When it comes to extensions, many of our clients want light-filled open plan rooms, which connect to their outside space. It is also important to ensure that light still gets into the interior of the house. This is easy to achieve with well-placed skylights, bi-folding doors and floor to ceiling windows. But what is the best glass to achieve light and airy spaces and how do you stop your new extension turning into a green house?

Glass for Skylights and roof lights

When choosing the type of glass for your skylights, safety is paramount. So, the ideal specification is to use what is known as tempered or toughened glass. This type of glass is usually used, at the very least, in the outer pane, but can be used for both panes if double glazed; it is less likely to smash and, if it does, it will shatter into many fragments, rather than larger, more dangerous, shards.

You can also opt for laminated glass; this is more often used for security purposes, because it cracks, rather than shatters, on impact. If you have double, or even triple, glazed skylights, laminated glass is usually used on the inside pane as it can stop an outer breakage from falling in. Another advantage of laminated glass is that it has mild sound proofing qualities.

There are rules and regulations on the U-Value level that can penetrate through skylights, currently, the U-value stands at 1.6W/m2/K. If overheating is an issue, for example, if you have a south facing home, you can use solar control glass. This type of glass can reduce solar glare, but glass that is tinted blue or bronze can also do the same job; however, tinted glass does admit less light than ‘clear’ glass. 

If your skylight or roof lights are difficult to get to, you can opt for self-cleaning glass, which works by breaking down dirt, making it easier for it to be washed away by rain.

Glass for bi-folding doors

When opting for bi-folding doors, you need to think about heat loss, heat gain and noise as well as security and safety. Glass can contribute extensively to heat loss, so to ensure your new extension does not become a large fridge in winter, it is recommended that your bi-folding doors have a thermal barrier between the inner and outer components. A thermal barrier will also help to reduce condensation and conduction. Noise is always going to be a problem when you live in a city; while parts of London can be quiet and peaceful, this is not a given. Blocking out external noise has a lot to do with how the glass is sealed within the individual panels as well as the glass type that you choose.

Glass walls

Extensions are not cheap – so you don’t want to build one only to find it’s a glorified green house in the summer. Getting too much sun and heat is known as passive solar gain, and there are several ways to reduce this. One way is to make use of the latest glazing technology, such as specially coated glass that works to reduce solar gain as well as meeting the U-value standards. Other ways to reduce solar glare include adding a roof overhang, a sun breaker, brise soleil, or ensuring that the orientation of the extensions does not face south – this is, of course, not always practical.


If you want to add an extension to your London home, contact Simply Extend today for a free site survey.

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