Windows

 Last year in November, I wrote a blog on doors. Today is something of a companion piece, where I look at windows - their materials, proportions and placement in a room. The position of the windows in a space has a number of consequences on the comfort and usability, and often the designer needs to weigh these up where these factors do not coincide. When I was a student, we were encouraged to include typical furniture layouts in our designs, to help us to entrench this in our thinking. For example, a window in the centre of a wall can leave space on either side for tall furniture, while one closer to the corner is more limiting.

A centrally placed window often gives maximum flexibility for furniture layouts

On the flip side, though, the centred window often does not allow for optimal ventilation, as the fresh air tends to form a tunnel from the window to the door, especially if the door is in the centre of the opposite wall. A centrally placed window also tends to dominate the room. If the view is good, this can be a bonus, but I remember flat-hunting with one of my daughters and one of the bedrooms had a central window overlooking a parking lot with a skip-waste as the centrepiece!

Windows placed close to an adjacent wall tend to create much better daylighting in a room, as the natural light washes down the side, so very bright within the actual window and then a light gradient radiating outwards. A centred window, especially if it is quite small, can sometimes create a harsh light, casting the adjacent wall into shadow.

Light is cast down the wall on the right

The Cape Dutch craftsmen created a similar gradient effect by placing the window frame on the very outer face of the wall, and then splaying the deep reveals (their walls were typically half a metre thick). These were smooth plastered and painted white, to reflect the daylight and create this gradient of light.

Daylight in a Cape Dutch house

If you want to adapt an existing window, one way is to have a central blind with two side panels - I did this in a room for my older child when she was a newborn. The central panel was of translucent fabric and was always down, allowing for a large area of filtered light. The side panels were adjusted up or down according to the outside light and her routine, and the final touch was some heavier curtains to lock out the daylight entirely for when she was napping.

The proportions of a window can also affect the quality of light in a room. In the past, before the invention of concrete beams and lintels, windows were kept narrow and tall, so that it was easier to carry the load of the wall above. This creates a narrow band of light, which moves across the room throughout the day, an ideal situation for an east or west facing wall, where the direct sun can be very harsh in summer, so it limits the time that the room will be uncomfortably hot. In the southern hemisphere, large windows in a south wall offer a very consistent light throughout the day, ideal for a museum, library or an artist's studio, but these can be freezing in winter, as glass is very good at conducting heat. For the north wall, the best is to use some form of shading for big windows, as I describe in my blog about pergolas.

In the past, window frames were almost always made of wood, a very effective choice as it tends to expand and contract with temperature variation at much the same rate as glass. Wood also tends to give quite a robust aesthetic, although in the 19th Century, British carpenters could achieve very slender frames using hardwoods imported from the Far East, such as Burmese teak. Wood is an excellent choice in places that have a fairly humid climate all year round, but in inland areas, they need regular maintenance to protect the wood from drying out and splintering or cracking.

Wooden windows and sliding doors with quite robust frames

The invention of steel window frames in the 1920s has made this the default for most homes in the interior of South Africa for this reason. In the 1930s, steel windows were seen as the height of modernity, often used with concrete beams so that they could be much wider than before. Steel windows have their own problems, though. The one that has most affected the 1930s building I live in is that, over the years, they have been repainted several times, so they no longer close as tightly as when they were first installed. This is a problem in winter, with icy drafts, but the real killer for many of my neighbours is that the badly fitting frames can no longer exclude the noise of our busy street. As a result, several owners have replaced theirs with aluminium frames, some even double-glazed. 

Older steel windows below and new aluminium frames above

This has resulted in a bit of a patchwork aesthetic, as the glass panes in the new windows are quite a bit bigger, and the aluminium frames are thicker. This is something to think about if you are considering replacing some of your windows - generally it is most effective if you can replace all the frames in the whole house, but if this is not possible, at least consider changing all the windows on one wall for an elegant effect.