Scottish housing design is on the verge of major change. The Heat in Buildings Strategy, and the associated New Build Heat Standard 2024 require that any new buildings applying for a Building Warrant after 1st April 2024 with an installed heating system will need to be zero direct emissions heating (ZDEH). While recent press reporting has focused on a delay to the phase out of gas boilers in existing properties, in the same announcement, Patrick Harvie MSP reported on plans to regulate to ensure that minimum energy standards are met for both private and owner occupied houses (by 2028 and 2033 respectively). And alongside the consideration of low carbon heat, there is Scottish Government commitment to the development of a “Scottish equivalent to the Passivhaus standard” which will apply to all new housing.
These all sound like promising steps forward for the low energy building sector, and for the quality of housing in Scotland, but will it deliver better homes, which are cheaper to run?
It is encouraging to see energy standards being considered alongside zero carbon heat as, in our experience, it is not sensible to consider low carbon heat in isolation. If the design of the building does not minimise heat loss through the fabric, and maximise solar gains through the glazing design, significant heat energy input is still required. When this heat energy is provided by low carbon heat options, this could in fact result in an increased financial cost for heating. As designers of nearly 200 certified Passivhaus homes and buildings, we know that rather than just turning to technology, the far better solution is to first drive down the heat requirement as far as possible through a well-designed and airtight fabric, which keeps energy use down and therefore costs low. This is particularly key in a Scottish climate, and so we’re hugely encouraged by the development of a Passivhaus based approach to housing design.
A Scottish Passivhaus solution
Support for the Passivhaus standard in Scotland has grown dramatically over the last few years. Until very recently, Passivhaus in Scotland was the domain (pun intended), with some notable exceptions, of the single dwelling house, or small residential developments. Now we are seeing significant numbers of large and complex buildings being designed and built to the standard, largely as a result of the Scottish Futures Trust funding programme encouraging verifiable in use performance for new schools. In the domestic sector with the Domestic Building Environmental standards (Scotland) Bill, and the Scottish Government’s subsequent commitment in 2023 that, within two years, legislation would be created to introduce “new minimum environmental design standards to meet a Scottish equivalent to the Passivhaus standard”, the Passivhaus standard is now at the forefront of discussions.
In addition to providing a means to achieve compliance with legislation, the Passivhaus standard has huge benefits for the development of multi-home residential developments by local authorities, Registered Social Landlords and housebuilders, including reduction in energy use, ensuring quality and performance as promised at design stage, avoiding fuel poverty and providing a comfortable, healthy environment for tenants and residents. Critically, it also future proofs our housing stock – housing that is built to the minimum standards today will require complex, costly upgrades in future to meet our net zero targets. Surely, it’s much easier to get it right in the first place.
The nature of Passivhaus as a quality and comfort standard also has the opportunity to offer huge benefits. There have been well publicised tragic impacts of damp and mould in dwellings, and, while damp and mould can have a range of contributory factors, condensation and inadequate ventilation are key elements. Designing to Passivhaus ensures optimised levels of ventilation (even in the winter, when we tend to keep our windows closed more) and eliminates thermal bridges (which would manifest as cold spots, where condensation could collect). During construction, the quality assurance aspect of the Passivhaus standard ensures that thermal bridges don’t appear through shoddy construction (it’s not unheard of in standard construction for whole areas of insulation to be missed!). A recent article in the Guardian also highlighted the woeful state of Britain’s mass house building industry – because of an independent certifier of build quality, Passivhaus can help housebuilders and homeowners avoid shoddy workmanship and achieve the intended level of quality.
When any new change is introduced there can be initial fears about increased costs and a change to usual ways of working.
The Passivhaus Trust has undertaken various pieces of research, with their latest report concluding that while current best practice is 9% over ‘standard’ cost, “Passivhaus projects in the UK can be achieved for a modest extra over cost likely to be around 4% or less once adopted at scale”. This is supported by the view of Emma Osmundsen, an experienced client, who, speaking of her experience in delivery of Passivhaus housing at Exeter City Council, is quoted in Inside Housing Magazine as saying: “If you’ve got a good designer that understands building physics and form factor and orientation, what we’ve been able to demonstrate is that you can virtually eradicate the cost of building to Passivhaus”.
This would echo our experience, which indicates that Passivhaus can be delivered within existing standard build cost metrics, with costs quickly recouped through reduced running and maintenance costs. If Passivhaus building costs do seem higher, it is worth considering other variables such as site abnormalities, late adoption of the standard, high inflation or unnecessary complexity in the design.
Upskilling an industry
What we have seen in the Scottish construction education sector is that if the appetite is there, then upskilling can be achieved in a remarkably quick timescale. Scotland has gone from a standing start with the first Passivhaus nursery school starting on site in 2020 to having multiple Passivhaus schools in design or in construction within a period of three years. This is a remarkable turnaround, and a testament to the design teams, contractors and their supply chains who have invested significantly in training. To assist with this swift upskilling, in Scotland we have an incredible resource at BE-ST, which is providing training through the Open Learning Academy. At Architype we also work hard to assist site teams through the provision of tool box talks for site operatives.
There are lots of reasons to be optimistic in Scotland right now. The recent Passivhaus Trust conference had the tagline ‘Scotland Leads the Way’ and as a nation it has taken bold and necessary steps to combat climate change and improve the way we live. We hope other countries take note.
 Olly Wainwright: ‘Cracked tiles, wonky gutters, leaning walls – why are Britain’s new houses so rubbish?’ 21/10/23, as accessed 23/10/23.
 Passivhaus Trust, ‘Passivhaus Construction Costs’, October 2019