Households can maintain indoor temperatures of around 20 degrees Celsius without turning on heating by applying basic physics principles, according to Zbynek Svoboda, an associate professor at the Czech Technical University in Prague.
Writing for Czech energy publication energozrouti.cz, Svoboda explained that daytime temperatures often remain around 20 degrees Celsius after the first cold autumn nights. As a result, residents do not need to rush to switch on their heating systems.
Svoboda, who teaches at the university's Faculty of Civil Engineering, said that a household's internal temperature depends on the balance between incoming heat and heat escaping through windows, doors, walls, and ventilation. By controlling heat loss and capturing solar radiation during transitional autumn weather, occupants can keep their homes comfortable for longer.
The Czech Technical University in Prague, founded in 1707, is one of the oldest technical institutes in Europe and a major research center for structural engineering and building physics. Svoboda's advice focuses on using natural thermal dynamics rather than consuming additional gas or electricity.
Solar heat management during daytime hours
To maximize natural heating during sunny autumn days, Svoboda advised residents to open curtains, pull back shutters, and raise window blinds completely. Solar radiation passing through window glass directly warms floors, walls, and furniture, which then store the energy and gradually release heat back into the indoor air.
Windows facing south and south-west receive the highest amount of solar energy throughout the day, though Svoboda noted that windows on all sides of a building should be unblocked during sunny hours. The overall heating effect depends on window size, building insulation, orientation, and total daily sunshine hours.
While sunlight may not raise room temperatures by several degrees, Svoboda said it significantly slows the rate at which an apartment cools down after a chilly night.
Draught prevention and evening window insulation
Once the sun sets, windows cease to provide solar heat gains and become primary pathways for thermal loss. Svoboda recommended drawing heavy curtains and closing blinds as dusk approaches to create an insulating air pocket between the glass and the living area.
However, curtains must not be allowed to hang over active radiators. Covering a radiator restricts warm air circulation, preventing heat from spreading efficiently through the room.
Svoboda also urged householders to inspect window frames, doors, and roller blind housings for air leaks. Cold draughts caused by dried, cracked, or displaced rubber seals should be addressed by replacing the damaged sealing strips.
For gaps beneath exterior doors, temporary draft stoppers or door snakes can effectively block cold air infiltration during windy weather.
Safe ventilation and room temperature guidelines
Svoboda cautioned against sealing up essential ventilation openings designed for fuel-burning appliances such as boilers, gas stoves, and fireplaces. Blocking these vents starves appliances of oxygen and can cause a dangerous buildup of carbon monoxide, a toxic, odorless gas.
Proper ventilation remains necessary even in cold weather to prevent moisture buildup from cooking, showering, and drying clothes inside. Svoboda advised against leaving windows tilted open for extended periods, recommending instead that windows be opened fully for a few minutes several times a day to create a rapid air exchange.
Indoor layout also affects thermal comfort. Svoboda suggested moving sofas and armchairs away from cold exterior walls or windows, and placing rugs over cold tiled floors to reduce radiant heat loss from the body.
During sunny hours, internal doors to warm rooms should be left open to let heat circulate. In the evening, doors to cooler rooms should be kept closed to preserve warmth in occupied spaces.
According to the World Health Organization, the specialized United Nations public health agency, 18 degrees Celsius is the safe minimum indoor temperature for most adults. Svoboda noted that while heating is unnecessary when homes stay at 20 to 21 degrees Celsius, heating should be switched on if indoor temperatures drop toward 18 degrees Celsius or become uncomfortably cold.
Radiator maintenance before the heating season
In related guidance reported by Ukrainian news agency UNIAN, experts highlighted the importance of cleaning radiators thoroughly before turning on central heating systems.
Dust and small debris frequently collect inside panel radiators, accumulating between internal metal fins, under top grilles, and behind the wall mounts. This buildup acts as an insulating barrier, reducing heat transfer into the room and forcing heating systems to work harder.
Cleaning radiators internally and externally before the start of the season ensures maximum thermal efficiency when heating is finally activated.
