Heat loss is often invisible, yet it costs you money and comfort every single day. Especially in older homes, it can be challenging to know exactly where the warmth is escaping. A thermal scan reveals hidden heat loss and gives you the insights you need.
What is a thermal scan?
A thermal scan — also called thermography or sometimes a thermoscan — is an inspection using an infrared camera that visualises temperature differences on walls, roofs, windows and floors.
This insight is particularly valuable today: the energy transition is in full swing, energy prices are rising, and buildings need to become more efficient. In cities like Brussels, for example, many homes are old, partially renovated or built in different phases. Thermal bridges, air leaks and missing insulation are therefore common.
In 2023, a thermographic inventory of all roofs in the City of Brussels was carried out. These aerial images show the heat loss of the surveyed buildings with a precision of 40 cm.
Take a look at Brussels’ aerial thermography
How does it work?
The camera records infrared radiation and converts it into a thermal image, known as a thermogram. Temperature differences become visible through a colour scale:
- Warm areas: red/orange
- Cold areas: blue/purple
This gives you a visual map of the heat loss in your home.
Although thermography is used in many sectors — from medicine to industry — it is particularly powerful in construction. It allows you to 'see through' a wall, provided there is enough temperature difference between inside and outside.
When is the best time?
For an accurate measurement, there must be at least a 10°C temperature difference between indoors and outdoors. That’s why thermography is usually performed between October and April, ideally under the following conditions:
| Early in the morning or late in the evening |
| On cloudy days |
| No rain or snow in the previous 24 hours |
| Heating running at room temperature for at least 12 hours so heat losses become visible |
| Ventilation grilles closed and curtains open |
| Low wind |
Wind can disturb or literally blow away warm air leaks, making them difficult to measure from outside. Air leaks are therefore always detected from the inside.
What problems can it reveal?
A thermal scan not only shows What do I need to know about insulation?how well your home is insulated, but also highlights many other issues you’d rather discover sooner than later.
Energy loss and insulation problems
- Missing or sagging insulation
- Thermal bridges in concrete structures, balconies or window frames
- Gaps and cracks that let heat escape
Not every thermal bridge is immediately a problem. It becomes critical when the interior surface temperature is less than 3°C above the dew point, as this can lead to condensation and mould.
Comfort and moisture issues
- Areas at risk of condensation
- Damp walls or floors
- Spots prone to mould growth
Technical defects
- Overheated electrical wiring or components that may pose a fire risk
- Leaks in underfloor heating or flat roofs
- Poorly balanced radiators
- Pipes with insufficient flow
- Solar panels not performing optimally
Thermography is often combined with moisture measurements, helping you determine whether a cold spot is caused by heat loss, moisture, or both.
A thermal scan is a powerful tool, but not a complete X‑ray of your home. It does not reveal the exact thickness of insulation, whether a vapour barrier is present, or the condition of the cavity wall or full construction build‑up
DIY or professional?
You can perform a thermal scan yourself using rented or affordable equipment, but the difference compared to a professional scan is significant.
DIY
Rental typically costs €50–100 per day (buying starts around €300–1000). It’s cheap and flexible, but image quality is limited and interpreting what you see is not always easy.
Professional
You get better equipment, clear explanations and advice you can apply immediately. It costs more and depends on the specialist’s availability.
A professional scan is especially useful when:
- you want an in‑depth analysis
- you’re looking for concrete improvement points
- you have little construction knowledge
- you need the results for subsidies
Tip: if you want a full analysis of the energy losses in your home, combine your thermal scan with an airtightness test (blower‑door test).
Sometimes the problem is obvious without a camera: walls feel icy cold, snow doesn’t stay on the roof, you feel draughts in several places, or you can see that insulation is visibly too thin. In such cases, it makes more sense to invest directly in insulation or air‑sealing.
Beware of misleading 'free thermography' offers!
A proper thermographic analysis requires time, expertise and a good camera. Free scans are often marketing tricks where:
- images are shown without a temperature scale
- incorrect conclusions are drawn
- problems are “found” that don’t actually exist
A faulty analysis can even cost you money. Always choose an independent expert who understands both the camera and building physics.
What happens next?
A thermal scan is not the end point, but the start of targeted action. It immediately shows where your home loses energy and which improvements offer the best return. Some measures require a larger investment, while others deliver quick gains on a small budget.
| Targeted measures | Quick wins |
|---|---|
| Improve insulation (roof, walls, floor) | Letterbox brushes |
| Seal air leaks | Draught strips |
| Address thermal bridges where possible | Radiator fans |
| Replace glazing with HR++ or triple glazing | Thermostatic valves |
| Optimise the heating system |
With the results of a thermal scan, you can tackle the biggest sources of energy loss in a very targeted way. And you’ll notice the difference quickly: lower energy bills, more comfort, a more sustainable home and often a higher property value. Small interventions can make a surprisingly big impact.
Do you have questions about your thermal scan results? Want to know more about the right thermal insulation for your home? Contact Homegrade for personalised advice.