The eight strategies in the Communion Sustainability & Energy Creed help bring a focus and rigour to our thinking around sustainability, no matter the size or type of project we’re working on.
In this article, we look at how we apply the strategies in a new build dwelling.
We’re using as the example an exceptional new build dwelling, which we call Earth House. It’s a unique building, not least because it uses stabilised rammed earth for a significant part of its construction. The dwelling also makes use of locally grown oak, with the structural oak beams pointing to the very wood they were grown in.
Fabric
We’re deliberate about the materials we use, choosing options that lower a home’s heating demand and minimise embodied carbon. For instance, we recommend high quality aluminium or timber windows and doors instead of standard domestic uPVC.
Curved glazing along the east elevation is the showcase of the window systems used in this building, with curved double-glazed units and frames stitched into the stabilised rammed earth walls at each end of the crescent shaped living space. More conventional straight aluminium glazing systems are used for the bedrooms, circulation and study, with lift & slide patio doors allowing seamless flow between indoor and outdoor spaces.
The oak beams have been combined with steel posts and hidden connection details, all capped off with a Cross-laminated Timber (CLT) roof structure. A green roof sits on a Bauder mineral felt roof covering, with various fixed and openable rooflights, including the 6m long rooflight in the centre of the crescent living area, which flood the main spaces with lots of natural daylight.
The stabilised rammed earth walls are created with the soil and clay excavated from the site, carefully dried and stored by the site team for use when building commenced. Herefordshire aggregates were added to the clay mix to form the required density and workability, all under the careful scrutiny of the leading UK expert in rammed earth wall construction, Mr Pete Walker at Bath University. This approach has significantly reduced the embodied energy of the dwelling, with the rammed earth walls travelling less than 20 material miles.
Orientation
We consider how each room is positioned within the building and the direction it faces. The goal is to maximise solar warmth during winter while reducing the risk of overheating in summer.
An east elevation is unconventional for the main living space, but it is towards the excellent views into the Malvern Hills National Landscape and the estate owned woodlands, where a lot of the materials required to build the house have originated. Bedrooms all have south-facing lift & slide patio doors, which enhance the indoor/outdoor connection.
Airtightness
Air tightness plays a vital role in a building’s energy performance, which is why it’s a fundamental element of the PassivHaus standard – the leading international benchmark for low energy homes. Our goal is to prevent unnecessary air movement between indoors and outdoors in either direction, helping to cut heating demand. While Building Regulations allow 8 m³/h/m²@50 Pa, Communion works to a far stricter target of 1.0 m³/h/m²@50 Pa, an 87% improvement.
The timber frame elements of the house include Smartply to provide the airtightness and structural stability. The Smartply is then sealed to the rammed earth, glazing systems, roof structure and floor using various tapes and sealants designed specifically for the task. An air test will be carried out at completion of the first fix mechanical and electrical systems. This will prove the installation and highlight any improvements required before the building finishes are installed.
Ventilation
Buildings can’t be too airtight – levels below 3.0 m³/h/m²@50 Pa can negatively impact occupants’ health. For that reason, we pair airtight construction with effective ventilation.
Mechanical Ventilation with Heat Recovery (MVHR) systems extract stale air from bathrooms, WCs, kitchens and en suites and expel it outside. At the same time, they recover the heat from that outgoing air and transfer it to fresh incoming air, which is then supplied to living rooms, studies and bedrooms. With efficiencies above 85%, MVHR systems lower heating demand while still providing healthy, consistent ventilation for the people inside.
The house will benefit from three MVHR units, serving all areas. The ventilation units will run continuously, always ensuring high air quality inside the house. Each unit can boost the flow rate on sensing higher humidity or pollution and is totally automatic.
The building requires mechanical cooling to comply with Part O – Overheating of the Building Regulations. This has been achieved with a heat pump and wall mounted fan coil units, all concealed within the furniture designs.
Shading
In winter, increased solar gain is beneficial, but in summer the same heat can make interiors uncomfortable. Although shading is more commonly used in commercial buildings – where higher occupancy also adds to internal heat – we evaluate its usefulness in homes as well.
External solar shading lets low angled winter sunlight enter the building to warm the internal thermal mass, while blocking the higher summer sun to prevent overheating. This is especially effective when materials like exposed concrete floors, walls or ceilings are used, as they store heat exceptionally well despite concrete’s high embodied carbon. Where a more traditional finish is preferred, phase change plasterboard offers a suitable alternative.
The south elevation windows and doors benefit from a significant overhanging roof. This will limit summertime overheating while also allowing some winter sun to reach into the rooms. The house will be fitted with Lutron roller blinds in concealed pockets in the ceilings. The Lutron system can automatically lower the blinds on the hottest days or when the client is away from home. It also allows the client to adjust the level of the shades with the easy-to-use wall mounted controls.
Control
Once a building is occupied, we want clients to be able to easily understand and manage their building’s systems and energy use. We therefore choose solutions that are sophisticated enough to meet current and future needs, yet straightforward for users to operate.
Heating and cooling will be controlled with an interlocked Heatmiser thermostat for each room. The Heatmiser system will be integrated with a home automation system, with fixed tablet on the wall in the main living space along with a mobile tablet for use around the house, all in addition to the Lutron lighting controls in each room. Security systems, CCTV and gate control will all be controlled from a single device, with options for adjustments as systems change over time.
Monitor
It’s also essential to monitor building systems so we can understand how energy is being used. With this insight, we can identify ways to lower energy demand during peak times. For this reason, we install meters and sub meters on high consumption systems such as heating and lighting.
Energy monitors will be provided on all significant energy consumption devices, principally the heat pumps, chiller, lighting and any other circuit as required. This energy monitoring can be fed into the home automation system if required.
Reporting
As part of our commitment to the RIBA 2030 Climate Challenge, we share anonymous data on the energy performance of our buildings during their first year of occupation. This contributes to a broader, real world dataset that helps accelerate learning across the industry and the wider community.
As this is a unique build type in the UK, the entry into the RIBA register of buildings with climate information may be complex. We hope that this will inspire other architects and engineers to use the materials they have on site in place of importing materials.
If you’d like to explore the Earth House and its development in more detail, you might like this YouTube playlist.
