Can I rely on Kermi Radiator calculator software?

[Malcolmkeith]

I calculated my radiator sizes (BTUs) based on the simple formula of room cubic capacity in feet x 5 for lounges and times 4 for bedrooms -adding 10% for windows etc, etc. I was quite happy until I read about the Kermi radiator calculator in this forum.
It is a much more sophisticated calculator but I am worried that the figures it gives me are substantially lower than the simple calculation above. Many of the rooms are calculated to be 50% lower requirement than the simple calculation.
I don't want to find I have used radiators that are too small and I don't want to buy a boiler that is too small either.
Can I trust these Kermi values?

 

[ChrisR]

Don't know it. But the method you outline is inadequate, which is why it's so generous. You have to take in to account :

The sizes/materials of the floor, ceiling, walls internal and external, windows, window frames
Air changes
Aspect - northern, etc
Whether tha rads are under the windows or not, and whether they'll be covered by curtains
How quickly you want it to heat up from cold
Whether it'll be on 24/7
Background ventilation
Pipe losses
Whether you shut the internal door or not
Extra factors -eg Agas, airing cupboards
Oh and the outside and inside temperatures you want to allow for.

Others will add other factors.

Or use 50Watts per cubic metre - that'll probably do

 

[Paul Barker]

I would have thought times 5 and times 4 results in by far oversized rads.

 

[nstreet]

I hope it can be relied upon, i used it to calculate the values for my rads. I did add 10% though just in case

 

[Nige F]

Was that @ Delta T 50 or 60