The recently completed social housing project at Akerman Road for Lambeth Council, includes three new-build Passivhaus certified terrace houses, and six highly energy efficient retrofit flats within a locally listed building. The construction solutions and details were carried out by the 15-40 Architectural Collective.

Ensuring vapour open construction was a priority. Highly insulated houses must consider moisture management, moisture damage being the greatest risk factor to the building fabric. The new-build terraces were constructed using the PH15 Timber Frame System which uniquely offers a natural Sinsulations solution to Passivhaus projects, ensuring the building can ‘breathe’ and that moisture can escape externally through the structure.

With the PH15 Timber Frame System, products are used that are known to enable water vapour to escape externally – this includes Lime Green’s Warmshell render system applied directly to external wood fibre insulating boards. Lime Green renders are highly breathable and elastic, with low water absorption, which means they will provide a very durable finish and importantly have far less embodied energy than other render systems.

Lime Green Products offer approved installers to ensure their lime based products are applied correctly on site, important given that this is a natural product. Lime Green also provide excellent technical support and training. A wide variety of colours and finishes are possible.

The PH15 System is a part offsite solution developed specifically for Passivhaus standard levels of energy efficiency. The PH15 frame elements are all pre-cut offsite and individually coded – like a meccano set, rather than fully panellised. This is both an economic solution and avoids the need for heavy lifting equipment. The system can be delivered where there are limited or difficult access conditions. The PH15 shell relies on typical UK carpentry skills only, supported by onsite training and a technical help line.

Lime Green Products also manufacture a range of natural lime renders and insulation solutions for retrofit projects where moisture management is particularly critical. Their Warmshell internal insulation system addresses the common problems of damp and condensation, whilst also addressing heat loss and contributing to a healthier indoor environment.

PASSIVHAUS STATISTICS: TFA 371m², Form Factor 1.8, with U-values of roof 0.108 W/m2K, walls 0.105 W/m2K, floor 0.106 W/m2K.  Heating load 7.9W/m2. Predicted Heating demand 9.1 kWh/m²a. Airtightness test results: 0.34, 0.39 and 0.4 ach@50Pa

For further information on the Warmshell insulation and render systems please visit

www.lime-green.co.uk/warmshell

To learn more about the PH15 Timber Frame System visit www.phhomes.co.uk.

Photography by – Paul Samuel White Photographs Akerman Road