Does Weyerhaeuser have a recommended detail for installing radiant floor tubing to the underside of the floor sheathing?
The typical detail for insulating radiant floor heating is to attach the tubing to the underside of the floor sheathing and use batt insulation below to reduce energy losses to the basement. Usually furring strips or 2x are nailed to the TJI webs to support the batting. This may be easy to install but may cause some problems. The insulation below the tubing isolates the top flange in a warm dry environment while the bottom flange is in unconditioned space. When wood is moist, it will expand. Since the expansion due to moisture occurs on the bottom flange (the flange exposed to unconditioned space), there could be additional deflection beyond anticipated.
This detail is our preferred radiant floor heat detail as it better isolates the tubing from the floor structure so no energy is wasted heating the wood and both flanges experience the same environment. In addition, the aluminum heat plates will conduct more heat up to the sheathing, a more efficient heat path.
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