An unknown type of building in our country is gaining more weight, as only 66% of people have heard of it: passive buildings or those that comply with the Passivhaus standard. Simplifying the concept, we could say that it is a building capable of maintaining the thermo-hygrometric conditions (environmental temperature, humidity and ventilation) in the interior, without almost needing energy input.
Obviously, to achieve such an ambitious goal, very careful planning is required, with a well-studied design and, of course, a highly qualified execution. And it is that among the factors that contribute to having a passive building are from the orientation of the holes, to the thermal insulation used, the thermal bridges and a meticulous control of the filtrations.
If this is achieved, it is possible to reduce the heating and cooling needs by more than 75%, provided that certain requirements are met:
- Limit the building’s energy demand to 15 kWh / m2 / year for both heating and cooling.
- Limit the total primary energy demanded to 120 kWh / m2 / year (including air conditioning, lighting, appliances, equipment, etc.)
- Guarantee an air tightness not exceeding 0.6 renovations / hour at 50 Pa of depression compared to the exterior.
Without human intervention
One of the main novelties brought by passive buildings is that, despite what their name suggests, they are much more active than traditional buildings. If until now we are used to being an active part of the house, ventilating it, providing it with heating and cooling, etc., the idea underlying the passive buildings is that they are the ones who work for us without having to intervene.
A good example that illustrates this approach is the temperature-ventilation relationship. We are accustomed to look for a better quality of the air by ventilating when opening the windows and, on the contrary, to pursue the thermal comfort by means of air conditioning units. In a passive building, on the other hand, air quality is achieved by relying on ventilation systems that recover heat, while the comfort temperature is achieved thanks to the use of passive insulation-enclosures.
The basic principles
- Super isolation. The recommended thermal envelope doubles or even triples the one that is usually used in Spain. This also happens with high-performance windows and doors.
- Elimination of thermal bridges. These are the points at which, due to a change of material in the structure, the thermal envelope weakens.
- Infiltration control. If we manage to eliminate unwanted air infiltrations, we can achieve thermal comfort only with heat recovery, without using another system.
- Mechanical ventilation with heat recovery. A recuperator is able to touch the heat of the interior air and change it for the fresh outside, previously filtered and tempered.
- Optimization of solar gains. In line with the previous one, all the heat that we generate inside (people, lighting, appliances …) is very profitable.
The importance of climate
When assessing some of these factors, the climate happens to be in the top positions, greatly conditioning the relationship between people and the spaces they inhabit and, therefore, determining when it comes to achieving comfort. Faced with this situation, passive buildings must be able to find a balance between the demand of the inhabitants and what housing can really bring.
For this it is imperative that since the building only appeared in planes, these conditions have been taken into account, so that in the coldest regions prime design in solar gain and internal heat conservation, while in the most hot will seek more sun protection and passive cooling.
The conclusions of a study, promoted by companies in the sector, that analyze the energy habits of people, have just been made public. The objective is to mark the way towards the construction of these almost null-passive consumer buildings.
Despite the fact that for 60% of the respondents, comfort is vital for their healthy life, one of the first conclusions that are drawn is the widespread lack of knowledge on the part of people of the factors responsible for the home-comfort relationship. Health. It follows that when addressing a new work or a rehabilitation, although they verify the impact, they do not know how to reduce it or even eliminate it, because they do not know the real causes. Hence the importance of always having qualified professionals with experience behind them.