Passivhaus techniques and the climate crisis

We've recently been working on a series of Passivhaus retrofit projects (known as EnerPHit) and these drawings showcase the strategic moves made to upgrade a 1960s estate into a modern facility that significantly reduces operational carbon.

The decarbonisation of heating buildings through retrofit is challenging, however, these steps outline how we can substantially improve outdated buildings:

1. Assess the current condition of the building. This involves taking core samples through the existing envelope, calculating the U-values, measuring the existing thermal performance of the walls/roof/floor. This can be evidenced through carrying out thermographic surveys and airtightness testing.
2. Develop a strategy that wraps the existing thermal bridges (such as slab edge) consistently in insulation whilst ensuring that the dew point does not fall within the internal layers of the wall; this will mitigate damp moving forward. Create a continuous airtightness layer and improve the overall performance of components whilst developing a strategy for interface details (such as parapet, window heads/sills). Upgrade windows/ doors to triple glazing. There may be opportunity to optimise the existing glazed areas, though thermal modelling and physically changing window opening sizes.
3. Once the fabric has been addressed, look at eliminating the use of fossil fuels for heating and hot water. Optimise renewables such as PV's, air source & ground source heat pumps, to limit operational costs and reduce reliance on natural gases for heating.
4. Introduce external horizontal brise soleil above south-facing windows and vertical brise soleil on the side of west/east windows. This prevents overheating in summer months whilst making use of lower sun during winter months to naturally heat the building.

The beauty of this approach is that it can be applied to a wide range of building types such as, houses, multi-story flats, hospitals, schools, universities, civic and commercial buildings. We're applying this strategy to whole campuses and building estates with similar construction, aiming to upgrade them cohesively.

The resulting building performance from the retrofit measures depend significantly on careful detail design, specification of materials and rigorous execution of the construction. This requires enhanced quality control, evidencing the specific materials have been used and inspection on site. For some procurement methods this can be more challenging, but still achievable if planned in early enough into the project requirements. This is why the use of accredited and certified methods are utilised, such as Passivhaus, as it provides a structured approach, testing with modelling software and a methodology to design and construct to, overseen by a third party certifier.

There are many important reasons to retrofit. When developed with a great design team, the finished product will feel completely new without the headaches of lengthy programs, planning, and the risk of inflation trying to derail almost any new build project. On top of this, the embodied carbon saved in re-using the existing structure means that deep retrofits provide a truly sustainable solution to reaching Net Zero.