November 2010 Chapter Event
Topic: How Glass & Window Options Affect Energy & Tour of Gilkey Window Company
When: Thursday Nov 11
Where: 3625 Hauck Road, Cincinnati OH 45241
California in the 1980s began limiting window solar heat gain based on estimated solar exposure, glass orientation and how much area. By mid-2000s, EnergyStar began restricting solar heat gain in qualifying windows in new homes but for all orientations. IRS began requiring EnergyStar ratings to qualify for energy tax credits. So most US window companies switched all windows to low-solar glass. The low-E coatings used to lower the solar gain produced higher R-values which was good, but the “solar heat gain coefficient” or SHGC was reduced to no more than 30% of what would pass through a window’s rough opening prior to window installation.
Consumer complaints, professional objections and articles argued that northern homes, usually with much higher heating than cooling costs, suffered higher heating bills using low-SHGC windows. So EnergyStar was revised to allow high SHGC windows in northern climates, including the Cincinnati area.
Most US window companies still only offer low-SHGC windows. A few companies including Gilkey offer a wide variety of glass so solar properties and R-values can be custom-fit to the application. In passive solar design, for example, higher SHGC windows can be used on the south to benefit from winter solar heat, lower SHGC windows on east and west to reduce summer solar heat. Lower SHGC can also be used to reduce AC demand and cost, even size of AC.
During lunch (provided by Gilkey), home energy consultant, passive solar home designer and adult-ed instructor John Robbins will compare winter and summer energy performance for windows with a variety of glass options, including several available from Gilkey. Comparisons will include conduction heat loss or gain plus solar gain. Window air infiltration rates for various window styles will also be compared.
Mike Gilkey, owner of Gilkey Windows, will answer additional questions and provide more information about his company and products, then lead a tour of his facility where both windows and glass are manufactured.