H+H’s Thin-Joint System is at the heart of Derwenthorpe, a low-carbon community, the first phase of which scooped the Best Affordable Housing Development Award in the 2017 Inside Housing Awards. The latest win follows three prestigious RIBA awards earlier this year.
Joseph Rowntree Foundation Trust’s 540 home mixed-tenure community is located on the outskirts of the village of Osbaldwick near York. Delivering eco-friendly homes was a key priority for the project so finding an environmentally friendly solution was essential.
The architect behind the project, Studio Partington, had been working on the development for 10 years and had already experienced the benefits of using H+H’s Thin-Joint System in previous projects. Director Adam Cornish said: “We were confident the Thin-Joint System could achieve the performance required, U-values, air tightness and construction quality”.
Two prototype houses were initially constructed to test different Modern Methods of Construction (MMC); one of which used H+H Standard Grade (3.5N) Jumbo Plus Bloks (630mm x 250mm in 100mm thickness) as part of H+H’s Thin-Joint System and achieved Code for Sustainable Homes Level 4.
Analysis conducted by Leeds Metropolitan University’s Centre for the Built Environment found that the property had a dwelling emission rate of 12.59kgCO2/m2/yr and an airtightness of around 2m3h.m2@50Pa. Post-occupancy studies showed a significant narrowing of the performance gap between predicted and actual energy.
Housebuilder David Wilson Homes then went on to adopt the tried and tested H+H Thin-Joint System for the majority of the development after they were satisfied the method proved it could achieve and maintain the level of performance and build quality for over 500 homes. Although the housebuilder was new to thin-bed masonry construction, Adam explained:
“H+H provided David Wilson Homes and the subcontractors with on-site support and training. They have continued to be supportive of the project, providing valuable technical information in developing the appropriate detailing to achieve the performance required for a project where standards were particularly high.”
H+H, the UK’s largest manufacturer of aircrete, provides its Thin-Joint System as a combination of aircrete blocks with Celfix Mortar, producing masonry with a 2mm joint rather than the standard 10mm, speeding up the build process and reducing thermal bridging.
The system combines 100mm aircrete blocks with cement-based Celfix Mortar rather than traditional sand: cement mortar. As well as offering superior thermal performance over traditional methods of masonry, the thin-joint bed allowed housebuilder David Wilson Homes to construct the whole inner leaf first to provide an immediate watertight structure before the windows and doors are fitted.
Adam said: “This allowed the insulation to be installed and checked before the outer brick façade is added, ensuring a better constructed and well insulated air-tight building.”
The demand for ever-increasing energy efficiency is particularly strong in the public sector, where the need to cut carbon emissions is combined with a focus on minimising energy costs for tenants.
Approaching these twin objectives with a fabric-first solution requires builders to minimise the amount of heat lost through construction details; the minimal joint thickness achieved with H+H’s Thin-Joint System allows for maximum airtightness and maximum thermal performance.
H+H is keen to support contractors looking to make the switch to using aircrete. Adam said: “H+H were very supportive in resolving queries during the development stage of the project and addressing any on-site concerns and training needs we had.”