Ready to install PEX under the floor. Two little questions...

Are you going under the subfloor? You may need something like this to radiate the heat up http://www.pexsupply.com/Wirsbo-Uponor-A5080500-Wirsbo-Joist-Trak-1-2-Heat-Transfer-Panel-2111000-p

Gary

I have been doing a lot of research on various methods for radiant heating-mostly on these sites:

http://greenbuildingtalk.com/Forums/tabid/53/view/topics/forumid/12/Default.aspx

http://www.heatinghelp.com/forum-category/92/Radiant-Heating

The pros on these sites strongly recommend to use of aluminum heat transfer plates. More specifically heavy extruded plates instead of lightweight stamped plates. Using plates can certainly add a lot of $$ to the job but you don't want to skimp here.

Now, if you don't have an accurate room by room heat loss for this building, you are just guessing. With new construction you may be just fine with what you have planned but it would be major drag if not.

I have read about plenty of radiant horror stories in the last few weeks and just want to make sure your on the right track here.

Noah

The best comprehensive radiant floor site I have seen is http://www.radiantdesigninstitute.com/. For his opinion of the aluminum plates see specifically http://www.radiantdesigninstitute.com/page4.html. Also he says you can have loops up to 500' if you have enough head.

When I installed my underfloor PEX I used a combination of talons and Watts nylon clips. I placed them approximately 16" and less in bends and that seemed to work well. The pipe is twisty when pulled of the roll. After heating and cooling it forms to whatever shape it has been in.

I did not use the plates and think that having a high head pump with appropriate delta-t will bring better performance. I used a TACO 008 Delta-T pump but others may have better suggestions.

YMMV.

Cheers,

Rurik

If building new, try if at all possible to put the tubing _in_ the floor, not under it-- wood is less of an insulator than most things that are officially used as insulation, but it's also one of the last things you'd pick-- at least any thicker than you can help-- to transmit heat.

Sounds like you are going under floor. If so:

Keep the loop short, in my opinion 300' is too long, I wouldn't go over 200. Alternate the loops so that the hot water is close to the same temperature over the area.

You need heat spreaders for underfloor. They need to be full soft, if not send them back and purchase full soft ones or they will squeak and pop.

However,
In hind site I would make my own by using a wood block with two groves to form the U shape (you can bend with fingers, or a push stick). Full soft aluminum flashing is not hard to find.

Use the flashing for 3/4 of the tubing run; that way it won't be impossible to install. The heat spreader drawings are online, if I remember correctly the spreader is 12" wide with two U shaped groves that the 1/2 pex snaps in to. I installed these with 1/4" X 3/4" long staples.