Climate change is one of the biggest threats we face today, as I wrote in a previous blog about ‘Zero-Carbon Buildings’. Clearly we need to reduce CO2 emissions globally to zero, or to less than zero, to address climate change. We need to approach this in two ways: radical energy efficiency to reduce demand and de-carbonisation of energy generation, in other words, a massive scaling-up of renewable energy generation.*
In some situations these two approaches are going to manifest as ‘Zero-Carbon Buildings’ or ‘Net-Zero Energy Buildings’. Even though there are many reasons why this is the wrong target (and if you read the comments you’ll find there are more than just the 9 reasons I wrote about.)
What then, is the best approach to achieving these notional targets of ‘Zero-Carbon Buildings’ or ‘Net-Zero Energy Buildings’?
Passivhaus First is the best approach and I explore why in this blog.
‘Zero-Carbon Buildings’ – Benefits of Less Demand
A radical reduction in energy demand, as delivered by certified passivhaus buildings, will significantly ease pressure on the electricity grid during peak demand. When buildings typically demand the most energy is likely to coincide with when renewable systems are generating the least, compounding the effect on the grid. (See point 5.) In the UK this is most likely in winter when heating demand is high and there is less solar energy and wind available to generate electricity. ‘Zero-Carbon Buildings’ that is predominantly run on electricity coupled with an increase in electric vehicles will put more pressure on the grid at a time of peak demand. However, if ‘Zero-Carbon Buildings’ are also passivhaus buildings, heating demand and other electrical consumption is radically reduced. This will significantly benefit the electricity grid during peak demand.
There is an additional benefit of radically reduced demand with a ‘Zero-Carbon Building’ that is also passivhaus. The need to generate more than just the buildings own demand is also reduced significantly. (See point 6.) A ‘Zero-Carbon Building’ needs to generate enough energy on site to meet its annual demand. However, as it still draws electricity from the grid part of the time, it needs to generate enough surplus energy to balance the carbon intensity of the grid. Less demand means less surplus generation is needed. And in turn renewable energy generation equipment can be reduced in size and cost.
‘Zero-Carbon Buildings’ – Benefits of Efficiency
Energy efficiency is more cost effective than energy generation, up to a point. And this is the point that the Passivhaus Standard is based on, the point of diminishing returns. Once the passivhaus standard of energy efficiency is achieved, primarily through the building fabric, then it is worth considering renewable generation for a building. That is why passivhaus is an important staring point for ‘Zero-Carbon Buildings’ rather than a lower standard of energy efficiency.
Energy efficient building fabric will last the lifetime of the building and continue to provide reduced CO2 emissions for ‘Zero-Carbon Buildings’. This is the most important starting point for a low emissions building to be based on. Renewable energy generating equipment is more dependent on maintenance, climate, location etc. than the building fabric.
This can be seen for example with the Bullitt Center in Seattle, which although it is not passivhaus, it is highly energy efficient. In a report published about the building in September 2014, calculations indicate that the building energy efficiency will save 323.47 metric tons of CO2 emissions over the lifetime of the building in comparison to 101.60 metric tons of CO2 emissions saved by the building mounted renewable energy system. The building fabric has three times the impact of the renewable energy generation.
This may of course change over time. Energy efficient building fabric locks in high performance and low CO2 emissions for the lifetime of the building making it vital to get right. It is unlikely that significant improvements and upgrades to the building fabric will happen at short intervals, if ever. Renewable energy generating equipment mounted on ‘Zero-Carbon Buildings’ in contrast will need replacing in just ten years in some cases. The upside of this is that with rapid advancements in renewable energy generation technology there may be opportunities for future upgrades. And it is much easier to upgrade renewable energy generation in most cases then to upgrade the building fabric!
‘Zero-Carbon Buildings’ – Additional benefits of Passivhaus
Passivhaus is a tried and thoroughly tested standard that delivers what it promises – radical energy efficiency and thus radically reduced CO2 emissions. If ‘Zero-Carbon Buildings’ are also passivhaus the performance and CO2 emissions can be trusted based on decades of evidence.
The Passivhaus Standard is not just a standard; it comes with a trusted and practical methodology for design and assessment. ‘Zero-Carbon Buildings’ and ‘Net-Zero Energy Buildings’ are mostly about a notional target and there isn’t much practical guidance or a trusted methodology available to get there yet.
Rigorous quality assurance is the hallmark of the Passivhaus Standard and an important reason for obtaining certification. If we are serious about reducing CO2 emissions and ‘Zero-Carbon Buildings’ being part of the means to do so, quality assurance is vital. Good intentions won’t prevent runaway climate change. And neither will ‘Zero-Carbon Buildings’ with a badge but unreliable or poor performance.
Passivhaus buildings are comfortable for people to occupy and use all year round by design; this is a core purpose of a building after all. Energy efficient buildings or ‘Zero-Carbon Buildings’ that are not comfortable will be both unpleasant and emit much more CO2 than predicted. People will use more energy and emit more CO2 as they heat, cool or ventilate the building more in an attempt to be comfortable.
Indoor Air Quality is linked very closely to comfort. Passivhaus buildings have a constant reliable supply of fresh filtered air that ensures excellent indoor air quality. The fresh air is pre-warmed by heat recovered from the stale air leaving the building ensuring comfort is maintained. We need to ensure that ‘Zero-Carbon Buildings’ also deliver excellent indoor air quality.
‘Zero-Carbon Buildings’ – Passivhaus First
The best approach to ‘Zero-Carbon Buildings’ is Passivhaus First. Whether you want to comply with legislation requiring ‘Zero-Carbon Buildings’ as the UK appears to be heading towards, or you wish to obtain ‘Net Zero Energy Building’ certification, passivhaus provides a powerful starting point with considerable benefits. Not only does the Passivhaus Standard ensure energy demand is radically reduced and energy efficiency dramatically increased, the standard also beings many other benefits. ‘Zero-Carbon Buildings’ need the quality assurance, comfort and excellent indoor air quality that passivhaus provides.
Architecture in the anthropocene must change for the good and must radically reduce CO2 emissions. And yet we mustn’t lose sight of our purpose in commissioning, designing and constructing buildings for people.
‘Zero-Carbon Buildings’ also need to be beautiful, comfortable and healthy buildings that deliver on their promises. Start with passivhaus.
For more on Passivhaus and on ‘Zero-Carbon Buildings’ please subscribe by email (just below my photo and profile) to get future blog posts direct into your inbox. Well, a teaser anyway, it’s never a full length blog that gets emailed out!
The Passivhaus Trust have produced a Technical Guidance paper on “Passivhaus & Zero Carbon Compliance” relating to anticipated UK legislation that is available to download as a PDF.