Regenerative design at Sherwood - another Certified Passivhaus, A rated and Zero Carbon House by G&S Architects

At G&S Architects we are pleased to add another certified Passivhaus project to our growing number of certified schemes throughout the country. Recently certified by the Passivhaus Institute, Sherwood also achieved an A rated EPC and Zero Carbon status. Furthermore, Sherwood has recently been short-listed for an LABC (Local Authority Building Control) award in the Best Individual New Home category.

Designed into the landscape following both Permaculture and Building Biology principles, Sherwood highlights how an integrated approach to design can still produce a highly contemporary aesthetic.  Buildings can be built to look beautiful and still be ecological, low energy and zero carbon as well as being healthy spaces to live in.  

What makes this scheme all the more remarkable is the fact that our client took on the project as a self build. Being a challenging site, with high design targets and aspirations, they rose to the challenge and exceeded all expectations. They have produced their own blog which tells the tale of their remarkable eco house build journey.  

Key strategies include:

Permaculture 

One of the key features and challenges of the design was to integrate the building into a sloping landscape following permaculture principles.  

The sloping landscape presented a major design challenge at the beginning of the project, however it later proved to form one of the key design principles of the scheme. Being south facing, the site helped to orientate the building in order to achieve the passivhaus target. The building is dug into the south-facing slope and topped with a curved turf roof so as to maximise solar gains and blend into the immediate surroundings. The sloping elevation then enabled a permaculture zoning strategy whereby seven layers of forest garden have been planned. This consists of an edible community of species designed to mimic a natural ecosystem. The scheme includes an aquaculture irrigation system, wildlife pond and forest garden.   

Sherwood elevation and zoning

Sherwood site plan

Building Biology 

Sherwood incorporated healthy building design based on Building Biology principles featuring: non-toxic materials, designing out dust mite habitats, minimising electromagnetic radiation through wiring specification and design (radial wiring and EMR dampening switching), high levels of air quality, thermal comfort and daylight levels, potable water filtration and cleaning system. Whilst contemporary in its design, the materials and detailing used reflect local traditions.  Natural materials have been specified throughout such as timber shingles, a green roof, timber windows and doors, untreated timber cladding and stone facing.

 

Passivhaus: fabric low energy design

The low energy design to Passivhaus standards has resulted in high thermal comfort levels, minimal CO₂ emissions and greatly reduced energy consumption.

Thermal Mass:  Inclusion of thermal mass has been provided in the load bearing ground floor construction using solid internal walls and floor slabs. Thermal mass reduces internal temperature fluctuations and helps reduce energy use. The building was also built into the earth bank.   

Optimum Orientation: The building has been dug into the south facing slope and features a double heighted living space, forming a tower in the centre of the design. The high levels of south facing glazing that form part of the tower maximise beneficial solar gain. Mass and high level roof openings which creates a stack ventilation effect help maintain summer comfort levels.  

Super Insulation: 

Walls to achieve high insulation levels U-values < 0.15 W/m²K.  

Highly insulated roof and floor constructions achieve U-values < 0.1 W/m²K.  

Triple glazed windows, high performance timber frames U-values < 0.1 W/m²K. 

Low energy building services design

Gale & Snowden's integrated design approach ensures that building physics, architecture, permaculture and mechanical and electrical systems are all considered at early design stages so that optimum and minimal solutions are arrived at.   

This holistic passive design strategy allows the house to be designed without a conventional heating system. At the same time, it will avoid overheating in summer and have minimal environmental impact. 

Our in-house services design team developed a simple services strategy for the scheme.

 
Mechanical Ventilation with High Efficiency Heat Recovery (MVHR)  A highly efficient MVHR was installed linked into an earth tube supply duct.  The earth tube tempers the incoming cold air in winter and Tempers warm summer air to help maintain summer comfort levels. 

  

Heating & Hot Water  Heating was met by a small wood burner with back boiler and thermal store.  A solid Isokern chimney system helped retain the heat from the flue gases as can be seen from the below thermal image. 

The minimal heat load was distributed to the perimeter zones by an innovative in wall heating systems.

The scheme is supported by a roof mounted PV array with a modulating controller to match the thermal store immersion back up element in summer. 

As part of the G&S integrated approach we also ensure that services are installed and commissioned correctly. For Sherwood’s we were on hand to assist with the M&E installation and MVHR balancing. Please see our engineering review during the construction phase here.

The scheme was truly a collaborative effort between designers, the client and on site installers. G&S Architects are proud to have been on this journey with the client to help them realise their dream of living in an innovative and ecological home. 

What the client had to say about us: 

We chose Gale and Snowden for their Passivhaus knowledge and experience.The outcome is an outstanding zero carbon home which has far exceeded our expectations. It is a real pleasure to live in. The central atrium and eyrie are architectural highlights. Importantly, the internal space is highly flexible which suits our lifestyle and hobbies perfectly. The use of healthy materials combined with ventilation and Winter heat recovery means that we enjoy excellent internal air quality and comfort all year round. The careful thought that went into the design and construction of the fabric of the building eliminated the need for active technologies such as central heating - one of the advantages of following a Passivhaus methodology.  Consequently, the house benefits from very low running and maintenance costs. As well as a detailed spec and comprehensive drawings, the team at Gale and Snowden also gave us timely and well informed advice during the construction phase. This assisted the smooth running of the building process and ensured the construction was up to the required standard for Passivhaus certification. It also helped us to keep the project on budget.