Adding Heat to Room Without - Radiator or Ceiling?


Old 01-13-16, 03:09 PM
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Adding Heat to Room Without - Radiator or Ceiling?

1926 House. One room has no heat. It's a second floor room we use as an office. Several windows. Attic insulated to R30. Walls not insulated. We live in an area where the lowest winter temps are about 40F and are typically about 50F. The room is 7x14 feet.

We have a boiler than sends heat to the original cast iron radiators. Water temp is 180F. The house is largely original in appearance inside and we are trying to keep that period look.

We want to add heat to this room. It seems like there are three options:

1. Ceiling radiant. No demo involved. I already have a set of PEX tubes, 3/4 inch, that go from the boiler location to the attic, so this would be pretty easy. I even have a conduit that would allow control wires to reach the boiler for zoning. Takes up no room in a room with limited floorspace. Water temp might be too high for this. I would build an insulated box above the ceiling to minimize heat loss and to direct it downward.
2. New wall mount radiator. Could optimally size radiator and could place beneath windows. Takes up little room. Some demo of plaster involved. Non period look. Could be zoned as well.
3. Take radiator in basement, which matches the rest of the 1926 radiators. and place in room. Replace basement radiator with larger modern unit that is properly sized (existing cast iron way too small for that room, about the right size for the 7x14 room). Takes up floor space. Preserves period look. Could be zoned as well.

Pluses and minuses of each, and your recommendations or suggestions would be appreciated. If ceiling heat is a good option, we could also heat two unheated bathrooms at that level using the same circuit as well. I would probably do this myself, having successfully incorporated a radiator into a first floor bath remodel.
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Old 01-14-16, 10:44 AM
Join Date: Jan 2014
Location: USA near Boston, MA
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I would recommend option 3 for aesthetic and performance reasons. Adding or mixing radiant and/or copper fin-tube on a predominantly cast iron system can result in problems.

Radiant supply should be mixed with return to provide a lower water temperature than radiation uses. That usually precludes adding it to an existing zone.

Radiant ceiling heat in your location may be OK but not too effective. Usually ceiling radiant is embedded into the ceiling material (like plaster). Mounting it above even with the "insulated box" you propose probably won't provide the heating result you desire. (Unlike a floor application where you actually come into contact with the warm surface.)

If you go with option 3 you should replace the basement radiator with a cast iron unit (radiator or baseboard) unless you have a way to provide different water temps to different zones. Cast iron works well with lower water temperatures in the 130 to 150 degree range. Copper fin-tube needs 160 to 180 degree water to be effective. Radiant is best around 120 to 130.

You can use PEX fished through the walls to feed up to the radiator (or even down from the attic as long as you provide a means to purge air from the top of the piping.) That might eliminate some of the demo and repair.

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