Author: Pablo Vallejo Valle
The energy required for the construction, maintenance and daily use of buildings represents 40% of the energy consumption in the European Union. We can also affirm that a third of global equivalent CO2 emissions originate from the construction and use of buildings.
Today, with climate change and in compliance with Agenda 20/30, the latest directives on construction of buildings of the European Parliament, introduces the concept of “almost zero net energy” building. According to this directive, “the almost zero or very low amount of energy consumed should be covered, to a very large extent, by energy from renewable sources, including energy from renewable sources on-site or in the environment”
The passive architecture criteria are articulated in five basic principles: a high level of thermal insulation, the elimination of thermal bridges, the tightness of the envelope, high-performance windows and doors, mechanical ventilation with a highly efficient heat recovery system and a PHPP profit and loss energy modeling
FIGURE 1.-BASIC PRINCIPLES OF THE PASSIVHAUS STANDARD
It is as the title of this presentation says, LIVING IN A THERMO, consists of building a house that effectively retains the heat contained in the fluid, that is, it is heated by solar radiation, which is why the orientation of the themselves, cooling by natural and sustainable systems, for which heat must be dissipated, by means of air currents.
In this way, insulation becomes vitally important, it is not the more the better, but must respond to the climate where the building is located, the orientation, taking advantage of solar radiation in winter and enhancing sun protection in summer. is that the interior environment of a house is not influenced by the climatic conditions of the exterior. In the end, attempts are made to prevent the cold in winter and the heat in summer.
Avoid thermal bridges, is to avoid points in which due to a bad construction detail, there are areas through which heat escapes, leaving points in contact with the outside. It is verified with a test called blower door, in which, after closing the entire house, an overpressure is generated through one of the doors to check if there is any leak and if it does not give the test, find them and fix them.
The quality of the windows is also very important, since the exterior carpentry is a weak point of the envelope, for which the carpentry must ensure the hermeticity, for which the thermal bridge break and use triple glass with interior noble gas chambers, which improve thermal performance, limiting energy transmission.
But our passive houses, even if they work like a thermos, must guarantee the renewal of air, both natural ventilation, either through strategies such as cross ventilation, and above all with mechanical ventilation. And within this, the most efficient is mechanical ventilation with heat recovery. Taking advantage of the fact that we have to remove stale air from the interior, and introduce fresh air, what we do is introduce internal air through a mechanism that recovers the heat and transfers it to the new air that enters. In addition, these machines incorporate filters that ensure unbeatable air quality, which affects the comfort of these homes.
All this leads us to the fact that these buildings must be highly air-tight, not only from the envelope, but also from their exposure to the wind.
In homes certified with the Passivhauss seal, it is supervised that all this process, for which, very specific and measurable requirements must be met, which are the following:
The heat demand must be less than 15KWh / m2 / year.
The demand for refrigeration must also be 15KWh / m2 / year.
The demand for primary energy must be less than 120 KWh / m2 / year (including energy destined for hot water and electricity)
Ensure that the house is practically watertight, but maintaining a healthy indoor air quality, that is, ensuring 0.6 air changes per hour.
Most of our housing stock consume more than 10 times these figures.
All this makes Passivhauss certified buildings more sustainable and more comfortable. In addition, we must reflect, in these moments in which we have had to live confined in our homes, for which we and our buildings were neither prepared, and make a stop and think about our health and that of our buildings, or rather the health that can be reported by LIVING IN A THERMO.
FIGURE 2. EXAMPLE OF PASSIVHAUS HOUSING. “Importance of solar radiation protection”