Do chickens need a heat lamp in winter?

Winterizing is drafts, water, bedding, and air. Adult heat is where the extension pages disagree. The numbered brooder schedule is still for chicks.

Built by Jeremy Panasuk. Updated October 6, 2026.

Moisture is the winter problem these pages describe

The housing pages cited here treat damp, poorly ventilated air as the winter problem, not a missing heat lamp. Sealing a coop traps moisture from breath and droppings. A heat lamp is a fire risk; these pages do not count coop fires against cold losses, and they do not publish an adult temperature such as −10°F or −20°F. If the power fails, birds that were depending on a lamp lose that heat at once.

How to winterize the coop

Start with the shell. Maryland's winter fact sheet says to fix leaking roofs and the cracks that let wind blow on the birds, because moisture raises ammonia and damp air feels colder. Holes can be filled with spray foam or covered with a heavy plastic sheet. Ohio says to find those holes before winter: lights on inside, walk the outside in the dark, and keep foam and caulk where the chickens cannot peck it. A tarp over an open side can block ground-level wind. Ohio says the tarp should not run all the way to the roof, or the coop stops exhausting moisture.

Roosts are part of the winter setup, and the lengths disagree, so they stay separate. Minnesota says roosts generally start at least 12 inches off the floor and give 9 inches per chicken, on wood (a 2×4 or 2×2), not metal or plastic, so birds can sit on their feet. Ohio says at least 6 to 8 inches of roost per chicken and a bar 1½ to 3 inches in diameter, with every bird able to get off the floor at night. The year-round inch ranges are on the roost page.

Bedding is also two published depths. Minnesota's deep-litter option is 4 to 6 inches of straw or shavings: stir the soiled top down and add a clean layer, with a 6- to 8-inch kickboard at the door if the bedding would otherwise spill. Maryland says 3 to 4 inches of pine shavings or straw, which insulates and also makes some heat as microbes break it down. Ohio says to remove the old bedding and start winter with a deep layer of dry material, then fluff it, because deep bedding can raise humidity. Minnesota says chicken manure is 70 percent water, so trays under the roost, or picking up the wet spots, are the moisture control. If you smell ammonia, or moisture is beading on windows, Minnesota says to add ventilation and clean the manure.

Water has to stay liquid. Maryland says frozen water is unavailable water, and birds will not break the ice. Check and replace it through the day, or use a base heater, and do not splash cold water on a hot lamp because the bulb can shatter. Minnesota lists heated founts, heated bases, and a covered heated dish so birds do not step in or drown, with the water on a stand and the cord off the bedding. Have a second waterer. Daily gallons, as opposed to "is it frozen," are on the water page.

Feed intake in cold weather is another split. Minnesota says a flock's feed intake may increase up to 25 percent, so keep extra feed and refill the feeders, and offer grit because snow cover stops birds from finding stones. Ohio says chickens eat less in winter than in summer, and that each laying chicken requires 2 pounds of feed per week. This site's feed function stays at 0.25 lb per hen per day and does not apply either sentence. The worked feed example is on the feed cost page. Minnesota caps scratch at a handful per 10 birds. Maryland's winter sheet caps treats and scratch at 10 percent of total feed, fed in the evening. Missouri says temperatures under 15°F usually slow or stop egg production, and temperatures around 10°F will probably freeze combs or toes. Those are production and frostbite lines, not a wattage.

Frostbite care is also specific. Minnesota says petroleum jelly on combs and wattles can help insulate them and does not treat frostbite that is already there. Call a veterinarian for frostbite or infection. Move a pecked bird out until it recovers. Ohio says warm a frostbitten bird slowly, use warm (not hot) water on feet only, and do not rapid-warm the tissue. Contact a veterinarian if you suspect infection.

Fans and ventilation

The backyard pages describe openings, not a fan rating. Ohio says most breeds can take cold, including temperatures below freezing, and that the damage comes when wind and moisture arrive with the cold. Block drafts. Keep ventilation. A sealed coop builds ammonia from the litter and humidity that makes frostbite more likely. Maryland says incoming air has to mix with the warmer air already in the building before it reaches the birds, and that a vent near the roof or ceiling is what lets ammonia and stale air out. Minnesota's list is a partly open south window, roof vents, burlap over an open window, and a small door or window on warmer winter days.

Missouri is the page that names a fan: a circulating ceiling fan can move air in large houses, along with curtains or windows as the fresh-air source. It also says to keep the house free of drafts. It does not publish a cubic-feet-per-minute number for a backyard coop, and this page does not borrow one from a commercial poultry-house bulletin.

Worked example: a 24 sq ft coop

Inputs to calcHeat: 24 square feet of floor, a winter low of 28°F, chicks set to no. The function's adult line is "below 20°F." Twenty-eight is not below 20, so adult watts are 0. Vent area is the site ratio, about 1 sq ft per 10 sq ft of floor, in half-foot steps: 24 / 10 = 2.4, which lands on 2.5 sq ft. The same floor at a 10°F low does cross the site line. Adult watts are 24 × 250 / 16 = 375, rounded up to the next 50 W, which is 400 W. Chick watts on a 16 sq ft cap are 250 W either way. None of those watts are in the Minnesota, Maryland, or Ohio pages.

Read 28°F against the sources, not against the function. Minnesota's instruction is supplemental heat when the coop is below 35°F, so 28°F is inside that instruction even though the calculator prints "no adult watts." Maryland still says wind-protected, dry adults should not need added heat. Ohio still says a dry, insulated, acclimated, cold-tolerant flock usually does not. The calculator is a third number. Use it to see the site's own planning watts. Do not treat 20°F or 400 W as the extension answer. Bantams are the exception Maryland does name: they produce less heat than large fowl and may need supplemental heat while the large birds look comfortable. Molting hens may need extra heat or protection until the feathers return.

Run the heat function

Minnesota's 35°F line is applied in the note as a comparison with the temperature you typed. It is not inside calcHeat.

Common mistake

Closing every opening, including the high vent, because the coop feels cold. Ohio's draft control stops short of the roof on purpose. Minnesota's ammonia test is the correction: if you smell it, you need more air and less manure, not a tighter door. The other mistake is hanging a heat lamp by its cord, or running the coop on an extension cord. Minnesota says never hang a lamp by the cord, keep wires away from birds, water, and litter, use extension cords only short term, and hire a professional electrician to install power in the coop. If that circuit is solar, panel sizing is a separate job: SolarSizer. Maryland's lamp clearance, at least 18 inches off the floor, is in the next section.

Limits, and when to call someone

Frostbite, a bird that is losing a comb or a foot, or an infection on damaged tissue is a veterinarian call. Minnesota says petroleum jelly does not treat frostbite. Electrical work in the coop is an electrician's job. These pages do not publish a safe DIY wattage for a given coop, and the 400 W figure above is this site's rounding of its own ratio. Chick brooding is the case where a lamp is required. The feed amounts and the floor space for those chicks are on the baby chick page.

Ventilation planning ratio

Maryland says to use 1/2-inch hardware cloth over windows. Put vents above roost height and out of the wind. Condensation on the glass in the morning means the air is too wet. Lighting figures that Maryland does publish — one 25-watt bulb for 40 square feet, or one 40-watt bulb for 200 square feet — are on the flock-size page, in the 200 sq ft lighting section.

If you still add a lamp

The 250 W per 16 sq ft figure in the worked example is this site's ratio, not a bulb size from these pages. If you add a lamp because Minnesota's coop is below 35°F, because Maryland's note on bantams or a molting hen applies, or because a bird is ill, Maryland's clearance is at least 18 inches above the floor. Secure the lamp. Keep the coop dry. Minnesota says not to hang it by the cord.

Brooder math (this is where lamps are required)

Maryland Extension: start chicks at 90–95°F the first week, then reduce 5°F each week until they are five weeks old and the room is about 70–75°F. The lamp should be at least 18 inches above the floor. Watch the chicks: panting and crowding away from the lamp means too hot; a tight huddle under the lamp means too cold. These pages do not assign a 250 W bulb to a 4×4 ft brooder or a 100 W bulb to a 2×2 ft brooder.

The steps below start at 95°F, the top of Maryland's 90–95°F first week, then drop 5°F a week through week 5, when Maryland says the house is about 70–75°F. Chick behavior is on the paragraph above. This table does not add a temperature Maryland did not publish.

As an Amazon Associate I earn from qualifying purchases. The Amazon links below are affiliate links; they don't change the math.

If you rely on supplemental electric heat, outage planning starts with what size generator runs a space heater in an outage.

FAQ

How cold is too cold for chickens?

Minnesota Extension says to provide supplemental heat when the coop falls below 35°F. Maryland's winter fact sheet says adult birds protected from wind and wet weather should not need additional heat. Ohio State says cold-tolerant breeds in a dry, insulated, ventilated coop do not usually need it. This site's calculator turns adult watts on only below 20°F, at 250 W per 16 sq ft. That cutoff and those watts are site planning.

How much ventilation does a chicken coop need in winter?

These extension pages do not publish a backyard fan size or a cubic-feet-per-minute rate. Ohio says not to seal the coop when you block drafts. Minnesota says to open more ventilation if you smell ammonia. This site's planner uses about 1 sq ft of high opening per 10 sq ft of floor. That ratio is site planning.

What wattage heat lamp for a chick brooder?

Maryland Extension starts chicks at 90–95°F the first week and drops 5°F each week until they are five weeks old, with the lamp at least 18 inches above the floor. These pages do not assign a wattage to a floor area.

Compiled with AI assistance from the sources below. Spot an error? Email jpanasuk@gmail.com.

Sources

• University of Minnesota Extension, "Caring for chickens in cold weather" (reviewed 2026). https://extension.umn.edu/poultry/caring-chickens-cold-weather. Accessed Oct 3, 2026.
• University of Maryland Extension, "Winter Weather and Small Flocks: What You Need to Know," FS-1133 (updated January 27, 2023). https://extension.umd.edu/resource/winter-weather-and-small-flocks-what-you-need-know-fs-1133. Accessed Oct 3, 2026.
• Ohio State University Extension, "Winter and Your Backyard Chickens," ANR-66 (December 19, 2018). https://ohioline.osu.edu/factsheet/anr-66. Accessed Oct 3, 2026.
• University of Missouri Extension, "Small Flock Series: Managing a Family Chicken Flock," G8350 (reviewed September 2017). https://extension.missouri.edu/publications/g8350. Accessed Oct 3, 2026.
• University of Maryland Extension, "Housing Requirements," for the brooder schedule (90–95°F, then 5°F less each week) and the 18-inch lamp clearance. https://www.extension.umd.edu/resource/housing-requirements.