Exterior solar screens vs window tint: which cuts more heat?

An exterior solar screen cuts more heat than window tint on a sunny window. Efficient Window Coverings puts an exterior solar screen at a shading coefficient of 0.14 to 0.33, which works out to a solar heat gain coefficient (SHGC) of about 0.12 to 0.29, so the window lets in roughly an eighth to under a third of the sun's heat. Film is bonded to the glass, and the energy it absorbs heats the pane and partly ends up in the room. Film wins on UV, on keeping a clear view and on zero upkeep. The screen wins on heat and on winter flexibility, because it can come off.

Solar screens vs window tint at a glance

Screen figures are from Efficient Window Coverings' exterior solar screen page, film figures from its applied film page.

Why outside the glass wins on heat

A solar screen and a film both turn sunlight away, but in different places. An exterior screen catches the sun before it reaches the pane. Whatever the mesh absorbs warms the mesh, and outdoor air carries that heat off. Film sits on the glass, so it can only reflect or absorb the sun at the pane itself. Efficient Window Coverings states the cost of absorbing plainly: absorbing films are less effective "because the absorbed energy will heat the glazing surface and a portion of that energy will be transferred into the room." It lists "Higher-absorbing films will reduce energy savings and decrease comfort" among film's drawbacks.

The screen figures show the same thing. Mounted outside, the same mesh reaches a shading coefficient of 0.14-0.33. Mounted inside the glass, it only gets to 0.50-0.70, because the sun has already come through the pane and the warm mesh gives its heat to the room. Film is always at the glass.

Worked example: one west window, three treatments

This uses the same heat-gain method as our solar screens vs insect screens comparison: glass area x sun on the glass x SHGC.

The published screen coefficients are treated as the whole window's figure, as in the sibling example. Real results move with glass, sun angle, mesh color and openness. Efficient Window Coverings notes that color alone "can change the shading performance by as little as 5% or as much as 100%," and openness by 5-25% for the same color. Choosing a step is covered in screen mesh openness factor. To turn watts into a seasonal bill, use the energy savings calculator or the step-by-step method in energy savings from awnings.

View, glare and daylight

Efficient Window Coverings lists "Reduced view and clarity (fixed panels)" as the solar screen's main drawback and puts its look at "about the same impact as insect screens, depending on color." Film keeps the glass clear, but its listed drawbacks include "Undesirable interior 'mirroring' with interior films" at night and that it "May increase need for electric lighting." A retractable screen gets around the view problem by rolling up when the sun is off that wall, which a film cannot do. See zip track screens for motorized versions.

Winter solar gain: removable beats permanent

Efficient Window Coverings' advice for screens is direct: "take down solar screens to increase solar gain and reduce heating costs." A retractable screen just rolls up. Film cannot step aside. Its own listed drawbacks include "Reduce winter solar heat gain (in heating-dominated climates)," and once installed it requires "special procedures and release agents to remove."

The Lawrence Berkeley National Laboratory study Energy Savings from Window Attachments (2013, for the US Department of Energy) modeled this across 12 US climates. It found that exterior attachments "are generally more effective in saving cooling energy," but that this "does not always translate to the highest overall energy savings due to a potential increase (penalty) in heating energy." It names exterior films among the attachments that "provide little to no energy benefit in heating dominated climates," with some using more energy than the bare window. In cooling-dominated climates, the same study found "all window attachments save energy."

UV and fading

This is film's clear win. Applied film blocks "UV very effectively (95-99.9%)." Solar screens give "Excellent UV protection (75-99%)," and the low end of that range belongs to the more open weaves. Sun through the holes is unfiltered, so a mesh's UV ceiling tracks its openness; see UPF and UV protection. Where fading, not heat, is the problem, film is the better tool.

Cost and upkeep

For one 30 by 60 inch window, Efficient Window Coverings puts a fixed exterior screen panel at about $45 and a motorized roller at about $500. Film runs about $10 DIY, $80 for standard solar control and $125 for spectrally selective film. A fixed panel is both cheaper and cooler than film; a retracting screen costs more. Installed prices for motorized exterior shades on full-size openings are covered in retractable screen cost.

Film needs "No operation or maintenance." Screens need cleaning, and motorized ones add a motor and fabric that eventually need replacing. Our solar mesh FAQ puts quality vinyl-coated polyester at around 10 years or more in full sun.

When this comparison stops applying

• North glass. North windows get little direct sun, so neither product saves much heat there. Film may still earn its place for UV.
• Low-e glass already present. Modern low-e glass often has an SHGC of 0.25-0.40 before anything is added. In the LBNL tables for a house with double-pane low-e windows, the solar screen saved at most 3.3 GJ a year and the applied films at most 2.9 GJ in the three climates shown, and several combinations used more energy than the bare window. On this glass, buy either product for glare or comfort, not for the bill.
• Renters. Film is close to permanent: removal is a professional job with release agents, so it needs the landlord's agreement. A fixed screen panel or an interior retractable window screen comes out when you leave, though an interior screen gives up most of the heat benefit.
• Outswing casements and awning windows. Efficient Window Coverings says exterior installation is "not appropriate for outward swinging windows." Here film, or a screen mounted where the sash cannot hit it, is the realistic choice.
• HOA and historic districts. An exterior screen changes the facade, and HOAs commonly review visible exterior changes, including color. Historic commissions often review any visible change. Interior film adds no hardware to the facade. Check the rules before ordering a screen: see permits, HOA rules and building codes.

How to compare two specific products

Ask both sellers for an SHGC on the same glass. Window film was the first window attachment option to be rated by the NFRC, so ask for the film's NFRC-rated SHGC on your glass type. Solar screens fall under the Attachments Energy Rating Council, whose AERC program rates "blinds, cellular shades, roller shades, storm windows, solar screens and pleated shades." Its certified product search filters by U-factor, solar heat gain coefficient, visual transmittance and air leakage, and products are "simulated over a double pane, clear window" unless you pick another glass. If you are also weighing an awning for the same wall, sun angle decides it: see exterior solar shades vs awnings.

Frequently asked questions