Design Ratings

The following ratings have a great affect on specific performances of window and door products. Understanding these ratings will help you better identify the specific needs you want to address and optimize with new windows and doors for you home.

U-factor – Indicates the products rate of heat loss for each degree of difference between one side and the other. This is its insulating value and is tested to account for both flow of heat through frame material and glass. The lower ther U-factor the lower the transmission of heat flow. Energy Star rated products have a U-factor of .35 or lower.

Design and structural test pressures- These two aspects of a product account for a specific products ability to withstand wind and rain - respectively. Resistance to water leakage is a correlation of pressure from wind loads when combined with rain. This is known as the structural test pressure. Design pressure is a products ability to withstand wind loads. Testing for water resistance is accomplished by a simulation of 8” of rainfall per hour under a static pressure simulation of wind load. Since the structural test pressure rating ( resistance to water), is a function of the DP (design pressure) = 1.5 x DP, you can simply conclude that the greater the Design Pressure rating the better.

Solar Heat Gain Coefficient ( SGHC) – Represents the efficiency of a products ability to block radiant energy. The value given indicates the percentage of solar radiation that passes through the product. Glass types used have the most affect on solar heat gain. Solar heat gain is generally less desirable in the summer months of the Pacific Northwest. It is also responsible for color fading of materials. South and West elevations in the Northwest are most subjected to the affects of solar heat gain. Shading from trees and overhangs give shelter from its affects, however, homes with lots of glass on these elevations could benefit from the use of SunCoat Max ( HYPERLINK http://www.milgard.com/gettingstarted/energy-efficiency-suncoat.asp www.milgard.com/gettingstarted/energy-efficiency-suncoat.asp )

Sound Transmission Class ( STC ) rating – Addressing sound attenuation from the outdoors is affected by glass thickness and air space between the glass. Using offset glass thickness in double paned insulated glass units (IGU) can interrupt the sound wave and decrease noise. Installing windows or doors with laminated glass is better at decreasing sound. Better solutions for sound control http://www.milgard.com/products/sound-control-windows/ www.milgard.com/products/sound-control-windows/