How architects can use Passivhaus principles to unlock operational net zero carbon
The UK’s climate change targets mean that by 2030 all new buildings must operate at net zero carbon. That presents major challenges for architects – but designing to Passivhaus standards makes it achievable. Here’s how…
The challenge of operational net zero carbon
To operate at net zero carbon, a new building must power its lighting and appliances and regulate its temperature without contributing a positive quantity of carbon emissions in doing so. In practical terms, that means it will need to achieve an energy balance: producing enough of its own renewable energy (e.g. through PV solar panels and wind turbines) to cover its heating, cooling and electricity consumption, so that there is no reliance on the opaque industry of carbon offsetting.
Architects can achieve that energy balance through designs that minimise energy demand and enable ongoing energy conservation and generation. But – as we explained in this post – there are some major challenges here for designers. These include:
Meeting very stringent energy use targets – realistically, buildings will need to meet energy demand targets that are a third of the maximum levels demanded by building regulations. For example, domestic buildings will need to meet the LETI target of a Space Heating Demand equal to or less than 15 kWh/m²/yr; and a total Energy Use Intensity (EUI) – meaning the energy use measured at the meter – equal to or less than 35 kWh/m²/yr.
Incorporating innovative heating and electricity-generating technologies into the building design – to avoid any reliance on fossil fuels.
Annual measurement of the energy balance – to demonstrate that net zero really is being achieved in a building’s operation over time.
Finding ways to meet zero carbon needs without sacrificing practical and aesthetic requirements – architects will need to find ways to design beautiful buildings that meet client needs yet incorporate all the necessary ingredients for zero carbon.
How Passivhaus principles can meet the net zero challenge
Passivhaus is a leading international performance-based energy standard in design and construction which aims to significantly reduce energy use from buildings. To qualify as a ‘passive house’, a building must be built to five specific principles, and must meet strict criteria on space heating demand, energy use, airtightness and thermal comfort.
The five principles of designing a passive house
- No thermal bridging – ensure roofs, walls and floors are insulated with no gaps, minimising the need for artificial heating or cooling to reach a comfortable temperature.
- High-quality insulation – a fabric-first approach with a super insulating envelope with a targeted U-Value of 0.1W/m2K
- Superior windows – all windows must be Passivhaus certified and triple glazed, with a low thermal conductivity.
- Airtight construction – a super airtight envelope to eliminate uncontrolled internal-external airflow. Airtight tests must be equal or less than 0.6 air changes per hour @ 50 Pascals.
- Ventilation with heat recovery – a Passivhaus-certified MVHR system must be installed, to recover heat from the used air and transfer it to incoming fresh air, resulting in minimal energy loss and clean indoor air quality.
There are multiple benefits for users and residents of building to these standards, including improved health, wellbeing, affordability and market resilience.
But they also provide a proven way for architects to meet the operational net zero challenges and the stringent LETI energy targets such as a space heating demand of 15 kWh/m²/yr.
For example, the diagram below shows how we model a project in PHPP (Passivhaus Planning Package) to calculate the energy balance: all the losses through the envelope need to balance with all the gains (in this example ‘heating, 13’ indicates that the project is meeting 13 kWh/m²/yr).
Designing for net zero carbon
Net zero carbon is a huge and complex issue and operational net zero is only one element of the puzzle. Other dimensions include construction emissions, materials, durability of buildings, and developing the circular economy and smart local energy systems. We must also retrofit and adapt old buildings to achieve operational net zero.
We look at how we architects can address these issues in this article: 6 ways architects can help achieve net zero carbon in buildings.
But we believe that the Passivhaus principles provide a key for architects to unlock operational net zero for new buildings, and they will be a vital tool as we head into a future that makes climate change the top priority in architectural design.
If you would like to discuss any of the issues about operational net zero carbon or Passive House design raised in this post, drop us a line.
See also: