Why do I have mould in my apartment in Luxembourg?

Mould appears when moisture stays on a surface for too long. Common causes are condensation, poor ventilation, a clogged mechanical ventilation system, a leak, a thermal bridge, a cold wall or water ingress.

Can a dirty mechanical ventilation system encourage mould?

Yes. If the mechanical ventilation system or the air vents are clogged, moisture may be less well extracted. The damp air then stays longer in the home, which can encourage condensation, odours and mould.

What humidity level is recommended in a home?

A comfortable indoor humidity level is generally between 30% and 60%. Persistently high humidity increases the risk of condensation and mould growth.

How can you recognise a ventilation problem?

Common signs are condensation on the windows, a musty smell, a bathroom that dries slowly, dark stains in the corners, heavy air or an extract vent that draws poorly.

What should you do about mould in the bathroom?

You should reduce steam, ventilate effectively, check the extract vent, carefully clean accessible areas and have the ventilation checked if the marks come back.

Who should you contact for a mould problem in Luxembourg?

If you are a tenant, inform the landlord promptly. For a problem linked to ventilation, the mechanical ventilation system or indoor air, HUMINUS can inspect and service the ventilation components.

How do you say "mould" in Luxembourgish?

In Luxembourgish, mould is generally called Schimmel. Damp is called Fiichtegkeet, and condensation is called Kondensatioun.

Is cleaning the mechanical ventilation system enough to remove mould?

Not always. Cleaning the mechanical ventilation system can help if the problem comes from poor air extraction. If the cause is a leak, water ingress, a thermal bridge or a building defect, that cause also needs to be addressed.

Why do I get condensation on my windows?

Condensation appears when damp air meets a cold surface. It can be encouraged by a lack of ventilation, a room that is too humid, thermal bridges or insufficient ventilation.

Does HUMINUS operate in Luxembourg?

Yes. HUMINUS operates in Luxembourg for the inspection, cleaning and servicing of ventilation and mechanical ventilation systems.

How common is damp housing in Luxembourg?

It is common. According to Eurostat (EU-SILC survey, 2023), 18% of Luxembourg’s population lives in a dwelling with a leaking roof, damp walls or foundations, or rot — nearly one resident in five. Condensation and insufficient ventilation are among the most frequent causes.

Is mould dangerous for your health?

The World Health Organization (Guidelines for Indoor Air Quality, 2009) concludes that occupants of damp or mouldy homes face an increased risk of respiratory symptoms, respiratory infections and worsening asthma — the meta-analyses it cites estimate this increase at 30 to 50%. Treating the damp and ensuring good ventilation reduces that risk.

Mechanical ventilation & indoor air specialist in Luxembourg

Mechanical ventilation·Mould·Damp·Condensation

Mould in your home in Luxembourg?
Check the humidity and ventilation first.

Poor air extraction, a clogged mechanical ventilation system or blocked vents can encourage condensation, musty odours and black stains. HUMINUS inspects and services your ventilation to help your home breathe properly.

Mould, damp, condensation: HUMINUS helps your home breathe better.

Service in Luxembourg · Français / Lëtzebuergesch · Mechanical ventilation, ventilation, indoor humidity

Humidity benchmark

69%

To monitor

30–60%

60–70%

>70%

Visual examples · Common signs

The signs not to ignore

Mould doesn’t always start as a large black spot. It often shows up first through weak signals: condensation, a musty smell, blackened seals, blistering paint or indoor air that is too humid.

Schimmel, Fiichtegkeet a Kondensatioun: d’Zeeche fréi erkennen.

Black spots
Around windows, in corners, on grout lines or on the ceiling.
LU · schwaarze Flecken
mouldwindowcold wallLuxembourg
Musty smell
Heavy, stuffy air or a persistent smell in a room.
LU · muffege Geroch
musty smellwardrobestagnant airdamp
Condensation
Frequent misting on windows or cold surfaces.
LU · Kondensatioun
condensationwindowdamp airLuxembourg
Blackened seals
Often in the shower, around the bathtub or the sink.
LU · schwaarze Fugen
bathroomblack sealsmechanical ventilationdamp
Blistering paint
A possible sign of damp in the wall or ceiling.
LU · Faarf mécht Blosen
blistering paintdamp wallwater ingressdamp
Peeling wallpaper
Can signal persistent damp behind the surface.
LU · Tapéit léist sech
wallpaperwall damphidden mouldLuxembourg
Damp air
A sense of stagnant air or a poorly ventilated room.
LU · fiichte Loft
damp airbedroomventilationmechanical ventilation
Furniture or clothes that smell musty
Often linked to a lack of air circulation.
LU · muffege Kleeder
wardrobeclothesmusty smellventilation

These visual examples help you recognise the most common signs of damp in homes in Luxembourg. The cause can be insufficient ventilation, a clogged mechanical ventilation system, a thermal bridge, water ingress or indoor air that is too humid.

Worth remembering: cleaning a visible mark is not always enough. If the signs come back, the cause needs to be identified: damp, condensation, ventilation, a leak or a building defect.

Mechanical ventilation inspection · Damp advice · Service in Luxembourg

Recognise these signs?

Ventilation + humidity diagnosis as soon as possible

A HUMINUS technician inspects your mechanical ventilation, measures the humidity room by room, and provides you with a report you can use with your insurer or building manager if needed.

+352 621 96 25 22Call

SEO mesh · Illustrative cases

Common cases of mould in a home

Visual examples to help recognise typical situations: bathroom, bedroom, cellar, kitchen, furniture, laundry room and condensation on windows.

Before and after of a bathroom with mould, damp and improved ventilation in Luxembourg — Bathroom
Shower steam, damp joints, clogged extract vents and poor ventilation can encourage black staining.
Bathroom, steam, black joints, damp corners and insufficient mechanical ventilation.
Mechanical ventilationCondensationJointsDamp

Before and after of a bedroom with condensation on the windows and mould around the wall in Luxembourg — Window & bedroom
Condensation on the glazing is often the first sign of indoor air that is too humid or a cold wall.
Window & bedroom, condensation, cold wall and indoor air that is too humid.
WindowCondensationCold wallMould

Before and after of a damp cellar with mould and improved ventilation in Luxembourg — Cellar
Cellars are prone to persistent damp, water ingress, stagnant air and musty smells.
Cellar, damp, water ingress, musty smell and stagnant air.
Damp cellarWater ingressStagnant airMould

Before and after of a kitchen with mould, condensation and damp in Luxembourg — Kitchen
Cooking, steam, a cold window, an insufficient extractor hood or a lack of extraction can create damp areas.
Kitchen, cooking steam, condensation, damp around the windows and lack of extraction.
KitchenSteamExtractionVentilation

Before and after of mould behind furniture caused by a lack of ventilation in Luxembourg — Behind the furniture
When furniture is placed too close to a cold wall, air circulates poorly and damp can build up.
Behind the furniture, cold walls, blocked air and a lack of circulation.
FurnitureCold wallBlocked airVentilation

Before and after of a damp laundry room with mould and improved ventilation in Luxembourg — Laundry room
Drying laundry, a washing machine, a closed-off room and insufficient ventilation can sharply increase damp.
Laundry room, drying laundry, persistent damp and insufficient ventilation.
Laundry roomLaundryDampVentilation

Illustrative images. Each home must be assessed based on the real cause: ventilation, condensation, a leak, water ingress, a thermal bridge or a building defect.

Every place in a home where mould can appear

Each room has its own causes: steam, cold walls, condensation, leaks, lack of airing or insufficient mechanical ventilation.

Bathroom

Common signs

·Black grout lines around the shower
·Stained ceiling or peeling paint
·Persistent steam fogging after a shower

Possible causes

·Shower steam not properly extracted
·Clogged extract vent
·Undersized or non-functioning mechanical ventilation

What HUMINUS can check

Inspection of the extract vent
Cleaning of the grille and filter
Check of the airflow rate

frmoisissure salle de bainfrjoints noirsfrVMC salle de bainlbSchimmel am Buedzëmmerlbschwaarz FugenlbSchimmel an der DuschdeSchimmel im Badezimmerdeschwarze FugendeBadlüftungenbathroom moldenblack mold in showerenbathroom ventilation

The real causes: ventilation, damp or a building defect?

A clear grid for telling apart what comes from the air, from moisture, or from the building itself.

Category 1

Air & ventilation

Clogged mechanical ventilation
Blocked extract vent
Insufficient airflow
Stagnant air
Poorly ventilated room
Unmaintained filter

Category 2

Damp & condensation

Condensation on the windows
Shower steam
Cooking
Laundry dried indoors
Damp cellar
Relative humidity too high

Category 3

Building & water ingress

Thermal bridge
Cold wall
Cracked façade
Water leak
Faulty roof or gutter
Rising damp

Worth knowing: Servicing the ventilation helps when the problem comes from air renewal. Where there is a leak, water ingress or a structural defect, the cause has to be fixed on the building.

The HUMINUS method

A clean, clear cause-oriented approach.

Step 1

InspectionKontroll

Visual check of the vents, filters, airflow and sensitive areas.

Step 2

CleaningBotzen

Cleaning of the extract vents, grilles, accessible filters and relevant parts depending on the installation.

Step 3

Airflow checkLoftfloss

Checking the air renewal and identifying signs of poor extraction.

Step 4

Prevention adviceVirbeugung

Simple recommendations to reduce moisture, condensation and stagnant air.

Recognise these signs?

Ventilation + humidity diagnosis as soon as possible

A HUMINUS technician inspects your mechanical ventilation, measures the humidity room by room, and provides you with a report you can use with your insurer or building manager if needed.

+352 621 96 25 22Call

Mould & damp glossary for Luxembourg

Because in Luxembourg, people search in French, Luxembourgish, German and English.

Français	Lëtzebuergesch	Deutsch	English
Moisissure	Schimmel	Schimmel / Schimmelpilz	mold / mould
Humidité	Fiichtegkeet	Feuchtigkeit	humidity / dampness
Condensation	Kondensatioun	Kondensation	condensation
Ventilation	Belëftung	Lüftung / Belüftung	ventilation
VMC	VMC / Belëftungsanlag	Lüftungsanlage	mechanical ventilation
Air intérieur	Loft dobannen	Raumluft	indoor air
Odeur de moisi	muffege Geroch	muffiger Geruch	musty smell
Taches noires	schwaarz Flecken	schwarze Flecken	black spots
Mur froid	kal Mauer	kalte Wand	cold wall
Pont thermique	Wärmebréck	Wärmebrücke	thermal bridge
Fuite d’eau	Waasserleck	Wasserleck	water leak
Infiltration d’eau	Waasserandrang	Wassereintritt	water ingress
Cave humide	fiichte Keller	feuchter Keller	damp basement
Salle de bain	Buedzëmmer	Badezimmer	bathroom
Cuisine	Kichen	Küche	kitchen
Chambre	Schlofkummer	Schlafzimmer	bedroom
Nettoyage VMC	VMC botzen	Lüftungsanlage reinigen	ventilation cleaning
Entretien VMC	Ënnerhalt vun der VMC	Wartung der Lüftungsanlage	ventilation maintenance
Bouche d’extraction	Ofzuchsventil	Abluftventil	exhaust vent
Bouche d’insufflation	Zouluftventil	Zuluftventil	supply vent

Moisissure

LU Schimmel

DE Schimmel / Schimmelpilz

EN mold / mould

Humidité

LU Fiichtegkeet

DE Feuchtigkeit

EN humidity / dampness

Condensation

LU Kondensatioun

DE Kondensation

EN condensation

Ventilation

LU Belëftung

DE Lüftung / Belüftung

EN ventilation

VMC

LU VMC / Belëftungsanlag

DE Lüftungsanlage

EN mechanical ventilation

Air intérieur

LU Loft dobannen

DE Raumluft

EN indoor air

Odeur de moisi

LU muffege Geroch

DE muffiger Geruch

EN musty smell

Taches noires

LU schwaarz Flecken

DE schwarze Flecken

EN black spots

Mur froid

LU kal Mauer

DE kalte Wand

EN cold wall

Pont thermique

LU Wärmebréck

DE Wärmebrücke

EN thermal bridge

Fuite d’eau

LU Waasserleck

DE Wasserleck

EN water leak

Infiltration d’eau

LU Waasserandrang

DE Wassereintritt

EN water ingress

Cave humide

LU fiichte Keller

DE feuchter Keller

EN damp basement

Salle de bain

LU Buedzëmmer

DE Badezimmer

EN bathroom

Cuisine

LU Kichen

DE Küche

EN kitchen

Chambre

LU Schlofkummer

DE Schlafzimmer

EN bedroom

Nettoyage VMC

LU VMC botzen

DE Lüftungsanlage reinigen

EN ventilation cleaning

Entretien VMC

LU Ënnerhalt vun der VMC

DE Wartung der Lüftungsanlage

EN ventilation maintenance

Bouche d’extraction

LU Ofzuchsventil

DE Abluftventil

EN exhaust vent

Bouche d’insufflation

LU Zouluftventil

DE Zuluftventil

EN supply vent

Frequently asked questions

Luxembourg

Mechanical ventilation, damp and mould service in Luxembourg

HUMINUS supports homeowners, tenants, property managers and professionals across Luxembourg facing damp, condensation, musty smells and insufficient ventilation. Our approach starts with indoor air: checking the vents, servicing the mechanical ventilation, cleaning the accessible parts, and prevention advice tailored to the home.

Luxembourg-villeEsch-sur-AlzetteDifferdangeDudelangePétangeStrassenBertrangeMamerHesperangeNiederanvenKäerjengRemichGrevenmacherEttelbruckDiekirchWiltz

Do you see stains, condensation or a musty smell?

Before repainting or cleaning the surface, check whether your home is properly clearing the humidity. HUMINUS inspects and services your ventilation in Luxembourg, and provides a usable report if needed.

+352 621 96 25 22

Fast response · Service in Luxembourg · Advice tailored to your home