When dealing with the issue of thermal insulation of a building, we usually think of insulation for the winter season. Therefore, reduce heat loss to reduce heating costs. Obviously, winter insulation is very important but if we only keep this aspect in mind, we forget to consider the energy costs due to summer cooling which in certain situations can be even higher than the costs for winter heating.
If you want to evaluate a thermal insulation intervention, it is, therefore, advisable to consider what are the choices to make to obtain optimal results in both situations: the winter and the summer. A correct summer thermal insulation allows to reduce by about 50% the energy costs deriving from the use of air conditioners for cooling.
Thermal insulation for at least 25% of the total dispersing surface allows access to the 110% super bonus.
If you are in Turin and its province, I recommend that you contact a specialized company such as EcoStili.
Table of contents
- Elements to consider in the case of summer thermal insulation
- Other elements to consider
- Thermal insulation of the attic
- Materials to consider for summer insulation
- The ventilated facade
- So what needs to be done to achieve good summer thermal insulation?
Elements to consider in the case of summer thermal insulation
The elements to consider for optimal summer thermal insulation are:
1. Periodic thermal transmittance (U)
The thermal transmittance periodically measures the amount of heat exchanged by a material or a body per unit area and unit of temperature and defines the insulating capacity of an element. It is measured in [W / m2K]. It may seem like a complicated step but the important thing to keep in mind is that the lower the transmittance value, the greater the insulating power of the material.
2. Thermal inertia
Thermal inertia is the ability of a material to vary its temperature more or less slowly in reaction to changes in external temperature or to a source of heat or internal cooling. In practice, thermal inertia is the ability of a material to heat up (or cool down) more slowly than another.
To simplify, we can say that thermal inertia allows to:
- Reduce the heat spike that can be created inside the house
- Create a phase shift, that is to say the ability to make the effects of heat coming from the outside feel with a delay (of a few hours). This means that the insulating material absorbs a large part of the heat that reaches the building during the day (retaining it and without letting it enter the house) and releases it with a lower intensity after several hours (for example during the night hours when the external heat is attenuated.
It is evident that if the phase shift is only a few hours, the environment becomes very hot even during the evening and night, because the internal walls release the heat accumulated during the hot hours too quickly. A phase shift greater than 12 hours, on the other hand, allows the heat accumulated during the evening and night hours to be disposed of.
Other elements to consider
In addition to periodic thermal transmittance and thermal inertia, ventilation and shading should also be considered for an optimal evaluation of a summer insulation intervention.
Shading can be obtained through systems:
- filtering (such as curtains)
- shielding (such as louvre systems)
- blinds (e.g. roller shutters)
- trees with deciduous leaves
By ventilation we mean the natural one, which should facilitate the dispersion of heat, especially at night. But due to the “heat island” effect that occurs in the largest cities, it is also good to be able to ventilate through a controlled mechanical ventilation (VMC) system.
Thermal insulation of the attic
The roof is the part of the building that generally presents the greatest problems of heat dispersion in winter and heat accumulation in summer.
The owners of independent houses or apartments on the top floor of a condominium know very well that the attic rooms are the most critical in the whole house, where, especially in summer, the rooms immediately placed under the roof reach very high day and night temperatures.
As for vertical walls, even in the case of attic insulation, the insulating material used must have a low thermal conductivity (it must be a good insulator) but at the same time a high material density, i.e. a mass expressed in Kg / m3, high (see table in the next paragraph).
Materials to consider for summer insulation
Specifying that each intervention must be evaluated and designed as a case in itself and that therefore also the materials are to be chosen according to the specific case, on the basis of what is indicated above, in the case of summer thermal insulation there are materials more suitable than others.
From the table it can be seen that, in principle, the most suitable materials for summer insulation are wood wool, wood fiber, expanded cork, rock wool.
Materials such as EPS, XPS or polyurethane do not have a sufficient density (kg / m3) to obtain optimal summer insulation.
Natural materials such as wood fiber, cork or hemp are also highly permeable to vapor allowing the house to “breathe”.
We could argue that these materials (wood wool, cork) are less effective from the point of view of winter insulation than materials such as EPS or polyurethane. This is true even if there are minor differences. The same results can also be achieved for the winter phase by providing a few more cm of insulation but using Eco-sustainable materials.
The ventilated facade
External wall (red in the image). Insulation material for winter insulation (in yellow). An empty space is left between the insulating material and the ceramic panel (in orange) for the air to circulate.
(From Wikipedia): “The ventilated facade (or ventilated wall) is a particular type of perimeter cladding of the walls which involves the dry application, on the external surface of the building, of panels of appropriate thickness, not strictly adhering to the structure. The ventilated facade is essentially characterized by the position of the external cladding layer, which does not adhere to the infill wall but is spaced apart to form a cavity. In this way, the natural circulation of the air in the space of the cavity is obtained, due to the convective motion produced by the presence of openings arranged at the base and at the top of the facade “.
It should be noted that this intervention must be considered in the case of walls of a certain size to exploit the so-called ” chimney effect ” and is therefore an intervention to be evaluated mainly in condominiums of a certain height. The project must be done very carefully because the chimney effect could, in exceptional cases, favor the development of flames that can be generated in some external areas of the building.
To learn more about the chimney effect, read the natural cooling techniques.
So what needs to be done to achieve good summer thermal insulation?
If you are interested in understanding how you can reduce your energy consumption and thus save on winter heating and summer cooling costs, the first thing to do is to ask for a professional’s advice who can evaluate the most suitable interventions for your home.
An analysis of the context in which the interventions (for example of thermal insulation) will be carried out will allow you to obtain the maximum result in terms of cost reduction and increased comfort and will avoid having problems due to an intervention carried out in a hasty manner ” so much to isolate the cold wall facing north “.