Does anyone know a reliable formula for calculating the required kW for radiator panels based on room size, external wall size, window size etc?
I'm getting varying suggestions from suppliers so don't know what to trust. Some just say 1 kW per 10 sqm, some say 1.4 kW per 10 sqm, one gave a result of 5.4 kW for a 21 sqm room, and then there is a calculator that apparently takes into account windows, external walls, whether you have insulation (see http://www.choice.com.au/reviews-and-tests/household/heating-and-cooling/home-heating/heating-options-for-your-home-buying-guide/page/heating-calculator.aspx)
E.g, what kW rating would you suggest for this room?
6m x 3.6m with 2 external walls (approx 25% of the external walls are standard windows).
- External and internal walls are not insulated
- Old windows that are not double glazed
- Ceiling is 2.4m insulated throughout, hardwood floors on piers with air underneath.
- Maximum difference in temperature from outside in winter to desired temp inside would be 15 degrees C.
From the formulas I have at least 3 different results, 2.8kW, 3.25 kW and 5.4 kW, so not sure what I really need!