Prefabrication or industrialised construction is emerging as one of the cornerstones of what is known as Construction 4.0. According to the McKinsey Global Institute, the objective of this 4th Industrial Revolution is to ditch obsolete and traditional construction methods and improve productivity by more than 50%, through- among other things- the optimization of resources based on prefabrication, zero waste and circularity.

Alongside this, we have the growing trend of passive houses, or homes certified to the Passivhaus standard, a voluntary certification seal that prioritises maximum comfort and indoor air quality for users, with almost zero energy consumption. It is characterised by close attention to detail in the design phase and rigorous on site control to guarantee a high construction quality, and is based on 8 principles:

• Bioclimatic design
• Thermal insulation
• Air tightness
• Reduction of thermal bridges
• Mechanical ventilation with heat recovery
• High performance doors and windows
• Shading devices
• Efficient mechanical & electrical systems

The increase in the number of buildings with Passivhaus certification during the last 10 years is notable, reaching more than 3,86 million square metres of certified floor area in 2024. In 2020, Spain was the country with the second most Passivhaus certified square metres in the world, led by China.

The marriage of prefabrication with the Passivhaus standard seems a logical step to improve construction quality, reduce execution times and increase productivity. Let’s have a look at some of these together.

Prefabrication: What is it and how is it applied to construction?

Prefabrication or industrialization is the mass production, off site, of the construction elements of a building, transferring work that was previously carried out on site to a workshop or factory. It generally includes structural elements and thermal insulation, assembled in a series of modules such as slabs, façade walls, partitions or roofs. These modules are transported to the building site and assembled, like pieces of a puzzle to form the building.

Industrialisation opens up interesting possibilities, such as the off site installation of windows, external shading systems and some services such as electricity, waste water, ventilation or heating and cooling equipment, among others.

Advantages and drawbacks of prefabrication in passive houses

Advantages of prefabrication for passive houses:

• Rapid onsite assembly, allowing for quick weather-proofing and protection from rain and wind. This is especially important in timber construction, a material widely used in the construction of passive houses.

• Greater precision and build quality, essential for the construction of Passivhaus buildings, above all in relation to airtightness detailing and the sealing of windows and service penetrations.

• Less waste on site and a reduced environmental impact.

• Optimization of materials, through standardised production and off site assembly, reducing material waste and costs..

Some of the drawbacks:

• Detailed design of the project has to be fully complete before manufacturing and before on-site assembly begins, and allows for fewer or no modifications once on site. It should be noted that Passivhaus projects already require detailed design to be complete before beginning construction, and allow for very little on site improvisation anyway. 

• The time saved in assembling the prefabricated structure on site, is not always reflected in the total execution time of the building. Services, fittings and interior finishes continue to slow construction down.

• The size of the prefabricated elements is limited, in width and height, by the size of the transport trucks and the free height on the roads that connect the factory with the construction site.