In a home with infloor radiant heat on the first floor, is it worth the extra cost to also install radiant heating in the second floor? Or would baseboard heat be sufficient? The heat source is a geothermal heat-exchange system, so the water comes into the house at about 120 degrees.
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The answer's gonna depend on things like heat loss, construction methods, floor plan, glazing, etc. For a lot of the time, heating our first floor suffices, especially be/c the upstairs is only bedrooms and we want them a coupla degrees lower anyway. But the colder it gets outside the less that suffices, and there are probably a few weeks worth of cold days that we really need the heat upstairs. And then the decision to RFH or not will depend on your perception of comfort. I really like the warm floors, especially the tile in the bathrooms, but also stepping out of bed, paddling into the closet, etc. For me, I'd still rather heat the floors than have heat sources along the walls.
If you are talking about HW baseboard heat, I don't believe that 120 degrees at the manifold will be high enough. If you already have the geo unit and the pumps, I am wondering why you would not put radiant heat on the second floor???
Yeah...you've already got most of the expense out of the way, that is if you can still get at either the top or bottom of the subfloor. Also, can your geothermal unit handle the extra load?
Generally, baseboard convectors are not speced for 120 degree water, but with the advent of outdoor reset controls, they realistically may be running at low temps most of the time.
Heatloss is the big variable. If the house is very tight, an upstairs zone may rarely kick in anyways. Upstairs floors are usually not cold ot the touch. You may indeed be able to get enough out of baseboards at 120degrees for the coldest day of the year.
I think the cost/benefit ratio for RFH on upper levels is not as good, so it may be worth weighing your options. RFH in a tiled bathroom is almost always worthwhile, however.
With some irony, having RFH on the lower level is likely to make the upper level somewhat colder than it would be otherwise. Less hot air accumulates at the ceiling level to conduct upwards, and less hot air rushes up the stairwells.
Thanks to everyone for the thoughtful replies. I was asking the question for a friend who is not Internet-equipped. I'll pass your answers on (and any others that come along). To answer two of your questions:
1. The downside of RFH on the 2nd floor for him is the added expense to an already pricey system.
2. I think his geothermal system was designed to handle the extra load of 2nd floor RFH or whatever.
Thanks again.
--Asa Christiana, managing editor, Fine Woodworking