Cracking the Code

H+H’s Thin Joint system has been used in a fabric-first approach to the design and construction of a low energy apartment block on a constrained site in Brighton.

The planners insisted the four-apartment scheme had to comply with Level 4 for the Code for Sustainable Homes. This demanded a 25% reduction in CO2 emissions when compared to Building Regulations (2010). “The scheme had to achieve Code Level 4, so not only did we have to achieve a very good thermal performance but good sound resistance and airtightness too,” says Michael Alderton, director of contractor Canning Ericsson. “The H+H Thin Joint aircrete construction system appeared to be the best solution to achieve this,” he adds.

This was the first time the contractor had used the H+H This Joint system for an external wall construction, although Canning Ericsson had used H+H’s Jumbo Bloks to build the internal partitions on some of their previous developments.

The apartment’s external walls are constructed using Celfix Mortar applied to Standard Grade 610 mm long x 270 mm high x 100 mm wide Jumbo Bloks for both the inner and outer cavity walls. The walls were designed using H+H’s Aircrete Construction Details to minimise the amount of heat lost at the junctions of walls and floors. The 100mm cavity was filled with insulation. An additional 50mm of insulation was added to the outside of the wall, which was finished in a pre-coloured render system.

The separating walls between apartments were also constructed using the Thin Joint system, which enabled one block type to be used throughout the scheme. The separating walls are constructed from two skins of 100mm wide High Strength Jumbo Bloks with the 100mm cavity filled with insulation. A sound test on the walls proved the solution exceeded Building Regulations requirement by up to 8dB.

The Thin Joint system worked well with the limited storage available on the tight site, which has been slotted into the end of the back garden of an existing home. Because of the limited storage space just-in-time deliveries of blocks were made by PBS, a local H+H Aircrete merchant.

“Using Jumbo Bloks and the Thin Joint system was ideal because the mortar comes bagged and can be mixed in buckets, so we don’t need to have piles of sand and other materials lying around and taking up space,” says Michael Alderton. “The Jumbo Bloks are lightweight and relatively easy to cut and shape when compared to dense block so it definitely saved time – I’d use it again”.

In addition to the highly insulated building fabric photovoltaic panels were installed on the roof of the block to generate electricity from the sunlight. The panels supply one of the apartments, which achieved an EPC A rating, with the remaining apartments achieving a very impressive B-rating.