Short answer: a Pi-and-screen kiosk drawing 15-25 W runs fan-cooled only under a roof or behind a sun shield. Direct sun adds 10-20 °C to a steel shell, and a Raspberry Pi 4 starts shedding core clock speed at 80 °C [176 °F], hard-capped at 85 °C. The decision therefore splits at about 30 °C ambient. Shaded or shielded, you ventilate and a modest fan wins. In open sun at 30 °C and up, you seal the box to IP66 and pump heat out with a thermoelectric cooler sized at 1.5-2× the electronics load. The worked example below uses a 16 x 12 x 8 in box, and the closing sections turn the arithmetic into the rating, the material and the order spec for each case.
The heat budget of a Pi kiosk
Every cooling choice follows from one number: the watts inside. Count them before you shop for fans.
A Raspberry Pi 4 draws about 3 W idle and 6-8 W under load. A 7-10 in touch screen with its driver board adds 5-10 W. A 5 V supply at 85% efficiency turns a 17 W electronics load into roughly 20 W of heat, so call the whole kiosk 15-25 W and you are within a few watts either way.
The limit that decides the design is the chip's, not the box's. Raspberry Pi's own documentation puts the throttle window at 80-85 °C [176-185 °F]: the cores shed clock speed across that band and hold the reduced speed at 85 °C. The air around the board has to sit well under that. With a small finned aluminum sink at about 5 K/W, 6 W of chip heat lifts the silicon 30 K over the surrounding air, so that air must stay below 50 °C for full speed. A blower-style case at about 3 K/W cuts the lift to 18 K and raises the air ceiling to 62 °C.
The sun eats part of that margin before your electronics contribute anything. The solar heat load and temperature rise article walks the wall-by-wall numbers for a box standing in the open.
What the sun does to a steel shell
Clear-sky solar irradiance at ground level peaks near 1000 W/m² at noon. How much of that the wall soaks up depends on the finish: solar absorptance runs about 0.4 for bright stainless and about 0.85 for dark paint, so the same sun puts 400 W/m² into a bright wall and 850 W/m² into a dark one. Enclosure thermal guides publish the outcome as a 10-20 °C rise over ambient in full sun, with bright shells at the bottom of the band and dark shells at the top.
That rise lands on the shell before any of your 20 W shows up. It is why a fan sized for the electronics alone still cooks the board at noon.
The worked example: a 16 x 12 x 8 in box at 35 °C
Take the box a countertop kiosk actually needs: 16 x 12 x 8 in [406 x 305 x 203 mm] stainless, 0.54 m² of wall area, 20 W inside, 35 °C ambient, unobstructed sun.
- Shell. 35 °C + 15 °C of mid-band solar rise = 50 °C at the wall. A dark shell trends to 55 °C, a bright one to 45 °C.
- Fan and vents. 20 CFM is 9.4 L/s of air, and air carries about 1.2 J per litre per kelvin. The load warms that stream by 20 ÷ (1.2 × 9.4) = 1.8 K, so the fan handles the electronics with ease. But it inhales 50 °C air off the hot shell, and the inside sits near 52 °C.
- The chip. 6 W through a 5 K/W sink adds 30 K: 52 + 30 = 82 °C, past the 80 °C throttle point. The Pi clocks itself down at noon.
- Add a sun shield. A published enclosure test with shields over the top and sides measured about a 46% cut in the sun-driven rise. Fifteen kelvin becomes 8 K: the shell sits at 43 °C, the air at 45 °C, the chip at 75 °C. Full speed holds, with 5 K to spare.
- Seal it for rain. Through stainless walls, 20 W moves at k = 3.7 W/m²K × 0.54 m² = 2.0 W/K, so sealed air runs 20 ÷ 2.0 = 10 K over the shell. That is 60 °C unshielded and 53 °C shielded. The sealed unshielded box fails at this ambient whatever sink you fit; the shielded sealed box holds with a 3 K/W board cooler (53 + 18 = 71 °C) and throttles with a 5 K/W one (53 + 30 = 83 °C).
Every path through the arithmetic says the same thing: at 35 °C in open sun the shield is not optional, and above about 30 °C ambient passive cooling survives only on a good board cooler.
Where fans and vents are enough
Under a roof, in an alcove or against a shaded wall, ambient is the whole story, and a fan carries the load up to about 30 °C. Budget roughly 0.4 CFM per watt for a 5 K rise: a 20 W kiosk needs about 7 CFM, so a 20 CFM fan doubles the margin. Mount one fan low and one high on opposite walls so air crosses the board instead of sliding past it.
Then keep the rating honest. Every vent and fan opening drops the assembly to that part's rating. Filtered fan vents of the kind kiosks use hold about IP54: dust-protected (first digit 5), splashing water (second digit 4), no hose jets. A kiosk under an awning can live with that. A kiosk that rain or washdown reaches cannot, because IPX5 jets run 12.5 L/min and IPX6 runs 100 L/min under IEC 60529, and a vent passes neither. If rain is in the picture but you still want moving air, a sealed cooling unit with an isolated impeller passes the heat through the wall without openings and keeps IP66 intact.
The sun shield: the cheapest margin on the list
A shield is sheet metal standing off the box, open at the ends so wind and convection strip the heat. Give it a 2 in [50 mm] air gap over the roof and down the sun-facing sides; the gap is what makes it work, because the shield's own heat never reaches the shell. Cover the roof first, since it takes the full 1000 W/m² at noon, then the west and south faces, which catch the low afternoon sun.
The measured 46% cut is worth 7 K in the worked example: it is the distance between 75 °C at the chip and a throttled kiosk. A bright finish does the same job by subtraction, taking a sun-facing wall from 850 to 400 W/m² of absorbed load. For the geometry, see how a sun shield cuts solar heat load and the solar shield numbers article, and the sun shield install guide for an outdoor instrument walks the standoff and fixings step by step.
Sealed and active: thermoelectric cooler or mini AC
Seal the box and the question becomes how many watts you can pump out. Size the cooler at 1.5-2× the electronics load: a 60-100 W class thermoelectric cabinet cooler covers a 20-25 W Pi kiosk with margin. Count the electrical draw too, because a unit in that class pulls roughly 60-80 W whenever it runs — a real line item on a solar-battery kiosk.
Condensation is the failure mode to design out. A cold plate sits below the inside-air dew point on humid days, and the water it wrings out drips onto the board; set the thermostat a few kelvin above the dew point and read the thermoelectric condensation article before you hang the cold side over the electronics. A kiosk running 24/7 carries 20 W of self-heat, which keeps most night-time condensation down. A kiosk that sleeps on a schedule does not, and that is where an anti-condensation heater earns its slot.
Above about 60 W of load, or whenever the inside air must sit well below ambient for hours, a compact compressor unit is the better machine. A unit sized for this duty draws 300-600 W and needs a condensate drain and service clearance, and its evaporator obeys the same dew-point rule. The thermoelectric vs air conditioner article lays out the crossover.
Rating, material and finish
Rain-exposed kiosks get a manufacturer-rated NEMA 4X / IP66 enclosure; not UL listed. The two sixes mean dust-tight, plus powerful jets from a 12.5 mm nozzle at 100 L/min under IEC 60529, and NEMA 250 adds a 200-hour salt-spray evaluation for the X. In US installations, NEC 110.28 states that IP ratings are not a substitute for enclosure type ratings, so carry both markings on the spec. The NEMA 4 vs 4X vs IP66 guide and the IP rating chart map the pairs and the digits.
Material follows the site. 304 covers most outdoor addresses; 316L earns its keep near salt water, de-icing salt or sanitizer mist. Heat raises the stakes: chloride stress-corrosion cracking starts near 60 °C for both grades, and a dark unshielded shell in still air can pass it. Molybdenum in 316L buys pitting and crevice resistance; it does not move that threshold. The bright finish and the shield do, by keeping the wall under 50 °C.
Remember the weakest part when you add hardware. A display's front gasket, a gland on the wrong cable diameter or an unrated cooler cutout sets the whole assembly's rating.
Screen, size and the housing route
A Pi kiosk is a custom box: the window, the gland holes and the standoffs are cut to your parts. The enclosure sizing guide gives the size rules, and the cutouts, glands and windows guide covers window tolerances. Two rules carry most of the value: keep 1 in [25 mm] of clearance around the screen window for its gasket and fasteners, and put the Pi, the supply and the evaporator on a removable panel, so service means four screws. Isolate the supply and verify absence of voltage before you open a kiosk that is powered.
If you can swap the Pi and its screen for an industrial panel PC, the housing problem is already solved. Our HMI housing for a 15 in panel PC or HMI housing for a 21.5 in panel PC is 304 stainless with a gasketed rear cover and an IP65-type front seal once the display is installed, manufacturer rated — see the HMI enclosures line for the full size list.
The decision, by case
| Site | Ambient | Cooling that holds the chip under 80 °C | Assembly rating |
|---|---|---|---|
| Under a roof or awning | up to 30 °C | 20 CFM fan plus filtered vents (0.4 CFM/W rule) | IP54-type — the vent's rating |
| Outdoor, rain and sun | up to 30 °C | Sealed, sun-shielded, passive; Pi on a 3 K/W board cooler | NEMA 4X / IP66, manufacturer rated |
| Outdoor, rain and sun | 30-40 °C | Same shell plus a 60-100 W thermoelectric cooler, set just above the dew point | IP66 throughout, cooler included |
| Load above about 60 W, or a below-ambient set point | any | Compact compressor AC, 300-600 W draw, with drain and service clearance | IP66 throughout, unit included |
A 5 K/W sink ends the passive window near 30 °C ambient; the 3 K/W board cooler stretches it to about 38 °C (38 + 8 + 10 + 18 = 74 °C at the chip). Past that you are buying a cooler no matter what the fan catalog says.
What to put on the order
| Line | Spec |
|---|---|
| Shell | 304 stainless wall-mount, or 316L by the coast; custom size — the worked example is 16 x 12 x 8 in [406 x 305 x 203 mm] |
| Rating | Manufacturer-rated NEMA 4X / IP66; not UL listed |
| Cutouts | Screen window to the display drawing; two M20 [0.79 in] cord-grip gland holes; a sealed breather where ambient stays under 30 °C |
| Cooling | Passive and shielded at or below 30 °C ambient; a 60-100 W thermoelectric cooler cutout above it |
| Interior | Removable mounting panel, Pi on 0.25 in [6 mm] standoffs, DIN rail for the 5 V supply |
Custom sizes and cutouts run from your drawing to the shop and back to you delivered in 10 business days, anywhere in the world, counted from your approval of the drawing. Size the box in the stainless enclosure line, send the screen drawing with the quote, and the kiosk arrives as one finished part.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 15" HMI enclosure | 304 stainless | 12.91 x 16.06 x 3.88 in | IP65-type front seal with the display installed, manufacturer rated; not UL listed |
| 21.5" HMI enclosure | 304 stainless | 14.69 x 23.03 x 3.86 in | IP65-type front seal with the display installed, manufacturer rated; not UL listed |
| 16 × 12 × 8 in | 304 stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 24 × 20 × 8 in | 304 stainless | 24 x 20 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Can a Raspberry Pi run outdoors without active cooling?
Yes, when the box is shaded or shielded and the load is modest. A Pi 4 with a screen draws 15-25 W; behind a shield that cuts the solar rise about 46%, a 35 °C day leaves inside air near 45 °C, and a Pi on a 5 K/W sink sits at about 75 °C, under the 80 °C throttle. In open sun the same fan-vented box breathes 52 °C air and the chip lands at 82 °C, throttled.
At what temperature does a Raspberry Pi start to throttle?
A Raspberry Pi 4 lowers its core clocks progressively between 80 and 85 °C [176-185 °F] and holds the reduced speed at 85 °C. With a 6 W chip on a 5 K/W heatsink, the air around the board must stay below 50 °C for full speed; a 3 K/W blower case raises that ceiling to 62 °C. Aim for inside air of 45-50 °C with a finned sink, and up to 60 °C with a blower case.
How much heat does a Pi kiosk with a screen put out?
Count 15-25 W for the kiosk: a Pi 4 draws about 3 W idle and 6-8 W under load, a 7-10 in touch screen adds 5-10 W, and an 85%-efficient 5 V supply adds roughly 3 W more. Twenty watts through the 0.54 m² wall of a 16 x 12 x 8 in stainless box lifts sealed inside air 10 K over the shell.
How much does a sun shield cut enclosure temperature?
In a published enclosure test, shields over the top and sides cut the sun-driven rise by about 46%. For a steel shell that runs 15 °C over ambient in full sun, that turns a 50 °C wall on a 35 °C day into roughly 43 °C — the margin that keeps a 20 W Pi kiosk off its 80 °C throttle with no refrigeration. Leave a 2 in [50 mm] air gap over the roof and sides so convection can strip the heat.
Do vent holes keep an outdoor enclosure's IP rating?
Only if each opening carries a rating of its own: the weakest part sets the assembly rating. A plain drilled hole ends it; filtered fan vents of the kiosk kind hold about IP54 — dust-protected, splashing water, not hose jets (IPX5 jets run 12.5 L/min, IPX6 runs 100 L/min under IEC 60529). For IP66, use sealed breathers and a sealed cooling unit with an isolated impeller, or no openings plus a thermoelectric cooler.
Thermoelectric cooler or mini AC for a Pi kiosk?
Below about 60 W of load, a thermoelectric cabinet cooler wins: no compressor or refrigerant, and a 60-100 W unit covers a 20-25 W kiosk at 1.5-2× sizing. Above that, or when inside air must sit well below ambient for hours, a compact compressor unit is the better machine; it draws 300-600 W and needs a condensate drain and service clearance.
