Performance Testing
Verified by independent laboratory testing, Wojan windows and doors routinely exceed national performance standards set by the American Architectural Manufacturers Association (AAMA) in AAMA/NWWDA 101/I.S.2-1997 and AAMA 1503.1. These tests include precise measurements of structural strength, deformation under load, air infiltration, water leakage and thermal conductivity, based on simulations of actual wind, rain and temperature conditions the window is likely to experience when installed.
Energy Performance Basics
Heat moves out of a building in winter and must be replaced by burning costly furnace fuels. It moves into a building in summer and must be removed with air conditioning systems. The key to energy efficiency, then is to slow the rate at which the heat moves in or out. To do this, we have to pay attention to the three ways in which heat travels: conduction (the same mechanism that makes a metal spoon grow warm when placed in a cup of hot coffee), infiltration (air leaking in or out through tiny cracks in the wall or window framing system) and radiation (the heating effect of infra-red light rays).
Minimizing conduction through a window begins with multiple glazing. A hermetically sealed "dead" air space between the inner and outer glass panes slows heat conduction. The measurable result is a lower "U-value," stated as the number of British thermal units (Btu) traveling through a material every hour, per square foot of roof, wall or window area, for each degree of indoor vs. outdoor temperature difference. Dual glazing is two panes of glass with one dead air space between; triple glazing is three panes of glass with two dead air spaces.
The framing, too, must be constructed to form a barrier to conduction. Since some materials (like wood or certain plastics) do not conduct heat very well, we have to make sure there is a layer of such material between the inner and outer surfaces of the window frame - a thermal separation. In doing so, however, we have to be sure that the overall framing assembly is strong, durable and able to stand up to years of weathering and constant use.
An additional benefit to reducing heat conduction is that we also control condensation, the annoying tendency of a window to "fog up" or even frost over when it's cool outside and humid inside.
Minimizing air leakage means we need a "tight" framing design and careful use of good weatherstripping. Yet, we still have to make sure the window opens and closes smoothly and easily over years of service life.
The effects of radiation can be minimized by selecting different kinds of glass: "low-e," coated or reflective.
Taken together, careful selection of materials and design can produce a window that lowers the effects of conduction, infiltration and radiation for optimum energy efficiency, while being durable, long-lasting, and easy to operate and maintain. A prime example is Wojan's M-35 triple-glazed window.
M85 Series