First of all, what does passive design actually mean? Put simply, designing passively means taking advantage of the local climate to provide internal comfort for occupants. Buildings are designed to maintain a comfortable temperature using climatic and natural elements to optimum effect, thereby reducing or eliminating dependence on mechanical systems for heating and cooling. This in turn reduces energy demand and associated CO2 emissions.
For example, one of the biggest problems the UK built environment is likely to face through climate change is overheating. In fact, it is a problem that many developments in London are already facing and as a result they often incorporate some form of comfort cooling. However, we need to ensure that cooling does not become the first and only solution as, amongst other issues, this will end up increasing energy use (we will explore the issue of ‘maladaptation’ in a future blog post). This is where passive design comes in. After all, passive design is not about minimising or maximising solar gain to reduce cooling or heating demand but about optimising solar gain – that is, carefully balanced so that it is beneficial.
Sounds like a pretty effective and sustainable way to design a building (certainly the Swedes and the Germans have embraced the concept) – so why has is not become more of a standard approach in the UK? In part it is due to a misunderstanding of its versatility. If you mention passive design, most people would picture a singular “eco”-house that is extremely air tight, has unusual geometry and window placement, and probably has an array of ‘innovative’ technologies. Few would picture a high-rise, curtain-walled residential or commercial building in a city centre!
However, we believe that passive design can be incorporated into any building without the need for expensive technologies or certification. The basic principles of passive design (orientation, overhangs and shadings, insulation, windows and thermal mass) are usually already considered in the design of any building, regardless of its size or its intended use. What is required is a shift in the discussion to recognise, acknowledge and incorporate the passive benefits of these principles.
So how do we move the passive design discussion forward and ensure that future buildings are designed with consideration for its principles?
Firstly, early conversation is crucial. Several of the principles relate to the placement and massing of a building or buildings and are therefore heavily impacted by early design decisions. Utilising the orientation of the building to balance natural light with solar gains can have huge benefits in terms of minimising the risk of overheating, but unless it is considered at an early stage the opportunity will likely be lost.
Secondly, educating design teams, developers and particularly occupants is required. Many passive design buildings do have very low heating demand and so it is feasible that future buildings could be designed with no heating system at all. This is a total change from our traditional design approach in the UK and is very different to what we know and expect as occupants. Without knowledge sharing there would almost certainly be a concern amongst occupants that their home would be cold in winter. Similarly, with an ever-increasing desire for oversized windows to maximise light and views the risk of overheating intensifies, and with it the need for cooling. To mitigate this passively, it is likely that we will need to either reduce the proportion of glazing (never desirable by architects nor developers!) or accept external solar shading as standard design practice for our buildings. This however needs a shift in aesthetic expectations by not just designers and developers, but critically planners.
In short, we need to start designing and building responsibly for a future climate – and not just the current climate – because as our climate changes our buildings are going to need to perform well in the warmer months as well as the colder months that we’ve long been used to.
Obviously passive design alone is not going to solve the climate change adaptation problem and so next up in our series we are going to consider the impact of urban greening.