Heat loss: What are the causes and solutions?

Heat loss or thermal loss, as it can be called, is where heat escapes from your home and you can’t control it.

Heat loss occurs when a building is poorly insulated. If your home is experiencing heat loss, heat could be escaping through your walls, roof and other openings, such as doors, windows and or old and out of date skylights.

When you take steps to reduce heat loss, you should also see a reduction in your energy bills and your home’s carbon footprint.

Every home has a thermal footprint. There are six main factors that determine how effective this is at retaining or losing heat.

1. Age and type of construction: older buildings often do not meet the latest insulation building regulations, making them more likely to suffer from heat loss.
2. Insulation quality: poor quality and inadequate insulation is one of the main causes of heat loss.
3. Building materials: some construction materials, such as inferior insulating materials, single-glazing and porous products, can increase heat loss.
4. Condition of windows and doors: old or poorly insulated windows and doors can be a major source of heat loss.
5. Building position: the location of your home can impact how much heat it retains. If your home is built on a hill, for example, and has little protection from the elements, this could make it harder to keep out draughts.
6. Modifications and extensions: if you renovate or extend your home and don’t include adequate insulation it will be more susceptible to heat loss.

According to The Energy Saving Trust, an independent organisation working to address the climate emergency, most of the heat in our homes escapes through one or more of these areas:

1. Walls: about a third of heat is lost through uninsulated walls.
2. Floors: a lot of heat can escape from an uninsulated ground floor and heat can also be lost from floors in rooms above an uninsulated space, such as a garage.
3. Roof: about a quarter of heat is lost through an uninsulated roof and loft space.
4. Windows: Single-glazed windows and poorly insulated doors will leak heat from your home.
5. Draughts: heat escapes through poorly fitted doors and windows and open chimneys.

To discover where heat transfer is occurring in your home and it’s losing heat, spend some time walking around each of your rooms and noting if some rooms feel colder than others and if some areas of each room feel particularly cold.

• Temperature differences within a room – if you notice a difference in temperature between the walls of your room and the middle of your room, this is a sign that your insulation is inadequate. Use a room thermometer to measure the temperature change more accurately. A difference within a room of 2 to 3°C indicates that you need to improve the insulation in the room.
• Draughts – See if you can feel air coming in through doors or windows or around their frames.
• Condensation and mould – Condensation on your windows and mould on your walls is another sign that heat is not evenly distributed across your room and it’s poorly insulated.
• Heating not doing its job – If your room feels cold even when the heating has been on for a while, it's a sign that your room is leaking heat.

A thermal bridge is a cold spot in your home from where warm air can escape outside and cold air can come inside. Here is where you are likely to find thermal bridges in your home:

• Wall-to-roof junctions – there could be gaps in the insulation where your walls meet your roof.
• Around openings – there could be space between the frames and the glass of your windows and between your window and door frames and your walls.
• Balconies and overhanging elements, like a porch – these are connected directly to the structure of your building and there may be tiny spaces where they link from which warm air can escape.
• Exposed floors – heat can escape through an uninsulated ground floor and uninsulated floors that sit above an uninsulated room, such as a garage.
• Partition walls and corners of buildings – the internal walls and the corners of your property may be inadequately insulated, allowing heat to escape.

A complete energy audit of your home will give you an accurate measurement of its level of heat loss. When you sell your home, you are required to obtain an energy performance certificate (EPC), which will classify your home from A for the most efficient to G for the least efficient. You can have this assessment done even if you don’t plan to sell.

When you use a professional to calculate heat loss in your home, they will look at its windows, doors, walls, heating and ventilation. They may also use specific tools and techniques, including:

The blower door test

A blower door is a diagnostic tool that measures how airtight your home is and shows where air is coming in and out of it in places it shouldn’t.

Thermal imaging

Here, an infrared camera is used to locate where heat is escaping from your home. It is very effective at pinpointing poorly-insulated areas and can show how heat loss can be reduced if you carry out renovation work.

Endoscopic camera

An endoscopic camera is designed to detect heat transfer in inaccessible areas of your home. It will show where heat is being lost through wall cavities or spaces under your roof, for example.

Each area of your home, from your roof to your boiler, must be considered when calculating its heat loss. The thermal performance of your home is calculated as its ‘U Value.’ The U Value is a measure of how quickly heat passes through a material or structure and it calculates the effectiveness of the insulation in your home. The lower your home's U Value, the better its insulation.

If you want to improve the energy efficiency of your home, it is crucial to calculate how much heat it is losing and from where. A specialist heat engineer can help you with these calculations. If you’re doing any work on your home that needs to meet building regulations, your building regulation inspector may look at how the materials you use impact your home’s U Value.

A heat engineer will use specialist software that accounts for the thermal performance of your building's materials, its type of ventilation and the effectiveness of its insulation.

If you’re installing a new heating system, this method can give you a pretty accurate estimate of how much heat you will need for each of your rooms and show you how measures to reduce your heat loss will also reduce your heating needs.

Investing in the latest insulation solutions will make your home more comfortable to live in all year round and:

1. Reduce your energy bills

Effective insulation will maintain a steady ambient temperature in your home and reduce how much you need to use your heating in winter or fans in hotter weather. Consequently, your electricity and gas bills should become cheaper.

2. Cut your carbon footprint

As a well-insulated home runs on less energy, it will also lower your greenhouse gas emissions and be more environmentally friendly.

3. Increase your home's value

Energy-efficient homes are now highly sought after, so improving your home’s insulation can also boost its value.

4. Improve your wellbeing

The latest insulation will make your home feel cooler in the hotter months and warmer in the colder seasons, so you’re less likely to wake up sweating or find yourself grabbing an extra jumper at any time of the year.

Heat loss problems can be effectively addressed with the latest insulation and ventilation systems.

Once you have identified thermal leaks in your home, there are several ways you can fix them and reduce your energy bills.

• Loft insulation: the loft is a major cause of heat loss and insulation will put a stop to this.
  • To find out why you should insulate your loft and to identify the best approach to take and the right insulation materials for your home read our article: Internal roof insulation: the complete guide

• Replacement windows: switch single pane windows for double or triple-glazed windows for better thermal insulation. If you have very old roof windows, consider replacing them with VELUX roof windows, which are double glazed as standard.
  • Read all about window insulation here: Creating a more efficient home with energy saving windows .

• Insulating walls and fixtures: external and internal insulation can help significantly reduce heat loss in your home. Improving the insulation around boilers and home appliances can help reduce heat loss too. To make your home extra eco-friendly, opt for insulation made from a natural material, such as hemp or cellulose.  

Choosing the right insulation materials is crucial:

• Glass wool, also known as fibreglass, and rock wool are ideal for insulating lofts and walls. 

• Polyurethane and moulded and expanded polystyrene (EPS): lightweight and efficient, these materials are perfect for insulating floors and ceilings.

For useful guidelines, read our article: What is the best thermal insulation for ceilings?

• Double or triple-glazed windows: installing replacement windows can help with reducing heat loss from your home and in particular from roof windows.

Read more about replacing your roof windows here: How to replace a roof window

Good to know: VELUX roof windows include a 15 mm Argon gas insulating layer, which eliminates the cold wall phenomenon and leads to a more comfortable indoor environment. They also feature solar control glazing that blocks 77% of heat, which is 41% more than previous generations of windows.

Transform your space with VELUX roof windows, skylights and sun tunnels!

You may be eligible for financial support with your insulation and heat-loss projects. In England, Scotland or Wales, financial support may be available for insulation through the Great British Insulation Scheme (1). This government initiative is designed to help households cover the cost of insulation improvements that lower energy bills and make homes more environmentally friendly. If your home is in Northern Ireland, you may qualify for a grant for insulation through the government Affordable Warmth Scheme. (2). In the Republic of Ireland, the Sustainable Energy Authority of Ireland offers Home Energy Grants to help you improve the insulation of your home with insulation. (3).

Check government websites to see what grants and subsidies might be available to you.