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Sheepridge Passivhaus: A Passivhaus Self-build Home fit for an Architect

Architect Jane Simpson has known Green Building Store’s founding director Bill Butcher for 29 years. So, a few years ago, when she and her husband, Paul Niven, decided to self-build their next home with the comfort they wanted and would deserve in their retirement, they reached out to Bill for his opinion on what to do. 

Jane admits, “We weren’t initially going to do a Passivhaus at Sheepridge, but after conversations with Bill about our original design, we were sold on the concept and realised the potential that a Passivhaus self-build had for us and our needs.” So it was that our Passivhaus project at Sheepridge was born.  

In this blog about the Passivhaus self-build project at Sheepridge, we will discuss the plans for the project and the early stages of the construction so far.  

Why is Sheepridge such an important project for Green Building Store?  

As mentioned in our last blog, Sheepridge marks a significant milestone in the history of the Green Building Store as it will be the final local Passivhaus built by our in-house construction team. For the last fifteen years, our dedicated in-house building team, led by our founding director Bill Butcher has pioneered Passivhaus building and knowledge in the UK through its local Passivhaus construction projects. These projects were key in allowing us to become a true authority on the principles of Passivhaus building in the UK. 

From building the first UK traditional construction Passivhaus at Denby Dale and founding director, Chris Herring helping set up the Passivhaus Trust, Green Building Store saw the potential of low energy building and Passivhaus principles and their impacts in the UK long before others. Indeed, as Scotland looks to adopt Passivhaus standards more widely, new build policymakers across the UK are still playing catch up with our visionary thinking some 15 years later.  

We launched our Passivhaus services in 2009, and in that time, through the local projects we have built, we have used our in-house construction team’s hands-on research and development to better understand the first principles of Passivhaus building. This wealth of knowledge on ultra-low energy efficient building, which now exists throughout all our services, convinced Jane and Paul to reach out to Bill with their plans for Sheepridge.  

With Passivhaus knowledge firmly established as one of GBS’s key values and with our services stretching to all parts of the UK, it was realised that the construction arm of GBS had run its course and that Jane and Paul’s self-build home at Sheepridge would be our last-ever in-house construction project in the local area. 

GBS will continue to develop our UK-wide services by providing an enhanced supply chain for the delivery of low energy buildings that will include the essential components; high-performance windows and doors, MVHR systems, airtightness products and specialist insulation. Helping to make buildings better across the country by ensuring they are more comfortable, healthier, and energy efficient places to live. We firmly believe that few others can rival our understanding of low energy residential buildings and how to create homes that are the best place they can be for inhabitants.   

Whilst Sheepridge is the last project by Green Building Store’s inhouse construction project, our in-house construction team’s Site Manager, Jude Wilson, who has been pivotal in the success of our local Passivhaus builds, will form a new entity using our other trading name Green Building Company Ltd. This new company will continue to build Passivhaus and ultra low energy homes and in doing so continue to share the practice of what Green Building Store has researched and developed over the last fifteen years. So, whilst a significant marker for many, Sheepridge is both a beginning and an end of something special and something we are extremely proud to have played such a significant role in – the development of Passivhaus building in the UK.  

Replacing a 1930s bungalow with a self-build for the future.  

Jane and Paul’s original home on the Sheepridge site was a 1930s bungalow (pictured below) which they had lived in since 2003. Thirteen years ago, they built an office and garage on the site for Jane to work from. However, Paul and Jane decided to rebuild at the same location and create a home for them both in retirement.  

Whilst the original design by Jane, which also included input from Stefanie Stead from Otley-based Stead and Co Architects, had planned to use the same SIPs system that had been used for Jane’s offices, it became clear to us that this system would not be meet the Passivhaus standards for the design so an alternative solution would be needed.  

Rendered timber façade – Something a little different for Green Building Store  

Since we built the UK’s first traditional construction Passivhaus at Denby Dale, we have become specialists in masonry built Passivhaus buildings. Indeed, it is what we are best known for. So, when we were approached with the rendered timber façade design for Jane and Paul’s home, it allowed us to explore something different and assess the options available for such a build.  

In the project’s early stages, we conducted an exhaustive economic analysis of potential ways to build their design; however, after concluding that the original SIPs design was not suitable due to a combination of reasons to achieve Passivhaus standards, we analysed and considered several other offsite timber framed panel systems instead. Quantity Surveyor Siu Fai-Lam from ROQS joined the project and completed an economic analysis of workable solutions for the house. However, In the end, the solution from Nelson-based Buildakit was chosen. 

Building with Buildakit  

Buildakit delivers a closed panel system in fully insulated kits from its state-of-the-art manufacturing facility in Lancashire. From the start of the relationship working with Buildakit, they were extremely accommodating in helping to create a bespoke solution for Jane and Paul’s design.  

Several reasons contributed to why the original SIPs design was not suitable for Passivhaus standards. In particular, the inclusion of a large veranda in the original design, a lack of glazing on the south side of the house, low solar gain, and the form factor of the planned building meant that extra insulation, a wood fibre vapour open system, was needed to be incorporated to meet the Passivhaus standards. Consequently, the original design plans had to be adapted and resubmitted to building control to have accurate working drawings available for the build. 

Architectural Technician Ashley Bamford from Bamford Architectural redrew the plans along with input from Green Building Store’s Bill Butcher on the detailing required for the Passivhaus standards. Such changes to the drawings emphasize why it is important to always consider Passivhaus design as early as possible and before designs are drawn.  

The Benefits of offsite panel systems like Buildakit  

Using an offsite panel system for any building has numerous benefits, but these factors make them particularly good for ultra low energy and Passivhaus buildings.  

  1. Energy efficiency: Offsite panel systems have high thermal insulation properties, resulting in reduced energy consumption for heating and cooling, leading to lower utility bills.  
  2. Quick construction: Offsite panels are prefabricated, as the name suggests, offsite, allowing for faster construction than traditional building methods. The panels can be quickly assembled, saving time and labour costs.  
  3. Design flexibility: Offsite panel systems can accommodate various architectural designs and floorplans. The panels can be customised to fit specific building requirements and incorporate openings for doors, windows, and other features.  
  4. Structural integrity: Offsite panels provide excellent structural strength, enabling the construction of durable and stable buildings.  
  5. Reduced waste: Since the panels are pre-cut and assembled off-site, minimal waste is generated during construction compared to traditional methods.  
  6. Improved indoor air quality: The airtightness of offsite panels helps to reduce air infiltration, which can enhance indoor air quality by minimising the entry of pollutants, dust, and allergens.  

Further benefits of using an offsite panel system manufactured from timber and combined with the use of woodfibre insulation, make a significant contribution to locking up CO2 within the building for 60 – 100 years plus. While eventually, the building will reach the end of its life and could be replaced by another, there is a significant opportunity if we choose a built environment that is constructed from cellulose-based products to lock up hundreds of thousands of tonnes of CO2. 

Airtightness at Sheepridge  

An Air Test or Air Permeability Test is used in Passivhaus building to determine the total conditioned air lost through leaks in a building’s envelope. In the UK, all new developments have been required to have an air test, as stated in Part L of the building regulations, since 2006.  

For a Passivhaus like Sheepridge, airtightness standards are significantly more stringent than those for traditional homes. A Passivhaus must not have air changes per hour greater than 0.6 m3/hr.m3 @50 Pa.  

Passivhaus projects are tested using a different method than most other builds in the UK. The most common practice measures the volume of air passing through a fan per hour to create an imposed pressure differential of 50 Pascals (Pa) which is then divided by the envelope area in square metres. This results in an Air Permeability measured in m3/h.m2 @ 50 Pa. However, for Passivhaus builds, an air test is calculated using the volume of the building as opposed to its envelope area. This is expressed as m3/h.m3 @50 Pa.  

In a Passivhaus build, it is the sequencing of the air test which is paramount. Ideally, the first air test should be conducted as early as possible in the construction while the airtightness strategy is still accessible. The air test wants to be conducted when the construction team still has access to the air strategy measures, like tapes and membranes, so that they can, if necessary, be altered. The first air test should certainly be done before the second fix on the project. It is also preferable to conduct the air test when the windows are in place, which is what we did at Sheepridge. The first test results at Sheepridge had a very impressive result of 0.28 lower than 0.6 m3/hr.m3 @50 Pa standard expected. 

What’s Next?  

The construction is well underway at Sheepridge, so keep your eye out for more blogs on the project, where we will discuss the windows and doors installed by GBS, the MVHR system designed by GBS, and the heat pump system which is being installed by our sister company Green Building Renewables.   

We also hosted two Passivhaus Summer Open Day events at Sheepridge for architects and self-builders to visit the site.

If you have any questions about the project, please don’t hesitate to get in contact. 

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