The Plan

Nigel and Marta moved to Birmingham from Nottingham in 2017 after buying a home that is typical of many suburban areas of Birmingham. Both were committed to making the home as low carbon as possible, and had previously been involved in the Meadows eco-neighbourhood in Nottingham. They started by improving the fabric of the building, with additional insulation to the walls, roof and floor; adding additional glazing, mechanical ventilation with heat recovery, and solar panels. These measures have reduced the home’s carbon dioxide emissions per square metre by 51%. The measures they have adopted could be used on thousands of post-war suburban homes in Birmingham and beyond. Nigel and Marta’s home is now warmer and more comfortable with better air quality, and their fuel bills are lower.

The home was built in the 1950s as a four-bedroomed end terrace, with a floor area of 112 square metres. When Nigel and Marta bought the home, it already had cavity wall insulation and double glazing, as most similar homes will already have.

The Floor

The downstairs solid floor had been built on hardcore using an unusual material – ‘red ash’ waste from a power station . This is no longer acceptable practice as red ash expands and attacks concrete when it gets wet. All the downstairs floors therefore needed to be replaced. This meant that Nigel and Marta could have underfloor heating for the ground floor rather than radiators, and also that they also added extra insulation to the floor, below the underfloor heating pipework. Many people overlook the fact that heat can escape from a house through the floor. While the walls and roof are the most obvious places for heat to escape, heat can transfer downwards as well as upwards, escaping to the ground or to a cellar below. Floor insulation, either by insulating below the floor in the cellar, or by replacing a solid floor and including a layer of insulation, can be a very effective energy saving measure.

Insulation

Although the home already had cavity wall insulation, loft insulation and double glazing, they had experienced the transformation achieved by external wall insulation added to their Nottingham home. This improves insulation, disguises the appearance of tired brickwork and eliminates many of the thermal bridges in the building, which allow heat to escape. A thermal bridge is a an area or component of a house which has lower thermal insulation than the surrounding materials, creating a path of least resistance through which heat can escape. It was to reduce heat loss and prevent thermal bridging that Nigel and Marta decided to have external wall insulation, even though the home already had cavity wall insulation.

Loft extensions are one of the most popular ways for people to increase the living space in their home. Converting the loft was also a chance for Nigel and Marta to add extra insulation to the roof. Along with external wall insulation and triple glazing the new windows, roof insulation helped to complete the thermal blanket around the whole building.

Ventilation

Most homes in the UK do not have adequate ventilation. There is a difference between draughts and ventilation. Draughts are unwanted, uncontrolled movements of air. Ventilation is planned and controlled movement of air, to ensure air quality. Lack of ventilation leads to poor air quality, and exacerbates problems of condensation and damp leading to mould – all caused by excessive moisture production in the home and inadequate heating. Nigel and Marta decided to add more ventilation to their home. This is a very good move when adding insulation, to ensure there are enough air changes to ensure good air quality and avoid either condensation and damp in winter, or overheating in summer. They went for a mechanical ventilation with heat recovery system (MVHR) which exchanges heat from the stale exhaust air with the cold fresh air that it draws in from outside, so that the exhaust air is cooled and the incoming fresh air is warmed. This uses a very small amount of energy to pump a continuous, silent, constant background ventilation that retains the heat that is used to keep the home warm.

Heating

The home already had a condensing gas boiler and basic heating controls but a new condensing gas boiler was installed with additional smart heating controls to supply the 3 zones of underfloor heating and the 3 shower/bath rooms.

Solar Panels

Low energy LED lighting has been fitted throughout the home – to make sure precious electricity is not wasted. 16 Solar electricity (photovoltaic) panels were installed, enough to supply almost a quarter as much again as the home’s annual electricity requirement. However most of this is during the summer when consumption is lowest and generation is highest. During the nights and especially during the other 3 seasons, because they work long hours and from home, they actually import three quarters of their consumption from the grid. So they are currently investigating using batteries to supply their electricity, and only draw from the grid in the early hours of the morning when it is cheapest.

Nigel and Marta are currently working with researchers from the University of Birmingham to see if a ground source heat pump could provide space heating to theirs and neighbouring homes.

Thermal Imaging Survey

After the work was complete, Nigel and Marta commissioned a thermal imaging survey. This showed how effective the insulation had been in reducing heat loss. It also showed some additional areas that needed insulating, to block cold bridges, including the roof of a bay window, and also the walls below the damp-proof course.

After all the work was complete, Nigel and Marta commissioned a thermographic survey. The thermal images showed:

The external wall insulation was successfully preventing heat loss from the home
The triple glazed windows showed less heat loss than the neighbour’s insulated cavity walls in the rest of the building
There were, as expected, cold bridges below the damp-proof course and above the downstairs bay window. Nigel and Marta are now considering insulating these areas.

Nigel and Marta are now working with other local residents to set up Acocks Greener, a community group that will help reduce Acocks Green’s carbon dioxide emissions as a neighbourhood.

Conclusions

What Nigel and Marta have done with their home could be copied by others with post-war homes, including:

External wall insulation is more expensive than cavity wall insulation but gives better heat loss prevention – this is particularly important if we are to reduce carbon emissions due to gas-fired central heating or even to move beyond gas for heating, as heat pumps need very high levels of insulation
Most homes are under-ventilated; mechanical ventilation with heat recovery gives excellent air quality with low heat loss and running costs
Under-floor insulation should not be overlooked as it gives additional heat loss prevention over and above wall and roof insulation.

The West Midlands Combined Authority and many local and parish councils are publishing exciting and ambitious plans to tackle the climate emergency. What Nigel and Marta have done with their home shows us the scale of the challenge we face to make our homes low carbon, but Nigel and Marta have also shown us an exemplar that can be replicated to many post-war suburban homes.

(for www.energyconfidence.co.uk only) If you need help with making your home or business low-carbon, then please take a look at my energy saving advice packages https://www.energyconfidence.co.uk/pricing

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Notes not for publication

Assumes floor area after loft extension = 165 m2

CO2 emissions before = 11,223 kWh gas (epc) = 2063 kg, 5200 kWh electricity (epc) = 1329 kg 112 m2; 147 kWh/m2 (epc) = 3392 kg co2 = 30.3 kg/m2

CO2 emissions after = 9,694 kWh gas = 1782 kg co2; 1957 kWh electricity = 500 kg co2, 165 m2 ; = 2457 kg co2 = 14.9 kg/m2

27.5% reduction in total CO2
51% reduction in co2 per square metre