Assessing Window Materials for Energy Ratings

This paper assesses window materials for their suitability and energy ratings. It explores the importance of window design optimization and material selection for energy efficiency. The properties of different window materials are discussed, and alternative options for improving energy performance are suggested.

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ASSESS WINDOW MATERIALS FOR SUITABILITY OF ENERGY RATING
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Introduction
Research shows that windows contribute approximately 38% of heating energy use and
29% of cooling energy use (Brownlee & Wright, 2015). Hence, window design optimization and
material selection for thermal performance is important for occupants in achieving low energy
consumption and increasing the overall performance of the building. To achieve energy
efficiency in windows, manufactures have come up with ranking mechanism that label window
products on the basis of their energy efficiency through the Energy Rating System (ERS).
Energy rating system is an assessment method of comparing the energy performance of
windows. Its main purpose is to rank windows according to their energy performance in order to
enable customers to relate with the windows using particular numbers that is relative to their
energy efficiency. The energy rating formula is derived from the balance between heat loss
through conduction and air infiltration or leakage and heat gain via the window. It is
recommended to label each window with a separate energy rating (ER) for cooling and heating
conditions since heat gain and heat loss parameters have opposite effects on cooling and heating
energy. A number of countries have different variation of energy ratings on windows due to
different climatic condition throughout the year. An international standard method was
established by ISO to determine a similar method for calculating the energy rating (ER) for
windows in ISO 18292 (Sorgato, et al., 2016). Over the years, some challenges experienced in
energy performance of fenestrations have raised concern in the industry that could compromise
the validity of the energy ratings as a method of ranking the energy performance of windows in a
predominantly hot climate. This issues mainly deal with selection of a reference building, impact
of thermal comfort and the advancement in glazing technology.

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Therefore, this paper will assess window materials of a builder in relation to their
suitability and energy ratings by comparing the builder’s choice of selection of the window
materials and comparing them with the energy rating report. The essay will go ahead to give
their material properties considering the thermal and durability property of each material. I will
then conclude by giving an alternative for window frame material will improve the energy
performance of the building.
On technical grounds, it was reported that the window energy rating scheme was
established in the year 1995 in cooperation with the University of New South Wales. The scheme
founders were Dr Peter Lyons and PC Thomas (Sorgato, et al., 2016). This enabled windows to
be labelled and rated for energy impact on the overall performance of the house in any climate of
Australia. Therefore, window makers must comply with the energy rating standards as stipulated
by the Australian Fenestration Rating Council in order to participate in Windows Energy Rating
System (WERS)
Suitability of materials
The builder’s choice of material was very simple. He opted to go with aluminum frames
with 3mm single glazing layer of glass material labelled window 1. Aluminum is a strong but
inexpensive material for home building given the advantage of its durability and the fact that it
can be painted (Kibert, 2016). Aluminum may not be the choice in regard to heat transfer
mechanisms since it is a good conductor of heat which translates to more heat gains and heat loss
through conduction process. The single pane glass has a low rating in terms of energy efficiency
since it provides only a thin barrier to heat transfer from daylight hence exhibiting very little

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insulating value due to a high U- factor. This will definitely add up the hefty costs of heating and
air-conditioning. According to the star ratings table for generic windows created for the Window
Energy Rating Scheme (WERS) of Australia, it shows that window number 1, which is 3mm
single glazing clear glass with aluminum frame has zero cooling star and 1-star for heating
performance. Therefore, this means that when Post Occupancy Evaluation and thermal comfort
of the house is carried out, it will exhibit poor performance in terms of energy performance level
of the building.
Figure 1: single pane
Source: (Kibert, 2016)
Properties of materials
Windows are defined by sticker ratings that gives them their performance scores to
determine the best choice for building a home, if sustainability and thermal comfort is key to the
design implementation.

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Figure 2: The label for Window Energy Rating Scheme in Australia
Source: (Sorgato, et al., 2016)
Some of the factors that define the energy performance of windows include U-factor, solar heat
gain coefficient (SHGC), visibility transmittance (VT), and Air leakage (AL).

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The builders choice of single glazing with aluminum frame window had a label rating of
1.29 U-factor which is higher than the energy performance label of National Fenestration Rating
Council ( NFRC) which gives a U–factor ratings of between 0.20 -1.20 (Sorgato, et al., 2016).
This description states the lower the U-value, the better the insulating value of the window in
resistance to heat transfer.
In terms of the heat gain which is referred to as Solar Heat Gain Coefficient (SHGC), the
builders window choice indicated window performance rating of 0.73 which is within the
required range of 0 and 1 with the best performance being labelled as 0.32 according to the
National Fenestration Rating Council (NFRC) (Sorgato, et al., 2016).This is because, the lower
the SHGC, the less solar heat is transmitted into the building or the house.
Visible transmittance of the window glass was labelled 0.69 which is an optical property
required to be within 0 and 1 (Sorgato, et al., 2016). It indicates that the higher the visibility
transmittance, the more light rays are transmitted through the window hence the window
property meets the energy requirement standards.
The air leakage of the window is measured in cubic feet per minute. The window was
labelled 0.21cfm/sq ft which is a good rating since this property states that the lower the number/
air leakage, the better the seal hence less air will be allowed to pass through the cracks
(Kotireddy, et al., 2018).

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Figure 3: The NFRC label for rating the energy performance of fenestration products in the
USA.
Source: (Sorgato, et al., 2016)
Materials that are structurally adequate
All windows are required to meet certain requirements before being released to the
builder for purposes of construction. This include being rated water tightness, airtightness,
resistance to forced entry, wind load strength, insect screen strength, and ease of operation.
Short and long-term degradation is considered in relation to building life span
Since the building is considered to have a life span of 80 years, the use of aluminum window
frame is the best choice since it is durable and able to withstand external forces considering it is a
strong material. However, when it comes to energy efficiency, it will mean high costs of bills

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throughout the life span due to its heating ability and can also nullify the efficiency of glass
materials installed.
Alternative materials
Use double glazed pane since it has a dramatic increase in the energy efficiency of the window.
The two panes can be filled with air between them which acts as insulating property (Kibert,
2016). Therefore, it means the thicker the air space, the more its insulation property.
Figure 4: Double pane
Source: (Kibert, 2016)
Fiberglass can also be used as frame option replacing aluminum. It is also a strong and durable
material that is resilient to weather with little maintenance and insulation property which will
help to reduce the U- factor of the window hence reducing heat gains and heat loss transfers
(Kwok & Grondzik, 2018). Moreover, it is aesthetically pleasing both on the inside and outside.
Its only disadvantage is that it is expensive.

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Site safety
Site safety is a major priority when avoiding work place injury cases. When simple
precautionary measures and simple procedures are followed, accidents can be avoided or
prevented during the building stage. It is therefore the responsibilities of both the employer and
employee to work together to comply with the safety guideline stipulated in order to remain safe
at any construction site. Construction site safety can be enforced if proper storage and
transportation of material procedures; materials testing procedures and safety procedures on-site
are followed.
With regard to construction, different types of materials have different storage
requirements depending on whether they are durable, toxic or non-durable. It is important for the
site space to be carefully planned to avoid unnecessary congestion. Construction materials
should be stored in a secure area away from site operations. The area of storage should be near
the area the material is used to minimize costs and time used to transport them (Li and Yi 2015,
p.34). Additionally, construction materials should be stored in a safe area for protection against
vandalism and theft. When storing construction materials, items should be stacked properly to
prevent accidental fall. The types of materials being stored also need to be taken into account so
that specific precautions are taken when handling them. Toxic materials also need to be
separated from others during storage to avoid reaction. During transportation of materials, the
items should be properly stacked on trucks to prevent fall off that may cause injuries. Secondly,
paths should be cleared of obstruction and other tripping hazards.
Apart from storing and safe transport of materials procedures, on-site materials testing
procedures should also be kept into consideration. Firstly, materials to be tested should be
sampled from the rest and transported to a designated area where they will be tested. Secondly,

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appropriate equipment for the test should be used to conduct the test. After conducting the test,
the materials used should be disposed safely or kept in a safe place for reference. During
construction, it is also important to observe safety procedure when handling items. When people
observe safety procedures during construction, accidents are minimized greatly. Safety at the
construction site can only be achieved when employees are given proper training (Dong et
al.2012, p. 312). Training is a fundamental part that ensures workplace safety. Training reminds
workers on construction site safety procedures which further minimize fatalities. Secondly,
workers should be supplied with personal protective equipment and clothing. The personal
protective equipment prevents them from injuries. It is also vital for workers to ensure proper
material storage and handling onsite. This can minimize breakage and further prevent potential
accidents. The top management, workers and supervisors should work hand in hand to promote
and enforce good practice to ensure that everyone is safe.
Notably, a Material Safety Data Sheet (MSDS) is a crucial document in a construction
site. MSDS document entails information on potential hazards and further prescribes how people
can work with the chemical product safely (Li & Yi, 2015). The document contains information
on storage, use and handling of material in case of an emergency. During construction, MSDS
can be useful when dealing with bricks and cement (Li & Yi, 2015). The MSDS gives a
guideline on how to package, deliver, handle and store bricks and cement to avoid breakage.
Bricks are needed to be stored on a flat surface and avoid direct contact with the surface. This
will facilitate proper handling when needed.

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References
Brownlee, A.E. and Wright, J.A., 2015. Constrained, mixed-integer and multi-objective
optimization of building designs by NSGA-II with fitness approximation. Applied Soft
Computing, 33, pp.114-126.
Dong, Xiuwen S.,Wang, Xuanwen and Daw, C., 2012. Fatal falls among older construction
worker. Human Factors. 54 (3): 303–315.
Kibert, C.J., 2016. Sustainable construction: green building design and delivery. John Wiley &
Sons.
Kotireddy, R., Hoes, P.J. and Hensen, J.L., 2018. Integrating robustness indicators into multi-
objective optimization to find robust optimal low-energy building designs. Journal of Building
Performance Simulation, pp.1-20.
Kwok, A.G. and Grondzik, W., 2018. The green studio handbook: Environmental strategies for
schematic design. Routledge.
Li, R.and Yi M., 2015. Rita Yi Man Li, Construction Safety and Waste Management, Springer
2015. Risk Engineering. doi:10.1007/978-3-319-12430-8. ISBN 978-3-319-12429-2.
Sorgato, M.J., Melo, A.P. and Lamberts, R., 2016. The effect of window opening ventilation
control on residential building energy consumption. Energy and Buildings, 133, pp.1-13.

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