radiant floor

Eric_10

I am atempting to add a zone of radiant heat to a bathroom.I currently have baseboard in the rest of the house. I am a heat tech with more expierience on the warm air and hot water end not very familiar with radiant. This is for my own house. Ive ran the zone already with a mixing valve and stapled the wirsbo to the subfloor underneath. should there be anything between the piping and insulation to assure the heat will penetrate the floor and not just warm the insulation. Thanks for any help

Mark Eatherton1

Ya mean...

like a mirror or something?

Lets think about this for a second. Let's say you owned a mirror factory, and you over produced a whole bunch of cheap mirrors that were 14-1/4 inches wide. They were PERFECT for putting between the floor joists to reflect the radaint energy coming from the tube in the joist bay.

Sounds like a good idea from the outside... Now, lets climb into the bay after, say a year of operation. Your perfectly clean mirror, which WAS good at reflecting energy back towards its source is now covered with DUST. Look in that mirror. Can you see a good reflection of yourself? If you shine a bright flash light on that surface, does a lot of it bounce off the mirror? Is its spectral reflectivy influenced by the dust?

Put the foil in your attic. It's been proven to be effective up there...until it gets covered with dust...

Got pictures???

ME

Tom Meyer

Insulation

I agree with Mark about how long "reflective insulation" is truly reflective. But lets look at a couple of other things. The insulation only slows down the rate of heat transfer between two temperatures. The greater the temperature differential (delta T), the greater the rate of heat transfer. Insulation is rated on its ability to SLOW the rate of heat transfer. There is no perfect insulation which would stop the heat transfer. One thing that would help in your situation is making sure there is an air gap between the staple up tubing and the insulation. The air would act as an non-conductor.

Tom Meyer
Senior Designer/Trainer
Precision Hydronics Corp
www.precisionhydronics.com

S Davis

Staple Up

You would be better off using PEX Clips to stand the tubing off the wood to limit expansion noise, and leave a air space in the top of the joist space to help spread the heat.
PEX tubing expandes 3" Per 100' Per 10 deg. temp rise.

S Davis

Weezbo

heat goes to cold.

not much can be done about changing any of the Laws of physics.crank up the recirc,set the mixer as close to ideal room temp that you'd like, insulate the space Under the pipes and leave it alone.

DAVID R. FAUVER

insulation

me i prefer a slab but if stapled up under i use the double bubble with a reflector side then standard insulation.

Unknown

Not sure if you're using a different kind of PEX, or maybe you read temps in Celsius, but Wirsbo lists expansion at 1.1"/10deg F. temp rise.

Also you need to make sure your joist penetrations are large enough to accomodate expansion.

do not staple tubing directly to the subfloor without plates. do not use lightweight plates with a "dial a temp" system unless you are using PEX-AL-PEX which doesn't expand much (but is a pain to work with in joist cavities).

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Robert Brown, Co-Owner, RPA certified Radiant Designer

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