Lewes Eco Open Houses 2016

15 - 23 Oct 2016

House 06

Energy-saving improvements

  • Low-cost improvements
    Low-cost improvements
  • 'Big' insulation works
    'Big' insulation works
  • Glazing
  • Lighting systems and electrical appliances
    Lighting systems and electrical appliances
  • Sustainable building materials
    Sustainable building materials
  • Lifestyle change
    Lifestyle change


8 St. James Street
East Sussex

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Opening times

15 - 23 Oct 2016
Saturday 15th October 1-5pm
Saturday 22nd October 1-5pm

This event has now finished.

Just turn up


Type: 3 bed, end of terrace, brick walls                                                          

Built: 1789                                                                                                                      

Area: 90 m2                                                                                                                     



Room in roof insulation

Condensing Boiler

Conservation timber DG sash window

Flat roof insulation

LED lighting                                                                                                                    

Secondary double glazing (magnetic)

Solid wall insulation (internal)

Underfloor insulation

Vegetable beds and fruit trees

Woodburning stove



In August 2012 Neil bought this house and just before moving in, the attic was stripped and solid wall insulation was fitted internally in the two reception rooms.

Subsequently, the attic was relined with high levels of insulation, to put a snug cap on the house.

A woodburning stove was added to the sitting room, with cellar insulation underneath.

All lights were replaced with LEDs and new appliances were A to A+++. Cheap and near invisible magnetic secondary double glazing has been fitted to four windows.
In 2013 the ceiling of the rear extension was stripped to fit much better roof insulation. In 2014 raised beds were added to the garden for vegetable production, as well as espalier fruit trees.

Developments in 2015/6 - more solid wall insulation for hall wall and back bedroom - cellar stairs insulated - new timber double glazed sash window - new highly insulated timber framed extension - more magnetic secondary DG.
Energy use is now around 40% of an average house which is not bad for a leaky Georgian building. When PV is fitted, carbon emissions will be down by 90% and could reach reach zero carbon.

Refurbishment has cost £7500 (excluding the extension), of which £1500 was for essential roof strengthening. Net 'eco' expenditure is therefore £6000, most of which was DIY with friends.

This is a work in progress, applying principles learned from an MSc in Sustainable Architecture. The guiding principle has been to go for the most cost effective energy saving measures.


Energy efficiency measures

Heating and hot water

The house already had a modern condensing boiler supplying water to a well insulated pressurised cylinder.

A woodburning stove in the lounge helps cut down the gas use and heat percolates upwards to the bedrooms.



The lath and plaster ceiling was stripped out in the loft mainly to raise the head height from a tight 1.95m to over 2.4m. In the process it was apparent there was no insulation, so 50mm Celotex PIR foam boards were slotted between the rafters, taking care to leave a ventilation space of 50mm above, to allow the roof to breathe and avoid condensation. All joints were taped to avoid infiltrating air coming from behind and undermining insulation.

The flank wall was very uneven and was stripped back to brickwork, levelled with hardwall plaster and overboarded with laminated plasterboard, formed of 9.5mm board bonded to 19.5mm foam insulation. The chimney breast and party wall were also clad in laminated board, which was carried up over the sloping ceiling and eaves walls to improve overall insulation and limit cold bridging via the rafters.

In the eaves themselves, Celotex insulation was carried down between the rafters and rockwool was placed between the ceiling joists, which were overboarded to create storage. The eaves joint needed careful detailing to prevent draughts and divert ventilation above the insulation.

The aluminium double glazing in the attic was retained, even though not to current standards, as it is still pretty effective and in good condition.

Front sitting room
Slim laminated solid wall insulation (28mm and 37,5mm overall thicknesses) was fitted to the outside walls, so as to encroach as little as possible on already limited internal space. The board was fixed using Dow InstaStik adhesive foam and the board secured with Insofast drywall fixings. This cut heat loss by around 70%. In order to fit the insulation it was necessary to remove skirting and architraves, undo light fittings, switches and sockets and take down the radiator. This sounds complicated, but it happened very quickly and easily. Before the board went up, the position of those fitting was marked, so that they could be easily reinstated. The only complication involved creating slightly deeper reveals around the windows and doors by fixing battens around the perimeter, to which the conserved architraves could be refixed.
One big cost bonus of using laminated board with tapered edges is that joints can be taped, filled and sanded ready for decoration without the need for plastering the whole wall. This is very sustainable, avoiding high embodied energy plaster.

Below the sitting room there is a cellar and it was very easy to fit 170mm rockwool loft insulation between the joists from below to insulate the floor.

The front window was insulated using magnetic secondary double glazing which is virtually invisible and only cost £60 in total. This cuts draughts and makes the small room far more usable and comfortable.

Garden room

The side walls of this extension were leaky single skin brickwork. These two walls were overboarded with Celotex PL4000 laminated board (37.5mm overall), which has cut heat loss by 70%, without impacting on space. Because of the clearness of the walls this was done by two people in half a day, with a minimum of fuss.

The timber ceiling was believed to be insulated with rockwool between the joists, but during the winter it was easy to observe that frost and snow quickly melted to reveal the pattern of ceiling joists, indicating no insulation. This was resolved by stripping the plasterboard and inserting 100mm Celotex PIR between the joists. The whole job took two days with a friend, including decorating and has had a huge impact. The room stays warmer in winter and is also much cooler in summer as sunshine on the flat roof used to radiate straight through to the ceiling. On sunny days the ceiling temperature used to reach 30 degrees plus!

The garden doors are fairly recent with timber framing and double glazing. However the single glazed window now has a magnetic secondary double glazing panel, which is virtually invisible but cuts heat loss by half, for a cost of about £40 all in.

One of the most effective insulation measures was to put DIY cardboard panels coated with aluminium foil behind the radiator on the external wall. This immediately raised the temperature in the room by 1.5 – 2o C, as the radiator no longer had to heat the brickwork and could give its energy to the room. This cost virtually nothing, but saves several hundred kWh each year, as well as making the room far more comfortable.

Renewables and Low carbon technology

With only one resident hot water use is pretty low, which makes it hard to justify solar thermal water heating.

A better investment would be solar PV on the roofs of the extension and summerhouse. This depends on whether there is enough room for panels to give an economic output and is currently being investigated.


Low energy LED lighting has been installed throughout, cutting the lighting load to 10/20% of old halogen and incandescent lamps. The former halogen fittings were easily converted to LED GU10 by a local electrician for less that £5 each. This measure saves a massive 500 kWh pa for very little expense and savings will recoup costs in under two years.

With all lights in the house on, the total load is only about 100W, i.e. the same as one old light bulb!

The low energy fridge freezer and washing machine are A+++ or as near as possible.

Other sustainable Measures
The end of the garden has been used for raised beds for vegetable growing. In spring of 2014, fan trained fruit bushes and trees were planted along the south facing fence to both maximise space and grow more produce.
Natural Materials

The summer house was built with UK oak, fixing carbon and creating a durable structure that might be converted to an enclosed room, if future residents need the space.
Lessons learned

This house had an EPC rating of E, but was probably more like F or G, as the assessor had wrongly credited it with loft and flat roof insulation, when there was none. It also failed to take into account the wafer thin flank wall which is only half a brick thick. This highlights the inadequacy of a poorly regulated EPC system, which can produce misleading information.

Builder: Marc Cable,
M.B. Cable Ltd, Lewes. 07739127901, cable.m@sky.com

Solid wall insulation: DIY with much assistance from plasterer Steve Huckle.
Laminated plasterboard Insulation: Celotex PL4000. http://www.celotex.co.uk/products/pl4000
Woodburning stove: David Sibley, Energy Wake Up Ltd. http://www.energywakeup.co.uk/
Magnetic secondary double glazing: see link for information and local suppliers http://transitiontownlewes.org/magnetic_secondary_double_glazing.html


8 St. James Street
East Sussex

View on map

Opening times

15 - 23 Oct 2016
Saturday 15th October 1-5pm
Saturday 22nd October 1-5pm

This event has now finished.

Just turn up

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Part of the Green Open Homes network