10 ways to improve the insulation of your period home

Ranging from small, inexpensive fixes to more extensive updates, Period Living looks at 10 ways to improve the thermal efficiency of an old home

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1. Eliminate floorboard draughts

Seal up the gaps in your floorboards by caulking under the skirting and inserting draught strips between floorboards.

Cost: from £20 for a 40m roll of draught strip

2. Draught-proof doors and windows

Draught-proof doors and windows as up to 30% of a home’s heat can be lost through these entries. Take care to ensure a level of ventilation is maintained, however, so only block the most noticeable draughts.

Cost: from £6 per door or window

3. Check your loft insulation

Top up your loft insulation to 300mm thickness (a minimum of 270mm is standard). Rockwool is commonly used, but sheep’s wool products, such as Thermafleece, are more efficient and made from a natural material that supports British farming. 10% of a home’s heat can be lost through a loft; this is reduced to just 3% after adding more insulation.

Cost: from £7/m2

4. Insulate floors

Insulate under floors, too. If your home has suspended timber floors, mineral wool can be layered underneath between the joists. This is easy to install if you have a cellar, as the insulation can be fitted and held up by netting or boarding — in other cases floorboards will need to be raised.

Solid floors can be excavated and insulation put below, which is a big job that can have implications on pipework, damp proofing and – of course – existing flooring (thus an average cost is not easy to come by).

Cost: around £100 (dependent on floor area) for a suspended timber floor

5. Improve glazing

Double or secondary glazing can reduce heat loss by up to 70%. If existing single-glazed windows are rotten this warrants replacing with double glazing and there are many companies that specialise in providing this service for period homes.

If the windows are in good condition or should not be replaced due to conservation status, secondary glazing is the best option and offers nearly the same levels of efficiency as double glazing. It will also improve soundproofing while preserving your home’s character. Secondary glazing is available for sash windows and other traditional window types, but some companies can also offer bespoke options for unusual window shapes or styles.

secondary glazing fitting to James Bruges home

CosyHome Company improved the thermal efficiency of the sash windows in James Bruge’s home with special secondary glazing for sash windows

6. Deflect lost heat

Fit enhancers behind your radiators to reflect heat back into the room. This prevents heat loss through the walls and can save 7% on heating bills.

Cost: less than £10 (per radiator)

7. External wall insulation

External wall insulation (EWI) is ideal for rendered or slate-hung walls. It consists of insulation boards such as Celotex (synthetic) or Diffutherm (wood fibre board) glued to the external walls, covered with wire mesh and re-rendered. EWI has no risk of condensation being trapped behind it; protects the wall; and reduces its U-value from 2.0W/m2 to as low as 0.2W/m2, majorly improving warmth.

Cost: £5,000–£9,000 for an average three-bedroom semi

8. Internal wall insulation

If you can’t fit external wall insulation because your home is listed, or has stone walls you don’t want to render, internal wall insulation can be highly effective. The technique is similar to EWI, and insulation boards are glued to internal walls and covered with plasterboard. If done incorrectly, condensation and dry rot can get behind it, so professional guidance is recommended.

Cost: £40–£50 per m2

9. Add curtain lining

Thermally lining your curtains can reduce heat loss by up to 14%. Single glazing has a U-value of 5.5W/m2, but this can be brought down to 1.0W/m2 with thermally lined curtains.

Cost: from £20 per curtain

10. Improve insulation to sloping ceilings

If your first floor (or second floor in a three-storey house) rooms have a sloping part, this is often because plasterboard has been fitted to allow cold air to circulate above and ventilate the rafters. This can lead to phenomenal heat loss if not insulated properly, so fit insulation boards and re-plaster. This can be expensive but makes a big difference to the warmth and thus comfort of a room.

Cost: from £12/m2 including labour


A U-value is a measurement of how quickly heat passes through a surface and is used to indicate the thermal efficiency of various parts of a home’s structure. A U-value shows how much energy (in watts) passes through each square metre — the lower the value, the better the thermal efficiency.

Under Part L of the Building Regulations, maximum U-values have been set for floors, walls, roofs and windows. New building work must adhere to these, but it is also important (for environmental and energy saving reasons) to try and get the lowest possible U-values in your home, whatever its age.

Following all these tips could reduce the heat loss in your home by as much as 80%, but tackling the DIY fixes – such as loft insulation, draught proofing, secondary glazing and radiators – will reduce loss by as much as 40% alone. The result is your home is more comfortable and you save money on your energy bills.

Tips provided by Mukti Mitchell, director of CosyHome Company, specialist in insulation solutions for period properties