When Dr Wolfgang Feist realised that domestic heating used the largest single share of modern energy consumption, he set out to find a solution. Working with concepts developed in Sweden and North America, he refined home heat exchange and insulation systems to the point of maximum efficiency. The result was the first Passivhaus (passive house) properties, built in Darmstadt in 1990. Today, his principles are among the most recognised in sustainable construction.
For a property to be certified as a passive house, the International Passive House Association says it must have:
heating demands of less than 15kWh per year, or 10W per square metre of living space,
cooling demands equal or similar to those for heating,
total energy consumption of less than 120kWh per year,
a maximum of 0.6 air changes per hour at 50 Pascals pressure, in order to prevent draughts and heat loss, and
living areas that maintain consistent temperatures of 20–25°C for 90% of the year.
These requirements are met by building designs that maintain a constant atmosphere, rather than heating, cooling and exchanging air ‘on demand’. Key to achieving this is the idea of continuous insulation.
This construction method is all about avoiding thermal bridges – areas that facilitate the exchange of hot and cold air, which causes heat loss in winter and overheating in summer. Continuous insulation also helps prevent condensation, a leading cause of damp problems. As well as efficient insulation, passive houses must have extremely efficient windows to prevent undesirable air, moisture and heat exchange.
With the atmosphere tightly controlled, it’s then regulated by air and/or ground source heat exchange pumps. These use plumbing systems to transfer heat and fresh air in and out of the house, maintaining a constant temperature with minimum energy use.
The maintenance of a controlled atmosphere not only saves money, but also reduces energy consumption significantly compared to standard homes, making passive houses incredibly eco-friendly. Data sourced from passive house developments also suggest that they make incredibly comfortable homes. The near-constant temperatures and mechanical ventilation can help improve air quality, without the inconsistency and sudden shifts experienced with window ventilation.
The main downside is that they can’t easily adapt to big changes. If you’re redecorating, for example, opening all of the windows and doors to ventilate will unbalance the system and it will take time to recover. Similarly, if you (or your guests) like an extremely warm or cold environment, you can’t simply turn the heating up or open all the windows to accommodate this.
While the concept is often sold as an affordable energy saving idea, lots of modernist architects have built luxury homes to Passive House standards. So you can find modern, minimalist passive house mansions that are sustainable, yet contain every luxury you’d expect from premium developments. And because they’re just as valuable in cold and warm climates, you’ll find them in regions as diverse as the coast of Portugal and British Columbia.
However, if you're not ready to buy a passive house property just yet, there are still lots of sustainable architectural trends to explore, from the renaissance of wooden buildings to vertical living. And with a better overview, you’ll be fully equipped to decide on the right construction approach for your new home.