Radiator sizing

[bassanclan]

Any recommendations for an accurate/good radiator sizing website.

 

I've put the details for one room into three different websites and the results range from 8800 to 12000 BTU!

[PeterW]

This one and subtract 15% seems to be about right for me most times

 

https://www.traderadiators.com/acatalog/heating-calculator.html

[bassanclan]

Thank you.

It has given me a figure of 9592 BTU - 15% = 8153 BTU

I think if I go for 9000BTU I should be right in the middle of all these calculations, the 12000 BTU is an outlier.

[PeterW]

Just watch the sizing as they assume a wall of 0.3 on the uValue and not the much better standards you're probably building to. 

[bassanclan]

It's a refurb with a wall of 280mm - insulated cavity of 80mm, so probably worse than the assumptions!

[JohnW]

Just trying to resurrect this thread - I can't find an online radiator sizing calculator that accounts for triple glazed windows or really well insulated walls, floors & roof.

 

Does anyone know of a reliable one that does?

[PeterW]

None do - they are a long way behind the times. 

 

What you need to do is work out your total load, check the room volumes and then size based on this. @JSHarris spreadsheet is a good start for this. 

[JohnW]

Thanks @PeterW are you suggesting I use the spreadsheet to calculate the whole house heat loss and then if a rooms volume is 10% of the whole house volume then the heat loss for that room will be 10% of the total heat loss?

[PeterW]

It will be a reasonable start - you may need to flex it a little based on the external walls etc but if you oversize the rads you can turn them down 

[CC45]

I always try to see how the size of rad will look in the room.  I increased the size of some of ours so they looked right.  It is a very well insulated house so the rads were (and still are) on the small side anyway.  If you are in any doubt then bring the pipes up in the centre of the rad and then go left and right - that way you can fit a bigger rad if you want to at a later date.