The term passive house, or passivhaus, refers to a type of ecologically sound building which complies—voluntarily—with a strict set of energy-efficient and environmentally-friendly criteria. In essence, passive houses require minimal energy for heating and cooling and therefore retain a modest carbon footprint. Although primarily residential properties, passive houses can also be schools, offices or supermarkets, having grown in popularity in recent years in line with increasing environmental awareness. Originating in Germany in 1990, the passive house concept has spread widely throughout German-speaking countries and Scandinavia, with over 25,000 certified buildings in Europe alone by 2010. Notable features of these forward-thinking homes include superinsulation and passive solar building design, with a limit on the volume of air emitted from the building each year and a primary energy consumption cap of 60 kWh/m2.
In line with the rest of Northern Europe, passive house awareness and popularity has grown significantly in recent years. There are now several national bodies overseeing the construction of new homes, ensuring each complies with the strict set of standards required. In order to achieve the Passivhaus Standard in the UK, a building will require:
- Very high levels of insulation
- High performance windows with insulated frames
- Airtight building fabric
- 'Thermal bridge free' construction
- A mechanical ventilation system with highly efficient heat recovery
- Accurate design using the Passive House Planning Package (PHPP)
If you’re considering building a passive house or converting your existing property, make sure you enlist the guidance of an specialised organisation such as The Passivhaus Trust, as well as the advice of an experienced architect.
In order to meet the rigorous standards of passive house design, there are several key elements that must always be incorporated. Without these, the home cannot be certified as belonging to this category - so it’s important to get it right. The fundamental components include:
- Advanced window technology in order to allow in maximum sunlight and minimise emissions
- Passive solar design to capitalise on the sun’s energy with cleverly-placed windows and the most effective surface area for the climate
- Superinsulation to reduce heat transfer through walls
- Airtightness in order to minimise external pollution
- Passive natural ventilation where possible
- Space heating to make use of any residual energy from appliances or lighting
- Lighting from photovoltaic panels and low-energy compact fluorescent lamps
Once these elements have been incorporated into the design of the home, it will need to be independently inspected and certified before the label ‘passive house’ can be applied.
First and foremost, if you weren’t concerned about the environment and keen to make some positive lifestyle choices, you probably wouldn’t be reading this. So the number one advantage of passive houses is the relative good they do the planet, and their minimal carbon footprint. They are also inherently sustainable and built to last, so they’re a prudent investment if you have the money to play with. They’re also pleasantly in tune with the natural world, allowing a rather wholesome sense of self sufficiency. In terms of drawbacks, the most obvious is the initial cost. In order to meet the rigorous standards required to become a passive homeowner, there are many hoops to jump through in terms of materials, design and technology. There will also be some inherent limitations in terms of aesthetics and style, with function outweighing form at every turn.
If you’re seriously considering building or buying a passive house, bear in mind that you really do get what you pay for. Although new build costs tend to be 8-10% higher for this type of home in the UK, you’ll end up with a sustainable and cheap-to-run dwelling that should last a lifetime. Converting an existing property can cost around £50k, with a 3-bedroom detached passive house in the vicinity of £280k and a 4-bed coming in at £420k.