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  1. #1
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    metalsheets and venting

    My land and house location allows for strategic position to reduce sun exposure and use of the south-south west winds: we have a large tree on the west side and I plan to place rooms strategically using, for instance, bathrooms as insulation (acoustic and heat types) on the west side. Of course, there would be other air intake from other areas.

    My concern is about venting a metalsheet roof (which seems positive for its inability to store heat after). (I would use a white coating and some foam for noise.) My builder tells me that ridge vents are not possible on a metalsheet roof. If so, I am concerned that other vents will not work to evacuate hot air in the absence of wind. True?

    If that is true, I would like to add a cupola (another way to vent the heat out at the top). Not possible? If not, why can't they weld a cupola structure to the steel beams?

    Any other ideas to allow the heat to rise and get out, apart from putting holes into my roof? LOL Electric fans do not seem to be so economical. There are passive metal vents and, from the pictures, they seem to be able to be fitting on metalsheet: link. I hear they eventually squeak. This would be the last resort.

    If it is a negative, on all counts, I just have soffit and gable vents and loads of insulation on the roof floor or in a drop ceiling seem an option (things that I would do regardless). ( I read for soundproofing that a 15 cm air gap between two layers of fibreglass and then panels would be best, which should be possible, with some modification as we are talking hanging installation: link Soundproofing for planes, chicken calls, birds, frogs,...)

    I would think that this soundproofing construction would be excellent for insulation as well (for ceilings/roofs) and vertical walls as well, with a range of products to be used. ACC don't seem to be available in Chiang Mai. Not sure of the ROI of different types of double walls material: bricks VS one of ACC .

    But, back to roof, I think there are 2 basic shapes of roofs (apart from flat): A shape (cheapest/simplest to build) or pyramid shape. My builder/architect tells me A shape has only 2 soffit sides. If there is no ridge vents and cupola (and no metal round vent), focussing on insulation (drop ceiling AND floor roof layers) might be the best ROI/solution!

    Thanks for your ideas and advice.

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    How to Install a Metal Roof Ridge Cap | ABC In the second part of this video the person in the video says that you should NOT have both soffit and gable vents.

  3. #3
    Member KiCanCummins's Avatar
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    [QUOTE=runker;3677992]How to Install a Metal Roof Ridge Cap | ABC In the second part of this video the person in the video says that you should NOT have both soffit and gable vents.[/QUOT

    "Soffit Venting vs Gable Venting" what a load of bollocks, here in Ontario, Canada it is mandated by code, don't these guys know basic physics, heat rises, LOL
    Moved back to Kanada

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    Member KiCanCummins's Avatar
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    Check out this video from Youtube, "Installing a roof made from COLORBOND® steel".



    from the 1.00 mark to 1.20 they show blue eps foam about 1" thick under the roof material. I would say that this not only protects from heat radiation but will also dampen the sound of the rain.

    All this in Australia where the temperature can reach well into the 40c's.

    When I come back to Thailand I will be building a new house and seriously consider this as it is light and will help with the radiant heat also. I am looking to build with energy conservation and cooling as the main criteria in selecting materials that are locally sourced.

    CMdweller, a combination of soffit vents and good sized gable vents with the above roof system should give a cooler attic, but will only be at ambient air temperature. I plan on having 200mm of eps foam sprayed on to the top of the ceiling panels to stop the ambient air in the attic heating the rooms below, yes I know that heat rises but in my wifes issan house she has just the foil under the concrete tiles with small gable vents (and on occasion, when changing light bulbs) I have noted that the ceiling is warm to the touch even with the AC on.

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    Thank you all for your replies, information, and ideas.

    I listened to the video and what I came out with is when the guy is asked about venting he states that one will get a lot of crosswind airflow and it will make the ridge vent less effective. I am troubled by his answer because he assumes there will be crosswind. My question is: "And when you don't have any wind or very little wind?" IMHO, if the ambient temperature is 35 c., the roof cavity will be a lot hotter (especially if there is nothing under the tiles or metal sheets). It seems to me that this heat has to escape. We know heat will rise up. Some of it will move out of the gable vents, but not a lot, I figure. So heat will increase if there is no ridge vent, assuming they work as I think they do.

    If no ridge vent, one will have to increase insulation. The best way is on the floor of the cavity. I even wonder if it is not a good idea to not put any insulation under the tiles/sheets. That insulation will slow down the release of the heat. I can put a lot of insulation in the drop ceiling too.

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    condensation?

    Can there be problems with condensation/mold as temperature drops during the night and there is high humidity like in the rain season? Water vapour hitting a surface like metal usually becomes water if a surface is colder than the water. Water vapour is everywhere. It can be bathroom shower water vapour or ambient water vapour from the rain/humidity. Is there anyone with more information about that?

  7. #7
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    Quote Originally Posted by KiCanCummins View Post
    Check out this video from Youtube, "Installing a roof made from COLORBOND® steel".



    from the 1.00 mark to 1.20 they show blue eps foam about 1" thick under the roof material. I would say that this not only protects from heat radiation but will also dampen the sound of the rain.

    All this in Australia where the temperature can reach well into the 40c's.

    When I come back to Thailand I will be building a new house and seriously consider this as it is light and will help with the radiant heat also. I am looking to build with energy conservation and cooling as the main criteria in selecting materials that are locally sourced.

    CMdweller, a combination of soffit vents and good sized gable vents with the above roof system should give a cooler attic, but will only be at ambient air temperature. I plan on having 200mm of eps foam sprayed on to the top of the ceiling panels to stop the ambient air in the attic heating the rooms below, yes I know that heat rises but in my wifes issan house she has just the foil under the concrete tiles with small gable vents (and on occasion, when changing light bulbs) I have noted that the ceiling is warm to the touch even with the AC on.
    Thanks for the info and the video. I think foam under the tiles is not a bad idea as you expressed. If there are leaks, it will also help. Condensation without any foam/bubble? The only downside on foam is the potential fumes affecting the living space, I think, but I don't see that being a problem as gable vents should help to eliminate the toxic fumes. Maybe they might burn a little under the metal sheet and let off toxic fumes? I have seen programs where people complain, but it is not clear that this is a problem. There can be many reasons why sprayed foam can be a problem. I don't know. I was thinking of using spray foam to seal the roof floor from the living space (above the drop ceiling (which I assume has some sheetings at the roof floor level). I would spray where the roof slopes meet the floor of that roof to insure there is no air cracks,...

    Does a bigger roof cavity help? The metal sheet seems to be 30% more from a 30 degree pitch roof to a 45 degrees pitch roof. More sheet, more steel beams and maybe even bigger ones? More/bigger concrete columns? IS the ROI there? Insulation might be much cheaper. I think that a ridge vent would help more than gable vents. No vents is not an option. The soft vents if there is a wind will help move the air, as the gable vents (on the opposite side of an A frame house. not sure if that happens and how effective that is? Still, if there is no wind, I think a ridge vent should help. How much? I don't know? Are they expensive? Is it worth it?
    Last edited by CMdweller; 12-12-2017 at 10:43 PM.

  8. #8
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    My old US house that was built in 1976 and it had ridge and gable without soffits vents so go figure and back then no one really cared.

  9. #9
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    Quote Originally Posted by CMdweller View Post
    Thanks for the info and the video. I think foam under the tiles is not a bad idea as you expressed. If there are leaks, it will also help. Condensation without any foam/bubble? The only downside on foam is the potential fumes affecting the living space, I think, but I don't see that being a problem as gable vents should help to eliminate the toxic fumes. Maybe they might burn a little under the metal sheet and let off toxic fumes? I have seen programs where people complain, but it is not clear that this is a problem. There can be many reasons why sprayed foam can be a problem. I don't know. I was thinking of using spray foam to seal the roof floor from the living space (above the drop ceiling (which I assume has some sheetings at the roof floor level). I would spray where the roof slopes meet the floor of that roof to insure there is no air cracks,...

    Does a bigger roof cavity help? The metal sheet seems to be 30% more from a 30 degree pitch roof to a 45 degrees pitch roof. More sheet, more steel beams and maybe even bigger ones? More/bigger concrete columns? IS the ROI there? Insulation might be much cheaper. I think that a ridge vent would help more than gable vents. No vents is not an option. The soft vents if there is a wind will help move the air, as the gable vents (on the opposite side of an A frame house. not sure if that happens and how effective that is? Still, if there is no wind, I think a ridge vent should help. How much? I don't know? Are they expensive? Is it worth it?
    I think you will find the sheet metal roof will be much lighter than a tile roof, the structure underneath will be lighter also. If you look at the video there is not much pitch on that roof, and if it is properly installed it will stand up to the driving rain better than tiles, as there are only seams running down the pitch. Having the foam sheet will allow some expansion and venting between the foam and the roofing material, with good drainage to boot.

    For spray foam insulation, its best to put it on the top of the ceiling gypsum board, after all the electrical has been done (make sure all connections are not within the thickness area for where the foam is to be sprayed) this is where you will find the least temperature differential between the top of the ceiling panel & the bottom of the panel.

    Spray foam on the underside, as advertised by a company in Thailand to stop water leaks, is just asking for trouble. If you roof leaks it will rot the roofing material roof and create a haven for mould, apart from never finding the source of the leak. Also the expansion rates of the foam and the material it is sprayed on to can cause the foma to detach from the roofing material.

    Last October I was looking at a leaking problem in the wife's house in Korat, she had the "Reflective Insulation" applied under the concrete tiles, I would say that almost 40% to 50% was drooping down the plastic just slowly disintegrating. She has the same thing on the car port that I designed 4 yrs ago, the builder advised on the sheet metal with a thin foam membrane on the back, now it too is disintegrating. I see the problem with these as the plastic in the foam is not temperature resistant and the adhesive on the steel was sadly lacking, looked like they did it with their eyes closed.

    As for the ridge vents on the roofing, it looks like it is hard to get the ridge vents for tiles, I dont know the costing on the australian style metal roofing, may be on of our Aussie friend can help out here.

    A bit of an oxy moron here in the great white north is that we have ridge vents, then old man winter comes and covers them up, LOL. The thing here is to have good ventilation to keep the roofing material COLD if the heat from the house gets underneath you have major ICE buildups.

    Just my observations KC.

  10. #10
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    Quote Originally Posted by KiCanCummins View Post

    Spray foam on the underside, as advertised by a company in Thailand to stop water leaks, is just asking for trouble. If you roof leaks it will rot the roofing material roof and create a haven for mould, apart from never finding the source of the leak. Also the expansion rates of the foam and the material it is sprayed on to can cause the foma to detach from the roofing material.
    Thanks for that great piece of information on the foam spraying location. Roof floor makes more sense. I think they must only use the open-cell foam here which might explain why it is not that resilient around water and heat as explained at https://www.thomasnet.com/articles/p...ell-open-cell/.

    I think the Bluescope sheets have a bubble-wrap underbelly. I hope it does not end up being like the foam. I am tempted to just "right-off" the metal sheets completely and focus on the ceiling floor and the drop ceiling space. I am not too sure what the architect is going to use for sheathing on the floor of the roof, but I wonder if condensation/dew is not going to drop on that bit by bit in the morning/night from the underbelly of the metal sheet (I see condensation on car windows in the morning in CM now, so the same could be happening on the metal sheet, I think.) I am no expert, but should not the heat kill mold?

    People complain about the noise, but if soundproofing using loads of fibreglass, some air gaps (15 cm) and some foam where there could be gaps or cracks between sheathing, beams, ... should do the trick, but I am not sure.

    Of course, we could do this (which made one contractor a lot of money): . I doubt any insulation was used under the 1st roof. I doubt the architect/builder mentioned that cheaper solutions exist! Venting? Probably none. I sure could put a lot of fibreglass in that roof cavity for 500,000 Bahts! I guess the shock and attention-seeking "solution" was "worth it! It is an endorsement for metal sheet roofs, in a round-about way. Sure is ugly.
    Last edited by CMdweller; 13-12-2017 at 01:38 PM.

  11. #11
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    Quote Originally Posted by KiCanCummins View Post
    She has the same thing on the car port that I designed 4 yrs ago, the builder advised on the sheet metal with a thin foam membrane on the back, now it too is disintegrating. I see the problem with these as the plastic in the foam is not temperature resistant and the adhesive on the steel was sadly lacking, looked like they did it with their eyes closed.
    I am considering all the same roofing questions and asked elsewhere on this forum about the durability of foam/foil-backed Colorbond. My instinct is that the steel will expand and contract significantly every day, whereas foam is not famous for its elasticity so I'd expect the two to part company over time. I am interested in any real-life experiences that anyone can share.

    On the question of venting, I was planning to put a solar-powered fan in one gable end, maybe leave the usual Thai louvred vent at the opposite end of a simple pitched roof. These fans are available as a unit together with a small solar panel, although I haven't noticed any in Thailand yet.

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    Quote Originally Posted by Shutree View Post
    I am considering all the same roofing questions and asked elsewhere on this forum about the durability of foam/foil-backed Colorbond. My instinct is that the steel will expand and contract significantly every day, whereas foam is not famous for its elasticity so I'd expect the two to part company over time. I am interested in any real-life experiences that anyone can share.

    On the question of venting, I was planning to put a solar-powered fan in one gable end, maybe leave the usual Thai louvred vent at the opposite end of a simple pitched roof. These fans are available as a unit together with a small solar panel, although I haven't noticed any in Thailand yet.
    Thanks. Good points!

    This product seems to address the flaws of the products we are talking about: https://youtu.be/RmiJWHXpd0M and this But, let's be careful about screws as 2 metals can cause rusting: https://en.wikipedia.org/wiki/Galvan...osion#Overview

    I read that fans can actually be pulling the air from the conditioned space (potentially a/c air) into the roof space, but I suspect that you would need a powerful fan to do this and unvented roof space to achieve this. Solar-powered fans seem a good idea. Are you counting on rain to clean them when dust/dirt covers them up? Or are they designed in a such a way that this will not happen?
    Last edited by CMdweller; 13-12-2017 at 06:22 PM.

  13. #13
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    I found this web page on different types of insulation, quite informative.
    To my amazement I learned that XPS off gasses some nasty stuff, but also interesting on what they say about thermal foil, only good for radiant heat and requires an air gap on the warm side.

    http://www.ecohome.net/guide/choosin...s-applications

    Now one has to understand that the main context of the article is dealing with keeping a house warm in these northern climate at winter time, the summer cooling here (yes it gets to above 30c in the summer) is a bonus.

    KC

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    Quote Originally Posted by KiCanCummins View Post
    I found this web page on different types of insulation, quite informative.
    To my amazement I learned that XPS off gasses some nasty stuff, but also interesting on what they say about thermal foil, only good for radiant heat and requires an air gap on the warm side.

    http://www.ecohome.net/guide/choosin...s-applications

    Now one has to understand that the main context of the article is dealing with keeping a house warm in these northern climate at winter time, the summer cooling here (yes it gets to above 30c in the summer) is a bonus.

    KC
    Thanks for that. Yes, those off-gas are toxic, but I do not know how long they stay like that. One would need to be meticulous and cautious about keeping all the cracks not bringing in the gas in. It is also good for insulating. Here is some great info. about that: Lstiburek?s Rules for Venting Roofs | GreenBuildingAdvisor.com Reading the comments is also very interesting.

    On metal roof, this is a great blog entry with great comments as well: Staying Cool with a Metal Roof | GreenBuildingAdvisor.com

    Here is one:


    "With the previous white shingle roof my attic temps could be over 150º at times in the summers here in southern NJ. But now with the metal roof my attic temp was 79ª F. on a sunny 103º day. I have a probe up there and the first time I saw it I immediately thought an A/C duct had broken and I was cooling the attic space. But that wasn't it - the attic was naturally 79º on a 103º day."

    Read more: Staying Cool with a Metal Roof | GreenBuildingAdvisor.com
    Follow us: @gbadvisor on Twitter | GreenBuildingAdvisor on Facebook

    Yes, most of the information on the internet is about trying to keep the heat in, but air has to be exchanged, if not bad air, stale air becomes a negative for health reasons. In many instances, humidity (man-made or ambient) has to be removed, but not too much.

    There is some good information about hot climates, but it is time-consuming to find there is so little.

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    Quote Originally Posted by Shutree View Post

    On the question of venting, I was planning to put a solar-powered fan in one gable end, maybe leave the usual Thai louvred vent at the opposite end of a simple pitched roof. These fans are available as a unit together with a small solar panel, although I haven't noticed any in Thailand yet.

    That seems like a good idea ... fans at the gable end. Here is some information I am reading. Of course, it is mostly about Northern hemisphere issue. We want cold air, not hot. LOL

    Although the logic behind powered attic ventilators is compelling to many hot-climate homeowners, these devices can cause a host of problems. Here’s the basic problem: a powered attic ventilator will depressurize your attic, and it’s hard to predict where the makeup air will come from. Although the “smart arrows” in the sales brochures shows outdoor air entering the attic through the soffit vents, that’s not what usually happens.


    In many homes, powered attic ventilators pull conditioned air out of the home and into the attic through ceiling cracks. The net result: powered attic ventilators increase rather than decrease cooling costs.


    As the cool air is being sucked out of the house through the ceiling, hot exterior air enters the house through other cracks to replace the exhausted air. The net result: the air conditioner has work harder than ever as it struggles to cool all that entering outdoor air.
    Several studies show that even in a house with a tight ceiling, a powered attic ventilator uses more electricity than it saves.


    Read more: Fans in the Attic: Do They Help or Do They Hurt? | GreenBuildingAdvisor.com
    Follow us: @gbadvisor on Twitter | GreenBuildingAdvisor on Facebook

    AT THE SAME TIME, THERE was an interesting exchange in the comment section. If an attic fan does depressurize the house and bring air from the house, if the sun exposed walls are well insulated, it could be that UNconditioned air (no a/c) could cool the roof.

    "20.
    Nov 5, 2012 11:08 AM ET

    Edited Nov 5, 2012 11:23 AM ET.

    Attic fan reduced my electricity bill
    by j wing


    I've been an energy engineer for over twenty years. My experience has taught me to think beyond articles like this one. In the real world, comfort, low first cost, and immediate gratification take precedence over theory and lab results. To wit, I have intalled two attic fans; both installations were resounding successes:
    1) My 1960-vintage home in northern Alabama runs 5-tons of central air conditioning plus one small window A/C unit. In the summer, the upstairs bedrooms are unbearably hot, due to the ceiling radiating attic heat. The bedrooms can be filled with cool air, yet the hot ceiling makes them feel like being inside a broiler. This past summer,a major outdoor renovation forced me to disconnect the condensing units from the central A/C, leaving me with just the small window unit. So, I put in an attic fan to relieve the hot ceiling. The A/C is off during the day when I'm at work; but the fan runs. By the time I go to bed, the attic is cooler than the inside of my house, so it is drawing heat out. The small window unit is plenty to keep the house comfortably cool.
    2) My mother-in-law stays in her hot home all day and was considering replacing her central A/C system with one of higher capacity. However, the cost was prohibitive, so I installed an attic fan. With a cooler attic, the A/C system had lower heat gain, therby reducing the supply air temperaure at the diffusers. Additionally, the hot ceiling effect was alleviated. MIL was able to turn her thermostat up a few degrees, thereby saving energy and increasing comfort.
    It's very easy to write that better insulation, radiant barriers, and light-colored roofs are components of a superior solution. And they are; I can't argue otherwise. But in the real world, we look for practical solutions that people will actually implement. In the two cases, I've described, the most practical (by far) solution was contrary to the conventional wisdom.



    21.
    Nov 5, 2012 11:45 AM ET

    Edited Nov 5, 2012 11:47 AM ET.

    Response to J Wing
    by Martin Holladay


    J Wing,
    You have installed powered attic ventilators in two homes in recent years, so you obviously like them. According to your anecdotes, the electricity use decreased in both of these buildings.

    Even if your anecdotes are accurate in all details, and even if you have no financial interest in promoting powered attic ventilators, two anecdotes aren't convincing. Needless to say, there are all kinds of reasons that electric bills fluctuate from one month to the next; one of the biggest reasons (when it comes to air conditioning) is variations in weather.
    You have described two buildings with "hot ceilings." I have no idea why anyone with a hot ceiling would think it was easier to install powered attic ventilators than a layer of cellulose insulation. After all, the cellulose insulation doesn't require any electricity.
    Here at GBA, we strive to advise readers of the simplest and best solutions to common building problems. I'd like to repeat my advice: if you have a hot ceiling, install more insulation on your attic floor. Don't install a powered attic ventilator, since these devices, on average, use more electricity than they save.



    22.
    Nov 5, 2012 2:33 PM ET

    Thanks
    by John Bigler


    Excellent article. Thank you Martin.



    23.
    Nov 5, 2012 5:11 PM ET

    Well, to me two anecdotes are
    by j wing


    Well, to me two anecdotes are more compelling than one article, no matter how many times it's been re-written. I have been a professional energy engineer for 2 decades; I understand that there are many variables that account for enrgy use.
    The most important variable, however, is the human beings involved and the particular situation they are dealing with. In both of my anecdotes, the human beings felt that the cost in money, time, work, and hassle would not have sufficient return in comfort. In the case of my house, it is impossible to lay down another layer of insulation.
    On the other hand, each attic fan took about $100 and hour to install. As a curious professional, I was willing to risk the investment to see for myself what effects are. If the attic fans didn't do the trick, then I'd move on to the next solution and be out only $100. The results of my experiments, so far, differ from this article and all the other ones that say the same thing. I report my findings not to argue or to be off-handedly accused of having financial interest, but to advance our understanding and knowledge.
    Building a new house? Definitely insulate the roof and add a radiant barrier. Is your fan-coil unit in a hot attic? Consider an attic fan, especially if you turn the A/C off during the day. Are you at home with the A/C on all day? Consider a different roof heat-gain management system, if you can afford a long-tem investment. Not staying in the house long enough to make the investment worthwhile? Consider a less-expensive solution that may have some drawbacks. Does your attic have insufficient ventilation openings that will cause an attic fan to draw through your house? Increase your ventilation area, or consider a different solution.
    Energy engineering is way more complicated than telling people that there is but one solution to a problem.



    24.
    Nov 5, 2012 5:21 PM ET

    Response to J Wing
    by Martin Holladay


    J,
    Thanks for sharing your anecdotes. I certainly appreciate the information, as I appreciate all information provided by GBA readers. And I accept your assertion that you have no financial interest in promoting powered attic ventilators.

    However, after having read the reports of researchers who have studied the issue and measured energy use in buildings with powered attic ventilators, I'm going to stick with the conclusions and advice of the researchers, even in the face of two anecdotes that buck the trend.



    25.
    Nov 8, 2012 2:21 PM ET

    What about a garage attic??
    by Robert Williams


    I'll be building a large garage with attic storage in NE Texas. I will use a radiant barrier decking, but does a powered attic ventilator make sense here ??



    26.
    Nov 8, 2012 2:34 PM ET

    Response to Robert Williams
    by Martin Holladay


    Robert,
    Running a fan always requires electricity. Of course, a fan cannot cool your garage unless the outdoor air temperature is lower than the indoor air temperature. If you have radiant barrier sheathing, the temperature difference between the two spaces won't be very great, and probably won't be enough to justify the use of the fan.

    The other question: what are you storing in your attic? Does it matter what the temperature is? If you have an old lawnmower and some Christmas ornaments up there, it probably doesn't matter if the garage is 80 degrees or 110 degrees.



    27.
    Feb 2, 2013 7:14 PM ET

    Whole House Fans
    by Kurt Shafer


    Martin,
    Your research into attic fans is of great interest. It is valuable to have the data from those who have studied them recently.
    Your comments about Tamarack are surprising. Tamarack is a fine company with leading edge insulation technology but you do your readers a disservice by inserting your opinion that they "make the best whole-house fans available".
    I had hoped you would have done a little more research into other suppliers in order to offer a more unbiased view.
    I would be very happy to assist you in a thorough market overview which I do regularly for the http://www.WholeHouseFanGuy.com



    28.
    Apr 30, 2013 8:50 AM ET

    Like so many other "plug in"
    by David Jones


    Like so many other "plug in" solutions attic fans certainly have the potential to make things worse rather than better. Your article does a great job of outlining how this happens. As a general rule unless a homeowner has a highly qualified person to evaluate their house, I think its safe to say that attic fans should be avoided.
    I do think that under CERTAIN circumstances an attic fan can be beneficial. The problem is that in most cases, there is no one available to accurately make that determination.
    The primary reason attic fans are not helpful is that they can depresureize the attic and draw air out of the house. Many houses have significant leaks in the air barrier(attic floor) and it would be easy for the attic fan to draw a significant amount of air from the house. If a house has been air sealed by someone with an understanding of the air leakage, then it would seem that the depressurization would be minimal and the attic fan could then be beneficial.
    The amount of air being drawn out of the house is a function of the pressure difference and size of the air leaks in the attic floor. In an attic with gable vents, soffit vents, and ridge venting, I suspect that the attic fan would not create a significant pressure difference and the air leakage from the house is probably small. (assuming even a rudimentary level of air sealing).
    Lee Dodge suggests a "balanced" system where there is an incoming and exhaust fan. This seems like an approach that could also limit depressurization.
    If air leakage is minimized, and depressurization is controlled with either a balanced fan or adequate openings for incoming air then it seems reasonable that the amount of depressurization would minimal and the attic fan could be beneficial.
    Arnie Katz's study concluded that (an undefined amount of?) depressurization was enough to increase cooling costs. This assumes that there is a cooling system in place and operating. In a house not running an ac system any air being drawn from the house is being replaced by outdoor air. If the windows are open in the house there is no "cooling penality" to having some air exhausted from through the attic. if late in the afternoon the house temps rise above the outdoor air temps there is actually a cooling benefit. (we hope the amount of air being exhausted through the attic floor is minimal because the house is air sealed).
    If the house without AC running was closing the windows during the day to keep the house cooler, then any air being exhausted to the attic would be replaced by warmer outdoor air, but that warming of the house is tempered by a cooler ceiling.
    You propose the question "who cares how hot the attic is if there is enough insulation in the attic floor?" Insulation can only slow and not stop the energy transfer. Regardless of what the insulation level is, there will be some level of energy transfer from the warmer attic to the cooler house. So everything else being equal, any house would benefit from a cooler attic. In many houses it is impractical to increase the insulation in the attic. (At least when compared to the difficulty/cost of installing an attic fan. Of course the insulation is the better option if possible.).
    My own experience points to anecdotes showing the attic fan is beneficial. I know of two houses using them and the owners are certain that they make a large difference in comfort. Both houses do not use AC. Both have a large amount of venting for incoming air.




    Read more:
    http://www.greenbuildingadvisor.com/blogs/dept/musings/fans-attic-do-they-help-or-do-they-hurt#ixzz51DCs1CXo
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    Last edited by CMdweller; 14-12-2017 at 12:59 PM.

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    Quote Originally Posted by CMdweller View Post
    Solar-powered fans seem a good idea. Are you counting on rain to clean them when dust/dirt covers them up? Or are they designed in a such a way that this will not happen?
    Good question, I hadn't thought as far ahead as cleaning. Probably send Somchai up a ladder when that day arrives.

    Here is an example of a quality US product which has roof-mounted and gable end mounted options.

    Let your Attic Breathe

    Cheaper alternatives are widely available, outside Thailand.

  17. #17
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    CMdweller,
    Good research I will get to read later today.
    The more knowledge we gain the better we can understand the conditions and requirements.
    Its certainly a task to wade through the myriad of information on the net, especially when those who are posting have had cheap energy, that has now disappeared.

    My take on this is to pay a little more up front for something that will in the long term keep energy costs down, it ain't getting any cheaper thats for sure.

    I read some of the posts on the green building advisor from the middle to the south of the US where with a lot of energy (low cost), one could keep a house comfortable, those days are gone and we have to think of the best (each one will be different) way we can keep those energy bills low.

    I plan to be building in around 2 yrs time when we get back to LOS. So research has been ongoing for some time now.

    What I see for my prefered build (subject to further research & information coming forward) in a cool attic space/roofing material will be the following ideas.

    Steel roofing, might be Colourbond (the aussie stuff) available locally in Thailand, I want white coloured roof but I have to win over Mrs KC first on that one, fastened to the roof battens. Fastened to the battens and between the rafters either xps or eps foam to act as a barrier to the radiant heat from the steel roofing. This would have to be sealed tight to the rafters to keep the radiant heat from entering the attic space, leaving an air channel to duct the heat up and out of the roof. The idea is to keep the attic space as close to ambient air temperature as possible. A possible knock on effect will hopefully be some sound attenuation from when it rains. Included in this design will be large soffit overhangs (1900mm) taking the sun angles into consideration, with a continuous 100mm gap/vent around the perimeter of the house. No use putting large vents in the roof or gable ends if the vents cannot draw from where YOU need it to draw from, like water air will take the path of least resistance, so if inflow area is equal to or larger than the outflow area then very little air will be taken from the living space below. Check out Deck Ape's building thread here on TD as this is what he has done. http://teakdoor.com/construction-in-...ouse-10-a.html (Deck Ape's Big Gringo House -- 10 years later)

    So the here comes the other important item, ceiling insulation, I am looking at spray foam (must be closed cell type, need more research on this). this will completely seal the ceiling from the attic and keep the house below cool. This does come with some major design considerations too. ensure all electrical junction boxes are placed above the finished level that the foam will be. The use of conduit for ALL electrical runs is a must, if a wire has to be rerun or replaced it will make it so much easier. this spray foam would be the last item to be done on the house, I would say about 2 to 3 months after the rest of the build is completed just incase some defect shows up and needs correcting then one is not having to rip up all the foam to make the repair.

    As for the exterior walls I am leaning to 20cm ACC block to give the maximum insulation in one application, as opposed to a double wall with a cavity as I see this as added expense in labour. Windows to be double glazed with ecoating for the times the morning or evening sun will hit the widows, I have yet to see a window design european thai or otherwise that come close to the units that I have had installed as an upgrade on my house here. Double glazed (Argon gas filled) upvc frames, all casement windows have single latch multi point latching system with a single crank to open the window, this puts the removable bug screen between the levers and crank for easy operation of the window. (Baviere Series - Casement and awning window - PVC windows - Lapco) This might be over kill for this environment but I do like how they work and un like aluminium frames do not transfer heat from the outisde. I might have to import these if I cannot source the same locally.

    I am sure there will be more to follow up on, my Ideas at this stage.

    KC

    PS its hard to get my head around some of these theories and constructions when it is a nice sunny day out side, but -15c with a wind chill of -26c, LOL
    Last edited by KiCanCummins; 15-12-2017 at 02:39 AM.

  18. #18
    Thailand Expat David48atTD's Avatar
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    WOW ... interesting

    Would it be true that you guys haven't built a roof structure along these lines in Thailand yet?

    What seems reasonable as building technology and innovation in the West doesn't usually transform
    into practical construction with a builder in Thailand
    .


    I live in sub-tropicial Australia and in Thailand.

    A metal roof is a good idea because of it's low thermal retentive properties ... but usually the Thai Wife
    will decline because Cement Tiles 'look' the best. Good luck with that battle!

    Roof pitch ... have you noticed that roof pitches are usually steeper in Northern Thailand.
    That is attributed to the fact that the rain is perceived to be stronger.


    Build by the KISS principle ... keep it simple.

    1/ Vent the soffit

    2/ Sarking under the roofing material to reflect the heat (I'm not keen on the spray on foam stuff)

    3/ Insulate the ceiling to reduce any heat transfer from the ceiling cavity/attic and reduce noise.
    ... What style of insulation you choose depends on what type of ceiling you have installed.

    4/ Vent the ceiling cavity/attic and the simplistic way is way is through a gable vent which is passive
    ... A gable vent with a fan or
    ... a roof vent ... though the roof vent when poorly fitted can leak.

    Look what products are available in Thailand as ANYTHING imported will both be expensive AND confusing
    to the local 'trades' to install.


    In Thailand, we are purely passive. We did a bedroom rebuild, so a little limited.
    Roof tiles were fiber cement, a material I notice that almost no Westerner considers.
    Reflective metal sarking under.

    We have a suspended tile ceiling and no air-con.
    I went with a simple 'bubble wrap' double sided foil for above ceiling insulation.
    The rating is R1, cost less then BHT 1,000 to do the insulation.


    Just a word on ceiling insulation. You can spend a fortune with the above ceiling insulation,
    and using products which are R 3/4/5 rated however ...
    if you vent the ceiling cavity/attic effectively, the temperature there might only be a few degrees
    above the ambient temperature, thus you don't need a high 'R' rating.

    If, however, you are going to run the Air-Con in the room I would go for a higher 'R' rating with the
    insulation as you would be reducing the rooms temperature significantly that of the ambient temperature.


    The ceiling is vented passively through soffit vents.
    Being an inclined roof, at the lower end the vents passively draw in the air and at the higher end they vent the air.

    A simple and passive design, designed and built by a Thai.

    Fan assisted roof ventilation is the best.
    In the West I have an adjustable thermostatically controlled fan ... brilliant.

    Simple enough to rig one up in Thailand.
    Just get a electric fan and control the power to through a thermostat.

    Alternatively you could buy a solar powered fan and you could post-construction fit it.
    https://solatube.com.au/roof-ventilation/

    IMHO

    Our fingerprints never fade from the lives we touch

  19. #19
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    Quote Originally Posted by David48atTD View Post
    WOW ... interestingWould it be true that you guys haven't built a roof structure along these lines in Thailand yet?What seems reasonable as building technology and innovation in the West doesn't usually transforminto practical construction with a builder in Thailand.I live in sub-tropicial Australia and in Thailand. A metal roof is a good idea because of it's low thermal retentive properties ... but usually the Thai Wife will decline because Cement Tiles 'look' the best. Good luck with that battle!Roof pitch ... have you noticed that roof pitches are usually steeper in Northern Thailand.That is attributed to the fact that the rain is perceived to be stronger.[...]
    Thanks a lot for that advice. I read all of it, but will need to read it again to get all of it. That was a lot of info to take in. Very useful. Thank you.I am a Canadian with NO metal sheet and tropical climate know-how.

    I know a bit about construction and can read, which led me to using metal sheet and convert my Thai wife to it (albeit helped by a builder that is a fan). I even have her agreeing to a white roof. You would use sarking reflective foil? Not the bubble-wrap? Is that to reflect more heat? To control potential leaks/condensation?I read termites/insects/pests don't mind cellulose (foam), but in the roof space? Apparently, most of them don't like fibreglass, but I am sure spiders will love it if there are insects eating food there. Maybe I should populates spiders in the roof space. I think they will be there regardless. LOL There are a lot of potential issues in the tropics. And in Thailand, the list is endless! Flying temples? LOLIt looks like my builder/architect is hesitant about recommending a 45 degrees roof pitch on a 2 story A-shape building (81 m2 house area). What do you think or know? I was going for a pyramid shape, but I think the cost will be higher. You agree? Are all soffits roof better than a mix of gable/soffit roofs? Apparently the builder tells me that ridge vents are not possible on metal sheet roofs. I have seen pics on the internet, but it might not be a local idea. It might be side not to push the limit like you said. I am using the Australian metal sheet Bluescope. I hate noise and I fear birds are going to use the roof to hang there in the morning. The top of the roof could have spikes and wind gizmos to deter them from going there, but what about a 30 degree pitch roof with screws sticking out. I am afraid that the birds will try to land there and scrape the roof with their claws. Would a 45 degree roof prevent the whole issue? I think she thinks the thick metal sheet and the drop ceiling insulation (6 inches + 15 cm air gap) should do the trick on heat (and noise). Not sure biard noise can be mitigated unless I have a motion alarm triggering a loud outside speaker with a huge noise that birds don't like (rifle shots?). Anyway, I am worried about the birds. What do you think? The loudspeaker gizmo idea might be the cheapest and best idea as I have a rather big western oriented tree 3 meter from the house roof where they will be hanging in regardless.. My living quarters are upstairs, but I have bedrooms options on all levels. I have bathrooms oriented to the west (sun and tree side). I plan to build a double wall on the east side perhaps for noise and winter sun exposure (insulating the bedrooms further). I have no windows in my bedrooms. My 2 soffit sides and gable vents should be able to pick up the wind equally well as the corner seems to be oriented where they are supposed to be coming from (SSW according to a website on wind stats for Chiang Mai). Still, not being a geography major, the house has a large rice field on the north and east side that I am told could provide "microclimate" winds. In any case, like you said, a solar powered fan could do the trick to vent if there is no wind. And the soffit vents and gable vents are able to pick up some wind no matter where they come from. A cupola did not get any approval from my builder who was afraid of rain being driven by wind storms. Will an "attic" fan draw air from the conditioned space? As long as it is not a/c air (if I am not using it because the temp. does not require it), I guess I should not mind.)
    Last edited by CMdweller; 15-12-2017 at 03:45 PM.

  20. #20
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    Quote Originally Posted by David48atTD View Post
    WOW ... interesting

    Would it be true that you guys haven't built a roof structure along these lines in Thailand yet?

    What seems reasonable as building technology and innovation in the West doesn't usually transform
    into practical construction with a builder in Thailand
    .


    I live in sub-tropicial Australia and in Thailand.

    A metal roof is a good idea because of it's low thermal retentive properties ... but usually the Thai Wife
    will decline because Cement Tiles 'look' the best. Good luck with that battle!

    Roof pitch ... have you noticed that roof pitches are usually steeper in Northern Thailand.
    That is attributed to the fact that the rain is perceived to be stronger.

    [...]
    Thanks a lot for that advice. I read all of it, but will need to read it again to get all of it. That was a lot of info to take in. Very useful. Thank you.

    I am a Canadian with NO metal sheet and tropical climate know-how. I know a bit about construction and can read, which led me to using metal sheet and convert my Thai wife to it (albeit helped by a builder that is a fan). I even have her agreeing to a white roof.

    You would use sarking reflective foil? Not the bubble-wrap? Is that to reflect more heat? To control potential leaks/condensation?

    I read termites/insects/pests don't mind cellulose (foam), but in the roof space? Apparently, most of them don't like fibreglass, but I am sure spiders will love it if there are insects eating food there. Maybe I should populates spiders in the roof space. I think they will be there regardless. LOL There are a lot of potential issues in the tropics. And in Thailand, the list is endless! Flying temples? LOL

    It looks like my builder/architect is hesitant about recommending a 45 degrees roof pitch on a 2 story A-shape building (81 m2 house area). What do you think or know? I was going for a pyramid shape, but I think the cost will be higher. You agree? Are all soffits roof better than a mix of gable/soffit roofs? Apparently the builder tells me that ridge vents are not possible on metal sheet roofs. I have seen pics on the internet, but it might not be a local idea. It might be wise not to push the limit like you said. I am using the Australian metal sheet Bluescope. I hate noise and I fear birds are going to use the roof to hang there in the morning. The top of the roof could have spikes and wind gizmos to deter them from going there, but what about a 30 degree pitch roof with screws sticking out. I am afraid that the birds will try to land there and scrape the roof with their claws. Would a 45 degree roof prevent the whole issue? I think she thinks the thick metal sheet and the drop ceiling insulation (6 inches + 15 cm air gap) should do the trick on heat (and noise). Not sure biard noise can be mitigated unless I have a motion alarm triggering a loud outside speaker with a huge noise that birds don't like (rifle shots?). Anyway, I am worried about the birds. What do you think? The loudspeaker gizmo idea might be the cheapest and best idea as I have a rather big western oriented tree 3 meter from the house roof where they will be hanging in regardless.. My living quarters are upstairs, but I have bedrooms options on all levels. I have bathrooms oriented to the west (sun and tree side). I plan to build a double wall on the east side perhaps for noise and winter sun exposure (insulating the bedrooms further). I have no windows in my bedrooms.

    My 2 soffit sides and gable vents should be able to pick up the wind equally well as the corner seems to be oriented where they are supposed to be coming from (SSW according to a website on wind stats for Chiang Mai). Still, not being a geography major, the house has a large rice field on the north and east side that I am told could provide "microclimate" winds. In any case, like you said, a solar powered fan could do the trick to vent if there is no wind. And the soffit vents and gable vents are able to pick up some wind no matter where they come from. A cupola did not get any approval from my builder who was afraid of rain being driven by wind storms. Will an "attic" fan draw air from the conditioned space? As long as it is not a/c air (if I am not using it because the temp. does not require it), I guess I should not mind.)

  21. #21
    Thailand Expat David48atTD's Avatar
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    ^ Just removing the wall of text...

    Quote Originally Posted by CMdweller View Post
    Thanks a lot for that advice.
    I read all of it, but will need to read it again to get all of it. That was a lot of info to take in. Very useful. Thank you.

    I am a Canadian with NO metal sheet and tropical climate know-how.
    I know a bit about construction and can read, which led me to using metal sheet and convert my Thai wife to it
    (albeit helped by a builder that is a fan).

    I even have her agreeing to a white roof.

    You would use sarking reflective foil? Not the bubble-wrap?
    Is that to reflect more heat? To control potential leaks/condensation?

    I read termites/insects/pests don't mind cellulose (foam), but in the roof space?
    Apparently, most of them don't like fibreglass, but I am sure spiders will love it if there are insects eating food there.

    Maybe I should populates spiders in the roof space. I think they will be there regardless.

    LOL There are a lot of potential issues in the tropics. And in Thailand, the list is endless! Flying temples? LOL

    It looks like my builder/architect is hesitant about recommending a 45 degrees roof pitch on a 2 story A-shape
    building (81 m2 house area). What do you think or know?

    I was going for a pyramid shape, but I think the cost will be higher. You agree?

    Are all soffits roof better than a mix of gable/soffit roofs?

    Apparently the builder tells me that ridge vents are not possible on metal sheet roofs.
    I have seen pics on the internet, but it might not be a local idea.

    It might be side not to push the limit like you said. I am using the Australian metal sheet Bluescope.

    I hate noise and I fear birds are going to use the roof to hang there in the morning.

    The top of the roof could have spikes and wind gizmos to deter them from going there,
    but what about a 30 degree pitch roof with screws sticking out.

    I am afraid that the birds will try to land there and scrape the roof with their claws.

    Would a 45 degree roof prevent the whole issue?

    I think she thinks the thick metal sheet and the drop ceiling insulation (6 inches + 15 cm air gap) should do
    the trick on heat (and noise).

    Not sure bird noise can be mitigated unless I have a motion alarm triggering a loud outside speaker with a
    huge noise that birds don't like (rifle shots?).

    Anyway, I am worried about the birds. What do you think?

    The loudspeaker gizmo idea might be the cheapest and best idea as I have a rather big western oriented tree
    3 meter from the house roof where they will be hanging in regardless..

    My living quarters are upstairs, but I have bedrooms options on all levels.

    I have bathrooms oriented to the west (sun and tree side).
    I plan to build a double wall on the east side perhaps for noise and winter sun exposure (insulating the bedrooms further).

    I have no windows in my bedrooms. My 2 soffit sides and gable vents should be able to pick up the wind equally well as
    the corner seems to be oriented where they are supposed to be coming from (SSW according to a website on wind stats
    for Chiang Mai).

    Still, not being a geography major, the house has a large rice field on the north and east side that I am told could
    provide "microclimate" winds.

    In any case, like you said, a solar powered fan could do the trick to vent if there is no wind.
    And the soffit vents and gable vents are able to pick up some wind no matter where they come from.

    A cupola did not get any approval from my builder who was afraid of rain being driven by wind storms.
    Will an "attic" fan draw air from the conditioned space?

    As long as it is not a/c air (if I am not using it because the temp. does not require it), I guess I should not mind.)
    Anyone wish to give a reply?

  22. #22
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    Quote Originally Posted by CMdweller View Post
    It looks like my builder/architect is hesitant about recommending a 45 degrees roof pitch on a 2 story A-shape building (81 m2 house area). What do you think or know?
    Prefacing my comments by confessing that I have no direct experience, only information picked up as I plan my own house in Isan.

    I believe that 45 degree roof pitch is best for defeating the attempts by strong wind to lift your roof off. (Blame Mr. Bernoulli for this.) However, despite some strong winds, many, many houses in Thailand have much shallower roof pitches and seem to survive the storms. I am planning to go with 30 degrees.

    Can't say I have noticed birds being a problem on roofs. Not many birds left in Isan!

    The problem of roof vent fans sucking conditioned air out of the house below the attic seems to be an issue in modern homes elsewhere where the whole box is hermetically sealed. No such problem here. If there are vented soffits and a vented gable at one end then a fan at the other end should simply pull ambient air from outside through the attic space. That at least is my working hypothesis for my own build.

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    Quote Originally Posted by Shutree View Post
    Prefacing my comments by confessing that I have no direct experience, only information picked up as I plan my own house in Isan.

    I believe that 45 degree roof pitch is best for defeating the attempts by strong wind to lift your roof off. (Blame Mr. Bernoulli for this.) However, despite some strong winds, many, many houses in Thailand have much shallower roof pitches and seem to survive the storms. I am planning to go with 30 degrees.

    Can't say I have noticed birds being a problem on roofs. Not many birds left in Isan!

    The problem of roof vent fans sucking conditioned air out of the house below the attic seems to be an issue in modern homes elsewhere where the whole box is hermetically sealed. No such problem here. If there are vented soffits and a vented gable at one end then a fan at the other end should simply pull ambient air from outside through the attic space. That at least is my working hypothesis for my own build.
    Great advice backed up by explanations that are logical. Thanks.

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    Quote Originally Posted by David48atTD View Post
    Anyone wish to give a reply?
    I think I wrote too much? Sorry!

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    Quote Originally Posted by David48atTD View Post
    WOW ... interesting

    Would it be true that you guys haven't built a roof structure along these lines in Thailand yet?

    What seems reasonable as building technology and innovation in the West doesn't usually transform
    into practical construction with a builder in Thailand
    .


    I live in sub-tropicial Australia and in Thailand.

    A metal roof is a good idea because of it's low thermal retentive properties ... but usually the Thai Wife
    will decline because Cement Tiles 'look' the best. Good luck with that battle!


    Build by the KISS principle ... keep it simple.

    1/ Vent the soffit

    2/ Sarking under the roofing material to reflect the heat (I'm not keen on the spray on foam stuff)

    3/ Insulate the ceiling to reduce any heat transfer from the ceiling cavity/attic and reduce noise.
    ... What style of insulation you choose depends on what type of ceiling you have installed.

    4/ Vent the ceiling cavity/attic and the simplistic way is way is through a gable vent which is passive
    ... A gable vent with a fan or
    ... a roof vent ... though the roof vent when poorly fitted can leak.
    IMHO
    I do have some experience in Thai roofs.
    I do try to keep things simple KISS principle, but sometimes I get caught up with too much technology. The passive way is obviously the better way to go no need for electric.
    I will be using A/C when we build in Issan.

    As my member name kind of tells you of my nationality, Kiwi & Canadian.


    On Mrs KC’s house I designed a carport and had a local contractor source all the materials (gave him pretty much free rein on that) we ended up 5 years alter with the glue on foam & foil backing peeling off from the wrong adhesive used, Can’t find that contractor anywhere now.
    At a point we added to the carport and the next contractor saw the condition of the foam under the existing roof and guarantied this would not happen with the extension he would add to the existing roof, I had originally had the carport this size, but Mrs KC does not read plans and could not see the need for such a large carport, but she does like it now. And the foam/foil on the new extension is still like new 3yrs later. We deemed it too expensive to reroof the old roof at the time of the extension.


    Also her house attic cavity the reflective “sarking” that was originally installed has in some places degraded and is drooping down from the concrete tiles that are above it, so much for reflective barrier.


    CM dweller,
    I would not worry too much about the birds on the roof most of the time it will be too hot for them to walk on, our biggest problem with the carport is the pigeons and Minor birds like to sit on the rafters and poop on the car, LOL.


    As for Spray foam I said it was not good to spray on the underside of the metal roof for the obvious reasons, thermal expansion of dissimilar materials.
    But I would use rigid sheet foam under the roof battens between the rafters. Then on the top of the ceiling I would use the closed cell spray foam insulate and seal the ceiling from the attic.

    I have seen this on a few bird nests lofts to keep them cool. They also use a double qcon block wall with an air gap, near the bottom of the wall are a series of 6” pipes cut into the outer wall with a bug screen cover and at the top of the open cavity of the wall a bug screen is placed along the top, in all quite a cool dwelling. The bird house was about 10 meters wide by about 30 meters long and the equivalent of 3 stories high, quite a large structure, but of course no windows. This was just south of Hua Hin.

    David48atTD, what are your thoughts on a roof mounted solar water heater?

    I hope I have clarified my findings
    Lots of good info from you guys, good to be able to learn from each other.
    Sorry CMdweller no intent to highjack your thread.

    KC

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