Beyond Net Zero: Passivhaus in practice - reflections from delivery
Contributor
Cammy Sriram
MMath
Passivhaus Designer
Passivhaus focuses on designing and delivering high-comfort, low-energy-use buildings that close the energy performance gap. The energy targets set by the standard are consistent with designing a built environment that responds to the climate emergency.
This is an extended version of an article originally published in our Beyond Net Zero whitepaper in April 2025. To read the full whitepaper, click here.
Early Adoption of Passivhaus
Projects have the best outcomes when Passivhaus is considered from the outset. On the Two Rivers Primary School, we were involved from the bidding stage and were able to provide a good level of cost-certainty right from the project outset. Backed by initial modelling in the Passivhaus Planning Package (PHPP), we identified and improved key junctions affecting heating demand, advised on the most effective use of insulation in the walls, and guided the team towards a cascade ventilation strategy.
The PHPP serves as a useful tool during design development, giving quick feedback on design options, a feature we used to good effect on Passivhaus certified multi-residential project, Greenhaus, in Salford. We worked with the contractor throughout the design stages to rationalise the design, and our study on the impact of thermal shims behind masonry support brackets saved around £200k from the design cost.
It's essential for the delivery of Passivhaus projects that the contractor is on-board, and the design team have a key role in setting contractors up for success on site. We believe that construction quality starts in design, and when the design and the site processes are right, the results can be excellent. We’ve achieved very good levels of airtightness on our CLT projects. Lucy Cavendish College recorded an air permeability of 0.42 m³/m².h @ 50Pa in its final air test, achieving exceptional energy performance. Passivhaus is as much about the process as the end result. If adopted early, the principles and targets provide clear goals for the team, allowing PHPP to be used as a tool to inform design development and help make cost-effective decisions. During construction, it fosters good practices on site in terms of quality of workmanship.
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Comparing two of our projects (Lucy Cavendish and Cranmer Road) to non-Passivhaus projects built to industry good practice standards. In-use energy performance on the Passivhaus projects is significantly better.
Achieving Energy Efficiency Through Passivhaus
We’ve delivered Passivhaus buildings across varying typologies and have an appreciation of the wider benefits it can bring to designers, contractors, and end users. Lucy Cavendish College, new-build student accommodation which achieved Passivhaus Classic Certification in 2023, has been outperforming industry benchmarks and our own non-Passivhaus projects. Passivhaus certification is awarded around practical completion and we always recommend post-occupancy evaluation (POE) and aftercare services to review the operation of the building and help with fine-tuning.
Agar Grove, the first Passivhaus development of its kind in the UK and which sets a new standard for social housing, has meaningfully tackled fuel poverty by reducing residents' fuel bills by 70% and has influenced changes to the London Plan in relation to district heat networks.
Our EnerPHit (the Passivhaus retrofit standard) projects have shown similar savings in energy use. The Entopia Building, the UK’s largest EnerPHit certified office building, saw an 86% reduction in EUI post-retrofit. POE data from the first 12 months of operation shows the building performing better than predicted and with performance aligned with the UK Net Zero Carbon Buildings Standard (Pilot Version) 2025 and future years’ targets for a “one-go retrofit”.
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"The high-quality working environment is energising and invigorating for our staff, including elements like outdoor spaces, natural light, and task-based lighting. We continue to monitor and track quantified data to understand how good the internal air quality is compared with external ambient air, but anecdotal evidence from some asthmatic staff indicates that they feel less reliant on their inhalers when they are working in the office."
A Sustainable Energy Solution
As we move to net zero carbon and an all-renewable grid, we feel EUI shouldn’t be the only metric considered, as it doesn’t consider the availability of local renewable energy sources or seasonal variability. Efficient energy use (i.e. reduced power wastage and storage losses) will be needed for affordable renewable energy as demands on the grid increase.
On-site generation by renewables can be part of the solution, but has its limitations. This is demonstrated in the POE data from Two Rivers Primary School, which has PV panels on the building generating 93% of its annual electricity demand. Around two-thirds of this electricity is used by the school, and the remainder is exported to the grid. Passivhaus promotes efficient use of energy through its energy demand metric, the Primary Energy Renewable (PER). It factors in storage and distribution losses and focuses attention on reducing energy demand when electricity is less available.
The performance on Passivhaus projects, the Entopia Building and Agar Grove, prove that targeting the standard helps to deliver sustainable buildings for the future, benefitting end users and the planet, and provides a rewarding experience for those involved in design and construction.
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Annual energy summary (kWh)