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Topic # 113789 28-Jan-2013 13:34 Send private message

So, it's hot this week, really hot. Too hot to easily sleep, really. I'm after thoughts about how to cool my house down, especially the bedroom at night. Sorry for the rather long post!

I have a pretty old house, around 100 years, old enough that no-one really knows how old it is. It's a single level weatherboard house, 120 odd square meters. The front of the house has the living area, three bedrooms, bathroom, and lounge. A single standard door leads through to a big open plan kitchen/dining, with an office and laundry off it. The house has very good insulation in the ceiling, walls, and under the floor, and retrofit double glazed windows in the living area of the house. It resists ambient air temp pretty well, but the big windows let the sun's heat in. In winter it's pretty good, if it's 5 degrees outside it'll drop from 20 to 18 overnight with no heating on. Problem is the same thing happens in summer.

The bedroom/lounge area gets morning and early afternoon sun, but with curtains we can block it out pretty easily. It gets up to around 22-23 degrees when ambient is around 28. Opening the windows doesn't help much, there's virtually no breeze, and even if there is not much goes through the house.

The kitchen, dining and office areas have dark blinds and lots of windows. It can get up to 35 degrees or higher on a sunny day. There's a bit of a catch 22, if you open the windows you have to open the blinds which lets the sun in. Keep them closed and the heat gets in anyway. I'll address that with light color window coverings one day, but you have to be careful in kitchens.

The house has an air conditioner/heat pump in both areas, a big 10KW unit in the living area, a smaller but still decent 7KW unit in the kitchen.  To get to our bedroom the cool air (or in winter, heated air) has to go around a 180 degree turn via the hallway, we sometimes use a pedastool fan to help with that. The air conditioner in the kitchen pushes air down the same hallway, which means only one 90 degree turn. Getting the air temperature down when they're on is pretty easy, it only takes 20 minutes. What I find though is even if we get the air down to say 18 degrees with the air conditioners on for an hour it soon heats up, I presume because the carpet, the walls, the tons of wood that make up the house are still at 22+ degrees.

The house also has a cheap DVS unit. Outlets go into the kitchen and the hallway, though I've set it to only operate when the roof cavity's below 22 degrees in summer. I also have it turn off at night because the noise bothers me, though I could probably live with it, but there's not much point because the outlet isn't near the master bedroom and wouldn't help air movement much.

If it gets super hot we can just move into our main spare room, right in front of the big heat pump, which can make any temperature we like within about 5 minutes. We like our room though.

Does anyone have any thoughts on cooling or ventilation? It's rare to need it in Wellington, so I wouldn't compromise the winter insulation for the few days that it'd be helpful in summer. I guess we need to either add some kind of ventilation, some air movement (not too much as it'd be noisy or wake us during the night), cool the air, or stop it getting hot in the first place.




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  Reply # 751991 28-Jan-2013 13:44 Send private message

Do you have overhangs on the windows? So they let sun in in the winter, but keeps the sun out in the summer. That is probably theonly way to stop it over heating.



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  Reply # 751992 28-Jan-2013 13:47 Send private message

The house has quite wide eaves, around a meter or so, maybe a bit more. The sun's mostly overhead, but not directly. Some sun comes in during the day, but it's late afternoon when the sun's low in the sky that a lot of sun/heat gets into the house. We block it with the dark blinds I mentioned, not that successfully.




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  Reply # 752004 28-Jan-2013 14:16 Send private message

Yes. it's the west side windows that are the worst for summer heating and can be a problem with the most energy efficient houses e.g Passive Haus. Standard theory is to minimize those windows but other factors such as views etc often affect that.

What will work best is shading from outside as mentioned, such as a pergolar or foliage, outside shade blinds (they can be automated for convenience). Inside blinds or curtains will help but not as good. Perhaps some of the mirror film if the look isn't important(not sure how well it works).

Otherwise open windows to get a cross breeze going through.

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  Reply # 752010 28-Jan-2013 14:20 Send private message

Window film is probably the quickest place to start. Try to stop it getting hot in the first place. Perhaps ventilate the roof cavity, but you've got pretty good insulation upstairs anyway. I'd look at blocking the direct sunlight in the fist instance, and get some air moving (assuming the outside air is cooler in the first place!).

We're going through something similar.  We're brick, which is great towards winter as the sun heats the bricks during the day.  In summer though the house is a heat sink that radiates warmth well into the night, even if you don't want it.  Trying to get the kids to sleep when it's still daylight outside and it's too warm for any covers just isn't pleasant.

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  Reply # 752019 28-Jan-2013 14:30 Send private message

When I need to go to bed, I crank up the fan to max and position it towards me.
Does the trick haha!




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  Reply # 752026 28-Jan-2013 14:36 Send private message

what about portable air conditioners would(do?) they work?  at cooling down a room?



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  Reply # 752028 28-Jan-2013 14:39 Send private message

Around 1/2 the area of our west side wall is glass, great for winter (well it would be if it was double glazed), not so good for summer! Outdoor shades sound like a good idea, though I'm not sure how practical they are, especially since I want to reclad sooner or later, plus that area of the house isn't my main concern.

As I said the kitchen gets pretty warm, but the living area avoids that heat. The bedroom area gets up to 22 degrees, it's just getting it down a few degrees. Windows don't help much, you need a cross breeze which we don't get. A huge extractor fan mounted in a window might help. A better DVS might help, but it'd need to draw fresh air in during summer, and in winter use warmer air from the ceiling cavity. My problem with a DVS is you have to cut large holes in your ceiling, which lets heat escape in winter.

Another thing I've thought of is putting another (our third) air conditioner into our bedroom. It may be something we do eventually, maybe even putting in a unit that can do all the bedrooms. A portable unit isn't a good option, we have one at work, they're SUPER loud. Even a fan in the hallway isn't ideal, as it's really bright out there due to street lights through the front door - I'm working on that though.

It sounds to me like we might just have to sleep in the spare room with the air conditioner on until the heat goes away! That or use a noisy fan.




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  Reply # 752029 28-Jan-2013 14:43 Send private message


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  Reply # 752046 28-Jan-2013 15:24 Send private message

Get a ceiling fan. Best $200 I have spend since moving down to Canterbury. Spend more to get one with Wooden blades as I find the metal ones make more noise.

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  Reply # 752052 28-Jan-2013 15:33 Send private message

Given that heat rises, the best way to get heat out of the house is a thermal chimney. We have a dual layer brick house and once hot it stays hot until we open the skylights... The cold/cool/outside air comes in the door/windows and the hot air vents out the roof. Kevin McCloud from Grand Designs has built a housing estatge with thermal chimneys for use in the UK, they are pretty good idea.

You could also try a heat transfer kit. They can transfer the cold as well, which is like a DVS, but sucks the air out of one room and pushes into another. Re: your concern about insulation. Some come with insulated flexible pipes (my central heating ducts are like this).

Or you could try a balanced ventilation system which circulates fresh air balanced with a heat recovery system. I think you can bypass/reverse the heat recovery option for summer.

Jon



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  Reply # 752054 28-Jan-2013 15:36 Send private message

Ceiling fan's a pretty good idea, but you still have to cool it. A proper heat recovery DVS that would do the job as well, but lots of holes in the ceiling.

Insulated ducts would help a little, but not much. The heat from your room would still go up, through the rather thin insulation, up the pipes to wherever it goes, etc. It's still a fairly large hole in your insulation. I always though floor mounted would make more sense, but then there'd be holes in your floor. Wall mounted would be an idea... maybe not a good idea, but an idea nonetheless.




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  Reply # 752055 28-Jan-2013 15:37 Send private message

Taking the skylight thought a bit further, if the heat is a usual thing put an extractor fan like in the bathroom in the ceiling so all it does is suck the hot air out. If you put the fan motor in the ceiling it should be far enough away for minimal noise, you could insulate the pipe, and the negative pressure would suck the cold air from other parts of the house?

Jon



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  Reply # 752057 28-Jan-2013 15:39 Send private message

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.




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  Reply # 752058 28-Jan-2013 15:40 Send private message

Our ducts are better insulated than the ceiling ie. ~ 4 inch thick around the pipe and then sealed in plastic. The piece of ceiling where the duct come through are insulated as well, so I can't see the ceiling itself, so not sure where the heat leak is?



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  Reply # 752060 28-Jan-2013 15:41 Send private message

That's interesting, that's proper insulation around the ducts. The question is if it's super cold up there where do they connect, and does it still give a heat chimney effect?

Bit off topic, but interesting.




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