Vicarages do not have a reputation for being at the cutting edge of sustainable design. Such heretical notions are about to be absolved with the completion of a cutting edge design for a rectory.
The Zero Carbon abode sits angelic among its neighbours at Penzer Street, Kingswinford, near Dudley. The vicarage claims to be the first scheme in England to meet both Passivhaus and Code Level 6 standards. This officially means that the saintly scheme can claim annual carbon emissions of zero.
As a result, the building's annual energy demand is predicted to be 8000 kWh. Impressively, this is less than a third of the old vicarage's 26,000 kWh demand.
The building cost £1965/m², which is approximately 30% above the comparable costs for standard construction. However, these additional costs are expected to give a payback of around eight years.
The client, the Diocese of Worcester, was fervent in its sustainable zeal and wanted to make a bold 'green' statement. The Worcester Parsonages committee wanted to demonstrate that it was possible to build a house with minimal environmental impact. Their fervour was fuelled by the Church of England's aim to reduce its carbon footprint 80% by 2050. This aligns with the UK Government's 2050 carbon commitments.
Designed by John Christophers of Associated Architects, the trinity of floors was entirely coincidental. The ground floor contains the vicar's study and living room. Moving up, the middle floor houses a kitchen-diner, a family room and a study-cum-guest bedroom. Transcending both is the top floor, comprising three bedrooms tucked into the roof-space, lit by windows set into the roof.
Christophers is experienced at low-energy architecture having designed his own house to zero carbon standards. His experience influenced the design of the eco-vicarage:
"I was able to bring some of the lessons learned, such as the use of thermal mass with high levels of external insulation…" he says.
The high pitched roof visually hints at a spire. Coupled with pristine white render, you get a sense of the spiritual. Acrylic brick slips and blue-black slates help to blend the otherwise stark building into the neighbouring properties. The roof-mounted solar panels, however, give a hint at the vicarage's low carbon credentials.
This building is so well insulated that it can be heated from sunlight. Sunlight is also used to generate electricity and hot water for the vicarage. It is so energy efficient that on sunny days it will actually generate more electricity than it can use. As a result, estimated annual fuel bills are expected to be less than £100.
The scheme has been designed using the Passivhaus 'fabric-first' approach, ensuring energy demands are kept to an absolute minimum. To achieve the high sustainability standard, Sto's Passivhaus certified StoTherm Classic K (Lamdatherm) system was required. The system combines a number of high performance materials:
- A 250mm depth of Neopor graphite-enhanced expandable polystyrene insulation
- StoArmat Classic, a highly flexible, crack resistant intermediate coat
- Sto Armour Mesh for additional crack and impact resistance
- Performance render finish (natural white)
- Acrylic brick slips to complement the neighbouring properties
"The Diocese was very keen on highly energy efficient houses because they know that their energy bills will be very low for a very long time," says Christophers.
The highly insulated, air-tight shell means it can be heated primarily using passive, renewable sources:
- Solar energy
- Geothermal energy from the ground
- Body heat generated by the occupants
All the principal rooms face south and incorporate large triple-glazed windows to collect the winter sun. Rooms are flooded with natural light helping to reduce the need for artificial light as well as providing heat. Recessed, electrically-operated and manually controlled blinds prevent the rooms getting too hot in summer. Spaces that are less natural light dependent have all been pushed to the shaded, north side of the building.
Remarkably, the vicarage does not need a boiler. The super-insulated eco-vicarage is heated by simply using the fresh air supply for the occupants. Unusually for a UK Passivhaus, the air is drawn into the building through a clay pipe, buried underground. Because the ground is at a constant temperature of 12°C, the pipe tempers the incoming air. In winter it will be warmed by up to 9°C while in summer, cooled by up to 14"C.
The thermal efficiency of the building is aided by its airtight construction. This necessitated a Mechanical Ventilation Heat Recovery (MVHR) system installed to extract stale air from the rectory's kitchen and bathrooms. During winter, stale air passes over a heat exchanger, transferring heat to the incoming fresh air before it is exhausted. This process can be bypassed in summer for more comfortable climate control.
Using Sto external wall insulation ensures that the interior has a large area of exposed plastered blockwork. This offers the dual benefits of maximising internal space and providing thermal mass to help moderate internal temperatures. "The use of thermal mass with high levels of thermal insulation has the advantage of reducing peak summer temperature and increasing winter temperature, which also helps protect the scheme against projected changes to the climate over the next 50 years," explains Christophers.
Renewable technologies are used to ensure the scheme is Zero Carbon over the course of a year. Hot water is provided from 5m² of roof-mounted solar thermal evacuated tubes. The tubes will qualify for a small income from the forthcoming Renewable Heat Incentive. The heated water is retained in a 550 litre store and available at any time of the day or night.
In addition to the solar thermal collectors, the roof also accommodates 42m² of solar photovoltaic (PV) panels. The panels enable the vicarage to generate its own electricity from sunlight. "On a sunny day the panels will easily generate more electricity than the vicarage can use," says Christophers. The panels will generate revenue for the vicarage through the Government's feed-in-tariff scheme. The scheme also harvests rainwater for use in the washing machine, for flushing toilets and for watering the garden. Low energy lighting is used throughout.
Eco Vicarage on Walkers Lane, Webheath
The eco-vicarage at Walkers Lane has also been built to Code Level 6, but falls just outside Passivhaus standards. Like Penzer Street, the scheme is also for the Diocese of Worcester and similarly incorporates roof mounted solar PV panels.
The rectory's Sto facade incorporates the same high levels of insulation as the Penzers Street vicarage. However, because of the more rural location, render has been combined with timber to create a more rustic rainscreen solution.