Passivhaus: the miracle of passive houses.

Passivhaus or passive houses are homes that are characterized by their high energy efficiency and low consumption of resources. These homes are designed and built following the principles of the Passivhaus standard, which is an international certification that guarantees compliance with quality and sustainability requirements. In this post, we are going to explain what passivhaus or passive houses are, what the Passivhaus principles are and what benefits they have for their inhabitants and the environment.

What is the Passivhaus standard?

The Passivhaus standard was created in 1988 by the German physicist Wolfgang Feist and the Swedish Bo Adamson, a professor at Lund University. The objective of this standard is to reduce as much as possible the energy demand of buildings, both new construction and rehabilitation, through the use of passive design and construction strategies. These strategies are based on making the most of available natural resources, such as sunlight, climate or natural ventilation, and minimizing heat or cold losses through optimal thermal insulation, adequate air tightness and a ventilation system. mechanical with heat recovery.

The Passivhaus standard establishes quantitative criteria that buildings must meet to obtain certification. These criteria are the following:

• The heating and cooling demand must be less than or equal to 15 kWh/m² per year.
• Primary energy demand (including heating, cooling, domestic hot water, lighting and appliances) must be less than or equal to 120 kWh/m² per year.
• The air tightness must be less than or equal to 0.6 renewals per hour at a pressure of 50 Pa.
• Thermal comfort must be guaranteed for at least 90% of the year, with an interior temperature between 20°C and 25°C.

The Passivhaus standard can be applied to any type of building, whether residential or non-residential, and has three levels of certification: Passivhaus Classic, Passivhaus Plus and Passivhaus Premium. The highest level is Passivhaus Premium, which implies a higher degree of energy efficiency and greater use of renewable energy.

What are the Passivhaus principles?

To meet the criteria of the Passivhaus standard, buildings must follow five basic principles of design and construction. These principles are the following:

• Optimal orientation: it is about orienting the building in such a way that maximum use is made of solar radiation in winter and overheating is avoided in summer. To do this, large windows are usually placed on the south and east facades, and they are protected with elements such as overhangs, blinds or vegetation. The shape and volume of the building is also taken into account to reduce the surface area exposed to the outside and improve compactness.
• Thermal isolation: It involves wrapping the building with a continuous layer of insulating material that prevents heat loss or gain through the walls, ceiling or floor. The thickness and type of insulating material depend on the climate and the characteristics of the building, but they are usually higher than those usual in conventional construction. In addition, thermal bridges are avoided, which are areas where the insulation is interrupted or reduced, such as the encounters between structural elements or blind boxes.
• Air tightness: it involves sealing all possible air leaks between the interior and exterior of the building using gaskets, tapes or putties. In this way, hot air is prevented from escaping in winter or cold air from entering in summer, which means energy savings and improved comfort. Air tightness is measured through a test called blower door test, which consists of subjecting the building to a certain pressure and measuring the flow of air that enters or leaves through the leaks.
• Mechanical ventilation with heat recovery: It involves installing a ventilation system that renews indoor air in a controlled and efficient way. This system consists of two networks of ducts: one that extracts stale air from the interior (from the bathrooms, kitchen or bedrooms) and another that introduces clean air from the outside (in the living room, dining room or bedrooms). Both networks pass through a heat exchanger that recovers part of the heat from the extracted air and transfers it to the incoming air. In this way, good indoor air quality is achieved without losing energy or comfort.
• Use of renewable energies: it is about incorporating systems that take advantage of the renewable energy sources available in the environment, such as the sun, wind or biomass. These systems can be thermal solar panels to produce domestic hot water, photovoltaic solar panels to generate electricity, wind turbines to harness wind energy or biomass boilers or stoves to generate heat. These systems make it possible to further reduce conventional energy demand and increase the autonomy and sustainability of the building.

What benefits do passivhaus or passive houses have?

Passivhaus or passive houses have multiple benefits for both their inhabitants and the environment. Some of these benefits are the following:

• Economic savings: By having a very low energy demand, passivhaus or passive houses represent great savings on heating, cooling and electricity bills. According to some studies, this savings can reach up to 90% compared to a conventional home. Furthermore, having greater durability and construction quality, passivhaus or passive houses require less maintenance and repairs.
• Thermal comfort: By having a stable interior temperature throughout the year, between 20°C and 25°C, passivhaus or passive houses offer a high level of thermal comfort to their occupants. Furthermore, by avoiding cold or hot air currents and sudden changes in temperature between rooms, the thermal sensation is improved and problems such as colds or allergies are avoided.
• Indoor air quality: By having a controlled mechanical ventilation system with heat recovery that filters outside air, contaminants, allergens and bad odors are eliminated, which promotes respiratory well-being and prevents diseases.
• Sustainability: By reducing environmental impact, you contribute to the mitigation of climate change and preserve natural resources for future generations.