Case Study:

Energy Efficiency Improvements to a traditional house in Scotland

Fernandes Binns Architects – Architects in Edinburgh

Summary

Traditional stone houses make up a large proportion of Scotland’s housing stock, but many are cold, expensive to heat, and difficult to upgrade safely.

This case study looks at the refurbishment of an 18th-century farmhouse in East Lothian, where we combined careful fabric repair, targeted insulation upgrades and air source heat pumps to transform a cold, inefficient building into a warm, comfortable home—without causing condensation or mould problems.

The project demonstrates why thermal upgrades to traditional buildings need careful design, and how early architectural input can significantly reduce risk and long-term cost.

Why Retrofit of Traditional Homes Is Challenging

Around a third of UK homes were built before the Second World War, often with solid stone walls and little or no insulation. While upgrading these buildings can dramatically reduce running costs and improve comfort, poorly designed retrofit work can lead to serious problems such as damp, mould and timber decay.

Much of the recent negative press around insulation failures comes down to one issue: a lack of understanding of building physics.

Every home produces moisture through everyday activities. In older, uninsulated houses this moisture often dissipates harmlessly. When insulation is added incorrectly, moisture can become trapped, leading to condensation within walls and roofs.

This is why retrofit design matters.

The Existing House

The property was a large detached 18th-century farmhouse with solid stone walls, single-glazed sash windows and a slate roof. Years of roof leaks had left internal finishes damp, and the house relied on a mixture of electric heaters, gas and wood-burning fires.

As the house was off the mains gas network, it was expensive to run and uncomfortable to live in—often feeling colder inside than out during spring and autumn!

A full refurbishment was required, creating an opportunity to upgrade the thermal performance at the same time as essential repairs.

Our Retrofit Strategy: Fabric First

Whenever we work on existing buildings, we prioritise a fabric-first approach: improving insulation, airtightness and ventilation before specifying new heating systems.

Because much of the building fabric had to be stripped out for repair anyway, we were able to integrate insulation upgrades with minimal additional disruption.

Key principles included:

• Improving thermal performance wherever practical
• Managing moisture carefully to avoid condensation
• Retaining the character of the original building

Energy Assessment and Heating Strategy

Given the size of the house and its rural location, we worked with building services engineers to carry out an early-stage energy assessment.

This allowed us to model heat loss and compare options including LPG, ground source and air source heat pumps. Air source heat pumps were selected, supported by the improved thermal envelope and with future photovoltaic panels in mind.

Early modelling was critical in ensuring the system would be efficient, reliable and cost-effective over the long term.

Key Thermal Upgrades (Overview Only)

Roof

The roof was stripped and re-slated, allowing us to reuse existing insulation alongside additional layers. Careful detailing and ventilation were incorporated to prevent condensation, including a modern vapour-permeable membrane.

Windows

The existing timber sash windows were retained and upgraded with slim-profile double glazing and draught sealing, improving comfort while preserving the building’s appearance. Today, we would typically consider vacuum glazing for similar projects.

Floors

Timber floors were lifted to repair joists and install insulation from above. Ventilation to the solum below was improved to prevent moisture build-up—a critical but often overlooked detail.

External Walls

Internal wall insulation was carefully designed using thermal modelling to manage interstitial condensation risk. A ventilated cavity and airtightness measures were incorporated to balance performance with moisture control. Although breathable insulation boards such as wood fibre can be a great option for retrofit, in this case we opted for a conventional PIR board insulation, leaving a narrow cavity between the stone and the insulation which was ventilated to the solum or roof space.

Heating and Comfort

Three air source heat pumps were installed, feeding a large hot water cylinder serving both space and water heating. Underfloor heating was used where possible, with larger radiators elsewhere.

Wood-burning stoves were added to provide rapid-response supplementary heating and enhance day-to-day comfort.

Funding and VAT

When making energy efficiency improvements, it is worth investigating the VAT position and checking for any funding available. There is some guidance on VAT on the UK government website, but it may be sensible to advice from an accountant for bigger projects. Energy-saving materials and heating equipment (VAT Notice 708/6) – GOV.UK

For funding, it can be worth checking guidance on Home Energy Scotland’s website Home Energy Scotland

Lessons for Homeowners

This project highlights several key lessons for owners of traditional properties:

• Insulation upgrades must be designed, not improvised
• Ventilation is as important as insulation
• Early professional advice reduces risk and long-term cost
• Heat pumps work best when combined with fabric improvements

Summary

If you are considering refurbishing or upgrading a traditional property in or around Edinburgh, early architectural input can make the difference between a successful retrofit and costly problems later on.

Fernandes Binns Architects specialise in residential refurbishment, conservation and energy upgrades for traditional buildings. If you are planning a project, we would be happy to discuss how we can help. Please get in touch!