Guide to the relationship between windows and energy saving: let's clarify concepts such as heating, dispersion, performance and environmental impact.
Correct space heating for economic savings and environmental protection
Energy saving plays an increasingly important role in the purchase of any type of product, even more so in the choice of doors and windows. The window market offers a wide range of models which over time have reached a high degree of completeness and reliability from an energy saving point of view. The savings that can be obtained by properly ventilating a home are both economic and environmental.
Excessive heating is synonymous with unhealthy environments, it is uneconomic and ecologically unsustainable. The conditions of well-being occur at a temperature of 20 ° C while the rooms little used by people can be kept at a temperature of about 12 ° C.
What is the correct method for ventilating rooms? Windows wide open or windows ajar?
It is good practice to ventilate a room when there has been a prolonged presence of people. From an energy saving point of view, is it better to open the windows for a short time or keep them ajar for a long time?
The most efficient way to ventilate is to
open the windows for about five consecutive minutes (in proportion to the size of the space), and then close them again. In fact, if we decide to half-close the windows for longer times this would lead to an excessive heat dispersion towards the outside and to the cooling of the perimeter walls (for which a new use of energy is required).
How to eliminate thermal bridges and calculate dispersions?
The installation of properly insulated windows, i.e. with good gaskets, seals and double glazing, prevents the cooling of the air-conditioned internal temperature. Unfortunately, the cold outside temperature tends to sneak through cracks, crevices or poorly insulated materials. If you have a window that is not perfectly insulated, you can still try to limit heat loss by keeping the shutters, roller shutters or shutters closed during the night, inserting
draft excluders under the entrance door, replacing the old
worn gaskets or redoing the seals.
The UNI 10349 standard indicates the
formula for calculating heat losses :
QT = 86.400 x N x HT x Δ Ø
where is it:
QT = total heat loss;
86,400 = seconds in a day;
N = number of heating days;
HT = area of the window multiplied by its coefficient of transmittance;
Δ Ø = temperature difference between inside and outside.
If we are based on average estimates, a saving of about 25% in terms of energy consumption (a quarter of annual heating costs) is achieved between new and old windows. If we then go to insert low-emission glass instead of standard double-glazing, a saving of up to 35% is obtained. This would allow the recovery of the investment for the replacement of the windows in about 5 years.
Construction is a field in which it is still largely possible to make innovations with the aim of containing the high heat losses currently present. In fact
, 40% of the energy we invest every day to air-condition the rooms is dispersed in the atmosphere through the building envelope. Of this 40%,
almost 10% is lost due to window surfaces!
The certificate of energy performance of buildings
The frame plays a fundamental role in economic, environmental and aesthetic terms within the building envelope. From the legislative decree 192 of 2005 the notion of "
energy class " for buildings was introduced. Thanks to this concept, when we intend to buy a new house that has just been built, we can immediately know what the operating cost is to maintain the temperature we want inside this structure. The
energy performance certificate (APE) certifies the energy performance of buildings. The certification follows three parameters: thermal transmittance, air permeability and light transmittance.
The window is made up of several parts that can be improved to increase their energy performance:
- the type of frame and profile;
- the frame and the gasket systems;
- hardware and hinges;
- the material it is made of.
The link between windows and environmental impact
The concept of environmental impact involves window and door manufacturers, customers and the environment itself. The manufacturing company can reduce the environmental impact in various ways by making different types of investments (for example the reduction of the material used in the production process, the type of disposal envisaged, the packaging used, etc.). Companies that engage in this direction are recognized by ISO 14001 certification. Together with ISO 9001 on quality, they are a guarantee of product quality and consumer protection. The consumer, on his own side, as the end user of the product should reward the product that offers the greatest guarantees of quality.
How to choose the most suitable window according to the environment?
Before ordering a new window, it is necessary to understand
what type of building intervention we are about to start. If it is a
new building the constraints in the choice of the window frame are practically null. The same in the case of a
renovation with complete replacement of the old fixtures (including frame and
subframe ). In this case the designer will be able to examine all the solutions.
If, on the other hand, it is restructured by replacing the old windows but
without removing the fixed frame, it will not be necessary to carry out masonry works but there will be limits in the choice of the type of window and related accessories (such as mosquito nets), not to mention the aesthetic result which obviously it will be compromised. The advantage of this last type of intervention will be the speed and the lower cost. Even if a simple replacement of the fixtures is carried out, the energy performance will not be compromised but the light of the new window will be reduced. This is because in this last case no masonry works were done to remove the old frames and false.
We hope we have allowed you to deepen some of the concepts that are often poorly explained in the world of fixtures, although extremely important. If you have any doubts, you can comment on the article publicly or contact us.
