Do not start with the visible glass dimensions alone. First locate the type code of the existing roof window, usually shown on a plate or sticker attached to the sash. Record the brand, type and size code, then measure the external dimensions as a check. A recognised size code can help identify a suitable replacement, but the actual situation must still be verified.

Next, inspect the roofing material and existing flashing. A new, matching flashing is normally installed when replacing a roof window. Also check the condition of the roofing membrane, insulation, battens and internal lining. A window with the same nominal dimensions does not automatically mean that the opening or internal finish will require no adjustment.

A PVC roof window is particularly useful when low maintenance and moisture resistance matter. HR+++ triple glazing is generally selected for a heated room, while HR++ may suit a standard renovation. Summer comfort should also be considered on a roof slope with strong sun exposure.

The right dimensions depend on the spacing between structural elements, the desired amount of daylight, the room height and the view. Position the lower edge so that operation and the view remain practical. At the top, consider access to the handle and the internal lining.

Daylight is not determined by the total glass area alone. A higher window brings light deeper into the room, while several windows can distribute light more evenly. The shape of the reveals also makes a difference: a horizontal top reveal and vertical bottom reveal improve light distribution and air circulation across the glazing.

Have any changes to load-bearing rafters or purlins assessed by a structural professional. Always use the dimensions in the installation instructions; the external product dimensions, order dimensions and required structural opening are different measurements.

The flashing drains rainwater around the roof window and connects the window to the roofing material. Select it according to the window series, window dimensions, roofing material and roof pitch. Flashing for profiled roof tiles is not automatically suitable for slates or flat roofing materials.

When ordering, check that the size codes of the window and flashing match. During installation, follow the specified overlaps and correctly connect the weatherproof membrane to the roofing. The Intura Vista differs from many standard models because its flashing is already integrated.

Condensation on the inside occurs when warm, humid indoor air meets a cold surface. It does not immediately mean that the roof window is leaking. Limit moisture production, ventilate the room and maintain airflow across the glazing. Bathrooms, bedrooms and newly plastered rooms in particular can temporarily contain a great deal of moisture.

Correct insulation and an airtight connection around the frame prevent thermal bridges and moisture movement into the roof construction. Ideally, position a heat source beneath the roof window and avoid completely blocking the airflow with a deep windowsill or closed curtain. Moisture that remains visible between the panes may indicate a failed insulated glass unit.

Integrated ventilation in the roof window can supply fresh air while the window is closed. Capacity and operation vary by model. A ventilation position is useful, but it does not always replace the home’s ventilation design or mechanical extraction in a bathroom and kitchen.

Maintain continuous ventilation in accordance with the home’s design and open the window for additional purge ventilation when moisture or heat must be removed quickly. Keep ventilation openings clean and unobstructed. In a bedroom, a combination of background ventilation, an opening window and suitable insect screening is often the most comfortable solution.

The PVC profile does not require painting. Clean it with lukewarm water and a mild, non-abrasive cleaner. Avoid aggressive solvents and abrasive sponges. Keep the external channels and drainage areas free of leaves, moss and dirt.

Periodically check the seals, hinges, operating components and the flashing connection. Follow the model-specific instructions for lubrication and adjustment. A centre-pivot sash can generally be rotated so that the outside pane can be cleaned safely from indoors.

A roof window may be permitted development under certain conditions, but the rules depend on the country and local authority, its position and dimensions, and whether the building has listed or protected status. Different requirements may apply to a roof slope facing a road or other public area.

Check the current national and local planning rules before starting work and ask the relevant authority when in doubt. Prior approval is often required for listed buildings and protected areas. Building requirements for structural safety, insulation and weathertight installation still apply regardless of planning status.

• Measuring only the glass instead of checking the type code and external dimensions.
• Selecting flashing that does not match the window dimensions or roofing material.
• Failing to check the permitted roof pitch for the specific model.
• Insufficient insulation or an inadequate airtight connection around the frame.
• Ignoring solar exposure, blackout requirements or insect screening.
• Changing the opening without assessing the supporting structure.
• Using a roof window as the only ventilation provision in a humid room.

If in doubt, have the complete product configuration checked before ordering. Include dimensions, roof pitch, roofing material and clear photographs of both the inside and outside.