There is no question in my mind anymore that a radiant floor, if done correctly, is the most economical way to heat a structure. Sure, that method has some disadvantages such as not being able to quickly change the temperature in the building, but overall I have found no other method of heating that will provide the comfort level and overall long term economy of a radiant slab. These advantages are amplified in the case of any structure with high ceilings....which I would define as anything over 10'.
The building in the pictures here heated the entire season last year with pellets. The owner went through 7-1/4 tons start to finish which equaled about $1,400 total cost to heat a 6,400 sq ft building. Hot water was provided with a Windhager BioWin260 which is rated at 88,000btu maximum output.......so much for the old rule of thumb assuming 30btu/sq ft........
Interesting to note that the temperatures at the ceiling in the 16' part run about 3* cooler than the temp at "human height". This is the huge difference between a radiant system and one using forced air heating where you would typically see ceiling temps running 10-15* warmer than at the floor.
It is typical pole barn construction which yields a wall cavity of about 8". The whole building is blown cellulose with the walls being 8" and he has 14-16" in the ceiling. The center 3,200 sq ft has a 16' ceiling and the lean-to sides are each 1,600 sq ft with 9' ceilings. The entire structure was kept at 65* 24-7.
The slab edge and the entire floor was done with 2" foam and the slab itself is 6" concrete. As you can see there are pretty substantial door openings so the 8" thick wall insulation only applies to maybe 60% of the total wall area. The overhead doors are all 1-1/2" foam insulated for an actual R-value of maybe 7.5. The North and west walls are mirror image of what you see in the pictures of the East and South so you can get a rough idea of total door and window area.
Regarding wall insulation, we are seeing a lot of hybrid application being done now. They spray 1' of closed cell foam on the outer wall and then fill the rest of the wall cavity with cellulose. This gives the advantage of total air sealing with the foam and the sound deadening quality of cellulose while keeping total cost reasonable. It's an excellent system and in reality, anything beyond that rapidly reaches the point of diminishing return.
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