As we know, size does matter and thickness is everything..............BUT just how good is the product? what I mean by that is; does 1" stop 10% of heat passing through?, 2" stops 20%? 6" stops 95%? ( I realise the answer would be theoretical but it would be nice to have some kind of idea)
The actual effectiveness of celotex type products?
- Thread starter DIYedboy
- Start date
Sponsored Links
Do you mean in a completely new built three bedroom detached house in London? Or what? And how would you insert 6" into a cavity. You need to expand your question...
additional thickness is incremental.
e.g. suppose your roof loses 1 kW
suppose 50mm insulation halves it to 500w
the next 50mm will also halve what's left; from 500w to 250w
the third 50mm will also halve what's left, from 250w to 125w
soon the extra cost of more thickness brings such a tiny benefit that it is not a paying proposition.
Figures are made up, but not totally unrealistic
e.g. suppose your roof loses 1 kW
suppose 50mm insulation halves it to 500w
the next 50mm will also halve what's left; from 500w to 250w
the third 50mm will also halve what's left, from 250w to 125w
soon the extra cost of more thickness brings such a tiny benefit that it is not a paying proposition.
Figures are made up, but not totally unrealistic
Sponsored Links
I'm not sure that the lobbies you have in mind would necessarily agree that the manufacturing impact and cost is worthwhile, if there is not a realistic net saving on energy used, carbon saved, money spent.
In the UK, the current recommended thickness of loft mineral wool is 250mm, for example.
I haven't seen lobbying to increase it to 500mm
Swedish insulation standards are higher than here, because, being colder, the savings are greater. Actual energy loss is similar.
See Table 11 and Table 12
http://www.eurima.org/uploads/Modules/Mediacentre/brochure_en.pdf
In the UK, the current recommended thickness of loft mineral wool is 250mm, for example.
I haven't seen lobbying to increase it to 500mm
Swedish insulation standards are higher than here, because, being colder, the savings are greater. Actual energy loss is similar.
See Table 11 and Table 12
http://www.eurima.org/uploads/Modules/Mediacentre/brochure_en.pdf
JohnD's on the correct line. He just made up the 1KW figure which doesn't matter for the purposes of his illustration. The law of diminishing returns still applies. You'll find that there aren't any real figures easily available. Insulation is hugely political and no one is particularly interested in facts. Minor fact: All Celotex is about 0.022 W/mK. If you perform the calculation for your floor ,walls, windows and ceiling you should be able to get a graph tailored to your situation.
DIYedBoy
You cannot say that Johns figures "are made up". They are accurate and work in a real sense in that a room may need a 1kW heater perminatley on to keep it at 21oC, and that insulation may then mean that only 500W of heating in a room is needed to keep it at say 21oC.
You can use the required heating in your house and the lamda value of materials to see what change is produced by use of insulation. Here are some landa values of materials, noting that it shows how much energy in Watts (W) it allows through a 1metre thickness (m) with a 1 Centegate (K) difference on each side of the thickness. If you want to model it You can then change the values by making the temp difference different from 1oC and the thickness different from 1m.
Material Approximate thermal conductivity (lambda-value) in W/(mK)
Natural stone ........................................ 3.500 W/(mK)
Concrete .............................................. 1.500 W/(mK)
Full brick ............................................... 0.760 W/(mK)
OSB (Oriented Standard Board).............. 0.130 W/(mK)
Wood (pine) .......................................... 0.140 W/(mK)
Clay blocks (e.g. Porotherm) ................. 0.160 W/(mK)
Aerated concrete (e.g. Ytong) ................ 0.130 W/(mK)
Mineral wool .......................................... 0.039 W/(mK)
EPS ....................................................... 0.036 W/(mK)
Here is a nice introduction to lamda, U and R values: http://www.greenspec.co.uk/building-design/u-value-introduction/
and it shows that I feel is easier to model with U-values where using there example:
•The U-value of a single sheet of glass as found in a traditional window pane is 6.0W/m2K – which means that for every degree of temperature difference between the outside and the inside, a square metre of the glazing would lose 6 watts. So for example, if the temperature difference on a typical cold day was 15 degrees, then the amount of heat loss would be 15x6 = 90 watts per square metre. That’s a lot of heat!
• By comparison, the U-value of a modern piece of triple-glazing can be as low as 0.7W/m2K – which is not very much heat at all.
sfk
You cannot say that Johns figures "are made up". They are accurate and work in a real sense in that a room may need a 1kW heater perminatley on to keep it at 21oC, and that insulation may then mean that only 500W of heating in a room is needed to keep it at say 21oC.
You can use the required heating in your house and the lamda value of materials to see what change is produced by use of insulation. Here are some landa values of materials, noting that it shows how much energy in Watts (W) it allows through a 1metre thickness (m) with a 1 Centegate (K) difference on each side of the thickness. If you want to model it You can then change the values by making the temp difference different from 1oC and the thickness different from 1m.
Material Approximate thermal conductivity (lambda-value) in W/(mK)
Natural stone ........................................ 3.500 W/(mK)
Concrete .............................................. 1.500 W/(mK)
Full brick ............................................... 0.760 W/(mK)
OSB (Oriented Standard Board).............. 0.130 W/(mK)
Wood (pine) .......................................... 0.140 W/(mK)
Clay blocks (e.g. Porotherm) ................. 0.160 W/(mK)
Aerated concrete (e.g. Ytong) ................ 0.130 W/(mK)
Mineral wool .......................................... 0.039 W/(mK)
EPS ....................................................... 0.036 W/(mK)
Here is a nice introduction to lamda, U and R values: http://www.greenspec.co.uk/building-design/u-value-introduction/
and it shows that I feel is easier to model with U-values where using there example:
•The U-value of a single sheet of glass as found in a traditional window pane is 6.0W/m2K – which means that for every degree of temperature difference between the outside and the inside, a square metre of the glazing would lose 6 watts. So for example, if the temperature difference on a typical cold day was 15 degrees, then the amount of heat loss would be 15x6 = 90 watts per square metre. That’s a lot of heat!
• By comparison, the U-value of a modern piece of triple-glazing can be as low as 0.7W/m2K – which is not very much heat at all.
sfk
Last edited:
Paul, ha ha ha - very true. Always my issue is that I model this in my head as a heater in either a brick box, or a glass box, or a brick/Celotex/brick box, or a combination of all.
And then in real life the drafts blow straight through the letter box. :>
SFK
And then in real life the drafts blow straight through the letter box. :>
SFK
Sap already does this.
But you can truly never model a building until it is built and is occupied by those who the model is only relevant for.
What's the test called where you heat a building up to a certain temperature and measure the time for it to drop called?
SFK...............of course I can say John's figures are made up cos that's what John said...........but thanks to everyone else's contributions I realise that John's diminishing factor isn't the made up bit.
If we talk just about the insulation's effect upon heat loss (therefore ignoring windows, draughts n dog flaps etc) 50mm of insulation reduces heat loss by 50%, 100mm reduces loss to 25% and 200mm reduces this to 12%.............. am I correct in that assumption?
If we talk just about the insulation's effect upon heat loss (therefore ignoring windows, draughts n dog flaps etc) 50mm of insulation reduces heat loss by 50%, 100mm reduces loss to 25% and 200mm reduces this to 12%.............. am I correct in that assumption?
If you go on the celotex website there is a calculator where you can input your hypothetical construction and get the u value. You could run a few scenarios in there to get the numbers your after.
- Joined
- 26 Aug 2016
- Messages
- 6,833
- Reaction score
- 1,010
- Country
Yes you are correct, John's figures were slightly misleading in the 3rd 50mm won't half it again, you'd have to double it again which would be 100mm extra.
- Joined
- 26 Aug 2016
- Messages
- 6,833
- Reaction score
- 1,010
- Country
But the main thing is find what's losing the most heat in your room and work out how much you can save and the cost.
So don't triple glaze if you have solid walls as the walls are losing more heat and are a larger area. Better to insulate the walls externally.
But if you need to replace the windows anyway, if you need to redo the render on your house, that would change the equation one way or another.
So don't triple glaze if you have solid walls as the walls are losing more heat and are a larger area. Better to insulate the walls externally.
But if you need to replace the windows anyway, if you need to redo the render on your house, that would change the equation one way or another.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
