What is the optimal temperature for indoor spaces for us to feel comfortable at?

There is no universal temperature recommendation; the perception of temperature differs from person to person and is influenced by a number of factors, such as humidity and airflow. There are, however, guidelines that we can follow. The temperatures in living and working room, for example, should range from 20 to 22 °C, while a comfortable temperature range in bedrooms ranges from 16 to 18 °C. 

If I want to save energy, is it enough to lower the room temperature by just one or two degrees Celsius?

Generally speaking, each degree that we can lower room temperature by saves gas, therefore lowering energy costs. The optimal control of heating is key here. Used correctly, smart thermostats, for example, can noticeable reduce our heating costs because they allow the indoor temperature to adjust to external factors, such as the weather and time of day. Another key factor is to make sure warm air from radiators can flow freely throughout the room. This means that traditional radiators should not be covered by curtains or blocked by furniture. Regularly venting the air out of radiators is also recommended, as air in the heating system lowers its efficiency.

Heated rooms can often become stuffy — how can I improve the indoor air without losing energy?

While in the summer we recommend airing rooms out for longer periods in the morning and evening, in the winter, rooms should be aired out as briefly and as effectively as possible. If windows are left open for long periods, heated rooms lose more heat than necessary. This means that in winter it is best to adhere to an »all or nothing« principle, meaning that windows should not be left tilted and that cross ventilation is most effective.

But be aware of moisture: despite proper ventilation, moisture can remain in a room. Cold air absorbs less moisture and this increases the risk of mould. To decrease this risk, residual condensation should be wiped from tiles and windows. Moisture also enters the rooms through wet laundry, which means we should take extra care to ensure proper air circulation when drying laundry. We do not advise hanging laundry to dry in unheated rooms, as cold air does not absorb moisture very efficiently.

How do I prevent heat loss without having to renovate?

Roll shutters and thermal curtains that are closed after dark can help with insulation; by creating an additional layer of air, they reduce the heat exchange to the outdoors. The efficiency of this, however, depends greatly on the quality of the windows. Doors that separate areas with different temperatures (e.g. between the living room and hallway) should remain closed. So called »draught-stoppers« can help seal door gaps and prevent heat loss.

Owners can also improve energy efficiency: besides undertaking major renovations, such as replacing heating or windows, smaller measures, such as window maintenance, can help ensure that windows are properly sealed and extends their longevity.

Why does a tiled floor feel colder than hardwood or carpet, even when the room is a cozy 22 degrees?

Humans do not work like thermometers; in physics, temperature is an objective measurement of an object’s condition, but humans’ subjective perception of warmth varies based on the material and its heat penetration coefficient. This also includes the material’s thermal conductivity and heat storage capacity. This means that we feel the temperature of materials such as metal, natural stone or wood differently — even when they are the same temperature. The heat transfer between our skin and the surface of a material is the determining factor: Our skin receptors react to the how easily the material transfers or absorbs heat. Metal and stone are better heat conductors than wood, which means that we perceive a higher loss of heat when we are standing on a stone floor versus a wood or carpeted floor. Stone feels cold, which can be nice in the summer, but uncomfortable in the winter.

And what can we do about cold feet?

The best way to prevent your feet from getting cold is to wear thick socks or slippers. IT can also be helpful to lay carpeting in areas where feet are on the ground for long periods, such as under desks or dining tables.

Cold ground floor apartment and warm attic — myth or reality?

The ground floor in homes is usually above an unheated basement. The ceiling of basements in older buildings are typically built in the same way as the ceilings of the other floors, so this notion could be true, but it also depends on a number of other factors such as the basement temperature and ceiling insulation. The same applies in reverse for attics.