LIT 1: Hi-R Windows

Windows account for about 5% of all U.S. energy consumption or 12% of building energy use. For 30+ years, the Berkeley Lab Windows and Envelope Group has provided research and technical support enabling advancement of energy performance in the window industry. From 1980 to 2000, the combination of public/private investment in R&D, codes, rating and labeling resulted in deep market penetration of dual pane low-E/argon gas filled windows (~R3), now >90% of all sales. However, for more than a decade, progress toward further energy efficiency improvements in the window market has largely stagnated, with more insulating triple glazing still comprising less than 2% of all window sales in 2016.

​Berkeley Lab work has demonstrated there is the technical potential to nearly halve the energy consumption of the prevailing U.S. window stock, if it is all replaced with triple glazed windows (~R5-7). These high performance windows would save 7-16% of the energy used in a home built with today's typical code compliant construction. The largest savings are achieved in heating dominated climates, with more modest savings in cooling dominated climates.

Contributing to the performance stagnation, manufacturers have been reluctant to redesign their entire sash/frame inventory to accommodate the thicker, heavier insulating glass units (IGUs) needed for conventional triple pane windows. Slimmer and lighter vacuum glazing, that could achieve these R-values, is not yet market ready.

However, Berkeley Lab has identified the potential to transform window markets to the R5-7 insulating levels by introducing a novel packaging of existing technology elements, implemented as a "drop-in replacement" for current IGUs. By working with supply chain partners (thin glass, low-E, new spacers, Krypton gas fill) and leading window manufacturers, this technology can be practically deployed, allowing market pull partners (codes, utilities, etc.) to incentivize higher performance without imposing undue cost burdens.

Berkeley Lab is engaged in a DOE funded partnership project with industry (two window and four component manufacturers) to develop drop-in Hi-R windows units for existing frames. Although the initial focus is residential windows, the technical concept and the need for energy performance transformation, also applies to the window market for commercial buildings.

We are interested in using this opportunity with the IMPEL program to understand methods that industry uses to push technology into the market. Also, an exploration of how industry views and markets energy improvement technology compared to other amenities (such as security and aesthetics) will help accelerate needed and feasible energy efficiency improvements in the window market.