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Treadgold House

BowTieSprong Concept Design
Bow Tie Construction, Sciana, GSA
Project Description

As the winners of Energiesprong UK’s 2020 design competition, Bow Tie led a consortium working with GSA Studios and Sciana to concept design the UK’s first net zero carbon multi-unit building retrofit. Bow Tie then successfully applied for Innovate UK funding to follow on the research and development process, engaging with residents using the permaculture process. The grant funded the successfully patent of intellectual property detailing how external insulation panels would be designed and fit to the building with the highest possible precision.

The retrofit design would self-generate enough electricity (annually) to power its hot water and heating systems for all individual units and communal areas. This would be achieved by a large solar array, batteries, air source heat pumps and heat recovery ventilation units. The installation would eliminate carbon dioxide and nitrous oxide emissions (NOX) and reduce the heat demand of the building by a factor of 47.

The project was balloted to residents and received near-unanimous backing. These residents know their views are central to the co-design process. From the commencement of the R&D process Bow Tie Construction engaged weekly with the Lancaster West Neighbourhood Team, Building Control and residents through workshops, presentations and Q&A sessions. LWNT stated they wanted residents to have the final say in approving the retrofit and its ingredients. Resident engagement and resident experience have been at the core of the offering and was inspired by Permaculture principles: Earth care, people care and fair shares. The participants directly contributed to making their estate a nicer place to live for all, now and in the future. The results of the resident engagement process can be viewed here:

Benefits of The BowTieSprong retrofit:
  • Elimination of fuel poverty for residents – apartments will never fall below 19degrees even without active heating.
  • Increased amenity space – renovated balconies to double the size of existing.
  • Lower cost of energy for residents.
  • Gas removed to eliminate standing charge, safety issues and maintenance costs.
  • Zero Carbon and NOX emissions going forward.
  • Resident co-design of the retrofit with input on landscaping, playspaces and volunteer activities such as germinating seeds to seedlings which grow to maturity on resident balconies.

Innovate UK is the United Kingdom’s innovation agency, a non-departmental public-body, commented:

“Your vision aligns beautifully with where we think the retrofit sector could go and you are innovating around all the key barriers to scaling up and wider adoption of retrofit.”

The resident experience:

  • Constant temperature in living area of 21degrees.
  • ‘45-minutes’ of hot water a day, a typical electrical plug load, all within a ‘comfort plan’ or service charge.
  • An attractive building that looks/feels good.
  • Ability to stay in their home during works.

‘BowTieSprong’ is a revolutionary approach to wholesale retrofit of apartment buildings:

  • It involves encapsulating the building with a new insulated airtight wall and a new warm roof with a maximally sized solar array.
  • The new roof space forms a service loft providing access to the solar array/batteries/air source heat pumps (ASHP) and MVHR air handling units.
  • Hot water is heated by ASHP which eliminates gas connection and standing charge.
  • Conversely, indoor temperature will rarely be above 26°, guaranteed by the fact the entire design is informed by Passivhaus retrofit principles but exceeds these performance requirements (details in Q7).
  • The replacement of gas boilers with heating systems powered by solar array prevents emission of 417 tonnes of CO2 annually and 1.2 Tonnes of NOx.
  • 1670 MWh of fossil fuel energy will no longer be combusted by Treadgold House annually.
  • That is the equivalent emission released by burning 177,884 litres of petrol (EPA 2020) or 208tons of coal (EPA 2020).
  • To reverse one year’s Treadgold current emission would require 6,895 tree seedlings grown for 10 years (EPA 2020).
Modern Methods of Construction

The key waste reduction factor would be the use of modern methods of construction (MMC) to deliver retrofits. External wall-panels will be supplied to site with windows installed. Roof cassettes would be manufactured off-site.  

The external wall-panel system will achieve brick, stone or render finish. All components are made to measure manufactured specifically for each installation. There is zero-waste as there are no off-cuts, cutting on-site or wet-trades. Assembly would take place at a flying-factory within 5-miles of Treadgold House. It is our aspiration that Lancaster West Estate residents are given the opportunity to work on their retrofit and up-skill in the process. Assembled panels are transported by electric vehicle and hoisted into place by electric crane. This eliminates the emissions of thousands of litres of diesel which would have been used through traditional methods. Swift movement of panels from assembly to construction site would be coordinated “Just-In-Time”.


Bow Tie Construction received an Innovate UK grant for R&D leading to patent application. This includes 3D-scan driven design and installation systems reducing the cost and install duration. This system bridges the gap between existing construction and 3D models and designs out survey inaccuracies. The system includes innovation that improves the way survey equipment makes decisions with data to automate labour-intensive tasks. It is applicable across the entire construction industry as it improves accuracy and programmability whenever large, costly off-site manufactured components are being designed/manufactured/installed. Bow Tie intend to license this process to software companies and manufacturers making this technology available which will drive down cost of MMC retrofit. They welcome enquiries from interested parties.

“My projects with Bow Tie are the only ones where I’ve left the contractor to follow my airtightness details and the projects have passed the 1st airtightness test.”

– Justin Bere

“Rafael’s product knowledge and technical skills helped us solve many tricky problems and ultimately produce our dream home. Thanks Rafael!”

– Zahid H

“I’ve been very pleased with how Bow Tie have got on with the work.”

– Justin Bere

“I have enormous respect for Bow Tie as a contractor: It’s a real pleasure not having constant battles and headaches from a builder trying to do the bare minimum.”

– Justin Bere

“Rafael was not only a competent builder but was fully involved in a complete refurbishment job from conception to realisation.”

– Carole R

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