VELUX Articles

Written by Charlie Luxton, September 26, 2017
Topics: inspiration

Daylight is one of the holy grails of modern living. Bright well-lit spaces have clear health and well-being benefits.  In short they make us feel good and unsurprisingly this is something we want from our homes. 

In this quest for light, roof windows are an especially powerful tool because they provide twice the amount  of daylight compared to a similarly sized vertical window.

When that sun is shining - or even if it is just a fairly bright day - not only does the daylight makes us feel good, it also provides a free source of heating. As sunlight passes thought glass it creates warmth, called solar gain. You can really feel this in a freezing cold conservatory or greenhouse on a cloudy winter day that then becomes lovely and warm if the sun comes out.

Increasingly solar gain is being utilised as a source of heating in buildings. In fact when I’m designing houses with triple glazing and huge amounts of insulation, combined with a bit of solar gain, keeping warm is not something that is at the forefront of my mind. The house will stay warm with almost no heating all year.

What I need to focus on is the potential for overheating because while modern buildings need very little heat we still want lots of daylight. This is OK for most the year but a juggling act starts in summer when you have to try and balance these things without cooking the occupants! 

It’s not just overheating that is a potential issue when you have lots of daylight; glare can be an unwanted by-product too. Whilst undoubtable it is a ‘first world problem’ squinting at a laptop or phone is unpleasant or not what you want when you are lounging around your beautifully new extension or home. Unless you‘re up for wearing sun glasses inside you’ll need to control glare on sunny days.

It is not without irony that having spent a whole lot of effort getting daylight into a home you need to expend more controlling it! However if you consider how the weather, and therefore available solar energy, varies day to day let alone through the year it make sense that a building must be able to adapt. 

Blinds are without doubt one of the best ways to achieve this optimisation for both solar gain and glare. Allowing the ‘goldilocks’ moment of just the right internal temperature and light levels to be maintained whilst using as little energy as possible. 

While the two issues of glare and overheating are interlinked controlling them really requires two separate roof window blinds solutions. Internal blinds to control glare and external awning blinds to control solar gain.

Internal mesh blinds either manually operated or motor controlled, take out just enough light to allow for comfort on a bright day but can be retracted on a dull day to boost light levels sand make you smile!  

For solar gain it is best to have awning/roof blinds on the outside of the roof window. Once light has got through glass and into a building internal roof blinds only reflect about 10-20% of the light/heat back out. Externally mounted blinds stop the solar gain entering the building all together. These should be electrically controlled and preferable attached to a thermostat so that if the building starts heating up while you are out, the roof blinds will automatically lower and keep your house nice and cool. You can also set roof blinds on timers so that in the summer they are down while you’re at work but have opened for your return to a bright welcoming home.

It can seem too complicated and too much hassle when you’re in the thick of a build project to think about these issues. But an element of control over your roof windows using blinds can be the key to a more comfortable energy efficient home.

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