In many hotels in the South of Europe there are rooms where air conditioning cannot cope with the temperature. In many rooms, air conditioning works around the clock generating unnecessary electricity costs.
Hotel rooms – security measures are used so that the air-conditioning does not work when there are no guests in the rooms. Unfortunately, there is no switch for sunlight. The sun, through unprotected windows, heats the room by accumulating the temperature in the materials on the floors, walls and window sills. If the windows are covered from the inside with blinds or curtains – the sun’s rays get inside the room anyway and the blinds absorb (accumulate) the heat. Additionally, UV rays cause the color of furniture, curtains and floor surfaces.

When guests return to the room and the air conditioning is turned on, it has to deal with the air temperature, the temperature accumulated in the floors and walls, often working with the maximum power of the air conditioner. What if the sun was turned off? The use of sun protection films on the windows in the room without the air conditioning turned on will not allow the floors, walls or the entire room to heat up. The temperature difference between the surfaces before and after the installation of the sun protection films is 10-15 degrees Celsius in the room. From our experience on the same floor tiles outside (48C), windows with installed foil and inside the room (27 C) – temperature difference up to 21 degrees Celsius (Croatia, island of Brac – June 2020)

Do you know this feeling like in a sunny concrete parking lot or a stone street after sunset you can feel the high temperature accumulated in concrete or stone for a long time? The same is happening in your rooms. For air conditioning, it is easier to lower the temperature from 28 C to 22 C than from 38 C to 22 C (+ temperature accumulated in the materials on the floor and walls).

The simplest solution for low temperatures is to build buildings with good (thick) wall insulation and small windows. If we add a ground heat exchanger (heat exchange through a system of pipes in the ground or rock), we will obtain passive natural air conditioning. Such applications were already in the 19th century as in Blace Hermitage (Island Brac) where thick stone walls and small windows do not allow the rooms to heat up, and ventilation ducts in the rocks provide cooled air – passive air conditioning J.

Nowadays, we will not build from stone and use small windows. The trend in construction is focused on large glazing. Of course, there are ways to shade such glazing, such as hiding them in the recesses of buildings, mounting large canopies over the windows that provide shade, or protection for windows in the form of external blinds that unfortunately take away from the view. Sun protection films for windows do not have any disadvantages – they are the cheapest and the most effective form of protection against excessive solar radiation.