Londoners living in high-density areas are, not surprisingly, suffering most from alarming rates of deficiency of vitamin D — the sunshine vitamin vital for bone strength. Seasonal Affective Disorder, or SAD, again caused by lack of light, affects about seven per cent of people in the UK and is a deep and debilitating depression.
© Nick Kane
It's an important issue for many Londoners because the city has so much accommodation converted from Victorian and Edwardian homes, which can create dingy basement or ground-floor flats with light-starved side returns.
The London Development Agency made improved natural light a benchmark of design in a housing standards document published in 2010.
But while it is easy for new-build properties to incorporate more light into their designs, what can you do if you live in an older house and you're not starting from scratch? Luke Tozer, director of architects' practice Pitman Tozer, says that it is a lot easier to improve quality of light than people might think.
"Along with shelter and warmth, natural light is a fundamental element that every house must provide," he says. "A room bathed in natural light lifts the spirits and is something everyone enjoys.
"Period houses have large sash windows that give good light to rooms to the street but often the rear and the stairs are gloomy. This can be solved by adding large glazed doors on to the garden and a roof light over the stairs."
Luke's own Bayswater house, which he designed, is called the Gap House because it sits on a plot a mere 2.3 metres wide, sandwiched between two listed buildings. But the four-bedroom home maximises light and space by stacking bedrooms at the front, while reception rooms fall in a "cascade" effect at the rear. The only rooms without natural light are wetrooms or storage.
© Luke Hayes
Another Pitman Tozer project is the Upside-Down House in Notting Hill, where the traditional house lay-out was transposed by placing bedrooms at ground floor and living rooms above.
This option costs slightly more but can be relatively easily done as long as water outlets are kept roughly in the same place — for example, a kitchen goes where a former bathroom was and vice versa.
Here, Luke outlines three other ways people can lighten up at home.
1 TOP LIGHT
A horizontal glazed surface (often called a roof light or skylight) lets in many times more light than an equivalent-size vertical window. There's a huge variety of roof lights, from those you can walk on, slide away or tilt, to those which utilise a sun pipe. Simply adding a roof light at the top of a stairwell, for example, can radically transform how the space feels. The ability to look up and see the sky from inside also provides a psychological boost, and gives a sense of openness and connection to the outside, even on a cloudy day.
High-level windows, or clerestory windows, often expose a greater amount of sky even though they are vertical like traditional windows. Combined with a sloping ceiling this can funnel light down into spaces that would otherwise be gloomy. They also give an illusion of space because the room feels higher. High windows also allow warm air to rise out in the summer and cool air to fall down, cooling the space. Suppliers: Glazing Vision (glazingvision.co.uk); Velux (velux.co.uk); Rooflight Company (rooflightcompany.co.uk).
2 CHANGE THE FRAMES
If you are stuck with existing window openings (and even if you're not) it's still possible to significantly increase the light by reducing the size of the frames. Traditional hardwood sash windows or Crittall windows were very good at this but now there are even sleeker frameless glass windows and doors around.
If you live in a conservation area you will need to apply for planning consent to change your windows and always take care to choose windows that allow you to naturally ventilate the space. Suppliers: skyframe.com
3 CHANGE THE GLASS
It is possible to vary the amount of light coming through a window by changing the glass. Some types make the light appear whiter and reflect further into the room. Also consider putting glass in doors, particularly front doors with gloomy halls. If security is an issue (though toughened glass is difficult to smash), consider putting glass around and above the door frame, or use frosted glass. It lets less light in but it's better than no light at all. In a listed building, changing the glass requires Listed Building Consent.
Windowsills: large, brightly coloured or reflective windowsills reflect natural light deeper into the room, as do light or glass shelves.
Mirrors: a mirror is a wonderful way of giving the illusion of light and space, particularly if added above eye level, so that the space seems to continue into the distance. Also try to position mirrors opposite a window so that the light is reflected. This also works well at the end of a garden to create a sense of extended space.
Orientation: if you are able to influence the window positions at the design stage, make sure you have as many south-facing lights as possible as they let in more light than north-facing ones. Try to maximise the number of windows on the south-facing side of the house — but avoid overheating the room. Reflective films can help control and reduce the amount of light if summer overheating is a problem. Suppliers: Purlsol (purlsol.com).
Splayed openings: if your window spaces are small, make sure you have splayed openings, which is where the inside window surface is greater than the outside window gap. It allows the light to spread over a wider area, making the room brighter.
Clean your windows: it's obvious but particularly in cities, the amount of dirt and grime that accumulates on windows can have a huge effect on the amount of natural light that gets through them. If the windows are hard to reach or you don't want to clean them yourself, it's worth considering self-cleaning glass that does the job for you. But be warned, this is not a cheap option and you might be better off employing a window cleaner. Supplier: pilkingtonselfcleaningglass.co.uk.
* Pitman Tozer Architects, 103 Great Western Studios, 65 Alfred Road, W2. (020 3214 3255; pitmantozer.co.uk)