Zero Carbon Retrofit – Options, Advantages and Drawbacks
Achieving net zero carbon housing by 2050 will transform most of the UK’s housing stock. Currently, only a tiny fraction of homes meet the net zero standard. For local authorities and housing associations this means a massive upgrade programme.
The options chosen will have a major impact on the overall cost and the upheaval and inconvenience experienced by residents.
The goal is to insulate every property to a level where the energy it needs to consume can be provided entirely from renewable sources. What this means in practice will vary from property to property depending on the age and construction.
Net carbon zero calls for a whole house approach. It’s unlikely that one retrofit option on its own will upgrade a home to the required level of energy efficiency.
A great deal of heat loss occurs through walls – particularly solid walls and those with uninsulated cavities. The choices are to apply insulation internally, externally or within the cavity (if there is one).
Injecting insulating material into wall cavities is generally straightforward and cost-effective. Care must be taken to ensure external faces are waterproof to avoid creating a moisture bridge between external and internal surfaces.
Applying insulating materials to the internal faces of walls will reduce room sizes (materials can be up to 100mm thick). This can sometimes be easier than external treatments but is more disruptive for residents. Switches, wiring and radiators may have to be relocated. Making sure there is an airtight layer is equally important.
External cladding is an effective method. The biggest potential drawback may be that the cladding can alter the identity of homes and neighbourhoods, which may not be acceptable to planners.
Adding insulation to external or internal wall surfaces will increase the depth of door and window reveals.
Suitable treatments depend on whether floors are solid or suspended. For suspended floors, you can lift floorboards to lay insulation between joists or spray insulation into the void beneath the floor. It’s essential to seal gaps between floorboards and skirting to prevent draughts.
Rigid insulating materials can be laid over a solid concrete floor so long as this doesn’t contravene building regulations relating to room height.
Insulating Roof Spaces
This is usually a straightforward case of installing upgraded loft insulation. Boarding out loft spaces for storage may no longer be an option, which can call for careful communication with residents.
Doors and Windows
Triple glazing is usually needed to achieve the required level of thermal insulation. Many homes will also need upgraded front and rear doors. These operations are fairly straightforward but will have to be planned on a massive scale.
Low Carbon Heating
Heat pumps (either for individual properties or area-wide) will gradually replace gas boilers. In most cases, thermal insulation upgrades will be needed for a heat pump to keep a home acceptably warm. Heat pumps won’t provide the rapid burst of power that you get from a gas boiler so residents will have to learn to use their heating systems differently. Many homes will also need hot water storage tanks to be installed if the heat pump is replacing a combi boiler.
This is just a brief summary of the options available. There are many more factors to take into account. Osborne is responding to the net zero challenge by actively forming partnerships that can deliver a fully managed zero carbon retrofit programme to local authorities and housing associations.