Sto render system specified for new Passivhaus development

Sto's StoRend Flex render system was specified for use on a high-profile development of luxurious and sustainable homes built in Norfolk.

Located five miles from Norwich city centre, the six new Octagon Park homes are designed to meet the requirements of the Passivhaus Plus standard, while delivering outstanding quality and a high level of sustainability.

“In order to minimise energy consumption, the Passivhaus Plus standard sets out very specific criteria for construction, insulation and ventilation systems,” explains Sto’s head of sales, Ashley Wainwright. “This meant that the materials specified had to satisfy extremely demanding performance standards, and the StoRend Flex render system was certainly able to achieve this.”

The Octagon Park development was created by JR Cozens Wiley Ltd, and the properties feature a timber-frame construction, which had a direct bearing on the specification of the StoRend Flex system. “An alternative render system was originally considered for the project,” adds Ashley. “However, this would have required the inclusion of many vertical and horizontal movement joints at every door and window aperture. Fortunately, these weren’t necessary with the Sto system, so it was ideal for this purpose as it helped simplify both the design and construction processes while still delivering the performance and high level of finish required.”

The StoRend Flex synthetic render system provides a highly flexible, rugged and crack-resistant exterior render finish which was in-keeping with the high-quality nature of the Octagon Park development. The render itself was applied to Sto’s own StoVentec render carrier boards, which were fixed to the timber frames of the buildings. Being made from recycled glass granulate, the StoVentec render carrier boards are dimensionally stable, so thermal movement is minimized and the need for movement joints can be reduced, and often eliminated completely.

Widely regarded as an industry benchmark solution, StoVentec board has been specifically developed for use with Sto render products. “The boards can be installed quickly and easily and can be cut without the need for power tools,” comments Sebastian Slomkowski of Passivhaus-approved S.I.R.S. Ltd of Norwich, who installed the Sto materials. “They can also weigh up to 50% less than other render boards which makes them easy to handle and install.”

The addition of StoArmat Classic Plus, a cement-free, acrylic resin-based reinforcing coat – which is up to 15 times more flexible than traditional cement-based reinforcing coats when embedded with Sto Glass Fibre strengthening mesh - provided exceptional levels of crack resistance. The system was then finished with a stippled StoSilco render and StoColor Dryonic façade paint that promotes fast and efficient drainage of water, allowing the surface to dry rapidly and greatly inhibiting the appearance of algae, fungus and unsightly marks.