ABC's of window performance

Width of the overall glass unit is 1 3/8" top rating in energy efficiency.

The ABC’s of Window Performance

The performance of windows sold in Canada is defined in a Canadian Standards Association standard called CSA A440 (Windows). This standard sets the type of materials that are to be used in the manufacture of windows and some minimum material properties, such as thickness, hardness and durability. The A440 Standard also defines minimum performance levels for windows evaluated under a standardized set of conditions. The characteristics defined in the A440 Standard include:

  • Air tightness
  • Water resistance
  • Wind load resistance
  • Ease of operation
  • Resistance to forced entry
  • Condensation resistance
  • Screen strength

Air Leakage

Why is an air leakage standard so important?

The uncontrolled movement of air into or out of the house is a cost to the homeowner. For example, any cold outdoor air that leaks into (air infiltration) the home must be heated to room temperature to maintain the comfort of the occupants, so air infiltration is a heating cost. The same problem occurs in air-conditioned homes in summer, when warm outdoor air infiltrates, resulting in an additional cooling load.

When interior-conditioned air (either heated for winter or cooled for summer) leaks to the outside, the homeowner also pays the energy costs associated with the air leakage.

Windows are tested for air leakage using test pressures of 75Pa (1.57psf) across a window of a standard size. The average air leakage rate is calculated and compared to the maximum allowable leakage.

Windows are given one of the following air tightness performance ratings:

  • A1 (somewhat leaky)
  • A2 (slightly leaky)
  • A3 (not very leaky)

Window rating programs are intended to allow consumers to compare similar products, not to predict. The thinking is that, if one window has a better air tightness rating than another, it will have less air leakage when installed.

All our windows have A3 rating

Water Tightness

Windows may also allow water to leak into the house during rainstorms, leading to water damage of interior finishes and potential mold growth. Because of this, all windows sold in Canada should be evaluated for their ability to resist water leakage and for resistance to wind-driven rain. Water is continuously sprayed onto the outside of a standard-sized window under standard air pressure conditions.

The window is rated in accordance with the highest air-pressure level for which no water leakage occurs.

A B1 rating is assigned to a window that exhibits no water leakage at a relatively low air-pressure difference across the window. It is the lowest result.

Every rating number above B1 represents the highest air-pressure condition for which no water leakage occurs. For example, a window rated B5 that shows no water leakage at a test pressure differential of 500 Pascal (Pa) and a water spray rate of at least 204 L/m² per hour. The highest possible rating in the A440 Standard for resistance to wind-driven rain is B7.

As well as air leakage, the B rating does not necessarily indicate the performance of the product as installed. It should only be used to compare products. The B rating is a very important performance index in coastal climates, where wind-driven rain is relatively common. A window rated B2 would be the minimum advisable for low-rise houses in most of Canada.

Wind Load Resistance

Windows are also tested for their ability to resist wind pressures without deforming too much and without blowing out of their frames. Test windows are subjected to a large air-pressure difference to simulate hurricane-force winds (120 km/h and higher). The resulting deformation of the framing components is measured, with the window receiving a rating from C1 — deflection or blowout to C5 resistance to extremely high wind pressures without blowout or permanent deformation. Windows rated C5 are appropriate for some high-rise buildings, or for low-rise buildings in very windy climates. A window rated C2 is the minimum advisable for low-rise houses in most of Canada.

Ease of operation

Operable windows are tested to ensure that their operation is relatively smooth, with no jamming of operator mechanisms. The amount of force required to turn operator cranks or slide windows open and closed is measured in the test and cannot exceed set levels.

Resistance to forced entry

The CSA Window Standard includes a test method to determine a window’s resistance to forced entry.Entry should not be gained within the specified time limit.

Screen strength

Operable windows usually feature a screen over the open portion of the window to keep insects outside. It is important to note that the screen strength test is only designed to determine the ability of the screen to resist nominal loads. An insect screen is neither a fall prevention device nor an anti-theft feature - it is only intended to keep insects out.

Condensation resistance

The CSA procedure contains standardized test methods to evaluate a window’s tendency to allow condensation to form on the glazing or framing members under winter conditions.