# Temperature: how warm a room feels, not just reads > How heat moves, why the same reading can feel warm or cold, and how layout and shading keep a room comfortable. Source: https://guide.rayon.design/knowledge/foundations/temperature · Foundations · Updated 2026-10-18 © 2026 Rayon. Quote short excerpts with a link to the source page. Full terms: https://guide.rayon.design/about ## Introduction A thermostat reads one number, but a room is a mix of temperatures: warm air, cold glass, a sunlit floor. Learn how heat moves, why the same reading can feel warm in one room and cold in another, and how [layout](https://guide.rayon.design/knowledge/foundations/use), materials and [shading](https://guide.rayon.design/knowledge/foundations/light) keep a home comfortable through the year. ## Temperature basics What temperature is and how we measure it. Temperature says how hot or cold something is, in degrees Celsius (°C) or Fahrenheit (°F). In a room, the air and every surface have their own temperatures. A thermostat measures only the air near its sensor, so it misses what a person actually feels: a cold window, a sunlit floor or a warm ceiling changes comfort while the air stays the same. Read temperatures where people actually sit and stand, away from direct sun and heat sources. *Interactive diagram:* One room, four temperatures: the air the thermostat reads, the cold window, the wall and the floor in the sun. *Point at the air, the window, the wall or the sunlit floor to read its temperature. One room, four numbers.* ### Living rooms **20–22 °C** For sitting still in everyday clothes. ### Bedrooms **16–19 °C** Cooler air helps sleep, under covers. ### Humidity **40–60 %** Relative humidity that feels fresh and keeps mould away. ## How heat moves Why rooms warm up and cool down. Heat always flows from warmer to cooler, in three ways. **Conduction** carries it through materials, such as a wall or a window. **Convection** carries it between surfaces and moving air, such as the warm air rising off a radiator and circling the room. **Radiation** carries it between surfaces with no contact at all, such as a person losing warmth to cold glass across the room. Sunlight, people, lamps and appliances add heat; the walls, windows and fresh air add or remove it depending on the weather. A room’s temperature is the balance of all of these. *Interactive diagram:* Heat flows through the glass itself, from the warm room to the cold outside. ### Conduction Through materials. Heat passes through the glass, from the warm room to the cold outside. *Interactive diagram:* Air warmed by the radiator rises, crosses the ceiling, cools, sinks and returns along the floor. ### Convection Through moving air. Air warmed by the radiator rises, cools against the glass and sinks again. *Interactive diagram:* The person loses heat straight to the cold glass, with nothing touching in between. ### Radiation Across space, with no contact. A person loses warmth to cold glass across the room. ## Thermal comfort Why the same temperature can feel different. Comfort depends on more than the air. The surfaces around us exchange heat with our bodies by radiation; moving air takes heat away faster; humidity changes how easily sweat evaporates; and clothing and activity change what feels right. [Operative temperature](https://guide.rayon.design/lexicon/operative-temperature) combines the air temperature with the [mean radiant temperature](https://guide.rayon.design/lexicon/mean-radiant-temperature) of the surroundings, which is why two rooms with the same thermostat reading can feel different. Local conditions matter too: a draught at the ankles or sun falling on one person can make part of a comfortable room uncomfortable. *Interactive diagram:* Beside a large cold window, the person loses heat to it by radiation, and feels cooler than the air. ### Beside cold glass The air is 21 °C, but the person loses heat to the cold window and feels cooler. *Interactive diagram:* Among warm walls, the person gains heat from them by radiation, and feels warmer than the air. ### Among warm walls The air is 21 °C too, but warm surfaces give heat back and the person feels warmer. ## Designing for temperature Using layout, materials and controls to improve comfort. Control unwanted sun with shading, ideally outside the glass, where it stops heat before it enters. Place seating away from cold glazing, hot surfaces and draughts, and keep radiators, supply outlets and return grilles clear of furniture and curtains. Put thermostats and blind controls where people can reach and understand them. Insulation slows heat flow through the envelope. [Thermal mass](https://guide.rayon.design/lexicon/thermal-mass), such as stone, concrete or brick, stores heat and gives it back later, evening out the swings between day and night. Ventilation cools a room when the outside air is cooler, but adds heat when it is warmer. Design for every season, and give people simple ways to adjust. *Interactive diagram:* The awning reaches out and stops the high sun before it enters, the window stands open for air, and the chair can sit by the window. ### Summer Shade the glass from outside, open windows when the air outside is cooler, and use thermal mass to soak up the day’s heat. *Interactive diagram:* The awning folds back so the low sun reaches deep into the room, the window closes, and the chair moves away from the cold glass. ### Winter Let low sun in, close up and seal draughts, and move seating away from cold glass. Never block a radiator with a sofa or long curtains. ## Questions What people ask most about indoor comfort. ### What is room temperature? Room temperature usually means about 20–22 °C, the range most people find comfortable sitting still indoors in everyday clothes. Bedrooms feel better a little cooler, around 16–19 °C. What you feel also depends on the surfaces around you, draughts, humidity and clothing. ### What should the humidity be in a house? Aim for 40 to 60 percent relative humidity. Below about 30 percent, air feels dry and static builds up; above 60 percent, condensation, mould and dust mites become likely. In cold winters, 30 to 40 percent avoids condensation on windows. ### How do I lower the humidity in a house? Remove moisture where it is made: use extractor fans while cooking and bathing, dry clothes outside or in a vented dryer, and open windows briefly to air rooms. Keep rooms evenly heated, avoid blocking radiators, and use a dehumidifier in damp rooms or basements. ### What should I set my thermostat to in winter? About 20 °C when you are home and awake suits most people, with 16–18 °C overnight and when you are out. Each degree lower saves noticeable energy. Avoid turning it off completely in very cold weather, to protect pipes and prevent condensation. ### What is radiant heat? Radiant heat warms people and surfaces directly, without heating the air first, the way the sun warms your face on a cold day. [Underfloor heating](https://guide.rayon.design/lexicon/underfloor-heating), radiant panels and warm walls work this way. It feels comfortable at a lower air temperature and avoids draughts. ### How do I keep a house cool without air conditioning? Block the sun before it reaches the glass, with external shades, awnings or shutters, and close curtains on sunny windows during the day. Open windows on opposite sides at night to let cool air through, use ceiling fans, and switch off heat sources such as lamps and appliances. ### How do I increase the humidity in a house? Use a humidifier in the rooms you spend most time in, dry laundry indoors on a rack, and add plants. Lowering the heating slightly also helps, because warmer air feels drier. Keep humidity below 60 percent to avoid condensation. ### What is a smart thermostat? A smart thermostat controls your heating or cooling from a phone app and learns your routine. It can lower the temperature when you leave, warm the house before you return, and control rooms separately. Most save energy by heating only when and where it is needed. ### How do I keep a baby's room cool? Keep the room at about 16–20 °C. Shade the window during the day, air the room in the cool evening, and use a fan to move air, never pointed directly at the baby. Dress the baby in light layers and use a room thermometer to check. ### What causes high humidity in a house? Everyday activities release moisture: cooking, showers, drying clothes and breathing. Poor ventilation keeps it inside, and cold surfaces make it condense. Leaks, rising damp and unvented appliances add more. Better extraction, steady heating and fixing water leaks bring it down.