Design Process
The 5 basic principles for building a passive house
Addressing climate change is a matter of maintaining the level of comfort our society has achieved through clean, renewable energy sources.
To that end, there is a consensus that the solution is not to generate the same amount of energy through renewable sources—something considered unattainable with current technology—but rather to reduce consumption and focus efforts on local, self-generated energy production.
A self-sufficient home that requires little energy to operate and produces it independently appears to be the path towards a sustainable model of global development.
In this sense, passive houses are emerging as the alternative of the future. These are homes that reduce energy consumption to a minimum through exceptional insulation and, with a minimal energy demand, become self-sufficient through renewable sources.
What is a passive house?
A passive house is simply a home that works thanks to systems that do not depend on energy production. In short: INSULATION.
If we insulate a house sufficiently and cover that insulation with an airtight membrane that prevents even the slightest air leakage, we achieve a thermos-like home—that is, a home that retains indoor heat for hours.
This has two consequences:
– First, with very little energy—which can be the sun’s own heat—we achieve a comfortable indoor temperature with virtually no need for heating.
– Second, living in a thermos also has its drawbacks: there is no air exchange with the outside. What may initially seem like a disadvantage becomes an advantage, because the air exchange between indoors and outdoors is used to filter the air entering our home, free of pollutants—very useful if we live in a city—and also to recover heat from the air, further reducing energy consumption for heating.
The result of this combination is not only an eco-friendly home that requires around 10% of the heating energy of a conventional house, but also filtered indoor air and a controlled, healthy environment free of pollutants, with optimal CO2 levels.
And although this may sound exaggerated, the truth is that in most homes we live in, indoor air is polluted not only by outdoor pollution—an obvious issue in a large city—but also by insufficient ventilation, which leads to a build-up not only of CO2 but also of volatile organic compounds that are harmful to health and emitted by dust itself, paints, damp, varnishes, cleaning products, etc.
What are the characteristics of a passive house?
We always tell you that “passive house” can mean two things. The first is passive architecture, which is any element that helps improve energy efficiency and capture heat from the sun without consuming energy—for example, a simple adjustable louvred shutter that filters sunlight depending on the time of year and time of day.
The second is what is known as a Passivhaus passive house: homes certified with a German building standard seal that guarantees that your home consumes less than 15 kWh/m2/year.
To this end, the Passivhaus Institute, based in Germany with branches throughout Europe, has defined a series of minimum design criteria for a home to be considered part of the standard:
1. High levels of insulation
As we have mentioned, insulation will be a key point in reducing heat loss. We turn our home into a thermos.
2. High-quality windows
A weak point in any home is the junction between a window or door and the wall.
At this junction, heat is lost not only due to air infiltration through the seals, but also because the cold transmitted through the glass or the window frame itself causes condensation indoors, which turns into damp that is unhealthy for the indoor environment of our home.
A high-performance window whose junction with the wall is properly detailed, sealed, and insulated will ensure there is no heat loss at a point where problems are common.
3. No thermal bridges
Thermal bridges is a term used to describe an area in the construction of a home’s walls or roof through which heat escapes, generally due to a poorly resolved construction detail.
Of course, if we are saying that building a passive house requires airtight insulation, it will be essential that there is no air leakage at any point.
This is checked using a blower door test, which, after sealing the entire home, creates positive pressure through one of the doors to determine whether there are any leaks and to fix them.
4. Mechanical ventilation with heat recovery
If we are living in an airtight compartment, like a thermos, we will need a supply of fresh air.
This may initially sound strange because, when living in a passive house, it is not necessary to ever open the windows (although it is possible), as air renewal is carried out mechanically to ensure adequate quality.
Since we need to extract stale air and bring in fresh air, the indoor air is routed through a mechanism that recovers heat and transfers it to the new incoming air. In addition, this unit includes filters that ensure outstanding air quality—an excellent option if you live in an area with environmental pollution, such as a large city.
5. Airtightness
Finally, and although it has already been mentioned several times, building a passive house requires ensuring that we have achieved an airtight space to prevent heat loss.
If, in addition, we build this home with natural, environmentally friendly materials, we can ensure that we are contributing to a sustainable development model while also living in a healthy space where we will surely be happy.
At Slow Studio, we specialise in building passive houses with natural materials. Our goal is not only to create healthy, efficient spaces, but also for our clients to be happy in the homes we build.