How to Keep a Poorly Insulated House Warm
2 October 2026
To keep a poorly insulated house warm, stop uncontrolled draughts first, use curtains and floor coverings to reduce heat loss, keep radiators clear and heat the rooms you use most. These measures can improve comfort quickly, but the lasting solution is to insulate the loft, walls and suspended floors in the right order.
A house that loses heat rapidly may still feel cold when the heating is working properly. Turning the thermostat higher produces more heat, but much of it can escape through the roof, walls, windows, floors and gaps around doors. Finding the main source of heat loss is therefore more useful than continually increasing the boiler temperature.
Quick answer: Close internal doors, seal unwanted gaps around windows and doors, fit thermal curtains, use rugs on cold floors and keep furniture away from radiators. Heat occupied rooms to a comfortable temperature, normally at least 18°C for older people and anyone with a health condition. Do not block air bricks, extractor fans or intentional ventilation. For a permanent improvement, start with loft insulation and then investigate the walls and floor.
Find Out Why the House Feels Cold
A poorly insulated house can have more than one problem. Before buying heaters or replacing radiators, check whether the house is losing heat or failing to produce enough of it.
Common signs include:
Rooms warm up but become cold soon after the heating turns off.
Cold air can be felt around doors, windows or floorboards.
Upstairs rooms are warmer than downstairs rooms.
External walls feel much colder than internal walls.
One room is consistently colder than the rest of the house.
Radiators are hot, but the room remains uncomfortable.
Condensation forms on windows and cold walls.
If every radiator is lukewarm, the problem may be the heating system rather than the building. Check the thermostat, boiler pressure and heating schedule. A heating engineer can inspect the system if it struggles to reach the selected temperature.
1. Stop Unwanted Draughts
Draught proofing is usually the quickest improvement because it prevents warm air from escaping through unnecessary gaps.
Check these areas:
Gaps between doors and frames.
Worn seals around opening windows.
The bottom of external doors.
Unused keyholes and letterboxes.
Gaps around loft hatches.
Cracks where pipes pass through exterior walls.
Gaps between floorboards and around skirting boards.
Unused fireplaces and chimney openings.
Self-adhesive seals can help around opening windows and doors. A brush strip can reduce the gap below an external door, while a covered letterbox helps prevent cold air entering through the front door.
Be careful around chimneys and combustion appliances. An unused chimney may need a removable chimney draught excluder, but it should not be permanently sealed without professional advice. A working fire, stove or open-flued appliance needs suitable ventilation.
2. Use Curtains and Blinds Properly
Windows can create a cold surface even when they are not visibly draughty. Thermal curtains or lined blinds add another layer between the room and the glass.
Open curtains during sunny winter days so sunlight can warm the room. Close them shortly before it becomes dark to hold that heat inside.
For the best result:
Use curtains that cover the full window.
Make sure they reach close to the windowsill or floor.
Close curtains in unused rooms as well as occupied rooms.
Keep the fabric away from portable heaters.
Do not let long curtains hang over a radiator.
Curtains covering a radiator can direct warm air towards the window instead of into the room. Tuck them onto the windowsill or use a shorter length where the radiator is directly below the glass.
3. Improve Single-Glazed Windows
Replacing windows is not always affordable, possible or permitted, particularly in rented, listed or conservation properties. Temporary secondary glazing film can create an insulating air layer over single glazing when fitted tightly.
Removable acrylic secondary glazing is a more durable option. It can be useful where original timber windows must be retained.
Before adding a window covering, repair obvious gaps and damaged seals. Secondary glazing will not solve a large draught passing through a poorly fitting frame.
4. Cover Cold Floors
Bare timber, laminate and tiled floors can make a room feel colder, especially when the house has an uninsulated suspended floor.
Use rugs with non-slip underlay in occupied areas. A thick rug will not perform like proper floor insulation, but it can reduce the cold sensation beneath your feet and limit small draughts through exposed floorboards.
Do not cover floor vents or air bricks. Suspended timber floors need airflow beneath them to control moisture and protect the joists from decay.
5. Keep Internal Doors Closed
Close doors between heated and unheated areas. This prevents warm air moving into hallways, stairwells and spare rooms before occupied rooms become comfortable.
A door curtain can help where an external door opens directly into a living room. It should remain clear of locks, handles and escape routes.
Avoid allowing unused rooms to become extremely cold. Completely unheated rooms can develop condensation and damp, especially when warm, moist air enters from the rest of the house. Use thermostatic radiator valves to maintain a lower background temperature instead of turning every unused radiator off for the entire winter.
6. Get More Heat From Your Radiators
Radiators need free airflow to heat a room effectively. Move sofas, cabinets, beds and drying racks away from them. Even a small gap is better than having furniture pressed directly against the radiator.
Check the radiator temperature while the heating is running:
Cold at the top usually indicates trapped air.
Cold at the bottom can indicate sludge or restricted circulation.
One cold radiator may have a closed or stuck valve.
Radiators warming at different speeds may need balancing.
A fully hot radiator that cannot warm the room may be undersized.
Reflective radiator panels can reduce heat passing into a cold external wall. They are most useful behind radiators fixed to uninsulated outside walls. Ordinary kitchen foil is difficult to fit neatly and can degrade, so use a purpose-made product.
Do not place shelves, wet washing or thick covers over electric heaters. Follow the appliance manufacturer's clearance instructions.
7. Use the Heating Controls Efficiently
Set the heating around your routine rather than heating an empty house to full temperature. Start it early enough for occupied rooms to become comfortable before you use them.
In a poorly insulated property, short bursts of very high heat can produce an uncomfortable cycle. The room becomes hot near the radiator and then cools rapidly when the heating stops. A steady thermostat setting during occupied periods often feels more comfortable.
Thermostatic radiator valves can keep living rooms and bedrooms warmer while maintaining a lower temperature in spare rooms. Do not use the boiler flow temperature control as though it were a room thermostat. It controls the temperature of water circulating through the heating system rather than the desired room temperature.
Could Insulation Funding Make Your Home Warmer?
Check the current Warm Homes Plan, available measures and household eligibility before paying privately for major improvements.
8. Control Condensation Without Making the House Colder
A cold house often develops condensation because warm indoor air meets cold walls and windows. Sealing every opening can make the moisture problem worse.
Use extractor fans while cooking and showering. Keep bathroom and kitchen doors closed until excess moisture has been removed. If possible, dry washing outdoors or use a properly vented dryer.
Ventilate deliberately rather than leaving windows slightly open all day during cold weather. Opening windows more widely for a short period can replace humid air without cooling the walls and furniture as much as continuous ventilation.
Never block:
Air bricks.
Trickle vents needed for the ventilation design.
Extractor fans.
Ventilation openings serving a boiler, fire or stove.
Persistent damp, peeling paint or mould may indicate a leak, failed damp proofing or insufficient ventilation. Heating alone will not correct the underlying fault.
9. Insulate the Loft First
Warm air rises, making an uninsulated loft one of the first areas to investigate. Look for thin, compressed or missing insulation, including gaps around the loft hatch.
Do not push insulation tightly into the roof eaves because the roof space may depend on ventilation at this point. Keep insulation away from unsuitable light fittings and heat-producing equipment.
A professional installer can assess the existing material, required depth, ventilation and any condensation or electrical risks before adding more insulation.
10. Check the Wall Construction
The appropriate wall insulation depends on how the house was built.
Cavity Walls
Some cavity walls can be filled through small holes drilled from outside. The property must be surveyed first because cavity exposure, existing damp, wall condition and location can affect suitability.
Solid Walls
Solid walls can be insulated internally or externally. Internal insulation reduces the room size slightly and requires careful detailing around windows, floors and sockets. External insulation changes the outside appearance and may require planning or conservation approval.
Solid wall insulation should be designed as a complete system. Poor detailing can create cold bridges or trap moisture within the building fabric.
11. Consider Underfloor Insulation
Suspended timber floors often feel draughty because cold air circulates in the void below. Insulation can be installed between the joists, provided ventilation beneath the floor is maintained.
Concrete floors require a different approach and may be more practical to insulate during a wider renovation. An installer should identify the floor construction before recommending work.
12. Check Whether the Radiators Are Large Enough
Poorly insulated rooms need a higher heat output than modern insulated rooms of the same size. A small radiator may become completely hot but still fail to replace the heat escaping through the building.
A heating engineer can perform a room-by-room heat loss calculation. This considers:
Room dimensions and ceiling height.
External wall area.
Window size and glazing.
Roof and floor construction.
Insulation levels.
The indoor and outdoor design temperatures.
Use the calculated heat requirement to choose the radiator output. Matching only the physical dimensions of the old radiator can leave the room underheated. Our guide explaining how radiators heat a room covers airflow, cold spots and system balancing in more detail.
How Much Do the Main Improvements Cost?
The following figures are based on InstantCost's 2026 UK insulation and heating data. Final prices depend on property size, access, region and the condition of the existing building.
Improvement | Typical UK cost or funded value | When it may help |
|---|---|---|
Loft insulation | £400 to £1,200 | Loft insulation is missing, thin or badly disturbed |
Cavity wall insulation | £600 to £2,000 | The home has suitable unfilled cavity walls |
Solid wall insulation | £6,000 to £12,000 | The property has cold, uninsulated solid walls |
Boiler service | £70 to £120 | The boiler is due for its annual inspection |
Professional radiator balancing | £100 to £250 | Some radiators warm much faster than others |
Heating engineer heat loss assessment | £80 to £150 | Rooms remain cold despite fully hot radiators |
Radiator installation | £200 to £450 per radiator | The existing radiator has insufficient output |
Heating system power flush | £350 to £650 | Several radiators have persistent cold lower sections |
Eligible households may receive funded insulation or heating improvements. Do not assume a grant covers work until the property has been assessed and approval has been confirmed.
What Renters Can Do
If you rent the property, report defective heating, serious draughts, damp and mould to the landlord in writing. Include photographs, room temperatures and dates where possible.
Ask for permission before making permanent alterations, installing secondary glazing panels or changing heating equipment. Removable draught seals, thermal curtains and rugs are normally easier options, but they must not damage the property or block required ventilation.
Private landlords may need to give consent before grant-funded insulation can be installed. Some energy-efficiency schemes include rented homes when both the tenant and landlord meet the relevant conditions.
Safety Guide for Heating a Cold House
The UK government's cold-weather guidance recommends heating rooms you use regularly to at least 18°C, particularly if you are aged 65 or over, have reduced mobility or live with a long-term health condition. Read the official keeping warm and well guidance if cold conditions may affect your health.
Never use a barbecue, patio heater or camping stove to heat an indoor room. These appliances can cause fires and produce carbon monoxide. Keep portable electric heaters upright on a stable surface and away from curtains, bedding, clothes and furniture.
Do not use an extension lead for a high-power portable heater unless the heater manufacturer specifically permits it and the lead is correctly rated. Plugging several heating appliances into one extension can overheat the socket or cable.
Homes with fuel-burning appliances should have suitable carbon monoxide alarms. Any gas boiler repair or internal gas work must be completed by a Gas Safe registered engineer.
Common Mistakes
Blocking Every Vent
Draught proofing should close accidental gaps, not required ventilation. Blocking air bricks, chimney ventilation or extractor fans can contribute to damp and create serious risks around fuel-burning appliances.
Putting Furniture in Front of Radiators
A sofa directly against a radiator absorbs and traps heat. Leave room for cooler air to enter below the radiator and warm air to rise into the room.
Turning Off Heating in Every Unused Room
A completely cold room can develop condensation. Use a lower background temperature instead, especially where the room shares walls with heated areas.
Buying a Larger Heater Before Finding the Heat Loss
A larger heater can increase energy use without fixing draughts or missing insulation. Find the cold spots first and address the cheapest sources of heat loss.
Covering Radiators With Curtains
Long curtains can trap warm air beside the window. Keep the radiator exposed to the room while closing the curtain across the glass.
Insulating Over Damp
Insulation should not be used to hide leaking walls, penetrating damp or damaged timber. Find and repair the moisture source before covering the area.
Frequently Asked Questions
What is the quickest way to make a cold house warmer?
Close internal doors, seal obvious gaps around windows and external doors, close lined curtains before dark and move furniture away from radiators. These steps can improve comfort without major building work.
Should I leave the heating on constantly in a poorly insulated house?
Usually, it is better to use a thermostat and heating schedule based on when the house is occupied. Leaving the heating on continuously can waste energy because the building loses heat rapidly. Vulnerable residents may need a steadier minimum temperature for health reasons.
Why is my house still cold when the radiators are hot?
The radiators may be too small for the room's heat loss, or heat may be escaping through the roof, walls, floor, windows and draughts. A room-by-room heat loss assessment can show whether insulation or larger radiators should be prioritised.
Do thick curtains really keep a house warmer?
Lined or thermal curtains reduce the cold effect of windows and slow heat loss. They work best when closed before dark and positioned so they do not cover radiators.
Is it safe to block a draughty air vent?
No. Do not block a vent without knowing its purpose. It may ventilate a suspended floor, control moisture or provide combustion air for a boiler, fire or stove.
Which insulation should I install first?
Loft insulation is often the first area to investigate because it is usually more straightforward than wall or floor insulation. The correct order still depends on the property's construction, existing insulation, damp condition and main source of heat loss.
Check the Cost of Improving Your Heating
Compare current UK prices for boiler servicing, heating repairs, radiators and complete boiler replacement.