Radiant Under Floor Installation: "Tricks of the Trade"
Until somebody comes up with a better hot water delivery system, radiant heat tubing
will be a major component of all radiant under floor installations.
Pex tubing isn't hard to work with, but there are tricks of the trade you can employ to
make the job go faster and still end up with a first class install.
Another option is Pex or Wisbro clips which attach to the subfloor and allow the
tubing to hang an inch or two below the subfloor.
A third device for tubing support are slide brackets pictured above. These allow for
quick install and, like other fasteners, reduce noise by allowing effortless expansion
and contraction of the polystyrene piping.
Here are some of the "tricks of the trade" that will help the work go easier.
1. Run the tubing when the joists are as unobstructed as possible, before the other
trades do their work and before cross bridging is installed. Work from below
whenever possible. Push and pull at the same time. If you pull too hard on the pipe
without pushing, you will get a kink. Have someone feed the tubing to you. Work
with the tubing at room temperature. Tie a rope around the coil to keep it together.
2. Don't try to work with a length of tubing that is unnecessarily long. Anything
longer than 200 ft. will become more difficult as the tubing must pass through more
holes. If the work becomes too difficult because there are too many holes and
joists, cut the tubing and start again. Couple the tubing ends together later.
3. Tape the open end of the pipe to keep out sawdust and dirt.
4. Each tubing has a minimum bending diameter and if you try to make a sharper
bend, you are likely to get kinks. Smaller diameter tubes can make sharper turns
but they put out less heat and have higher costs. In general, work with the largest
tube you can.
5. The more workers, the easier the work will proceed. It is ideal to have one
person at each point where the tubing turns. For do it yourself projects, it is a good
excuse for a party.
6. Consider skipping every other joist space, and then, at the end of the building,
turn around and come back through the joists that you missed. The advantages are
that the turns will be wider and that there is no need to run a return pipe.
Alternative-Heating-Info.com
Aluminum transfer plates, as the photo on the left
illustrates, hold the tubing in place and transfer the heat
radiated from the tubing to the subfloor. But transfer
plates are expensive.
A 900 square foot parallel run like you see here would
cost around $1,600 just for the plates. So it's not
surprising if a radiant system designer chooses to forego
the plates in favor of less expensive foil barriers.
The foil barriers used to insulate hydronic tubing have
the same properties as a radiant attic barrier, which
means 97% of the radiant heat is reflected upward
creating a heated air space while only 3% is emitted,
or allowed to escape from the joist cavity.
The cost to insulate the same 900 sq. ft. using a foil
barrier would be around $400, or 75% less than
transfer plates.
If you use a radiant barrier instead of transfer plates
to conduct the heat upwards you'll need an alternate
method to secure the radiant tubing in place.
The quickest method is using a Mangone staple gun
with "stand off" staples to secure the tubing to the
side of each joist.
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