Venting Hot Air From Rooms

[Riley'sLife]

I am attempting to design a small open-plan single storey house and to avoid the use of aircon yet draw in as much cooler night-time air as possible.

Is it worthwhile venting warm air to the outside either by using cathedral ceilings with window openings at high level taking advantage of natural convection, or by screened fan assisted ducting in normal ceilings through the roof void and the roof,.? Has anyone got vented ceilings? Are there any disadvantages? Any advice? They are used in northern Australia which has a similar climate to Thailand.

I plan double layer radiant barrier (foil) beneath the roof covering, together with eaves, ridge and gable-end venting and foil wrapped fibreglass ceiling insulation, and eaves extended at least 3m to shade all exterior walls.

[jackr]

Many folks have had success with the vents here from what I have read... have a search around. Keep it running with a window open to the cool side.

[Riley'sLife]

Thanks for the response Jackr. I have already searched the forum and discovered that a few people are using whole house fans and seen members' house photos showing dormer windows in single storey homes which I assume mean they are using cathedral ceilings and the dormer windows are used for ventilation. I was hoping some members with direct personal experience would share. Maybe my topic title is not sufficiently specific or maybe the DIY forum isn't the best location.

[genset]

Hi Riley,

A number of years ago, I rented a house in Florida with what was described as a 'whole house fan'. It was a single story house with a 'ridge vent' running the entire length of the roof, although I'm sure the standard vents you see on most thai houses would work just as well, you may simply have to increase the size or number of vents to accomodate the volume of air being moved. The house had a regular 8ft-ish ceiling, not cathedral and a large fan (approx 36") was located in a fairly central location, built into the ceiling and orientated to draw air from the ground floor and expel it into the roof cavity. Opening all the windows (or those located in rooms through which you wanted a significant flow of air) then turning on the fan resulted in a serious volume of air being drawn through every room simultaneously and worked really well (it was akin to standing in a wind tunnel in fact, quite pleasant on very hot days). I've never seen such a cooling system incorporated into a Thai home, but see no reason why it wouldn't work well, the only downside is the potential for a lot of dust to be drawn in with the air flow (depending on where you live).

Cheers, Genset

Edited March 2, 2010 by genset

[beechstreet]

I am planning on using several "Windworkers" to ventilate the high ceilings in our house (hope to start construction in a couple months). The design acts like a windsock to keep the device pointed in the right direction and even a slight breeze provides a positive draw.

The Windworker website is a little rough around the edges but the Australian architect Glenn Murcutt has used them before and that is a pretty solid endorsement. I have a sample and plan on rigging it up to our job site storage container to do a little testing.

Here's a photo from their website...I'll try to take some pictures of the sample I have and post it up if anyone is interested.

[Riley'sLife]

Thanks Genset for your Wholehouse Fan experience. Quite relevant too, as Florida also has a humid climate. Maybe this would be far more efficient than individual vents in each room each with its own fan to extract the warm air, which is what I had planned.

Interesting to hear that it produced a good flow of air. The place I'm designing is less than 100sqm. which is perhaps much smaller than your Florida rental. I hear what you say about the dust. I'm in the country so hopefully this would be less of an anoyance than in a town or city.

I had really planned the fan/s to work only when the outside air temp was lower than inside, like at night or when it's raining, but from what you say these 36" Wholehouse fans could give a pleasant breeze even when pulling in warm air, and that would mean I could throw out my portable fans.

The Windworker is an interesting concept beechstreet. Many people like the revolving stainless steel Whirlygigs. My only reservation would be from a subjective aeasthetic point of view. The Windworkers would look good on a very modern design I'm sure. The attraction of both the Whilygig and the Windworker is their zero energy requirement. Isn't the function of the Windworker more to balance air pressure within the roof void reducing air pressure in hurricane conditions, than to evacuate warm air from the living space? I'm not saying they wouldn't work, I just wonder about their efficiency. It would be of interest to many, I'm sure, if you could post your opinions again once you have got your sample rigged up on your storage container.

My other option of cathedral ceiling with opening casement windows set in roof dormers would also be zero energy and this is the attraction over the Wholehouse fan concept. However, I am primarily concerned with discovering the most efficient way of keeping cool (without aircon) and not so worried about being "green".

[wpcoe]

genset: What was the noise level of that whole house fan? My mother's house in S.California has one that was installed many years ago, and from day #1, it was so noisy, it is only tolerable to turn it on for short periods of time (like five minutes max). I had my mother buy thick felt, cut it into strips and glue them together to make a kind of gasket between the fan and the ceiling joists, but that only helped a little.

Did we get a bum fan and/or poor installation, or is that experience typical of an older design and if we replace it would it be tolerably quiet?

By noisy, I mean that if you stand outside at the street curb, you can hear it.

Noise aside, it *does* bring in lots of outside air.

[canopy]

I hear what you say about the dust. I'm in the country so hopefully this would be less of an anoyance than in a town or city.

Careful about this assumption if you are not there right now. The countryside in many parts of Thailand this time of year is ablaze. There are unbelievable amounts of smoke and dust in the air limiting visibility. And it isn't just ashes, but all those poisons they spray on the fields going airborne. Below is what the air quality is like today in some places. It's mainly unhealthy and today is a pretty good day. Over 100,000 people from the countryside have already gone to the hospital for treatment this year.

[chrgrims]

wow, thats interesting info canopy. how does it compare to an average size city in europe?

i was browsing the aqnis website and tried to find updated info in english on the various thai provinces, but havent found anything yet. let me know if you have the link please.

[splitlid]

funnily enough, i have just finished a design concept which has exactly what you are interested in.the entry is connected to the lounge,dining room and kitchen so all hot air can be vented up and out.

[canopy]

1) The air quality index in european cities is many times better than the Thai countryside now. And sadly enough, Bangkok air is not as good as europe or clean asian cities yet is also several times better than the countryside. The unhealthy air situation goes for several months of each year. I found it interesting among various things they are burning in Phetchabun are mountain forests owned by the king that are being burned down systematically one day at a time, section by section. I asked why they are doing this and everyone knows who and why and are totally indifferent: a hunter is flushing out game to shoot. Links to requested air qualities are below:

Daily air quality in Thai provinces

Daily air quality in Bangkok

Daily air quality in Europe

2) Back more on topic with this thread. It seems the chief need for ventilating a house is due to the thermal mass of the walls. The brick and concrete walls they make here soak up the heat of the sun and reflect it inside the building for hours even after it cools off. A greener wall system or shading the walls would be a favorable solution.

[jackr]

funnily enough, i have just finished a design concept which has exactly what you are interested in.the entry is connected to the lounge,dining room and kitchen so all hot air can be vented up and out.

Nice look that.