Adding Exterior Treatments to Windows
Use the “upgrade windows” recommendation to add and model solar screens / exterior window treatments.
If you are not upgrading the windows, but only adding exterior treatments, be sure to choose No Improvement for the "Windows Improved?" question.
Then, be sure to set the appropriate window area that is going to receive the Exterior Treatments as described in this article.
Then select the appropriate Exterior Treatments that are applied to each orientation as in the example below. The the system will calculate the savings and add the approximate estimated cost to the total window costs.
It's important to realize that the solar gain in the home is cut down by the exterior treatment, which reduces the cooling load in summer, but also increases the heat load in the winter if the treatment is year around. In some climates you will see a greater savings if the treatments are applied as "summer only"
Reference:
Solar Heat Gain Coefficient (SHGC) measures how much heat from the sun is blocked. SHGC is expressed as a number between 0 and 1. The lower the SHGC, the more a product is blocking solar heat gain. Blocking solar heat gain is particularly important during the summer cooling season in hot climates.
The SHGC figures below are an example of Phifer screens, please check with your supplier for their specs.
Phifer Suntex Solar Screens
Suntex 80 - SHGC = .15 to .07
Suntex 90 - SHGC = .08 to .07
