A Simple Guide to Keeping More Heat Inside Your Home
When you heat your home, some of that heat eventually escapes.
It can leave through the roof, walls, floors, windows and doors. Meanwhile, cold outside air can enter through gaps and openings.
As a result, your heating system has to replace the heat that is being lost.
Insulation helps slow this process.
However, every property is different. An older stone house, a Victorian terrace and a modern flat may all lose heat in very different ways.
So, before deciding what insulation to install, it helps to understand where your home is losing heat and why.
Why Does Heat Leave a Building?
Heat naturally moves from warmer areas towards colder ones.
During winter, your home is usually warmer than the air outside. Therefore, heat continually moves through the building towards the colder surroundings.
The greater the difference between the indoor and outdoor temperature, the greater the potential for heat loss.
For example, keeping a home at 20°C when it is 15°C outside requires much less heating than maintaining the same indoor temperature when it is -5°C outside.
That is one reason heating costs can rise sharply during cold weather.
Where Does Heat Escape?
Heat can leave a property in several ways.
Common areas include:
- Roofs and lofts
- External walls
- Floors
- Windows
- External doors
- Gaps around the building
- Areas where different parts of the building meet
However, there is no fixed percentage of heat loss that applies to every home.
You may see claims such as a certain percentage being lost through the roof, walls or windows.
These figures can be useful as broad examples. However, the actual amount depends on the property.
For example, heat loss can be affected by:
- Building size
- Age
- Construction
- Insulation
- Window area
- Number of outside walls
- Indoor temperature
- Outdoor temperature
- Wind exposure
- Ventilation
- Draughts
Therefore, it is better to understand your building than rely on one general percentage.
Heat Loss Through the Roof
Warm air often rises within a room, but heat loss through a roof is not simply caused by heat rising.
Heat can pass through ceilings and roof structures whenever there is a temperature difference between the inside and outside.
If a loft has little or no insulation, this heat can escape relatively easily.
Adding suitable loft insulation creates a layer that slows the movement of heat.
As a result, the rooms below can stay warmer for longer.
Loft Insulation
Loft insulation is often one of the simpler improvements in a property with an accessible loft.
Insulation is commonly installed between and over the ceiling joists.
However, the correct approach depends on how the roof space is designed.
For example, some lofts contain:
- Water tanks
- Pipework
- Electrical cables
- Recessed lighting
- Ventilation openings
- Boarding
- Heating equipment
Therefore, insulation should not simply be pushed into every available gap.
Ventilation may need to remain clear, while tanks and pipes may also need protection against freezing.
If the loft has been converted into a room, the insulation arrangement will be different again.
So, understand the roof construction before deciding what work is needed.
Don’t Forget the Loft Hatch
A well-insulated loft can still have a poorly insulated hatch.
Because the hatch forms part of the ceiling, heat can also pass through it.
In addition, gaps around the edges may allow unwanted air movement.
Therefore, it can be worth checking whether the loft hatch is:
- Properly fitted
- Draught proofed where appropriate
- Insulated
- Easy to close securely
It is a small part of the building, but it can easily be overlooked.
Heat Loss Through Walls
External walls make up a large part of many buildings.
Therefore, their construction can have a major effect on how quickly a property loses heat.
However, not all walls are built in the same way.
UK properties may have:
- Cavity walls
- Solid brick walls
- Stone walls
- Timber-frame walls
- Modern insulated wall systems
Before considering wall insulation, first find out what type of walls you actually have.
What Is a Cavity Wall?
A cavity wall normally has two separate wall layers with a gap between them.
In suitable properties, insulation can sometimes be added to this cavity.
This reduces the rate at which heat passes through the wall.
However, cavity-wall insulation is not automatically suitable for every cavity-wall property.
Factors such as the condition of the walls, cavity construction and exposure to wind-driven rain can matter.
Therefore, suitability should be checked before work begins.
What Is a Solid Wall?
Many older properties have solid external walls rather than cavity walls.
These may be built from brick, stone or other materials.
Because there is no cavity to fill, improving their insulation normally requires a different approach.
The two main options are:
Internal Wall Insulation
Insulation is added to the inside face of an external wall.
External Wall Insulation
Insulation is added to the outside of the building and then covered with a suitable finish.
Both can reduce heat loss.
However, both are significant building improvements and need careful planning.
Internal Wall Insulation
Internal wall insulation can improve the thermal performance of a solid wall.
However, it also changes the inside of the room.
Depending on the system, it may affect:
- Room size
- Skirting boards
- Electrical sockets
- Radiators
- Window reveals
- Doors
- Existing finishes
Moisture also needs careful consideration.
Therefore, internal wall insulation is not simply a matter of attaching insulation boards to a wall.
The whole wall needs to work properly after the improvement.
External Wall Insulation
External wall insulation wraps insulation around the outside of the property.
This can reduce heat loss without taking space from inside rooms.
It may also change the appearance of the building.
Therefore, factors such as planning requirements, boundaries, roof edges, window details and external finishes may need consideration.
Again, moisture needs to be managed properly.
A suitable system should work with the building rather than simply covering it.
Older Buildings Need Particular Care
Older buildings were not necessarily designed to behave like modern homes.
Some traditional walls manage moisture differently from modern cavity-wall construction.
Therefore, adding unsuitable materials can sometimes create problems rather than solve them.
For example, changing how moisture moves through a wall may increase the risk of damp if the whole construction has not been considered.
This does not mean older homes cannot be insulated.
Instead, it means:
The insulation should suit the building.
This is especially important with older stone and solid-wall properties.
Heat Loss Through Floors
Floors can also lose heat.
However, the amount and the best solution depend on the type of floor.
Two common types are:
Suspended Floors
Floorboards or other flooring sit above a ventilated space.
Solid Floors
The floor is built directly onto a solid base.
These need different insulation approaches.
Suspended Timber Floors
Many older homes have suspended timber floors.
Cold air may circulate underneath the floor as part of the building’s ventilation design.
Insulation can sometimes be installed beneath or between the floor joists to reduce heat loss.
However, the ventilation beneath the floor may still be essential.
Blocking air bricks or other designed ventilation can increase the risk of moisture and timber problems.
Therefore:
Insulate the floor without blocking the ventilation it needs.
Solid Floors
Solid floors can also be insulated, although the work may be more involved.
Depending on the property, insulation might be added above the existing floor or as part of a replacement floor.
However, this can affect:
- Floor height
- Doors
- Skirting
- Kitchen units
- Stairs
- Other adjoining floors
Therefore, solid-floor insulation may make most sense when other major work is already being carried out.
Windows and Heat Loss
Windows usually insulate less effectively than a well-insulated wall.
However, that does not automatically mean every window needs replacing.
Heat can be lost through:
- The glass
- Frames
- Gaps
- Failed seals
- Poor installation
Therefore, first identify the problem.
A sound double-glazed window with a damaged seal around the frame may need a relatively simple repair rather than complete replacement.
Single, Double and Triple Glazing
Single glazing has one pane of glass.
Double glazing uses two panes separated by a sealed gap, while triple glazing uses three.
The extra layers can reduce heat transfer.
However, the overall performance of a window also depends on the frame, glazing specification, installation and seals.
Therefore:
More panes do not tell you everything about a window’s performance.
Good installation matters too.
Doors and Heat Loss
External doors can lose heat through both the door itself and gaps around it.
So, check:
- Door seals
- Letterboxes
- Keyholes
- Thresholds
- Gaps around the frame
Sometimes simple draught proofing can improve comfort considerably.
However, if the door itself performs poorly, replacement may eventually be worth considering.
Again, start with the problem before deciding on the solution.
What Is Thermal Bridging?
Insulation is most effective when it forms a good, continuous layer around the heated part of a building.
However, some parts of the structure can allow heat to pass through more easily.
These areas are often called thermal bridges.
They can occur around:
- Window openings
- Door openings
- Wall and floor junctions
- Wall and roof junctions
- Structural elements
- Gaps in insulation
A thermal bridge can create a colder surface inside the home.
In some cases, this may also increase the risk of surface condensation.
Therefore, insulation is not only about how much material is installed.
How well the insulation joins together matters too.
What Is a U-Value?
When looking at insulation, you may come across the term U-value.
A U-value describes how readily heat passes through part of a building, such as a wall, roof, floor or window.
It is normally shown as:
W/m²K
You do not need to memorise the technical detail.
The main point is:
A lower U-value means less heat passes through.
For example, a well-insulated wall will generally have a lower U-value than the same type of wall without insulation.
However, U-values should be compared in context because different parts of a building perform differently.
What Is an R-Value?
You may also see R-value, particularly when looking at insulation products.
R-value describes resistance to heat flow.
Unlike U-value:
A higher R-value means greater resistance to heat flow.
So, as a simple reminder:
U-value → lower is better
R-value → higher is better
However, good insulation still depends on correct installation.
A high-performance product will not perform as intended if it is badly fitted or contains large gaps.
Insulation Needs to Be Continuous
Imagine wearing a thick winter coat with several large holes in it.
The material itself may be excellent, but the gaps reduce its effectiveness.
Insulation works in a similar way.
Gaps, poor joints and missing sections can create easier routes for heat to escape.
Therefore, the quality of installation can be just as important as the insulation material itself.
Insulation and Moisture Need to Work Together
A home contains moisture.
Cooking, washing, showering, drying clothes and breathing all add water vapour to the indoor air.
Meanwhile, the building itself may also contain or absorb moisture.
Changing the insulation can change:
- Surface temperatures
- Air movement
- Where condensation may occur
- How parts of the building dry
Therefore, insulation and moisture should be considered together.
This becomes particularly important when making major changes to older properties.
Insulation Is Not the Same as Draught Proofing
These two ideas are closely related, but they are not the same.
Insulation slows heat passing through materials.
Draught proofing reduces unwanted air movement through gaps.
A wall can be well insulated but still have a draught around a nearby window.
Likewise, a room can have very little draught but still lose heat through poorly insulated walls.
Both matter.
However, because ventilation also matters, we cover air movement separately.
Learn more about Draught Proofing and Ventilation →
More Insulation Is Not Always the First Answer
If a room feels cold, it is tempting to assume it needs more insulation.
However, the cause could be something else.
For example:
- A heating control may be set incorrectly
- A radiator may not be working properly
- A window may have a damaged seal
- There may be a strong draught
- The room may have a large amount of external wall
- The heating system may not provide enough heat
Therefore, investigate before spending money.
Sometimes the solution is insulation.
Sometimes it isn’t.
How Can You Find Heat Loss?
You can start with simple observations.
Walk around your home and look for:
- Cold areas
- Draughts
- Uninsulated loft spaces
- Poorly fitting doors
- Damaged window seals
- Cold floors
- Areas of condensation
Your energy use can provide clues too.
For example, if a home needs a large amount of heating but cools very quickly once the heating stops, heat loss may be significant.
However, identifying the exact cause may require a more detailed assessment.
Thermal Imaging
A thermal camera can show differences in surface temperature.
This can help reveal possible areas of:
- Missing insulation
- Thermal bridging
- Heat loss
- Air leakage
However, thermal images need to be interpreted carefully.
Weather, sunlight, heating conditions and surface materials can all affect what the camera shows.
Therefore, a bright area on an image does not automatically prove that a particular repair is required.
Thermal imaging is best used as evidence to investigate, rather than as a diagnosis by itself.
Should You Insulate Everything at Once?
Not necessarily.
It can be better to understand the whole property first and then decide which improvements offer the greatest benefit.
For example, one home may have almost no loft insulation but reasonable walls.
Another may already have a well-insulated loft but very poor solid walls.
Their priorities would be different.
So, rather than following a standard shopping list, ask:
Where is my home losing heat most easily?
Then consider the practical and financial options.
Think About Payback
Insulation can reduce energy use, but different measures have very different costs.
A simple improvement may pay for itself relatively quickly.
However, major wall or floor work can cost considerably more.
Therefore, consider:
- Installation cost
- Expected energy saving
- Expected bill saving
- Lifespan
- Maintenance
- Comfort
- Other work required
Some improvements may still be worthwhile even with a long financial payback because they greatly improve comfort.
However, understand what you are buying and why.
Insulate Before Increasing Heating Demand
If a home loses heat quickly, simply installing a larger heating system may treat the symptom rather than the cause.
Reducing heat loss first can mean the property needs less heat to remain comfortable.
As a result, a future heating system may have less work to do.
This becomes particularly important when considering technologies such as heat pumps.
A lower heat demand can make it easier to heat the property efficiently.
So, where practical:
Reduce unnecessary heat loss before deciding how much heating you need.
Insulation and Your EPC
Your Energy Performance Certificate (EPC) may contain information about the insulation already present in the property.
It may also suggest possible improvements.
This can be a useful starting point.
However, an EPC does not replace a detailed inspection of the building.
For example, the actual condition of existing insulation may not always be obvious from the certificate.
Therefore, use your EPC as one source of information rather than the final answer.
Learn more about Understanding Your EPC →
Before Paying for Major Insulation Work
Large insulation projects deserve careful thought.
Before agreeing to work, make sure you understand:
- What type of construction you have
- What problem the work is intended to solve
- What insulation system is proposed
- How moisture will be managed
- How ventilation will be maintained
- What happens around windows and doors
- What guarantees apply
- What maintenance may be required
- What the total cost will be
Where appropriate, also compare installers and quotations.
For major work, good design and installation matter just as much as the insulation product.
A Sensible Order
If you are considering insulation, a simple process can help.
1. Understand the property
Find out how the roof, walls and floors are built.
2. Look for obvious problems
Check for gaps, missing insulation and areas that feel unusually cold.
3. Deal with simple issues
Small repairs and suitable draught proofing may improve comfort before major work is needed.
4. Consider the main heat-loss areas
Look at the roof, walls, floors, windows and doors.
5. Think about moisture and ventilation
Make sure improvements will not create another problem.
6. Compare the options
Consider cost, likely savings and the effect on comfort.
7. Get suitable advice for major work
This is particularly important for solid walls, older buildings and more complex insulation projects.
In Short
Every heated home loses heat.
Insulation slows that heat loss, which means your heating system needs less energy to keep the property comfortable.
However, there is no single insulation solution for every home.
First, understand how your property is built.
Then look at where heat may be escaping.
After that, consider the most suitable improvements while also thinking about moisture, ventilation, cost and comfort.
Most importantly:
Don’t start with the insulation product. Start with the building.
Once you understand where the heat is going, it becomes much easier to decide what is worth improving.
Energility
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