Energy Efficient Design for a Connecticut Home
by
Michael J. Gasper
An Engineering Project Submitted to the Graduate Faculty of Rensselaer Polytechnic
Institute in Fulfillment of the Requirements of the degree of
MASTER OF ENGINEERING IN MECHANICAL ENGINEERING
Approved:
_
Ernesto Gutierrez-Miravete, Project Adviser
Rensselaer Polytechnic Institute
Hartford, Connecticut
December, 2014
© Copyright 2014
by
Michael Gasper
All Rights Reserved
ii
CONTENTS
CONTENTS ..................................................................................................................... iii
LIST OF TABLES ............................................................................................................ iv
LIST OF FIGURES ........................................................................................................... v
DEFINITIONS ................................................................................................................. vi
SYMBOLS/ABBREVIATIONS LIST ............................................................................ vii
KEYWORDS .................................................................................................................. viii
ACKNOWLEDGMENT .................................................................................................. ix
ABSTRACT ...................................................................................................................... x
1.- INTRODUCTION ........................................................................................................ 1
2.- METHODOLOGY ....................................................................................................... 2
2.1-Walls ...................................................................................................................... 2
2.2-Roof ..................................................................................................................... 10
2.4-Windows .............................................................................................................. 11
2.5-Doors ................................................................................................................... 15
2.6-Whole House Analysis ........................................................................................ 17
3.- RESULTS AND DISCUSSION ................................................................................ 19
4.- CONCLUSION .......................................................................................................... 20
REFERENCES ................................................................................................................ 21
APPENDIX A .................................................................................................................. 23
iii
LIST OF TABLES
Table 1: Heat Transfer Rate of Various Single Wall Materials......................................... 4
Table 2: Heat Transfer Rate of Various Insulating Materials in Multi-Material Walls .... 6
Table 3: Heat Transfer Rate of Various Interior Materials in Multi-Material Walls ........ 8
Table 4: Heat Transfer Rate of the Most Efficient Multi-Material Walls ......................... 9
Table 5: Heat Transfer Rate of Various Ground/Foundation Materials .......................... 11
Table 6: Heat Transfer Rate of Various Single Pane Window Materials ........................ 12
Table 7: Heat Transfer Rate of Various Multi-Material Window Materials ................... 14
Table 8: Heat Transfer Rate of Various Single Door Materials ...................................... 15
Table 9: Heat Transfer Rate of Various Multi-Material Door Materials......................... 17
Table 10: Whole House Analysis .................................................................................... 18
iv
LIST OF FIGURES
Figure 1: Heat Transfer Through a Single Wall ................................................................ 3
Figure 2: Heat Transfer Through a Multi-Material Wall (Reference (q)) ......................... 5
Figure 3: A Triple Pane Window per Reference (s) ........................................................ 13
Figure 4: Cross Section of a Garage/House Door per Reference (t) ............................... 16
Figure 5: Page 1 of BAEC 2011 House of the Year Brochure ........................................ 23
Figure 6: Page 2 of BAEC 2011 House of the Year Brochure ........................................ 24
Figure 7: Page 3 of BAEC 2011 House of the Year Brochure ........................................ 25
Figure 8: Page 4 of BAEC 2011 House of the Year Brochure ........................................ 26
v
DEFINITIONS
Word
Definition
Reference for
Definition
Heat Transfer
“Heat transfer describes the exchange of thermal energy,
(i)
between physical systems depending on
thetemperature and pressure, by dissipating heat. The
fundamental modes of heat transfer
are conduction ordiffusion, convection and radiation.”
Thermal
Conductivity
“In physics, thermal conductivity (often denoted k, λ, or κ)
(j)
is the property of a material to conduct heat. It is
evaluated primarily in terms of Fourier's Law for heat
conduction.
Heat transfer occurs at a higher rate across materials of
high thermal conductivity than across materials of low
thermal conductivity. Correspondingly materials of high
thermal conductivity are widely used in heat
sink applications and materials of low thermal
conductivity are used as thermal insulation. Thermal
conductivity of materials is temperature dependent.”
Conduction
“On a microscopic scale, heat conduction occurs as hot,
rapidly moving or vibrating atoms and molecules interact
with neighboring atoms and molecules, transferring some
of their energy (heat) to these neighboring particles. In
other words, heat is transferred by conduction when
adjacent atoms vibrate against one another, or as
electrons move from one atom to another. Conduction is
the most significant means of heat transfer within a solid
or between solid objects in thermal contact. Fluids—
especially gases—are less conductive.Thermal contact
conductance is the study of heat conduction” between
solid bodies in contact.[9]
vi
(i)
SYMBOLS/ABBREVIATIONS LIST
Symbol/Abbreviation
Meaning
Units
T
Temperature
°F, °C, or K
A
Area
in2, ft2, mm2, or m2
L
Length
in, ft, mm, or m
k or h
Thermal Conductivity
W/mK
q
Heat Transfer Rate
W
vii
KEYWORDS
Energy, Efficiency, Design, Home, House, Heat Transfer, Window, Door, Roof, Wall,
Conduction, Thermal Conductivity
viii
ACKNOWLEDGMENT
I would like to thank my parents and friends for their support whenever I encountered
hardships throughout the completion of this project.
ix
ABSTRACT
This study did an analysis of the compilation of building materials and thicknesses used
to build a house since they significantly impact wasted energy on heating and cooling in
the summer and winter months respectively. More specifically the type and thickness of
insulation and walls, type of windows, and doors are analyzed to determine what the best
combination is. The whole house analysis shows how efficient the BAEC 2011 House of
the Year really is. In some cases better materials for heat transfer could have been used
but they were most likely not cost effective at the time. For any future building projects
this analysis should be coupled with a cost versus benefit evaluation.
x
1. - INTRODUCTION
Designing an energy efficient house is a complex task. It can involve designing
electricity sources, heating systems, cooling systems, and/or the compilation of building
materials and thicknesses used to build the house. This study carried out an analysis of
the compilation of building materials and thicknesses used to build the house since they
significantly impact wasted energy on heating and cooling in the summer and winter
months respectively. From this study, the materials with the best thermal properties can
be selected. However, the materials with the lowest heat transfer rate may not always be
the best cost effective materials for building. To determine the cost/benefit this analysis
should be coupled with the cost these materials in the area that you are building at that
time and the electricity rates and projections for the next few years ahead. The house
investigated in this study is the 2011 Connecticut Home Builders Association house of
the year located in Griswold, Connecticut. This house was designed to be an energy
efficient house. Extreme summer outside temperatures only approximately 40 degrees
from a normal inside temperature whereas extreme winter outside temperatures are
approximately 77 degrees from a normal inside temperature. The materials below were
analyzed in extreme winter temperatures since this condition creates the largest
temperature gradient and therefore the largest heat transfer rate. There are many different
styles of buildings which would also greatly affect the heat transfer rate for the entire
house on top of what is being used for materials. For instance a conditioned attic will act
differently than an unconditioned attic especially if there are heat and or cooling ducts
located in them spaces since they tend to result in a large loss.
1
2. - METHODOLOGY
2.1-Walls
As stated in the introduction the heat transfer analysis was done for a winter
condition due to a larger thermal gradient than in the summer. Since the house analyzed
in section 2.6 is located in Connecticut the exterior temperature used for calculations
was the lowest temperature seen in the state took in Hartford in the 2013-2014 winter
season was -9˚F on January 4, 2014 per Reference (b). For an energy saving house, a
good temperature to keep your thermostat at in the winter is 68˚F per Reference (c).
Therefore, all of the following calculations are done with an external temperature of -9˚F
(250.37K) and an internal temperature of 68˚F (293.15K). We will assume the heat
transfer through a single 25x8 foot wall (A=18.6m2) with no windows for all of the walls
below. Thickness is based on material and construction and will vary. To determine
which materials are the best to use for construction, the one-dimensional steady-state
conduction equation 3.4 from Reference (a) can be applied to each material to obtain the
heat transfer rate.
For example of a single material wall with standard brick:
𝑞𝑥 =
𝑘𝐴
𝐿
(𝑇𝑠,1 − 𝑇𝑠,2 )
Equation 3.4 Reference (a)
𝑊
k=0.72𝑚×𝐾 from Table A.3 of Reference (a)
L=3.625 inches (0.092m) per Reference (d)
𝑞𝑥 =
𝑊
0.72 [𝑚 × 𝐾 ] × 18.6[𝑚2 ]
0.092[𝑚]
(293.15[𝐾] − 250.37[𝐾])
𝑞𝑥 = 6227𝑊
Figure 1 from Reference (p) shows schematically the wall with temperature
difference and how to reduce heat transfer.
2
Figure 1: Heat Transfer Through a Single Wall
All thermal conductivity values in Table 1 are at approximately 300K. Table 1 could
be older/or poorly designed buildings that only have a single building material. This
table can be coupled with Table 2 to determine the best insulation/exterior material.
3
Table 1: Heat Transfer Rate of Various Single Wall Materials
Material
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
Heat
Transfer
Rate (q)
[W]
Standard Brick
0.72
(a)
0.092
(d)
6227
Doubled-up Brick
0.72
(a)
0.184
(d)
3114
Block 1.1
(a)
0.2
(a)
4376
Block 0.6
(a)
0.2
(a)
2387
Concrete
(Hallow)
Concrete
(Filled)
Cement (4 inch)
0.72
(a)
0.1016
(e)
5639
Cement (8 inch)
0.72
(a)
0.2032
(e)
2819
Cement (10 inch)
0.72
(a)
0.254
(e)
2256
Cement (12 inch)
0.72
(a)
0.3048
(e)
1880
Log (28mm)
0.12
(a)
0.028
(g)
3410
Log (34mm)
0.12
(a)
0.034
(g)
2808
Log (44mm)
0.12
(a)
0.044
(g)
2170
Log (70mm)
0.12
(a)
0.070
(g)
1364
Log (90mm)
0.12
(a)
0.090
(g)
1061
Similar to above with the same temperature difference and wall area the heat
transfer rate through multiple materials can be calculated. For example of a multimaterial wall with gypsum board, hardboard siding, and cellulose:
𝑊
𝑘𝑔𝑦𝑝𝑠𝑢𝑚 =0.17𝑚×𝐾 from Table A.3 of Reference (a)
𝑊
𝑘ℎ𝑎𝑟𝑑𝑏𝑜𝑎𝑟𝑑 𝑠𝑖𝑑𝑖𝑛𝑔 =0.094𝑚×𝐾 from Table A.3 of Reference (a)
𝑊
𝑘𝑐𝑒𝑙𝑙𝑢𝑜𝑠𝑒 =0.23𝑚×𝐾 from Reference (f)
𝐿1/2′′ 𝑔𝑦𝑝𝑠𝑢𝑚 =0.0127m
𝐿1/2′′ 𝑝𝑙𝑦𝑤𝑜𝑜𝑑 =0.0127m
4
𝐿8′′ 𝑐𝑒𝑙𝑙𝑢𝑜𝑠𝑒 =0.2032m
Using a modified equation 3.15 from Reference (a):
𝑞𝑥 =
(𝑇∞,1 − 𝑇∞,3 )
𝐿
𝐿
𝐿
[( 𝐴 ) + ( 𝐵 ) + ( 𝐶 )]
𝑘𝐴 𝐴
𝑘𝐵 𝐴
𝑘𝐶 𝐴
𝑞𝑥
=
(293.15[𝐾] − 250.37[𝐾])
0.0127𝑚
0.0127𝑚
0.2032
[(
)+(
)+(
)]
𝑊
𝑊
𝑊
0.17 [𝑚 × 𝐾 ] × 18.6[𝑚2 ]
0.12 [𝑚 × 𝐾 ] × 18.6[𝑚2 ]
0.23 [𝑚 × 𝐾 ] × 18.6[𝑚2 ]
𝑞𝑥 = 748𝑊
Figure 2: Heat Transfer Through a Multi-Material Wall (Reference (q))
All thermal conductivity values in Table 2 are at approximately 300K. The multimaterial walls in Table 2 have a ½’’ plywood board on the outside, varying insulation as
shown in table 2 in the middle, and ½’’ gypsum board on the inside. The insulation
thickness differences shown such as 4’’, 6’’, and 8’’ represent common walls made of
2’’ x 4’’, 2’’ x 6’’, and staggered 2’’ x 4’’ or 2’’ x 8’’ studs for wall framing.
5
Table 2: Heat Transfer Rate of Various Insulating Materials in Multi-Material Walls
Material
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
Heat
Transfer
Rate (q)
[W]
8’’Celluose
0.23
(f)
0.2032
(-)
748
4’’Celluose
0.23
(f)
0.1016
(-)
1279
6’’Celluose
0.23
(f)
0.1524
(-)
944
3-1/2’’Fiberglass-
0.046
(a)
0.0889
(-)
377
0.038
(a)
0.0889
(-)
316
0.035
(a)
0.0889
(-)
292
0.046
(a)
0.1651
(-)
211
0.038
(a)
0.1651
(-)
176
0.035
(a)
0.1651
(-)
162
0.046
(a)
0.2159
(-)
163
0.038
(a)
0.2159
(-)
136
0.035
(a)
0.2159
(-)
125
0.043
(a)
0.1016
(-)
313
0.043
(a)
0.1524
(-)
214
16kg/m^3
3-1/2’’Fiberglass28kg/m^3
3-1/2’’Fiberglass40kg/m^3
6-1/2’’Fiberglass16kg/m^3
6-1/2’’Fiberglass28kg/m^3
6-1/2’’Fiberglass40kg/m^3
8-1/2’’Fiberglass16kg/m^3
8-1/2’’Fiberglass28kg/m^3
8-1/2’’Fiberglass40kg/m^3
4’’Fiberglass/blown16kg/m^3
6’’Fiberglass/blown16kg/m^3
6
8’’Fiberglass/blown-
0.043
(a)
0.2032
(-)
162
4’’Urethane Two Part 0.026
(a)
0.1016
(-)
195
(a)
0.1524
(-)
132
(a)
0.2032
(-)
100
(a)
0.1016
(-)
475
(a)
0.1524
(-)
329
(a)
0.2032
(-)
251
(a)
0.1016
(-)
444
(a)
0.1524
(-)
306
(a)
0.2032
(-)
234
0.046
(a)
0.1016
(-)
333
0.046
(a)
0.1524
(-)
228
0.046
(a)
0.2032
(-)
173
16kg/m^3
Foam
6’’Urethane Two Part 0.026
Foam
8’’Urethane Two Part 0.026
Foam
4’’Vermiculite Flakes 0.068
80kg/m^3
6’’Vermiculite Flakes 0.068
80kg/m^3
8’’Vermiculite Flakes 0.068
80kg/m^3
4’’Vermiculite Flakes 0.063
160kg/m^3
6’’Vermiculite Flakes 0.063
160kg/m^3
8’’Vermiculite Flakes 0.063
160kg/m^3
4’’Mineral Wool
Granules with
Asbestos
6’’Mineral Wool
Granules with
Asbestos
8’’Mineral Wool
Granules with
Asbestos
7
Using the information learned from Table 2 above that the 8’’ cellulose and ½’’ plywood
were used along with an altered interior material.
Table 3: Heat Transfer Rate of Various Interior Materials in Multi-Material Walls
Material
1’’Gypsum Plaster,
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
0.22
(a)
0.0254
(n)
½’’Plywood
0.12
(a)
0.0127
(-)
8’’Celluose
0.23
(a)
0.2032
(-)
1’’Gypsum Plaster,
0.22
(a)
0.0254
(n)
½’’Plywood
0.12
(a)
0.0127
(-)
8’’Celluose
0.23
(a)
0.2032
(-)
1’’Gypsum Plaster,
0.22
(a)
0.0254
(n)
½’’Plywood
0.12
(a)
0.0127
(-)
8’’Celluose
0.23
(a)
0.2032
(-)
11mm Hardboard
0.094
(a)
0.011
(-)
Heat
Transfer
Rate (q)
[W]
720
Sand Aggregate
729
Vermiculite
Aggregate
651
Sand Aggregate
Siding
Table 3 shows that altering the interior material and even adding a 4th material to the
exterior does not make a significant difference in the heat transfer rate. Using the above
information from Tables 1, 2, and 3, Table 4 was created to show the best possible
combinations for multi-material walls.
8
Table 4: Heat Transfer Rate of the Most Efficient Multi-Material Walls
Material
1’’Gypsum Plaster,
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
0.22
(a)
0.0254
(n)
90mm Log
0.12
(a)
0.09
(-)
8’’Urethane Two Part
0.026
(a)
0.2032
(-)
½’’Gypsum
0.17
(a)
0.0127
(-)
90mm Log
0.12
(a)
0.09
(-)
8’’Urethane Two Part
0.026
(a)
0.2032
(-)
1/4’’Gypsum
0.17
(a)
0.0127
(-)
90mm Log
0.12
(a)
0.09
(-)
8’’Urethane Two Part
0.026
(a)
0.2032
(-)
Heat
Transfer
Rate (q)
[W]
92
Sand Aggregate
Foam
92
Foam
92
Foam
Table 4 shows the same heat transfer rate with different interior materials. It proves with
different thicknesses and or materials that there is not a significant difference on the
interior of the house. Table 4 also show that there is significantly less heat transfer with a
thick log exterior and 8’’ of urethane two part foam for insulation. This insulation can be
thicker and or the wall also, but 92W is a very low heat transfer rate.
For additional information on heat transfer of different wood materials Reference (l)
goes further in depth. Four of the five most common insulating materials per Reference
(m) are shown in Table 2 above as options. The fifth material is polystyrene which is a
foam board. This can be added to any wall for additional heat transfer and moisture
prevention.
9
2.2-Roof
There are 2 main designs for ceilings/roofs for insulating. The two options are
conditioned and unconditioned attics as described in Reference (o). Both of these behave
similarly for heat transfer. For the purposes of this paper and general house building the
ceiling would consist of gypsum board, insulation, and a plywood layer similarly to the
walls section above. Example if the roof is made of ½’’ gypsum board, ½’’ plywood,
and 8’’ cellulose insulation for a 25’ x 8’ section it would have a heat transfer rate of
748W as shown in Table 2 above. Assuming no flow, but heat rises so the flow would
make the roof loose more heat than the walls. The best insulating materials from Table 2
can be used for this for the best results.
2.3-Ground
The ground/foundation can be considered to be cement. We are assuming no
raised structure and that there is space below ground such as a basement. Since this is
below ground the exterior will be approximately a constant temperature of 50˚F
(283.15K) below the frost line per Reference (r). Minimal heat transfer can be assumed
through the ground/foundation since there is minimal thermal difference to normal
interior temperature. If a whole house calculation is being performed this value can be
specifically calculated using the same information as the cement wall in Table 1 and
changing the temperatures. Refer to Figure 1 above for a visual.
For example of a single material foundation with 4 inches of cement:
𝑞𝑥 =
𝑘𝐴
𝐿
(𝑇𝑠,1 − 𝑇𝑠,2 )
Equation 3.4 Reference (a)
𝑊
k=0.72𝑚×𝐾 from Table A.3 of Reference (a)
L=4 inches (0.1016m) per Reference (e)
𝑞𝑥 =
𝑊
0.72 [𝑚 × 𝐾 ] × 18.6[𝑚2 ]
0.092[𝑚]
(293.15[𝐾] − 283.15[𝐾])
𝑞𝑥 = 1318𝑊
10
All thermal conductivity values in Table 5 are at approximately 300K. Table 5 is
conservative opposite of the roof section since heat rises and would not push to transfer
out through the ground as much.
Table 5: Heat Transfer Rate of Various Ground/Foundation Materials
Material
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
Heat
Transfer
Rate (q)
[W]
Cement (4 inch)
0.72
(a)
0.1016
(e)
1318
Cement (8 inch)
0.72
(a)
0.2032
(e)
659
Cement (10 inch)
0.72
(a)
0.2540
(e)
527
Cement (12 inch)
0.72
(a)
0.3048
(e)
439
These calculations assume only a cement floor, adding flooring would further
decrease the heat transfer rate. Rising the structure above ground such as if it were a
beach house would increase the heat transfer rate and it could be assumed similar to a
wall as shown in section 2.1.
2.4-Windows
Using the same methodology and equations as Chapter 2.1 for walls the heat
transfer rate through various windows can be calculated. For the purposes of showing
which windows are the most efficient we will assume the window size is 58 x 36 inches
(A=1.34709m2). Windows come in many various sizes and if a whole house analysis is
performed the specific sizes of each window should be used for accuracy.
For example of a single material window with glass:
𝑞𝑥 =
𝑘𝐴
𝐿
(𝑇𝑠,1 − 𝑇𝑠,2 )
𝑊
k=0.9𝑚×𝐾 from Table I of Reference (h)
L=0.003m per Reference (h)
11
Equation 3.4 Reference (a)
𝑞𝑥 =
𝑊
0.9 [𝑚 × 𝐾 ] × 1.34709[𝑚2 ]
0.003[𝑚]
(293.15[𝐾] − 250.37[𝐾])
𝑞𝑥 = 17,289𝑊
Single panes consist of 1 material such as shown in Figure 1 in section 2.1.
Table 6: Heat Transfer Rate of Various Single Pane Window Materials
Material
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
Heat
Transfer
Rate (q)
[W]
Glass
0.9
(h)
0.003
(h)
17289
Polyester film
0.14
(h)
0.0001
(h)
80680
Acrylic or
0.19
(h)
0.006
(h)
1825
polycarbonate sheet
Glass is the material that is usually used for most window applications. Acrylic or
polycarbonate are used for applications such as storm windows. Most windows in newer
houses are a composite of double or triple pane with gas separating the panes. For ease
of calculation we are going to assume each composite window has a total thickness of
one inch (0.0254m) and each glass pane has a thickness of 3mm (0.003m). These are the
average window and glass thicknesses but glass and windows can be thicker or thinner
than these in specific applications.
For example of a multi-material with glass-argon-glass:
𝑊
𝑘𝑔𝑙𝑎𝑠𝑠 =0.9
𝑚×𝐾
from Table I of Reference (h)
𝑊
ℎ𝑎𝑟𝑔𝑜𝑛 =0.016𝑚×𝐾 from Reference (f)
𝑊
ℎ𝑎𝑖𝑟 =0.024𝑚×𝐾 from Reference (f)
𝑊
ℎ𝑘𝑟𝑦𝑝𝑡𝑜𝑛 =0.0088𝑚×𝐾 from Reference (f)
𝐿𝑔𝑙𝑎𝑠𝑠 =0.003m from Reference (h)
12
𝐿𝑔𝑎𝑝 𝑓𝑜𝑟 𝑔𝑎𝑠 𝑑𝑜𝑢𝑏𝑙𝑒 𝑝𝑎𝑛𝑒 =0.0194m
𝐿𝑔𝑎𝑝 𝑓𝑜𝑟 𝑔𝑎𝑠 𝑡𝑟𝑖𝑝𝑙𝑒 𝑝𝑎𝑛𝑒 =0.0082m
Using a modified equation 3.15 from Reference (a):
𝑞𝑥 =
(𝑇∞,1 − 𝑇∞,3 )
𝐿
𝐿
𝐿
[( 𝐴 ) + ( 𝐵 ) + ( 𝐶 )]
𝑘𝐴 𝐴
ℎ𝐵 𝐴
𝑘𝐶 𝐴
𝑞𝑥
=
(293.15[𝐾] − 250.37[𝐾])
0.003𝑚
0.0194𝑚
0.003
[(
)+(
)+(
)]
𝑊
𝑊
𝑊
2
2
2
0.9 [𝑚 × 𝐾 ] × 1.35[𝑚 ]
0.016 [𝑚 × 𝐾 ] × 1.35[𝑚 ]
0.9 [𝑚 × 𝐾 ] × 1.35[𝑚 ]
𝑞𝑥 = 653𝑊
Figure 3 shows an example of a triple pane window. A double pane window is missing
the middle piece of glass which changes the reflective properties.
Figure 3: A Triple Pane Window per Reference (s)
13
Table 7: Heat Transfer Rate of Various Multi-Material Window Materials
Material
Glass
Argon
Glass
Glass
Argon
Glass
Argon
Glass
Glass
Air
Glass
Glass
Air
Glass
Air
Glass
Glass
Krypton
Glass
Glass
Krypton
Glass
Krypton
Glass
Glass
Argon
Glass
Krypton
Glass
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
0.9
0.016
0.9
0.9
0.016
0.9
0.016
0.9
0.9
0.024
0.9
0.9
0.024
0.9
0.024
0.9
0.9
0.0088
0.9
0.9
0.0088
0.9
0.0088
0.9
0.9
0.016
0.9
0.0088
0.9
(h)
(f)
(h)
(h)
(f)
(h)
(f)
(h)
(h)
(f)
(h)
(h)
(f)
(h)
(f)
(h)
(h)
(f)
(h)
(h)
(f)
(h)
(f)
(h)
(h)
(f)
(h)
(f)
(h)
Thickness
of
Material
(L) [m]
0.003
0.0194
0.003
0.003
0.0082
0.003
0.0082
0.003
0.003
0.0194
0.003
0.003
0.0082
0.003
0.0082
0.003
0.003
0.0194
0.003
0.003
0.0082
0.003
0.0082
0.003
0.003
0.0082
0.003
0.0082
0.003
Reference
for
Thickness
(h)
(-)
(h)
(h)
(-)
(h)
(-)
(h)
(h)
(-)
(h)
(h)
(-)
(h)
(-)
(h)
(h)
(-)
(h)
(h)
(-)
(h)
(-)
(h)
(h)
(-)
(h)
(-)
(h)
Heat
Transfer
Rate (q)
[W]
653
769
976
1148
360
425
547
Double pane windows with krypton as the gas are the most efficient in terms of heat
transfer. With windows the reflective properties as described further in Reference (h)
should also be considered but they are not in this study.
14
2.5-Doors
Using the same methodology and equations as for walls the heat transfer rate
through various doors can be calculated. The door options below are for ones without a
glass window. Ones with a glass window will be less efficient. If you are designing a
house and using a door with a window, the window area should be considered in the
calculation. Assume all of the doors below are 1.75 inches or 0.04445 meters thick with
an area of 1.85806m2 (36 x 80 inches).
For example of a single material door with wood (oak or maple):
𝑞𝑥 =
𝑘𝐴
𝐿
(𝑇𝑠,1 − 𝑇𝑠,2 )
Equation 3.4 Reference (a)
𝑊
k=0.16𝑚×𝐾 from Table A.3 of Reference (a)
𝑞𝑥 =
𝑊
0.16 [𝑚 × 𝐾 ] × 1.85806[𝑚2 ]
0.04445[𝑚]
(293.15[𝐾] − 250.37[𝐾])
𝑞𝑥 = 286𝑊
For the case of a single material Figure 1 above can be used for a visual.
All thermal conductivity values in Table 8 are at approximately 300K.
Table 8: Heat Transfer Rate of Various Single Door Materials
Material
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
Heat
Transfer
Rate (q)
[W]
Hardwood
0.16
(a)
0.04445
(-)
286
Polyvinyl Chloride
0.19
(f)
0.04445
(-)
340
Fiberglass
0.04
(f)
0.04445
(-)
72
15
Similar to above with the same temperature difference, door thickness, and door
area the heat transfer rate through multiple materials can be calculated. For example of a
multi-material door with steel, polyurethane, and steel:
𝑊
𝑘𝑠𝑡𝑒𝑒𝑙 =16𝑚×𝐾 from Table A.3 of Reference (a)
𝑊
𝑘𝑝𝑜𝑙𝑦𝑢𝑟𝑒𝑡ℎ𝑎𝑛𝑒 =0.03𝑚×𝐾 from Reference (f)
𝐿 1 ′′
32
𝑓𝑖𝑏𝑒𝑟𝑔𝑙𝑎𝑠𝑠,𝑎𝑙𝑢𝑚𝑖𝑛𝑢𝑚,𝑜𝑟 𝑠𝑡𝑒𝑒𝑙
=0.00079375m
𝐿𝑝𝑜𝑙𝑦𝑢𝑟𝑒ℎ𝑎𝑛𝑒 =0.042863m
Using a modified equation 3.15 from Reference (a):
𝑞𝑥 =
(𝑇∞,1 − 𝑇∞,3 )
𝐿
𝐿
𝐿
[( 𝐴 ) + ( 𝐵 ) + ( 𝐶 )]
𝑘𝐴 𝐴
𝑘𝐵 𝐴
𝑘𝐶 𝐴
𝑞𝑥
=
(293.15[𝐾] − 250.37[𝐾])
0.00079375𝑚
0.042863𝑚
0.00079375𝑚
[(
)+(
)+(
)]
𝑊
𝑊
𝑊
2
2
2
16 [𝑚 × 𝐾 ] × 1.858[𝑚 ]
0.03 [𝑚 × 𝐾 ] × 1.858[𝑚 ]
16 [𝑚 × 𝐾 ] × 1.858[𝑚 ]
𝑞𝑥 = 56𝑊
Figure 4: Cross Section of a Garage/House Door per Reference (t)
All thermal conductivity values in Table 9 are at approximately 300K.
16
Table 9: Heat Transfer Rate of Various Multi-Material Door Materials
Material
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
Thickness
of
Material
(L) [m]
Reference
for
Thickness
Steel
16
(a)
0.0008
(-)
Polyurethane
0.03
(f)
0.042863
(-)
Steel
16
(a)
0.0008
(-)
Fiberglass
0.04
(a)
0.0008
(-)
Polyurethane
0.03
(f)
0.042863
(-)
Fiberglass
0.04
(a)
0.0008
(-)
Aluminum
205
(f)
0.0008
(-)
Polyurethane
0.03
(f)
0.042863
(-)
Aluminum
205
(f)
0.0008
(-)
Heat
Transfer
Rate (q)
[W]
56
54
56
Door internal material us usually polyurethane which from Table 2 was shown to be
the best insulating material. Varying the thing exterior and interior material does not
greatly affect the heat transfer.
2.6-Whole House Analysis
The above information for a single wall, door, and window can be combined to
analyze an entire house as shown in this section. The information for dimensions and
insulation in the 2011 Home Builders Association of Eastern Connecticut House is
located in the brochure in Appendix A. Pictures of the house are also located in
Appendix A. The ceiling has the same thickness gypsum board, cellulose insulation, and
plywood that the walls have so for calculation purposes we can assume a box. The
length of the house is approximately 50 feet and the width is approximately 25 feet. This
house is a split level with a basement under half and an attached garage under the other,
therefore, we can assume this is 2 stories or approximately 16 feet high. Both of the
shorter sides have no windows and are approximately 25 feet by 16 feet so the value in
section 2.1 can be multiplied by 4 to get the losses on those walls. The front has 5
17
windows, a garage door (make equal to 4 doors) and a door and the back has 6 windows
and a sliding door (make equal to approximately 2 windows) which subtract area off of
the two 50 foot by 16 foot areas. The area from the windows and doors will not be
subtracted for conservatism. This is summarized in Table 10 below:
Table 10: Whole House Analysis
Heat Transfer Rate
Wall
(q) [W]
West Side (25’x16’)
1496
East Side (25’x16’)
1496
North Side (50’x16’)
2992
South Side (50’x16’)
2992
Ground - 12’’ Cement
(50’x25’)
2634
Roof (50’x25’)
4488
13 - Windows
9997
5 - Doors
280
Total
26375
The total 26,375W is approximately 90,000 BTU/hour. To be able to keep up with
the cold outdoor temperatures in your entire house your heating system would need to be
larger than 90,000 BTU/hour.
18
3. - RESULTS AND DISCUSSION
From the materials analyzed for the walls it was determined that log walls are the best
external material and foam two part urethane mixture is the best insulating material. Two
common interior materials of plaster and gypsum board make a negligible difference to
the heat transfer rate so either could be chosen. For each of these materials common
thicknesses were chosen but thicker walls and or materials would further decrease the
heat transfer rate. For the windows it was determined that a double pane krypton filled
window is the most efficient for heat transfer rate. The triple pane windows also have a
good heat transfer rate but would be better than the double pane in windy areas. It was
determined that the doors with the best heat transfer rate had a polyurethane core with
either an aluminum, fiberglass, or steel sheet on the exterior. The whole house analysis
shows how efficient the BAEC 2011 House of the Year really is. In some cases better
materials for heat transfer could have been used but they were most likely not cost
effective at the time. Since building material cost varies greatly based on location and
year the buyer/builder would have to determine energy efficiency versus cost at the time
they are considering the project.
19
4. - CONCLUSION
Building materials are constantly changing. New materials should be added to this
analysis at the time of use. Costs of each material and estimated future heat and or
cooling costs should be coupled with this to get a complete analysis of what to use.
Electricity, oil, and wood are the 3 most common heating and cooling sources. These
sources vary greatly with cost based on area and day you look at them and a prediction
would have to be made. The buyer/builder would have to determine energy efficiency
versus cost at the time they are considering the project.
20
REFERENCES
a) Fundamentals of Heat and Mass Transfer 6th Edition; Incorpera, DeWirr, Bergman,
Lavine, 2007
b) Weather Works, 2014, from http://www.weatherworksinc.com/winter-statistics2013-2014, date last accessed 12/8/2014.
c) Energy.gov, 2014, from http://energy.gov/energysaver/articles/thermostats, date last
accessed 12/8/2014.
d) Architects Technical Reference, from http://www.archtoolbox.com/materialssystems/masonry/bricksizes.html, date last accessed 12/8/2014.
e) University of Missouri Extension, from http://extension.missouri.edu/p/g1700, date
last accessed 12/8/2014.
f) The Engineering Toolbox, from http://www.engineeringtoolbox.com/thermalconductivity-d_429.html, date last accessed 12/8/2014.
g) Northwest Log Cabins,
http://www.northwestlogcabins.co.uk/department/the_top_10_tips_on_choosing_a_c
abin/, date last accessed 12/8/2014
h) Calculating Heat Transfer Through Windows; Energy Research, Vol 6, 341-349
(1982); Michael Rubin; Lawrence Berkeley Laboratory, University of California,
Berkeley, California 94720, U.S.A.
i) Wikipedia, Heat Transfer, http://en.wikipedia.org/wiki/Heat_transfer, date last
accessed 12/8/2014.
j) Wikipedia, Thermal Conductivity,
http://en.wikipedia.org/wiki/Thermal_conductivity, date last accessed 12/8/2014.
k) Johns Manville, http://www.jm.com/content/dam/jm/global/en/buildinginsulation/Files/BI%20Data%20Sheets/Resi%20and%20Commercial/BID0016%20Kraft-Faced%20Fiber%20Glass%20Data%20Sheet-Acrylic%20Binder.pdf,
date last accessed 12/8/2014.
l) Oak Ridge National Laboratory,
http://www.fpl.fs.fed.us/documnts/pdf1988/tenwo88a.pdf, date last accessed
12/8/2014.
21
m) Thermaxx Jackets, http://www.thermaxxjackets.com/5-most-common-thermalinsulation-materials/, date last accessed 12/8/2014.
n) Craftsman Blog, http://thecraftsmanblog.com/5-worst-mistakes-of-historichomeowners-part-4-plaster/, date last accessed 12/8/2014.
o) Green Building Advisor.com, http://www.greenbuildingadvisor.com/blogs/dept/qaspotlight/determining-best-attic-option, date last accessed 12/8/2014.
p) Air-Conditioner-Selection.com, http://www.air-conditioner-selection.com/radiationconduction-convection.html, date last accessed 12/8/2014.
q) Dr. Nor Mariah’s Homepage,
http://eng.upm.edu.my/~mariah/KMP3203/module3.htm, date last accessed
12/8/2014.
r) Innovate Us, http://www.innovateus.net/earth-matters/what-frost-line, date last
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s) Green Glaze Co., http://www.greenglaze.co.uk/wp-content/uploads/2013/04/tripleglazed-windows.png, date last accessed 12/8/2014.
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accessed 12/8/2014.
22
APPENDIX A
This appendix is a brochure from the Builders Association of Eastern Connecticut on
their green 2011 house of the year. This brochure gives details about the construction
and dimensions of the house that are in section 2.6 of this paper.
Figure 5: Page 1 of BAEC 2011 House of the Year Brochure
23
Figure 6: Page 2 of BAEC 2011 House of the Year Brochure
24
Figure 7: Page 3 of BAEC 2011 House of the Year Brochure
25
Figure 8: Page 4 of BAEC 2011 House of the Year Brochure
26