Radiator output help

[jazzbhatia]

I work at the Council as a Housing Enforcement Officer and part time gas engineer (when I get the time)

I am looking into radiator output and its relation to buildings characteristics. In doing so I have used various online calculators and have always come out with a different output. The Chartered Institute of Environmental Health (CIEH) has published an excess cold guidance which I feel is not consistent. Page 35 (appendix 5).

http://www.cieh.org/WorkArea/showcontent.aspx?id=38302

I come across various properties which clearly have physically undersized radiators and suffer extensive condensation/mould. I am aware that we need to ensure that the tenants are using the heating, ventilating etc etc however we must also ensure that they have the means to do so hence my questions.

What is the best way to calculate a rooms requirement
How do you spec a radiator output?
Is over sizing better?
Is there a standard or guidance on this calculation?

 

[Weedrip]

Many online calculators while generally ok must by their nature make std assumptions as to the building / structure. Any real life deviation from the std model will result in an inaccuracy of the end result.

What is the best way to calculate a rooms requirement
Define the building elements and calculate the heat-loss to each element enclosing / affecting the space to be heated.

How do you spec a radiator output? Use the manufacturers table of outputs, but do allow for the mean temp of the system and adjust according to the correction factors as published for the chosen product.

Is over sizing better?
Having calculated the output required for each space or zone some element of over sizing [or allowance] should be made to accommodate, exposure of the structure, extremes of temp, fuel / appliance type.

Is there a standard or guidance on this calculation?
A Traditional method would be to:
Define the U value = [ W/m2 per degc ] calculate the area or volume x by the relevant U value x temp difference + any allowance for the exposure and extremes.
A common oversight is not allowing for increased air changes where a room has an open chimney.

To get a feel for the type of long hand calculation the following is a link, [just the first I could find, I am sure there are many others, google is your friend in this to find a method]
link>>> http://www.tombling.com/heaters/heatloss.htm

hope that is of use.