Methods of cooling a room

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With this hot weather and working in an air-conditioned office, I've been dreaming of trying to get our house's temperature down to something more comfortable.
Obviously, buying an air-conditioning unit would probably be the best way - though I think these are quite pricey (I think anything more than 150 would be out). Also the cheaper ones are very noisy aren't they? Plus, ideally I'd want a split unit... anyway
I've heard about these evaporative coolers - and I've also heard how people think they're snake-oil, and I understand how they're physics are doomed to failure - however I do know of people who claim they work. I guess the difference is between the temperature we feel and the actual temperature.
Please correct me if I'm wrong. High humidity when its hot means that my sweat doesn't evaporate as quickly/easily so I feel hot. Surely then reducing the humidity is the way to go as this will allow my sweat to evaporate more easily.
So - would a dehumidifier help to reduce how hot I feel? I've never seen them advertised as being able to do this - whereas things which humidify (evaporative coolers) seem to claim they do.
Basically I'm confused about it and just want a (reasonably) cheap option (also preferable movable between living room + bedroom) to cool us down. Fans may be the best option (price wise) I know - but I'm trying to think of other options too.
Incidentally, what's the sort of price I should expect for a reasonable split air-conditioner? I'd love to be able to permanently install one for the living room - however it then seems a waste as I can't use it in the bedroom (unless it managed to cool the whole house down!).
Thanks
D
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Don't bother with a./c units in the UK climate. Just enjoy the nice weather as it comes along, so infrequently.
To cool a room, not freeze it, have some sort of forced ventilation bring in cooler air from the north side. Heavily insulate the loft. use radiant barrier in the loft to as this reflects heat back out from the tiles.
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<snip>

I'm sure that it'll come as a surprise to you, but just as there some (many) people who regard Milton Keynes as one of the inner circles of Dante's hell, there are those for whom 30C/90F temperatures are anything but "nice".

... and the relative costs of these options are ...?
Julian
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wrote:

There is something in what you say. I regard south London a hell. All those sink estates.

I lot cheaper than an a/c that will be used a few days a year, and buttons to run.
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Your last suggestion sounds quite a good idea actually. Our roof is unlined and very dusty (I think due to it being unlined). I've wondered about whether we could put something on the underside of the roof to stop all the dust etc coming from the tiles (which is where it seems to be coming from). If we put something reflective (on both sides?) onto the underside of the roof this may both stop the heat coming into the loft, and also stop some of the dust (so we may be able to use it for storage!).
Now - what would you suggest to put on the underside of the roof? I wouldn't want to put anything which may cause problems (damp etc) and I'd not want to do anything which a surveyor in the future may take issue with (though they'll probably take issue with anything!)
Any suggestions?
Thanks
D
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David Hearn wrote:

Until you actually stop and think about it.

Dust yes, but heat? No, the only way to reduce heat input from the tiles is to put thermal insulation under the tiles.
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But it needs a thinker to think about it. And you fail in this respect.
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The loft does have insulation (as thick as the joists). There's just no felt under the tiles (ie. I can physically touch the tiles).

I forgot to say that we've got one of these. At least, sort of. I fitted it fine - but I've got to sort out a wobble with it - it has 3 speeds - top speed wobbles far too much and makes a pulsing noise. The 2 slower speeds are okay (no visible wobble, but still a quiet pulsing noise) - and we use it as such. I need to take it down and put something under the mount (currently just metal to lath/plaster into joist) and possibly use longer screws. Once that is done, I'll then consider swapping the blades around (though they claimed they were all matched in the factory).
What we've been doing is using the ceiling fan (which we don't seem to notice does anything except make a pulsing noise which annoys us slightly) and also a pedestal fan. Makes things more bearable - though its still too hot....
Maybe shedding some pounds off my weight may make things a little better... ;) I've been meaning to do that too!
Thanks
D
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Heavy dust on radiant barrier reduces its effectiveness. Plug the holes first.
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IMM wrote:

Exactly how much heat radiation are you expecting to get off the under side of a hot tile?
The only way a radiation reflective layer is going to have a major effect is if you put it on the outside of your tiles..... go wrap your house in tin foil!
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he has got a point (!) Tiles will absorb radient energy from the sun and re-radiate some of that down into the attic space. Lining the inside of the roof with tinfoil would reflect some of this back, and reduce convection currents.
Whether it would make a noticable difference to the rest of the house is another matter!
Since I am sick of renovating my kitchen I might try an experiment this weekend
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Compared to the amount of heat that is transferred into the house by direct thermal conduction from the (hot) tiles to the air and hence induced thermal convection, the amount introduced by radiant energy is small at these temperatures.
You'll be much better off insulating between the rafters. That will stop the loft space heating up to such a high temperature, and hence reduce direct thermal conduction to the house below.
cheers Richard
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It is a combination of bothg radiant barrier and heavy insulation on the loft floor. 300mm min.
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Actually come to think of it, fill the rooms as well. Then you can maximise the heat properties.
There won't be any room for the people of course, but that is a mere bagatelle in the quest for the insulation Holy Grail .andy
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In the context of the insulation afforded by the other surfaces in a typical property, the value tails off after about 100mm.
Look at the sums for a typically constructed property from the last 50 years and going beyond that is making small changes to a fairly small part of the total heat loss or gain.

You don't normally let that get in the way of principle.

.andy
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have, not experimental stuff, which while it may be interesting, is not relevant to practical situations.
If you do the heat loss (or gain) calculations for a brick and block property with tiled roof, having ridiculous amounts of space wasting insulation in the roof space is making no more than a tiny difference when set in the context of what is gained or lost through the walls and windows.
You are the one who is advocating saving space sufficient for a couple of pairs of shoes over a hot water cylinder, yet filling a loft to a point where useful storage space is lost is OK. A little inconsistent, isn't it?
.andy
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wrote:

No you don't read at all. Once again, so much faith, with so little evidence or figures.

Figures and evidence please. Not rambling thoughts.
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I don't deal in faith or dogma.

I already did this once for you and not very long ago. Would you like me to dig out the figures that demonstrate once again that you are talking nonsense?

.andy
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wrote:

You are dealing with a lot of it now.

You claim anything over 100mm of loft insulation is not worth it. Please convince me. Don't make it up.
Strange that current building rags are over 100mm and in 2007/8 they will be well over. Maybe you know something the BRE, the Germans, Dutch, Scandinavians and North Americans don't know.
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It's pretty simple.
Consider a detached property with an overall footprint of 8m x 8m and a height of 5m to the eaves. Floor is concrete throughout and there is a pitched, felted roof. Walls are brick and block with 50mm cavity insulation. All rooms are at the same temperature of 21 degrees, and the outside is -3 degrees. There are a total of 10 rooms with an average window size of 1.5 sqm in each, and patio doors 3m x 2m
Using the required U values from the Approved Documents to the Building Regulations:
Floor         U = 0.25 Walls        U = 0.35 Windows    U = 2.0 Roof        U = 0.16
Floor area = 64m^2 dT = 24 Heat loss = 64 x 24 x 0.25 = 384W
Window area = 21m^2 dT$ Heat loss = 21 x 24 x 2 = 1008W
Wall Area = 8m x 5m x 4 = 160m^2 less 21m^2 windows net wall area = 139m^2 dt = 24 Heat loss = 139 x 24 x 0.35 = 1168W
Roof area = 64m^2 dt = 24 Heat loss = 64 x 24 x 0.16 = 246W
This comes to a total of just over 2800W In addition, in order to heat the average number of air changes of 1.5 per hour, additional heat of 3975W is required making a total of 6775W.
If the U value of the roof were increased to 0.36, which is the approx value if 100mm of insulation were used, the heat loss through the roof increases to 554W, the difference being 308W.
In other words, the saving is 308/6775 = 4.5%
In comparison to the walls and windows it's negligible.
If you were to take a slightly older property having twice the U values for each surface, the improvement gained by going for more than 100mm of insulation drops to between 2 and 3 %.

That depends on the type of insulation, of course. Frankly it's demonstrably window dressing to play the Kyoto game.

You've seen the Statutory Instrument?

Not really, but the figures speak for themselves.
It's window dressing.
.andy
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