The Arc, Boxford

The Arc
The Arc
The Arc
Building typeDomestic
Building Agepost 2000
LocationCO10 5JU
Cost of work£320,000
DistrictBabergh
FeaturesSolar Hot Water Heating,Solar PV Panels

Introduction

This building was conceived to fulfil three separate, but complementary design criteria:

  • We required a four bedroomed residence which conformed to a contemporary design aesthetic
  • The structure minimised embodied CO2 and moved towards ongoing carbon neutrality, without compromising normal activities of daily living
  • Use of high thermal mass and passive ventilation targeted a low humidity healthy living environment

The building was therefore oriented on the site to maximise solar gain and wind capture, with extensive use of recycled and substitute high density materials to enhance its heat-retentive capacity. It’s performance is telemetrically monitored as part of a UEA research project, although results from this are not yet available.

Sustainability Features

Footings and floors

Excavated soil disposed of to a local above-ground site (landscaping of golf-course). 200mm moisture-protected Celeotex insulation under concrete (see comment under “insulation” below)250 mm reinforced raft formed using 50% cement-replacement concrete. Backup underfloor low power (75-100W/m2) electric heating cables (Deviflex DSIG-10) laid 50mm under surface. This is the only powered heat source in the house. Top surface of slab power-floated to form final finished floor surface. No screed or secondary surfaces used

Walls

All walls were constructed from 2 x 100mm thickness dense recycled aggregate blocks. Two types were used:• Masterblock Enviroblock EV11 – 100% recycled aggregate• Fyfestone Enviromasonry – secondary recycled aggregate + cement replacement. Internal surfaces are all exposed blockwork, either painted fair-faced, or unpainted fairfaced blocks. The only use of plasterboard in the build was for a few minor locations where fire protection for structural components was required. Externally, the walls were covered with Celotex, 225mm to north-facing walls and 150mm to other walls. This was then rendered. Owing to very cold weather at the time this was applied, unfortunately we had to use cement-based render for the base coats.

Insulation

Owing to the extremely high levels of insulation required, natural materials were not an option for this build. The thickness required for materials such as sheep’s wool or hemp would have been to great to allow structural security of the walls. Faced with the need to use a synthetic material, we chose Celotex, not only because of its performance, but also because the factory where it is manufactured is just 4 miles from the building site. Given the huge quantities and bulk of insulation required for the build, delivery of this item has a potentially significant carbon impact on the build.

Windows

The whole south face of the building is glazed to maximise solar gain. The windows use Pilkington energiKare, a double glazing unit that has an outer panel with high solar transmission and an inner panel with high heat reflection. Frames are made of farmed French oak

Roof

The roof is covered with 93% recycled aluminium. Underneath is a further 200mm Celotex

Space heating

Primary space heating is by passive solar, combined with the high thermal mass of the building. Backup heating is by low-power underfloor electric cables

Further backup is supplied by a wood-burning stove in the main living area. There is no boiler-based system. Over the course of the past winter 2009-10 we have be very warm. Given the sustained low temperatures that we have experienced, this has been a good proof of principle.

Solar Water heating

Hot water is supplied by a 30 tube Thermomax DF100 solar collector coupled to a 300 litre cylinder

Backup is by electric immersion heater

Water

All roof water and some ground water is collected and stored in a 5000 litre tank buried under the drive. This is filtered and supplied by a demand pump for toilet cisterns, washing machine and garden tap. In 2010 we intend to upgrade the purification system to allow us to use this supply for showers as well.

Design Process

Our intent was to show that it was possible to build in an environmentally sustainably fashion without compromising either in terms of design aesthetic or the needs and expectations of a modern family. We do not believe that the way to achieve carbon neutrality is to force families to live in a pre-industrial environment – rather we have to find ways in which technology can be employed to make modern life environmentally viable. Broadly speaking, the planning authorities have been supportive although some aspects of the build, particularly the wind turbine, have triggered opposition within the Parish Council. Ultimately, however, although the process was rather drawn-out, and we needed to make some modifications to accommodate the requirements of the tree officer, the finished house is pretty much as originally designed.

Grants

£400 from Low Carbon Buildings Programme.

£500 from Babergh District Council. Both in respect of solar panel.

Unfortunately, because the wind turbine was a product in development and had not been officially recognised at the time it was erected, we could not get a grant towards its cost.

Green Lifestyle

We have always tried to live in as green a way as possible. We certainly recycle everything that is recyclable. We are looking to increase the amount of rainwater that we use. Every light bulb in our house is either LED (75%) or CFL (25%). Appliances are all A rated or better and the cooker is an induction hob. One of us works from home. The other works a 15 minute drive away. At the moment I use a small diesel car (public transport is not available). If I could afford it, I would buy an electric car. If I was brave, I would cycle!

Evaluation

Overall, the building has worked well. Considering that this was a self-build and neither of us had any substantive prior building experience, the whole thing has gone remarkably well.

Very good

Overall design, aesthetic, warmth, power-floated floors, windows, rainwater harvesting, water heating, wood-burning stove

Needs work

Wind turbine (but getting there), passive ventilation stacks (condensation problems), privacy (many curious people!)

Would do differently next time

More effective quantity surveying (inexperience shows), better financing (has been a struggle)

If money was no object

Take a sabbatical from work, so I didn’t have to work full time at the same time as managing the build.

Explore photovoltaics – somewhere out there, there has to be a viable system for the UK climate

Investigate sensible energy storage, other than batteries (phase-shift materials, electrolytic plants etc)

Get someone else to do the decorating!

Suppliers and professional services used

As a self-build, we were utterly dependent on the quality, expertise and dedication of our contractors. For that reason, this list is longer than that of the other case studies but we believe it is very important to recognise and thank those who have contributed to the project.

  • Architects: SeARCH Architects, Spalding
  • Engineer: Charles Tallack, Cambridge
  • Groundworks: MB Contracts Ltd, Halstead
  • Blockwork: Roberge Brickwork, Halstead
  • Joinery- External: Chas Crocker, Harwich
  • Carpentry and Joinery: Joe Carpenter, Sudbury
  • Joinery- Internal Doors: Thorrington Joinery
  • Glazing- Abbey Glass Ltd
  • Rendering- Fred and Adam Crisell, Sudbury
  • Electrics- Peter Cutmore, Sudbury
  • Leadwork- Newgen Roofing, Halstead
  • Roofing- Steve White Industrial Roofing, Ipswich
  • Plumbing- Plumlec, Sudbury
  • Solar Hot Water- Solarworks Ltd, Sudbury
  • Underfloor Heating- Elements, Ipswich
  • Wind Turbine- Skyrota, Limavady
  • Building Supplies and site services: Ridgeons Ltd, Buildbase (Sudbury and Hadleigh), MTM Plant Hire (Sudbury), Turner Tool Hire (Sudbury)

Awards

Featured on Grand Designs in 2010.

See all entries under Suffolk Case Studies

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