Energy efficient renovation of a former council house

CONSTRUCTION: Typical semi-detached 1930s council house

KEY FEATURES: Cavity, loft, and underfloor insulation, condensing boiler, wood stove, green roof, double glazing, solar PV



The owners wanted to upgrade the house and make it energy efficient at the same time to reduce their bills.

Energy Performance Certificate

A before and after EPC showed that the improvements had almost tripled the rating from 30 (F) to 85 (B).

Before After
Energy Rating 30 85
Actual gas consumption p.a. 11,000 kWh 6,300 kWh
Actual electricity purchased p.a. 2600 kWh 920 kWh
Carbon emissions p.a. 3 tonnes p.a. 1.5 tonnes


Having cavity walls meant that insulating them was easy and low cost, as was topping up the loft insulation. With timber floors, insulation was also relatively easy to fix under the floorboards.


The gas central heating was from an obsolete and inefficient back boiler unit, which was replaced with a condensing gas boiler. A wood stove with an air supply from under the floor was fitted, thus minimising draughts and providing heat from a renewable source when the central heating wasn’t needed.

Double glazing

The original windows were single glazed and metal framed, and so cold that condensation formed on the frames as well as the glazing. This meant that fitting double glazing made even more of a difference than if they had been wooden framed.

Solar PV

With a south-east facing front roof and room for 12 solar panels, solar PV was an obvious choice. The feed in tariff income from the 2.8 kWp system is enough to cover both gas and electricity bills.

Green roof

The green roof on the workshop helps to sound proof and insulate it. It provides a pleasant view from the house, a habitat for wildlife, and the neighbourhood cats love it as well.

Other possibilities

A porch on the front door and a sun room at the back would reduce cold air coming into the house, and provide solar gain.

“For a total investment of under £10,000, excluding the windows which needed replacing anyway, we now don’t have to spend anything on fuel. The savings are even greater taking into account that I work from home. The most noticeable change is that the house stays warm when the heating is switched off.”