Replies

1. 
   Tom_Laing | May 27, 1999 09:29pm | #1

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   Deborah,
   In-floor heat is quickly becoming the heating method of choice in my part of Alaska. Here, we use mostly oil fired boilers because we don't have natural gas. I have yet to talk to a single person who has lived with it who doesn't absolutely love it. As far as installing it over unenclosed space such as a carport, you would need to insulate under the floor to the extent that heat would radiate up rather than down. The amount would depend on heating requirements for your area. Seems like a good choice of insulation would be a spray foam that would not only insulate, but would limit the amount of heat loss from air movement under the building. Most people here install the distribution piping in a thin, light-weight slab like "Gypcrete." Most common is a 1 1/2" solid pour, but it's also done as a 3/4" pour between 1X sleepers. The sleepers are usually installed if nail-down wood flooring is to be used.

   Tom Laing

2. 
   Guest_ | May 28, 1999 05:52am | #2

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   Like Tom, I think radiant is terrific. I've installed it in both gypcrete slabs and underfloor, it works well with both as long as it's properly installed.

   If underfloor is your choice, use the fasteners the manufacturer sells. They cradle the tube and reduce friction noises when the tube expands/contracts in a heating cycle.

   Where the tube passes through the joists, it may help to line the hole with a sleeve of foam or cardboard, which, once again, will help to minimize friction noises. I've never had noise problems, they usually only occur when the tubing is pulled too tightly in installation. This could result in a bit of friction noise as the tube moves.

   Under the tube, put a minimum of 1/2 inch foil-faced foam board insulation. It will act as a radiant shield to "direct" the heat up, through the flooring. Below this, use additional insulation as required, cells or FG batts. You need the foil right below the tubing, though.

   If you're particularly concerned with heat loss, go with 5/8th inch tubing instead of the more traditional 1/2. Regardless, whoever you purchase the tubing through should be able to work up a heat-loss model for you.

   Regards, Mongo

1. 
   Guest_ | May 28, 1999 08:51am | #3

   *Deborah, I'm another Alaskan who'll chime in with Tom on the advantages of radiant floor heating. And I'm ahead of Tom because we live on top of a natural gas field on the Kenai Peninsula. $0.38/therm which is at least 40% less than most people pay for NG. And way less than anyone pays for fuel oil. Really nice to radiant heat a garage in snow country. The car thaws really quick with the heat coming from below the car. Most of my system is radiant slab, but some of the second floor is heated with 1/2" PEX tubing run down and back each TJI bay (about 8" on center, average). I don't need insulation below it because it's also a heated space. I went that route (rather than gypcrete pour the second floor) because it eliminates that added weight (serious seismic concerns up here), concerns that cracking with movement, and a derth of proven onstallers. The underfloor PEX I can do myself. The standard thing is to staple the tubing to the subfloor with a special stapler. But I'm putting mine on spacers to gaurd against the possibility of a future nail hit (which can be located and repaired, but is a pain). -David

1. 
   Guest_ | May 28, 1999 03:40pm | #5

   *Anybody have experience with the newer, electric radient mats for installation under ceramic tile?

3. 
   Deborah_Poliner | May 28, 1999 03:40pm | #4

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   I am an architect working on an addition which is above unenclosed space 15 feet above grade. Maintaing even heat in spaces situated like this is always a problem. I would like to hear from anyone who has had experience -good or bad- with radiant underfloor heating.