Baldy's Garden

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Baldy's Garden
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Details

Address: Baldy’s Garden, Cuilfail, Lewes, BN7 2BE
Owner: Paul and Louise Bellack
Type: Detached
Built: 2006
Beds: 5
Walls: Timber frame

Eco Features

Timber frame construction
Natural materials, locally sourced
Superinsulation
Airtightness
Solar thermal hot water
Solar PV (3.6kW, South facing)
Rainwater harvesting

Summary

The ugly and inefficient bungalow originally occupying this site was demolished to make way for the beautiful superinsulated structure designed by local architects, BBM. Owners Paul and Louise went for the most sustainable specification, building off the foundations of the original building and using locally sourced timber and natural materials throughout. The building is largely timber framed, with hemp/cotton breathable wall insulation. The external finish is part timber clad and part lime rendered.

Underfloor heating coupled with thermal mass in the ground floor helps stabilise temperatures, whilst maximising solar gain in winter. Both solar thermal hot water and PV greatly reduce energy consumption, as well as rainwater harvesting. Overall the building performs excellently, with only 10kgCO2 emissions/m2 and about 50% less mains water use. Energy use is only around half that of an average house, which is extraordinarily low, considering it has three times the floor area.

Lessons Learned

Flat roof – this proved problematic, largely because the specialist contractor who laid the membrane did it very badly, causing leaks. Also the black membrane had high solar gain, even with roof insulation, causing upper rooms to overheat. The flat roof was rebuilt after five years with a better fall, using white membrane, which greatly helped to reflect heat and also increase output from solar panels.

Heat gain in upper rooms – as well as the roof, there was excessive solar gain via windows. This has largely been resolved by using reflective film. Originally, the upper windows were to have been shaded with brise soleil slats, but this detail was removed at the time of building, due to cost.

Chestnut cladding – chestnut leaches tannin for some years, which needs to be taken into account when decorating externally.

The lime render, although attractive, has proved a little fragile and subject to hairline cracking and chipping at corners.

Rainwater recycling – ideally the building would have had a living roof, but this would have interfered with rainwater recycling which was a priority.

Hemp and cotton insulation – this is very hard to cut, which made it difficult to work with.

Passive solar heat gain – Thermal mass in the ground floor and large south facing windows means that in winter the building receives huge amounts of heat from the sun, which greatly reduces fuel use.

Energy use

Electricity used – 4000 kWh
Electricity generated – 3200 kWh
Gas – 10,000 kWh
Wood – nil
CO2 Emissions - 2.6 tonnes pa, 52% less than an average house
50% Water reduction (versus average).

Professionals

Architects: BBM Sustainable Design, Cooksbridge. www.bbm-architects.co.uk
Builder: Dermot Burton, Westmeston. 01273 842118.
PV Solar: Suntrader Solar Energy, Brighton. www.suntrader.co.uk

Gallery

Baldy's Garden