Heat loss calculations for floors

[JohnD]

I was showing someone the SEDBUK boiler size (heat loss) calculator. I had the idea that it allows you to specify floor construction, as they are interested in insulating between the joists of a suspended timber floor and adding UFH.

the SEDBUK doesn't appear to have this parameter.

Is there one that does, or some rule of thumb figures for uninsulated ventilated suspended floors; and insulated ones?

TIA

 

[D_Hailsham]

The Sedbuk Calculator is based on an older version of that produced by the Energy Saving Trust. You can download the latest version from Here. Unfortunately it's only paper-based.

However Baxi have produced an Online calculator which seems to be based on this document.

 

[JohnD]

thanks!

it's very sketchy on floor insulation, but I ran test figures for my own house, and it came out about right.

 

[D_Hailsham]

it's very sketchy on floor insulation

It may appear that way, but U values for floors are calculated in a completely different way from walls etc. The size and shape of the floor has a considerable effect, so it it possible to have an uninsulated floor with a very low U-value. You will see this in table 6 of the EST document - as the ratio of floor area to perimeter increases the U-value decreases. Though I'm not sure how you can have a building with a ratio of 20:1.

 

[Madrab]

For insulated floors you will also have varied U values depending on the type of insulation you use. Different insulation have varied thermal properties. Suppliers of insulation would supply these and they would be added to the equation. Oh the joy of doing Part L
Building regs Part L1B gives you the info for existing builds - http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_L1B_2011.pdf - Section 5