U vlaue of an old wooden flat roof

[azwaz]

Hi

I hope someone can help me. I had a aprox. 2" wooden flat roof on a single story extension behind the kitchen. It started leaking and and I was also loosing a lot of heat as it had no insulation.

I changed it with Pelkington K glass pitched roof. I now want to re-move a supporting pilar in between the kitchen and this extension only to be told by the council I need a heat loss calculation sheet.

Questions is does anyone know what is the U-value of an old wooden flat roof so I can enter it into the calcultion sheet.

Thanks

 

[mointainwalker]

Not sure if I have correctly understood, but if the previous roof consisted of 2" of softwood then this would give it an R-value of 0.4 or a U-value of 2.5 if the council prefers that.

 

[azwaz]

Thanks for the reply mointainwalker

I suppose to duty is on me to prove the value as the roof is now gone.

The council state, if it had past the pervious building regulation then it must have had a good enough insulation but this is all hear say, as the extension was built before I move in which is well over 14 years ago.

I will use your 2.5 U value and see what they say. many thanks.

 

[azwaz]

Sorry to ask but as matter oinsterest how did you work out 2.5 u-value, is there a special calculation you made based on the 2" softwood?

 

[Alastairreid]

http://www.vesma.com/tutorial/uvalue01/uvalue01.htm

 

[legs-akimbo]

Using that calculator is not as simple as putting in 2" of timber there are other variables and it is also not particularly accurate.
If there was absolutely no insulation it would be more accurate at 2.3 u value with a degree of insulaion around 0.4...theese are default values dependant on year of construction and amount/type of insulation.
I calculate u values in my job so I know how to do them precisely.