Improving the energy efficiency of an older block makes homes more comfortable while helping to reduce carbon emissions. But retrofitting a historic building requires a different approach versus upgrading a modern block.
Traditional buildings were constructed using materials and methods designed to manage heat, air and moisture in particular ways. Adding modern insulation or making a building more airtight without understanding how it performs can create unintended problems.
For managing agents, Resident Management Companies and Right to Manage directors and flat owners, the aim should be to improve energy performance without damaging what makes the building special, and without causing more problems than they solve.
Why Historic Buildings Need a Different Approach
Many traditionally constructed buildings use materials such as brick, stone, timber and lime mortar. These can absorb and release moisture rather than relying on the sealed construction commonly found in newer buildings. Any retrofit should start with understanding the building rather than choosing a particular product based on modern assumptions.
Historic England recommends a “whole building approach”, considering the building’s construction, condition, occupants and environment. In a block of flats, this joined-up thinking is particularly important. Alterations inside one property can potentially interact with communal walls, roofs, ventilation systems or other parts of the building.
Start With Maintenance
Before spending money on insulation or new technology, it’s best to deal with existing defects first. A leaking roof, blocked gutter, damaged pointing or faulty window can make a building colder and damper. Adding insulation without solving the underlying problem could trap moisture and make things worse.
For blocks, this makes planned maintenance an important part of energy efficiency. Roof inspections, drainage maintenance, window repairs and attention to cracks or defective finishes can improve performance while protecting the building. Sometimes the most effective first step towards a warmer historic block is simply properly maintaining what is already there.
Insulation Needs Careful Thought
Roof or loft insulation may offer opportunities in some blocks, but wall insulation can be considerably more complex. Insulation reduces heat loss, but it shouldn’t be assumed to be suitable for every part of a historic building.
Internal insulation changes the temperature of the original wall behind it. If the system is poorly designed, moisture can become trapped and condensation can build up where residents cannot see it. This can contribute to condensation, mould, timber decay and corrosion.
External wall insulation can present different challenges. It may alter historic façades, architectural details, window reveals or roof junctions and therefore may be unsuitable. Insulation should be treated as a building-specific project rather than a standard upgrade.
Secondary Glazing Can Offer a Practical Alternative
Windows are often one of the first areas up for consideration when residents want to improve comfort. For listed buildings, simply replacing original windows with modern double-glazed units may not be acceptable. Historic windows can make an important contribution to the character of the building, and replacement may require Listed Building Consent.
Secondary glazing can be a great alternative. Installed internally, a carefully designed secondary window allows the original window to remain in place while helping to reduce heat loss and draughts. This approach can also improve sound insulation and sometimes provides better energy-efficiency improvement than double glazing.
Secondary glazing does not usually require Listed Building Consent, although there are exceptions. Owners should always check with the local planning authority before planning any works.
Don’t Improve Airtightness and Forget Ventilation
One of the biggest retrofit mistakes is focusing on keeping heat in without considering how moisture gets out. Everyday activities such as cooking, showering and drying clothes generate moisture. Traditionally constructed buildings manage some of this through their materials and natural air movement.
Draught-proofing, insulation and improved windows can reduce that air movement, and without an appropriate ventilation strategy, humidity may rise. This is particularly important in flats, where kitchens and bathrooms may have limited external walls or windows.
The objective is not to make a historic property as airtight as possible, but to control unwanted heat loss while maintaining enough ventilation for the building and its occupants.
Beware of Trapped Moisture
Moisture is one of the biggest risks associated with poorly planned historic retrofits. Traditional walls are often designed to absorb moisture and release it again when conditions allow. Covering them with unsuitable impermeable materials can interfere with that process. Moisture may then accumulate behind insulation or finishes, potentially causing hidden decay.
This can be particularly serious around timber joist ends and other structural elements built into external walls. A retrofit that lowers heating bills but causes expensive and disruptive structural damage is clearly a false economy.
What About Listed Building Consent?
Energy efficiency and heritage protection do not have to work against each other. Historic England’s updated guidance recognises that historic buildings need to contribute to a lower-carbon future while retaining their significance. However, some changes will require permission:
- For listed blocks, owners should speak to the managing agent, freeholder, RMC or RTM company before altering windows, walls or other parts of the property. The lease may contain restrictions even where planning consent is not required.
- Where works could affect the building’s special architectural or historic character, advice should also be sought from the local authority’s conservation team.
Planning permission, Listed Building Consent and Building Regulations are separate requirements, so one approval should not be assumed to cover another.
Think About the Whole Block
Energy efficiency in flats can become complicated when improvements are considered property by property. One resident may install secondary glazing while another replaces heating equipment. Meanwhile, the roof, communal windows or shared heating system may offer greater opportunities for improvement.
RMC and RTM directors and managing agents can therefore benefit from looking at energy efficiency as part of long-term maintenance planning. If roof works are already scheduled, could appropriate insulation improvements be considered at the same time? If communal windows need refurbishment, could draught reduction form part of the specification? Coordinating improvements with planned major works may reduce disruption and help the block achieve better value from money already being spent.
A Sensitive Approach Can Deliver Results
Making a historic block more energy efficient does not necessarily mean transforming it into a modern building. Often, the best results come from a series of carefully chosen measures: good maintenance, heating controls, appropriate draught reduction, sensitive window improvements, suitable insulation and effective ventilation.
The key is understanding how those measures work together. Specialist surveyors, conservation professionals and retrofit experts with experience of traditional buildings can help boards identify solutions suited to the particular property.
With careful planning, appropriate materials and a whole-building approach, improving energy performance and protecting heritage can go hand in hand.
