Replies

1. 
   TLRice | Sep 24, 2002 02:51pm | #1

   MM,

   "...the use of finned copper tubing in an under-sub-floor application of radiant heating"

   Copper tubes with aluminum fins is primarily used as a convector in heating applications. To be effective it requires air movement over the tubes/fins. Not going to work very well for radiant floor heating.

1. 
   CloudHidden | Sep 24, 2002 03:21pm | #2

   Tim, could he have meant the alu plates installed under the floor, and not the radiator-looking fins? Some people call the plates fins.

1. 
   mathman6 | Sep 24, 2002 04:46pm | #3

   Hi Cloud Hidden!

   THank you for your reply.  Actaully I'm not sure whether my brother ment fins or plates, but assuming plates, would copper work ok or better than plastic tubbing?

   Thank you!!

1. 
   CraigerMan | Sep 25, 2002 12:50am | #4

   I just built a house using a combination of radiant floor and fin tube baseboard.  You're going to what to use 3/4 copper to supply all your baseboards.  Depending on the amount of zones, you may want to have them all come back to a manifold.  The radiant floor tubing runs at a different temp, so you'll need regulator for that.  Attach the tubing, with the reflective tin, under the sufloor.  I've got each bedroom and each bath on its own zone, and we love it!

1. 
   mathman6 | Sep 25, 2002 12:59am | #5

   many thanks for your comments! 

   What kind of insulation did you use in between the floor joists?  Did you leave any space between the tubing&reflective tin and the insulation?

2. 
   CraigerMan | Sep 25, 2002 01:09am | #6

   All you need is R-11, but I used 19.  The tubing is held up by the tins, so there isn't any space between them.  You don't want to the tins to touch or overlap.  Leave a 1-2" space between each one.  The insulation goes kraft side towards the tubing, touching but not squished.

3. 
   Mongo | Sep 25, 2002 05:20am | #7

   If you're going hybrid (RFH and baseboards), you'll have to split your system as craigerman described.

   Typically, the baseboards will run hot, at about 160 degrees. You'll have to temper the water fed to your RFH so it's in the 100-115 degree range.

   Skip the copper. Honestly, you're gaining nothing and actually making the job more difficult, with more potential problems. Stick with a good quality PEX.

   You may or may not need the Al plates, you can only find out if you do by running BTU calcs. I'm in CT and only a few times have I used plates in a staple-up.

   I staple the tubing to the bottom of the subfloor. I then rip 4-by-8 sheets of foil-faced polyisocyanate insulation (R7.2 per inch) to the proper width and friction-fit them between the joists, tucking the RFBI up until it hits the bottom of the staples. The staples cradle the tubing, and the plastic cradle on the staple has a flat face that will hold the polyiso about 1 1/4" off the bottom of the subfloor.

   Try to have three times the insulative R-value BELOW the tubing as you have in construction materials (subfloor/underlayment/hardwood/tile/carpet pad/carpet/etc) above the tubing. This will encourage the heat to go where you want it...to the intended living space. For example, on a second floor, you want all the second floor RFH going to the second floor. You don't want it overheating the first floor via the ceiling. If the polyiso doesn't give you all the R-value that you need...or want...then you can friction-fit unfaced FG batts between the joists, too.

   RFH...muy bueno.

   Edited 9/24/2002 10:27:24 PM ET by Mongo