Loft Insulation

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insulation
Of course I'm looking at the whole house. I pay the whole gas bill, which covers the heating for the whole house. If I only paid for my study, and my wife paid for the rest, then I'd turn the radiator off in that room and buy a few jumpers.

That's right - the extra 300mm required to take it up to the 400mm you requested. Well spotted.
You have to

I did, actually, because the costs I have been quoted for the Kingspan alone are less than I mentioned, but I allowed extra for battening etc.
Loft

As I have shown, the loft insulation is the same cost and has a much smaller benefit, so it is lower priority.
Also do downstairs too with

Do you think I am made of money? If my budget is (lets say) 400, it's either/or, not both. Insulating the downstairs wins hands down because it has a much bigger effect for the same outlay.
Regards
Neil
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On Fri, 23 Jan 2004 12:47:50 -0000, "Neil Jones"

Exactly. See my other post. Slightly different prices, but the principle is the same.

.andy
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On Fri, 23 Jan 2004 12:05:18 -0000, "Neil Jones"

Supawrap from BuilderCenter is 12.66 exc. for 4sqm and 150mm thick.
So for 70sqm coverage you would need 35 rolls to achieve a thickness of 300mm at a total cost of 520. This appears to be the cheapest they have on a volume basis. You could probably get 20% discount, so say 400.
On your assumed U value of 0.5, which is worse than it probably is, you are saving 588W worst case.
If the temperatures were worst case all year all day then at 1.4p a unit for gas you would save 72 per annum.
If you work on the 10 degree average which is closer to reality, then the loss is going to be 8/21 x the figure - i.e. 220W and 27 per annum.
In reality, the insulation you have is probably better than 0.5 and the saving perhaps 20 per year.
A 20 year payback or 10 years if energy costs double today....
Doesn't seem interesting to me.
I'd think about using even a thin Celotex layer on a few outside walls during redecoration first, if that's practicable. This is about 5/sqm for 50mm, 25mm is about 3.50.
.andy
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Exactly, although I'm looking at Kingspan rather than Celotex.
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wrote in message >

Do both. Loft and walls.
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wrote in message >

thick.
thickness
discount,
is,
a
then
and
walls
Do you live in the real world? Money is finite, and so we prioritise.
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wrote in message

Because you haven't looked at it properly.
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OK so present the hard data with numbers to justify that assertion. A complete example as I did and as Neil did separately.

.andy
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Apply some common sense and don't keep relying on a Myson program.
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You don't need a Myson program or any other to determine heat transfer through a surface. A pocket calculator is perfectly adequate and the methods of calculation well charted.

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But you rely on Myson.
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I don't rely on anything. Good engineering practice is to cross check information and method....

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So you make it up then?
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The U value for 100mm of mineral fibre in a pitched roof construction is 0.36 according to BS 5449.
So in fact Neil's heat loss via this route is less than suggested and more like
70 x 0.36 x 21 = 529W.
This is about 4% of his total 12.3kW
Increasing the insulation to your suggested level might achieve a U value of 0.15 taking the heatloss down to 220W.
This represents a difference of 2.4%
Not very interesting in the context of 20% going out through the solid walls.

The only effect that can happen there is to assume that the hallway downstairs is at downstairs temperature and that the landing above will achieve the same temperature via convection.
In most houses the upstairs landing might be 15-20% of the total upstairs area, so in essence the landing becomes 3 degrees warmer than the bedrooms. the impact is demonstrably marginal. Another corner case.

They look remarkably similar, even accounting for convection from downstairs.

If you think that that is a win, win then you are missing out on much bigger prizes.
Somebody once related the following tale to me, which seems apropos.
There were too bulls standing on the top of a hill and below them a field of cows.
One was always enthusiastic about chasing the latest idea, so he said "Cor. Look at that lot. Let's run down and f*ck one of them"
The other one said
"Let's walk down and f*ck all of them"

.andy
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In fact I deliberately increased the U-value of the loft because I don't know exactly how much insulation there is throughout the whole thing - part of it is inaccessible at the moment - and some of it appears to be somewhat low quality.
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You really haven't got it have you?
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On Fri, 23 Jan 2004 11:00:34 -0000, "Neil Jones"

These are quite typical numbers, Neil.
I guess that this is an older house with a new extension?
It's interesting to note that the losses are close to being the same upstairs and downstairs.
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Yes. The old part is 500 year old, or so. The extension was bulit in 1995.

Quite.
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Just to add my 2p. I insulated my loft to 150mm. I had lots of insulation over so doubled up over the main bedroom where I sleep. This bedroom is warmer in winter, and thankfully last summer a lot cooler. I could always sleep while neighbours complained they were too hot to sleep in similar houses to mine. When I have time I will do the whole loft to at least 300mm. If I can get a decent deal maybe thicker. To me it will be worth it. I don't know about economics as I haven't kept a watch on the gas bills. To me that is not the real issue during a hot summer.

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On 23 Jan 2004 07:12:33 -0800, snipped-for-privacy@my-deja.com (timegoesby) wrote:

As compared with having nothing? It would be. That is certainly worth doing but was not the point.

With how much insulation?

That's fine if you want to do it, but there is nothing to support that just doubling the insulation like this is going to make any significant difference to what you have now.

.andy
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