Start With the Fabric, Not the Boiler

Older houses were built to manage moisture in a way that modern buildings are not. Solid brick or stone walls, lime mortar, suspended timber floors and open chimneys all allow a certain amount of air movement and evaporation. That is not a fault to be cured; it is the system that has kept the building standing for a century or more. The trick with energy improvements is to work with that system rather than against it. Seal too tightly, insulate the wrong surface, or trap damp where it cannot escape, and you will create problems far more expensive than the bills you were trying to reduce.

A sensible approach is to spend money in layers: cheap, reversible measures first, then insulation where it is safe, and only after that a new boiler or heat pump. That order also happens to be the one that gives the quickest payback.

Draught-Proofing: Small Jobs, Genuine Returns

Draughts in a period property are rarely just about comfort. On a windy day they can account for a surprising share of heat loss, and they are usually the cheapest thing to fix. Work through the house methodically and note where cold air moves.

• Chimneys are the biggest culprits. A chimney balloon or sheep's wool draught excluder in an unused flue is inexpensive and instantly effective. Remove it before lighting a fire, and never block a flue serving an appliance that is still in use.
• Letterboxes, keyholes and cat flaps can be fitted with brush or flap seals for a few pounds each.
• Sash and casement windows respond well to brush or silicone seals fitted into the frame rebate. On historic joinery, ask a joiner to rebate the meeting rails rather than sticking on foam strips, which trap dirt and perish quickly.
• Suspended timber floors are draughty along the boards and at the skirting. Seal gaps with a flexible mastic or slivers of matching timber, and insulate beneath later.

Two cautions. Never block the airbricks that ventilate the sub-floor void — without them, joist ends rot. And never seal up a room containing an open-flued gas fire or a solid fuel stove without providing permanent ventilation, as required by building regulations.

Insulating Without Trapping Damp

Insulation is where good intentions most often go wrong in old buildings. The guiding principle is breathability: moisture must be able to dry inwards or outwards, and the insulation should be no less vapour-permeable than the materials around it.

In the loft, top up to around 270mm using a mineral or natural fibre, but keep the eaves clear. Fit rafter trays or proprietary ventilation trays at the wall plate so air still flows over the insulation into the roof space. If you insulate between rafters to create a warm roof, leave a 50mm ventilated gap above the insulation and use a breathable board such as wood fibre or sheep's wool, not foil-faced foam.

Solid walls are the difficult case. Internal insulation using wood fibre or lime-based boards is usually the safest option for a traditionally built home, provided you accept the loss of a little floor space and detail the junctions carefully. External wall insulation should be considered only after specialist advice, and rarely on a listed facade or in a conservation area without consent. Cavity walls in older properties may be narrow, rubble-filled or partly filled already; have them inspected before anyone drills holes in them.

For suspended ground floors, lift a few boards, fit netting between the joists and lay a breathable insulation such as sheep's wool or wood fibre, keeping the void below ventilated. It is undignified work, but it makes a real difference underfoot.

Windows, Doors and Shutters

Original timber windows are usually worth repairing rather than replacing. A well-maintained sash with new draught seals, a repaired cord and a coat of paint will outperform a cheap replacement and hold its value. Where you need more, secondary glazing fitted to the internal reveal is discreet, reversible and remarkably effective, and it is often acceptable where full double glazing is not.

Do not overlook the soft measures. Heavy lined curtains drawn at dusk, close-fitting timber shutters and a well-fitted curtain pelmet all reduce heat loss and draughts noticeably. For doors, a good draught seal and a heavy curtain over a back door will do more than you might expect.

Heating Controls and Running the System Well

Once the building is tidier, look at how you heat it. Thermostatic radiator valves on every radiator except the one in the room with the main thermostat give you room-by-room control. Zoned or smart controls suit a house with a cold wing or an unused top floor.

If you have a condensing boiler, ask your engineer to set it up properly: a lower flow temperature of around 55–60°C, weather compensation if the boiler supports it, and balanced radiators so every room warms evenly. A boiler that is correctly commissioned can cut gas use without any capital cost. Have it serviced annually, and lag any accessible hot water pipes in unheated spaces.

Resist the temptation to shut off unheated rooms entirely through winter. In an old building, a little background warmth prevents condensation forming on cold walls and in corners, which is how damp and mould take hold.

A Sensible Order of Work

Begin with a survey from someone who understands traditional construction, and check whether your home is listed or in a conservation area before planning anything external. Draught-proof, then insulate where it is safe, then improve controls, then consider the heat source. Phase the work over a few years if you need to, and keep records and photographs of everything you do. Done carefully, these measures will trim your bills, keep the house warmer and leave its character — and its fabric — intact for the next hundred years.