The document summarizes research on highly insulating windows conducted by the Windows and Daylighting Research Group at Lawrence Berkeley National Laboratory. The group consists of 10-15 researchers dedicated to improving window performance. Key areas of focus include developing triple glazings, improving frame performance, and testing low-e storm windows as a cost-effective way to increase insulation. Preliminary estimates show low-e storm windows can reduce whole home heating energy use by 19-27% over a winter season with a payback period of 3-5 years depending on the home.

4. Heat Transfer in Windows Conduction Radiation Conduction Convection Low-e coatings Special gas fills Multiple cavities Low conductance spacers Better frames

6. Highly Insulating Windows - range Whole window U-factor 0.10 0.20 0.30 0.50 0.40 No heat transfer Standard double-pane windows Typical ENERGY STAR windows Highly insulating windows 0.35 = Northern ENERGY STAR benchmark

13. Cost effectiveness – Low-e Storms Total Window Cost Annual Energy Savings Simple Payback (yrs) House 2- Low-E $1,738 $490 3.5 House 3- Clear $1,344 $111 12.1 House 4- Clear $2,661 $317 8.4 House 5- Low-E $1,738 $341 5.1

14. Thank You Christian Kohler, CJKohler@lbl.gov Windows and Daylighting Research Group Lawrence Berkeley National Lab