Radiant heat question

[Just Me]

Hi,

I have a question for anyone having actual experience with a floor based radiant heat system.

I'm planning on installing a hydronic between-the-joists system. It will use PEX fastened to the underside of the subfloor. The person who'll be helping me with the install, and has installed these systems before says that the aluminum heat diffusers you can apply along with the tubing are useless, especially if you're using water heated to about 100F. I've been reading Siegenthaler's book on the subject and he's absolutely in favor of their use.

Does anyone have any comments? My biggest concerns are 1) will the system be more efficient and able to react faster when needed, and 2) will you get hot stripes on the surface of the finished floor without them possibly leading to premature degradation of the hardwood flooring finish.

FYI, I plan on using mostly hardwood flooring (some tile). Subfloor is 3/4" advantech. House is mostly one floor with a full basement. Joists are 16" on center.

Thanks for your input.

[buffalobill]

[RicodJour]

With hardwood floors you want to try to equalize the heat distribution underneath the floor. Hardwood floors expand and contract with temperature and humidity and the radiant amplifies the expansion and contraction. The hotter areas will have larger gaps and that can tend to look off. Use the diffusers.

R

[marson]

It is critical that the joist cavities are insulated with reflective insulation. Haven't used it myself, so I'm not exactly answering your question, but this is what I am hearing from our plumbing supply house in Duluth, MN. If it works here, it ought to work anywhere.

[Edwin Pawlowski]

Heating engineers spent a lot of money on R & D to come up with the ideal method of heating the floors. What has your friend done for testing? Use the diffusers.

[Steve Barker LT]

#1. if your water is only going to be 100 degrees, don't bother. #2. if you don't "radiate" the heat out from the tubing, what's the point? the aluminum plates are essential for this type of install.

[RicodJour]

#1 and #2 seem to offer conflicting advice. What are you recommending?

R

[Just Me]