is restrictive this is not an investment property it is for keeping so I'm watching the pennies a bit but will not be mean if needed.

To all you kind posters......anyone know an installer/supplier for these roofs in CHiangrai area?
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Re: metal roofing and reflective foil

Postby Sometimewoodworker » Tue Apr 29, 2014 10:40 am

Many of the items in the catalogue will probably be un available in Thailand the main roofing profile is here but other bits might not be.

The best insulation is PU foam as Fred has, second best is the foamed insulation applied in the factory as RR has others are less good but better than nothing.
I've just proved that silver foil will give a drop of 20degrees C at the hottest time of the day.
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Re: metal roofing and reflective foil

Postby Cheeryble » Tue Apr 29, 2014 4:29 pm

Thanks STwW

For readers elucidation I have answered my own question somewhat went to Global today.
They indeed have foam backed plasterboard it's polystyrene not urethane but quite thick maybe 6cm
BUT it's 1010 baht /sheet.
Happily there is foil backed plasterboard at 207bt/sheet which is certainly do-able the regular stuff after all is 140bt.

So I think a top layer of colourbond foil and insulated sheet metal roof on the rafter battens, then a bottom layer of foil plasterboard facing upwards under the rafter battens, and hopefully some ventilation in between will do a pretty good job.

Which raises the question, without venting ridge tiles....how to vent at the top?

Possible answer?
Put a horizontal collar tie near the top of each rafter maybe just a foot or so below the ridge, and board up to, and under this.
It would look well, a little bit of flat ceiling at the top, and the air coming up between the rafters would connect to this "tunnel" at the top, to be vented at the eaves.
Just thinking!

In fact I may not have a ridged roof but have a simple one-slab shape rectangular roof at an angle one way only.
In this case it could probably vent under the overhang at the top end.......have to fit something to keep the wildlife out.
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Re: metal roofing and reflective foil

Postby sirineou » Tue Apr 29, 2014 6:33 pm

Not putting fiberglass insulation inside the rafter cavity and using the styrofoam backed sheet rock (drywall)
might be a good option and will provide a space for air circulation,
But I wonder what is the R value for such system.
I would think that for drywall so close to the metal roof you would need a min of R11.
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Re: metal roofing and reflective foil

Postby oil » Sun May 11, 2014 4:11 pm

btw, you guys think it would be possible to get metal roofing / w. reflective foil for a round house in TH, or you guys thing it would be so utterly expensive that its better to make it square?
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Re: metal roofing and reflective foil

Postby fredlk » Sun May 11, 2014 4:25 pm

oil wrote: you guys think it would be possible to get metal roofing / w. reflective foil for a round house in TH

Yes, it's the same roofing, just fitted differently.
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Re: metal roofing and reflective foil

Postby thailazer » Mon May 12, 2014 8:33 am

fredlk wrote:
oil wrote: you guys think it would be possible to get metal roofing / w. reflective foil for a round house in TH

Yes, it's the same roofing, just fitted differently.

Might be tough to use the metal sheet for a round roof as the stamped ribs are parallel. I would go with the composite tiles that are available. They look great and can place radially fairly easily.
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Re: metal roofing and reflective foil

Postby fredlk » Mon May 12, 2014 8:50 am

thailazer wrote:Might be tough to use the metal sheet for a round roof as the stamped ribs are parallel.

I forgot about that little detail.
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Re: metal roofing and reflective foil

Postby jackbill10 » Thu Jun 22, 2017 1:21 pm

Traveler wrote:I hope I don't open a can of worms with this post, but the previous discussions about these materials were often only an exchange of opinions and beliefs, rather than actual facts based on physics.

Those who oppose metal roofing and try to argue with "clay tiles have been used for a thousand years and therefore must be better" seem to forget about a couple of important factors.

In which climate zones were those clay tiles used commercial roofer ?
Mostly in the mediterranean or continental climates, which don't have a high humidity around year and also have cold winters. Therefore those roofs had to deal with a different environment and can't be compared to roofs in the tropics.

What were the alternatives for roofing material a thousand years ago ?
Actually NONE, except maybe for some organic materials which aren't durable but cheap and therefore were used by the average Joe. All other available materials had a lot of disadvantages.

Additionally it's hardly an argument to say" it was always done that way".
Acting by this rule would prevent any progress and I wonder if they still light their houses at night with torches instead of using electric lights. Torches were also used thousands of years ago, electricity only about one hundred, but which is better ?

Aesthetics may be an argument but solely a subject one which everybody has to decide for himself. It doesn't affect the suitability of any material, it's just a personal opinion, (good or bad) taste. :D

On the other hand the expectations or views of others shouldn't guide your decisions. So if you believe you must use clay tiles instead of Colorbond ONLY because you believe your neighbours may expect it or will otherwise look down and you, then grow up, get some self respect and confidence.

You don't need to know much more about thermodynamics than what you may have learned in elementary school, it's no rocket science. Energy levels always equal out by traveling from high level to low level - or here from hot to cold. All you got to know is which ways it can take and how to block them as good as possible.
This is all very simple to understand just by common sense.

I totally agree with Itchy, who stated that any measure taken must fit into the overall concept.
But I disagree that it is desirable to raise convection and therefore foil should not be used.

I guess it's obvious that such behaviour is counterproductive. The logical consequence would be that any kind of insulation will reduce convection and should therefore be avoided.

Why should I allow higher temperatures in the roof to drive up convection just to bring in hot air from the outside ?
Isn't it better to keep the cool air inside rather than exchanging it with hot air ?

A rise of temperatures should be prevented at all stages and as "early" as possible. That's why shading the perimeter of your house with plants helps quite a lot as it reduces all three ways of heat transportation into your building. If the temperature under your roof will rise over the day, so will the convection. It should only do its job when necessary but not before.


metal roofing (Colorbond)
=========================

When we decide for a certain material we have to look in which environment the material is used and how good it fits into it, the costs involved, the availibility of the material and the knowledge of your workers. The best material may be reduced to rubbish if improperly installed or used.

In the tropics - where the temperatures and humidity are high, but the differences between day and night are low - it is best if not mandatory to use materials with low thermal mass. Clay tiles and concrete for example have a high thermal mass compared to metal. Due to this fact alone, metal roofing is already superior to them.
Additionally metal roofing is very light weight, resulting in lower costs for the supporting structure. It's also faster to install, again reduced costs. It's very durable too, hardly gives any room for leakages and may stop "cockroaches" of all sorts to enter via the roof (which is quite common in LOS).

Due to it's low thermal mass metal roofing won't stay hot very long and cools down quite fast at night, which results in lower temperatures in the below building. Isn't that what we want ?
Metal roofing - just like any other roofing material - will heat up in bright sunshine and radiate a fair part of the heat into the below building.

This is the point where we turn to ...


reflective foil
===============

There has been a huge misunderstanding why reflective foil should be used.

Let's have a short look at the involved physics.
Heat can be transported by three ways : convection, conduction and radiation.
Reflective foil adresses all three aspects.

Reflective foil creates a barrier for the hot air directly below your roof thus preventing it to mix up with the cooler air in your attic, so it can't neither conduct the heat to the air nor to your ceiling and into the rooms.

So what's left is radiation
The intensity of radiation largely depends on the surface. A shiny surface radiates less than a dark one.
This is the reason why the reflective side of the foil can face down, away from the heat source. It's not intended to reflect any heat radiation back to your roof but rather to not radiate itself. The low thermal mass of the foil adds up to this effect. The hot air above the foil can not conduct much of it's energy (=heat) to the foil, due to the low heat capacity of the foil.

Now you should also understand why it is mandotory to have a "gap" between the foil and any other material below it. It's not only because air is a good isolator but also because you would bring conduction back into the equation.

In short : reflective foil is a radiation barrier, widely available, light weight, easy to apply, very cost effective and cheap, without any disadvantages. What else can anybody wish for ?


Cheers


Hello
Metal roofs offer many benefits, including: Longevity. Metal roofs can last 40-70 years, depending on the material. Traditional asphalt roofing materials have an estimated life expectancy of roughly 12-20 years.
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Re: metal roofing and reflective foil

Postby Sometimewoodworker » Thu Jun 22, 2017 1:42 pm

jackbill10 wrote:Hello
Metal roofs offer many benefits, including: Longevity. Metal roofs can last 40-70 years, depending on the material. Traditional asphalt roofing materials have an estimated life expectancy of roughly 12-20 years.

We are not in the USA so asphalt is not a traditional roofing material.

Probable spammer ? :twisted:
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Re: metal roofing and reflective foil

Postby Andyfteeze » Fri Jun 23, 2017 8:23 pm

Oh yes definitley metal roofing lasts a long time, in Australia. Here in thailand, not so much. The reason being, you cant get the same quality here retail.
Reading on from early on in the post, an assumption was made, no insulation is used to compare thermal performance. Thus based purely on the materials basic nature, a roofing material was specified.
I have a concrete roof on my new build. I also put 100mm of foam on top. Its as cool as anything inside, thats without windows and doors still. So to me, its not the actual basic material you use, its how you use it. Tin would be ok with lots of insulation underneath, same as tiles.
I chose concrete because it will outlast all the rest, its easy to maintain, wont look shabby in three years time . Other side benefits, vermin cant nest in it , it gives me sophisticated passive cooling plus i have an extra 65m2 of open usable space
The foam itself is protected with multiple layers of water proof membrane with fiberglass mesh layers. When this wet weather finishes it will be tiled with whitish tiles on swimming pool grade tile adhesive ( crocodile red). The foam is in effect sealed from the environment.
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