How to Clean Internorm Windows: A Professional Guide by Window Type

1. What Is the Product

Internorm is Europe's largest window brand, fully made in Austria since 1931. The family company pioneered triple glazing and Passivhaus-certified windows, with three factories producing over 25 million units. Their products are described as "low-maintenance and easy to clean," featuring "easy-to-care-for surfaces" and "concealed hardware" for faster cleaning.

With 25 years in premium glass care, I clean Internorm windows every week across Vienna. Internorm windows are well-built, but the glass still needs proper cleaning techniques to achieve streak-free results. And depending on which Internorm window type you have, the frame around that glass needs a specific approach.

2. Why Internorm Windows Need a Specific Approach

Internorm is not a single product. Where most window manufacturers specialise in one frame material, Internorm makes three completely different window types. Before you clean, you need to know which one you have.

Internorm makes three window types: uPVC (like KF 410), uPVC/aluminium (like KF 510 with I-tec Secure), and timber/aluminium windows. Look inside the frame: plastic signals uPVC or uPVC/alu, wood means timber/alu. Aluminium cladding appears on both uPVC/alu and timber/alu exteriors. Each material needs specific cleaners. What's safe for one may damage another.

The uPVC burn-in risk. Internorm's own care manual warns that if a mixture of dirt, cleaning product, and water remains on uPVC frame surfaces, the water evaporates, leaving the remaining mixture to burn into the surface permanently. This is specific to uPVC, and it's irreversible.

Internorm uses an I-tec Secure concealed hardware system, a locking mechanism built into the frame and sash, making it invisible from the outside. The rebate area (the groove between where the window frame and sash meet, normally housing hardware) is now smooth, without visible screws or hinges. There are no oily fittings or loose covers that collect dirt. Internorm describes this as "no more dirt grooves in the rebate area." Rounded edges on the designer closing elements make the area easier to wipe clean. This is a significant cleaning advantage over older window designs.

Before getting into Internorm's official care recommendations, it's helpful to understand the foundational glass-cleaning technique. The glass is the core of the job. Everything else supports it.

3. The Foundational Technique

The Window Cleaning Manifesto covers the foundational glass-cleaning technique, essential tools, soap-water preparation, and basic squeegee turns in 5 minutes. It's free and is a smart starting point before reading the manufacturer-specific care advice below.

4. What Internorm Recommends

Internorm publishes detailed care instructions in their Fibel, also called the Gebrauchsanweisung (User Manual), covering Reinigung, Pflege und Wartung (cleaning, care, and maintenance) for each material separately. Their care and maintenance page also lists recommended products. These are the manufacturer's guidelines, presented as Internorm wrote them.

Glass:

1. Clean glass surfaces using the wet method with water and a sponge or cloth.
2. Commercial glass cleaners without abrasive components can be added to the water.
3. For stubborn stains like paint or tar splashes, use spiritus, acetone, or white spirit, followed by a wet re-clean.
4. No metallic objects. Razor blades and steel wool are explicitly prohibited.
5. No alkaline cleaning solutions, acids, or fluoride-containing cleaners.
6. Protect glass from mortar splashes, cement residue, sparks from grinding, and acid-based facade stone cleaners.

uPVC frames (Kunststoff-Oberflächen):

1. Use Internorm's specific care products: one for PVC hard finish, one for Decor finishes.
2. For general cleaning: dishwashing liquid, mild pH-neutral universal cleaner, alcohol-free glass cleaner, or clear water.
3. Always rinse frames thoroughly with clear water after cleaning. If the cleaning product residue dries on the surface, it can burn in permanently.
4. Never use nitro thinner, petrol, acetic acid, nail polish remover, alcohol, cleaning agents with orange or lemon aroma, or products containing ammonia or sulphur.
5. Insect excrement, pollen, soot particles, and iron dust (common near railway lines) can cause permanent staining on uPVC in combination with rain and UV radiation. Clean promptly.

Aluminium-Exterieur (eloxierte oder pulverbeschichtete Oberflächen):

1. Do not clean aluminium in direct sunlight. Surface temperature should not exceed 25°C.
2. Pre-clean with pure water, adding small amounts of pH-neutral detergent if needed (pH value between 5 and 8 only).
3. Use suitable soft cloths to avoid scratching.
4. Never use steam cleaners.
5. Internorm distinguishes between anodised and powder-coated aluminium, each with its own cleaner and conservation product.
6. The conservation treatment creates a temporary dirt- and water-repellent film that needs periodic renewal.
7. Alkaline leachate from facades and masonry can cause irreversible damage. Clean and conserve frames promptly if there is fresh plaster or concrete work nearby.

Timber interior (Holz/Aluminium elements):

1. Use mild cleaning agents, such as diluted dishwashing liquid or soap solutions.
2. Never use abrasive, corrosive, or solvent-containing products. Use only soft cloths.
3. Glass cleaners containing traces of alcohol can be used on both the glass and the wood frame profiles. However, dry the wood profiles immediately. Prolonged exposure to alcohol can soften the lacquer surface.
4. Interior wood is not exposed to weather, so repainting is not required under normal conditions.

Hardware (Beschlag):

1. Lubricate all moving hardware parts at least once per year with acid-free, resin-free oil or grease.
2. Only use products that do not impair corrosion protection on the fittings.
3. Windows that open and close very frequently may need more frequent lubrication.
4. Internorm warns that failure to observe lubrication intervals can lead to hardware failure.

Gaskets (Dichtungen):

1. Clean all gasket profiles at least once per year to maintain function.
2. Gaskets are essential for thermal, sound, and weather insulation.

I-tec Ventilation (I-tec Lüftung):

If your Internorm windows have the I-tec Ventilation system, they also require care and maintenance. The Fibel includes a section on I-tec Lüftung care. The filters must be cleaned regularly to maintain airflow and indoor air quality. Always follow Internorm's instructions for your ventilation model. Incorrect handling can damage the unit.

These are Internorm's own recommendations. Internorm care products are available through its distribution partner network. Following these guidelines, along with the professional glass technique below, gives you a complete approach: the material care from the brand itself and the cleaning skill from 25 years of professional experience.

5. What I Add as a Professional

Internorm's guidelines are thorough for frame and hardware care. What I add is the glass-cleaning technique. Window cleaning is glass cleaning. That's the skill. You can follow every manufacturer's care tip perfectly, but if the glass has streaks, nothing else matters. A spotless frame around dirty glass is still a dirty window.

Here is the professional method I use on Internorm windows, and on every window I clean. Step by step, you'll see how each stage builds on the last.

6. Step-by-Step Technique

Preparation: Soap Water, and Tools

Mix your soap-water solution. Dip your microfiber T-bar (a T-shaped tool covered in microfiber fabric designed for washing glass) into the solution on both sides. You need enough soap on the glass to dissolve the built-up dirt. Too little solution, and the dirt stays stuck. No amount of squeegeeing will fix that.

Agitation: The Step Most People Skip

Apply the soap water to the glass using the T-bar applicator and agitate the dirt with overlapping passes. The idea is to dissolve the dirt into the soap water, releasing it from the glass surface, so the squeegee (a flat tool with a rubber blade for wiping off water) can shave it away.

This is the step that separates professional results from amateur attempts. If the dirt isn't fully dissolved in the soap water and released from the glass, the remaining dirt still stuck will be transported over the squeegee, leaving smudges or smears. Think of it like washing dishes. You don't just run water over a greasy pan. You scrub first, then rinse.

Detail the Frame Edge Before Squeegeeing

Now that the soap is sitting on the glass and the built-up dirt has dissolved into it, detail the edge of the frame where the glass meets the putty or rubber seal. With your rag, use your finger to get into the edge and take away any pooled soap water to avoid drips.

As the frame is also part of the window, this detailing will remove dust and dirt buildup that the squeegee cannot reach. As you advance your application skills, this detailing will become more refined and targeted.

The Three Squeegee Turns

There are three fundamental squeegee turns. Mastering each one and combining them will speed up the process and reduce any chance of leaving streaks or missing spots.

Side to Side: Start at the very edge of the top of the window. Work your way across the whole window in a straight line. To avoid creating lines from water spilling over both sides of the squeegee, tilt it slightly. This angle will direct the water to spill from only one side of the squeegee channel. Wipe the squeegee rubber dry after each line is completed. This gives a clean, streak-free start to the following line. Overlap from one line to another. The smaller the overlap, the less work there is. Finishing precisely on the edge requires extra pressure on the glass into the frame and a wrist rotation to adjust the rubber blade angle.

Top to Bottom: The same principles as side to side, but working vertically. Start in the top corner edge with a dry rubber on the glass. Work your way down the whole window in a straight line. Tilt the squeegee at a slight angle so the water spills out of only one side, the lower side. Wipe the rubber dry after each line. Overlap line to line. Finish with extra pressure and a wrist rotation on the bottom edge.

Turn with a Twist (the "J" Tune): This is the professional continuous motion. One smooth movement from the top of the window to the bottom, linking turns with a wrist twist at each end. Your thumb is your guide. Start with it pointing one direction, rotate as you reach the edge of the window, move down, and repeat on the return. This turn has top-to-bottom, side-to-side, and mixed variations. There is a window for each.

On large Internorm windows where you can't reach the top, use top-to-bottom first with a pole until you reach arm height, then finish with side-to-side.

Cutting In: Before any turn, you need the squeegee rubber to make the initial contact with the glass. This can be done "dry," starting with a dry rubber on a dry edge, or "moving," slicing at an angle to create a dry starting point. The moving cut-in is more advanced, but it reduces preparation time once mastered.

Finishing: Edge Detailing

Clean away any excess soap water with your finger, pressing it into your 100% cotton towelling rag (not microfiber). Get into the edge where the glass meets the frame and remove any pooled soap water. Always control where the rag is in your hand and make sure it only touches the glass where you need it to collect the soapy water. Rotate the rag so you are only touching the glass with a clean section. Replace it with a fresh one every few windows to keep a high-quality detail.

The squeegee turn determines how much detailing you need afterwards. The better your turns, the less cleanup you need.

Internorm-Specific Tips During Technique:

Work inward from the aluminium exterior. On uPVC/alu and timber/alu models, clean the aluminium cladding first, then the glass, then the interior frame. This prevents dirty rinse water from the exterior running onto already-cleaned surfaces.

The uPVC rinse matters more than the wash. Always do a final clear-water rinse of uPVC frames. The burn-in warning in Internorm's manual is real. I've seen uPVC frames with permanent discolouration where the cleaning product was left to dry.

On timber/alu models, keep glass cleaner off the wood. If the wood frame sits directly below the glass, catch any drips. Brief contact is fine, but letting a cleaner pool on a lacquered surface while you finish the window can soften the finish.

Use the cleaning stay-arm (Putzschere). Internorm tilt-turn windows feature a cleaning stay-arm that allows you to tilt the sash beyond the standard tilt position. This gives you access to the outer glass surface from inside. Useful on upper floors.

7. How Often to Clean

Twice per year at a minimum for glass and frames. In environments with higher pollution, near industrial areas, railways, or busy roads, increase the frequency. This is especially important for uPVC frames, where contaminants can cause permanent staining.

Hardware lubrication: once per year minimum. Gasket cleaning: once per year.

Internorm also recommends annual professional servicing through its distribution partner network, covering hardware checks, gasket inspections, seal adjustments, and functional testing.

8. What NOT to Do

Sourced directly from Internorm's care manual:

1. Never use razor blades or steel wool on glass.
2. Never use alkaline solutions, acids, or fluoride-containing cleaners on glass.
3. Never use nitro thinner, petrol, acetic acid, nail polish remover, alcohol, ammonia, or sulphur-containing products on uPVC.
4. Never use orange or lemon-scented cleaning products on uPVC.
5. Never clean aluminium in direct sunlight or when the surface temperature exceeds 25°C.
6. Never use abrasive or solvent-containing products on lacquered wood.
7. Never let cleaning product residue dry on uPVC frames. Rinse with clear water.
8. Never use steam cleaners on aluminium surfaces.
9. Never use products that impair corrosion protection on hardware.
10. Never skip annual hardware lubrication. Internorm warns that this can lead to sash failure.

9. Why Professional Technique Matters

Internorm builds windows designed to last decades. Their 30-year serviceability assurance reflects that. But this assurance is conditional on following their installation and maintenance guidelines. Using the wrong cleaning products or skipping annual hardware lubrication doesn't just leave streaks; it can cause damage. It can void your warranty and reduce the lifespan of components designed to protect your home. For Passivhaus-certified Internorm windows, maintaining seals, gaskets, and I-tec systems directly supports preserving the energy performance your home was designed for.

But window cleaning is about the glass. That's the skill. The three squeegee turns, the agitation, the detailing. That's what produces the crystal-clear result.

Between Internorm's own care recommendations from their Fibel and the professional glass-cleaning technique from Orloff's Window Cleaning Training, you have everything you need. The manufacturer's guidelines are direct from the source, and the cleaning method is based on 25 years of hands-on experience.

10. Protecting Your Investment

Internorm describes their windows as "permanently beautiful" when properly maintained. The combination of proper technique with the glass and the manufacturer's recommended care for frames, hardware, and gaskets delivers that result.

The Window Cleaning Manifesto covers the foundational technique, essential tools, and the basic squeegee turns in five minutes. It is free and only takes five minutes to review, making it a smart starting point. The AR Window Cleaning Training Tool builds on this by covering all three squeegee turns, including the twist, developing muscle memory on your own mobile phone or tablet.

For the complete A-to-Z professional training, including cutting in, pole work, advanced technique, and safety, the Beginner Program is $69 with lifetime access.

About the Author:

Justin Orloff is a professional window cleaner with 25+ years of experience, based in Vienna, Austria. He regularly cleans Internorm uPVC, uPVC/aluminium, and timber/aluminium windows across the Vienna region, and he created the world's first AR window-cleaning training platform.