Radiator Calculator

[Martin Carroll]

Just been trying a few calculators to work out radiator sizes for the bedrooms in the renovation.

The couple I have tried have given me completely different results (6450 BTU or 2606 BTU !!).

Anyone got a link to a calculator that gives the correct values?

Cheers

[dwtowner]

When I was doing this recently I too found a huge variation in the calculated sizes. The trouble is that they seem to make different assumptions, which relate differently to the factors that you supply. For example, if you have a very large external wall area, then two calculators that make different assumptions about the external wall U- value will give dramatically different radiator requirements.

Eventually I went back to first principles, and calculated the requirements from the u-values of the indivual elements, which is actually very easy to do. A good overview of the process is given here:

course, you could always take the largest value radiator, and fit a thermostatic valve to it, which is what the guy in my local plumber ship suggested!

dan.