Fenestration energy performance/User guide to CSA A440.2:19, Fenestration energy performance
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This is the seventh edition of CSA A440.2/CSA A440.3, Fenestration energy performance/User guide to CSA A440.2:19, Fenestration energy performance. It supersedes the previous editions published in 2014 and 2009 under the title Fenestration energy performance/User guide to CSA A440.2 and in 2004, 1998, 1993, and 1991 under the title Energy performance of windows and other fenestration systems (and associated user guides).
CSA A440.2 applies to the determination of energy performance properties for a variety of fenestration systems, including fixed windows, operable windows, sliding glass doors, hinged doors, skylights with flat glazings, and curtain walls. It includes the following energy performance properties, which are applicable to all building types (residential, commercial, and other):
a) overall coefficient of heat transfer (U-factor);
b) solar heat gain coefficient (SHGC); and
c) visible transmittance (VT).
These properties can be evaluated using either computer simulation or measurement.
In addition, CSA A440.2 provides a means for determining a comparative Energy Rating (ER) for fixed and operable windows, sliding doors, and hinged doors to be used in low-rise residential housing. The ER combines the U-factor, SHGC, and heat losses resulting from air leakage into a single rating that allows the energy performance of fixed and operable windows, sliding doors, and hinged doors to be compared over an average heating season. Assumptions have been made about the size of the fixed and operable windows, sliding doors, and hinged doors in order to develop the ER.
Annex B provides some information on how climate change can affect fenestration product design and application.
CSA A440.3, the user guide to CSA A440.2, has been prepared to explain the content and use of CSA A440.2. CSA A440.3 allows the knowledgeable user to develop specific energy performance properties that apply to fenestration systems of different sizes in specific geographic locations and orientations. CSA A440.3 is divided into three parts. In Section I, the energy performance of fenestration systems is discussed in general terms to provide an overview of the issues that should be considered in the selection of fenestration systems. Section I also explains some of the content of CSA A440.2. In Section II, technical explanations are provided for specific clauses of CSA A440.2. In Section III, the concepts of Specific Energy Rating (ERS) and Energy Rating for the cooling season (ERC) are explained for more advanced users.
CSA A440.2 is considered suitable for use for conformity assessment within the stated scope of the Standard.
CSA acknowledges that the development of these Standards was made possible, in part, by the financial support of Natural Resources Canada (NRCan).
CSA A440.2 has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group.
CSA A440.2:19 - Fenestration energy performance
This Standard applies to
a) fenestration systems covered by AAMA/WDMA/CSA 101/I.S.2/A440, including
i) vertically sliding windows;
ii) horizontally sliding windows;
iii) dual-action windows;
iv) casement windows, both fixed and operable;
v) projecting (awning/hopper) windows;
vi) fixed windows;
viii) transom windows;
ix) sliding doors;
x) side-hinged doors;
xi) dual-action side-hinged doors;
xii) architectural terrace doors;
xiii) unit skylights and roof windows;
xiv) greenhouse or garden windows; and
xv) tubular daylighting devices;
b) curtain walls; and
c) garage (vehicular access/rolling) doors.
Note: Unless otherwise specified, the term fenestration system is used to apply to all products listed in Clause 1.1.
This Standard specifies both measurement and calculation methods for establishing the following fenestration system properties for both residential and commercial applications:
a) overall coefficient of heat transfer (U-factor);
b) solar heat gain coefficient (SHGC); and
c) visible transmittance (VT).
This Standard also specifies measurement methods for establishing the Temperature Index (I) for fenestration systems for both residential and commercial applications.
Note: The fenestration properties established in accordance with this Standard are for specific indoor and outdoor conditions and will vary slightly under actual conditions. The values obtained by the methods specified in this Standard are considered to provide an acceptable basis for comparing performance in use.
This Standard specifies a method for determining an energy performance rating for vertical fenestration systems, under heating conditions, for use in low-rise residential applications. The Energy Rating (ER) includes factors for
a) solar heat gain;
b) heat loss by conduction, radiation, and convection; and
c) heat loss by air leakage.
The ER allows for a comparison of different fenestration systems on the basis of their effect on the energy supplied annually by the heating system. The ER calculation assumes vertical installation in low-rise residential buildings and is based on average conditions for
a) incident solar radiation on fenestration systems facing the four cardinal compass directions (north, east, south, and west); and
b) representative climate zones in Canada.
The ER should not be used to rate
a) any sloped glazing (residential or commercial); or
b) fenestration products that will be installed in commercial, industrial, or high-rise residential buildings.
CSA A440.3 is a user guide to this Standard. It provides guidance on determining
a) a specific Energy Rating (ERS) for particular locations, orientations, and vertical fenestration system sizes; and
b) an ER for residential cooling (ERC).
Annex B introduces the issue of climate change and its associated effects on fenestration in buildings. It is anticipated that fenestration designers will need to incorporate changes in climate loads resulting from climate change into fenestration product design. It is also anticipated that adjustments will need to be made to installation detailing. Annex B provides some information on these topics for consideration by building design professionals, authorities having jurisdiction, and installers. As information on climate change evolves, so too will the requirements of this Standard.
This Standard does not apply to
a) fixed glazing cast into precast concrete panels;
b) revolving doors;
c) doors intended for indoor use; and
d) storm doors.
Note: While these products have not been considered in the development of this Standard, simulation procedures given in the Standard may be used to evaluate the U-factor and the SHGC of these products.
This Standard does not address the retention of thermal and optical properties and airtightness by fenestration systems over time and under conditions of use.
In CSA Standards, shall is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; should is used to express a recommendation or that which is advised but not required; and may is used to express an option or that which is permissible within the limits of the standard.
Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.
Notes to tables and figures are considered part of the table or figure and may be written as requirements. Legends to equations and figures are considered requirements.
Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.
CSA A440.3:19 - User guide to CSA A440.2:19, Fenestration energy performance
Section I — Understanding fenestration energy performance
I.1 Purpose of CSA A440.2
CSA A440.2 was developed to allow comparison of the energy performance of different fenestration systems. In the past, the energy performance information provided by the manufacturer was often limited to the R-value or the U-factor for the centre-of-glass area. Because the effects of the frame and sash were not taken into account, the energy performance of the fenestration system was usually overrepresented. CSA A440.2 specifies a procedure for evaluating the energy performance parameters of the total fenestration system, including the glass, frame, and sash.
The properties that affect the energy performance of fenestration systems are
a) solar heat gain;
b) heat losses resulting from conduction, radiation, and convection; and
c) heat losses resulting from air leakage.
CSA A440.2 provides methods for determining the solar heat gain coefficient (SHGC) and the heat losses resulting from conduction, radiation, and convection (U-factor). The procedure for determining air leakage is specified in AAMA/WDMA/CSA 101/I.S.2/A440.
CSA A440.2 also provides a method for calculating the overall Energy Rating (ER) for a fenestration system to be used in a self-contained low-rise residential building by combining, into a single overall rating, the following three properties:
a) solar heat gain coefficient (SHGC);
b) overall coefficient of heat transfer (U-factor); and
c) air leakage.
The ER provides a means to compare the energy performance of fenestration systems used in low-rise residential buildings. However, because of the manner in which the ER is determined, there are limitations to its applicability. As explained in Clause I.6, ER is only applicable when comparing fenestration systems that are to be used in houses under heating conditions.
Section II — Commentary on selected clauses in CSA A440.2
Note: The clause numbers in this Section correspond to those in CSA A440.2, with the addition of the prefix II. Not all clauses in CSA A440.2 are explained in this Section.
The Energy Rating (ER) outlined in CSA A440.2 is not currently relevant for the energy use required for the mechanical cooling of residences. The effect of fenestration systems on energy requirements for the cooling of a residence can be calculated, and a simple comparative rating procedure is provided in Clause III.4. Similarly, the ER is not directly applicable to heating or cooling applications in multi-storey apartments or commercial building applications, where the relationship of heating and cooling loads to weather conditions is more complex.
The angle from the horizontal at which fenestration systems are installed has some effect on their thermal properties. CSA A440.2 specifies the determination of reference values for vertical installation, as most fenestration systems are installed vertically. The solar heat gain coefficient (SHGC) and the overall coefficient of heat transfer (U-factor) are generally appropriate for comparing the performance of fenestration systems installed at other angles. The ER, however, is based on incident solar radiation on vertical surfaces, and therefore does not apply directly to fenestration systems installed at other angles.
In developing the ER, the weather factors in 11 Canadian and two US cities with 4000 to 6200 heating degree-days were averaged, including incident solar radiation on fenestration systems facing the four cardinal compass directions, to produce a single set of average weather conditions. Rating values based on these average conditions, therefore, do not apply to any specific location. The ranking of the fenestration system, however, is roughly the same as that which would be obtained using local weather conditions.
The ranking of a fenestration system would likely be affected if an ER were computed for a specific orientation. A method for obtaining a Specific Energy Rating (ERS) for a specific location and orientation is provided in Clause III.3 for those who might wish to select or market fenestration systems on this basis. The ERS so obtained can be used to make a comparative estimate of the effect on annual heating energy requirements of alternative fenestration system installations.
The thermal properties of fenestration systems can change with time. There remains some uncertainty about the long-term service life of some sealed glazing systems. Air leakage rates for some air-sealing systems change more rapidly than those of others. Standard methods for establishing the ability of fenestration systems to retain certain thermal properties have not been established.
Section III — Determining specific fenestration system properties
III.1 Considerations for special conditions
The U-factor, solar heat gain coefficient, visible transmittance, and Energy Rating as determined in CSA A440.2 are for typical fenestration system sizes, average Canadian weather conditions, and average solar orientation. In some cases the building designer or purchaser will be interested in fenestration system properties for a specific condition rather than for the average condition specified in CSA A440.2.
III.1.2 Specific size
For large projects where most of the fenestration systems are the same size (e.g., office and apartment buildings), fenestration systems should be compared on the basis of the actual size, not the typical sizes used in CSA A440.2. For these cases, refer to Clause III.2.
III.1.3 Location and orientation
In some cases, a specific building location or fenestration system orientation can be important when evaluating the performance of fenestration systems. For example, when designing a passive solar house, the designer might be interested in comparing fenestration systems only on the basis of their ER when facing south, and not on an average of the four cardinal directions. A house designer might wish to select the optimum fenestration system for each elevation. For fenestration systems to be used in low-rise residential buildings, refer to Clause III.3. For other buildings, a detailed building energy analysis can be performed.
III.1.4 Heating/cooling options
For buildings and locations where cooling energy is a significant portion of the annual energy bill, a Cooling Energy Ratio (ERC) can be determined and included in the overall energy balance of the fenestration system. For these cases, refer to Clause III.4.