Pumping insulation into cavity

fiestaman

I was talking to the xtratherm rep today and he was saying that 60mm of there wall insulation has a U value of 0.25 in a 100mm cavity. He said that the pumped 100mm cavity was only 0.27 and you needed a minimum of 110mm cavity pumped to get a 0.25 rate. In this case i think i will be going for 60mm boards in the wall.

muffler

fiestaman wrote: »

I was talking to the xtratherm rep today and he was saying that 60mm of there wall insulation has a U value of 0.25 in a 100mm cavity. He said that the pumped 100mm cavity was only 0.27 and you needed a minimum of 110mm cavity pumped to get a 0.25 rate. In this case i think i will be going for 60mm boards in the wall.

You surely didn't expect him to tell you anything other than that?

sydthebeat

fiestaman wrote: »

I was talking to the xtratherm rep today and he was saying that 60mm of there wall insulation has a U value of 0.25 in a 100mm cavity. He said that the pumped 100mm cavity was only 0.27 and you needed a minimum of 110mm cavity pumped to get a 0.25 rate. In this case i think i will be going for 60mm boards in the wall.

its easy to manipulate the figures....

think about practicalities....

Viking House

fiestaman wrote: »

I was talking to the xtratherm rep today and he was saying that 60mm of there wall insulation has a U value of 0.25 in a 100mm cavity. He said that the pumped 100mm cavity was only 0.27 and you needed a minimum of 110mm cavity pumped to get a 0.25 rate. In this case i think i will be going for 60mm boards in the wall.

When the Xtratherm rep calculated the U-value did he allow for a 160% loss in U-value due to Thermal Looping when you have the unavoidable 3mm gap between the insulation and the internal wall because of discrepancies in block widths?
Did he allow for a further 160% loss in U-value over 2-3 years due to Pentane gas migration from PUR insulation?
If you are using older details around the windows, at the top of the wall and where the inner block sits on the cold foundations then I would guess the actual U-value of the wall is much closer to 1.25 than 0.25.

The details we build with are completly cold bridge free, it may be worth your while looking at them.

fiestaman

Viking House wrote: »

When the Xtratherm rep calculated the U-value did he allow for a 160% loss in U-value due to Thermal Looping when you have the unavoidable 3mm gap between the insulation and the internal wall because of discrepancies in block widths?
Did he allow for a further 160% loss in U-value over 2-3 years due to Pentane gas migration from PUR insulation?
If you are using older details around the windows, at the top of the wall and where the inner block sits on the cold foundations then I would guess the actual U-value of the wall is much closer to 1.25 than 0.25.

The details we build with are completly cold bridge free, it may be worth your while looking at them.

Thanks. What kind of value then would you be talking for the 100mm pumped. i know and see the point of cold bridging and i dont think theres any way of preventing it completly.

Viking House

Have you the walls built yet? Can you go with a 150mm-200mm cavity?
It is possible to avoid all the cold bridges completly. You should be pushing towards a 0.15 U-value wall without Cold Bridges to get close to the 2010 building regs that will be out soon.
You can use Polystyrene or Foamglass to stop the wall/floor cold bridge, you can shove your windows out into the cavity and use no L blocks and you shouldn't use a cavity closer block. The window cill should sit on the outer wall.