Case Study: Forge House

Case Studies

Lower heating cost and peace of mind for owners of this Sussex Heritage Trust prize winning house.

When the owners of Forge House decided to improve the thermal performance of their new home as part of extensive works to the property with CDMS architects, NBT Pavadry was chosen to give a risk-free upgrade to the walls of the traditionally built solid masonry walls. The system was expertly installed by local contractors Minton Young, with the project going on to win an award from the Sussex Heritage Trust.

What is Pavadry?

Pavadry is an Internal Wall Insulation (IWI) system comprising of a composite woodfibre and hardboard insulation to which plasterboard or an alternative finish is fixed. The system is designed to radically improve the thermal resistance of solid masonry buildings while actively controlling moisture, preventing condensation while preserving the structural integrity of the building.


IWI is recognised as one of the highest risk areas for retrofitting as changing the thermal dynamics of the building can cause higher moisture levels within the walls. However, Pavadry eliminates the danger of trapped moisture in a simple way – by using the natural properties of woodfibre supplemented by an integral mineral layer.

An Adaptable System

The system is highly adaptable both during and after installation, with a wide variety of options for finish linings and installation of services. Internal fitting is simplified due to the load bearing capacity of the internal surface. Contrary to other systems, the insulation can sustain significant weight. This means the problems fixing to it in the future are avoided. There is also no risk of puncturing a vapour barrier (which is integral to the suitability of other systems).

Guidance and Analysis

Specification of Pavadry is always carefully guided by us. We undertake condensation risk analysis with sophisticated software that accounts for fluctuating external conditions, as well as internal conditions. Standard industry practice is to ignore the impact of rain absorption, and with it the most significant moisture source acting on the wall.

Better Buildings

Natural Building Technologies is dedicated to delivering better buildings with simple, robust and effective thermal insulation. NBT systems utilise the inherent advantages of sustainable natural materials to deliver reductions in energy cost alongside fabric durability and occupant health; all with materials of ultra-low environmental impact. NBT also provide design, specification and construction support which contributes to a joined up process throughout the refurbishment, and closes the gap between design aspiration and reality.


Our expertise in traditional buildings has been developed in partnership with leading academic and not-for-profit organisations in the retrofit sector, including University College London (Pavadry was developed in conjunction with UCL), SPAB, the STBA (authors of the DECC funded Responsible Retrofit Report), and the Good Homes Alliance. Bringing this expertise to bear on projects such as Forge House ensures that the conservation of energy enhances, rather than compromises, conservation of traditional buildings.

Products used in this project…