Question 1

How do I know which cleaning method my façade needs?

Accepted Answer

Not every façade should be cleaned in the same way. Nu-Isoleren examines the façade material, type of contamination and condition of the surface before choosing an appropriate cleaning method.

Question 2

What insulation grants are available in Belgium?

Accepted Answer

Belgium offers various grants, subsidies and financial support schemes for insulation and energy renovation work. The support available depends on the region where the property is located. Flanders, Brussels and Wallonia each have their own rules, eligibility requirements, grant amounts and application procedures. Depending on the property and applicant, support may be available for roof insulation, cavity wall insulation, external wall insulation and other energy renovation measures. Nu-Isoleren provides an overview by region to help homeowners identify which schemes may be relevant.

Question 3

What type of insulation does my home need?

Accepted Answer

The most suitable insulation depends on the age, construction and current condition of your property. In many older homes, the roof and external walls are important areas to check. If the property has a suitable uninsulated cavity wall, cavity wall insulation may be an effective option. If there is no suitable cavity, external wall insulation with render may be more appropriate. The free Nu-Isoleren home check provides an initial indication of which solutions may suit your property.

Question 4

When should old cavity wall insulation be removed?

Accepted Answer

Older cavity insulation can settle, deteriorate or lose effectiveness over time. Poorly installed insulation from an earlier renovation may also need to be removed. Nu-Isoleren first inspects the cavity to determine whether removal is actually necessary.

Question 5

How much energy can I save by insulating my home?

Accepted Answer

The amount of energy you can save mainly depends on how well your home is currently insulated, the area being insulated and your heating system. Savings can be substantial in poorly insulated homes. In some situations, insulating a poorly insulated roof can reduce heating costs by around 30%. The Nu-Isoleren energy savings calculator provides a more personalised estimate based on your property, energy use and selected insulation measure.

Question 6

Why combine render with external wall insulation?

Accepted Answer

At Nu-Isoleren, render is installed together with external wall insulation. This gives the property a completely renewed façade while also improving the thermal envelope, without sacrificing living space inside the home.

Question 7

What does a water-repellent treatment do to my façade?

Accepted Answer

Nu-Isoleren applies a water-repellent treatment to a suitable façade to reduce the amount of rainwater absorbed by the surface, without simply covering the wall with a visible layer of paint.

Question 8

What is a good EPC or PEB rating?

Accepted Answer

A lower energy score indicates better energy performance. In Flanders, an EPC score between 1 and 100 kWh/(m² year) corresponds to label A, while a score of 0 or below corresponds to A+. Brussels and Wallonia use their own PEB scales and thresholds, so scores should always be interpreted according to the region where the property is located.

Question 9

What are the guide prices on this website based on?

Accepted Answer

Our guide prices are based on the usual price ranges for the work we carry out. They provide a realistic initial estimate, but the final price always depends on the specific property and chosen solution.

Question 10

How can I recognise rising damp in my home?

Accepted Answer

Common signs include damp patches along the bottom of walls, peeling paint, damaged plaster or moisture marks rising from floor level. Nu-Isoleren first investigates the source so that the actual moisture problem can be treated rather than only the visible damage.

Question 11

How long does it take to insulate a cavity wall?

Accepted Answer

In most cases, the cavity walls of an average home are fully insulated within a single working day, without any demolition work or inconvenience.

Question 12

Should I choose glass wool or PIR for my roof insulation?

Accepted Answer

This depends on the available space and existing roof construction. Nu-Isoleren works with materials including URSA glass wool and IKO PIR insulation. PIR can be useful where high insulation performance is needed within limited thickness, while glass wool can be a practical solution for other roof structures.

Question 13

Should I insulate my roof or the attic floor?

Accepted Answer

If the attic is heated or will become living space, insulating the roof itself is generally the logical choice. If the attic remains unheated and is rarely used, insulating the attic floor can be an attractive alternative. Nu-Isoleren assesses which solution best matches how the property is used.

Question 14

Are insulation grants different in Flanders, Brussels and Wallonia?

Accepted Answer

Yes. Insulation grants differ between the three Belgian regions. Flanders has its own renovation support system, the Brussels-Capital Region has separate financial support and financing schemes, and Wallonia operates its own grant system. Grant amounts are not the only difference: income requirements, technical standards, eligible work and application procedures can also vary. Nu-Isoleren therefore recommends checking the rules for the region in which the property is located before insulation work begins.

Question 15

Where should I start when insulating my home?

Accepted Answer

For a poorly insulated property, the roof is often a logical place to start because roof insulation can significantly reduce heat loss. The external walls can then be assessed for cavity wall insulation or external wall insulation. The ideal order depends on the property itself. Nu-Isoleren uses the home check to assess the roof, walls, façade and possible moisture issues before suggesting the most relevant solutions.

Question 16

Are the prices shown final prices?

Accepted Answer

No. The amounts shown are indicative guide prices. For a final price, we assess your individual project and provide a tailored quotation.

Question 17

How do I know if my cavity walls can be insulated?

Accepted Answer

Not every cavity wall can be insulated without an inspection. The width and condition of the cavity, the exterior wall and any existing insulation should first be checked. An inspection can determine whether the cavity is suitable for insulation with EPS beads.

Question 18

How does Nu-Isoleren remove old cavity wall insulation?

Accepted Answer

The removal method depends on the type and condition of the existing insulation. The old material is removed from the cavity so the space can be cleared as thoroughly as possible. Afterwards, we can assess whether the wall is suitable for new insulation.

Question 19

How much can I save with roof insulation?

Accepted Answer

Roof insulation is often one of the most effective measures when a roof has little or no insulation. Around 30% of a home's heat can be lost through an inadequately insulated roof. Actual savings depend on the existing insulation, roof area, heating system and current energy consumption, which is why Nu-Isoleren calculates an estimate based on your individual situation rather than promising one fixed percentage.

Question 20

Which insulation does Nu-Isoleren use behind render?

Accepted Answer

For our externally insulated rendered façades, we use EPS insulation boards. The insulation, façade system and rendered finish work together as one complete solution, combining insulation and façade renovation.

Question 21

Can my façade be protected after cleaning?

Accepted Answer

Yes. Where the façade is suitable, cleaning can be followed by a water-repellent treatment. The surface is first cleaned and prepared before the protective treatment is applied.

Question 22

How does Nu-Isoleren treat rising damp?

Accepted Answer

Where the wall is suitable, openings are drilled at a controlled level and a damp-proof treatment is introduced. This creates a barrier designed to stop moisture from continuing to rise through the masonry, after which the existing wall can gradually dry.

Question 23

How is an EPC or PEB score calculated?

Accepted Answer

An energy performance score is calculated using the energy-related characteristics of the property. These include the size of the home, roof, wall and floor insulation, windows and doors, heating, domestic hot water, cooling, ventilation and solar energy systems. Standardised assumptions are used so that the energy performance of different homes can be compared.

Question 24

Does my façade need cleaning before a water-repellent treatment?

Accepted Answer

A water-repellent treatment performs best on a clean and suitable façade. Nu-Isoleren therefore checks the condition of the surface first and, where necessary, cleans it before applying the treatment.

Question 25

Is every façade suitable for a water-repellent treatment?

Accepted Answer

No. The material and condition of the façade matter. Nu-Isoleren therefore assesses the surface first and, where necessary, recommends repairs before applying the treatment.

Question 26

Can my cavity walls be insulated again after the old insulation is removed?

Accepted Answer

In many cases, yes. Once the old insulation has been removed, Nu-Isoleren reassesses the condition of the cavity. If suitable, the wall can then be re-insulated using a modern EPS bead system.

Question 27

Can cavity wall insulation cause moisture problems?

Accepted Answer

The EPS system used by Nu-Isoleren absorbs virtually no water and retains its insulating properties within the cavity. Before installation, we still check that the cavity and exterior wall are suitable and that there are no existing defects that need to be resolved first. This combines a moisture-resistant insulation material with correct installation.

Question 28

Can Nu-Isoleren insulate an existing roof from the inside?

Accepted Answer

Yes. Many existing pitched roofs can be insulated from the inside without replacing the entire roof covering. Nu-Isoleren first examines the existing roof structure and then selects a suitable insulation build-up and material.

Question 29

Can I get a grant for roof insulation?

Accepted Answer

Financial support may be available for roof insulation, depending on the region and the applicant's circumstances. Eligibility can depend on factors such as income, the property, the insulation performance and the date of application. In Flanders, roof insulation falls within the roof category of Mijn VerbouwPremie, although eligibility rules changed in 2026. Nu-Isoleren installs roof insulation using solutions including glass wool and PIR insulation boards.

Question 30

How do I know whether my home has cavity walls that can be insulated?

Accepted Answer

Many homes built from around 1960 onwards have cavity walls, but the construction year alone cannot confirm this with certainty. Wall thickness, brickwork and certain ventilation openings can provide useful indications. Before cavity wall insulation is installed, the cavity should also be checked for sufficient width, cleanliness and technical suitability, and the external façade should be in good condition. Nu-Isoleren can inspect the cavity on site and determine whether EPS bead cavity wall insulation is suitable.

Question 31

What does kWh/(m² year) mean on an EPC or PEB certificate?

Accepted Answer

kWh/(m² year) expresses the calculated annual primary energy performance per square metre of floor area. A lower figure generally indicates a more energy-efficient property. It is a theoretical energy performance figure and is not the same as the actual consumption shown on your energy bills.

Question 32

How much energy can cavity wall insulation save?

Accepted Answer

Cavity wall insulation can significantly reduce heat loss through external walls when the cavity is empty or insufficiently insulated. The actual saving depends on factors such as wall area, existing insulation, cavity width and heating system. The Flemish government describes cavity wall insulation as a cost-effective way to make an existing home more energy efficient.

Question 33

Should moisture problems be treated before insulating a property?

Accepted Answer

Moisture problems should first be properly diagnosed. Damp patches at the bottom of internal walls may indicate rising damp, while moisture on an external façade can have a different cause. Installing insulation without understanding the source of the moisture is therefore not recommended. Nu-Isoleren also provides rising damp treatment, water-repellent façade treatment and façade services when these are required before or alongside insulation work.

Question 34

How accurate is the price calculator?

Accepted Answer

The price calculator provides an initial estimate based on the information you enter. The result is intended as a guide and does not replace a final quotation after your property has been assessed.

Question 35

Can I get a grant for cavity wall insulation?

Accepted Answer

Cavity wall insulation may qualify for financial support in certain situations. The property, applicant and work must meet the requirements of the relevant region. In Flanders, filling a suitable existing cavity wall is included within the external wall category of Mijn VerbouwPremie and must comply with specific technical conditions. Nu-Isoleren insulates suitable cavity walls with EPS beads after checking whether the cavity is technically suitable for insulation.

Question 36

Is the Nu-Isoleren EPC calculator official?

Accepted Answer

No. The Nu-Isoleren calculator provides an indicative estimate based on the property information you enter. The result is not an official EPC or PEB certificate and cannot replace an official certificate required for purposes such as selling or renting a property. Official certificates must be prepared according to the applicable regional certification rules by an authorised professional.

Question 37

Which saves more energy: roof, cavity wall or external wall insulation?

Accepted Answer

There is no single insulation measure that produces the greatest saving in every property. Roof insulation may be the priority in a home with an uninsulated roof, while cavity wall or external wall insulation may have more impact when the walls are the weakest part of the building envelope. External wall insulation can also accommodate a thicker layer of insulation than is normally possible inside an existing cavity.

Question 38

How do I know if my home has cavity walls?

Accepted Answer

Many homes built between approximately 1920 and 1975 have cavity walls that were originally built with little or no insulation. More recent homes often already contain insulation, but the construction year alone is not enough to be certain. Nu-Isoleren therefore checks the wall construction and condition first to determine whether the cavity is suitable for insulation with EPS beads.

Question 39

Can Nu-Isoleren inspect my property before I decide which insulation I need?

Accepted Answer

Yes. The Nu-Isoleren online home check is intended as an initial assessment. An on-site inspection can provide a more accurate picture of the technical condition of the property. This is especially important for cavity walls, existing cavity insulation, damaged façades and moisture problems. Nu-Isoleren can then determine which work is technically suitable for the property.

Question 40

Why can the estimated EPC score differ from my official certificate?

Accepted Answer

An official EPC or PEB assessment uses a detailed regional calculation methodology and more technical information about the building. An online calculator does not always have access to all of these details and therefore has to make assumptions for some inputs. The estimated result can consequently be higher or lower than the score on an official certificate.

Question 41

Why does Nu-Isoleren use EPS beads for cavity wall insulation?

Accepted Answer

Nu-Isoleren uses EPS beads because they are lightweight, dimensionally stable, moisture-resistant and provide strong thermal insulation. Different bead sizes also help fill the available cavity space effectively. We work with ISOMO EPS and an ATG-approved system for retrofitting cavity wall insulation.

Question 42

How accurate is the Nu-Isoleren energy savings calculator?

Accepted Answer

The Nu-Isoleren calculator provides an indicative estimate rather than a guaranteed saving. It considers factors including property type, construction year, existing insulation, insulation area, heating source and annual energy consumption. Actual results can also be affected by the exact construction, insulation thickness, airtightness, indoor temperature, weather and heating behaviour.

Question 43

Can I estimate the EPC rating of my home myself?

Accepted Answer

Yes. Our EPC tool can provide an indicative estimate based on factors such as insulation, windows, heating and property type. The result is not an official EPC certificate.

Question 44

Can I combine several insulation grants?

Accepted Answer

It may be possible to combine different types of support, but the rules depend on the region, the applicant and the work being carried out. A property may require both roof and wall insulation, for example, with each category subject to separate eligibility conditions. Certain schemes may also be combined with other financial incentives, while some combinations are restricted. Nu-Isoleren recommends checking the applicable rules before starting the renovation work.

Question 45

Can I calculate how much energy I could save with insulation?

Accepted Answer

Our energy savings calculator can provide an initial estimate of the potential savings after insulation work. Actual savings depend on factors such as your home, existing insulation, heating system and energy consumption.

Question 46

Can I combine roof insulation, cavity wall insulation and façade work?

Accepted Answer

Yes. Several parts of a property can be improved as part of the same renovation. A home may need both roof insulation and cavity wall insulation, for example. If the cavity is unsuitable, external wall insulation with render may be a better option. Façade cleaning, hydrofuge treatment or moisture treatment can also be combined where appropriate. Nu-Isoleren assesses which combination of services best matches the condition of the property.

Question 47

Can insulation improve my EPC or PEB score?

Accepted Answer

Yes. Roof, wall and floor insulation are taken into account when assessing the energy performance of a home. Improving insulation can reduce heat loss and contribute to a better energy score. The exact effect depends on the existing building, insulation levels, technical systems and other characteristics of the property.

Question 48

Can insulation improve my EPC or PEB rating?

Accepted Answer

Yes. Roof, cavity wall and external wall insulation can improve a property's energy performance by reducing heat loss through the building envelope. This may have a positive effect on an EPC or PEB rating. The exact change depends on the complete property and the official regional calculation method, so the Nu-Isoleren calculator does not replace an official EPC or PEB certificate.

Question 49

Where can I find the current insulation grant amounts and eligibility conditions?

Accepted Answer

Current grant amounts, income thresholds, technical requirements and eligibility conditions are published by the competent authority in each Belgian region. The regional grant pages from Nu-Isoleren provide separate information for Flanders, Brussels and Wallonia and can direct homeowners to the relevant official sources. Because grant schemes can change, the conditions should always be checked before work begins and before submitting an application.

Question 50

What is the difference between EPC and PEB?

Accepted Answer

EPC is the term commonly used in Flanders for the energy performance certificate. Brussels and Wallonia mainly use PEB, short for Performance Énergétique des Bâtiments. They serve a similar purpose, but each Belgian region uses its own calculation methodology, energy label scale and thresholds.

Question 51

I do not know which improvements my home needs. What should I do?

Accepted Answer

Use our home check. By answering a few questions about your property, you can get an initial indication of which insulation or renovation measures may be relevant.

Question 52

Can I combine different insulation measures to save more energy?

Accepted Answer

Yes. Improving several parts of the building envelope can reduce heating demand more than addressing only one area. Roof insulation can, for example, be combined with cavity wall or external wall insulation. The Flemish government notes that heating a poorly insulated home can cost more than twice as much as heating a well-insulated one.

Question 53

Is my EPC or PEB score the same as my actual energy consumption?

Accepted Answer

No. EPC and PEB scores are theoretical calculations based on standardised conditions so that properties can be compared consistently. Actual consumption also depends on factors such as occupancy, indoor temperature, heating habits and how much of the property is heated. As a result, actual energy consumption can differ substantially from the calculated score.

Question 54

Can grants reduce the final cost of insulation work?

Accepted Answer

Certain insulation measures may qualify for grants or other forms of financial support. Conditions vary depending on the work and may change, so visit our grants page for further information.

Question 55

Why can the final price differ from the guide price?

Accepted Answer

Factors such as surface area, accessibility, the condition of the property, required preparation, material choice and technical requirements can all affect the final cost.

Question 56

How can I get an exact price for my project?

Accepted Answer

Request a no-obligation quotation. Based on the work required and the specific situation of your property, we can determine an accurate price for your project.

Question 57

Does rising damp disappear immediately after treatment?

Accepted Answer

The treatment addresses further rising moisture, but water already present in the wall does not disappear overnight. The masonry needs time to dry gradually. Nu-Isoleren can therefore also advise when the treated wall is ready for further finishing.

Frequently asked questions about insulation and façade works

General & Grants

Façade cleaning

Cavity wall insulation removal

Render

Façade waterproofing

Rising damp

Cavity wall insulation

Roof insulation

Can't find your answer?

Calculate

About us