Cooling houses in hot weather

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jonherries

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#752061 28-Jan-2013 15:42

timmmay: Not a bad idea, an extractor. Again it's the hole in the ceiling thing, you might as well have a proper DVS if you do that.

With a skylight it'd need to be double glazed, and covered so as not to let light in. Plus in my house a skylight in the bedroom would just lead into the huge tall ceiling, which until well after sunset would be pretty warm. I had a temperature monitor up there once, it got up to around 40 degrees from memory. It's not well ventilated, which is handy in winter, but not so much in summer.

Our skylights are double glazed with roller blind and remote electric opening with a rain sensor. Just the kind a geek would like ;)

Jon

jonherries

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#752063 28-Jan-2013 15:45

Sorry maybe I mixed you up. In my house:

Thermal chimney - skylights
Ceiling holes - central heating

Was just saying you could use the same ducting for a thermal chimney, with a fan for extra volume. If the fan isn't running then no air moves, so you don't lose heat in the winter. It just fills the duct and the duct isn't that big.

Jon

timmmay

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#752077 28-Jan-2013 16:16

jonherries: Our skylights are double glazed with roller blind and remote electric opening with a rain sensor. Just the kind a geek would like ;)

Ah so there's a skylight that goes all the way up from the room. Interesting idea. I'm completely adverse to any light coming in at all, so it'd have to be a very good blind. Sounds like a nice system though :)

jonherries: Sorry maybe I mixed you up. In my house:

Thermal chimney - skylights
Ceiling holes - central heating

Was just saying you could use the same ducting for a thermal chimney, with a fan for extra volume. If the fan isn't running then no air moves, so you don't lose heat in the winter. It just fills the duct and the duct isn't that big.

Yes ceiling holes is central heating, DVS, that sort of thing. Heat naturally rises so even with no fan on and insulated ducts it could lose heat. Probably not much though! Depends where/how they terminate. If they're open to the ceiling cavity then they'll probably act like holes in the ceiling.

New houses are pretty warm in winter, with an old house every little bit counts.

jonherries

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#752078 28-Jan-2013 16:18

The central heating ducts are connected to the gas fired central heating unit. It is a brivis one.

Jon

stuzzo

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#752104 28-Jan-2013 17:15

This is not a problem that should require thousands of dollars to solve and ongoing power costs. In the case of a DVS all it can do is equilize the temperature throughout the house over time but with the low angle evening sun from the west providing radiant heat that room is still likely to be uncomfortable while the sun is up and well after. The extractor fan idea might work quite well but I think the real answer lies at your local garden center ie outside.

Also, an obvious one is to keep some windows open at night. As it cools outside you want it to aid the cooling inside.

mattwnz

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#752116 28-Jan-2013 17:39

Cross ventilation by having windows at the bottom and top of the wall to allow cool air in at the bottom, and hot air escaping at the top of the room. Also having deciduous trees near the window, which provide shading in the winter, and allow sun in the winter. It is a natural way of keeping a house cool. Or if you put up a pergola, grow something up it that is decidious, and can achive the same result as a tree, without having to wait for the tree to get big. But those solutions can take a few years to establish themselves.

timmmay

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#752212 28-Jan-2013 19:41

It's a bit difficult to just add new windows. In the direction the sun sets we have a 5m wide deck, then a 5m wide lawn, then trees. The effect of the trees is they block the low winter sun, but don't get in the way of the summer sun. I take the idea though, for that room we have to put something in the way of the sun.

I think we're focusing on that room a bit much. Sure it gets hot, but between there and the rest of the house is a fully insulated wall and a closed door, so they're almost different houses.

The main problem is cooling the bedroom, and moving air. Windows don't help much on the awesome still days we have, so I guess the only option is mechanical ventilation.

A DVS doesn't just equalize temperatures, a heat recovery unit also uses outside air to cool in summer, and heat exchangers in winter to prewarm that outside air. Instead of using dusty air from my ceiling cavity (mine's super dusty) it uses fresh, warmed or cooled air. I'll do it one day, I guess, with those super insulated ducts I've learned about today :)

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Niel

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#752290 28-Jan-2013 21:04

Window tint:
Almost all window tint absorbs solar energy and itself heats up. Not too bad if installed on the outside, but bad if installed on the inside (like most are). So instead of the floor radiating the heat, it is the solar film radiating the heat. There are 2 exceptions, reflective film and a very expensive one from 3M. The one from 3M cuts 70%-90% or the infra-red but only about 15% of visible light. It is however about 3x the price of normal film. It (or a similar one) is used in Toyota windscreens (and a few other cars) to lower aircon requirements, and is becoming very popular with electric cars.

Ventilation system:
In our old home I was able to setup the window mounted aircon to circulate air through the lounge then dining room then kitchen then hallway back into the living room. It created enough turbulence to get cool air into the bedrooms off the hallway.
But if you can't do that, and like me you keep windows closed as you get a bad reaction from mosquito bites, then you need to do ventilation. I am about to do that in our new home. I'm using acoustic and thermally insulated ducting, will be either 150mm or 200mm diameter. It will be installed like a heat transfer system, but because an aircon is not a concentrated heat source I will be sucking the stale air out of the bedrooms and blow it into the living room so that cooled air from the living room will go through the hallway to the bedrooms. A future upgrade will be a thermostat to operate an air handler to draw in cool outside air and reduce my heat pump load. I might do the same for drawing warm air from the roof space in winter, but not keen on getting into the ceiling for replacing filters as I'm not good with maintenance schedules.

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bfginger

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#752828 29-Jan-2013 18:11

In some houses the colour of the roof can have a big influence on room temperature during summertime.

timmmay

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#752833 29-Jan-2013 18:20

Good point, good idea. The roof's light grey, though it's very well insulated between the house and the ceiling cavity (about a foot of insulation in most places) so it's probably not a leading cause IMHO.

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