Stone wall u-value

derickmc

I was speaking to another assessor recently and he was saying that he assumes the u-values provided in DEAP Appendix S is for a standatd 300mm stone wall. If the wall is significently thicker than this he works out the conductivity from the Appendix S u-value and a thickness of 300mm and recalculates the new u-value based on the conductivity and the actual wall thickness.

Anyone have the official line on this? Is it recommended practice?

d'Oracle

derickmc wrote: »

I was speaking to another assessor recently and he was saying that he assumes the u-values provided in DEAP Appendix S is for a standatd 300mm stone wall. If the wall is significently thicker than this he works out the conductivity from the Appendix S u-value and a thickness of 300mm and recalculates the new u-value based on the conductivity and the actual wall thickness.

Anyone have the official line on this? Is it recommended practice?

Appendix S does not give values for a stone wall based on the width.
Stone wall is issued as a worse case scenario, as such, it would be wrong to extract an conductivity value based on the stone wall.

DEAP manual Appendix S wrote:

If a wall type cannot be identified and does not fit into any of the categories in table S3, assume the wall type is stone.

dunie001

I have to agree with d'Oracle on this one...

Just use the u-value as it is given, and don't change it regardless of how thick or thin the stone wall may be.

it's not as if there's much difference in u-value of a stone wall that's 300mm thick and one thats 600mm thick anyway.