Living with less energy thanks to philosophy ‘passive house’. Since 2018, the member states of the European Union (EU) are obliged that public real estate be ‘Nearly Zero Energy Consumption Buildings (EECN)‘. As of 2020, this obligation was extended to all newly built buildings. Hence, efficient construction is becoming increasingly important. ‘Passivhaus’ is a construction standard for high energy efficiency, the most demanding worldwide. In Spain there are already 169 homes with the Passivhaus seal. And the demand is increasing.
The main objective of this standard is achieve the lowest possible energy demand while ensuring a high quality indoor environment. The ‘passivhaus’ or passive houses, thanks to global design strategies, They manage to reduce energy consumption by up to 90% compared to a normal house.
The ‘passivhaus’ standard, created in 1988 by the German Wolfgang Feist and the Swedish Bo Adamson, is perfectly aligned in the fight against climate change due to the drastic reduction in energy consumption in the use phase of the housing stock, both in new construction and rehabilitation.
That a house is a ‘passivhaus’ dwelling means that it is Respectful with the environment and that standards, methods and use of suitable materials have been followed during its planning, design and construction based on principles of energy efficiency and sustainability.
The pandemic has caused interest in passive houses to skyrocket. Mobility restrictions and the generalization of teleworking have highlighted the Serious deficiencies in the Spanish housing stock, especially with regard to aspects such as energy demand, poor indoor air quality or thermal insulation.
Significant energy savings
Spain has legislation that addresses the construction of EECN. And although this regulation is more lax than the requirements demanded by the Passivhaus certificate, connoisseurs of the housing sector predict that passive houses will gain more and more prominence due to their advantages, among which are clean interior spaces, without contaminants, with a constant temperature all year round and, above all, the significant energy savings.
How do you get the Passivhaus certificate? It is not an easy task. It must be granted by the Passivhaus Institut or by an entity authorized by it. There are four mandatory requirements related to energy demand, airtightness and what experts call the envelope’s thermal transmittance (measure of the heat that flows per unit of time and surface). The house must meet seven basic principles:
1. Bioclimatic design. It requires a good initial design (in new construction) or a detailed study of the available options (in rehabilitation), taking into account factors such as the orientation of the property, compactness of the building, solar protection, etc.
2. Thermal insulation. So that a home does not lose heat in winter and offers a cool environment in summer, the house envelope must incorporate large thicknesses of thermal insulation, greater than those indicated by the regulations. This envelope is a barrier that insulates from cold and heat. They are integrated into the walls, floors and ceilings that lead to the outside, to other neighboring houses and to the common areas.
3. Eliminate thermal bridges. It is the lung of passive buildings. All the points of the building envelope where there is usually no insulation in traditional homes, such as the facade pillars, are treated and calculated to avoid weak points where energy can be lost.
4. Hermeticism. Any space in holes or cracks must be sealed to prevent unwanted air infiltrations as much as possible and preserve the comfort of the home. It also eliminates internal air currents.
5. High performance carpentry. Doors and windows must have very low thermal transmittance. PVC is usually used with multilayer glass (generally triple), gas-filled chambers so that they transmit less temperature, and insulating frames and profiles. The crystals keep the heat in winter and reflect the sun in summer.
6. Mechanical ventilation with heat recovery. A mechanical ventilation system is installed that enables a constant renewal of the interior environment of the house throughout the day and that avoids high concentrations of CO2, odours, mites, viruses and other impurities. Ventilation equipment is also installed to guarantee maximum energy efficiency and a low noise level.
7. Sun protection. It is especially relevant in passive buildings, because it is vital to prevent overheating from occurring. For this, it is necessary to thoroughly study the appropriate design and the necessary strategies for sun protection.
Certificate for rehabilitated buildings
The Passivhaus certificate is obtained at the end of the work, after an approved Passivhaus technician has verified that all the requirements are met, but it must also be verified during the project and construction phase.
How much does a ‘passivhaus’ house cost? According to some studies, a passive house usually costs 5% more than a normal one, although the difference can reach 15% in the prime (luxury) real estate sector and depending on the chosen finishes.
But, according to experts, these extra costs are quickly recovered because a building certified with the Passivhaus standard has an estimated revaluation of 20%. In addition, energy savings are enormous, up to 90%. Finally, the operating costs are significantly lower.
Rehabilitated buildings can also obtain a certificate equivalent to Passivhaus, called EnerPHit and also issued by the Passivhaus Institut. Although EnerPHit is more lax than Passivhaus, it maintains most of its principles.
In Spain, the sector of the prefabricated houses with the Passivhaus seal, living a real ‘boom’ in the United States. They are airtight buildings, with a dedicated fresh air system, an energy or heat recovery ventilation system, high performance water heaters, high insulation, and high performance windows and doors.
Website of the Passivhaus Platform: https://www.plataforma-pep.org/