Energy efficient renovation of an older house

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CONSTRUCTION: Typical small early twentieth century solid-wall house.

KEY FEATURES: internal and external insulation, solar pv, wooden double and triple glazing, solar gain conservatory, and LED lighting.



The owners wanted to make some significant alterations to the house, so approached us for advice on how to make it more energy efficient at the same time – they were keen both to reduce their energy bills and help the environment by using less fossil fuels and generating electricity.

Energy Performance Certificate

A before and after EPC showed that the improvements had doubled the energy rating from 43 (E ) to 86 (B).

Before After
Energy Rating 43 86
Gas consumption p.a. 11,613 kWh 6,903 kWh
Electricity generation p.a. 0 1,500 kWh
Carbon emissions p.a. 5.5 tonnes p.a. 1.1 tonnes

The table below shows the effect of each improvement incrementally:

Improvement Rating after improvement
Seal open chimney 44
Wall insulation 59
Draught proofing to doors 60
Double/triple glazing 64
Bathroom ceiling insulation 66
Disconnect decorative gas fire 72
Solar PV 86

Before and after improvements:

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No cost and low-cost improvements

Not all the improvements cost money – we were able to advise on the most efficient way to use and control the central heating, using a wireless room thermostat. The gas coal-effect open fire in the lounge is only 30% efficient, and the chimney caused draughts, so it was blocked up the fire disconnected.

A thermal imaging camera showed draughts around the front and back doors. Additional draught proofing is a very simple measure. We also advised using LED fittings in the new lighting.

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Wall Insulation

Solid wall insulation is less easy and more expensive than cavity wall insulation, but with a house like this, there are no cavities. 50mm phenolic board insulation was fixed to front wall internally, so that the outside appearance from the street was unaltered. The side and rear walls were insulated externally, giving a smart rendered appearance. “Breathable” products and brick effect finishes are also available.

“The insulation work was quite disruptive and noisy, with scaffolding outside and radiators and skirting boards needing to be removed inside, but we are pleased with the result – both the appearance and the effect on our heating bills!”

Bathroom sloping ceiling insulation

With no loft hatch to the roof in the back of the building, but with a ceiling high enough to allow insulated plasterboard to be fixed underneath, this was an appropriate alternative to conventional loft insulation, and easily fitted by the building contractor.

Double/triple glazing

The owners preferred wooden windows, as a natural product and because of the toxic nature of PVC production. The front windows and sliding door were made by a local joiner and fitted as part of the alterations. Standard size, wooden triple glazed windows were chosen for the alterations at the back of the house where new openings could be made.


A south facing conservatory was built. This provides solar gain in Spring and Autumn, bringing warm air into the house.

Solar PV

With a south facing roof it made sense to generate electricity with solar photo-voltaic panels. The feed in tariff is now less generous, but with increasing electricity prices, it can still make sense.

“Our back door was very draughty. This and the uninsulated solid walls meant that in winter, the boiler used to be on most of the time, struggling to reach the temperature on the room thermostat. Now the heating comes on for an hour or so, and the temperature is reached so the boiler goes off. Having a well-insulated house means it keeps the heat in for longer, so the boiler is on much less, and we have noticed the difference in our gas bills.”