Merton Household Retrofit Guidance
Welcome to Merton Council’s Household Retrofit Guidance.
Here to help! – This tool provides basic guidance on energy efficiency improvements that could help make it easier to keep your home at a comfortable temperature, whilst also making it a healthier place for you and your family to live and reduce your energy bills.
Cold and damp homes contribute to health issues including respiratory infections, allergies, and mould-related illnesses and have a higher condensation risk - keeping your home warm and regularly ventilated with fresh air will help to create a healthier environment.
Why? - In Merton the energy used to heat and power our homes accounts for 44% of the borough’s total greenhouse gas emissions . Merton’s Climate Strategy and Action Plan details the importance of reducing energy demand from our homes to help support our journey towards becoming a net-zero borough by 2050.
This guidance has been produced to help Merton residents understand how they can begin to make energy savings in their home and considers a phased approach to retrofit. This ranges from simple, low-cost energy saving tips through to deep, whole house retrofit measures.
Retrofit and Your Home
What is retrofit?
Essentially, retrofit is about making improvements to your home to make it more energy efficient. This often includes improving the insulation of walls, floors, roofs and lofts and upgrading windows and doors. This may also include upgrading your heating and hot water system and installing energy efficient lighting and white goods in your home. The energy hierarchy can help inform what steps you take to reduce the energy demand of your home.
Remember – the higher the energy efficiency of your home and appliances, the lower your overall energy use is likely to be!
The energy hierarchy outlines three key stages:
- Energy Conservation – Reducing the amount of energy we are using in our homes, primarily through behavioural changes e.g., not leaving appliances on standby and putting on warmer clothing before turning on the heating - small actions which all add up to save energy and money!
- Improving Efficiency – Improving the efficiency of the built fabric of your home (insulated walls, improved air tightness, more efficient windows) and the appliances being used (LED lighting, energy-efficient white goods, running a gas boiler at a lower temperature).
- Meeting any remaining energy demand with renewables and low carbon heating – Once the energy demand in your home has been reduced as much as possible, consider installing low carbon heating (such as air source heat pumps) and renewables (such as solar panels).
Retrofit Ready
You should always prioritise the maintenance of your property prior to beginning any retrofit works as this is the main way to increase both your own comfort and the energy efficiency of the building. Regular maintenance of your home may also provide the perfect opportunity for energy efficiency improvements to be considered e.g., when windows need repairing or replacing. Maintenance of your home ensures that it is ‘retrofit ready’.
Fabric First Approach
A Fabric First approach follows the energy hierarchy previously mentioned. Put simply, this means to improve the fabric, or shell, of a home before installing any technology such as low carbon heating or renewables. This ensures energy demand is reduced to as low as possible so that when technologies such as an air source heat pump are installed, they can run efficiently and cheaply because they are not required to meet as significant a demand.
Whole House Planning
When considering the retrofit of your home, it is important to see your home as a whole system and not a series of disconnected parts – a lot of retrofit measures work together. This means you should think about how the installation of one measure could impact another.
The ‘whole house’ approach helps you decide which retrofit measures to install and in what order. Planning your measures in isolation rather than as a joined-up process risks unforeseen and possibly undesirable outcomes, as well as higher overall costs.
If you have recently installed a new kitchen or bathroom, for example, it would be undesirable to take these out to insulate the walls behind them. Think about how you can incorporate retrofit measures into other home renovation plans - you could save money by doing these at the same time.
A suitably qualified Retrofit Coordinator or Designer can help you in creating a whole house plan which follows the fabric-first approach and ensures that measures are completed in the correct order to suit you and your home.
Planning Considerations
If your home is considered to be of heritage value (i.e., it is a listed building or is located in a conservation area), the retrofit works you can complete may require planning permission.
If your home is in one of Merton’s Conservation Areas (refer to above map), you may need to submit a planning application for any work to the exterior of your property e.g., external wall insulation, new windows, solar panels, air source heat pumps.
If your home is an historic listed building, you will also need to apply for Listed Building Consent if you want to make any changes internally or externally.
Some home retrofit measures (as listed in the fabric measures section of this guidance) are covered under national Permitted Development rights. Permitted Development rights allow for certain building works to be completed without the need to make a planning application. Permitted Development rights do not apply to flats, maisonettes, listed buildings or within some conservation areas.
If you have any planning queries in relation to proposed retrofit works in Merton, please contact Development Management by email: planning@merton.gov.uk
Please note: It is your responsibility to ensure the relevant consents such as Planning Permission and Building Regulations approval are in place.
Retrofit Measures
Below you will find a list of energy saving tips and ‘quick win’ measures to make modest energy savings in your home. This is followed by a list of deeper retrofit measures where more significant energy savings can be made.
Fabric Improvements
Understanding Your Property
Every home is different and there are important characteristics to understand in order to decide which energy reduction measures are suitable for your home. These include: house type (detached, semi-detached, terraced, bungalow), wall construction (solid wall, cavity wall) and property age.
For those living in homes which are not detached, consideration should be given to party walls and whether the outside of your home could be insulated at the same time as your neighbour to make the most of associated costs e.g., scaffolding.
Knowing the wall construction of your home is also important. In Merton this is commonly a solid or cavity brick wall. Solid walls can be insulated internally or externally. New cavity walls will be built with insulation inside the cavity of the wall. However, some older cavity wall houses do not have insulation in this area and could benefit from this.
The Importance of Ventilation
As we spend most of our time inside buildings, ventilation is important to improve indoor air quality by removing potentially harmful pollutants from the air. Ventilation also helps to regulate internal moisture levels produced by breathing, washing, cooking and drying clothes. Finally, ventilation can also help prevent overheating.
In our homes, ventilation is particularly important in high-moisture areas such as kitchens and bathrooms. Using extractor fans and opening windows will help stop moisture from spreading to other areas of the house where the moist air could condense on cold surfaces which may lead to damp.
Drier areas in your home such as bedrooms also need ventilating. If your windows have trickle vents (small channel vents found on the top and side of modern windows), leave these open to help fresh air get around the room.
Fans are available which recover the warmth from any extracted air and return this back into the room – these are called single-room Mechanical Ventilation with Heat Recovery (MVHR) systems. For more extensive retrofit projects, a whole-house MVHR system could be more suitable (see Airtightness and Ventilation section below for more details).
Jargon Busting
Passivhaus – Passivhaus is an energy performance standard and certification for new build dwellings. The standard and certification set rigorous energy efficient design standards to provide high level of occupant comfort using very little energy for heating and cooling.
EnerPHit – EnerPHit is the Passivhaus standard equivalent for building retrofits.
Whole House Plan – A whole-house plan allows for a holistic view of all retrofit measures in a property. This ensures that retrofit measures are being implemented in an order which does not negatively affect thermal performance. A suitably qualified Retrofit Coordinator or Designer will be able to support you in the creation of a plan specific to your home.
Net Zero - Achieving a balance between the carbon emitted into the atmosphere, and the carbon removed from it. This balance will occur when the amount of carbon we add to the atmosphere is no more than the amount removed.
Party Wall – A party wall is a wall shared by two adjoining property owners (e.g., the wall separating semi-detached or terraced houses).
PAS2035 – A code of practice created to ensure that retrofit standards and approaches on housing stock are completed to a consistent standard. It was created in 2015 to try to address a previous lack of consistency across retrofit projects. You can find out more at https://retrofitacademy.org/knowledge/pas-2035/
CO 2 e – This is the abbreviation for ‘carbon dioxide equivalent’. CO2e is a standard unit for measuring carbon footprints. It provides a unified way of comparing the impact of different greenhouse gases on the environment.
EPC – EPC is an abbreviation for Energy Performance Certificate. An EPC is a legally valid document which provides an energy efficiency rating (displayed on an A-G scale) in relation to a property’s running costs. This rating will take into account the potential energy performance of a property (fabric) and its services (heating, lighting, hot water)
Financial Support
Visit our webpages for an up-to-date list of available funding schemes to stay warm and save energy:
You can also explore retrofit options for your home with a free online plan builder from Ecofurb .