Question: What criteria do passive homes meet to achieve almost zero energy consumption?
- They must meet certain requirements in terms of actual heating demand (less than 15 kWh/m2 ), cooling demand (also less than 15 kWh/m2), and primary energy demand (hot water and electricity).
In addition, the airtightness of the building must be ensured, not exceeding 0.6 air changes per hour. Compliance with these parameters must be formalised through a physical test and audit.
Question: What concrete solutions does it provides?
- The solutions are focused on two main aspects. On the one hand, the relationship of the house with its environment and its establishment on the plot. The micro-climate of each area must be kept in mind when carrying out the project.
On the other hand, the constructive solution of the home and the materials used are also crucial: superinsulation, high-performance carpentry, eliminating thermal bridges, mechanical heat recovery ventilation systems, etc.
Question: How is it different from conventional housing?
- The main difference is energy efficiency. A passive house consumes less energy than a conventional home does to guarantee thermal comfort inside, which helps, on the one hand, save on the consumption of energy sources and, on the other hand, reduce CO2 emissions. This can combat pollution and climate change.
Another important difference is the reduction of maintenance work, since in passive housing, the fluctuation of temperature and humidity changes inside the house is minor. Materials and equipment suffer less and last longer, preventing construction pathologies related to these changes from emerging.
Question: Is the construction a major investment?
- The cost of carrying out this type of construction is higher than that of "conventional" housing, but taking into account the useful life of a home, the return on the extra investment occurs quickly, between 5 and 10 years.
Question: When you are tasked with a passive housing project, is the first thing you do a study of the climatic conditions of the plot? What other preliminary analyses are performed?
- It is essential to be aware of the micro-climate of the plot and to adapt our solutions to it. But it is equally important to analyse and find the balance between the orientation of the house with respect to the sunlight and the views the plot offers, to assess presence of water on the plot, as well as wooded areas or other obstacles that cast shadows, etc.
Question: With regard to traditional houses, how much energy is saved in these homes? Can you reach 100%? Or in other words, is it possible for energy consumption to be zero?
- The savings are remarkable, reaching even 90% on heating and cooling demand. In real cases, zero consumption is very difficult to achieve.
Question: How do they save energy?
- Basically taking advantage of clean energy (solar, geothermal) to provide heat, and keeping this heat inside the house through its construction system with high thermal mass.
In the case of warm climates, where the cooling system takes precedence, we must adapt the home's construction by using heat sink materials such as water and installing a smart heating/cooling system. Heat recovery systems with a bypass option are also used, minimising loss due to air change.
Question: Is it possible to change the energy rating of a house built a few years ago in such a way that it is adapted to the zero consumption requirements?
- It depends on each particular case and how the building was built at the time. But the cost of the work that needs to be performed in order to adapt the existing home to the zero consumption requirements would be entirely disproportionate to the value of the house.
Remodelling work that has been performed lately does significantly improve the energy efficiency of the home, although zero consumption cannot be achieved.
Question: Who requests this type of home be built? Individuals, construction companies, public administrations…?
- Many sectors of the population are currently requesting it; individuals in particular are increasingly concerned about the matter, especially in new constructions.
The incentive of public administrations through subsidies is providing a powerful boost to this type of activity, especially in cases of refurbishing and remodelling the housing stock.