Passivhaus principles present an effective guide to building regulation compliance
The increased cost of living continues to highlight the need for energy-efficient properties, and energy professionals are under more pressure to consider the thermal performance of building components. Steve Tonkiss, Head of Sales South at REHAU UK, explains how Passivhaus performance criteria can be used as a set of design principles to assist in the implementation of building regulation updates.
Built environment professionals are under mounting pressure to consider new heat loss-reducing factors when choosing products for new-build or refurbishment projects. The overarching driver comes in the form of the Future Home Standard (FHS), in particular, updates to Part L covering energy efficiency. These new updates emphasise the importance of specifying compliant components for all aspects of a build.
The integral part that windows play in a building’s energy rating was highlighted by a Citizens Advice’s warning that families could see 30% of the energy they pay for disappear through windows, doors, and roofs1. This loss can be prevented by selecting high standard products. For example, installing high performing double glazing into a semi-detached gas-heated property could result in annual savings of up to £175.2 These reported improvements underline the potential of windows within this arena and demonstrate why energy professionals working on public projects should similarly consider the frames used to uplift energy retention on social housing, offices and other structures.
This pressure to ensure buildings are futureproofed against increasingly strict environmental legislation is a main driver behind the growing popularity of Passivhaus-certified buildings. Materials and design aspects of a project are being further analysed to futureproof in a sector that can expect further changes to public building laws as the demands for nation-wide net zero emissions accelerate. As such, Passivhaus, a concept that was once considered a ‘radical’ approach to futureproofing, can now be seen as a technical guide for improving a building’s thermal efficiency and implementing sustainable design.
What energy professionals need to know
A low-energy design standard developed in Germany, buildings constructed according to Passivhaus strive to achieve thermal comfort by post-heating or post-cooling the fresh air without the need for additional recirculation. High-quality windows are one of the key components for achieving the Passivhaus required levels of airtightness, insulation, and overall efficiency. When compared to more traditional designs, they must achieve outstanding thermal performance.
Certified projects are principally new build, mainly due to the ease of implementing principles within the building design process. However, it is widely accepted that existing properties need significant improvement. This has led to the Passivhaus Institute creating the ‘EnerPHit’ certification, debunking the belief that the standards are limited to very difficult or expensive builds.
One of the most important takeaways for energy professionals from FHS uplifts is that Passivhaus principles can successfully inform window specification within new builds or retrofit projects without full certification. REHAU, for example, can point out a window’s different junction points, which consultants can use to make the necessary calculations to meet the standards.
Providing a technical steer
While seemingly hard to achieve, Passivhaus requirements can instead provide a technical steer for improving a projects thermal efficiency and sustainability. When applied to buildings in the public realm that are subject to ever-increasing performance standards in design, Passivhaus’ strict requirements can assist in meeting such regulations. When viewed as a spectrum, these standards can be adopted across a broad scope of structures, even if the build doesn’t meet the highest standard or achieve official certification.
Solar gains can be a key contributor to the thermal efficiency of a build and the possibility of overheating must be considered. Window positioning and orientation also often plays an integral part when it comes to reaping the available benefits to assist the heating of a building. However, when it comes to Passivhaus buildings, despite what is often believed, they do not seek to minimise heat loss and maximise solar gains. Instead, they work to optimise the latter to achieve overall comfortable and efficient conditions inside the building and eliminate the potential for overheating. Considering the window’s critical function providing daylight and ventilation while adding to a building’s aesthetic, energy professionals should not specify frames based purely on their ability to heat a building.
When it comes to measuring the thermal performance of a window, the U-values, which are used to quantify how buildings conduct or transfer heat, should be considered. It must be noted that when using the UK’s existing window energy rating (WER) system, Passivhaus windows may only achieve a ‘B’ standard. This can lead to the assumption that standard ‘A’ rated windows are superior, but this is not correct when it comes to thermal performance. On this metric, certified windows always outperform those that are not when it comes to heat retention. Instead ‘whole-frame U-values’ should be measured rather than the WER system when specifying windows for Passivhaus.
Heat retention is a key factor in Passivhaus certification and can be improved through the use of a frame with high airtightness, as it minimises uncontrolled air movement in and out of a building. A topic that was once lacking clarity within the wider building industry, it is now seen as one of the most important objectives of any project, being key for energy efficiency and thermal comfort. A windows design profile can assist airtightness, for example REHAU’s GENEO system was created with a flat base on the outer frame. This allows installers to adhere a sealing solution or airtight membrane to the window, eliminating potential air leakage.
Assisting Queries
Given the technical detail involved, around frames, it is critical to involve window specialists at the earliest stages. This will ensure projects are certified without difficulty, eliminating the chances of incorrect and costly specification before building commences. REHAU, for example, offer its GENEO system as a Passivhaus compliant window solution for specifiers looking to improve a property’s thermal performance. Considering U-values, airtightness, and heat recovery to increase efficiency, the design of such systems is an example of an inclusive option for the addition of Passivhaus strategies within a range of projects.
Additionally, in response to a lack of clarity around the certification standards, REHAU has created a new report demonstrating the impact informed window specification can have on sustainability and energy efficient performance. Highlighting technical points that specifiers need to be aware of, it also highlights the principles’ values in providing a technical steer for improving building efficiency even without full certification. The guide covers new builds and retrofit to explore the possibility of using the standards across a range of properties.
Features that underpin Passivhaus properties are becoming standardised by proposed and ongoing changes to public building legislation. Windows are often a smaller component in traditional builds, but the same cannot be said for structures aiming for greater sustainability in line with the design principles. The certification’s requirements have previously been viewed as too demanding to be adopted fully. However, they can now provide a guide to streamline a properties thermal efficiency in line with updates such as those within the FHS. If energy professionals want to stay ahead of the regulatory curve they will have to respond in kind and can use Passivhaus standards as guidance to do so.
To access the REHAU Passivhaus guide, click here.
1 https://theenergyst.com/draughty-homes-leak-a-third-of-energy-spend-out-of-the-window-citizens-advice-warns/
2 https://energysavingtrust.org.uk/advice/windows-and-doors/
