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  1. #1
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    Roof Construction & Cooling

    Hi all,

    this is the reason I wanted to join Teakdoor, because you seem to have the best by far construction forum for Thailand, so was hoping to get some advice.

    Family are building a new house for my wife's Auntie on family plot, they have decided to have high loft style ceiling in main living area, so height will go right up to roof pitch, now this probably wouldn't be a problem in cooler countries, but in the tropics, I'm not sure what that will mean when trying to keep the house cool?

    Am I right in thinking, best way to do this is to have a vented double roof? I've tried badly to illustrate what I mean below, soffit vents at bottom and a double skin going up to roof ridge, and then ridge or gable end vents.

    My question is this, if outer skin is normal tile roof, and inner skin has reflective foil, what would be the ideal distance to have between them to provide insulation and ventilation? Would 30cm/12" be enough?

    Thanks




  2. #2
    Thailand Expat David48atTD's Avatar
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    Here is a start ... Roof vent airflow calculation?

    Have look back through some older threads on here

  3. #3
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    Excellent I missed that one.

  4. #4
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    The basic premise that 'heat rises' should be remembered of course but heat also radiates.

    If you create a skin between the actual roof tiles and your 'ceiling', that's good, and bad if you do not vent the space between.

    You need to ensure heat does not build up between the two roofs,and you achieve that by venting that roof void.

    fit a vent at each end, in the gables and the air flow through the roof will prevent heat build up and also lower the chance of any radiant heat coming through your ceiling.

    You could do as I did and create something similar to a cathedral ceiling... where the ceiling, or a section of it, rises up into the roof space, thus raising the ceiling height.

    In my case, the walls were 3m, and we added another 7-800mm in the raised ceiling. good news for the heat rises phenomenon.

    We also vented the roof void at each gable.

    Ours was not a full cathedral ceiling, which i think is what you are describing but a smaller version of it. It works well for us.


    Hope this helps and ..good luck with yours!

  5. #5
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    Quote Originally Posted by Thai Dhupp View Post
    The basic premise that 'heat rises' should be remembered of course but heat also radiates.

    If you create a skin between the actual roof tiles and your 'ceiling', that's good, and bad if you do not vent the space between.

    You need to ensure heat does not build up between the two roofs,and you achieve that by venting that roof void.

    fit a vent at each end, in the gables and the air flow through the roof will prevent heat build up and also lower the chance of any radiant heat coming through your ceiling.

    You could do as I did and create something similar to a cathedral ceiling... where the ceiling, or a section of it, rises up into the roof space, thus raising the ceiling height.

    In my case, the walls were 3m, and we added another 7-800mm in the raised ceiling. good news for the heat rises phenomenon.

    We also vented the roof void at each gable.

    Ours was not a full cathedral ceiling, which i think is what you are describing but a smaller version of it. It works well for us.


    Hope this helps and ..good luck with yours!
    Thanks!! I think I saw your build thread but hadn't looked at it yet, will have a read later, it might be exactly what I'm looking for

  6. #6
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    knowsitlike's Avatar
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    ^ Wish I could illustrate as ‘badly’ as that!

  7. #7
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    Quote Originally Posted by sourmanflint View Post
    then ridge or gable end vents
    The gable vents will reduce the risk of ridge leakage. Look around at older Thai houses, most have gable vents.

    Prior to installing the interior "roof", if you're happy seeing the underside of the exterior roof and the noise of the rain, try it without. The addition of the interior roof is easily added later if deemed necessary.
    Last edited by OhOh; 22-05-2020 at 12:19 PM.
    A tray full of GOLD is not worth a moment in time.

  8. #8
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    Quote Originally Posted by OhOh View Post
    The gable vents will reduce the risk of ridge leakage. Look around at older Thai houses, most have gable vents.

    Prior to installing the interior "roof", if you're happy seeing the underside of the exterior roof and the noise of the rain, try it without. The addition of the interior roof is easily added later if deemed necessary.
    The house will definitely have gable end vents, but these will directly vent the living space rather than the roof void. Phrae gets horrendously hot March-May most days are 38C and up and 45C is not uncommon so I think having a roof without insulation and passive cooling is going to be a bit uncomfortable. Also I'm pretty sure that once done, the chances of anyone agreeing to "improvements" is very slim, as they are not very keen on even basic maintenance, something I will never understand

    cheers

  9. #9
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    Your "Design" is the same as used in Canada & northern USA. This works well to keep the temperature of the outer roof separate from the Inner insulated roof, the flow of the air cools the space between and takes the heat up and out the ridge vent a well proven design, that works well in a multitude of climates. Where I lived in Canada in the summer 35c was not unheard of as was -35c in winter.
    Shape of this roof is called a "Cathedral Ceiling".

    You ask if 30 cm would be enough, this would be more than enough, a 15cm uninterrupted air flow space would be more than adequate, don’t forget to take into consideration the structure required to support the tile roof. Finding a ridge vent to add to the roof might be a struggle here, this is why so many roofs have Gable ends to promote air flow, the limitation is with the wind direction, they only really work when the air is flowing towards the face of the Gable end. Whereas the ridge vent works well in almost any direction.
    As for “Reflective Foil” it is a sham IT Does not work.
    I have yet to see a roof with the reflective foil still attached 5 yrs later here in L.O.S. If you’re looking for good insulation for the inner roof, I would go with 5 to 10 cm of EPS foam with gypsum board on the underside this will need to be framed separately also. This will stop any radiant and convective heat from reaching the interior of the room.

    Now if you do follow this, the other question comes into the overall picture of keeping the house cool, what insulation to be used in the walls? Are you going to use double glazed windows all these add to reducing any A/C usage and reduce ones electrical consumption. If A/C is to be used.

    Good luck
    Moved back to LOS, living in Issan

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