New roof advice

[Sheryl]

21 minutes ago, Kwasaki said:

1. Not necessarily true,  weight of old panel verse new as your outbuilding.

2. Quote...Battens (?purlin) are 1 meter distance apart and measure 3 x 2 inches. Unquote.  What material  ?

3.. Quote...   (I already did this replacement on a small garden shed) state it is the same or lighter. I will try to get specific though.  Unquote. 

The l would say they are probably right but still check to see what is the difference if any.

4.  Your Question:  from the above, does it sound like installing a newer fiber cement tile would be an issue? ......l would say no problem providing existing purlins if steel, battens if wood are OK.

5. ( R rating ) An insulating material's resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value -- the higher the R-value, the greater the insulating effectiveness. The R-value depends on the type of insulation, its thickness, and its density.

Thanks. They are steel. Picture in post above.

 

What would be an example of a good R-value?

 

And what would a "breather membrane" be called in Thai?

 

Lastly I am not clear why I would need a breather membrane if I use fiber cement tiles, my old roof did not have one and no problem with rain etc. For metal sheet I can see it would be essential because of noice factor. ??

[Sheryl]

I have found specs for one brand of non-asbetos  fiber cement tile, Roman tiles from Siam Cement Group.  This is not the brand I used on the garden shed, that was Oran but that doesn't come in white, SCG does plus the non-asbestos is desirable for the main house.

 

Specs are:

size 50 x 120, same as current roof

thickness: 5.5mm so thicker than current which is only 4

weight: 6.7 kg so a good 2 kg heavier than current roof tiles

However the recommended batten spacing is 100 cm which is what I have.

 

Will this be a problem?

 

 

   

 

 

[Kwasaki]

2 minutes ago, Sheryl said:

Thanks. They are steel. Picture in post above.

What would be an example of a good R-value?

And what would a "breather membrane" be called in Thai?

 

Lastly I am not clear why I would need a breather membrane if I use fiber cement tiles, my old roof did not have one and no problem with rain etc. For metal sheet I can see it would be essential because of noice factor. ??

Yes sorry the pictures did not show when l looked at the post.

 

You have a sound steel roof construction there.

Looking at the roof loft frankly l would just insulate your ceiling area with a fibre-glass if you so wished or leave if your happy with your present situation.. 

 

Yes again you can just replace the roof with the same as your garden shed roofing and fix with self-tapping screws instead of hook-bolts.

 

You can then keep your refurbish costs to a minimum but install new wide valley guttering and check purlin or timber fascia at eaves purlin level.

[Kwasaki]

14 minutes ago, Sheryl said:

Specs are:

size 50 x 120, same as current roof

thickness: 5.5mm so thicker than current which is only 4

weight: 6.7 kg so a good 2 kg heavier than current roof tiles

However the recommended batten spacing is 100 cm which is what I have.

 

Will this be a problem?

I would say no problem as already posted your roof steelworks are sound,  calculations made at times show much greater weight can usually be used and increased in the constructed of roof steel-work.

The 2 kilo will be spread over an area.

[simoh1490]

3 hours ago, Sheryl said:

 

Thanks, Simoh, I really appreciate your patience.

 

I was hoping not to put in any new battens but rather use the existing, is there any reason why I can't do that? They are 2x3 inches and spaced 1 meter apart. Picture of the attic void below.

 

I live in Prachinburi. Nakorn Nayok is 45 minute drive, Sakeo is 1 hour plus.

 

Can you tell me a brand name in Thailand for the radiant barrier? I think I now understand how it should be installed but am concerned about sourcing it.

 

Thanks!

 

 

 

 

(The yellow lighting is to deter bats)

Everybody's questions/issues answered in one post below:

 

Radiant barrier is sold at Homepro for example, the brand is Sunshield and it's 1,829 baht for a 60 metre roll that measures 1.25 metres across.

https://www.homepro.co.th/product/196545

 

Kawasaki - yes, sorry, I only meant to imply that the proposed new roof is similar in shape and size to the old roof.

 

Earlier Poster regarding radiated heat vs convected heat - again yes, it was not intended to be a precise scientific explanation, more to imply that heat radiated from the roof/iron will hit the radiant barrier, at which point it will no longer be radiated heat but will instead merely warm the surrounding air which is then considered to be convected heat.

 

Sheryl - Crossy will be able to advise more appropriately but from the pictures you've posted I would have no qualms about placing insulation on the floor of the attic/roof void. I'll post my attic set up in a moment so you can see what a finished roof void looks like

 

Finally, a bit of semantics perhaps, but  - radiant barrier can be retrofitted, aka fastened on the inside of the rafters but it's best applied on the outside of the rafter and new battens placed on top, before the final roof covering is applied, that way it protects the steel from radiated heat which an inside fitting does not do.

 

Am looking at distributors around you and will come back to you if any success.

 

[simoh1490]

3 hours ago, Sheryl said:

Do you mean a metal top sheet that is coated with something or another substance top sheet that is coated with metal? Sorry, still not clear on what this is.

 

I have found specs for a metal roof sheet that comes with EPE foam insulation  that has "embossed aluminum foil with bubbles" under it, is that the sort of thing you mean? (made by SKC).

PE foam insulation for heat is to be avoided at all costs. It comprises two outer layers of aluminium foil and a bubble wrap centre that is about 4 mm thick, it is touted heavily as insulation but if you search on the web you'll find that its R value is close to zero!  The only heat insulating properties PE foam has is that the outside foil acts as a radiant barrier, it's a huge con. I've used it as a radiant barrier but nothing more, it's also horribly expensive for what it is. Having said all that, if it comes attached to the sheet metal roof panels it may have some value as a noise damper when it rains but don't expect it to have any thermal properties, despite what the manufacturers say. 

 

 

[carlyai]

Boy, when experts get together, they sure muddy the water.

If your house was cool or Ok before, don't worry about the insulation.

If you want insulation, there was an indepth study done by a TV member before he insulated his house....I just followed his advice.

Roof 20 years since replacement and you know if you need insulation or not.

Me, I'd go with the new old roof, if you're happy, and spend the saved money on vermin proofing your house. Have you tried those fake Owls? Sorry off topic.

Sent from my SM-J700F using Tapatalk

[simoh1490]

Well yes, sort of! Except it's possible from the photographs supplied that the old roof panels might well contain asbestos which in Thailand is highly likely hence replacing like for like is not really that sensible. Also, whereas the old product had some insulating qualities, the newer better steel roofs don't so the need for insulation is derived from that changeover.

[simoh1490]

3 hours ago, Sheryl said:

Thanks. They are steel. Picture in post above.

 

What would be an example of a good R-value?

 

And what would a "breather membrane" be called in Thai?

 

Lastly I am not clear why I would need a breather membrane if I use fiber cement tiles, my old roof did not have one and no problem with rain etc. For metal sheet I can see it would be essential because of noice factor. ??

A minimum R Value for roof insulation is R16, R32 or higher is much better - I put two 6 inch rolls, one on top of the the other  which in theory gives me R64 and it works really well for all but the very hotest days.

 

Here's one company near you that might be worth checking out: https://www.thaisyncon.com/about-us-metalsheet-thaisyncon-tss

[Sheryl]

Thanks, Simoh, you are very helpful.

 

Can you comment on the issue of whether my roof infrastructure would be OK to support replacement fibre cement with weight of 6.7kg per 120 X 50 tile; my current tiles are about 4.5 kg so it will be an increase in weight, but the battens are the recommended 1 meter apart.

 

Good to know re the EPE foam, I will give it a miss. What about PU insulation attached to metal sheets?(like this https://www.thaisyncon.com/insulateroof-metalsheet) 

And will critters be likley to eat the PU insulation? That is an important consideration...

 

I have to go to Bangkok tomorrow and will stop at a few places on the way and price things. At this point I am not decided between new fiber cement vs metal sheet. Though I am finding that it is hard to find fibre cement in white.

 

I will definitely put in a radiant barrier, still undecided on the insulation for the ceiling floor (if I get metal sheets will definitely get those with attached insultaion, for the noise) but I think it can be done after the fact as well so might just wait and see, especially if it proves costly.

[Sheryl]

1 hour ago, carlyai said:

Boy, when experts get together, they sure muddy the water.

If your house was cool or Ok before, don't worry about the insulation.

If you want insulation, there was an indepth study done by a TV member before he insulated his house....I just followed his advice.

Roof 20 years since replacement and you know if you need insulation or not.

Me, I'd go with the new old roof, if you're happy, and spend the saved money on vermin proofing your house. Have you tried those fake Owls? Sorry off topic.

Sent from my SM-J700F using Tapatalk
 

My house was not/is not cool. That is the one aspect I am looking to change this time around.  It gets really, really hot in the attic and on the second floor and my electric bills are sky high from the a/c.

 

Still not clear with insulation vs radiant barrier vs both in terms of comparative cooling, though.  I worry bit that insulation would prevent heat from rising up from the house to the attic and then out, which it needs to do.  I understand it will stop heat from passing down from attic but seems like it would also block the reverse, and the vents in the atytic are where heat needs to exit the house....?

[bankruatsteve]

To me, your roof doesn't look conducive to put a radiant barrier there.  Just lay it down on the ceiling with minimum insulation.  Some insulation is necessary to prevent conductive transfer.  Otherwise, extra insulation does nothing in this climate.  Reflective to radiant heat of any kind is what you need.

[simoh1490]

34 minutes ago, Sheryl said:

Thanks, Simoh, you are very helpful.

 

Can you comment on the issue of whether my roof infrastructure would be OK to support replacement fibre cement with weight of 6.7kg per 120 X 50 tile; my current tiles are about 4.5 kg so it will be an increase in weight, but the battens are the recommended 1 meter apart.

 

Good to know re the EPE foam, I will give it a miss. What about PU insulation attached to metal sheets?(like this https://www.thaisyncon.com/insulateroof-metalsheet) 

And will critters be likley to eat the PU insulation? That is an important consideration...

 

I have to go to Bangkok tomorrow and will stop at a few places on the way and price things. At this point I am not decided between new fiber cement vs metal sheet. Though I am finding that it is hard to find fibre cement in white.

 

I will definitely put in a radiant barrier, still undecided on the insulation for the ceiling floor (if I get metal sheets will definitely get those with attached insultaion, for the noise) but I think it can be done after the fact as well so might just wait and see, especially if it proves costly.

Sorry, I can't comment on the engineering aspects of your roof, I simply don't know.

 

PU foam insulation is excellent, it's a sprayed on foam that kills noise stone dead and if applied thickly enough it will provide a thermal insulation barrier, an all in one solution - I believe PU foam is resistent to vermin. 

[simoh1490]

19 minutes ago, bankruatsteve said:

To me, your roof doesn't look conducive to put a radiant barrier there.  Just lay it down on the ceiling with minimum insulation.  Some insulation is necessary to prevent conductive transfer.  Otherwise, extra insulation does nothing in this climate.  Reflective to radiant heat of any kind is what you need.

A radiant barrier must face the source of radiated heat, it doesn't work very well when that angle is changed. Also, laying a radiant barrier on the floor of the attic means it will get covered in dust very quickly and that reduces the ability of the barrier to radiate effectively.

 

A radiant barrier's performance is determined by three factors:

• Emissivity (or emittance) – the ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area. It's expressed as a number a between 0 and 1. The higher the number, the greater the emitted radiation.

• Reflectivity (or reflectance) – a measure of how much radiant heat is reflected by a material. It's also expressed as a number between 0 and 1 (sometimes, it is given as a percentage between 0 and 100%). The higher the number, the greater the reflectivity.

• The angle the heat wave strikes the surface – a right angle (perpendicular) usually works best.

http://www.daviddarling.info/encyclopedia/R/AE_radiant_barrier.html

[simoh1490]

57 minutes ago, Sheryl said:

My house was not/is not cool. That is the one aspect I am looking to change this time around.  It gets really, really hot in the attic and on the second floor and my electric bills are sky high from the a/c.

 

Still not clear with insulation vs radiant barrier vs both in terms of comparative cooling, though.  I worry bit that insulation would prevent heat from rising up from the house to the attic and then out, which it needs to do.  I understand it will stop heat from passing down from attic but seems like it would also block the reverse, and the vents in the atytic are where heat needs to exit the house....?

A Big No!

Heat does not travel upwards in a house, heat travels downwards from the source of  heat, (the sun, the stored heat in the roof and the stored heat in the steel and the walls). As the upper parts of the house get saturated with heat it travels down the walls into the living space, walls further trap hot air in rooms.  The rules for thermal insulation are number one, deflect the source of the heat, aka radiant barrier, number two, insulate against what you can't deflect, aka batts of rolled insulation. So number one is a radiant barrier (cheap and effective), number two is adequate ventilation to get rid of the hot air and number three is rolled insulation batts, in that order. Air flow or ventilation in a roof void/attic is key, once you've killed the radiated heat aspect you'll need to make sure you have adequate venting for the hot air and this comes in two parts, hot air out and cooler air in. Hot air leaves the roof void via vents but they will not work hardly at all unless there is a means to draw in cooler air from the bottom of the roof, aka the eves. But you can do all these things in steps, the first being to select your roof material and agree on the radiant barrier, those are the must do items, the rest you can add on later, if needed. (sorry I can't paragraph this for some reason)....to add: the size of the vent for hot air out must equal the vent size of cool air in, otherwise overall hot air venting is limited to the smallest vent size. What this means in practice is that if you have a hot air vent in the peak of your roof or gable, and you don't have any cool air intake, the effect of that is that you have zero hot air venting in your roof, despite the fact you might be able to see physical vents they simply aren't working.

[carlyai]

Knowing that you want to lower the house temprature, ( sorry if I missed that before), and looking at your roof pics. again, and maybe Crossy is right again. Blue Scope steel would probably fit nicely.

Your old tiles, as I see them are nearly black from mould, like a lot of old tiled houses. Replacing will definitely lower the house temperature.

Tacking high R value double sided reflective insulation under the batterns should work well.

Making sure the end attic vents are clear would also help.

But again, I'm not a professional, just what I've done or would do.



Sent from my SM-J700F using Tapatalk

[Sheryl]

1 hour ago, simoh1490 said:

A Big No!

Heat does not travel upwards in a house, heat travels downwards from the source of  heat, (the sun, the stored heat in the roof and the stored heat in the steel and the walls). As the upper parts of the house get saturated with heat it travels down the walls into the living space, walls further trap hot air in rooms.  The rules for thermal insulation are number one, deflect the source of the heat, aka radiant barrier, number two, insulate against what you can't deflect, aka batts of rolled insulation. So number one is a radiant barrier (cheap and effective), number two is adequate ventilation to get rid of the hot air and number three is rolled insulation batts, in that order. Air flow or ventilation in a roof void/attic is key, once you've killed the radiated heat aspect you'll need to make sure you have adequate venting for the hot air and this comes in two parts, hot air out and cooler air in. Hot air leaves the roof void via vents but they will not work hardly at all unless there is a means to draw in cooler air from the bottom of the roof, aka the eves. But you can do all these things in steps, the first being to select your roof material and agree on the radiant barrier, those are the must do items, the rest you can add on later, if needed. (sorry I can't paragraph this for some reason)....to add: the size of the vent for hot air out must equal the vent size of cool air in, otherwise overall hot air venting is limited to the smallest vent size. What this means in practice is that if you have a hot air vent in the peak of your roof or gable, and you don't have any cool air intake, the effect of that is that you have zero hot air venting in your roof, despite the fact you might be able to see physical vents they simply aren't working.

Thanks, I am really learning a lot here!

 

Re the cool air in, won't that be from the eaves? There is enough space there with the current tiles that bats and rats can squeeze in so presumably air can.  I don't know if it will be different if I use metal sheets. Is there something else special I need to do to ensure a cool air intake?

 

re the insulation batts OK I am convinced.  Last question on them: are they fire proof? Flamable?

[simoh1490]

4 hours ago, Sheryl said:

Thanks, I am really learning a lot here!

 

Re the cool air in, won't that be from the eaves? There is enough space there with the current tiles that bats and rats can squeeze in so presumably air can.  I don't know if it will be different if I use metal sheets. Is there something else special I need to do to ensure a cool air intake?

 

re the insulation batts OK I am convinced.  Last question on them: are they fire proof? Flamable?

 

Fibreglass insulation is fireproof but the kraft paper coating is combustible, many people including myself have metres of the stuff in their roof space, not that makes it any safer but it shows I think that the risk of fire is minimal.  Yes you need the paper coating to avoid moisture absorption which makes the insulation heavier and less effective.

 

Yes, cooler air in via the eves, if not enough, drill some holes and cover with plastic grills.

 

Regarding your electric bill - try replacing the fluorescent light with a 3 or 4 watt LED, that'll reduce consumption from around 58 watt to 3 or 4 watt per hour.

 

A non-engineering view on the steel in your roof - there's a lot less there than in mine, the beams are further apart and much smaller, I would be worried about using concrete tile but steel sheet shouldn't be an issue. 

[wayned]

I was going to jump in some time ago and ask you to post pictures of the interior structure but you were getting good advice.  I now see that you have posted them.  IMHO the structure is very strong with 2x4 "D" section rafters and 1.5x3 "C" section battens.  The current roof is attached with "L" bolts so there is no holes in the battens.

 

I would replace the existing roof with the thicker colored fiber cement panels and attach them with "L" bolts.  I would not worry about installing any insulation on the roof.

 

I would then insulate the above ceiling with batts that can be easily rolled out and installed.  I would use at least 6" insulation with at least an R30 rating.

 

The roof would be easy to replace, the last time that I bought the colored panels locally they were 55 baht each.  The insulation would also be easy to install.  Your picture shows a vent in one gabled end, I would install one in the other end if there isn't one.  You should also install the plastic sculptured vented closeout panels on the fascia where the roof overhangs and could install a wire mesh on the inside of the gable vents to help keep critters out.

 

I installed the same thick colored panels with "L" bolts  on my roof 19 years ago and they still look new.  I have replace a couple that cracked, maybe 5 over the 19 years.

[simoh1490]

5 minutes ago, wayned said:

I was going to jump in some time ago and ask you to post pictures of the interior structure but you were getting good advice.  I now see that you have posted them.  IMHO the structure is very strong with 2x4 "D" section rafters and 1.5x3 "C" section battens.  The current roof is attached with "L" bolts so there is no holes in the battens.

 

I would replace the existing roof with the thicker colored fiber cement panels and attach them with "L" bolts.  I would worry about installing any insulation on the roof.

 

I would then insulate the above ceiling with batts that can be easily rolled out and installed.  I would use insulation with at least an R 6 rating.

 

The roof would be easy to replace, the last time that I bought the colored panels locally they were 55 baht each.  The insulation would also be easy to install.  Your picture shows a vent in one gabled end, I would install one in the other end if there isn't one.  You should also install the plastic sculptured vented closeout panels on the fascia where the roof overhangs and could install a wire mesh on the inside of the gable vents to help keep critters out.

I'm guessing you intended to write 6 inch insulation, not R6, an R6 rating is extremely low, hardly any thermal resistance at all?

 

Wire mesh over the vent is a good idea, as is a second vent at the other end, if not already present. If a second vent is installed, make it as big as possible and cover with mesh.

 

Finally, if you're getting rats etc in the attic: they mostly come from overhanging trees or via rain water guttering downspouts, try sticking some wire mesh in the ends of the downspouts and/or wire mesh in the  gutters themselves.

[wayned]

37 minutes ago, simoh1490 said:

I'm guessing you intended to write 6 inch insulation, not R6, an R6 rating is extremely low, hardly any thermal resistance at all?

Your right, I corrected my original post.  Sometimes my fingers get disconnected from my brain and if I don't proof read what I wrote it comes out garbled! The CCGOF syndrome!

[Kwasaki]

13 hours ago, simoh1490 said:

Sorry, I can't comment on the engineering aspects of your roof, I simply don't know.

I already have. 

[Kwasaki]

Suggested roof refurbish. 

[simoh1490]

Again on the subject of attic or roof void ventilation:

 

My house is not large, it's single story and the footprint of it is about 150 square metres but the peak or ridge line of the roof rises very high, it's about 18 feet or so from the floor of the attic to the ridge line. I have four gable ends, these are the flat vertical parts of the roof where you typically locate air vents, fortunately, they all face in different directions so the potential for cross air flow is good. I replaced each of the exhaust vents (they come in triangle shaped pairs) with larger vents and then I replaced all the eves boards with vented boards. The effect of all of that is that I now have good airflow in and out, I measured it all and I have 12 (twelve) square feet of vent for cool air in AND 12 (twelve) square feet for hot air out. Whilst twelve square feet sounds like a lot it's only three and a half feet by three and a half feet and the small gaps in vents add up very quickly - there are calculators available on the internet that tell you how much venting you should have based on the size of your roof/attic. The idea with all of that is to create air flow whereby cool air is drawn in at the bottom of the house whilst the hot air is vented out at the top, it's important to know that hot air will only move upwards if there is cooler air available below it, if there isn't it will remain right where it is. On a hot day I can open a window on the cool side of the house, open the door to the closet containing access to the roof void and I can feel that cooler air rushing in and upwards, it's known as the chimney effect which is what you should try and achieve if you can because it's so nice to have and high electric bills will become a thing of the past. So when you look at your roof vent and think, that's plenty big enough, just keep the above sizes in mind. Finally, I also installed an exhaust fan in one of the gable vents which is hooked up to a thermostatic switch, whenever the temperature in the roof gets above 40 degrees the fan kicks in - it's very cheap to run and the fan cost under 1,000 baht. All of those things, combined with insulated batt insulation (R64) on the attic floor means there are only about five days per year when I have to run air con in the living room. We still use air con in the bedroom at night for a couple of months each year but that's more of a luxury than anything else, there's also some months of the year when we use it in the living room in the late evening as the heat stored in the roof, walls and steel releases into the living area, just like a UK storage heater!. I'd posted pictures of these things but I can't get them to upload so sorry about that.

[simoh1490]

1 minute ago, Kwasaki said:

Suggested roof refurbish. 

That's helpful, what I was calling battens, you've labelled them as top hat spacers or similar, they are the same thing and they provide the means for establishing an air gap between the roof tile/sheet and the vapour barrier/radiant barrier. In a retrofit situation, you'd install the vapour barrier/radiant barrier on the A-A side of the rafter, as shown on your diagram but it's a job and a half trying to do that from the inside on a tall roof (I know) plus it's not easy to drill and fasten the barrier onto the steel.

[sfokevin]

Sheryl... You seem to have the structural and insulation issues sorted out... But the color choice still remains... I recommend orange... which is the new pink... 

[Kwasaki]

3 minutes ago, simoh1490 said:

That's helpful, what I was calling battens, you've labelled them as top hat spacers or similar, they are the same thing and they provide the means for establishing an air gap between the roof tile/sheet and the vapour barrier/radiant barrier. In a retrofit situation, you'd install the vapour barrier/radiant barrier on the A-A side of the rafter, as shown on your diagram but it's a job and a half trying to do that from the inside on a tall roof (I know) plus it's not easy to drill and fasten the barrier onto the steel.

Most times everything is a matter of cost this rough NTS sketch is an example of a straight forward basic way to improve the performance of the old roof, any specification could be expanded but at a higher cost.

Roof space is good and has existing vents in the front gables,  extra venting can be done in ridge and eaves to improve air-flow.

The top hat spacers can be bought with perforations they are inexpensive.

They are fixed into existing roof channel purlins with self tap screws.

The top roof sheet is also fixed with self-tap screws so whatever the selected barrier is,  it is not penetrated.

The self-tapper screws for fixing fibre cement roof sheet cover is OK, hook bolts are obsolete.

 

As for your suggestion of fixing that vapour barrier/radiant barrier on the underside of rafters it is made by fixing top hat section steel or zeds to the steel then fix your barrier.

 

 

 

[Sheryl]

Let me see if I am following this correctly: Put the radiant barrier atop the purlins  and use  "top hat spacers" to both affix them and create a small space between them and the roofing, is that correct? Is that going to be enough free space?

 

Several dealers of  metal sheet like bluesource colorbond, offer to pre-fix insulation with radiant barrier. glued directly to the metal sheets.  Apparently this is foam (probably EPE) with aluminum foil under it. While this would be vastly easier to install than trying to affix an aluminum radiant barrier separately,  I question its effectiveness since there would not then be a void between the roof material and the barrier but rather foam. My google searches of this issue as well as the info you have all provided leads me to think that would completely defeat the purpose of the radiant barrier and thus all I would be gaining is some noise buffer, but can you all confirm/comment? It does raise the cost considerably.

 

Still debating fiber cement vs colorbond vs non-bluecope brand "galvalume" which seems to be the same thing? (company is KSS Thailand which seems also to go by the name SKC Thailand, specs attached). Anyone have any experience with thsi last?  The nearest dealer of either this or colorbond is a good 4 hour roundtrip drive from me; the galvalume costs substantially less than the colorbond.

 

One other question: does anyone know if rats will eat (1) EPE and (2) fiber glass insulation? I do not mean eat through it to get somewhere - they will do that with ANYTHING in my experience, and they won't need to in order to get to my attic as they have other ways in through the eaves and vents, and rather than try to seal those up (a hassle and might impede air flow) I prefer to stick with my current system which is just to put one of my cats up in the attic from time to time. I mean will they eat it as food? Because if so neither will last long.

 

Thanks!

 

 

 

 

roof sheets metal SKC.pdf

[simoh1490]

22 minutes ago, Sheryl said:

Let me see if I am following this correctly: Put the radiant barrier atop the purlins  and use  "top hat spacers" to both affix them and create a small space between them and the roofing, is that correct? Is that going to be enough free space?

 

Several dealers of  metal sheet like bluesource colorbond, offer to pre-fix insulation with radiant barrier. glued directly to the metal sheets.  Apparently this is foam (probably EPE) with aluminum foil under it. While this would be vastly easier to install than trying to affix an aluminum radiant barrier separately,  I question its effectiveness since there would not then be a void between the roof material and the barrier but rather foam. My google searches of this issue as well as the info you have all provided leads me to think that would completely defeat the purpose of the radiant barrier and thus all I would be gaining is some noise buffer, but can you all confirm/comment? It does raise the cost considerably.

 

Still debating fiber cement vs colorbond vs non-bluecope brand "galvalume" which seems to be the same thing? (company is KSS Thailand which seems also to go by the name SKC Thailand, specs attached). Anyone have any experience with thsi last?  The nearest dealer of either this or colorbond is a good 4 hour roundtrip drive from me; the galvalume costs substantially less than the colorbond.

 

One other question: does anyone know if rats will eat (1) EPE and (2) fiber glass insulation? I do not mean eat through it to get somewhere - they will do that with ANYTHING in my experience, and they won't need to in order to get to my attic as they have other ways in through the eaves and vents, and rather than try to seal those up (a hassle and might impede air flow) I prefer to stick with my current system which is just to put one of my cats up in the attic from time to time. I mean will they eat it as food? Because if so neither will last long.

 

Thanks!

 

 

 

 

roof sheets metal SKC.pdf

 

The easy parts first.....no, rats will not eat fibreglass insulation as food but if the kraft paper covering is damaged rodents may nest in it and droppings present potentially serious health problems.

 

SKC info here: http://www.skcthailand.co.th/web/index.php

 

The gap between the Radiant Barrier and the roof doesn't need to be large, it just needs to be a space. If there is no space the radiant barrier conducts heat from the roof and radiates it downwards hence no gap means the radiant barrier is part of the roof surface and it won't work.

 

Having the supplier fix EPE to the underside would be a good move since it will deaden external noise, aka rain. But as said previously,  it won't provide much at all in the way of thermal insulation but you can always tackle that issue separately and in different ways.

 

Having the supplier also afix radiant barrier to the EPE foam raises the same questions in my mind that you have raised. Whilst EPE foam is not heat conductive in the same way that steel is, it will still transfer heat in the same way that almost any material will transfer heat, if it is hot enough for long enough - remember, insulation is a defense mechanism that can be defeated if it is subjected to high enough temperatures for long enough. In theory, the EPE foam should not radiate heat onwards but I don't know what the practicalities of that situation are, perhaps others can comment. The safest solution would be to separate the roofing product from the radiant barrier and treat them separately, after all, radiant barrier is cheap enough and doesn't require any special effort above and beyond what replacing the roofing material requires.

 

Best solution but most expensive - colourbond with EPE fixed to underside, separate radiant barrier and rolls of fibre glass insulation on the attic floor

 

Equally good but cheaper - colourbond with EPE fixed to underside plus separate radiant barrier - try it and see if the heat issue is tolerable or not, if not then add fibreglass rolls on the attic floor (but you may be able to avoid this step). Note: a roll of 6 inch foil encased fibre glass insulation costs 369 on sale, it measure 0.60 metres x 4 metres and covers 2.4 square metres. If your house is say 100 square metres that's 41 rolls or 15K+.

 

Even less expensive - colourbond with no EPE plus a separate radiant barrier and no fibre glass insulation. Your risk here is that if the noise from say rain is excessive it might be difficult to baffle the sound apart from laying fibreglass rolls on the attic floor.

 

I personally wouldn't use fibre cement on a roof but that's just me, I think it's excessively heavy and it doesn't weather well - I have a patio deck made from the stuff and it needs painting every year.

 

 

[Sheryl]

Thanks!

 

In terms of installing a seperate radiant barrier do I understand right that it would be by puttingthe radiant barrier atop the purlins  and use  "top hat spacers" to both affix it and create a small space between it and the roofing? And then the metal sheets would be affixed with screws long enough to encompass the space created by the top hat spacers?

 

And will rats eat EPE? Noted that they won't eat fiberglass.