House Structure Specifications (Total floor area: 1540 ft
2 = 143 m
2
)
:
1.
Floor to ceiling height: 9 ft = 2.74m; Crawling space has an average temperature 10
o
C;
2.
Windows: 3x5 ft (WxH) per unit except Living room Windows 3x6 (WxH). All with double glass; 3.
Doors: 3x7 ft (WxH) per unit; 4.
Covered porch and garage are considered as outside;
5.
Average outside t
o
= -6
o
C, φ
o
= 80%; Room t
i
= 22
o
C, φ
i
= 30%.
The upgraded structure includes additional insulation, air tightness. See Table below. Find:
1.
What’s the heating bill the month of January, if heat (nature gas) is 3¢ per kWh?
2.
What’ percentage of energy saving for the upgraded house compared with the typical?
3.
Food for thought (Optional): How long for the return of investment of upgrade if the added insulation cost $1.5/m
2
for ceiling, $15/m
2 for floor and $5/m for perimeter? Insulation and air exchange for Typical and Upgraded Structures:
Components
Typical
Upgraded
Wall, R15, total RSI (m
2
C/W)
3.07
3.07
Ceiling, with a total RSI (m
2
C/W)
3.65
7.2
Floor, particle board (with a Crawling Space at 10 C) (m
2
C/W)
0.776 (1” PE
insulation)
3.05 (insulation)
Perimeter insulation value, F (W/mC)
1.42
0.42
Windows
0.5
0.5
Doors
0.5
0.5
Air leakage (air change per hour)
1
0.5
Suggestion:
In calculating heat loss in a typical January: First, split the class into even number of teams. Half of team(s) works on the calculations for a Typical
house and the other half work on the Upgraded
house. First, each team works together to calculate perimeters, reasonable estimations are acceptable. Then among the team members, you may divide different tasks such as the following:
1.
Heat loss through walls, windows and doors, 2.
Heat loss through ceiling, floor and perimeters
Case Study: Improve Energy Efficiency for a Building
