burgie
Well-known member
Greetings,
As I read some threads I am seeing folks who installed (what I think are) rather small natural gas heaters in their shops (similar in size to mine) with apparent success. Maybe I am doing something wrong here but below is the formula for determining heater size I found online:
insulation quality x total cubic feet x desired heat rise) / 1.6 = Btu required
Before proceeding, here is a snapshot of my shop:
Size & Configuration:
30’ x 48” w/ 16’ walls. Ceiling is NOT flat but a raised collar design with a 2.5”/12” rise per foot run for the first 9’-3” from the walls and the center 12’ or so is flat and just shy of 18’ from the floor.
Floor:
Floor is 6” fiberglass reinforced 4000# concrete
Walls:
Walls are hemlock 2x8 – 16” O/C with R30 un-faced fiberglass insulation with 6 mil clear polyethylene plastic for a vapor barrier with all joints taped with Tyvek tape. Outside walls are 15/32” OSB, Tyvek w/ taped joints, 5/4” rim board, corners and window/door trim. Siding is ½” x 16” x 16’ engineered siding. Walls rest on 2x8 pressure treated sill w/ sill seal polystyrene insulation. Silicone beads were applied on the concrete foundation and again on the sill seal before bolting the walls down.
The interior walls will be 1x6 T&G pine for the first 9’ and the rest of the walls and ceiling will be ½” drywall.
Ceiling:
Ceiling will receive R38 un-faced
Openings:
I have six (6) 2'x4" awning windows, thermapane double insulated windows, one (1) 36" fiberglass insulated entry door and one (1) 12' x 12" Overhead Door with a R17.9 rating.
As I plug in the values I am using 0.5 x 23,040 x 30/1.6 whereas:
insulation quality x total cubic feet x desired heat rise) / 1.6 = Btu required
In this formula, use "5" for no insulation, "1.5" for little insulation, "1" for average insulation and "0.5" for very good insulation. I figured a heat rise of 25°F - 30°F so
0.5 * 23,040 * 30/1.6 = 216K BHT heater
Is this right? If it is should I go to 200K or 250K?
I am reading that some folks with structures similar in size as mine are using a 100K heater with success?? Am I missing something here? I realize maybe there are other factors that I may not be taking into consideration but I don't want to under-size...or conversely buy more than I require...
Any help would be greatly appreciated...
As I read some threads I am seeing folks who installed (what I think are) rather small natural gas heaters in their shops (similar in size to mine) with apparent success. Maybe I am doing something wrong here but below is the formula for determining heater size I found online:
insulation quality x total cubic feet x desired heat rise) / 1.6 = Btu required
Before proceeding, here is a snapshot of my shop:
Size & Configuration:
30’ x 48” w/ 16’ walls. Ceiling is NOT flat but a raised collar design with a 2.5”/12” rise per foot run for the first 9’-3” from the walls and the center 12’ or so is flat and just shy of 18’ from the floor.
Floor:
Floor is 6” fiberglass reinforced 4000# concrete
Walls:
Walls are hemlock 2x8 – 16” O/C with R30 un-faced fiberglass insulation with 6 mil clear polyethylene plastic for a vapor barrier with all joints taped with Tyvek tape. Outside walls are 15/32” OSB, Tyvek w/ taped joints, 5/4” rim board, corners and window/door trim. Siding is ½” x 16” x 16’ engineered siding. Walls rest on 2x8 pressure treated sill w/ sill seal polystyrene insulation. Silicone beads were applied on the concrete foundation and again on the sill seal before bolting the walls down.
The interior walls will be 1x6 T&G pine for the first 9’ and the rest of the walls and ceiling will be ½” drywall.
Ceiling:
Ceiling will receive R38 un-faced
Openings:
I have six (6) 2'x4" awning windows, thermapane double insulated windows, one (1) 36" fiberglass insulated entry door and one (1) 12' x 12" Overhead Door with a R17.9 rating.
As I plug in the values I am using 0.5 x 23,040 x 30/1.6 whereas:
insulation quality x total cubic feet x desired heat rise) / 1.6 = Btu required
In this formula, use "5" for no insulation, "1.5" for little insulation, "1" for average insulation and "0.5" for very good insulation. I figured a heat rise of 25°F - 30°F so
0.5 * 23,040 * 30/1.6 = 216K BHT heater
Is this right? If it is should I go to 200K or 250K?
I am reading that some folks with structures similar in size as mine are using a 100K heater with success?? Am I missing something here? I realize maybe there are other factors that I may not be taking into consideration but I don't want to under-size...or conversely buy more than I require...
Any help would be greatly appreciated...
Is that a manual J you ran? Given the spec you are building to with the excellent insulation 200 is just way large. The 125 will, I think. give you good comfort and good run times.