I'm trying to work out the losses in my new (1970) bungalow. ATM I
have a spreadsheet that tells me that I need 16 kW with an external
-1C. Strangely, the boiler, a Worcester HeatSlave Oil combi, is a
15-19kW model - perhaps the engineer that spec-ed it back in 1991 could
add up too :-)

Now I can find U-values for most things, but how do I work out the
effect of adding another 150mm to the existing 100mm loft insulation.

Also, my heating pipes run through the loft, and are lagged, but I
think I should allow a loss per meter run, any ideas how to do that?
The house is L-shapped and some of the runs are very long.

Thanks,

R.

Happy Christmas and a Prosperous New year to all.