Replies

1. 
   mwilly | Aug 17, 2006 04:06pm | #1

   4'x8' 1/2" polyiso foil-faced isulation board

   Cut strips to width of space between joists for friction fit, i.e. 14 1/2"x48" for 16" o.c. joist spacing

   No need for fasteners, just push up into place

   Install unfaced 6" fiberglass batts under, support with wire or other means

   1/2" polyiso is aprox 3.3 r-value, 6" fg is r-19

   14 years ago I did mine this way, floors are very evenly heated, nothing better than a warm ceramic tile floor in your kitchen on a cold winter day

   Mark

    

1. 
   mcrowleynh | Aug 17, 2006 05:46pm | #3

   Hi Mark,

   Thanks for the reply, I really appreciate it. 

   I agree with you, but I fear the combustability/ smoke from poly-isocyanate (sp?).    I would prefer fiberglass for this reason, what do you think?  Also, I have some (little)fear of out-gassing of the poly-iso.

   Does the poly iso offer anything over fiberglass other than theease of install?

   Thanks again,

   Mike

2. 
   johnnyd | Aug 17, 2006 04:37pm | #2

   How far are the fasteners (staples) holding the PEX to the subfloor apart?   

   You can get lightweight aluminum plates that are only ~ 12" long, have pre-formed grooves that fit the PEX tightly. Fit in and staple up to the subfloor as many as you can get between the existing staples..or maybe even pull a few existing to make room for the plates. 

   You will not be sorry, as the plates provide bona-fide conduction and emission, allowing for more even heating and especially lower water temperatures.

   Then continue with insulation per the other poster.  Good luck.

1. 
   mcrowleynh | Aug 17, 2006 05:55pm | #5

   JohnnyD,

   Thanks for the reply.

   Yea, I see what you are saying. 

   The staples are of variable distance, some 5", some 18", most look 18" so I guess I could pull some staples and reattach with the plates.   Also, there are 2 tubes between each joist, the distance between the tubes is highly variable.  Retrofitting someone else's work is no fun. 

   Sounds like a lot of work, but most on this board seem to agree with your approach.  I have a lot of critical project before winter, was hoping for a quick approach that'd work as well, but looks like your approach would offer a big benefit. 

   Thanks for the help.

   Mike

2. 
   mcrowleynh | Aug 17, 2006 06:03pm | #7

   JohhnyD,

   Any recommendations on plate vendors?

   Mike

1. 
   johnnyd | Aug 17, 2006 07:27pm | #8

   I would Google on "Aluminum Plates Radiant Heat" 

3. 
   NRTRob | Aug 17, 2006 05:50pm | #4

   You're talking about two entirely different animals.

   Plates that fit on the pipe and touch the subfloor are not reflectors. They aid in heat conduction to the subfloor, and conduction is the strongest form of heat transfer. you'll get better output at much, much lower water temperatures, especially if you use a good heavy gauge plate. Whether this is a good thing or not, well it's always good, but whether it's good for your CURRENT system in its CURRENT configuration or not depends on how the system is set up. You currently have a high temp system and so if you don't have any mixing controls on the radiant, adding plates without adding mixing might be a bad idea, though I would encourage you to do both.

   Reflection helps a little, but it's not even in the same ballpark as conduction.

   -------------------------------------
   -=Northeast Radiant Technology=-
   Radiant Design, Consultation, Parts Supply
   http://www.NRTradiant.com
1. 
   mcrowleynh | Aug 17, 2006 06:02pm | #6

   NRTRob,

   Thanks, I appreciate your comments. I understand your points and the difference between the 2 beasts.

   Not sure what I have yet on the setup.  Perhaps it is best if I get a hold of the guy (if I can get him to call back) who did the install and ask him what he set it up for.  The job was never finished, the previous owner had some health issues and the project stalled.   I have to pck up the ball and run

   I expect it was planned for reflection, but hopefully I can move it easilt to conduction.

   Thanks again,

   Mike