Window Performance Testing – A Basic Overview of NAFS

The North American Fenestration Standard/Specification, or NAFS, is the recognized standard for testing, rating and labelling of windows, doors and skylights for residential and commercial buildings in Canada.

The official name is AAMA/WDMA/CSA 101/I.S.2/A440, “NAFS – North American Fenestration Standard/Specification for Windows, Doors and Skylights” In Canada, an additional supplement is used to address specific Canadian performance conditions.

NAFS at a Glance

NAFS features a comprehensive method to classify the type, class and performance of windows and doors. Any product that has not been tested to NAFS does not meet the 2010 National Building Code of Canada, or provincial revisions.
Some of the main components of NAFS includes;

Performance Class
There are four performance classes: R, LC, CW and AW. Building type, load requirements and serviceability determine the Performance Class of the windows and doors and is set by the building architect, designer or specifier as;

Residential | R – Light duty, commonly used in single-family dwellings.
Light Commercial | LC – Medium duty, commonly used in low-rise and mid-rise multifamily dwellings.
Commercial Window | CW – Heavy duty, commonly used in low to mid-rise multifamily dwellings where limits on deflections are imposed and tougher environmental constraints exist.
Architectural Window | AW – Severe duty, used in high-rises or when extreme use of fenestration is expected.

Each Performance Class (R, LC, CW and AW) has minimum test sizes and minimum test pressures known as Gateway Requirements. Every product must be tested for each Gateway Requirement in order to qualify for a Performance Class.

Performance Grade
The Performance Grade is a single number that represents performance attributes for a number of different tests including design pressure, water penetration resistance, air leakage resistance, operating force, durability and life-cycle test. The Performance Grade is determined by;

Geographic location – Performance requirements are calculated to determine minimum design pressure, water penetration resistance and air leakage resistance based on the site’s geographical location

Building height – Determined from the top of the window or door above grade, with a minimum height of 10 metres.

Exposure condition – Determined as either;
Open terrain – level with only scattered buildings, trees or other obstructions, open water or shorelines.
Rough terrain – suburban, urban, or wooded terrain extending upwind from the building uninterrupted for at least 1km or 20 times the building height, whichever is greater

The NAFS Canadian Supplement includes a table that lists all major cities in Canada to help building professionals select the right Performance Grade. An easier method is to use the Fenestration Canada NAFS calculator – go to and click on the fenestration performance calculator.

Determining your Durabuilt window and door Performance Class

As a basic reference guide take a look at our Durabuilt NAFS Ratings info sheet that provides single unit window performance information. For more complete information based on your particular window and door configurations contact us to get a quote that contains specific NAFS performance information for every window and door, and an overall NAFS rating, for your project.

As part of NAFS requirements, the manufacturer is to affix both a removable NAFS rating label for building inspection purposes, and a permanent label to the product. This ensure your windows or doors comply with the NAFS requirements based on your site location.

To obtain more detailed information feel free to book a consultation or get a quote from a Durabuilt sales consultant or dealer partner.

Energy Code 9.36 – Where Do Windows and Doors Fit in?

Section 9.36 of the National Building Code details new requirements for housing and small buildings that is focused on improving the energy efficiency and reduction of greenhouse gas emissions. The code references six climate zones. The prairies have four of these zones. The specific weather location may be determined by referencing Appendix C of Division B in the Code or by consulting the local authority.

Compliance Map

Compliance Paths

Energy Code 9.36 includes three paths for compliance; Prescriptive, Trade-Off, and Performance Compliance. Select only one compliance path; multiple compliance paths are not permitted on a single building.

Prescriptive Path – The acceptable level of building energy efficiency by constructing the minimum requirements. This path involves following the prescriptive requirements of Subsection 9.36.2, 9.36.3 and 9.36.4 and is typically the simplest compliance path. It involves meeting all requirements in that part, but might not be appropriate for all buildings.

Prescriptive / Trade off Path – The acceptable level achieved by swapping of one or more building envelope thermal performance requirements, resulting in no worse thermal performance than if the affected assemblies met prescriptive requirements. If you need more flexibility in your design, a trade-off path allows you to trade elements within the above ground building envelope to demonstrate an equivalent level of performance without meeting every prescriptive requirement.

Performance Path – The acceptable level by employing a computer simulation software or calculations to compare a proposed design with a hypothetical reference building to show that the proposed design will use less energy over the course of an operational year. Once construction of the house is complete, a blower door test is performed and a Natural Resources Canada EnerGuide Rating System label is issued.

How do windows and door fit into Energy Code 9.36?

The Code allows windows and doors to qualify under two different energy performance rating methods: by the total unit U-value, and by Energy Rating (ER).

The U-value is the rate of heat loss through windows under standardized winter conditions and does not take solar heat gain into account. The ER is an overall energy balance rating that takes account of passive solar heat gain in addition to heat loss.

The ER is intended for use in homes with average window-to-wall ratios, and an approximately even distribution of windows on all sides of the home, and no external window shading devices. In such homes it has been shown to be more effective for selecting windows for lowest year round energy use. The ER is not recommended for homes with higher window-to-wall ratios (above 30%), or with windows facing primarily one or two orientations. Under these conditions occupants could face heating discomfort, or fail to obtain the benefits of moderate passive solar heat gain.

For homes with high window to wall ratios, or windows primarily facing one or two orientations, windows should be selected on the basis of U-value, and with consideration to reduce occupant discomfort from excessive solar heat gain by use of external shading or glass with lower solar heat gain.

There is some flexibility that allows trade-offs, in which a better performing window or glass door can compensate for a worse-performing product having the same orientation. It also has a performance path, and it is possible that homes designed under the performance path could accommodate several products that have worse than prescriptive ratings. The code also relaxes the U-value requirement for one door in a home. The intent is to allow decorative or heritage style entrance doors to be used which might be constructed of materials that cannot achieve the prescriptive U-values.

This table provides the maximum U-value and minimum Energy Rating for your building zone.


Determining your Durabuilt window and door Performance Class

As a basic reference guide, take a look at our Durabuilt Energy Performance info sheet that provides single unit window performance information. For more complete information based on your particular window and door configurations contact us to get a quote that contains specific energy performance information for every window and door.

The code requires products to be labeled with energy performance ratings. This ensure your windows or doors comply with the energy requirements based on your site location.

To obtain more detailed information feel free to book a consultation or get a quote from a Durabuilt sales consultant or dealer partner.

Performance Rating

If you are ever wondering about the structural and thermal performance of your windows, these guides are here to help you ensure you are getting the most out of your windows and sliding patio doors.


Same Day Stain

When it comes to staining or refinishing your wood grain entry door, Durabuilt highly recommends the Same Day Stain Door Finishing Kit designed exclusively for fiberglass doors. The Same Day Stain kit provides you with a long lasting finish that will bring out the authentic grain pattern in your fiberglass door. The finish will resist fading, bleaching and yellowing, and will complete the look of your door system. You are also able to layer the stain in order to achieve the desired look for your door. This kit includes step-by-step, easy to follow instructions, as well as a finishing DVD. The Same Day Stain Door Finishing Kit also has faster drying time than traditional oil and gel based stains.

My Home Is South Facing. How Can I Make It Cooler?

Durabuilt offers Low E glass solutions for year round comfort and savings. Low E glass can act as a gateway for natural heat to come in during cooler winter months and as a shield to block heat waves in the summer. Ask your Sales Consultant for a solution that is right for your home.

Will Replacing The Windows And Doors Increase The Value Of My Home?

Yes – one of Durabuilt’s major door manufacturing partners has found that the replacement of your home’s entrance adds real value in addition to a fresh new look. Therma-Tru’s National Home Valuation Study™ offers proof that a more attractive front entrance can considerably increase the perceived market value of a home.

The commissioned study asked more than 2,400 consumers to estimate home prices based on each home’s exterior appearance. The study found that an enhanced entryway can add as much as $24,000 to a home’s perceived value. The added value was as much as five times the cost of the entry system. The second instalment of Home Valuation Study™ found that moderately priced homes benefit from entryway updates just as much as their upscale counterparts. The new study shows that an upgraded entryway can increase the perceived value of an average home by $7,720, or 4.1%.

Replacing all your windows can provide the greatest visual impact on both the inside and outside of your home. When you think about the architectural features of your home, in most cases windows account for about 50% of the curb appeal.

What Is The Difference Between Full Frame And Box Frame Renovations?

In some situations where it is important for the customer to preserve historic characteristics of the home, we may be able to leave existing wood frames and simply replace it with a window insert. This depends on the state of existing windows and frames. Nine times out of ten, our recommendation is a full frame renovation where you remove any rotted wood and poorly performing components to replace the entire window system with a new high performance window.

Can I Replace My Windows and Doors in the Winter?

Absolutely – if you’re experiencing heat loss and cold drafts, please do not put your comfort on hold any longer! Winter installations are a common practice and our teams typically work most days (as long as conditions are safe). Excessive wind chills do play a factor in this, and if they become too uncomfortable or dangerous for our teams we will simply reschedule your install for the next available day.

Are your installers sub-contractors?

Durabuilt install crews are owner-operators that run their own crews, but it is a requirement that they exclusively work with Durabuilt Windows & Doors and our products. Extensive training and product knowledge is a requirement and expectation from members of the install team. Take comfort in knowing that the average installer for Durabuilt has been with us for 3+ years and has have a background in window and door renovations. Because we have a very low turnover rate, our installers take pride in their work and are passionate about Durabuilt and our customers.


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