Schools feel cold for a combination of reasons: aging buildings with poor insulation, HVAC systems designed to prioritize ventilation over comfort, high ceilings and concrete construction that absorb heat, and temperature settings that aim for a cool-side sweet spot where students concentrate best. The standard comfort range for occupied buildings is roughly 73°F to 79°F (23°C to 26°C), but many classrooms fall well below that, especially in winter.
Ventilation Rules Push Temperatures Down
Schools are required to circulate far more fresh outdoor air than most other buildings. Classrooms pack 20 to 30 people into a relatively small space, and without constant air exchange, carbon dioxide levels climb quickly, making students drowsy and unfocused. To keep air quality safe, HVAC systems pull in large volumes of outside air, filter it, and push it into classrooms.
The problem is that heating or cooling all that incoming air takes enormous energy. On a cold winter day, the system may not be able to warm outdoor air fast enough before it reaches the classroom. Harvard’s Healthy Buildings program has noted that mechanical ventilation systems sometimes can’t sufficiently heat or cool outside air before blowing it into classrooms during temperature extremes. The result is a steady stream of cool air flowing from ceiling vents, even when the thermostat says the room should be comfortable. If your school opens windows for additional ventilation, the effect is even more pronounced.
Concrete and Brick Absorb Your Warmth
Most schools are built from concrete block, brick, and tile, materials chosen for durability and fire resistance rather than coziness. These materials have high thermal mass, meaning they absorb heat from the surrounding air and release it slowly. In winter, the walls, floors, and ceilings of a concrete school soak up warmth like a sponge, making the room feel colder than the air temperature alone would suggest. You’re essentially trying to heat a massive block of stone every morning.
Research on school buildings in temperate climates found that classrooms with insulated concrete panels maintained temperatures at or above 64°F (18°C) for 34% more of the school day compared to classrooms without that insulation. Buildings with proper thermal mass and insulation together can raise average winter indoor temperatures and reduce the wild temperature swings that leave students shivering during first period and overheating by lunch. But many schools, particularly older ones built decades before modern energy codes, lack that insulation layer entirely. The concrete just conducts cold straight through.
Old Buildings, Outdated Systems
A large share of school buildings in the U.S. are 50 or more years old, and their heating systems reflect it. Many run on centralized boiler systems that send steam or hot water through the building on a single thermostat schedule. Individual classrooms rarely have their own temperature controls. A room on the sunny south side of the building might be 75°F while a north-facing room down the hall sits at 62°F, and the system has no way to treat them differently.
Drafty windows, gaps around doors, and minimal wall insulation make things worse. Single-pane windows, still common in older schools, lose heat at roughly twice the rate of modern double-pane glass. Budget constraints mean these systems often go decades between major upgrades. When something breaks, schools patch rather than replace, leading to uneven heating where some zones are neglected while others are over-served.
Cooler Classrooms May Be Intentional
Here’s the part that might surprise you: slightly cool classrooms actually help students think. Research on cognitive performance found that school tasks improved by roughly 20% on average when classroom temperatures dropped from 86°F to 68°F (30°C to 20°C). The sweet spot for mental performance appears to be below about 72°F (22°C). At temperatures in the low 70s, students made fewer errors on memory and complex reasoning tasks compared to warmer conditions.
When classrooms get warm, students make more mistakes and rush through work. One study found that error rates on attention tasks increased by about 11% when temperatures rose from 68°F to 77°F (20°C to 25°C). Researchers observed that students in uncomfortably warm rooms tried to finish tests as quickly as possible just to escape the environment. So facility managers who keep buildings on the cool side aren’t being stingy; they may be following guidance that favors alertness over warmth.
That said, there’s a lower limit. At around 68°F, hand dexterity starts to decline as joints stiffen and muscular reactions slow. Students writing or typing in a room much below that temperature work more slowly, not because they’re less focused, but because their fingers literally don’t cooperate as well.
Low Humidity Makes It Feel Colder
During winter, heated indoor air loses moisture rapidly. Relative humidity in schools can drop to 20% or lower, well below the 40% to 60% range considered comfortable. Dry air pulls heat from your skin faster through evaporation, making 70°F air at 20% humidity feel noticeably colder than 70°F air at 45% humidity. This is why a classroom can feel frigid even when the thermostat reads a perfectly reasonable number.
Schools with well-insulated, high-thermal-mass construction maintained humidity in the optimal 40% to 60% range for about 21% more of the school day than poorly insulated buildings. But most schools don’t have humidification systems, so in cold, dry months, there’s nothing counteracting the dryness. The combination of moderate air temperature and very low humidity creates that particular brand of school cold: not freezing exactly, but persistently uncomfortable in a way that’s hard to pin down.
No Federal Standard Requires a Minimum
You might assume there’s a law requiring schools to keep classrooms above a certain temperature. There isn’t. No federal OSHA heat standard exists, and few school districts have mandated temperature maximums or minimums. Individual states and districts set their own guidelines, and enforcement varies wildly. Some states require classrooms to stay above 65°F or 68°F; others have no rule at all.
This regulatory gap means that when a school’s heating system underperforms, there’s often no legal mechanism forcing a rapid fix. Teachers and students in buildings where temperatures regularly dip into the low 60s or upper 50s may complain, but without a binding standard, repairs compete with every other budget priority. The absence of regulation also means there’s no systematic tracking of classroom temperatures, so the scope of the problem is largely invisible at a policy level.
Cold Classrooms and Student Health
Beyond discomfort, persistently cold classrooms carry real health implications. Research examining school environments found that low indoor temperatures amplified the respiratory health risks associated with air pollution, leading to higher rates of student absences due to pneumonia and respiratory infections. The effect was cumulative: the longer students were exposed to cold conditions combined with poor air quality, the greater the risk. These associations were strongest in urban schools where outdoor pollution levels were already elevated.
Cold air also dries out mucous membranes in the nose and throat, reducing the body’s first line of defense against viruses. In a room full of students sharing air, that diminished barrier matters. Schools that struggle to maintain comfortable temperatures often also struggle with ventilation and humidity, creating a triple threat of cold, dry, poorly circulated air that is ideal for spreading respiratory illness.