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2 - Residential Construction Demonstration Project
sumed to be 0.33 Btu/hr SF F and 0.19 Btu/hr SF F
for solid core wood and insulated metal doors respec-
tively.
Glazing heat loss coefficients were extracted
from tested data available in the April 1987 Glazing
Test Report List (Hogan, 1987). Windows were
categorized by frame type, number of glazings, air
space width, coating type and filled gas type. Mean
heat loss coefficients were then calculated for each
category.
Component areas were examined for extreme
values. Any extreme values were checked against con-
struction blueprints and corrected if needed. A total of
seven corrections were made. Three basement
perimeter lengths and four glazing areas were incor-
rectly recorded and subsequently corrected. Com-
ponent areas and descriptions were extracted from
house plans and were verified through a series of con-
struction inspections. The methodology for collecting
component data (plans check and inspection process)
was similar to that used in the Residential Standards
Demonstration Program. This methodology was ex-
amined by WSEO and found to provide data which
were accurate and relatively free from errors
(Downey, 1988).
The overall conduction heat loss coefficient was
calculated with Equation 1.
Equation 1
UAc = UlAl + U2A2+ ... +Un An+FsPs
where:
UAc = the overall conduction UA in Btu/hr F
Un = the conduction heat loss coefficient for
component n in Btu/hr SF F
An = the area of component n in SF
Fs = the conduction heat loss coefficient for
slab in Btu/hr ft F
Ps = the perimeter of slab in lineal feet
Table 2 contains summary statistics of the conduc-
tive heat loss coefficient calculated for the 83 homes
examined in this analysis. Because different thermal
standards were required depending on the climate
zone where the structure was located, this table is
cross tabulated by the three climate zones. Figure 1
contains histograms of these data.
Table 2
Conduction Heat Loss Coefficients by Climate Zone
Climate
Zone
Mean
Standard
Median
n Frequency
1
318.6
290.6
111.0
41
2
299.7
297.8
73.4
22
3
271.5
255.9
75.8
20
Overall
302.2
283.8
95.3
83
Figure 1
Conduction Heat Loss by Climate Zone
(Btu/hr F)
Climate Zone 1
Climate Zone 2
0,4-
0.4-
0.2 -
J ■ °'z-
A,
c 0 -
■1 ■
JaL
0
1
6 200 400 600
§
i
■i
-o
U.
Climate Zone 3
0.4 J
0.2 -
0 ■
6 200 400 600
Convection Heat Losses
Convective losses are problematic for the simula-
tion software used in this analysis since they can not
be scheduled. Consequently, convective heat loss
must be condensed into an annual figure. Since all of
the test homes were equipped with mechanical heat
recovery ventilation (i.e., air-to-air heat exchangers),
convective heat loss is broken into two components:
mechanical and natural convective losses.
Mechanical Convection Losses
Each home in the program was equipped with
heat recovery ventilation (HRV) in the form of air-to-
air heat exchangers. Two types of air-to-air heat ex-
changers were used: plate exchangers with a core
constructed of plastic or metal and rotary wheel ex-
changers with the core consisting of a plastic wheel
rotating through the exhaust and intake air streams.
Heat exchanger air flow rates and electrical current
draw were measured during a single site survey. The
field technician attempted to balance supply and ex-
haust flows during the site survey. In some instances
the teclmician found it impossible to either measure
flows or balance the HRV unit due to poorly located
supply and exhaust vents, inaccessible flow dampers
or minimal flow capacity. Amp draw was recorded on
both high and low speeds if the heat exchanger unit
was equipped with a multiple or variable speed fan.
Mechanical convection losses were broken into
two separate components: effective convection losses
and unbalanced convection losses. The effective con-
vection loss coefficient was calculated with the fol-
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Downey, P. K. An Analysis of Predicted vs Monitored Space Heat Energy Use in 83 Homes, report, August 1, 1989; Olympia, Washington. (https://digital.library.unt.edu/ark:/67531/metadc1088109/m1/3/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.