Loft Insulation

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You missed it again. It is not a mater of either or. It is cheap to pack the loft full of insulation and super easy to do so. So do it. The walls leaking heat is another matter, and of course should be tackled eventually. To do the walls is not easy and expensive. because the walls leak heat more than the loft does not mean you ignore the loft, or insulate it to the level of then walls. You have strange logic.

Very convincing. Based on pure logic.
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That's exactly what I'm saying. Insulate it to the level of the walls which is a U value of 0.25 to 0.35 for a place with cavity walls and insulation. That equates to 100-150mm of glass fibre, not 350mm-600mm.
On an older property, the U value of the walls can easily be 2.0.
There is very little point in reducing the U value for the roof below 0.25 in the context of that.
.andy
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On Thu, 22 Jan 2004 15:28:12 +0000, Andy Hall wrote:

I think I am seeing your point.

Yep, my house is 250 years old, so really thick walls, but certainly no cavity.

Is there a way to find out the current heat loss through a wall?
Thanks
Dean
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On Thu, 22 Jan 2004 17:24:50 +0000, Dean Richard Benson

This will have a U value better than that which is for a 220mm solid brick wall with plaster. A 335mm one is at about 1.6 W/m^2.K
For other materials it's necessary to know the construction of the wall. If there are several components to it then the effect can be summed mathematically using reciprocals but if there is air inside that can make a fair difference even before insulation is added. For example for a cavity wall of two 105mm brick layers with 25mm air gap, the U value drops from 2.0 to 1.5. As soon as insulation is put into the gap it falls to around 0.5

There is a reasonably rigorous way of doing it in the Approved Document to the Building Regulations for Part L1.
http://www.odpm.gov.uk/stellent/groups/odpm_buildreg/documents/page/odpm_breg_600288.pdf
although the examples work on how much insulation is needed to achieve a certain U value for typical constructions.
There are also various references to U values on the internet if you search with Google.
If the wall is very thick, then you will also have the issue of thermal mass - in other words the amount of heat required to raise the temperature of the masonry itself. This has an impact on how quickly the air warms from cold, since to begin with, until steady state is achieved, you are also having to warm the walls. This is a separate issue but can influence heating design and controls.

.andy
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Don't. It is totally wrong.
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On Thu, 22 Jan 2004 22:07:15 +0000, IMM wrote:

Funny thing is tho, I can see your point too, I just don't know who is right.
What I do know, is that while I have the opportunity, I will spend as much as I feel comfortable and/or can afford at the moment on sticking in loft insulation into the loft.
Although I realise there is also heat being lost through the walls and windows in each room, I dont have the time or finances to spend at this moment in increasing the insulation for that.
However when I replace the windows, and/or decide to add insulation into/to the walls, I will adopt the same route as I have done for the loft, ie, insulate as much as I can afford at the time.
My goal throughout this insulation in my house is to increase comfort, not so much to save cost. Therefore return on investment for the insulation isn't as important to me as having a comfortable house. This is within reason of course, I do have a limited budget :)
I hope the above explains my angle.
Thanks to both IMM and Andy Hall for their points too.
Dean
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I was going to suggest the Knauf U value calculator normally available as a trial version from http://www.knaufinsulation.co.uk/ but it is unavailable at the moment as it is apparently being updated.
It may be worthwhile checking the site in a week or so if you \re still interpreted.
cheers
David
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The point is that the house has to be viewed as upper and lower floors. the difference in the upper floors is marked in most houses.
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temperature variation, varies depending on whether you are upstairs or downstairs?

.andy
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Grow up! The rooms in the upper floors have a large area that is the ceiling with a cold loft over in winter and hot loft over in summer. Insulate the loft heavily and heat loss in these rooms reduces considerably, giving superior comfort conditions in winter and summer, moreso than the ground floors.
You didn't know that did you?
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Yes, and all the exterior walls and windows have an even larger area that is hot in the summer and cold in the winter.

Please provide the figures to demonstrate that assertion.
If you are saying that adding insulation where there was none before makes a significant difference to the overall effect in the house, I will accept it. I don't accept that insulating up to 300-400 mm rather than 100 or 150 makes a huge difference to the *total* for a house because the figures don't support that.
If you can demonstrate, for an existing property, (not an eco-special), with independently verifiable figures and quantitative references that doing what you propose makes a difference of more than a very few percent then there is something to discuss.
Otherwise you are just doing your normal arm waving with nothing substantial to back it up.

.andy
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wrote in message

They generally do not. Most it is about equal in area. My main bedroom has a very large ceiling area. More than the walls. And when you take into account much of the outside walls have build-in wardrobes across them, there is not much wall area at all compared to ceiling area. Most homes have built-in floor to ceiling wardrobes these days, with many of them against outside walls, which gives an extra level of insulation against the outside walls. Packing in loft insulation for the benefit of the upper rooms is a win, win, win situation, giving greater benefits to these rooms than others. It is worth alone just for these rooms.
As I have told you. Last August in a heat wave, the coolest roomin my house was the main bedroom. The insulatio above proteced it from the 55C in the loft above. A breeze runningthrough the uper windows, which are beter for breeze being higher up, and it was very comfortable.
Many selfbuilt homes have the living areas on the upper floors, which makes much more sense.

Depends on the house in question. 90% plus will benefit and many others will greatly benefit.

You are a thicko! The upper rooms greatly benefit, of which there is usually 3 or 4 bed and one or two baths. You make the silly mistake of looking at the whole house and treating it as one with all rooms being equal. Big mistake.
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Nonsense.
Detached House. 7m x 7m x 5m high Outside wall area 140 sq metres Ceiling area 49 sq metres
Semi detached house 7m x 5m frontage x 5m high outside wall area 85 sqm ceiling area 35 sqm
Bungalow 10m x 7m x 2.5m high outside wall area 85 sqm ceiling 70sqm
Terraced house 15m x 5m *5m high outside wall area 50sqm (assuming small front and back walls) ceiling area 75sqm.
This is the only case, and even then there is a question mark over the party walls which should probably be treated as a third to a half the heat loss of an outside wall.

By counting three walls as internal? That's a crock because for the house as a whole there will be 2,3 or 4 external walls overall.

This is just pulling things out of the air.

Maybe you should try mirrors on the ceiling as well......

Figures? Otherwise this is just armwaving again.

I've done heating calculations in fine detail for different properties, counting losses and gains through internal surfaces as well.
The temperature ranges for different rooms by recommendation range from 16 to 23 degrees and I suspect a lot of people run with less than that. If you plug in these factors for most properties, the heat flow internally is generally relatively small in comparison with flows through external surfaces.

.andy
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wrote in message

You have to look at individual upper rooms.

Not in that room it isn't.

It is NOT! It is looking at the house realistically, instead of one blob of a box.
> >As I have told you. Last August in a heat wave, the coolest roomin my house

If these wo rk then I will. Do you have a URL?

Figures? For what type of house? Do they all one bedroom wall top to toe built-in cupboards? Etc, etc.

The devil is in the detail. Your detail was not fine enough. It is worth having high levels of insulation in my house just to keep the bedrooms warm and cool. For those who have an upper room as an office the benefits are even greater. Keeping bedrooms cool is good in preventing cots deaths too. I'm sure the lower rooms didn't benefit too much.
Even in the depths of winter, once the bedrooms are up to temperature, the TRVs virtually stay off all day. I have the bedroom doors always closed, so no heat is rising from downstairs into them.
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OK. So present a worked example of a typical house of today, yours if you like, and show figures for why you believe this is significant in the context of this discussion.
Obviously this is important in terms of heat emitter sizing but that is not the discussion here

OK, so why don't you present some real figures and workings to demonstrate your point.

On that argument you would insulate different rooms to different degrees.
If there were a real issue here, rooms would be insulated from one another in addition to anything related to external surfaces. Unless one wants to deliberately maintain a temperature of one room at a significantly different temperature from the others, insulation between them is not used, simply because the overall differences are 6-8 degrees.

Just provide a typical example with worked figures to demonstrate your point if you believe there is one.

So please provide the detailed data and worked examples to justify these assertions. Yes I know that cooler bedrooms impact SIDS so you don't need to search Google for those numbers. Stick to the point of providing the detailed data on the extent to which insulation at your recommended 350-600mm makes the large difference that you claim relative to 100-150mm, stated in the context of the house in total.

.andy
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wrote:

NO need, common sense prevails.

Could be. You could do all the bedrooms to 400mm and 200mm the rest.

Most walls have some sort of built-in insulation.

Just use some common sense. Bedrooms have a large loft ceiling area with a very cold or hot loft above. Insulating these to high degrees pays dividends in the particular rooms below.

before> >> >> makes a significant difference to the overall effect in thehouse, I

Just use some common sense, instead of just looking at a Myson heatless programme.

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Not with you it doesn't. If you can't produce figures, that's OK but makes further discussion rather pointless.

Sigh......
If you do heat transfer calculations between internal rooms, the numbers are usually fairly small. Sometimes, heat gain from a lower floor room to an upper floor room can result in reducing radiator size a little, but that's about all.

More of the same waffle.

I look at a variety of sources, all of which provide hard data.

.andy
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wrote:

It does because you rely 100% on a computer program.

Can't figure this out eh!

You still don't get it.

You didn't look hard enough.
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No porkie telling now!
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The word you are thinking of is slightly. As has been repeatedly pointed out, we are currently insulating to levels where providing any more has a minimal effect.
On the typical 108m2 2-storey house file we supply with our SuperHeat program the structural heat loss with a roof UV of 0.18 is 111.92W/K which would fall to 105.15 if you could get the U-value down to 0.05. But at this point with a condensing boiler the energy split is roughly 33% fabric, 17% ventilation, 33% DHW and 17% system losses, and the cash saving shown on the SAP worksheet is 5.78p.a. Most people would rather have a usable loft.
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