Do you have a garage door that provides a good air seal? I have yet to see one.

At first, I wasn't too pleased with the vinyl flap the garage door company installed on mine. I made sure the seals extended full length, particularly on the bottom. However, it's not as bad as I thought it was going to be. It's noticeably more difficult to close the door to the house with the garage doors down because of the overpressure condition generated. Today I was working in the garage with the doors shut. They face North and there was a bitter cold wind about 15k out of the North, but wasn't feeling any leakage. Most of the heat loss I felt was going through the door, not around it.

Speaking of climate ICF, I bet you are greatly enjoying the benefits of your passive solar home design this weekend, eh!

19F overnight. That's just about design temp. Thermostats set for 68F all night. With the Winter Solstice only about three weeks away the sun came in all apertures at maximum starting at sunrise. By the time the sun set at 4:15, it was 72F. Nice and toasty for a cold day. The garage was the only zone calling for heat.

Sweet ICF...and I know exactly what you mean!

Posted By jonr on 30 Nov 2014 01:41 PM
  ...And pumping doesn't add to the electric bill in cases of electric heat.

In this case it does.  He is using an electric hot water heater for his "electric heat".  The pump is needed to move the hot water from the tank to the radiant slab.

Posted By jonr on 30 Nov 2014 01:41 PM
Of course average loads are less than 50% of design loads.

Yeah, but in this case there is no design.  We are all just guestimating his loads.  And without any insulation in the ceiling I'm guessing his heat loss is pretty high.  And the fact that he has a floor slab that is already 32F and it isn't even winter yet tells me that he is pretty far north.

Right, lots of guestimating given the limited data to work with, but likely not too far off the mark either…

The pump is needed to move the hot water from the tank to the radiant slab.

For a given room temperature, every watt used to move water is one less watt used by the hot water heater. No net cost effect.

What type of insulation, if any, is around the PERIMETER of the slab?

The OP hasn't responded since the end of November.

hehehe, sure got you going though. ICF, the smartest man in the room...today! Well done and Merry Chistmas!

Posted By Jay Cooley on 29 Nov 2014 08:44 AM
I'm new to this Forum, and could use some much needed help please, What I have is a 32x64 garage with a 4" slab, using a 40ga. electric Hot Water Heater, with 5/8 Pex with an Oxygen Barrier through out the floor for a total of 2000', Also have a 7 zone manifold purchased from Pex supply store, I am not worried about control each zone of the garage it is all open, so zoning control is not needed, I did the math and for a total of 2000' of pex it takes 27.5 gallons to fill the pex, so I figured a 40gal Hot Water heater would be sufficient enough to do what i'm trying to accomplish, The pump i'm using is a Grundfos Type UP 26-96F Flow range: 0 - 34 U.S. GPM, Just a note i'm using only this pump to move the flow, but have had luck started the process the night before getting the water hot then starting the pump, it was it was 32 degrees when I started it and the next morning it was still 32 degrees what needs to be done to correct this problem I tried attaching a few pictures on what I have, but to much data, all suggestion and replies

replace with a TANKLESS WATER HEATER 160kBTU and be all set / set temp to 120-130 deg