Energy Consumption Comparison

The Canada Mortgage and Housing Corporation funded a study overseen by British Columbia bale builder Habib Gonzalez. Using energy consumption data from BC bale homes, they were compared to equivalent frame-walled homes via computer modeling. The following is an excerpt from that report:

While straw bale houses have a theoretical energy saving advantage over conventional houses, there is little good data on how they actually perform. This survey attempted to provide a first cut at comparing the space-heating energy consumption of straw bale homes and conventional homes.

Many straw bale homes are wholly or partially heated with wood-burning appliances. As wood consumption is difficult to measure accurately, the 11 houses in this survey used other fuel sources — gas, oil, electricity.

Most surveys of this type compare the measured houses to "control" houses of the same size, construction quality, occupancy, etc. Control houses for this study were too hard to locate, given the diversity of straw bale house design and the use of slab-on-grade foundations. Only 3 of the 11 study homes had full or walkout basements. Instead of actual control houses, the energy use of the conventional houses was modeled using HOT2000 software. The measured space-heating consumption of the 1.2 CMHC Energy straw bale houses was compared to the modeled energy consumption of conventional 2001 British Consumption Columbia (BC) building code houses of the same dimensions as the straw houses. ^ Comparison.

House

Actual energy use (GJ)

Model energy use (GJ)

% SB vs. Model area

Total inside floor (m2)

Year built

Bale wall type

Comments

1

115.6

100.9

12.7

133

1996

Post and beam

30% total wall area glazed; 78% single glazing

2

52.9

48.6

8.3

108

1998

Post and beam

20% total wall area glazed; 100% single glazing; hydronic heat

3

98.6

103.5

-4.7

156

1998

Post and beam

Hydronic heat; interior work unfinished

4

24.6

31.9

-22.8

48

1997

Load bearing

Cottage apartment and store room

5

96.7

129.7

-25.4

210

2000

Log post and beam

Two storey; hydronic heat; ventillation system not used

6

104.7

129.4

-19.1

189

2001

Modified post and beam

Hydronic heat

7

56.4

81.7

-31.0

218

1999

Modified post and beam

Water source heat pump

8

152.9

249.5

-38.7

267

1998

Timber frame

Two storey; basement apartment; B & B

9

142.1

186.3

-23.7

209

2000

Timber frame

Two storey; partial hydronic heat

10

105.7

137.4

-23.1

153

1999

Post and beam

HRV in use

11

73.4

95.7

-23.3

91

1998

Load bearing

Ventilation system not used

Mean

93.1

117.7

-21

162

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