A glass ventilation grille provides fresh air in your home without having to keep opening a window. This is especially useful if you replace old glass with HR++ glass, triple glass or vacuum glass. Your home will then be better insulated and denser, but moisture and polluted air must still be able to escape.
The short rule is: install a ventilation grille when you have better insulating glass installed and the room needs extra ventilation, such as in bedrooms, living rooms, kitchens or rooms with condensation problems. In this article we explain when a ventilation grille is wise, how a grille is installed in glass, what glass deduction means and what you should pay attention to when measuring.
Rule of thumb: better insulation = more conscious ventilation. Always determine a grid before ordering your glass, because the glass deduction makes the window lower and adding it afterwards is usually not possible.
What is a glass ventilation grille?
A ventilation grille is a grille above or in the window through which fresh air can enter. The grille is usually placed above the glass and, together with the window, forms one whole in the frame. Because it is located at the top of the window, the ventilation opening remains neatly integrated into the window. Would you like to immediately see what is possible? View our ventilation grilles.
A ventilation grille can be used for:
- HR++ glass
- Triple glass
- Vacuum glass
- Just double glazing
- Wooden frames
- Plastic frames
- Aluminum frames
Why is ventilation important?
Ventilation ensures that moist and polluted air is removed and replaced with fresh air. This is important for comfort, health and the preservation of your home. Moisture is created every day in the home by:
- Breathe
- Shower
- Cooking
- Dry laundry
- Cleaning
- Plants
- Pets
If that moisture cannot escape, it can settle on cold surfaces such as windows, window frames and exterior walls. Poor ventilation can cause condensation on the inside of windows, mold, stale air, damp spots, black edges on window frames, peeling paint, wood rot and an unhealthy indoor climate. A ventilation grille helps to constantly let in a small amount of fresh air.
Why are ventilation grilles extra important with HR++ glass?
If you replace single glazing or old double glazing with HR++ glass, your home will be better insulated. That is positive, but it also means that the home often ventilates less automatically.
Old windows and frames often had cracks, and those cracks unintentionally provided air exchange. After installing new insulating glass, those cracks partly disappear. This allows moisture to remain in the house for longer. You notice this, for example:
- More condensation in the morning
- Damp bedrooms
- Fogged windows
- Stale air
- Mold in corners
- Wet windowsills
A ventilation grille can prevent or reduce this.
When do you need a ventilation grille?
A ventilation grille is especially sensible in rooms where a lot of moisture occurs or where you often stay for a long time. Consider:
- Bedrooms
- Living rooms
- Kitchens
- Bathrooms with window
- Workrooms
- Children's rooms
- Washrooms
- Well-insulated homes
- Rooms with condensation problems
Ventilation is extra important in bedrooms. During the night you exhale a lot of moisture. If the windows remain closed and there is no grille, you often see condensation on the inside of the window.
When is a ventilation grille less necessary?
A ventilation grille is not always necessary. Sometimes there is already sufficient ventilation available. A schedule is less necessary when:
- Mechanical ventilation is already present
- The room already has good ventilation
- There are existing grilles in other windows
- The window can be opened often
- The space is rarely used
- It concerns a storage room, garage or unheated space
- There are no moisture problems
Please note: Exhaust alone is not enough. If air is extracted, fresh air must also be able to enter. A ventilation grille can ensure this.
Ventilation grille for condensation on windows
Condensation on the inside of windows often indicates too much moisture and too little ventilation. A ventilation grille can help. Condensation occurs when warm, moist air hits a cold surface. This happens more quickly with poorly insulating glass, but condensation can also form with HR++ glass if the humidity is high.
A ventilation grille helps because:
- Moist air is replaced faster
- Fresh air comes in
- The humidity drops
- Windows fog up less quickly
- Mold has less chance
Please note: You cannot solve condensation between the glass panes with a ventilation grille. Then the insulating glass is leaking and the window must be replaced. You can read more about this in condensation on windows: inside, outside or between the glass and recognizing and replacing leaking double glazing.
Ventilation grille per room
Bedroom window
A bedroom is one of the most important places for ventilation. You spend many hours there and produce fluid while sleeping. Without ventilation, the air can quickly become humid and stale. A ventilation grille in the bedroom helps against:
- Windows fogged up in the morning
- Stale air
- Damp walls
- Poor air quality
- Mold around window frames
- Headache or a tight feeling when waking up
When replacing bedroom window glass, it is therefore smart to immediately check whether a grille is needed.
Kitchen window
A lot of moisture is created in the kitchen by cooking. Grease and odors also linger more quickly if ventilation is poor. An extractor hood helps, but fresh air supply remains important. Especially in well-insulated homes, a ventilation grille can help to maintain air flow. A grille in or above the kitchen window is useful for:
- A lot of cooking
- Open kitchens
- Condensation on windows
- Insufficient supply air
- Mechanical extraction
- Scents that linger for a long time
Bathroom window
A lot of moisture is created in a bathroom by showering and bathing. Moisture is usually removed via mechanical ventilation or a window that can be opened. A ventilation grille can help, but it must be used properly. The moisture load in bathrooms is high, so choice of materials and placement are important. NB:
- Choose a suitable grille for damp areas
- Make sure the extraction works properly
- Prevent water from entering directly into the grille
- Ventilate extra after showering
- Keep sealant seams and window frames dry
A grille alone is not always sufficient for a bathroom. Good extraction remains important.
How is a ventilation grille installed in glass?
A ventilation grille is usually placed above the glass. The window is then lowered so that the grille fits above it. The combination consists of:
- Insulating glass
- Ventilation grille
- Possibly a coupling profile
- Glazing beads
- Kit or rubbers
- Frame
The grille is not simply sawn into an existing window afterwards. With new glass, the glass size is immediately adjusted to the grille. That is why you must determine before ordering whether you want a grille. When assembling insulating glass, take this into account immediately, so that the glass size and the grille match each other.
What does glass deduction mean for a ventilation grille?
A ventilation grille takes up space above the glass. The window must therefore be ordered lower. This reduction is often called the glass deduction.
Example: you measure a rebate height of 1200 mm. Normally you would subtract 8 mm for slack. Then you also subtract the glass deduction from the grid.
| Step | Height |
|---|---|
| Rebate height | 1200 mm |
| Normal deduction (slack) | −8 mm |
| Intermediate size | 1192 mm |
| Glass deduction grid | −80 mm |
| Order height glass | 1112 mm |
The exact glass deduction varies per grid. Always check this for the selected type of ventilation grille.
How do you measure glass with ventilation grille?
For glass with ventilation grille, first measure the normal rebate size. Then calculate the glass size including grid:
- Measure the width of the rabbet in three places.
- Use the smallest width measurement.
- Measure the height of the rabbet in three places.
- Use the smallest height measurement.
- Subtract normal placement clearance.
- Subtract the glass deduction of the grille from the height.
- Check whether the grille fits in the frame.
Always measure in millimeters. Please note: the width of the grille must usually be equal to the glass width or matched to the frame system. A detailed explanation can be found in measuring glass.
Does a ventilation grille fit in every frame?
Not always. Whether a ventilation grille fits depends on the frame, the available space and the way in which the glass is placed. Check:
- Rebate depth
- Available height
- Frame type
- Glass thickness
- Glazing beads
- Space for the grille
- Inside or outside
- Operation of the grille
- Direction of rotation for rotating windows
- Possible sun blinds or insect screens
You have to be extra careful with rotating windows. The grille makes the whole thing higher and heavier, and the controls must remain accessible.
Wooden frame
Ventilation grilles can often be used in wooden frames. Wood is usually easier to adapt than plastic or aluminum. Pay attention to the condition of the wood, the rebate depth, the glazing beads, the drainage, the paintwork, the connection of the grille and the risk of moisture in the event of poor installation. With old wood, it is wise to immediately check for wood rot and bad sealant seams.
Plastic frame
With plastic frames you are dependent on the profile. Not every plastic frame is equally easy to adjust. Pay attention to the maximum glass thickness, the available glazing beads, the space for the grille, the profile height, the rubbers, the method of clamping and the warranty of the frame. Sometimes a grille above the glass is possible, sometimes a separate grille in the frame profile or another ventilation solution is better.
Aluminum frame
The option also depends on the profile with aluminum frames. Modern aluminum frames can often be combined well with insulating glass and ventilation grilles, but old profiles sometimes have limitations. Pay attention to the thermal break, the risk of condensation, the glazing bead space, the grille height, the rubbers, the connection and the mounting method. A poorly insulated aluminum frame can still feel cold despite good glass. Therefore, look at the entire window, not just the grille.
Which type of ventilation grille do you choose?
There are different types of ventilation grilles. The right choice depends on comfort, sound, operation and appearance.
| Grid type | When useful? |
|---|---|
| Standard ventilation grille | Basic ventilation |
| Self-regulating schedule | Adjusts air supply according to wind pressure |
| Sound-absorbing grille | On busy roads or city noise |
| Grid with filter | With dust, pollen or polluted air |
| Narrow grid | When appearance is important |
| Manually operated grille | Simple operation |
| Grid with cord or rod | With high windows |
For homes on busy streets, a sound-absorbing grille is often wise. Otherwise, the grille can become a weak spot for sound. View the range in the category ventilation grilles.
Does a ventilation grille affect noise?
Yes, a ventilation grille can let sound through. Glass can be sound-resistant, but if the grille lets sound through, you will still notice it. Do you live on a busy road, railway line or in a city? Then look at a sound-absorbing ventilation grille. NB:
- Default grilles mute limited
- Sound-absorbing grilles are often larger or more expensive
- Gap sealing remains important
- Ventilation and sound insulation should be considered together
Do you mainly want less noise? Then choose not only sound-insulating glass, but also a suitable grille.
Does a ventilation grille affect insulation?
A ventilation grille allows air to pass through. As a result, it insulates less well than a completely closed window. Nevertheless, ventilation is necessary for a healthy indoor climate. Good grilles are designed to provide controlled ventilation without unnecessary drafts. When it comes to comfort, please note:
- Self-regulating effect
- Correct capacity
- Placement above the window
- Operation
- Draft restriction
- Combination with mechanical ventilation
A well-chosen grille provides fresh air without having to open the window all the time.
Ventilation grille and subsidy
With a subsidy for insulating glass, a ventilation grille can be part of the project, but the grille itself is usually not assessed in the same way as the glass. For subsidies, the insulating glass surface and the performance of the glass are particularly important. NB:
- The glass must meet the requirements
- The surface area must be specified correctly
- The invoice must be clear
- The grille can influence the total glass size
- Installation must be carried out professionally
Always check the current subsidy conditions if you want to apply for a subsidy. You can read more about this in ISDE subsidy for insulating glass.
Common mistakes with ventilation grilles
- Forgotten grille with new glass — once the glass is ordered, you cannot simply add a grille to the same window later.
- Forgot glass deduction — a grille takes up height; the window must be ordered lower.
- Only insulate and do not ventilate — better insulation without ventilation can cause moisture problems.
- Choose a standard grille if there is a lot of noise — a sound-absorbing grille is often better on busy roads.
- Enter wrong size — always measure the rebate size and check the exact deduction of the grille.
- Place the grille in a room where there is no extraction — ventilation works best if the supply and exhaust match.
- Forgot the controls — with high windows you should still be able to open and close the grille.
Checklist: do I need a ventilation grille?
- Do I replace old glass with HR++ glass?
- Will my home become denser than before?
- Do I have condensation on the inside of windows?
- Is the room often damp?
- Is it a bedroom?
- Is it a kitchen or bathroom?
- Is there mechanical extraction available?
- Is there sufficient supply air?
- Don't want to keep opening the window?
- Do I live on a busy road?
- Do I need sound insulation?
- Does the grille fit in my window frame?
- Do I know the correct glass deduction?
Do you answer "yes" multiple times? Then a ventilation grille is probably wise.
Conclusion
A glass ventilation grille ensures a constant supply of fresh air. This is especially important when you replace old glass with better insulating glass, such as HR++ glass, triple glass or vacuum glass. Your home will then be better insulated, but moisture must still be able to disappear. Ventilation grilles are especially useful in bedrooms, living rooms, kitchens and areas with condensation problems.
With a grille above the glass, you must take the glass deduction into account: the window becomes lower because the grille takes up space. Choose the schedule that suits your situation. A sound-absorbing grille may be wise for busy roads, and controls are important for high windows.
Do you want to order new insulating glass? Then immediately think about ventilation. Adding a grille afterwards is usually not easy, while it can be neatly included immediately with new glazing.
Read further and arrange immediately:
- View the ventilation grilles and put together your insulating glass with grille
- Consider vacuum glass for maximum insulation in existing window frames
- Are you unsure about thicker glass in your existing frame? Read thicker insulating glass in an existing frame
- Go to glass to size to order your window with the correct glass deduction