It is just over one year until the Scottish Government will introduce legislation requiring compliance with a new Scottish Passivhaus Equivalent Standard for new-build housing.

Given that passivhaus is generally considered to be the "gold standard" for energy efficiency in homes and buildings, this is a potentially radical and ground-breaking move that could transform the quality of newbuilds in Scotland.

However, despite this deadline looming, there is still significant uncertainty around what exactly the changes will entail and how they will be brought about.

Below, we take a look at what we know so far, and how we can expect the Scottish Passivhaus Equivalent Standard might be implemented in practice.

Origins of the changes

For those less familiar with passivhaus, in summary, it has been defined by its founders as the concept of designing and constructing buildings so that "the heat losses of the building are reduced so much that it hardly needs any heating at all".

The proposals for a mandatory passivhaus standard in Scotland for all new buildings was first introduced as a private member's bill, but was then ultimately adopted by the Scottish Government who have pledged to introduce legislative changes implementing the standard by mid-December 2024.

What will the standard look like

So far, all we know about the Scottish Government's plans is that they will take the form of secondary or "amending" regulations and are therefore likely to consist of changes to existing building regulations and standards.

However, the private member's bill proposals that prompted the Scottish Government's commitment to passivhaus also gives some insight into what the standard might look like.

Within the proposals it was stated that the purpose of the bill was "not to seek to prescribe materials or products or methods to achieve the standards set, but instead seeks to introduce new higher standards that all new build homes must achieve" . Reference was also made to the five key principles underlying the passivhaus standard as follows:

  • High-quality insulation
  • Heat control and robust windows
  • Building airtightness
  • Heat recover and ventilation
  • Thermal bridge free design

With this in mind, it seems likely that the Scottish Government will take an approach which is focussed on the end product, with the passivhaus standard consisting of a set of requirements that a new building must meet, rather than prescribing the way in which those requirements must be met.

It seems likely that a particular airtightness requirement will form part of the standard, with the currently recognised standard for passivhaus being less or equal to 0.6 air changes per hour. Indeed, it is difficult to see how the new Scottish standard could truly be considered to be a "passivhaus equivalent standard" without incorporating the 0.6 (or lower) benchmark. It is also likely that the other principles noted above will be reflected in some way within the standard, including a limit on thermal bridging.

How will the standard be enforced

One of the most important aspects of the new legislation will be around how the passivhaus standard is enforced.

Currently, the energy rating of a property is based on an estimate or model of how a designed building will perform in relation to energy efficiency. It is not based on an actual individual and verifiable assessment of each new build. In other words, there is no quality assurance by building control that the building, once built, will meet its estimated EPC rating.

This is likely to change under a new passivhaus regime, with buildings having to comply with the strict passivhaus certification process seen on existing passivhaus accredited projects (or something similar). This should mean that the potential as-built "performance gap" outlined above will not exist. Instead, the Scottish Government has confirmed that "the design and construction of new buildings must be supported by quality assurance and verification processes that result in buildings that meet the high standards set".

The proposal under the private member's bill was that this will be incorporated into the building warrant/planning process –it is difficult to see how a different approach could be taken if the passivhaus standard is to be enforced and developers held accountable.

It has been envisaged that passivhaus certification may add a step to the building warrant process, whereby the building is inspected and verified by the passivhaus certifier after it has been built, to confirm that the standard has actually been met.

This will, in turn, mean that there will be a need for more passivhaus verifiers. It is currently unclear whether these would sit within local authority building control departments, or whether developers will have to look to independent accredited passivhaus certifiers to have their buildings signed off. Regardless, this will spark the need for a significant amount of training and investment over the next year and beyond.

What's next?

As noted above, the Scottish Government are still to reveal much of the detail around what the Scottish Equivalent Passivhaus Standard will look like and how it will be implemented.

Consultations on the Scottish Equivalent Passivhaus Standard are anticipated for spring/summer 2024, when we may learn more about exactly what the proposed standard will consist of and how it will be implemented. We will be sure to update you once further details are available. In other words: watch this space!

Contributors

Lucy McCracken

Senior Solicitor