We stepped deep into window research, but we still have to make a decision on what windows to use. Because they will be a very big investment, any type of rebates, financial incentives or tax credits will influence this decision.
Federal Tax Credits for Consumer Energy Efficiency
… or, more commonly known as the $1,500 tax credit that expires on December 31, 2010.
The total of $1,500 can be applied across a range of energy efficient upgrades, such as furnaces, water heaters, insulation, doors and – yes – windows. This made us very happy as we were convinced that we could claim the $1,500 in a heartbeat on our new windows … until I looked at the fine print.
Qualifying windows must have a U-value of 0.30 [LINK] and Solar Heat Gain Coefficient (SHGC) of 0.30 (see also ‘The world of windows’ post).
This is a federal tax credit, available nationwide, from Alaska to Florida and Southern California to Maine, intended to stimulate the economy and improve the energy efficiency of existing homes.
Now, wait a minute, how can that energy efficiency thing work with this one requirement (U-value of 0.30 and SHGC of 0.30) across a number of different climate zones? Down south, a very low SHGC is probably of interest while the U-value would not matter that greatly. It would be the reverse up north, where the insulation value (U-value) counts and passive solar heat gain (high SHGC) may actually be desirable.
Take our house in Chicago. I ran a quick window analysis for the 1st and 2nd floor with the RESFEN model. The only variable in the analysis was the SHGC.
- Scenario 1: SHGC north 0.25, east 0.25, south 0.25, west 0.25
- Scenario 2: SHGC north 0.51, east 0.51, south 0.51, west 0.25
Allowing for passive solar heat gain (high SHGC) through the windows on the east and south side could bring the annual heating load down as much as 10%, even though our building has a north-south orientation. The more a building has access to passive solar, i.e. lots of windows in the south elevation, the greater the potential to lower the annual heating load.
That said, any window slated for passive solar heat gain (high SHGC) would need proper summer shading or otherwise the winter heating savings may be lost in summer cooling needs.
Even the Energy Star program recognized the importance of the different climate zones and has structured the qualifying criteria for windows, doors and skylights accordingly.
Why the federal tax credit for consumer energy efficiency did not take the same approach is a mystery to me. I guess the intent is good but the execution is poor.
As for the $1,500 – we may not claim it on the windows alone, because we would like to benefit from passive solar heat gain. But we have the boiler, insulation and doors that will help us to claim the full amount.
Tags: cost, energy, insulation, window