BRE U Value Import

[Roger Evans]

I might well be a bit slower here than some of you but a useful tip ..

I was playing with the UK BRE U Value Calculator & trying to figure how to import the info onto drawings then found that looking at the calc in preview mode I was able to copy the calc & then import as text into Revit ... works a treat

Retaining Walls ... Anyone know how to calculate U value for a retaining wall ?

[Martin P]

That is handy to know Roger, we use the BRE U value Calculator all the time.

The basement Calc is a bit of a waste of time, it doesnt allow for only some of the walls to be retaining :( and appears to be only a floor?? will have to do this soon myself!! probably I would be tempted to ignore the earth beyond the wall, then you would know that your U Value you calculate would end up giving a better than required as the the earth would only improve the U Value. If you add a very big number as the thickness of the earth you will end up being told dont need any insulation, which you obviously would do.

Playing around with floors though the earth does make a big difference. I did a floor with 1 layer a thickness of 1mm and a lambda value of 5000. (ie just the the earth being calculated)

for floors I found

clay alone gives a U value of 0.65
sand gravel 0.82
rock 1.25

I used the lambda Values from floors and applied to a 1 layer wall (clay 1.5, sand 2.0 rock 3.5) I adjusted the thickness till the uvalue matched what I found above and I got -

for clay (in a floor at least) it appears you could use a 750mm layer with lambda of 1.5 to represent the earth.....

for sand a 2100mm layer with lambda of 2

Suppose it depends if you need more or less insulation, I will probably go for ignoring the earth and just getting a well insulated wall when I have to do it...