Sizing radiators in water system

ambercontractors

Looking into a job homeowner is asking to have radiators installed in various areas of the house (not everywhere, only attic 2nd fl, and basement). This is a new construction home and will be getting better than average insulation. The radiators are going to be recessed into the wall cavity sticking out slightly and being covered with decorative wooden covers with holes in them. How do i properly size such a system each radiator has to be sized up but how to know how much?

Jamie Hall

Yu ned to know the actual heat loss of the space which will be served by the radiator -- that's step one. Step two is to decide what temperature water you want to use -- I would suggest, being new construction, that lower will be better -- and I hope the boiler will be, if gas or LP, the mod/con type to go with that (otherwise you want the return temp above 140). Then step 3 will be to select a radiator with the output you need at that temperature-- but if they are recessed you may need to derate that by 30% or so (others may have other figures for that --probably better ones!) depending on the exact geometry and air flow in the enclosure.

EBEBRATT-Ed

@ambercontractors
with the recessed enclosure.
the mfg of the rads should be able to give you the ratings. But the first thing is the water temp your running as @Jamie Hall mentioned

Hot_water_fan

Jamie is exactly right. The wooden covers will be screwy, but perhaps you can propose better looking radiators? It seems like you can propose a better looking radiator to start instead of average + cover. 

mattmia2

Fancy radiators are expensive but they get less expensive when they mean you can make the radiator smaller and don't need to make a cover.

If you end up guessing on the oversizing for the cover, design your near boiler piping/boiler so you can further reduce the swt to reduce the output if you need to.

what about building custom enclosures for convectors?

ambercontractors

Job is done. The family moved in few weeks ago, to go back to everyone's suggestions- exposed rads were not an option here there were designers/decorators involved. This was a high end remodel, we went with wooden covers with a large notch in the bottom for better air flow as well as multiple vertical notches. And after going to manufacturers literature we upsized the rads by about 30% depending on the area. i also reserved the option to up the temp if i see the it cant keep up, so far it hasn't been a very cold winter but we're just getting started.