How to cool roof crawl space





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  1. #1
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    Default How to cool roof crawl space

    We are in the process of building a new room next to the swimming pool, that is to be used as an entertainment centre. The dimensions of the room is roughly 8m x 5m and is a free-standing structure. The roof will be Chromadeck at a 5 degree angle and the ceiling will be directly under the beams. The room will be air conditioned.

    Now my brains tell me that the roof needs to be cooled / isolated properly to save on aircon costs.

    The constractor wants to install a whirlybird with a pipe going through the crawl space (I know the space will be too small to crawl in but for the lack if a better term), and suck air directly out of the room.

    My problem with this approach is that it will do nothing to cool the roof and crawl space and it will merely be sucking the air conditioned air out of the room.

    I first thought that a whirlybird sucking crawlspace air is the answer but I am not convinced that we have enough wind in Pretoria to make it work effectively.

    Isolation is an option but it seems pricey.

    My thinking now is to buy two DC fans and build it into the filler brick rows between the roof and the ceiling. The beams are 220mm and we can add 50mm + 50mm for brandering on top of and below the beams. This gives us 320mm so theoretically a 300mm fan should fit nicely.

    The one fan blows in air and the other extracts on the opposite side of the structure.

    The next step is to smack a solar panel on the roof and connect the fans directly to it.

    My thinking is that when the sun shines and the roof heats up - the fans kick in and cool down the crawl space. At night the fans shut down when there is no need in any case to cool down the crawlspace.

    The biggest obstacle I can think of is the limited crawlspace and the beams blocking much of the air flow. Other than that my brains tell me that the plan should work.

    What do you guys think? Any advice and suggestions welcome.
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  2. #2
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    Default Re: How to cool roof crawl space

    Have a look at Lamdaboard - insulation and ceiling all in one, with zero maintenance.

    www.rigifoam.com

  3. #3
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    Default Re: How to cool roof crawl space

    Thanks, I have just given them a ring.
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  4. #4
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    Default Re: How to cool roof crawl space

    "solar panel on the roof and connect the fans" Sounds costly and future maintenance.

    Go the insulated ceiling route.

    There are very nice plastic whirlybirds these days, I am going that route on my main house and one of the cottages.

    but insulate first.

    limited crawlspace and the beams blocking much of the air flow, one option - insulation.

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  5. #5
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    Default Re: How to cool roof crawl space

    My boss many years back cooled down his patio next to the pool by directing the pool water after the filter to flow over the roof. Heated the pool and cooled the patio plus increased somewhat water evaporation and added a bit more dust to pool.

    I would put insulation between the ceiling and roof. Passive solution = once off cost and maintenance free. Green and pink stuff are cheap. Helps during winter with coldness and summer with the heat.
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  6. #6
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    Default Re: How to cool roof crawl space

    You will have to combine insulation and ventilation.
    Insulation is not negotiable. There are ceiling / insulation combinations which could just be your best option.
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  7. #7
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    Default Re: How to cool roof crawl space

    I have exactly that (lamdaboard type) in my braai room. Had boards made to my specific requirements. One long board from start to end, purlin in between boards, chromadek flat roof, makes a huge difference, no heat coming through ceiling.

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    Last edited by staalwol; 2019/11/13 at 10:48 AM.
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  8. #8
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    Default Re: How to cool roof crawl space

    My best advise - don't crawl around in the roof space.

    Forced ventilation works well, just remember to be able to disable it in winter, there are times when trapping warm air in the void is an advantage.
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  9. #9
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    Default Re: How to cool roof crawl space

    http://isoboard.com

    Isolation and ceiling in one go. And no, it does not burn.
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  10. #10
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    Default Re: How to cool roof crawl space

    The whirlybird extractor does not need any wind to work. It simply uses rising hot air to work so the hotter it becomes in the roof, the faster it turns, providing it can draw enough air into the roof...
    Taking it into the room is not the right way. It should extract the hot air inside the roof outwards but I would also look at placing alububble reflective insulation under the sheeting and then either a insulating ceiling like isoboard or as mentioned Lamdaboard.

    Not sure about pricing for these mentioned ceilings but a conventional ceiling with a few rolls of Isotherm should do the trick as well but if it was my house, depending on pricing I would do both...

    Best is to get some quotes and see which is the most cost effective.
    If Force is not the solution, not enough of it was applied....

  11. #11
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    Default Re: How to cool roof crawl space

    The Lambdaboard rep is coming to see me this afternoon.
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  12. #12
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    Default Re: How to cool roof crawl space

    The Lamdaboard looks like a good product. We will probably go with that.
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  13. #13
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    Default Re: How to cool roof crawl space

    Quote Originally Posted by 4eTouareg View Post
    You will have to combine insulation and ventilation.
    Insulation is not negotiable. There are ceiling / insulation combinations which could just be your best option.
    This. Do both.

    Ventilation should both draw and expel air from outside. Regulate room air through windows. The rationale for ceiling ventilation is that the temperature in the cavity will then never rise significantly higher than the outside air temperature. If enclosed, the temperature below the roof sheets can go very high (50+, maybe higher). That is like having an overhead heater in summer! If you can close it off in winter, you will gain some solar heat, but the benefit in summer will outweigh the loss in winter.

    You should base your insulation material selection on the cost per R-value. I.e. one material with low R-value may be cheap enough to put in more layers than something with better insulation at double the cost. I don't know Lambdaboard, but know Isoboard is a good insulator. A simple rhinoboard ceiling with Aerolite may be cheaper than newer products. Just don't use something like Isotherm (green fluffy stuff) against the Chromadeck, as these might get too hot and melt the Isotherm. Isotherm is really cheap, so check the specs. Maybe your space is adequate.
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  14. #14
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    Default Re: How to cool roof crawl space

    Quote Originally Posted by albertvl View Post
    The Lamdaboard looks like a good product. We will probably go with that.
    Is it just an isolation product or a finished ceiling product?
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  15. #15
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    Default Re: How to cool roof crawl space

    Quote Originally Posted by thabogrobler View Post
    Is it just an isolation product or a finished ceiling product?
    It replaces normal ceilingboard.
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  16. #16
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    Default Re: How to cool roof crawl space

    I think we will see how the Lamdaboard fares and if necessary, add ventilation afterwards.
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  17. #17
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    Default Re: How to cool roof crawl space

    I am retired now but still do some work in the construction industry recently I was given some lamdaboards so replaced half of my outside wendy hut from rhinoboard with insulation , not much difference but when one touches the ceiling the Lamdaboard is much cooler , will replace the other half when I get some more
    So yes the Lamdaboard works well, remember this is a wendy hut so no space between sheeting and ceiling. in my house which is 50 years old I removed that pink (black) insulation with sisalation works as well but one can get into the roof space
    Last edited by 12richardk; 2019/11/13 at 05:27 PM.
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  18. #18
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    Default Re: How to cool roof crawl space

    My previous house had a corrugated roof garage, no insulation. Original color red, painted it white! What a difference!!! Cheapest solution by far. Do it first before embarking on other options

  19. #19
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    Default Re: How to cool roof crawl space

    MUST be white chromadec firstly. Beneath the chromadec I insulated mine further with the silver bubble insulation. Believe me I paid my fair share in school fees before I did the above.

  20. #20
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    Default Re: How to cool roof crawl space

    White Chromadeck is indeed cooler than the other colours, but a friend did some research and found that the other lighter colours with the silver tint in are not much worse. Also the white tends to show dust and fungi much quicker. Depending on your climate, you have to clean it every few years. That's easy enough on a lean-to garage roof, but more difficult on steep sections.
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