Serious Materials Ultra-Efficient Windows Window manufacturers just might have one of the toughest jobs in providing green building products: making large “energy holes” in walls more efficient. They’ve come a long way, but there’s still lots of room for improvement. Serious Materials, following a recent acquisition of Alpen Energy Group, has once again taken the effort a giant step forward with the introduction of ThermaProof windows, which boast full-frame R-values from 5 to 15, a significant jump from the R-2.5 to R-3 of a typical double-pane, low-E unit. The windows are made up of three efficient components: window glass with a layer of metal-sputtered Mylar that boosts center-of-glass R-values; a choice of a foamed PVC frame or a fiberglass frame with soy foam insulation; and an Eco Spacer that reduces heat loss at the edges. With this introduction, the company is also looking to shift industry-accepted efficiency language to full-frame, rather than center-of-glass, and to R-value, which they say is more familiar and under-standable, rather than U-value. 800.797.8159.