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Note: The annual energy performance figures shown here were generated
with regression expressions provided by Lawrence Berkeley National
Laboratory (windows.lbl.gov/EStar2008). Results assume a typical (new
construction: 2250 sq ft / existing construction: 2150 sq ft) house with
15% window-to-floor area. The windows are equally distributed on all
four sides and include typical shading (interior shades, overhangs,
trees, and neighboring buildings). U-factor and SHGC are for the total
window including frame. The costs shown here are annual costs for space
heating and space cooling only and thus will be less than total utility
bills. Costs for lights, appliances, hot water, cooking, and other uses
are not included in these figures. The mechanical system uses a gas
furnace for heating and air conditioning for cooling. Natural gas prices
used are projections of the average natural gas price for the heating
seasons of 2010-2020 in real 2009 dollars. Projections are based on
state-specific natural gas retail price data by the Energy Information
Administration (EIA) for the heating seasons of 2006-08 and are adjusted
based on EIA projections of national natural gas price trends for
2010-2020. Electricity prices used are projections of the average
electricity price for the cooling seasons of 2010-2020 in real 2009
dollars. Projections are based on state-specific electricity retail
price data by the Energy Information Administration (EIA) for the
cooling seasons of 2006-08 and are adjusted based on EIA projections of
national electricity price trends for 2010-2020
(www.eia.doe.gov).
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