Replies

1. 
   johnnyd | Mar 16, 2004 08:40pm | #1

   Probably should place 2" of rigid underneath the whole slab and pay attention to the perimeter of the slab.  You don't want to grow dandelions in January.

   As far as the cost goes, unless you can get off-peak dual fuel rates, electric resisitance will probably be higher cost per BTU:

   http://www.cngcorp.com/customer_sales_service/fuel_cost_charts.html

   Check with your PoCo.

   Have you had a heat loss calculation done?  You can only pack so many BTUs into tubing, so how much tubing, the size of the tubing, the size of the boiler, placement of the tubes in the slab, etc  have everything to do with your "design temperature"...which is how warm you want the interior to be on the coldest day of the year.  For a workshop like this, will you be frequently opening big overhead doors in the middle of winter?  If so you should specify a slab sensor which will keep the slab at a fairly constant temperature...the space will feel warm quickly after closing the door without a big fan kicking in and blowing hot air around.

   As far as which way is the right way, you should make sure the contractor has done a few sucessful installs, and go eyeball them and talk to the owners. 

2. 
   whoover | Mar 16, 2004 08:59pm | #2

   Any way you want to put it, a BTU of heat generated from electricity is a lot more expensive than that generated from burning gas.  My experience is in water heaters...even very efficient electric water heaters are about 3 times more expensive to operate than less efficient gas heaters.  If gas is available and possible, I would not even think about heating with electricity.

3. 
   aj1201 | Mar 17, 2004 12:09am | #3

   i do lots of radiant and yes sending the plans out is the best for you. You can only get so much btu per sq. foot out of the floor so you need to know ahead of time if you need additional heat and they will tell you size of tubing and spacing. Radiant is very flexible but i have yet to hear of 12 inch spacing not to say its not possible the one thing would be 12 inch with larger tubing. Oh and let me say i mean 12 inch residential i have seen it commercial and with large tubing and the floor ran 24 7 it does make a difference.Send the plans out and use the person who wanted to do the right thing for you in the first place.

1. 
   UncleDunc | Mar 17, 2004 12:20am | #4

   If somebody is going to use electric heat, wouldn't it be cheaper and easier to skip the boiler, pumps, tubing, etc. and put heat cables in the floor?

1. 
   aj1201 | Mar 17, 2004 01:53am | #5

   Im not sure where you live but here in the norht east electric heat is way to expensive to run so we have very little of it. So im not so upto date on it. The electric radiant i beleive is what you are refering to i have heard bad things about but no personal experience.

4. 
   steveodiy | Mar 19, 2004 10:21pm | #6

   I installed my own radiant system.  Staple up 7/8" 12" OC. It was a bear to thread pex through the joist but in the end my oil bills are lower and my house is warmer.