Replacement Radiator BTU

[Burgo99]

Want to replace an old gunked up radiator in a bedroom that diesnt really heat up.
Current one is single panel 600 high by 1300 wide.
Bedroom is 3.1m wide
4.6m long
2.3m high
Window area 3.2m2
Double glazed
Brick cavity wall insulated
Over 100mm insulation in pitched roof
2 outside walls

Difference is 1/3 of room is over garage which is unheated.

Any ideas what BTU I should be looking for.
Wanting to get a column radiator to replace.

 

[Burgo99]

Want to replace an old gunked up radiator in a bedroom that doesn't really heat up.
Current one is single panel 600 high by 1300 wide.
Bedroom is 3.1m wide
4.6m long
2.3m high
Window area 3.2m2
Double glazed
Brick cavity wall insulated
Over 100mm insulation in pitched roof
2 outside walls

Difference is 1/3 of room is over garage which is unheated.

Any ideas what BTU I should be looking for.
Wanting to get a column radiator to replace.

 

[wwwebber]

Plenty of BTU calculators online, My only suggestion would be to over spec it - you can always turn it down !

 

[Burgo99]

It's just I've used a few calcs and gone from 3000 to 5300 btu
I have no idea if the old rad was man enough for the room as it doesn't work too well. Only moved in 8 months ago.

 

[Yorkshirebloke]

Try the Myson heat loss manager.
Then choose a rad design you like, find the BTU or KW of the radiator that matches the heat loss calcs and then choose the rad that's slightly bigger than what you actually need.

 

[JohnD]

I have a room of similar size, it used to have a single panel radiator and now has a double that is about 1800W nominal output, which is fine.

With a TRV it turns itself down once the room is warm

I've packed the floor of the room over my garage with mineral wool between the joists, it blocks draughts and reduces noise a bit, there's not much conduction and no convection heat loss through a floor.

If your floor is draughty, stuff it, especially round the edges of the room, or inject pink fire foam into the gaps, which will mostly be under the skirting.

A long low radiator makes the room more comfortable than a narrow tall one.

Bear in mind that with a modern condensing boiler, actual heat output is around 70% of nominal as quoted in the advert