Sustainable and energy efficient design

— 15 Oct 2024

A recently converted and extended property in north devon has been designed with sustainability and energy efficiency at the forefront of the design brief.

The building was an office and garage below and has been converted to a dwelling re-using substantial amounts of the original structure and services, thereby utilising the embodied energy and existing materials within the building.

The new dwelling also significantly exceeds current and 2025 proposed Building Regulations standards, with the following sustainability measures incorporated:

• 2kw PV roof panels generate significant proportions of the electrical and heating demand
• 10kw battery storage to retain generated power and run domestic loads and heating and hot water requirements in all but the coldest days of winter
• External insulation (approximately 30% higher than 2025 Building Regulations standards) to reduce energy demand
• Heat recovery ventilation system to recover 75 - 90% of waste heat from ventilation
• Air Source Heat Pump (ASHP) to provide low carbon heating source
• 7kw woodburner to augment the ASHP in cold weather and utilise sustainable timber sources from surrounding hedgebanks and trees

The solar panels are a key part of the sustainability measures. They are designed into the roof, in effect performing as large glass roof tiles. This means there are no wasted building materials, by installing a roof and then installing solar panels on top.

The system is designed to provide enough electricity to run the entire 196m² house for several months of the year with little or no demand on the mains grid. The supply will first go to the power consumption of the house including running the ASHP; then it will go to batteries; when these are full any excess will feed into immersion heaters in the hot water storage system.

The predicted energy assessment for the property – which rates the energy use per square metre of floor area and is based on fuel costs and carbon dioxide emissions – is an energy efficiency rating of 94 and environmental impact (CO²) rating of 99, putting it firmly into the top A category.

It will be interesting to review the outcomes of the energy usage of the property when it has been in use for a period of time.