EnerPHit retrofit transforms heritage high-rises to 21st Century comfort

An EnerPHit informed retrofit transforms Leith’s Landmarks, Cables Wynd House & Linksview House into sustainable homes fit for the future.

Two of Scotland’s most recognisable post-war housing towers are set to undergo an ambitious EnerPHit-informed retrofit, balancing energy performance with the preservation of architectural heritage.

Cables Wynd House & Linksview House I Image credit Collective Architecture

Cables Wynd House and Linksview House are Category A listed brutalist buildings in Leith, Edinburgh, home to 310 households. Built in the 1960s and celebrated for their striking form and pioneering use of materials, the social housing towers now require significant upgrade to meet modern standards for comfort, energy efficiency, and health. The improvements are part of a project to modernise 44 multi-storey blocks across the city. Architects on the project, PHT member Collective Architecture, have delivered Scotland's largest residential certified Passivhaus, Dundashill.

Key stats

Number of homes: 310
Contract Value: £69 million (incl. landscaping & ground floor community services)
Stage: Awaiting planning approval
Expected build start date: 2026
Certification: N/A. EnerPHit-informed

Cables Wynd House & Linksview House I Image credit © Collective Architecture

Community buy in

The retrofit is being delivered with residents in place or temporarily relocated within the towers. Engagement began early using Collective Architecture’s Home Standard Tool, allowing residents to assess their homes against 14 criteria. Insights from this process informed:

Prioritisation of fabric and services upgrades
Design of new community hubs on the ground floor
Colour and detailing choices for façades

EnerPHit-informed retrofit

Cables Wynd House & Linksview House _Consultation I Image credit © Collective Architecture The City of Edinburgh Council aims to meet Scotland’s Energy Efficiency Standard for Social Housing post-2020 (EESSH2) while tackling fuel poverty and reducing operational carbon. The chosen approach is guided by the Passivhaus EnerPHit methodology, enabling rigorous, iterative modelling and detailed performance testing.

Predicted outcomes:

88% Space heating demand reduction
80% Total energy use reduction
Fabric-first approach with airtightness and thermal bridging performance targeting EnerPHit benchmarks

Cables Wynd House & Linksview House I Image credit © Collective Architecture

A bespoke Energy and Carbon Cost Tool has been used to balance predicted performance outcomes with capital and operational costs, installation complexity, and construction phasing. The £69m project costs include landscaping & provision of new ground floor community services.

We are investing around £69 million in essential repairs and improvements to Cables Wynd House and Linksview House in Leith. We are planning major refurbishments which will help to make them safer, warmer and more comfortable places to live.

City of Edinburgh Council

Construction

The reinforced concrete frame & precast aggregate concrete cladding were retained and repaired. Category A listing (equivalent to Grade 1 listing) limit the extent to which the building can be insulated. The need to respect and celebrate the Brutalist qualities of the towers’ architecture was at odds with the need to address the extensive thermal bridging and absence of insulation.

Due to heritage restrictions, most fabric measures are internal. However, through careful definition of the heritage significance, opportunities to introduce external wall insulation (EWI) to balcony recesses were identified, and internal wall insulation (IWI) deployed where there are concrete cladding panels. Timber frame infill walling is replaced with metframe and EWI.

A unifying colour strategy for externally insulated elements has been developed with Professor Fiona McLachlan of the University of Edinburgh and refined through resident workshops.

Warm roofs are proposed and ground perimeter thermal bridges addressed where existing floors cannot be insulated, but the majority of accommodation is located above ground level. Treating thermal bridges from the structure is a key focus of the design stage with an iterative approach to testing different insulation materials to determine optimum impact and benefit.

Heritage constraints to super insulate the fabric have been countered by driving the airtightness down to 1.0m3/hr.m² @50Pa combined with MVHR ventilation to reduce heat loss and optimise residents indoor air quality and comfort.

U-values

Roof: LVH: 0.174 W/m²K I CWH: 0.114W/m²K

New reinforced bitumen warm roof buildup

Wall: LVH: 0.267 W/m²K I CWH: 0.270 W/m²K

IWI – New stone mineral wool insulation on masonry/ concrete wall, metal stud frame with stone mineral wool insulation between, Monodirectional vapour control and airtightness membrane, plasterboard lining.

EWI – New rendered EWI system on weather resistant sheathing board on metframe stud wall with stone mineral wool between studs, Monodirectional vapour control and airtightness membrane, plasterboard lining.

Floor: LVH: 0.675 W/m²K I CWH: 1.304 W/m²K

Existing floors untreated but perimeter thermal bridges addressed. New floors insulated below slab.

Windows: LVH & CWH: 0.85 W/m²K

Composite aluminium faced timber frame triple glazed windows. Triple glazed curtain walling.

Doors: LVH & CWH: 1.5 W/m²K

Steel or aluminium frame double glazed secure entrance doors

Architect’s view

One of the core objectives for the project has been to meet the EESSH2 requirement for dwellings to be EPC band B or as near as possible. Working with the client we were able to convince them of the benefits of using the EnerPHit standard to guide a fabric first approach that would enable significant energy demand reduction. Early testing suggested that we were close to meeting the standard, however, the client did not have an appetite for certification. Additionally, we were aware that meeting the PER requirements would be challenging.

The focus of the project was always on resident comfort and affordability of heat with a client-led drive to move away from the gas heating systems present in each building, shifting to electric heating systems that are simpler to install and maintain. Restrictions on using solar PV due to the heritage listing and the decision to utilize High Heat Retention (HHR) radiators PCM batteries for hot water and economy 7 / 10 controls ultimately meant that compliance with the EnerPHit PER criteria were not attainable.

Instead, the focus of the project has been on using the EnerPHit fabric first approach to reduce the EUI to levels that mean that the energy costs are affordable, especially after the switch from gas to electric heating.

James York, Principal Energy Consultant, Collective Architecture

Predicted building performance

	Linksview House	Cable Wynd House
Space Heating Demand (≤ 25 kWh/m².a)	18.66	17.36
Peak Energy Load (≤ 10 W/m²	9.73	9.51
Primary Energy Demand: (≤ 120 kWh/m².yr)	89.37	76.56
Primary Energy Renewable (PER) Demand (≤ 60 kWh/m².a*)	89.37	76.56

*+/-15 kWh/m².a allowance if offset by energy generation. See Passivhaus criteria.

Building services

Planned upgrades to move Linksview House from gas central heating and Cables Wynd House from a gas fired communal heating system include:

Mechanical ventilation with heat recovery (MVHR) to improve air quality and reduce heat loss
High Heat Retention (HHR) radiators sized for reduced demand
Phase Change Material Hot Water Batteries appropriate for high-rise operation

Key team

Client: The City of Edinburgh Council
Funders: Scottish Government
Project Manager & QS: Atkins Realis
Architect: Collective Architecture
Energy and Heritage Specialists: Collective Energy and Collective Conservation
Fire Engineer: A10
Structural engineer: Narros
M&E consultant: Blackwood Partnership
Landscape Architecture: Urban Pioneers

Lessons learned

Deep retrofit using an EnerPHit informed approach is achievable for listed high-rise buildings, even under strict heritage constraints such as Category A listing (equivalent to Grade 1 listing). The EnerPHit framework enables reliable performance. Successful outcomes rely on carefully balancing heritage conservation with operational carbon reduction.

Detailed definition of heritage significance enabled selective application of EWI in balcony recesses and IWI on concrete cladding panels, while warm roofs and perimeter insulation helped address thermal bridges.
Thermal bridge treatment required an iterative approach, testing different insulation materials to maximise impact and performance.
Where fabric upgrades were limited, airtightness was driven down to 1.0 m³/hr·m² @50Pa, supported by MVHR ventilation to improve efficiency, indoor air quality, and comfort.
Ease of maintenance for MVHR units was a key consideration; enclosing gallery walkways created accessible communal plant space while also enhancing fabric efficiency and streamlining form.
Embedding resident engagement at every stage of retrofit was critical to aligning design decisions with user needs and building long-term support.