Pound Lane

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Pound Lane

Address: Woodlands, Pound Lane, Laughton BN8 6BE
Owners: Dave and Stephanie Kennaird
Type: semi-detached
Beds: 3
Walls: cavity filled
Residents: 2 adults 2 children

Eco Features

Combined heat and power (CHP)
Superinsulated attic conversion
Woodburning stove(whole house)
Cavity wall insulation
Double glazing
Solar PV (2kWp)
LED/CFL lighting

Summary

When Dave and Stephanie bought this house in 1997, it already had cavity wall insulation and uPVC double glazing. Dave has since converted the attic, using extremely high levels of insulation.

Based on his engineering expertise, Dave set up a CHP system using a marine diesel engine, which successfully provided most of the electricity and heat for over 10 years, until very recently. It has temporarily been retired, as the new woodburning stove with back boiler currently provides most heating needs. When the planned rear extension is carried out, the CHP will be reconfigured to meet the increased heating load.

Electricity needs are also met by 2kW of solar PV, helping to ensure the house has a fraction of an average house’s energy use and CO2 emissions.

 

Energy efficiency measures

Heating and hot water

CHP – A Mitsubishi marine diesel ac generator in the outside shed was set up to generate 7kW of electricity, with surplus stored in 24V lead batteries, as export to the grid was not allowed when it was installed. Electricity used in the house was drawn via a 24V to 240V invertor and the CHP unit was microprocessor controlled to respond to electricity demand, particularly during the evening peak when the all-electric cooker was in use. Heat from the engine was taken via a plate heat exchanger in the cooling circuit, as well as heat recovery from exhaust gases, making it able to deliver up to 12kW of heat at extremely high efficiency. This was channelled to the house via underground insulated pipes to a thermal store, from which heat could be drawn. Any surplus heat was either stored in an external insulated buffer cylinder or directed via a network of storage heater bricks below the conservatory floor.

This system was run from September to April, when there was a demand for heat, typically running for three hours per day, and used a very modest 600 litres of oil a year (7000 kWh).

During the summer, water was heated using electricity.

Woodburning stove – A 9kW Stratford woodburning stove is now fitted in the lounge, which has a back boiler that delivers heat to a 250 litre thermal store in the room above. Heat is drawn off from this to supply radiators, which were oversized to cope with the slightly cooler output from the CHP. The store has two immersion heaters as back up heating and has an additional coil for solar thermal, as and when funds permit.

This arrangement has proved so successful that it was possible to stop using the CHP, although this will be reconfigured to supply top up heat and power when the large planned extension is built.

Insulation

Attic conversion – The sloping roof is insulated with 50mm Celotex PIR insulation between the rafters and two layers of multifoil Spaceblanket insulation cross battened over that, finished with 25mm Celotex and plasterboard. This arrangement is equivalent to over 500mm of rockwool, far in excess of building regulations, giving a u value of around 0.09W/m2K.

The dormer sides and roof, plus attic flank wall are both insulated with 200mm Celotex, again well beyond required standards, with u values of below 0.11W/m2K.

Walls - The cavity walls were filled some years ago, with u values now about 0.45, which is perfectly acceptable.

Windows – the existing double glazing is some years old, but still performs well although the u value is probably a little higher than current standards (1.8) at about 2.2 W/m2K.

Renewables and Low carbon technology

2 kWp of Solar PV was installed on the front roof. As Dave teaches PV installation, this was done quite economically and receives FIT at the higher rate.

Electricity

Low energy LED lighting has been installed throughout, cutting the lighting load to 10/20% of old halogen and incandescent lamps.

Lessons learned

CHP – the existing unit is ac, but this has the disadvantage of only being able to operate at constant speed, which made it necessary to coincide use with peak demand, via microprocessor control, to get good efficiency. When CHP is reconfigured it will probably be a dc unit, which can operate at variable speed, which will more efficiently match output to demand.

Spaceblanket – This insulation needs to be fitted very carefully, leaving space around it to avoid compression, which can radically reduce its insulating properties.

Gallery

Pound Lane