Before embarking on an attic conversion project, it’s essential to consider several critical factors, including the desired outcome and the dimensions of the attic space. If you want to turn your attic into a habitable space, a dormer window can play a crucial role in making your dream a reality. In this blog, we’ll explore the benefits of dormer windows, how they’re built, and what you need to consider when opting for one.

What is a Dormer Window?

The term “dormer” originates from the French word “dormir,” which means “to sleep.” It’s a perfect indication of how dormer windows are used – to bring light into bedrooms built in the attic and increase the required height clearance for habitable attic projects.

How are Dormer Windows Built?

Dormers are usually constructed at the back or side of a house. The process involves cutting out a section of the existing roof and constructing a new “mini roof.” The style of the mini roof is entirely up to you, and the traditional “A” shape is the most common. However, flat roofs are becoming more popular, especially when clad in zinc or lead. Keep in mind that zinc and lead cladding can be expensive, so you may want to opt for a more budget-friendly alternative, such as fiberglass sheeting.

It’s crucial to note that flat roofs are never fully flat, even though they may appear to be. They must be constructed to allow water to run off, especially in Ireland where it rains frequently. The best way to ensure proper water flow is to have the dormer facing forward so that rainfall is directed away from the house instead of back to the main roof. The main roof and mini roof are connected by flashing (usually lead) to divert water to the main gutters. However, it’s worth noting that the addition of a dormer window will require the installation of an additional downpipe.

Insulating a Dormer Window

Improving the energy efficiency of your home should always be a priority. Not only does it reduce your heating bills, but it also supports global sustainability by reducing greenhouse gas emissions. On average, a house loses 20-30% of its heat through the roof if not properly insulated. To learn more about insulation and the grants available through the Sustainable Energy Authority of Ireland, check out their website.

Window insulation is just as important, and in terms of your dormer window, it’s essential to allow an air gap for adequate ventilation. This air gap prevents condensation and moisture buildup that could lead to leaks or damage to the material over time. Vapour permeable membranes are recommended, but extra care must be taken at the window surrounds. Proprietary tapes that are vapour permeable must be used to seal the insulation around the window to prevent mold growth.

What to Consider When Opting for a Dormer Window

If your attic conversion project requires a dormer window, the window design will be reviewed by the planning authority. Here’s a quick checklist of things to consider when planning your dormer:

• Do the materials for the new dormer match the existing main roof and/or walls of the main house?
• Will your dormer window be located below the ridge of the main roof?
• Will your dormer window be located as far back as possible from the eaves line (minimum three tile courses)?
• Is your dormer window aligned in proportion and character to the existing windows and doors?
• Do you have a hipped roof? If so, ensure that the dormer sits below the ridge