Natural light can transform any space, however too little leaves a room gloomy while too much can create glare or overheating. Pitched roof windows are an excellent way to bring the outdoors in, but choosing the right size isn’t just about what looks good. It’s about creating the perfect balance between brightness, energy efficiency, and function. So, how do you work out what size pitched roof window you actually need? Let’s break it down.

1. Consider the Purpose of the Room

Start by thinking about what the room is used for. A kitchen or living space will typically benefit from more natural light to keep things airy and sociable. Bedrooms, on the other hand, may need smaller or fewer windows to maintain a cosy feel (especially if you’re sensitive to morning sunlight).

Quick tip:
Workspaces like home offices benefit from evenly distributed light to reduce eye strain. A well-placed roof window can eliminate the need for artificial lighting during the day. Click the link to view Sterlingbuild’s skylight collection.

2. Know the Recommended Glazing Area

A common rule of thumb in the UK is that the glazed area of your window(s) should be around 20% of the floor space of the room. So if you’ve got a 10m² room, aim for 2m² of roof window glazing.

This isn’t a strict rule, but it’s a handy starting point. Of course, you can adjust up or down depending on how much natural light you already get or which direction the roof faces.

3. Think About Orientation

Where your pitched roof faces plays a big role in how much light your window will let in:

• North-facing: Provides consistent but cooler light throughout the day. Great for studios or bathrooms.
• South-facing: Offers the most sunlight, ideal for brightening darker rooms but can risk overheating.
• East-facing: Gets morning light (the sun rises in the East). Perfect for bedrooms (with black out blinds) or breakfast nooks.
• West-facing: Provides warmer evening light, good for lounges or dining spaces.

Choosing a slightly smaller window for south-facing roofs can prevent overheating, while north-facing slopes might benefit from larger glazing to maximise daylight.

4. Mind the Pitch and Placement

The steeper the pitch of your roof, the shorter the vertical impact of the window. In simpler terms: a large window on a steep roof might bring in less light than expected. The higher up the roof the window is placed, the further the light will travel into the room.

Top tip:
Install your window at eye level for ventilation and views, but consider additional windows or a longer window shape if you're after deeper light penetration.

5. Multiple Smaller Windows vs One Large One

Two smaller roof windows placed apart can often light a room better than one large one. Why? Because the light gets distributed more evenly across the space. It also gives you more flexibility with ventilation and layout inside the room.

If your roof layout allows, consider using more than one window to achieve better lighting coverage.

6. Take Privacy Into Account

Bigger windows mean more light, but also more visibility. If your roof overlooks neighbouring properties, you might want to go for a smaller size, higher placement, or add blinds and frosted glazing for privacy. You can still get great light without sacrificing comfort.