Passive House is pretty hot (pun intended) in the design/built environment world at the moment, but there are some aspects of the building, site and precinct that it doesn’t address.
There is no doubt Passive House is one of the important design approaches that will help transform the building stock of Australia, but it can’t fix everything.
Firstly, a quick background on Passive House. The philosophy originates in Germany, and is focused on heating and cooling a house or building in a passive manner, thereby avoiding the energy consumption associated with active heating and cooling systems.
Passive House is based on five main basic principles:
- High performance thermal insulation
- Well insulated windows with low-e coatings
- Ventilation and heat recovery, using heat recovery equipment
- Absence of thermal bridges
The Passive House may be a higher cost than traditional construction, but will also reduce the mechanical services spatial requirement, potentially increasing the building’s net lettable area. Passive House is largely used in houses and some education projects, though there are now some office and retail developments being considered in Australia.
The target is for the annual space heating and cooling demands to be less than 30 kWh/m2 of energy on average each year. Buildings meeting the strict Passive House certification criteria can be certified as Passive House buildings by any of the Passive House Institute accredited Building Certifiers operative worldwide.
But here are the aspects Passive House won’t address:
1. What about smart water systems and design?
A Passive House doesn’t consider or encourage smarter use of water in a building. Water is a significant issue in Australia, the driest inhabited continent on Earth, and there are a variety of smart solutions now being implemented to be reduce the net importing of drinking water, and exporting of stormwater, for a building. We must continually do more as urban development and population growth put more pressure on our water systems. Passive House doesn’t drive designers or architects to do more to include water smart systems and retention for landscaping and cooling.
2. What about green infrastructure?
Green infrastructure, closely linked to smarter water systems and surface water drainage, is important in building cooler, greener, healthier cities, and green infrastructure in buildings is part of that change. Passive House doesn’t explicitly consider the introduction and ongoing maintenance of more greenery both within the building and outside and around the building. We know from other research that green facades and green surrounds are critical to cooling the urban environment (making a difference of between one and 15 degrees), and that they act as important air quality filters as well. They also make people feel better and more productive in a workplace.
3. Can we actually build them?
There is a lot of debate about Passive House in the architecture and building industries in regard to whether the Australian building industry has the expertise to build a Passive House properly. Often projects start out with good intents, but with a lack of available materials (that are up to specified standards) and expertise, they don’t deliver on their design intent.
4. Living in a bubble?
A Passive House is a long way from the old Queenslander house design, whereby the house was raised and used a lot of cross ventilation to cool the interior spaces.
But are we more disconnected from the outside world and climate than usual by living inside a PassiveHaus? Is there an advantage to being conscious and connected to the world outside? The air, the sounds, the breeze that flows through a building, inherently ensures you are not living in a bubble. Anyone who has worked in the middle of a large office block will understand how disconnected you become from the outside world, and how disorientating it is to walk outside, thinking the sun is still shining when it is actually night time, or raining when it was sunny.
5. It’s more than just about buildings
Beyond just an energy efficient building, the core objective of Passive House, perhaps we need to focus on more than just building design in our move to a low carbon economy. One sustainable building/energy efficient building is good, but what about a whole precinct or suburb? What about the public spaces, the shopping centres, the food miles, and emissions from transportation, and so on. It is possible that we will have Passive Houses built in and around other inefficient buildings, infrastructure and open spaces. It isn’t an argument against Passive House, but more an argument to consider more than just one building at a time.
The rise in interest in Passive House is clearly a good thing in raising the profile of how much energy buildings and houses consume, but let’s not lose sight of the various other issues that create better cities.