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
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:
dan.
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