Installing A Radiant Floor Heating System


We are building a new home and wish to use radiant floor heating system (not electric) throughout instead of forced air. We also want hardwood floors…is this possible or must we stick to ceramic/stone floors?


Neil and Andrea


Dear Neil and Andrea

You can have your hardwood floor, but you will have to give them some special care to keep them from moving too much seasonally. Choose the simple hydronic system that places the heating pipes between the joists under the floor, so if any leak occurs the wood floor will not be affected too much.

Install at least 1″ or thicker plywood to the joists, with urethane glue and 3″ nails every 6-8″. Install the hardwood first. If you live in a really dry or very damp climate consider applying at least one coat of oil modified polyurethane on the underside of all the boards, and allow a week for this to dry and boards to acclimatize. This combined with the top coat, slows the moisture migration into (during humid summers) and out of (during the dry heating season) of the wood. The best furniture is always well finished on the underside also, for this very reason.

Consider using a 3/4″ quarter sawn red oak, or white oak in no more than 2 1/4″ width. NAILED every 6 ” with the proper floor cleats (read my article about this available in the search box at the top of this web page; the Primatec 210).

Keep the hot water in the heating system to no more than 80F, be sure of this. Raise the heat slowly in the fall, and heat consistently all winter, even when you are away. Then in the spring let down the heat gradually. In summer the house should be air conditioned, or at least dehumidify the basement. Try to keep the indoor relative humidity to about 40-60% ALL year round. Get a real wet-dry bulb hygrometer to measure this, the little metal ones that come with a thermometer are not accurate. You can get a good one at Try sku# 848N635.

Sounds like too much trouble, you bet. And the ceramic tile will hold the heat better, because of its thermal mass. So my choice would hardwood with a conventional system, or ceramic with the hydronics.