The five UK property types:what they mean for retrofit

How is England's housing split by age?

*The survey's modelled mean cost for homes that could be improved to band C, not a quote. Across all homes the mean was £7,480. The survey splits 1965 to 1990 in two, so we show both figures.

Two numbers explain most retrofit decisions in England. About 6.2 million homes have solid walls with no insulation, and about 4.9 million have cavity walls that are still empty.

What should you expect from a home built before 1919?

Victorian and Edwardian terraces, villas and cottages. The Energy Saving Trust says homes built before the 1920s are more likely to have solid walls: a single thickness of brick or stone with no gap. A quick check is the brick pattern. If some bricks are laid end-on, showing their short face, the wall is probably solid.

• Typical starting point: solid walls, often a suspended timber ground floor, and the largest average floor area of any era (110m²). The EPC methodology assumes a suspended timber floor for homes built before 1930 when the construction is not known.
• Only 27% reach EPC band C or better, the lowest of any era.
• Solid walls need internal or external insulation, which is disruptive and must manage moisture. Get specialist advice first.
• Usual order: loft and draught-proofing, then floor insulation where accessible, then carefully specified wall insulation, then heating.

More detail: internal vs external solid wall insulation.

What about interwar homes built between 1919 and 1944?

This is the era of the suburban semi with a bay window. The Energy Saving Trust says homes built after the 1920s probably have cavity walls: two leaves of masonry with a gap between. Many of those cavities were never filled. In the EPC methodology, an unfilled cavity wall from this era is given a U-value (the rate heat passes through) of 1.5 W/m²K, and a filled one 0.7, so filling it roughly halves the heat lost through the walls.

• Typical starting point: cavity walls that may be empty, a loft with some insulation, often replacement double glazing.
• 40% are rated A to C, and 53% sit in band D.
• Usual order: cavity wall insulation after a survey confirms the cavity is suitable, loft top-up to 270mm, draught-proofing, then heating sized to the reduced heat loss.

We walk through the numbers for this era in the 1930s semi worked example.

What is different about post-war homes from 1945 to 1964?

This era includes much of today's social housing: 29% of social rented homes in England were built between 1945 and 1964. Many are cavity-walled like interwar homes, but some post-war homes were not built in brick at all. The Energy Saving Trust notes that some houses have steel or timber frames or prefabricated concrete structures, and that these need advice from a building professional before any wall insulation.

• Typical starting point: smaller homes (90m² on average), usually with cavity walls unless the construction is non-traditional.
• 55% are rated A to C.
• Usual order: confirm the construction type, then cavity fill if suitable, loft, draught-proofing, then heating.

Do homes from 1965 to 1990 still need insulating?

Often, yes. This is the largest group, with 6.65 million homes. Standards tightened through the period, which shows in the EPC methodology's default values: an as-built cavity wall is assumed to reach 1.5 W/m²K up to 1975, 1.0 from 1976 to 1982, and 0.60 from 1983. That means a 1970s home may have an empty cavity, while a late-1980s one probably has some insulation built in.

• Typical starting point: cavity walls with no or only built-in insulation, and loft insulation that may fall short of today's 270mm recommendation.
• About 64% are rated A to C.
• Usual order: check the cavity with a borescope (a small camera through a drilled hole), top up the loft, then heating and controls.

Is a home built after 1990 ready for a heat pump?

Usually closer than any other era. The Energy Saving Trust says houses built from the 1990s onwards generally have wall insulation, and 86% of post-1990 homes are rated A to C. The EPC methodology assumes cavity walls from 1996 to 2002 reach 0.45 W/m²K and those from 2012 onwards 0.28 or better.

• Typical starting point: insulated walls and, in most homes, a gas boiler.
• There is usually less fabric work left to do. The average modelled cost to reach band C falls to £2,447 for 2003 to 2013 homes and £2,031 after 2013.
• Usual order: heating system, controls and flow temperature, then solar and storage if they suit you.

For these homes the big decision is heating. Start with whether a heat pump suits an older or newer home.

How do you use your home's era to plan spending?

1. Find your build date on your EPC, the deeds or a surveyor's report. Extensions can be a different era from the main house, and the EPC treats them separately.
2. Check the wall type by the brick pattern and wall thickness. The Energy Saving Trust says a brick wall 260mm to 350mm thick is likely to be cavity.
3. Fix the easy losses first: loft to 270mm and draughts around doors and windows, keeping deliberate ventilation open.
4. Insulate walls in the way that suits their construction, after a survey.
5. Size any new heating to the improved home, not the old one.

The retrofit planner turns your home's details into a sequenced plan, and our insulation service covers loft, cavity, solid wall and floor work.

Common questions