Low-E Window Film in Philadelphia

Why Low-E Window Film Fits Philadelphia's Climate

Philadelphia buildings spend months heating and months cooling. Most window films are built for one job: rejecting solar heat in summer. Low-E films do that and also reflect long-wave heat radiating from inside the room back toward the interior in winter. That second job is what matters in a city where heating season runs from fall into spring.

Many older commercial buildings, schools, churches and apartment buildings in the city still have single-pane or early double-pane glass with no low-emissivity coating. Those windows are cold to sit next to in January and hot in July. Low-E film is a retrofit that brings some of the performance of modern coated glass to the windows already in place.

Churches, schools and older institutional buildings across the city are a good example. Many have tall windows sized for a time before air conditioning and central heat, and big rooms that are expensive to heat. Low-E film is one of the few options that does not change the window's appearance much and does not require replacing frames that may be part of the building's character.

How Low-E Window Film Works

All warm objects give off infrared heat. In a heated room, walls, furniture and people radiate heat toward the windows, and plain glass absorbs it and passes it outside. A low-emissivity coating reflects much of that radiant heat back into the room instead, reducing heat loss through the glass.

In summer, the same film rejects a share of incoming solar heat, as standard solar control films do. Different products balance these effects differently. Some favor winter insulation, others favor summer heat rejection, and we choose based on the building's orientation and where its problems are.

On a spec sheet, the U-factor, or a stated improvement in it, describes winter performance, and the solar heat gain coefficient describes summer performance. We provide both for film applied to your glass type.

Low-E Film for Philadelphia Apartment and Institutional Buildings

Large rowhouse conversions, older apartment buildings around Fairmount and University City, and institutional buildings often have dozens or hundreds of identical older windows. Replacing them all is a major capital project, and in historic districts it can require Historical Commission review. Low-E film can be installed unit by unit or floor by floor with no exterior work.

Tenants notice the difference mostly as comfort. Rooms near the windows feel less chilly in winter, and there are fewer complaints about drafts that are really radiant heat loss to cold glass rather than air leaks.

Low-E film also reduces how cold the inside surface of the glass feels, which can help with condensation on single-pane windows in some cases. Heavy condensation usually points to high indoor humidity or poor ventilation, though, and film is not a fix for that. We will tell you honestly if we think the problem lies elsewhere.

Low-E Film and Philadelphia Energy Requirements

Owners of large buildings in Philadelphia report energy use under the city's benchmarking rules, and larger properties face building performance requirements as well. Low-E film affects both heating and cooling loads, making it a reasonable measure to evaluate alongside air sealing, controls and equipment upgrades.

Heating fuel varies by building. Many city properties use natural gas from Philadelphia Gas Works, others use oil, steam or electric heat, and PECO supplies electricity across the region. Whatever the fuel, your engineer can use the film's performance data to estimate savings. We do not promise a specific percentage, because results depend heavily on the building.