The best filament for outdoor use is ASA: Prusa rates it for high UV resistance and service up to 93 °C, though it wants an enclosed printer. PETG is the runner-up and works outside in shade or part sun below about 80 °C. PLA is not an outdoor material, and ABS yellows and embrittles in sunlight.
ASA wins for a specific structural reason rather than a marketing one, and every figure below is attributed to vendor documentation or a published weathering study. The useful part is not the ranking, it is knowing which failure mode kills your part first: ultraviolet, service temperature, or water.
Pick by failure mode, not by strength
Outdoor parts rarely fail because the material was too weak on day one. They fail because sunlight breaks the polymer, because a dark part in direct sun climbs past its softening point, or because thermal cycling pries apart layer bonds.
| Material | UV behaviour | Practical service ceiling | Warping | Verdict outdoors |
|---|---|---|---|---|
| ASA | High UV resistance | 93 °C (Prusa) | Significant | Default for sustained sun |
| PETG | Loses strength under UV-B | Below 80 °C (Prusa) | Low | Fine for shade and short seasons |
| PCTG | Rated “Good”, no weathering data on data sheets | 64 °C heat deflection at 1.8 MPa (Extrudr) | Enclosure advised for large parts (Extrudr) | Tough option for shade and part sun |
| PLA | Degrades under UV; softens first | Over 60 °C it deforms | Very low | Not for structural outdoor parts |
| ABS | Yellows and embrittles | ~90 °C class | Significant | Use ASA instead |
| PP | Chemically resistant, hydrophobic | Grade dependent | Severe | Niche, hard to print |
Polypropylene is there for chemical and water resistance, not sunlight, and it is a hard print: MatterHackers lists a 210 to 230 °C nozzle, a 50 to 80 °C bed, 30 to 50 mm/s, a 25 to 35 mm brim and a strong tendency to warp.
Why ASA wins, in one paragraph of chemistry
ABS and ASA are nearly the same material with one component swapped. ABS carries a polybutadiene rubber phase whose unsaturated carbon-carbon double bonds react with UV and oxygen, producing the familiar chalking, yellowing and loss of impact strength. ASA uses an acrylate rubber instead, and as Formerra’s materials documentation puts it, “because the acrylate backbone contains no unsaturated carbon-carbon double bonds, it does not react with UV radiation or oxygen through the photooxidation pathways that degrade ABS.” The same page reports that under ASTM G155 xenon-arc weathering, ASA retains more than 80% of its impact strength after 2,000 hours while ABS retains 20 to 30%, with colour shift typically staying below a Delta E of 2 units. That is the whole argument for ASA in one swap. The head-to-head on print settings, strength and fumes is in ABS vs ASA for printing.
The Prusa Knowledge Base ASA page rates it for high UV resistance and temperatures up to 93 °C. The Polymaker ASA technical data sheet lists a 98 °C glass transition, a heat deflection temperature of 100 °C at 1.8 MPa and 103 °C at 0.45 MPa, and a density of 1.13 g/cm³.
The spool costs little more than PETG. In October 2026 Prusa’s store listed Prusament ASA at $25.92 for an 800 g spool and Prusament PETG at $29.99 for 1 kg, about $32 against $30 per kilogram. The real cost of ASA is the enclosure, not the filament.
Is PETG good for outdoor use?
Yes, for parts in shade or part sun that stay below about 80 °C. Prusa rates PETG for “interior and most exterior use (with temperatures below 80 °C)” and lists it as water and humidity resistant. What PETG is not is UV-stable, so a load-bearing PETG part in all-day sun loses strength much faster than an ASA one.
In the accelerated-aging study published in Polymers 13(23):4132 in 2021, FDM-printed PLA and PETG coupons were run through accelerated UV-B ageing at 310 nm, in cycles of 8 hours of dry lamp exposure at 0.43 W/m²/nm at 50 °C and 50% humidity followed by 4 hours of condensation at 23 °C. Three cycles gave 24 hours of UV in total, which the authors describe as equivalent to several months outdoors. PETG lost 36% of its tensile strength and 38.3% of its compressive strength. PLA lost 5.3% and 6.3% respectively. Stiffness did not shift meaningfully for either.
That inverts the usual advice. Under UV specifically, PETG degrades far faster than PLA. It still beats PLA outdoors, but on service temperature and moisture, not on sunlight. A PETG bracket in a shaded north-facing spot will run for years; the same bracket on a south-facing roof is on a clock.
The damage appears to start at the surface. In the 322-day study covered in the PLA section below, PETG’s measurable changes stayed within the outer 10 micrometres, so extra walls give a PETG part more material to lose before the load path is affected.
Heat is the other limit. Polymaker’s PolyLite PETG data sheet gives an 81 °C glass transition and a heat deflection temperature of 75 °C at 1.8 MPa, against 98 °C and 100 °C on its ASA sheet: about 25 °C less headroom for a loaded part in the sun. PETG’s advantage is on the printer, where the same sheet lists no enclosure needed and a 70 to 80 °C bed.
Where that leaves PETG outside:
- Works: shaded brackets, hose and cable guides, under-eave mounts, planter inserts, and parts that mostly see water rather than sun.
- Marginal: part-sun parts. Print them in a light colour with four or more walls and check them each season with the coupon test at the end of this page.
- Avoid: dark, load-bearing parts in full sun, such as roof fixtures and south-facing wall mounts. Print those in ASA.
Dry the spool first. Polymaker specifies 65 °C for 6 hours for PolyLite PETG, and a damp spool prints weak layer bonds, the interface weather attacks first. The wet filament symptoms guide shows how to spot one.
ASA vs PCTG: which is better outdoors?
ASA is better for parts in full sun or near heat; PCTG is better for shaded or part-sun parts that take knocks, and it is easier on a printer without an enclosure. ASA’s heat deflection is 36 °C higher and its weathering is documented, while PCTG’s UV rating is qualitative but its notched impact strength is several times higher.
PCTG is a copolyester sold as a tougher PETG: Extrudr cites a notched impact strength of 94 kJ/m² for its PCTG against 4.7 kJ/m² for standard PETG.
| Property | ASA | PCTG |
|---|---|---|
| UV evidence | ”High UV resistance” (Prusa); resin grades keep over 80% of impact strength after 2,000 h xenon arc (Formerra) | Rated “Good” with no test method; permanent exposure can cause gradual fading or embrittlement (Extrudr) |
| Glass transition | 98 °C (Polymaker) | About 85 °C (Extrudr); 84 °C (3D-Fuel) |
| Heat deflection, 1.8 MPa | 100 °C (Polymaker) | 64 °C (Extrudr) |
| Heat deflection, 0.45 MPa | 103 °C (Polymaker) | 76 °C (Extrudr); 74–76 °C (3D-Fuel) |
| Notched impact | 10.3 kJ/m² Charpy (Polymaker) | 94 kJ/m² (Extrudr); 93 kJ/m² Izod, ISO (3D-Fuel) |
| Nozzle | 230–260 °C (Polymaker); 260 °C (Prusa) | 230–270 °C (Extrudr); 260–280 °C (3D-Fuel) |
| Bed | 75–95 °C (Polymaker); 105 °C then 110 °C (Prusa) | 90–110 °C (Extrudr); 70–80 °C (3D-Fuel) |
| Part cooling | Off (Polymaker) | 20–50% (Extrudr) |
| Enclosure | Needed (Polymaker); necessary for large parts (Prusa) | Required for larger parts (Extrudr); not typically required (3D-Fuel) |
| Drying | 70 °C for 7 h (Polymaker) | 60 °C for 4–6 h (Extrudr) |
| Spool price, October 2026 | $25.92 per 800 g (Prusament) | €29.99 incl. VAT per 0.8 kg (Extrudr) |
Read the impact row as roughly an order of magnitude, not an exact ratio, since the figures come from different vendors’ sheets. The UV row matters more. 3D-Fuel’s Pro PCTG data sheet claims better UV resistance than PETG but describes its weathering tests against PETG and ASA as underway, with no results given. 3D-Fuel’s own comparison says PCTG “handles up to 80–85°C”, above the 64 to 76 °C heat deflection figures on the data sheets. Design to the data sheet, and keep PCTG for hinges, clips and housings in shade or part sun, where a brittle crack is a bigger risk than UV.
Is ABS filament OK for outdoor use?
ABS is a poor choice for parts in sunlight. Prusa’s ABS page lists “Lacks UV resistance (unlike ASA)” among its drawbacks and warns that “ABS parts used outdoor turn yellowish and more brittle over time.” Since ASA prints at nearly the same settings, there is little reason to choose ABS for an outdoor part.
The cause is the rubber phase described above, and the 322-day UV study found ABS changing deep below the surface until it embrittled. Prusa’s profiles differ by only 5 °C at the nozzle, 255 °C for ABS against 260 °C for ASA, so switching is a profile tweak. Keep ABS for parts that never see direct sun.
PLA fails thermally before it fails optically
The folklore says PLA dies in sunlight. Longer-duration work is more specific. In the long-term photooxidative ageing study (arXiv:2606.00068), PLA, ABS, PET, HIPS and PC were held under UV for 7,744 consecutive hours (322 days) in a controlled environmental cell. PLA and polycarbonate showed the highest UV resistance of the set, while ABS and HIPS changed deep into the material and ABS embrittled. PETG changed only within the top 10 micrometres.
That does not make PLA an outdoor material. Prusa states plainly that PLA “gets soft and deforms at temperatures over 60 °C” and is “not suitable for technical and outdoor use”. A dark part in direct summer sun reaches that easily, so a PLA bracket sags long before UV chemistry gets a vote. PLA outdoors is a seasonal decoration in shade, not a structural part. PLA+ does not move that line, because the plus buys toughness, not heat resistance.
ASA settings, and the two that people get wrong
Prusa’s ASA profile runs a 260 °C nozzle with the bed at 105 °C for the first layer and 110 °C after. Polymaker’s sheet gives a wider 230 to 260 °C nozzle range with a 75 to 95 °C bed, lists an enclosure as needed, and specifies drying at 70 °C for 7 hours. Start with your vendor’s own sheet; ASA formulations vary more than PLA does.
The two settings that decide success:
- Chamber temperature. Prusa calls significant warping ASA’s main disadvantage and says an enclosure is necessary for large parts. Ambient temperature, not nozzle temperature, stops corners lifting. Target ranges by material are collected in PrintLabGuide’s chamber temperature reference.
- Part cooling. Aggressive cooling buys surface finish and costs layer adhesion, which is the property an outdoor part needs most. Keep the fan low. Bambu owners can start from the per-material profiles in this Bambu filament settings guide.
Not a print setting, but from the same Prusa page: ASA “releases potentially dangerous fumes during printing” and wants a well-ventilated area.
Design for weather, not just for strength
Polymaker’s ASA sheet gives tensile strength of 43.8 ± 0.8 MPa in X-Y but only 32 ± 1.8 MPa in Z. That 27% penalty across layer lines is where weathered parts break, since thermal cycling and UV attack the interface first. Four consequences:
- Orient the part so the main load runs in-plane, not across layers.
- Buy strength with walls rather than infill. Four or five perimeters at a 0.42 mm line width does more for a weather-exposed bracket than raising infill from 20% to 40%.
- Design out water traps. Water standing in a blind pocket freezes and splits layers regardless of polymer.
- Pick a light colour if the part is marginal on temperature. Pigment drives solar gain, and that is how a PLA or PETG part crosses its softening point on an otherwise mild day.
How to verify it on your own parts
Do not take any of this on trust, including the table above. Run a control coupon on your own spool.
- Print two identical coupons from the same spool and profile. A 60 × 20 × 4 mm bar with 4 walls and 20% gyroid is enough.
- Mount one outdoors in the orientation and exposure the real part will see. Keep the second indoors as a control.
- At 30 days, compare them for chalking, gloss loss and colour shift without bending or breaking either coupon.
- At 90 days, repeat the visual comparison, then snap both by hand. Reserve this destructive comparison for day 90 only.
Success criteria: no chalking, no obvious colour difference against the control, and the exposed coupon breaking with roughly the effort the control needs. If it snaps noticeably easier, the material is embrittling and the real part is on borrowed time. Before blaming the filament, confirm both coupons were dry when printed, since wet filament makes weak layer bonds that look exactly like weathering damage. Our filament drying guide has temperatures by material, and PLA vs PETG vs ABS covers the indoor tradeoffs.
FAQ
what is the best filament for outdoor use without an enclosure
PETG is the best outdoor filament for an open-frame printer, with PCTG as the tougher alternative. Polymaker’s PolyLite PETG sheet lists no enclosure needed, and 3D-Fuel says its Pro PCTG does not typically require one, though Extrudr advises a closed chamber for larger PCTG parts. Small ASA parts can work; Prusa calls an enclosure necessary for large ones.
is petg uv resistant
No, PETG is not UV-stable, though shaded PETG parts last well outdoors. In the Polymers 2021 study, 24 hours of accelerated UV-B cut printed PETG’s tensile strength by 36%, against 5.3% for PLA. Prusa rates PETG for most exterior use below 80 °C but makes no UV claim, so expect gradual surface damage in direct sun.
is pctg good for outdoor use
PCTG is good for shaded or part-sun outdoor parts that need impact toughness, but it is not a proven substitute for ASA in full sun. Extrudr rates its UV resistance “Good” without a test method and warns that permanent outdoor exposure can cause gradual fading or embrittlement. Its 64 °C heat deflection at 1.8 MPa trails ASA’s 100 °C.
is pla+ good for outdoor use
No, PLA+ is not an outdoor material either. 3D-Fuel rates its own Tough Pro PLA+ as softening at 55 to 60 °C, with poor UV resistance, and best for indoor projects. The plus is an impact modifier that buys toughness, not heat resistance, so the same 60 °C ceiling that rules out PLA outdoors applies.
