Can your home be as sustainable as you are? Passive architecture is about more than saving money

Staying warm and cozy in the cold months, comfortably cool in the summer and saving energy: these are, broadly speaking, the defining characteristics of passive houses, a concept which first emerged in the 1980s and meets the challenges of environmental efficiency today.

Text by José Miguel Pascual Labrador. Photography by David Fernández.

Throughout history, many cultures have built sustainable and passive houses, perhaps without even being aware of it, from mud houses in Africa to tents in the desert or Arctic igloos. But the invention of air conditioning and heating systems in the 20th century started a trend that somewhat disassociated construction from the purpose of sustainability, 

Recently, however, amid the growing awareness of the climate emergency, saving energy is starting to be perceived as more than just a financial matter, and as a problem that can be solved by architecture itself. Of all the associated movements, the most outstanding is the model designed by the German Wolfgang Feist—also founder of the Passivhaus Institut (PHI)—and the Swede Bo Adamson, who developed the passivhaus concept and whose first real work was built in 1990, to the north of the city of Darmstadt (Germany). A four-dwelling building, it was created under a series of premises to achieve average consumption of less than 15 kWh and 90% savings on heating.

Certification criteria

Passivhaus certification is based on a series of criteria, which, while not set in stone, do establish some essential features. According to the Passivhaus Building Platform (PEP), a non-profit association for technicians and professionals in the construction sector, the main characteristics of this concept are as follows: 

1. Thermal insulation. The house is surrounded by a protective layer that prevents the entry of cold or warm air. In cold environments, this layer can be up to 20 or 30 centimeters thick. 
2. Airtightness. After thermal insulation, it is necessary to ensure a good seal to prevent heat from escaping through cracks and/or the creation of drafts, which reduce energy efficiency. 
3. High-quality windows and doors. These are also considered a part of the insulation and airtightness of efficient dwellings. It’s important to not only choose the best orientation to maximize solar gains, but also to use windows and doors that avoid energy losses as much as possible.
4. Reduction of thermal bridges. This refers to points where the insulating surface is broken, creating an interior temperature difference, such as a door frame or in areas with nails or other anchoring systems.
5. Ventilation system with heat recovery. Passive architecture recommends installing a mechanical ventilation system that filters the air and recovers the home's own heat to warm the incoming air. 
6. Bioclimatic design. Last but not least, it all starts with a good initial design if we are talking about a new construction, or a meticulous study of the available options for a building renovation. This will consider factors such as orientation, structural compactness, solar protection, and in general, the relationship between the energy required in each space and how it is to be used.

Energy benefits of passive architecture

According to the Institute for Energy Diversification and Savings (IDAE), the correct use and maintenance of heating, hot water, household appliances, lighting and air conditioning are essential to energy savings, and buildings account for 30% of total energy consumption in Spain. In addition, its records show that 50% of a home's energy consumption (which stands at 15,514.42 kWh in a single-family home and 7,547.87 kWh in an apartment or flat) is due to the use of air conditioning and heating appliances. 

This echoes the energy focus of passive houses, which, in the case of Passivhaus Institut’s projects, can reduce energy consumption by 75% to 90%. In its opinion, it is necessary to go beyond containment measures, such as lowering the thermostat or limiting the use of air conditioning, and architecture “can and should help" to minimize consumption.

However, many consumers may wonder about the cost of building a self-sufficient home. While the initial cost is indeed higher compared to traditional types of construction, sector professionals cite the subsequent savings and easier maintenance as compelling reasons to consider the investment.

“High-quality" materials can add 5% or 10% to the price of a home or building, which together with other elements, such as windows or doors, could mean an extra 100 euros per square meter. Thus, the typical cost of an efficient home, depending on the company, may range from 1,000 euros/m2 to 1,300 euros/m2. According to Francisco Sánchez, representative of the PEP in Madrid, despite what one might think about the designation of high-quality, "it has nothing to do with luxury." It’s simply a matter of using efficient and innovative elements. 

Meanwhile, the CEO of PAEE Construcción Passivhaus-ECCN, Guillermo Hornero, told Planet Energy that the latest update of the Technical Building Code has reduced the “gap,” bringing housing closer to high-energy performance.  Therefore, the higher initial investment, optimizing the project, means a significant improvement in comfort, efficiency and health. If all the necessary criteria are met, and depending on your geographical area, after a few years you can save up to 2,500 euros per year, meaning about 70% lower consumption than a traditional home. 

Renewal of Spain’s building stock

According to Roberto Alonso, Passivhaus Studies Technician, and Álvaro Pardo, PAEE's Innovation and Sustainability Architect, in recent years there has been an increase in the demand for Passivhaus certificates. In their case, these have ranged from single-family homes built with different construction systems to an EnerPHit renovation (the Passivhaus certificate applied to renovation) of 21 homes in the center of Madrid.

As part of the National Integrated Energy and Climate Plan, the public administration is seeking to boost the energy efficiency of more than 1 million homes in Spain from 2020–2030, since the Spanish building stock has an average age of around 50 years old. To promote energy-efficient homes, the Ministry of Transport, Mobility and Urban Agenda aims to improve the energy efficiency (thermal envelope) of 1,200,000 homes over the course of the decade and to renew the thermal heating and hot water facilities of an average of 300,000 homes per year. With this aid, the concept of passive architecture as a tool in the energy transition appears to have been consolidated.