Heat Load Calc – 1 Room Electric Floor Heat
Hey guys,
I have an unusual room to do a load calc on. It’s a garage with a freestanding room & ceiling framed inside.
Zone 9a: (20°F to 25°F)
Approximate nominal R-Value:
Rear wall: R130 (yes.. 130!)
R Wall: R40
L Wall: R64
Front Wall: R22
Floor: R9 (EPS over slab, subfloor, laminate)
Ceiling: R40
Room Area: 220sf
Do to circumstances, the longest baseboard heater I could put in the room is 4′, and it would be a most unwelcome addition to the room’s use.
Heat pump would be ideal, but no budget for it, so I’m looking at electric in floor heating at 12w/sf and working out how many sq ft of in floor heating I need for the room. Most of the time only one half of the room will be used by 1-2 people.
If I can size the floor heating well enough I don’t need to add the baseboard that would be ideal.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
The formula is BTU/hr= (temperature delta)*(square feet)/Rvalue
Calculate that for each of the six sides of the room. Add them up. One Btu/hr= 0.293 Watts.
Are there any windows or doors? You'll have to do them separately and add them to the total.
For temperature delta, look up your county here:
https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/County%20Level%20Design%20Temperature%20Reference%20Guide%20-%202015-06-24.pdf
and use the 99% heating temperature as your outdoor temperature, subtract that from your indoor temperature.
My initial impression is you should be able to do this.