Just Me wrote:
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.

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