some thoughts from Dozer
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Peter M: house ventilation systems

from Peter M I’ve been doing some research on the net regarding roof ventilation. It’s become quite a sophiscated topic and there seems to be many new ways to reduce the heat build up effect in houses. Namely, their are non elec. turbine and wind turbines that force air out of the attic and than draw cool air in. Attic fans also have the benefit of being activated by built in thermometers which turn on at a given temp.

Also their are whole house systems that circulate cool air into the house, which apparently cool the house significantly. I’m going to see just what is available here in thailand. But it would seem to be that cooling house systems would be one of the most significant items to look at interms of living in thailand and reducing our yearly electric bills.

Without dwelling on conspiracy theories, the electrical company of thailand is definitely not interested in alternative sources of cooling other than AC.

will keep you posted.


  1. There are two parts to roof ventilation: But first the Physics.

    When you cool your house with AC, you are increasing the difference in temperature between inside the house (cool) and outside the house (hot).

    Heat (like water) wil always try to find the same level, so heat from outside your house will flow into the cool rooms, through open doors/windows/draughts and through walls/ceilings.

    The greater the difference in temp, the faster the heat will flow.

    Roofs play a part in this but have the added problem that they loft space between the ceilings of your rooms and the roof tiles acts like a solar heated oven (temperatures in the roof space can clime to 50 or 60 Degrees Centigrade).

    So your room is at 22 Deg C and the space above it is at 50 Deg C (You can if you put your hand up feel the heat radiating from your ceiling)

    To combat this the first thing you should do is add loft insulation: I recommend at least 4″ of Fibre Glass – You can buy this in pre packed pads that have the added advantage of keeping the fibre inside and stop it getting into your house and LUNGS! SAFETY NOTE: If you are laying fibre glass, always wear a face mask, and wear a one piece work boiler suit – the glass fibres can damage your lungs and can cause skin problems – so shower well afer fitting the fibre glass.

    Next add the roof ventilation: If you are building new, you might want to consider a roof design that allows air to enter under the eves and exit through a doubl roof over the apex (sort of one small roof ontop of the main roof with a gap in between to allow air flow). This is effective and requires no fans as the roof heating up causes air to flow)

    Don’t forget to fit anti insect gause across all vents!

    If your house is already built, get a builder to knock a single window sized hole in each gable end. Fit a louvered window screen – Anti Insect Gause – AND Anti Burglar Bars. Natural airflow will greatly reduce the heat in the roof space. (fit these ventilation windows as high as you can into the apex of the roof for best effect.

    Check that out and if you are not seeing enough reduction in heat fit a fan inside that blows air out of one of the ventilation windows. (Work with the physics) fit the fan on the warmer side of the house air will naturally flow Cool to Hot.

    Oh and fit the fan on a beam that is attached to the walls or concrete structure of the house NOT the roofing metal and certainly not in contact with the ceiling supports otherwise you might find that your fan rattles the whole roof/ceiling.

    A Temperature switch on the fan is a good idea as it will only operate when it needs to.

  2. I meant to say, systems that drag more air through the house have a disadvantage that with the air comes a lot of dust!

  3. Thanks Itchy. Makes alot of sense. Yesterday I found a man who specializes in wind turbines. He attaches them to the giprock sheets and sells them in various sizes. My main concern with these is there usefulness when there is no wind. I’m going to use your ideas for the overhang and see what I can do about adopting a mini roof on top!

  4. what a lot of hot air generated on this topic?

    There is a standard thai way of ventilating roof voids. they use a pair of louvred windows with insect gauze. commonly available in m ost suppliers, they are fitted into gables ends, preferably at both ends which allows wind to circulate freely, and importantly allow window pressure to equalise

    anyone come up with a design for a sranding fan powered by something other than local electricity (not a car battery please) say a propane gas tank? steam driven?

  5. forgot another point re cooling I have an exposee on this topic elswhere in this site and it consists of keeping th cinderblock work wet using a perforated hose to spray water

    the evaporative cooling is quite effective and very cheap

    another way which I use on my boss is the “wet tee shirt” principle combined with a simple fan

  6. Hi Robin: Yes I’ve heard this as well. Someone has suggested a perforated hose running on both sides of the roof crest. Would this be in line with your thoughts. I take it the cost would be in the pumping of the recirculated water na? I spend far too much time on this right now because I’m envisioning living in a 120 sqm second floor without walls and a 10 meter high ceiling.

    1. instead of fiberglass use rockwool
    2. sprinkle water over the roof, don’t think about recylcing that, let it soak into the ground around your house

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