You can use the design and materials criteria to calculate heat losses and evaluate the most practical and efficient ways to reduce them.
a Btu is a measurement of the heat required to raise one pound of water one degree F.
The sun can provide 306 Btu per square foot per hour
One kilowatt of electricity is equivalent to 3412 Btu
|
Design Criteria
SURFACE
|
DESCRIPTION
|
AREA
|
R VALUE
|
U VALUE
|
LOSS FACTOR
|
BTU/HR
30 degrees
|
BTU/24Hr
30 degrees
|
FLOOR
|
1" Gravel + Fabric
|
144
|
|
.4
|
57.6
|
1728
|
|
FLOOR
|
VB + 1.5" beadboard Insulation
|
32
|
5
|
.13
|
4.16
|
120
|
|
SILL
|
Wood timber 12"
|
20
|
|
.8
|
16
|
480
|
|
REAR
|
VB + Frame Wall
|
176
|
11
|
0.7
|
40.3
|
1200
|
|
REAR
|
VB + Windows
|
20
|
|
1.0
|
20
|
600
|
|
SIDES
|
VB + Foil Faced Insulation + Fabric
|
80
|
7.2
|
.16
|
12.8
|
3850
|
|
KNEEWALL
|
VB + Fabric
|
44
|
|
1.6
|
71.4
|
2100
|
|
GLAZING
|
VB (4mil poly) + Fabric
|
264
|
|
1.6
|
392
|
11760
|
|
|
TOTAL CONDUCTIVE LOSS
|
|
|
|
594
|
17820
|
508280
|
INFILTRATE
|
Door + Sill + VB (est .25 x total)
|
|
|
|
119
|
3570
|
90000
|
VENTILATE
|
500 cfm x .18 (.6/min x 880 cu ft)
|
|
|
|
|
|
|
|
TOTAL HEAT LOSS
|
|
|
|
713
|
21990
|
598300
|
SOLAR
|
(est 200) Btu x glazing x 10 Hr
|
392
|
|
|
200
|
|
784000
|
|
NET HEAT GAIN
|
|
|
|
|
|
185700
|
STORAGE
|
Water 2.27 gal/sq ft
|
400 gal
|
|
8.33 #
|
3320
|
99600
|
|
SOIL MASS
|
100 gallons soil/gravel x (5?)
|
|
|
|
500
|
15000
|
|
AUX HEAT
|
1500 W radiant heater
|
|
|
|
5100
|
|
122400
|
BENCH
|
2 - 250W heat cables (3412 btu/kwh)
|
32
|
|
|
1706
|
|
40944
|
|