What is the best method to insulate beneath PEX pipes installed under floor joists for radiant heat?
Maureen Ryan| Posted inEnergy Efficiency and Durabilityon
In our new house construction PEX pipes have been installed beneath the first and second floors to provide radiant heat to the rooms above. The pipes have been attached beneath the floors in a crisscross loop design between the joists.
Is it possible and is it advisable to also install heat transfer plates where the pipes do not run in straight parallel lines?
Is the type of reflective barrier that has foam insulation sandwiched between the 2 reflective layers sufficient insulation? If not, what is the best way to insulate beneath the pipes and what R value is recommended?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Ask your civil engineer/architect what he/she thought when ordering such job.
The thermal load and supply must be calculated before building starts.
The foil backed insulation boards make little sense in terms of thermal distribution.
As previously answered by Hein, a proper room heat loss analysis and hydronic radiant floor heat gain analysis should have done BEFORE the installation. For the floor/ceiling situation described, one could have avoided insulation altogether and designed both a hydronic radiant ceiling for the lower rooms and a hydronic radiant floor for the upper rooms.
Are you interested in insulating between the first and second floors? If so, why? What is below the first floor?
Every job I have seen has had HighR board, or in one case luan and spray foam. I am not saying it makes engineering sense, that is just what heating contractors seem to be doing. I think it started because they didn't want to heat the ceilings in basements.
Maureen,
I suggest you read two previous threads on this issue, plus one article:
Heat Transfer Plates for Radiant heat under floor joists
Reflective barrier and insulation for radiant heat
Lessons Learned the Hard Way