Extreme:
-20F outside, +70F inside, .35 a.c., garage heated and ventilated as house - 41,740 btu/hr
Typical:
+15 outside, +70 inside house, +50 inside garage, house ventilation .2 a.c., garage ventilation .1 a.c. - 25,188 btu/hr
Surfaces:
House ceiling: 832 ft2 R40 U*832*90 = 1872 btu/hr
House basement floor: 832 ft2 R20 U*832*35 = 1456 btu/hr
House upper level walls: 1044 - 112 = 932 ft2 R18 U*932*90 = 4660 btu/hr
House upper level windows: 112 ft2 R5 U*112*90 = 2016 btu/hr
House ground level walls: 1160 - (100 + 21) = 1039 ft2 R18 U*1039*90 = 5195 btu/hr
House ground level windows and door: 121 ft2 R5 U*121*90 = 2178 btu/hr
House basement walls: 928 - 20 = 908 ft2 R22 U*908*60 = 2476 btu/hr
House basement windows: 20 ft2 R5 U*20*90 = 360 btu/hr
Garage floor: 988 ft2 R20 U*988*45 = 2223 btu/hr
Garage ceiling: 988 ft2 R40 U*988*90 = 2223 btu/hr
Garage walls: 1428 - (126 + 46) = 1256 ft2 R16 U*1256*90 = 7065 btu/hr
Garage door: 126 ft2 R12 U*126*90 = 945 btu/hr
Garage windows and door: 46 ft2 R5 U*46*90 = 828 btu/hr
Total: 33,497 btu/hr
Infiltration calculation using LifeBreath HRVs:
Building Volume: 22464 + 13832 = 36,296
Infiltration: 36,296/60 X .35 = 212 CFM
Incoming air temp: 90(.6) + (-20) = 34
(delta T)(effectiveness) + outside air temp.
1.08 X 212 X 36 = 8243
Total load: 33497 + 8243 = 41,740 (muni worksheet shows 77,279)
41740 X 1.33 = 55,155 minimum heating plant size required
THIS FIGURE ASSUMES FULL GARAGE TEMP (+70) AND FULL GARAGE VENTILATION (.35) AND IS CONSERVATIVE IN THE HRV EFFECTIVENESS ASSUMPTION (.6)
Weil-McLain CGS-3 Boiler Rating: 57,000 (DOE Heating Capacity)
Fireplace Maximum Input Rating: 42,000 (steady state efficiency up to 87%)
Total load by space:
volumes: basement=6656(.1834) ground=7488(.2063) upper=8320(.2292) garage=13832(.3811)
Basement: 4292 + 1511 = 5803
Ground: 7373 + 1700 = 9073
Upper: 8548 + 1889 = 10438
Garage: 13284 + 3141 = 16426