GSA's 2-to-6-Year Payback: Why Low-E Window Film Outperforms Standard Solar Control Film in Year-Round Climates
Mar 16th 2026
Source: U.S. General Services Administration, GPG-032: Low-E Window Film (February 2017). Produced in partnership with Lawrence Berkeley National Laboratory (LBNL). Public domain.
The Problem Standard Solar Control Film Cannot Solve
Solar control window film is one of the most cost-effective energy retrofits available for commercial buildings. The GSA's own research (GPG-017) documented up to 29% HVAC savings in warm climates. But there is a limitation that facility managers in mixed and cold climates know well: conventional solar control film saves energy in summer and wastes it in winter.
The solution, documented in the GSA's GPG-032: Low-E Window Film (February 2017), is a dual-function film that addresses both problems simultaneously.
What Low-E Window Film Does Differently
Low-emissivity (Low-E) window film combines two technologies in a single product:
Solar control layer: Reduces solar heat gain (SHGC) in summer, just like conventional solar control film. This reduces cooling loads and air conditioning costs during warm months.
Low-emissivity coating: Reduces the emissivity of the glass surface, which slows the rate at which heat radiates through the window in winter. This is the same principle used in double-pane Low-E glass — applied as a retrofit film to existing single-pane windows.
The GSA's Test Results: Two Federal Buildings, Two Climates
The GSA commissioned LBNL to test Low-E window film at two federal buildings:
Hansen Federal Building — Ogden, Utah (Cold Climate, Zone 5)
A single-pane clear glass building in a cold, high-altitude climate. Low-E film reduced both summer cooling loads and winter heat loss, delivering measurable year-round energy savings.
Cabell Federal Building — Dallas, Texas (Hot Climate, Zone 2)
A single-pane clear glass building in a hot climate. Low-E film delivered strong cooling savings comparable to conventional solar control film, with the added benefit of reduced winter heat loss.
| Metric | Result |
|---|---|
| HVAC savings in perimeter zones | Up to 29% |
| Simple payback period | 2 to 6 years (single-pane clear glass) |
| Best performance | Cold and mixed climates (Zones 4–6) |
| Year-round benefit | Yes — cooling AND heating savings |
| Occupant comfort | Improved thermal comfort, reduced glare |
Why Low-E Film Is the Right Choice for Mixed-Climate Buildings
| Film Type | Summer Savings | Winter Savings | Best Climate |
|---|---|---|---|
| Standard Solar Control | High | Negative (increases heating load) | Hot climates (Zones 1–3) |
| Low-E Window Film | High | Positive (reduces heat loss) | Mixed/Cold climates (Zones 4–6) |
Solar Gard Ecolux 70: The Professional Low-E Solution
The Window Place USA supplies Solar Gard Ecolux 70, the professional-grade Low-E window film that delivers the dual-function performance documented in the GSA's GPG-032 study. Ecolux 70 provides 70% visible light transmission, low SHGC for summer cooling savings, low-emissivity coating for winter heat retention, and a 15-year manufacturer warranty.
Shop Ecolux 70 Low-E Window Film →
Frequently Asked Questions
What is the difference between Low-E window film and standard solar control film?
Standard solar control film reduces solar heat gain in summer but can increase heating energy use in winter. Low-E window film adds a low-emissivity coating that reduces heat loss through the glass in winter, delivering year-round energy savings.
Does Low-E window film look different from regular window film?
No. Solar Gard Ecolux 70 at 70% VLT is essentially invisible. It maintains the clear appearance of the glass while adding both solar control and thermal insulation properties.
Can Low-E window film be applied to double-pane windows?
Yes, but the payback period is longer than for single-pane glass. The GSA's GPG-032 study focused on single-pane clear glass, where the energy savings are greatest.
[2] U.S. General Services Administration. (February 2017). GPG-032: Low-E Window Film. Green Proving Ground Program. Retrieved from https://www.gsa.gov/system/files/GPG032-Low-E%20Window%20Film-Findings-508R.pdf. U.S. Government work, public domain under 17 U.S.C. § 105.