Constructing a low-energy home

January 12, 2022

Our clients in Portishead are about to start work on site building their new low-energy family home. The brief for the project was to create a home which is super-insulated, airtight, uses very little energy to heat, and is also cost-effective to build.

The starting point to achieving this was to keep the form simple and compact - limiting the external surface area and avoiding unnecessary junctions, to both reduce heat loss and keep construction costs down. The orientation of the building is important - the site is a south-facing slope, and windows have been predominantly located on the south elevation to take advantage of solar gain in winter. To protect the house from overheating in summer, an overhanging roof and balcony structure will provide shading.

The high performance envelope will be achieved by entirely wrapping the structure externally in high-performance insulation - avoiding any ’thermal bridges’ through the insulation layer which are common in traditional construction methods and allow heat to escape. The slab will be poured on top of a layer of rigid insulation, single-leaf masonry walls will then be built off the slab and insulated externally, and the roof will be formed from slender timber i-joists fully filled with pumped insulation. The house will have a high level of airtightness - which is critical for preventing heat loss, improving comfort as well as protecting the building envelope - combined with ventilation provided by an MVHR system. The construction details have been developed collaboratively with Dodden Energy Efficient Construction (https://www.dodden.co.uk/), who have developed and used this construction methodology to build eco-homes across the South-West.

More information will be posted as the project progresses on site.