RetractWise

UPF and UV Protection Under an Awning: What Ratings Mean and What They Miss

By Retract Wise Editorial TeamUpdated 8 min readEditorial standards

UPF (Ultraviolet Protection Factor) measures how much UV passes through a fabric: UPF 50 lets through about 1/50, or 2%, of skin-burning UV. Most solution-dyed acrylic and coated awning fabrics in medium and dark colors rate UPF 50+, so the fabric is rarely the weak link. Under an awning, most of the UV you still receive comes from open sky beside and in front of you and from surfaces that reflect it, so size, projection and side screens matter more than the label.

Key takeaways

  • UPF is a fabric property: UPF 30 passes about 3.3% of UV, UPF 50 about 2%. Beyond UPF 30 the difference to your skin is small.
  • Under a typical patio awning, scattered skylight and reflected UV often deliver many times more UV than what passes through the fabric.
  • For mesh and screens, UPF can be no better than about 1 divided by the openness factor: a 10% mesh tops out around UPF 10.
  • Darker colors and tighter weaves score higher, but lighter colors of quality awning acrylic are often still UPF 50+.
  • Bigger projection, a lower front edge, a valance or drop screen and non-reflective ground do more for protection than chasing a higher UPF.

What UPF measures

A lab shines a calibrated UV source through a fabric sample and measures the transmitted spectrum. Each wavelength is weighted by how strongly it causes sunburn (the erythemal action spectrum), and UPF is the ratio of the weighted UV without fabric to the weighted UV with fabric. In the US the test method is AATCC TM183, with ASTM D6603 covering labeling; in Australia and New Zealand, AS/NZS 4399 is the reference and also defines the familiar protection bands. European practice for textiles uses EN 13758.

UPF values and UV transmission
UPFUV transmitted (approx.)UV blocked (approx.)Common rating band
156.7%93.3%Good
254.0%96.0%Very good
303.3%96.7%Very good
402.5%97.5%Excellent
50+2.0% or less98% or moreExcellent

Note how flat the top of the table is: going from UPF 30 to UPF 50 changes transmission from about 3.3% to 2%. Going from UPF 15 to 30 halves it. "UPF 50+" is a ceiling on labels, not an indication that one fabric is dramatically better than another at UPF 80.

UPF is different from SPF (which is measured on skin with sunscreen) and from a "UV block %" figure some sellers quote. A "90% UV block" claim on shade cloth means roughly UPF 10, which is modest.

What affects an awning fabric's UPF

  • Cover factor (tightness). Gaps between yarns let UV straight through. Tightly woven awning acrylic has very little open area; mesh is deliberately open.
  • Color and pigment. Dark and saturated pigments absorb more UV. Black, navy and forest green typically rate highest; white and pale cream lowest, though quality awning acrylic in light colors is often still UPF 50+. Check the specific color.
  • Coatings. PVC-coated and vinyl fabrics are near-opaque to UV in almost every color.
  • Weight and thickness. More fiber in the path means more absorption.
  • Wear. A fabric that has thinned or opened up at stress points lets more through. On a stretched, waffled cover, the change is small, but holes and abraded valances leak.

Mesh and screens: the openness ceiling

For screen fabrics, the openness factor (the percentage of open holes in the weave) caps UV protection. UV passing straight through a hole is not filtered at all, so a mesh with 10% openness passes at least 10% of direct UV, plus whatever leaks through the yarns. That gives a practical rule: maximum UPF is roughly 100 divided by the openness percentage.

Openness factor and the best-case UPF of a mesh
Openness factorMinimum direct UV through holesBest-case UPF
1%1%About 100 (labeled 50+)
3%3%About 33
5%5%About 20
10%10%About 10
14%14%About 7

Real values are a little lower because yarns transmit some UV, especially in light colors. Choosing mesh for view, glare and heat is covered in screen mesh openness factor.

Where the UV under an awning actually comes from

UV reaches you from three paths:

  1. Direct sun, which the awning blocks when you are in its shadow.
  2. Diffuse sky UV, scattered by the atmosphere. On a clear day a large share of UVB (often around half) arrives from the sky dome rather than the sun's disk, and more on hazy or thinly overcast days. Any open sky you can see from your seat sends UV at you.
  3. Reflected UV from the ground and walls. The World Health Organization notes fresh snow can reflect up to about 80% of UV and dry sand about 15%; concrete and light pavers reflect more than grass or wood decking.

A fabric with UPF 50 handles only the part of path 1 that hits the fabric. Paths 2 and 3 come around it.

Retract Wise analysis: Take a midday UV Index of 10 and assume half of it is diffuse sky UV. You sit in the middle of a 10 ft (3 m) projection lateral arm awning with open sides. Looking out under the front edge and past the open ends, you can see very roughly 40% of the sky dome. Your exposure: direct sun blocked by a UPF 50 fabric leaves 10 x 0.5 x 0.02 = 0.1. Diffuse sky through the gaps adds about 10 x 0.5 x 0.4 = 2.0. Reflection off light pavers might add 0.3-0.5. Total: around UVI 2.5, of which the fabric's leakage is just 4%. Swapping to a UPF 100 fabric would change nothing you could measure; adding a 5 ft (1.5 m) side screen or extending projection would. The rule: once fabric is UPF 30 or better, spend your money on geometry.

The illustration uses rounded assumptions, but the proportions hold for most open patio awnings. The closer you sit to the front edge and the higher the awning is mounted, the more sky you see.

How to improve real UV protection

  • More projection. A deeper awning pushes the open edge farther from where you sit. Use the shade calculator to see where the shadow falls at the times you use the patio.
  • Lower front edge. More pitch or a lower mounting height reduces the sky visible beneath the front edge. Pitch also matters for rain, so see awning pitch explained.
  • A drop valance or front screen. A roll-down valance blocks low afternoon sun and the band of sky under the front bar.
  • Side screens or a wall. Awnings tucked into an L-shaped corner protect far better than those on a flat open wall.
  • Darker, less reflective ground. Outdoor rugs or wood decking under the seating area reflect less than white pavers.
  • Width beyond the seating. Extending 2-3 ft (0.6-0.9 m) beyond the furniture on each side cuts sideways sky exposure noticeably.

For sizing, see how to measure for an awning and the awning size calculator. Seasonal shade depth by latitude is tabulated in shade coverage tables.

Safety note: Shade reduces UV; it does not eliminate it. For people with photosensitivity, young children at midday or long afternoons outdoors, combine shade with sunscreen, hats and clothing. An awning is part of a sun-protection strategy, not all of it.

Worked example: choosing for a pool deck

Worked example: A family wants shade beside a pool with light concrete coping in Phoenix (around 33.4° N). Options: (A) a 12 ft (3.66 m) wide, 10 ft (3 m) projection acrylic awning in sand color, UPF 50+; (B) the same awning with a 5 ft (1.5 m) motorized drop screen in 3% mesh; (C) a 14 ft (4.27 m) wide, 11.5 ft (3.5 m) projection awning in the same fabric. The pool and concrete reflect UV strongly and the site is open to the west. Option A protects well at solar noon but leaves a large band of open sky to the west in afternoon. Option B's 3% mesh (best case about UPF 33) closes that band and still lets people watch the pool. Option C helps somewhat at all times of day. If afternoon use dominates, B wins; if midday use dominates, C is a strong choice. In neither case would a different fabric UPF change the outcome.

UV and the fabric itself

UV protection for people and UV resistance of the fabric are different properties. A fabric can block 98% of UV (high UPF) and still fade badly if its dye is not UV-stable. Lightfastness and fiber stability decide how long the awning looks good; see solution-dyed acrylic explained. Color also changes how hot it feels under the awning, which is covered in awning fabric colors and heat.

Frequently asked questions

Do I need UPF 50 or is UPF 30 enough for an awning?

UPF 30 passes about 3.3% of UV and UPF 50 about 2%. Under an awning, sky and ground reflection usually dominate, so the difference to your skin is negligible. Choose the fabric for color, durability and heat, then confirm it is UPF 30 or better.

Can you get sunburned under a retractable awning?

Yes, especially near the front edge, with open sides, near water or snow, or on bright pavers. Exposure under shade can still be meaningful on high UV days, so combine shade with other protection for long sessions.

Do white awnings block UV?

Often yes, but less than dark colors of the same fabric. Many quality white or cream acrylics still rate UPF 50+; some thinner or more open white fabrics do not. Ask for the UPF of the exact color.

Does awning fabric lose UV protection over time?

Tight, solution-dyed fabric retains most of its UV blocking for its useful life. Protection drops where the fabric wears thin, opens up or develops holes, which is a sign it is due for replacement anyway.

Is a mesh screen good enough for UV protection?

It depends on openness. A 1-3% mesh blocks most UV and works well; a 10-14% mesh is mainly a glare and insect solution, with a ceiling around UPF 7-10.

Does UV pass through clouds under the awning?

Thin or broken cloud lets much UV through and can increase the diffuse share. Because diffuse UV comes from the whole sky, open sides and a high front edge matter more on hazy days than on clear ones.

Sources and standards consulted

  • AATCC TM183, Transmittance or Blocking of Erythemally Weighted UV Radiation through Fabrics (AATCC)
  • AS/NZS 4399, Sun protective clothing: evaluation and classification (UPF) (Standards Australia)
  • ASTM D6603, Standard Guide for Labeling of UV-Protective Textiles (ASTM International)
  • EN 14501 and EN 13363, Solar protection devices: thermal and visual comfort, solar transmittance (CEN)
  • Awning fabric technical data sheets from major acrylic and polyester mills (manufacturer documentation)

See how we research for our sourcing and verification process.