Haet loss calculator

[Martin Evans]

Has anyone got a link/source of a decent (preferably free) heat loss calculator?

Myson used to have one but its no longer on their website.

[Andy Hall]

Send me an email and I'll send you the Myson one.

[Tony Bryer]

The Heating and Hot Water Information Council do one for £15 - I've not used it myself

[Lobster]

From my 'favourites' list (culled from this ng on a previous mention IIRC, but not used by me yet!):

[Tony Bryer]

later"

Suggests it hasn't been updated for a while (which may or may not be relevant to its usefulness)

[Andy Hall]

It's reasonable, but some of the U values are wrong and need to be updated from the building regulations figures. Although these might have been altered to help meet Kyoto commitments of course..... I would cross check again.

[John Stumbles]

You can do it on a spreadsheet (or paper and calculator, abacus or fingers[1])

[1] toes may also be required for some values

[Andy Hall]

Don't forget that the calculations for ground floors taking account of perimeter use a table of fiddled U values, so a spreadsheet would need some work unless there is a formula that can be used instead.

Tony, do you know?

[Tony Bryer]

In the current release of SuperHeat we have hard coded in the Appendix C tables and just interpolate. Previously we used the formula from BRE Information Paper 3/90:

U (uninsulated) = 0.05 + 1.65PA - 0.6PA^2

where PA = exposed perimeter/area

For a 5m x 10m floor four edges exposed PA = 30/50 = 0.6

Uninsulated U-value = 0.824 (current AD App.C gives 0.78)

To get the U-value of an insulated floor (insulation under/over whole of slab including perimeter) you take the reciprocal of this value to get the thermal resistance, then add the resistance of the insulation, then take the reciprocal again to get a new U-value.