Steel Farm is located near Hexham in the North Pennine Area of Outstanding Natural Beauty (ANOB). Built using traditional construction technology it is the first Certified Passivhaus in Northumberland and national winner of the Small Project Category at the UK Passivhaus Awards.
A reinterpretation of the traditional Northumberland farmstead materials and form are in harmony with the region. Windows are proportioned and positioned to act as the eyes to the world, playfully revealing views and vistas at critical moments. This nuanced design, constructed using a sensible budget, culminates in a vibrant home with a distinct sense of place.
As organic farmers Trevor and Judith Gospel owned a plot of land where they dreamt of building a comfortable home that could accommodate them in their old age and minimise their impact upon the environment. More than anything Trevor and Judith longed to build their own home so their grandchildren could come and stay.
In the mean time they rented a small, gloomy bothy with damp walls and mould in the bathroom. There wasn’t enough space for their grandchildren to stay over, and to make matters worse in the bitterly cold winter of 2011, they found that the inside of their fridge was warmer than in their living room. As if that were not bad enough the wood burning stove spewed soot and particulates into the living room. It would be fair to say that the bothy was unsuitable for habitation.
Finances were tight so careful consideration had to be given to the budget at all times. …so even if they were desired elaborate, self-indulgent architectural gestures could not be afforded. The remote rural location, limited access to utility mains, and onerous planning restrictions incurred significant costs and have strongly influenced design.
A number of conditions imposed by the local planning department increased costs and nearly prevented the Gospel’s from building their dream home. Mark Siddall, the architect, undertook delicate negotiations to demonstrate the value offered to the local and regional economy, and the environment. This saw the removal of a requirement to provide expensive tabling, quoins and two costly chimneys. Ultimately all planning criteria were fulfilled without compromising the Gospel’s desire for a healthy, comfortable, well lit, low energy home.
These days best practice design can cut space heating bills by 90% without causing overheating. Because of this it was natural for Trevor and Judith to want a house that was designed to the Passivhaus Standard - the world’s leading quality assurance standard for low energy buildings.
AECB Water Standards informed the design and minimised demand for domestic hot water without compromising comfort. Owing to the remote location the house features a solar thermal system for domestic hot water and a reed bed system for the treatment of foul waste water.
Trevor and Judith now live in their new, comfortable, spacious family home. The walls are washed with natural daylight and the windows frame views of the rolling hills (allowing surveillance of the livestock). The lights are rarely used and the grandkids now come to stay.
To celebrate winning the 2015 UK Passivhaus Award for the small projects category architect Mark Siddall has prepared an in-depth 3-part documentary “How to Successfully Design and Build Your Own Home ...Without Breaking The Bank”.
Project Details (what makes this project special?)
This project is the first cavity wall Passivhaus building to be constructed in the North East. For this project to be realised a number of opportunities were found to exist. These included:
Utilising and enhancing regional skills and knowledge in the design and construction of advanced low energy (Passivhaus) buildings through training and direct experience.
Developing cost effective construction details that are suited to small to medium scale development.
Utilising tools and procedures that served to minimise risks associated with advanced standards of construction.
Developing a new supply chain for low energy (Passivhaus) buildings.
Demonstrating that traditional materials and advanced standards of construction may be combined sympathetically within the North Pennine Area of Outstanding Natural Beauty (AONB).
Benefits to the owner / occupier include but are not limited to:
Excellent standards of thermal comfort (complying with BS EN 7730 / ASHRAE 55)
Best practice standards of indoor air quality and acoustic quality
High standards of daylight (complying with BS 8206-2)
Significantly reduced running costs
Adoption of lifetime homes standards
Minimising carbon emissions and being responsive climate change
This project provides a model for both the design and construction of sustainable, low energy/ low carbon buildings throughout the UK. It also supports the rural economy by providing a home for a sustainable organic farm.
The Government has committed to reducing carbon emissions by 80% by 2050. UK housing is estimated to account for 27% of all carbon emissions. According to the Energy Savings Trust (CE301) there is uncertainty regarding the ability of cavity wall construction to achieve high standards of thermal performance.
As the first cavity wall Passivhaus building to be constructed in the North East this project robustly firm addresses these concerns. Refinements in the design, procurement and construction process have resulted in:
A compact building form that has been selected, whilst also being a feature of traditional homes in the AONB, this serves to help minimise heat loss.
Super-insulation – U-values half that required Building Regulations (U-values < 0.1 W/m2K for walls and 0.1 W/m2K for floor, < 0.08 W/m2K for roof, window U-values < 0.8 W/m2K)
That the use of triple glazing with super insulated frames helps to maximise thermal comfort by minimising down drafts and improving radiant temperature. (U-values of ≤0.8W/m2K, g-values better than >0.5). (Windows: EcoPassiv from Green Building Store.) High performance windows
A 90% reduction in thermal bridging as compared to the Accredited Construction Details and an 80% reduction compared to EST Enhanced Construction Details. (Avoiding approximately 435m2 of additional insulation and the associated time and labour costs.)
Advanced airtightness detailing that achieving a 97% reduction in air leakage compared to Building Regulations requirements.
Windtightness standards based upon Norwegian research and best practice. (In the UK the windtightness of the building fabric is unregulated. Poor windtightness can result in a significant increase in heat loss; in-situ measurements have found an increase in heat loss of up to 660%.)
Encapsulation of insulation within the cavity walls to minimise risk of closed loop thermal bypass. (In the UK closed loop convective thermal bypass is unregulated and can result in a significant increase in heat loss; research suggests a 140% to 300% increase.)
Best practice standards for duct cleanliness being adopted; based upon Finnish/REHVA guidance (no comparable UK guidance appears to exist).
Hygienic ventilation (0.3 - 0.4 air changes per hour). The use of a Passivhaus Certified balanced ventilation system with 90% efficient heat recovery. (MVHR: Paul Novus; 90% heat recovery fan power < 0.57 W/l/s, from Green Building Store.)
European good practice acoustic standards for the ventilation system < 25 dB(A) in living room/bedroom, < 32 dB(A) in non-habitable rooms (currently acoustic requirements from ventilation systems are unregulated in the UK)
AECB Water Efficiency Standards were adopted as the basis for minimising mains water and domestic hot water demand. Low flow fittings, a compact services plan, a microbore plumbing system was utilised so as to minimise the volume of dead legs (< 1.0 litres), and the storage cylinder was superinsulated (100mm compared to standard 50mm.
A solar thermal system further reduced primary energy demand and carbon emissions arising from DHW. With 56% of DHW provided by the solar thermal.
The windows proportions have been optimised to achieve high standards of natural daylight and solar gains. Smaller windows are located on the north, east and west elevations so as to minimise heat loss and larger windows to the south so as to optimise solar gains. Window proportions were refined to reflect those of a traditional building in the AONB.
An energy efficient lighting design has been installed. Provision for task/mood lighting has been optimised; thereby reducing the need for an excessive number of lights at ceiling level. Compact fluorescent lighting throughout.
Energy efficient appliances are to be installed as old goods are replaced (minimum A+++ rated).
Use of PassivHaus Planning Package (“PHPP”) software - for a detailed understanding of building performance at all stages.
As foul drainage connections were not available reed beds have been used for foul water treatment.
The new role of Air Tightness and Thermal Integrity Champion (ATTIC) was developed to help the contractor fulfil the ambitions of the project.
The house being subjected to a two year monitoring programme.
Passivhaus Planning Package Calculations: Space heating demand 14.1 kWh/m2.yr, Peak Load 10 W/m2, Primary Energy 74 kWh/m2.yr,
SAP Calculations: Primary Energy 31 kWh/m2.yr, Rating for Impact upon Environment A93, Energy Rating B91, Area 170m2, Space heating demand 836 kWh/yr, Domestic Hot Water Demand 2406 kWh/yr. 1.1 tonnes CO2 emissions/yr. Estimated (regulated) energy cost of dwelling over three years £1101.00.
Materials & Equipment
Walls: 300mm cavity.
Stone: Alston Natural Stone
Cavity Insulation: Mineral wool: Knauf DriTherm Cavity Slab 32 Ultimate
Blockwork: Durox Supablock, Hemelite Standard
Wall ties: Ancon Teplo
Windows: Eco-passiv windows from the Green Building Store
Entrance Doors: Eco-passiv doors from the Green Building Store
Roof insulation: Excel 'Warmcel 300'
Floor insulation: Knauf 'Polyfoam'
Airtightness products: Proclima
MVHR: Paul Novus
MVHR Ductwork: Lindab Ductwork and terminals
Solar Thermal panels: Viridian Solar 'Clearline'
Boiler: Broag Remeha 'Avanta'
The house is the first Passivhaus, and more particularly the first masonry build Passivhaus, in Northumberland.
In order to assist with the construction of the structure a number of design and specification refinements and innovations were employed including:
a. 300mm wide cavity walls (550mm overall) were formed using low conductivity walls ties made from basalt (BBA approved)
b. Innovative structural opening formers were used to help to reduce site error and simultaneously minimise as constructed thermal bridges.
c. Standard roof trusses were deemed to be unsuitable as they would result in unnecessary thermal bridging consequently a double Bobtail trusses were utilised.
d. Innovative airtightness systems for masonry and timber frame (roof) constructions were utilised in order to achieve exemplarily standards of performance.
In a Passivhaus building the domestic hot water demand can be greater than the space heating demand (this is due to the outstanding reduction in space heating demand), for this reason innovative water efficiency measures, based upon the AECB Water Efficiency Standards, were adopted wherever possible.
Further explanation of the innovations are discussed in more detail in Section 3
Involvement / Engagement
The design and brief development process for a Passivhaus project requires a close working relationship and a high level of collaboration between all relevant players.
Pre-construction consultation included the client, the planning authority and building control. Furthermore, as a part of a risk management process, consultation was made with builders and specialists that have worked on similar projects. This lessons-learned exercise was then combined with LEAP’s experience in delivering Passivhaus buildings. Additional technical input was sought from the NHBC.
Pre-tender interviews and visits to completed projects were used to help identify suitable contractors. The winning contractor demonstrated high standards of workmanship and client satisfaction though they had not worked on a project that had been subject to an air leakage test. This risk was managed via training and development.
All relevant construction details and the various roles and responsibilities required throughout the project were discussed with tendering parties. Subsequently trades training sessions were also developed for the wining contractor. These events also provided the opportunity for questions to be asked and for feedback regarding value, buildability and safety to be made and practical solutions to be found.
So as to reduce help risks even further an innovative new project role, the "Air Tightness and Thermal Integrity Champion (ATTIC)," was introduced. This duty was fulfilled by the site foreman. The ATTIC had the role of providing on site, day-to-day, quality assurance supervision so that convective thermal bypass mechanisms could be avoided. This role proved crucial to the projects successful airtightness result. Ian from JD performed an excellent job and has proven to be a very diligent member of Joe’s team and has overseen the site to date.
Mark Siddall "In order to gain certainty that we could satisfy the Passivhaus standard we used the Passivhaus Planning Package (PHPP) to create an energy model. This was done at an early stage in the design process, before applying for planning permission and enabled us to determine the appropriate area of glazing and other aspects that influence the energy performance. Ultimately our discussions with the Local Authority helped us reach an agreeable solution whereby the character of the AONB and the ambitions of the project could be preserved."
Mark Siddall “In order to achieve the Passivhaus Standard every detail becomes important. Providing adequate information, and training, for the building contractor is therefore vital. ”
Mark Siddall “The clients are the stars of the project, without their ambition the house would not be a Passivhaus.”
Mark Siddall “Compared to the cost of construction it is surprising how cost effective well considered design time can be. We have calculated that the construction details are so energy efficient that they achieved an 90% reduction in heat loss compared to the standard details used to satisfy the Building Regulations.
“This not only avoided the need for a further 435 square meters of insulation (approx. £3000.00) but also the associated time and labour costs for installation on site. It is this kind of attention to design reduces both the construction costs and the energy bills.”
Mark Siddall “The blower door result is a real demonstration of the effort and hard work of Joe's team. I must confess that they have impressed me throughout the project with their attention to detail."
Joe Dixon "Feedback from Mark suggested that he was confident that we could achieve the airtightness target, but I honestly didn't expect for us to do so well. I mean, we'd never done a pressure test before and to get this kind of result is just fantastic. Without all the drawings, training and support from Mark there is no way we would have achieved what we have. These results are not just a proof of the skill of the lads on site but also to Mark's excellent design, commitment and knowledge of the whole subject of low energy buildings."
Joe Dixon of J.D. Joinery and Building says "Whilst the demanding standards of workmanship did slow progress a little at first it was the use of natural stone, required by the planning authority, that took longer than expected. Now that we have built a Passivhaus under the watchful eye of Mark, the architect, our familiarity with the demands of the Passivhaus Standard means that next time we will be able to do so more quickly and at lower cost."
Trevor Gospel "The construction of our new home has been a real adventure; challenging at times but, all in all, well worth the wait. Both Mark and Joe have met and exceeded our expectations. We had a limited budget and stuck to it. I don't think that we could have been in safer hands."
Judith Gospel “In our old house, 2011 I think, we measured the temperature of the living room and the fridge. It was warmer in the fridge! More than the savings in the energy bills and the reduced environmental impact, we are enjoying the comfort of our new home."
About the Architect
Mark Siddall (www.marksiddall.co.uk) is a practicing architect and one of the UK’s leading experts in the Passivhaus Standard.
He was project architect, and Passivhaus Designer, for 25 award winning Passivhaus Certified dwellings at the Racecourse Estate, Houghton-le-Spring. He was also project architect on a number of award winning Retrofit for the Future projects that targeted an 80% reduction in carbon emissions. He has also completed 3 other homes that have been built to the Passivhaus Standard.
Mark is a technical advisor to the PassivHaus Trust and trains architects and engineers how to become CarbonLite Certified Passivhaus Designers . He is also an author of many articles and papers about building performance and Passivhaus design. To access these articles for free visit www.PassivhausSecrets.co.uk