cooling a house by loft extraction

Hi,

Reading some old posts here, it was suggested you could keep your house cooler by removing heat from the loft. I can see how the loft gets hot under the full sun but if you have decent amounts of insulation between the loft and the first floor, then wouldn't that limit how much heat is transmitted from loft into the house?

Has anyone tried this? What size fan did you use? I'm thinking a small

4" fan designed for a small bathroom isn't going to cope with a loft which is as long and wide as the whole house?

TIA

Reply to
Fred
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I thought the idea was to install a large fan in the loft hatch, blowing into the loft, so new air is drawn into the house, which obviously needs the air outside to be cooler than the air in the house to make it of any benefit, this in turn would then push the hot air from the loft out, assuming you have some ventilation to the outside in the loft.

Toby...

Reply to
Toby

Fred brought next idea :

Just providing a free flow for air up to the loft then out from there will do it via convection currents. We just open the loft window to get the air to flow up through the house and out.

Reply to
Harry Bloomfield

Yes. However, well insulated houses usually (although not always) have no internal thermal capacity, so incredibly little leaking through, combined what anything coming through walls/windows, has an instant heating effect.

An old house with solid internal and external walls and no loft insulation stays much cooler, because of the thermal inertia of the building structure.

I've lived in both types.

That's the easiest, and what I do. I have a 10" expelair fan in the loft hatch (and another hatch without, for winter). It's difficult to know exactly how much difference it makes. It does instantly knock a degree or so off the loft temperature when it switches on, but what effect it has being on all day verses what the temperature would have been without it, it's impossible to do a comparison.

However, it would be better to extract the loft air near the top of the roof, via a gable end fan. Since this house is built of engineering bricks and it took me long enough to make a 4" hole at waist height, I've no intention of doing a 10" or larger hole 30' up in the air.

Reply to
Andrew Gabriel

Andrew Gabriel wibbled on Monday 09 August 2010 17:44

Yep. My last house was a Crest special and it was bloody awful in the summer, though OK in the winter.

Current one which is 95% brick walls throughout and solid concrete floor is a joy in the recent heatwaves.

Reply to
Tim Watts

If you run it at night as well it should store a nice amount of coolth in the house's mass, reducing peak temp the following day.

NT

Reply to
Tabby

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