Diasen Diathonite Thermactive: Products Finalist – Exemplar Sustainable Buildings Awards

A finalist in the 2025 Exemplar Sustainable Buildings Awards product category, Diasen Diathonite Thermactive.037 is a vapour permeable lime and cork-based insulating plaster that delivers thermal performance with low embodied carbon. Designed for use on internal walls and ceilings, it offers a multifunctional solution—combining thermal insulation, moisture management, and levelling in a single product. With excellent vapour permeability (μ = 3), thermal conductivity of just 0.037 W/mK, and high porosity, Thermactive regulates humidity, stabilises indoor temperatures, and enhances comfort year-round.

What makes Thermactive.037 stand out is its low-carbon formulation—made from up to 50% natural cork (85% of which is recycled), lime, and diatomaceous earth. Compared to typical thermal plasters, it has five times lower embodied carbon (0.895 kgCO₂e/kg), and comes with a verified EPD, BBA certification, and inclusion in the WUFI material database. In use, it achieves impressive operational results: at a Mews House retrofit by Prewett Bizley Architects, a 50 mm application reduced the U-value from 2.1 to 0.54 W/m²K, contributing to an 80% drop in energy use intensity.

Suitable for solid masonry, timber frame, and retrofit applications—including heritage and social housing—Thermactive.037 is helping push the insulation market toward more natural, vapour permeable, and circular alternatives. Its A1 fire classification, rapid drying time, and ability to address complex junctions with ease make it a practical and high-performing solution for sustainable buildings.