Performance

The unsexy upgrades that make every other system work harder.

Heat pumps love a well-insulated house. Air conditioning loves a shaded window. Smart controls love a thermostat in the right room. The fabric decisions almost no one writes about decide everything else.

The fabric of a comfortable home.

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the house holding its warmth against a cold morning; January, low winter sun. The frost is holding on the north wall; inside, the house has kept its warmth since dawn.

The fabric ladder

Performance is not a product decision. It is an order of works.

Every performance question sits on one of the rungs below. Fixing further down the ladder makes everything above it smaller, cheaper and gentler; skipping rungs is what turns a retrofit into a rolling programme of regret.

  1. 01
    Draught-proof

    Seal the obvious leaks first. A quiet afternoon with the right brush strips changes the felt temperature of the house.

  2. 02
    Insulate the roof

    The cheapest, highest-return upgrade in almost every British home. Loft first, always.

  3. 03
    Address the walls

    Cavity fill where suitable; internal or external solid-wall where it isn't. The single biggest fabric decision most homes will make.

  4. 04
    Fix the glazing

    Better glass, better frames, better seals. Or secondary glazing done properly on a listed house.

  5. 05
    Shade the summer

    External shutters, awnings and reflective film. The performance decision that used to be optional and is now a design condition.

A pound spent on insulation almost always pays back faster than a pound spent on a fancier boiler. A properly shaded window can save more energy than the most efficient AC. The fabric of your home is the cheapest, longest-lasting upgrade you'll ever make.

How performance works

Find the losses

Find the losses

Most British homes lose heat through the roof, the walls, the floor and the gaps round windows and doors. A thermal image or even a careful walk through on a cold morning shows where the warmth is going.

Close the envelope

Loft insulation, cavity fill where suitable, draught-proofing, and better glazing slow the loss to a fraction of where it began. Each upgrade compounds the next.

Verify, then size systems to suit

With the fabric improved, the heating and cooling can be smaller, gentler and cheaper to run. The order matters: shrink demand first, then specify the system.

A modernist interior in limestone and oak, in architectural daylight.
Performance

A pound spent on insulation almost always pays back faster than a pound spent on a fancier boiler.

The promise

The fabric of a comfortable home.

Inside this category

Where to start.

Tools, not brochures

Decide with data.

Find out where your home is leaking comfort and money.

Evidence apparatus
Last reviewed
4 July 2026
Evidence quality
High· Every performance recommendation on this pillar rests on the Building Regulations, PAS 2035 retrofit standard and the ECO4 evaluation record.
Primary sources

Pillar-level evidence is reviewed each quarter; individual pages carry their own last-reviewed date.