Radiant Heat not as great as it could be

[bfournier]

I spent the last three weeks installing about 700 feet of 1/2 inch Pex pipe between the first floor joist of my (not new construction) home. I installed in basement by stapling pex up to the floor. I have five loops running off my boiler with a separate zone and circulator. I have tested the supply water at anywhere from 125-165 degrees. Full circulation and have purged all air from each loop. I have a layer of reflective insulation (the thin kind that looks like bubble wrap covered in a reflective layer) and then stuffed R19 insulation under the reflective layer in between the joist. I have an inch to two inches of space between the pipe and insulation.

Here are concerns. I have never had radiant heat. It is not my only source of heat as I have forced hot water baseboards also. After about 2.5 hours the floor only gets to around 68 degrees. I am measuring surface temp with infared. I have hard wood and ceramic tile. I expected the floor temp to be higher. I have come this far and am wondering if it was worth the financial and time investment at this point. Is it worth even installing radiant heat without the heat plates? My joists are 12 inches on center. Where is the best place for a non contractor to get heat plates?

[Who]

Originally Posted by bfournier

Where is the best place for a non contractor to get heat plates?

I just go to the same places as the contractors. Go in realizing that you aren't a regular so you are lower priority and know exactly what part number(s) you need. I get good discounts to boot.

After about 2.5 hours the floor only gets to around 68 degrees.

From what temp? That floor is gonna warm up and cool down at a much much much slower rate.

How does it do with a steady t-stat? How are the tubes attached to the underside of the floor?

The plates, give the BTUs a much nicer conduction path to the floor and that is important.

[bfournier]

floor gets to 68 when the supply is around 165 degrees. The pipe is attached to the underside of the floor using the Pex plastic pipe "holders" that nail to the underside of the floor. When I am testing the floor temp I have the thermostat for the radiant zone set at 80 degrees...constantly calling for heat and circulating water.

Probably going to try to get enough plate to do one loop to test the performance.