1. Must-knows about roof windows

Whether youd like to install new pitched roof windows or change the existing ones, theres no doubt theyll affect the overall appearance of the room, energy efficiency, but also your homes value. This is why its important youre aware of all the options available.

1.1. Roof slope

Different slopes require different hardware to be installed and different installation methods. An installation set should secure waterproof pitched roof windows. The installer you choose will know which set and what type of windows to use for your roof, structure, and roofing and which method to employ.

1.2. Where to install them?

When deciding on a suitable place for your roof window, pay attention to the suns movement. If you dont have the luxury of making such choices, and that theres only one facing direction available, then the most important question is what type of window you should install to get enough daylight.

North-facing windows never receive enough light, so if you plan to install one, make sure it’s pretty large to allow as much daylight and heat as possible. East-facing windows will be exposed to direct sunlight in the morning, which can be ideal for a kitchen or bedroom, depending on your preferences. West-facing windows receive sunlight in the afternoon, so theyre a good choice for the living room. South-facing windows receive light throughout the day, so theyre the best option for the room where youll spend most of your time.

1.3. Insulation and ventilation

State-of-the-art roof windows include an innovative ventilation solution allowing you to enjoy fresh air even when the window is closed. Some windows feature small openings, i.e. vents allowing air to flow through filters, without actually needing to open the window. Theres also an insect screen, which especially comes in handy in the summer, when theres a myriad of creepy-crawlies. Different glazing solutions will affect a windows thermal insulating properties. The letter U stands for thermal transmittance, so dont forget to check it when choosing a window. The lower the U-value, the better the thermal insulation, meaning that the interior is more protected.

1.4. Shading solutions

Roof windows allow 30% more daylight into the room than regular ones. This is usually an obvious advantage, but sometimes, you need to reduce the glare to make staying in a room more comfortable. Most roof window manufacturers offer matching shading solutions. There are also venetian blinds which reduce heat loss for about 20%. Then there are blackout blinds, which completely block out all light, so theyre ideal for bedrooms.

2. Hire a professional

Installing a new window or replacing an existing one is not a one-man job. These works require expertise, skill, and experience, and an extra pair of hands. A solo experiment can end up costing you a fortune, both financially and emotionally. Its a good idea to learn about all available aspects and possibilities before you start a project. This will also help you reach an agreement with your contractors more easily.

3. Types of roof windows

When choosing a roof window, the most important thing is to find an exact fit for your roof and needs. Heres an overview of different types of windows and their characteristics to help you with your decision making.

3.1. Classic roof window

With this type of window, the handle is positioned either at the top or at the bottom. If the handle is placed at the top, you can put furniture under the window and still have enough space for handling and cleaning it. This type rotates around its axis, so you can flip it when its cleaning time.

3.2. Panoramic roof window

These are top-hung windows, so you must allow clear access. For safety purposes, the distance between the bottom side of the window and the floor should be at least 110 cm, but not more than 150 cm to keep them within reach. Panoramic windows let in plenty of light, heat, and fresh air, so theyre very energy efficient. These windows will give your loft an air of openness and comfort, and most certainly, a nice view.

3.3. Grouped roof windows

To make your room look spacious and airy, group several smaller windows together. You can arrange them horizontally or vertically. The original purpose of windows is to provide a connection between the interior and exterior, and give a room a more natural look. If your sloped ceiling is high or at least higher than usual, then you might consider installing roof windows above regular ones, and were sure this would make all the difference.

3.4. Roof balcony or terrace

Just because its an attic, it doesnt mean you cant install a balcony or terrace. This would certainly make the room look more spacious and help you enjoy the sun and relax. If you take this option, the best arrangement is to pair a top-hung roof window with a small outswing door under it. You should also add a safety railing. A roof balcony provides more light, fresh air, but also a direct contact with the outdoor world. You can always find a part of roof with no particular purpose and turn it into a balcony or terrace.

3.5. Special roof windows

You can also find the following types of windows on the market:

- lines for non-residential attics,

- inspection roof windows providing access to the roof,

- windows featuring trickle vents and providing access to the roof,

- flat-roof domes,

- safety-compliant smoke ventilation windows,

- skylights for flat and corrugated roofing and sun tunnels for flat roofs.

4. What materials do you need for roof windows?

4.1. Lacquer-coated wooden frames

Lacquer-coated and impregnated wood is a very popular solution for roof windows. Frames for these windows are usually made of the pine wood and oak wood, deeply impregnated before the assembly, and then coated with an environmentally friendly acrylic lacquer. Wooden windows are suitable for dry rooms and its advisable you keep them small. Wooden frames are usually protected with aluminium profiles on the outside.

4.2. Polyurethane-coated wooden frames

Polyurethane-coated wooden frames are a good choice for damp rooms, since theyre resistant to water and UV radiation. Theyre made of the pine or oak wood, and they come at a somewhat higher price than lacquer-coated frames, as theyre more durable.

4.3. PVC frames

PVC windows are in high demand. Theyre made up of PVC profiles and comprise several chambers, which prevent the so-called thermal bridging. These windows can be large in size, since theyre more lightweight than wooden ones, although theyre reinforced with aluminium and steel. Theyre great for mould-prone rooms, such as bathroom, kitchen, pantry, etc. They come in different shapes and colours, so youll surely find one that fits you even if youre a demanding customer.

4.4. Aluminium frames

Aluminium is used for large-sized roof windows or those used for not so common purposes (e.g. moving balcony doors, retractable balconies, etc.). Whats most important is that your aluminium roof window prevents thermal bridging.

5. Glazing options for roof windows

5.1. Double glazing

Double-glazed roof windows with an air chamber are a great and affordable option. This window can also come with an exterior protective glazing resistant to hail and burglar-proof. The thermal transmittance of this glazing is Ug=1.0 W/m2K.

5.2. Triple glazing

Triple-glazed windows include two layers of air or gas (argon or krypton). This is the most widespread type of glazing today. The thermal transmittance of this glazing is Ug=0.5 W/m2K.  

5.3. Quadruple glazing

This type of glazing is very secure and efficient, since it features noble-gas-filled chambers. Truth be told, this is the most expensive type of glazing, but only in the short run, since theyll save you lots of money on heating in the long term. This glazing meets passive house and low-energy standards. The thermal transmittance of this glazing is just Ug=0.3 W/m2K.

6. Installation of roof windows

Installing roof windows requires much more specialist knowledge than is the case with regular ones, as the former are exposed to literally all outdoor elements. Also, making a roof opening can cause heat loss. Given how intricate a roof structure is, RAL installation, which reduces heat loss, cant be applied in this case. However, if the work is done professionally and properly, heat loss can be minimized. This entails using an exterior insulation collar, waterproof flashings, a vapour barrier installed from the inside acting as a sealant that protects the structure from water ingress.

6.1. Where to install roof windows?

Roof windows should ideally be situated 90–200 cm above the floor level. Window height from floor depends on the knee wall, the height of the ceiling and occupants. As a rule of thumb, any window, including roof windows, should be installed in a place where its easily handled. Its equally important that a window provides an uninterrupted view, regardless of whether youll spend most of your time sitting or standing in this room. The width of a roof window depends on the distance between the posts. You should also ensure that you minimize alterations to the roof structure. Installing a roof window on a slanted roof requires the use of battens, while in case of flat roofs, the window is installed on the beams.

6.2. Roof window installation kit

To prevent poor workmanship and various other problems, use of a special installation kit is always advisable. This kit consists of a custom-made insulation collar, which is fitted into the aperture before the window is installed. This creates an optimal insulation layer between the window and roof structure and minimizes heat loss. The next step involves slotting the window into the insulation collar. The kit also contains custom-made flashings designed to prevent ingress of water and protect the window against condensation on the roofs underside. Flashings are attached to the window frame, and a vapour permeable underlay membrane is placed around it. The third member of the kit is a vapour barrier. Its simply laid around the window to stop ingress of water and vapour into the structure, thus protecting both the insulation and the roof structure. Its also custom-made.

6.3. Taking care of the inside