Clare and Ross Booth from Coldwells Build share details of their prefabricated, turnkey Passivhaus designs that aim to simplify the delivery of high performance homes in Scotland.

Interview with Clare and Ross Booth

Ross and Clare Booth are the founders and directors of Coldwells Build in Aberdeenshire, Scotland. Ross started out as a joiner and construction worker while Clare has a background in journalism and communication. Their construction company has delivered a number of bespoke housing projects and is now launching a range of contemporary, turnkey Passivhaus designs which will be sold at a fixed price and prefabricated off site.

This episode is set against a backdrop of potential change to the building regulations in Scotland.

Help keep the Scottish Passivhaus equivalent on track

Last year the Scottish Government announced plans to introduce new regulations for all new build housing to meet a ‘Scottish equivalent to the Passivhaus standard’.

Whilst this was exciting, the devil is in the detail and this is currently being fleshed out in a consultation about the proposal. Unfortunately there are signs that it may be watered down, which means we need to have our say and get it back on track. So please take the time to respond. The Passivhaus Trust has made it easy to understand what detail is lacking, so check out their guidance to help you play your part in the consultation.

The ‘Passivhaus equivalent’ doesn’t need to reinvent the wheel

The Passivhaus standard works so well because it is a holistic approach which addresses building physics, and there are quality assurance processes built in so that we get the results we anticipate.

Clare says that adopting the Scottish equivalent to the Passivhaus standard could have a profound effect on future homes across Scotland, and help the Government reach its net zero emissions target set for 2045.

Upskilling the workforce is essential

Clare and Ross believe that for Scotland to achieve higher building standards there is a great need to provide additional training for construction workers. Ross shares an example from his own experience as a joiner when he installed an airtightness membrane but didn’t really understand what it was doing or the attention to detail required when carrying out this work.

Clare and Ross have both upskilled as part of their professional development

While networking Clare discovered that some free Passivhaus tradesperson training was available and sent the whole team to Glasgow to attend. Ross admits that he was sceptical at first but was completely converted by the end of the training. This was Government funded and provided by BEST (Built Environment Smarter Transformation) who are working to decarbonise the built environment through upskilling and educating people in the construction industry.

Clare also attended a number of satellite events at the COP26 global climate change summit in 2021. Amongst her findings was that most homes still rely on oil and gas for heating which is contributing to nearly a fifth of the UK’s carbon emissions, the UK has some of the worst insulated housing stock across Europe, and that the performance gap currently sits at a staggering 60% in some cases.

A ‘bespoke’ home project is not a simple process

Having worked with numerous clients on one-off bespoke projects, Clare and Ross have identified key pain-points in the self build journey. For example, it can be difficult to design projects within budget and so clients need to go back and forth between their designer and the construction team until they have refined plans. There’s also fatigue from the estimated 3000 decisions that are needed to realise a new home. Then add in the unpredictability of the build itself, which may be subject to bad weather delays and noise complaints from neighbours.

Building off-site in a workshop is a lot more predictable

In an attempt to address some of the challenges of self build and streamline the process for their clients Clare and Ross decided to create a collection of predesigned homes that they would sell for a fixed price. Not only would these be beautiful contemporary homes but there would be a set number of materials and colour choices, making it easier for clients to choose. Another big change would be taking advantage of modern methods of construction by prefabricating these houses off site in a workshop. This also has the potential to increase quality as everyone can be trained in specific roles.

By increasing the insulation specification, their Passivhaus designs can work anywhere in Scotland

Over the last two and a half years Ross and Clare have been working with John Gilbert Architects to produce six ready-to-go Passivhaus designs.

As Passivhaus is site specific one challenge they faced was how a standard design could work on any site. The solution was to over-egg the insulation slightly so that the solar gains were not as critical.

We’ve got quite a chunky wall and roof system. And we’ve tested the house on PHPP on a coastal exposed site in the North East of Scotland, and we’ve tried it in every orientation, and it’s passed.

A building plot is essential to start the process

Although you might be tempted by the designs you need to have secured a building plot before you can engage with Coldwells Build. After selecting a house design they will check that it works for your budget, before moving on to a concept agreement.

At this point it is possible to make a few internal layout changes, providing that they don’t lead to structural changes. The team will then prepare a site plan and get everything cost checked and prepared for planning permission.

Once planning has been approved, Coldwells Build will create a preliminary building agreement and you can start looking at the internal finishes and kitchen designs. They will get the cost as accurate as possible at this stage and then the architect will submit for a building warrant. Once this has been approved, the client can sign a building contract, and the prefabrication will begin.

Assembly ‘on site’ will take a matter of days

Ross says that prefabricating the home would start within three months of having a building contract signed. Whilst the prefabrication is happening, the groundworks team can be on site, preparing the foundations, substructure and floor slab. Once the timber frame is delivered to site, it can be made wind, water and airtight within days. The cladding will be pre-installed and the wall panels and roof panels pre-insulated. The airtightness membranes will be pre-fitted, and only the joints will need to be taped on site. It is a quick turnaround from arriving on site.

The costs will be fixed and known upfront

Clare says that the average price for their four-bedroom turnkey design will be around £420,000. There is also a ‘You Build’ option, which gives you a completed shell that you would then have to fit out, and this is currently around £220,000. Again this is for a certified Passivhaus, which is core to their offering.

The Passivhaus collection will be launched next month but there is already a lot of interest and they even have a waiting list! So it’s an exciting time for Coldwells Build. They are currently working with their first customer which they will use as a test run and to check all their processes, before taking on more customers. Initially they are going to be limiting themselves to producing six houses per year. Clare explains that the most important thing is not to overload themselves and therefore ensure the quality of their homes.

Find out more

Visit the website of Coldwells Build

Transcript

Download a transcript of this episode

Please connect with us

Subscribe, rate and review us on Apple Podcasts

Like our Facebook page