Radiant Under Subfloor
Installing a radiant heat system in an existing building can be a challenge, but is feasible. Usually, a combination of forced air and radiant systems is the best for these projects, because of the building constraints. A detailed survey of the structure is needed to determine which areas are able to have radiant installed, and which would need to be heated by forced air. The most common method of installing radiant in an existing structure is to attach the tubing to the subfloor from underneath. This usually means the finished ceiling of the floor below would have to be removed, or installed in a crawl space beneath, which is ideal.
The radiant tubing is then attached either through stapling or radiant joist tracks from underneath. A high temperature tubing will need to be used because hotter than normal temperatures will be required for the heat to penetrate through the subfloor and whatever other floor coverings exist above. Radiators can be installed in rooms as an alternative to staple up distribution. Some radiators are the long baseboard type and others are boxier. Air handlers with heat exchangers can be installed to use the old ductwork with the new hot water heat system.