THERMAL INSULATION

The choice of windows in a thermal insulation project

In a house, about 25-30% of the energy can be lost through the windows, hence the importance of their thermal insulation which depends on the material of the frame, the glass, and the seal of the window. The greatest attention must be paid to the glass, which is the most exposed surface and therefore significantly affects thermal and acoustic comfort. The most common solution is double glazing, a prefabricated material consisting of two glass sheets joined along the perimeter with a plastic sealant but spaced at least 4 mm apart, in order to form an air space to be filled with a gas (argon or krypton) with high insulating power, both thermal and acoustic. What makes the difference is the composition of the inner sheet, tempered or laminated. The latter is generally subject to a low emissive treatment, consisting of the application of a microscopic and invisible deposit of silver that reflects the internal heat emission of the house, it can also reach 90%. There is then the possibility of making the window even more efficient in the summer period with the selective treatment that is done on the outer sheet, consisting of a microscopic film of metallic oxides that reflect solar radiation preventing excessive heating of the interior. The materials commonly used to make the frame are: aluminum, wood, and PVC, each of which has different characteristics in technical, aesthetic, and economic terms. Wood and PVC are very thermally insulating materials, PVC and aluminum are recyclable. Often the materials are combined to take advantage of their respective advantages. Even the European standard of the window product (EN 14351-1) does not consider the different materials for frames but only the performance of their assembly. A final consideration concerns acoustic comfort, that is, the reduction of external noise. The greatest soundproofing power is obtained by increasing the thickness of the glass sheets and using asymmetrical double glazing, that is, made with two sheets of different thicknesses.

Thermal insulation coating: constant temperature in winter and summer

The coat insulation system is used as an exterior cladding for new or renovated facades to optimize the thermal performance of the building. Providing a thermal insulation system for the facade means:

• Eliminate thermal bridges
• Exploit the thermal inertia of the walls
• Protect the facade
• Improve indoor comfort in summer and winter
• Have a healthy environment, free of condensation and mold
• Reduce the energy needs of the building
• Re-evaluate the value of the property
• Reduce the levels of CO2 released into the environment.
   

Thermal insulation coat systems allow for optimal energy performance in: low-consumption buildings (heating consumption less than 50 kWh/m² per year), passive houses (heating consumption less than 15 kWh/m² per year), and buildings that produce more energy than they consume. To ensure living comfort in every type of building, it is essential to start from a correct thermal insulation project, defining the requirements to be imposed on the envelope and choosing the design parameters that add value to living. Once these requirements are defined, we proceed to identify the most suitable technological solutions to guarantee them and make them compatible with existing architectural and economic constraints. Technological solutions can be grouped into two categories:

1. Passive, i.e., constituted by the building itself, its shape, orientation, exposure, construction system, and thermal insulation

2. Active, constituted by equipment, controls, and adjustments installed to graduate energy consumption and the use of renewable energy sources.

Living comfort is achieved with adequate thermal insulation of structures so that the temperature of the indoor air is very similar to the temperature of the internal surfaces of the house. It is indeed a scientific fact that the thermal balance of the human body is also regulated by the laws of thermodynamics. Since the temperature of the human body is constant (about 37°C), its internal energy is constant and therefore, by virtue of the first law of thermodynamics, the balance of energy exchanged with the environment must break even. Our body metabolism (i.e., the combustion of food calories) provides energy continuously. This energy must be dissipated from the body to the external environment through the mechanisms of conduction, convection, radiation, and evaporation. If the ambient temperature is lower than the body, it dissipates too much energy and tends to cool down: either we cover ourselves with more or less heavy clothes, or the metabolism must intensify and discomfort is felt. Furthermore, the comfort of the environment is also and above all determined by the characteristics of the walls of the environment in which we find ourselves, walls with which heat is exchanged by radiation. In the vicinity of an uninsulated wall, for example, in winter a sensation of cold is felt even if the air temperature is not below 20°C (comfort temperature for the human body).
 

The benefits of thermal cladding

In the cold season, thermal cladding guarantees a significant energy saving for heating, because it reduces the thermal dispersion outside the structure and definitively eliminates thermal bridges, providing a homogeneous and continuous thermal protection over the entire building. The external insulating envelope maintains a temperature higher than what would be if the insulator were placed inside, since a wall insulated from the outside stores a lot of heat when the heating system is turned on. However, the extent of energy savings and the thermal performance of the building envelope when used in warmer climates are not as widely understood concepts. In this regard, several studies have been conducted with the aim of evaluating the influence of thermal insulation on the demand for energy for heating and cooling in European locations belonging to different climatic zones. The calculations were replicated considering different levels of thermal insulation from time to time with the aim of defining how and how much a minimum level of insulation of the envelope affects the need for each climatic zone. The different thermal insulation standards can generally be traced back to four building macro-categories:

• Uninsulated building, with an envelope essentially consisting of the load-bearing or support element without any layer of insulating material
• Building with minimal insulation: the construction components are coupled with a layer of thermal insulating material of reduced thickness (4-8 cm)
• Building with a good level of insulation, with the presence of an insulating layer of 10-15 cm
• High energy performance building (15-30 cm of insulating material).

The results confirm the effectiveness of a correct thermal insulation project. In all European climatic zones, an increase in the level of insulation generates a significant decrease in the energy requirement for winter heating. This reduction ranges from 90% for buildings in Baltic climates to 80% for buildings in Mediterranean climates. Equally interesting results are obtained for summer energy and thermal performance: a higher level of thermal insulation allows to reduce by 50% the amount of cooling required in the summer period and therefore to halve the electrical consumption