Energy Efficient Design for a Connecticut Residential 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
ABSTRACT
Designing an energy efficient house is very complex. It can be designing electricity
sources, heating systems, cooling systems, and/or the compilation of building materials
and thicknesses used to build the house. This study did 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. The base house used in this study is the 2011 Connecticut Home Builders
Association house of the year located in Griswold, Connecticut. More specifically the
type and thickness of insulation and walls, type, number, and location of windows is
analyzed with finite element analysis to determine what the best combination is. HEED
software is then used to determine what the best overall design is coupled with the
smaller hand calculations.
ii
CONTENTS
ABSTRACT ...................................................................................................................... ii
CONTENTS ..................................................................................................................... iii
LIST OF TABLES ............................................................................................................ iv
LIST OF FIGURES ........................................................................................................... v
SYMBOLS/ABBREVIATIONS LIST ............................................................................. vi
INTRODUCTION ............................................................................................................. 1
METHODOLOGY ............................................................................................................ 2
RESULTS AND DISCUSSION ........................................................................................ 7
CONCLUSION.................................................................................................................. 7
REFERENCES .................................................................................................................. 9
APPENDIX...................................................................................................................... 10
iii
LIST OF TABLES
iv
LIST OF FIGURES
v
SYMBOLS/ABBREVIATIONS LIST
Symbol/Abbreviation
Meaning
Units
vi
INTRODUCTION
Designing an energy efficient house is very complex. It can be designing electricity
sources, heating systems, cooling systems, and/or the compilation of building materials
and thicknesses used to build the house. This study did 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. The base house used in this study is the 2011 Connecticut Home Builders
Association house of the year located in Griswold, Connecticut. More specifically the
type and thickness of insulation and walls, type, number, and location of windows is
analyzed with finite element analysis to determine what the best combination is. HEED
software is then used to determine what the best overall design is coupled with the
smaller hand calculations.
1
METHODOLOGY
Chapter 1: Walls
Since this house is located in Connecticut the lowest temperature seen 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, assume all of the following equations 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. 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
All thermal conductivity values in Table 1 and 2 are at approximately 300K.
Table 1: Heat Transfer Rate of Various Single Wall or Floor Materials
Material
Standard Brick
Thermal
Reference for
Conductivity
Thermal
(k) [W/mK]
Conductivity
0.72
(a)
Thickness
of
Material
(L) [m]
0.092
2
Reference
for
Thickness
(d)
Heat
Transfer
Rate (q)
[W]
6227
Concrete
Block 1.1
(a)
0.2
(a)
4376
Block 0.6
(a)
0.2
(a)
2387
(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 Walls (28mm)
0.12
(a)
0.028
(g)
3410
Log Walls (34mm)
0.12
(a)
0.034
(g)
2808
Log Walls (44mm)
0.12
(a)
0.044
(g)
2170
Log Walls (70mm)
0.12
(a)
0.070
(g)
1364
Log Walls (90mm)
0.12
(a)
0.090
(g)
1061
For example of a multi-material 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)
𝐿𝑔𝑦𝑝𝑠𝑢𝑚 =0.01m
𝐿ℎ𝑎𝑟𝑑𝑏𝑜𝑎𝑟𝑑 𝑠𝑖𝑑𝑖𝑛𝑔 =0.01m
𝐿𝑐𝑒𝑙𝑙𝑢𝑜𝑠𝑒 =0.01m
Using equation 3.15 from Reference (a):
Table 2: Heat Transfer Rate of Various Multi-Material Wall Materials
Material
Thermal
Reference for
Thickness
Reference
Heat
Conductivity
Thermal
of
for
Transfer
(k) [W/mK]
Conductivity
Material
Thickness
Rate (q)
3
(L) [m]
Standard Brick
Concrete
0.72
[W]
(a)
0.092
(d)
6227
Block 1.1
(a)
0.2
(a)
4376
Block 0.6
(a)
0.2
(a)
2387
(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 Walls (28mm)
0.12
(a)
0.028
(g)
3410
Log Walls (34mm)
0.12
(a)
0.034
(g)
2808
Log Walls (44mm)
0.12
(a)
0.044
(g)
2170
Log Walls (70mm)
0.12
(a)
0.070
(g)
1364
Log Walls (90mm)
0.12
(a)
0.090
(g)
1061
Chapter 2 Windows:
Using the same methodology and equations as Chapter 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 )
Equation 3.4 Reference (a)
𝑊
k=0.9𝑚×𝐾 from Table I of Reference (h)
L=0.003m per Reference (h)
𝑞𝑥 =
𝑊
0.9 [𝑚 × 𝐾 ] × 1.34709[𝑚2 ]
0.003[𝑚]
(293.15[𝐾] − 250.37[𝐾])
𝑞𝑥 = 17,289𝑊
4
Table 1: 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 =0.9𝑚×𝐾 from Table I of Reference (h)
𝑊
ℎ𝑎𝑟𝑔𝑜𝑛 =0.094𝑚×𝐾 from Table A.3 of Reference (a)
𝑊
ℎ𝑎𝑖𝑟 =0.23𝑚×𝐾 from Reference (f)
𝑊
ℎ𝑘𝑟𝑦𝑝𝑡𝑜𝑛 =0.23𝑚×𝐾 from Reference (f)
𝐿𝑔𝑙𝑎𝑠𝑠 =0.003m from Reference (h)
𝐿𝑔𝑎𝑝 𝑓𝑜𝑟 𝑔𝑎𝑠 𝑑𝑜𝑢𝑏𝑙𝑒 𝑝𝑎𝑛𝑒 =0.0194m
𝐿𝑔𝑎𝑝 𝑓𝑜𝑟 𝑔𝑎𝑠 𝑡𝑟𝑖𝑝𝑙𝑒 𝑝𝑎𝑛𝑒 =0.0082m
Using equation 3.15 from Reference (a):
5
Table 2: Heat Transfer Rate of Various Multi-Material 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]
Glass-argon-glass
0.72
(a)
0.092
(d)
6227
Glass-argon-glass-
1.1
(a)
0.2
(a)
4376
Glass-air-glass
0.6
(a)
0.2
(a)
2387
Glass-air-glass-air-
0.72
(a)
0.1016
(e)
argon-glass
glass
5639
Glass-krypton-glass
0.72
(a)
0.2032
(e)
Glass-krypton-glass-
0.72
(a)
0.254
(e)
krypton-glass
Glass-argon-glass-
2819
2256
0.72
(a)
0.2032
krypton-glass
(e)
2819
Windows triple pane windows with krypton as the gas are the most efficient but
depending on budget triple pane windows with argon is close to the efficiency with
much less cost.
Chapter 3 Doors:
Using the same methodology and equations as Chapter 1 for walls the heat transfer
rate through various doors can be calculated.
Chapter 4 Whole House Analysis:
6
RESULTS AND DISCUSSION
Hardboard siding with cellulose insulation and gypsum board on the inside is the
best wall material combination for an energy efficient house. The best type of window is
triple pane with krypton for efficiency but if cost is an issue a close second is triple pane
with argon. The solid wood door is the most efficient. The Connecticut home builders
association house of the year for 2011 was evaluated for its energy efficiency. It was
determined that better materials could have been used in some cases but would have
significantly raised the construction cost of the building. 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.
7
CONCLUSION
Hardboard siding with cellulose insulation and gypsum board on the inside is the
best wall material combination for an energy efficient house. The best type of window is
triple pane with krypton for efficiency but if cost is an issue a close second is triple pane
with argon. The solid wood door is the most efficient. The Connecticut home builders
association house of the year for 2011 was evaluated for its energy efficiency. It was
determined that better materials could have been used in some cases but would have
significantly raised the construction cost of the building. 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.
8
REFERENCES
a) Fundamentals of Heat and Mass Transfer 6th Edition; Incorpera, DeWirr, Bergman,
Lavine, 2007
b) http://www.weatherworksinc.com/winter-statistics-2013-2014
c) http://energy.gov/energysaver/articles/thermostats
d) http://www.archtoolbox.com/materials-systems/masonry/bricksizes.html
e) http://extension.missouri.edu/p/g1700
f) http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html
g) http://www.northwestlogcabins.co.uk/department/the_top_10_tips_on_choosing_a_c
abin/
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.
9
APPENDIX
10