Cullerne Nature House Retrofit

The Cullerne Nature House Retrofit is a pilot project exploring how a traditional stone house in Findhorn, Moray can be adapted into a low-carbon, energy-efficient home while retaining its architectural and cultural integrity. The project develops a regenerative retrofit strategy that combines heritage conservation with contemporary environmental performance.

Rather than relying on conventional deep retrofit methods that risk erasing historic character, the approach investigates an external “Nature House” enclosure inspired by the work of Swedish architect Bengt Warne, whose Naturhus concept introduced greenhouse-based thermal buffering as an alternative environmental strategy.

Retrofit Strategy

The existing Cullerne House, constructed from solid stone with a traditional slate roof and timber window assemblies, presents typical challenges associated with historic rural buildings: high heat loss, limited airtightness, and reliance on carbon-intensive heating systems.

Instead of heavily altering the original fabric, the design introduces a secondary glass enclosure wrapped around the south, east, and west elevations. This creates a temperate intermediary zone between interior and exterior, transforming the building’s environmental performance without compromising its heritage structure.

The intervention operates as a reversible layer of climate protection, allowing the original building to remain largely intact while significantly improving energy efficiency.

Nature House System

The glass enclosure performs as an environmental buffer, operating through three integrated mechanisms:

• Thermal buffering: Solar gain is captured within the glazed envelope, moderating temperature fluctuations and reducing reliance on active heating systems

• Wind protection: The external layer reduces wind pressure on the historic masonry, improving airtightness and limiting heat loss through infiltration

• Window protection: Existing traditional windows are shielded from direct exposure, reducing thermal bridging while preserving original joinery

This system allows the historic house to function within a stabilised microclimate, reducing operational energy demand while maintaining the visual and material identity of the original building.

Environmental Approach

The project responds directly to the challenge of decarbonising the UK’s existing building stock, where the majority of 2050’s buildings are already in use today. Historic homes such as Cullerne House are particularly difficult to retrofit without compromising their architectural value.

The Nature House strategy offers a low-impact alternative, prioritising envelope-level performance improvements over invasive internal reconstruction. This significantly reduces both operational and embodied carbon while extending the life of the existing structure.

Heritage and Performance

A key objective of the project is to demonstrate that heritage conservation and climate adaptation are not opposing forces. The retrofit maintains the legibility of the original stone house while introducing a contemporary environmental layer that can be read as a distinct architectural addition.

The result is a building that operates across two systems: a historic core preserved for its material and cultural value, and a modern climatic envelope that enables low-energy performance.

Location: Findhorn, Moray, Scotland, United Kingdom

Property type: Historic rural stone house (traditional Scottish domestic building) undergoing regenerative low-carbon retrofit

Scope: The project involves the sensitive retrofit of an existing historic stone house in Findhorn, Moray, through the introduction of an external “Nature House” glass enclosure system. The scope includes the design and implementation of a glazed environmental buffer wrapping the south, east, and west elevations of the building to improve thermal performance while preserving the original fabric. Works focus on reducing operational energy demand through passive climate control strategies - thermal buffering, wind protection, and window heat-loss reduction - without significant alteration to the heritage structure. The intervention aims to lower both operational and embodied carbon, enhance airtightness, and extend the usable life of the existing building while maintaining its architectural and cultural integrity within a regenerative retrofit framework.

Key Features:

• Regenerative retrofit of a historic stone house in Findhorn, Moray

• Introduction of a “Nature House” glass enclosure inspired by Bengt Warne

• External glazed buffer wrapping south, east, and west elevations

• Passive environmental control through thermal buffering and solar gain capture

• Wind shielding to reduce heat loss and improve building airtightness

• Protection of existing historic windows without removal or replacement

• Retention of original masonry structure and slate roof with minimal intervention

• Reversible, low-impact retrofit strategy preserving heritage fabric

• Significant reduction in operational energy demand through passive systems

• Improved internal comfort through stabilised microclimate envelope

• Reduced embodied carbon compared to conventional deep retrofit approaches