ASA vs PETG: Outdoor Use, Heat, Enclosures, and Printing

Who this comparison is for

This guide is for someone printing a part that has to live outside: a garden fitting, a mailbox flag, a bike mount, a car exterior clip, or a housing that sits on a sunny windowsill. Makers sell both PETG and ASA for outdoor parts, and they print very differently. The choice usually comes down to four questions:

• How much sun, and for how long?
• How hot will the part get?
• Is your printer enclosed?
• Can you ventilate the room where it prints?

Everything below comes from documentation published by Prusa Research, Bambu Lab, Polymaker, OVERTURE, eSUN, and SUNLU. Where we quote a figure, it describes one maker's product under that maker's test conditions. Other brands and grades differ, so check the data sheet for the exact spool you buy. If you're also weighing ABS, see ABS vs ASA and PETG vs ABS.

Is ASA or PETG better for outdoor use?

Both materials are sold for outdoor parts, but the ASA makers make stronger, more specific claims, and one of them publishes test results.

ASA:

• Prusa lists "High UV resistance" as an ASA advantage and calls it "a technical material suitable for outdoor use." The Prusament ASA page says it is "UV stable" and that the material "will keep toughness and durability for a long time and will not turn yellow."
• Polymaker says the "major difference" between ASA and ABS is that "ASA is extremely good at weather resistance." An FAQ on its ASA product page also reports test results for ASA. After "a two-year natural aging examination," it reports a color change (ΔE) below 2.5. In accelerated aging, it reports ΔE below 5 and "minimal tensile strength loss, even after exposure to 8000 kj/m2 irradiation." Polymaker concludes that parts exposed to "sunlight, rain, temperature fluctuations" maintain integrity "for a minimum of two years."
• Bambu Lab says its ASA "offers extraordinary UV, oxidation, and aging resistance, providing effective protection against breakage and color degradation when used outdoors for long-term purposes."
• eSUN says its ASA+ resists UV under long-term sunlight, "preventing fading, yellowing, or brittleness." SUNLU says its ASA stays "fade-resistant and shape-stable even after prolonged exposure to outdoor conditions." OVERTURE says its ASA is "specially formulated for maximum UV protection." SUNLU's data sheet adds a caveat in its handling section: "The product may yellow under the action of ultraviolet light, so it should be stored away from direct sunlight."

PETG:

• Bambu Lab says PETG Basic's "strong resistance to water, UV, and temperature makes it a highly cost-effective option for outdoor applications," with examples like garden labels.
• eSUN lists its PETG as "UV Resistant" and says it "Retains Color Without Fading."
• Polymaker is more cautious: "PETG is UV and water-resistant, making it suitable for outdoor parts, though prolonged exposure may degrade some properties."
• Prusa says PETG suits "mechanical parts for both indoor and outdoor use," but its PETG guide and Prusament PETG page don't make a UV claim.

Among the documents we checked, only Polymaker publishes weathering test results, and those appear on its ASA page, not its PETG page. No PETG maker here publishes an outdoor lifespan. That doesn't mean PETG fails outdoors, but if a part has to keep its color and strength in strong sun for years, the published evidence favors ASA. For a planter tag or a part in partial shade, the PETG makers above say their material is suitable.

Is ASA more heat resistant than PETG?

ASA also has the edge on heat. The fairest comparison is within one maker's data, since each maker tests its own way. Three makers publish heat deflection temperature (HDT) under ISO 75 for both materials:

Prusa's descriptive pages line up with those figures for ASA: both the ASA guide and the Prusament ASA page give a temperature resistance of 93 °C. For PETG, Prusa's pages don't agree with each other. The Prusament PETG page lists a temperature resistance of 68 °C, while Prusa's PETG guide says PETG parts suit "most exterior use (with temperatures below 80 °C)." If heat matters, design to the lower number. For Prusament PETG and Polymaker PETG side by side, see Prusament PETG vs Polymaker PETG.

Other ASA makers publish heat figures in their own formats:

For two of those spools side by side, see eSUN ASA+ vs SUNLU ASA.

OVERTURE publishes Vicat softening temperature instead. Its ASA data sheet gives 106.2 °C (ISO 306). The FAQ on its ASA page lists PETG at 85.1 °C for comparison, but OVERTURE's own PETG data sheet (V5.2) gives 75 °C. Vicat and HDT are different tests, so don't compare these numbers with the table above.

ASA's extra margin matters when a part may run near or above the PETG figures above. Bambu's filament guide says PLA is "Not recommended for environments at about 50 ℃ or higher," and lists PETG and ASA among materials that "Offer better heat resistance," so PETG is still a step up from PLA.

Enclosure, warping, and which printers suit each

This is where the two materials differ most at the printer.

Does ASA need an enclosure?

ASA makers agree it warps and call for an enclosed printer, with a few nuances:

• Prusa: calls warping "the main disadvantage of this material," lists "An enclosure is necessary for printing large parts" as a drawback, and says the bed should be at least 100 °C "and the printer should be inside an enclosure to keep a higher ambient temperature." Without one, Prusa suggests PrusaSlicer's draft shield. The Prusament ASA page says warping "can be eliminated by printing inside an enclosure or by adding a tall skirt around the object," and lists "Skirt or Enclosure Recommended."
• Bambu Lab: its filament guide says ABS, ASA, PC, and PA "Require higher heatbed and chamber temperatures to suppress warping and layer separation, and to ensure sufficient interlayer strength." Its ASA store page says "Enclosure Printers Required," and the Bambu ASA data sheet gives a chamber temperature of 45 to 60 °C. The store page also advises against printing "too large size and/or high infill density models."
• Polymaker: the ASA data sheet lists a closure chamber as "Needed," and the product page asks for an "Enclosure that can trap ambient air and keep it hot."
• OVERTURE and eSUN: OVERTURE's ASA page says "Enclosed Printer Required." eSUN's ASA+ page lists "enclosed-chamber printing" as its printing recommendation.
• SUNLU: its data sheet, in Chinese only, says to print enclosed ("封箱打印"); its English store page doesn't mention an enclosure. The page recommends a heated bed with glue stick or a PEI sheet "to eliminate warping."

Prusa adds a warning about heat inside the box: "printing a lot of ASA in an unventilated enclosure can cause the fan shroud and/or extruder plastic parts to deform over time." Our enclosure planning guide covers what an enclosure does and doesn't do.

Does PETG need an enclosure?

PETG barely warps, and the makers that address it say it doesn't need an enclosure:

• Prusa: says it "does not shrink or warp (it has very little thermal expansion)." The Prusament PETG page says "Enclosure not required," adding that even big objects printed without an enclosure rarely lift from the bed.
• Polymaker: the data sheet lists a closure chamber as "Not Needed."
• eSUN: says its PETG "requires no heated enclosure."

Bambu Lab adds a nuance: "For PETG and PETG-CF/GF, an enclosed printer is recommended to prevent low ambient temperatures from reducing the model's interlayer strength." Its PETG Basic data sheet gives a chamber temperature of 35 to 50 °C, lower than the 45 to 60 °C it gives for ASA. Too much heat is a problem for PETG, though. Bambu recommends opening the front door or removing the top glass cover on its enclosed printers so PETG doesn't soften in the extruder. The guide's text says to do this when the bed is above 60 ℃, while its plate table says to remove the glass cover when the bed is above 70 ℃. For ASA, the same table says "NO."

Which printers suit each

These fit notes come from printer makers' own documentation:

• Bambu Lab: the filament guide marks ASA "Not Recommended" on open-frame printers (A Series, P1P) and "Recommended" on enclosed ones (H2 Series, X2D, P2S, X1 Series, P1S). PETG is "Compatible" on both. Bambu's A1 FAQ is specific: it is "not recommended to use ABS, ASA, PC, PA" and similar materials on the A1 "for printing models that require high interlayer strength with large sizes and/or high infill densities," though they "can be used on A1 for printing small-sized models with low infill densities." Because "ABS and ASA release harmful and irritating gases," Bambu recommends "not to use A1 for printing ABS and ASA unless in well-ventilated environments at a safe distance from people." The same FAQ says "We don't recommend enclosing the A1."
• Prusa: the CORE One+ has an enclosed chamber that "heats up to 55 °C." Its spec table lists PETG as a supported material and ASA under "Advanced," and its filament cards rate PETG "Easy to print" and "ASA and ABS" as "Moderate." Prusa says the printer "automatically opens the vent for low-temperature materials (PLA, PETG) and closes it for high-temp materials." For ASA on Prusa's open-frame printers, the ASA guide points to the Original Prusa Enclosure or a self-built one.
• Other printers: check your printer maker's enclosure, chamber, and maximum nozzle and bed temperature specs before buying ASA. Our printer pages summarize what each maker documents.

Fumes and ventilation

Makers' safety guidance is much stronger for ASA:

• Prusa lists "Potentially dangerous fumes (styrene)" among ASA's drawbacks and says to print it "in a well-ventilated room because the material releases fumes and substances that could pose a potential health risk," without creating a draft around the print. The Prusament ASA page lists "Contains styrene" and "Produces odors during printing (less than ABS)."
• Bambu Lab's ASA page says "At printing temperatures, this filament may release harmful gases, including styrene, which can cause dizziness or nausea." It recommends a well-ventilated area or "an effective air filtration or exhaust system," "a protective mask with a vapor filter (such as an activated carbon mask)" for extended operation, and more ventilation or a pause if people with asthma or respiratory conditions, pregnant women, or children are present.
• Polymaker says to "Print in a well-ventilated area." OVERTURE says its ASA "does produce some odor during printing" and advises "ensuring good ventilation and considering air filtration." SUNLU's data sheet says the print area "should be well ventilated" and that "Local extract ventilation should be used when necessary."
• Prusa's CORE One+ page offers an optional Advanced Filtration System, which it says is useful for "materials such as ASA and other materials that produce an increased number of ultra-fine particles and fumes during printing."

For PETG, Prusament and Polymaker describe little odor. Prusament calls its PETG "Mostly odorless while printing," and Polymaker's data sheet describes "low odor." Bambu Lab says PETG Basic is "certified to UL GREENGUARD (UL 2904)" for low indoor printing emissions, but it still asks you to print it "in a well-ventilated area, or install an effective air filtration or exhaust system," the same wording it uses for ASA. Low odor doesn't mean no emissions.

Printing temperatures

ASA runs hotter at both the nozzle and the bed. These are each maker's published starting points, not universal settings:

The numbers shift even within one maker. The Prusament ASA product page gives 260 ± 5 °C at the nozzle where its data sheet gives ± 10 °C. Polymaker's ASA page gives 240 to 260 °C in one section and 230 to 260 °C in another. SUNLU's ASA page gives three bed ranges in different places (80 to 100 °C, 90 to 110 °C, and 80 to 120 °C); its data sheet says 80 to 100 °C. Start from the profile for your exact spool, and confirm that your hotend and bed are rated for ASA's temperatures before buying.

Part cooling differs too. Polymaker lists the fan "OFF" for its ASA and 20 to 60% for its PETG. OVERTURE's ASA data sheet says the fan is "Turned off." Prusament lists 30% for ASA (0 to 50% depending on geometry) and 50% for PETG. Bambu's data sheets give 0 to 80% for ASA and 0 to 60% for PETG Basic.

Build surfaces

PETG's quirk is that it can stick too well. Prusa says "Do not print on the smooth PEI sheet as the adhesion may be too strong!" and recommends a powder-coated or satin sheet, or a glue stick on smooth PEI if you use it anyway.

For ASA, Prusa's own pages differ. The ASA guide says to "Use the smooth or powder-coated PEI sheet with a glue stick." The Prusament ASA page recommends the satin sheet and says that "With the powder-coated or smooth sheet, the adhesion of the material can be too strong." The Prusament ASA data sheet lists satin, smooth PEI, and powder-coated sheets, with a footnote calling for a glue stick. Prusa also warns: "Do not put acetone or ABS/ASA juice on the powder-coated sheet!"

Bambu Lab lists both materials as "Not recommended" on its Cool Plate and compatible with its Engineering, Smooth PEI, and Textured PEI plates, and it recommends glue in general. Its ASA store page adds that ASA is "Not compatible with Cool Plate SuperTack," while the PETG Basic data sheet lists Cool Plate SuperTack as a supported plate. Polymaker lists "PC and Textured PEI" for both its PETG and ASA. OVERTURE's ASA data sheet calls for PVA glue on the build surface.

See textured vs smooth build surfaces for more, and warping if ASA corners lift. To clear glue residue between prints, see how to clean a build plate.

Moisture and drying

Both absorb moisture, and makers don't agree on which absorbs more. Each pair below was tested under one maker's conditions:

• Prusa Polymers (24 °C, 22% humidity): Prusament ASA absorbs 0.16% in 24 hours and 0.17% in 7 days, while Prusament PETG absorbs 0.07% and 0.10%. Prusament lists ASA as "Hygroscopic" and PETG as having "Low water absorption."
• Bambu Lab (saturated, 25 °C, 55% RH): 0.45% for both Bambu ASA and PETG Basic.
• Polymaker (70% RH, 23 °C): an equilibrium of 0.40% for its ASA and a maximum of 0.51% for its PETG. Polymaker says ASA "has low moisture uptake" but calls PETG "very hygroscopic."

Drying guidance from the makers:

Polymaker's product pages also give shorter cycles: 65 °C for 4 hours in its PETG spec block, and for ASA, 70 °C for 6 hours in one section, or 70 °C for 4 hours after only brief exposure. OVERTURE warns against "extended drying times" for ASA, which "can lead to the filament becoming brittle." Check that your dryer and spool can take ASA's higher drying temperature. Bambu's data sheets rate the ASA spool to 90 °C and the PETG Basic spool to 70 °C. Our dryer vs dry box guide covers the options.

AMS and automatic feeding

Bambu Lab documents both materials for its AMS units, but its pages disagree on ASA and the AMS lite:

• PETG: the filament guide lists PETG as "Compatible" with AMS and AMS lite. The PETG Basic data sheet lists "AMS, AMS 2 PRO, AMS HT, AMS Lite," and the store page says "All AMS Series Compatible."
• ASA: the filament guide lists ASA as "Compatible" in its combined AMS / AMS lite column. Bambu's ASA store page is firmer, saying "AMS lite NOT Compatible" alongside "AMS 2 Pro, AMS HT & AMS Compatible." We'd follow the store page for Bambu ASA.

Drying in the AMS differs as well. Bambu's guide lists ASA drying in the AMS 2 Pro as "Not recommended," while the AMS HT can dry it at 80 ℃ for 8 hours. PETG can be dried in either at 65 ℃ for 12 hours.

Polymaker says its PETG "works seamlessly with AMS and multi-material systems," and its ASA FAQ says its redesigned spool edges "spin great in the AMS." For other brands and multi-material systems, check the maker's own compatibility notes. Our AMS filament compatibility guide goes into spool sizes and feed paths.

Chemicals, solvents, and layer strength

Chemical resistance. Polymaker rates both materials on the same scale. Both are "Good" against weak acids and oils and grease, and "Poor" against strong acids. ASA rates higher against alkalis: "Good" for weak and "Fair" for strong, where PETG is "Fair" and "Poor." Bambu Lab's data sheets list Bambu ASA as "Resistant" to acid and alkali but "Not resistant to some kinds of oil and grease," and PETG Basic as "Not resistant" to acid and alkali but "Resistant to most kinds of oil and grease."

Solvents. Prusa says ASA "can be dissolved in acetone" and lists "Possibility of acetone smoothing and gluing" as an advantage. For PETG, Prusa says dissolving or smoothing "is possible only in a laboratory by skilled lab workers using dangerous chemicals (Dichloromethane)." Our ABS vs ASA guide covers acetone safety, and we don't publish smoothing instructions.

Layer bonding. Two makers' data point the same way. The Prusament data sheets give an interlayer adhesion of 18 ± 4 MPa for PETG and 11 ± 1 MPa for ASA. Bambu Lab's data sheets give a Z-direction impact strength (across layers, ISO 179) of 10.5 kJ/m² for PETG Basic and 4.9 kJ/m² for ASA. Both figures come from each maker's own test prints, so check the orientation of load-bearing parts either way. Our strongest filament guide explains why strength figures only compare well within one maker's data.

Side-by-side comparison

All figures are manufacturer-published values for specific products. Other brands and grades differ.

Who should choose which

Choose PETG if:

• Your printer is open-frame, including a Bambu A1, which Bambu says not to enclose.
• You can't provide the ventilation or filtration ASA makers call for.
• The part faces water, humidity, or partial sun rather than years of direct sunlight.
• You print large parts and want low warping without a heated chamber.
• You feed filament from a Bambu AMS lite.

Choose ASA if:

• The part will sit in direct sun for long periods and needs to keep its color and strength.
• The part will get warmer than PETG makers rate their material for.
• You have an enclosed printer and a ventilated space, or filtration your printer maker recommends.
• You want to acetone-smooth or solvent-glue parts and can do it safely.

Who should skip both

• The part is decorative and stays indoors at room temperature. PLA is easier. See PLA vs PETG or PLA vs ASA.
• The part needs more heat resistance than ASA offers. Look at the specialty filaments hub for polycarbonate and nylon, and check your printer's limits first.
• You need safety-critical, food-contact, or child-use parts. Neither material solves that.

Before you buy a spool

• Write down how much direct sun the part will see, and the highest temperature it will reach.
• For long outdoor life, check whether the exact product publishes weathering data.
• Check that your printer's hotend and bed reach the maker's recommended temperatures.
• For ASA, confirm your printer is enclosed and that its maker supports ASA on it.
• Plan ventilation separately from the enclosure.
• Check your build plate maker's guidance, especially PETG on smooth PEI.
• Plan drying and dry storage using the figures on your spool's data sheet, and check your spool's temperature rating.
• If you use an AMS or another automatic feeder, check the maker's compatibility list for that exact material.

Ready to choose? The ASA filament shortlist matches verified ASA spools to the printers they suit, with each maker's UV, enclosure, and drying guidance. The PETG filament shortlist compares verified spools from standard to high-speed grades on their makers' data. To see two ASA spools side by side, read Polymaker ASA vs OVERTURE ASA. If you're adding a box around an open printer, start with the printer enclosures shortlist, and check your printer maker's guidance first.

Specialty materials: what to check before you buy a spool ↗