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[atvalaska]

  well last Sunday was the day to fire my boiler as the weather was going to chit soon! I  just got the slab heat all plumbed in  and was to start on Saturday the 24th but it was taking me a long time to wire the 24v system up , I got things going and got all the air out in no time , here's where I thought things went wrong... It ran 24/7 till  Tues eve.. Near 3 days to get it up to 60 with my laser temp sensor on the concrete surface! But by weds eve all was well . i started the heat with a slab temp of 28/31 degs...dont do that again !....am now heating a shop with a 1200sf footprint, and 12' to the top plate walls, AND my house in progress, with the same footprint but  28' to the top plate !  Only the slab is hooked up in the 2/1/2 stories hom  I have r 30 walls and r 75 in the roof   the slab on grade in the house  thermostat is/was set to 67 and the top floor  is 46 degs... ...Hot molecules are  keeping my house warm .....or if u are all redneck like me ...heat rises - thereby keeping my azz warm ....all this with a outside temp around 17 to 22 and a lite wind  average of 6 mph over the last week ! , I'll add pics at some point , but winters here and I'm off and running ! I have warmboard on the next two floors up ...but I will have to get more done before I get them on line ...

[slimjim]

Oh yes it certainly does rise BUT try putting the same BTU's into the top floor and forcing it down, it ain't going to happen, the basement will be pretty darn cold. Another great thing about a radiant slab is the thermal storage you now have, it will take days for the slab to cool off again to ambient temp.

[cartod]

"In any discussion of radiant ceilings and comfort, there seems to be some ingrained misunderstandings of the concepts.  Someone will say that “heat rises, therefore you’ll have a hot head and cold feet”.  Not true.  Heat doesn’t rise.  Hot air rises.  In radiant systems objects of mass are heated without heating the air.  In fact, there is typically more hot air rising with a radiant floor than with a radiant ceiling.  This is because air molecules that come into contact with the radiant ceiling already occupy the highest strata. In radiant floors, the cooler molecules sink and come into contact with the warm floor surface and rise as their density changes with heat, driving the convective forces that cause stratification.  Under normal conditions neither radiant floors or radiant ceilings heat the air to an uncomfortable level like in forced air systems, however."