My article on structural glazing can be found in August's edition of Self Build & Design in a special glazing supplement.
STRUCTURAL BUILDING AND EXTENSIONS
When is a wall not a wall? When you can see through it? Or is it still defined as a wall by the mere fact that it divides or protects a space? Glass is still a physical element; after all we can’t walk through it…..yet!
With glass no longer being the captive of a frame or reliant on the wall it resides in, it has become a walling material in its own right. This is no new thing of course, with the likes of great architects Mies van de Rohe and Philip Johnson using glass in huge expanses to create floating roofs and transparent houses, which seamlessly blended into the landscape. It is, however, only in more recent years that we have seen the growing trend for structural glazing in the UK domestic market both on new build houses and extensions.
The real attraction of glass is its transparency and its ability to bring the outside in. Transparent walls enable you to feel at one with your surroundings unlimited by frames and solid walls they can give a real sense of openness whilst also allowing the maximum amount of daylight into habitable spaces. What better feature wall than the changing skies and seasons!
Structural glazing the long time preserve of the high street shop front or prestigious office has really broken through into the residential market, which has been dominated by UPVC conservatories for far too long. Structural silicone bonding has been around for over 30 years giving architects the freedom to form vast fully glazed facades.
The structural grade silicone effectively acts as glue, which bonds the glass to the structural frame (often glass itself), obviating the need for intrusive mechanical fixings and enabling the design of seamless glass surfaces. It is the unique properties of the silicone that allow this to work being both strong and flexible and also weather resistant.
This clever sticky stuff gives us the opportunity to create transparent masterpieces in our back garden, contemporary glass gems, which sit elegantly alongside our traditional brick dwellings. There are various companies who specialize in structural glazing systems specifically for the residential market, such as www.glasspace.com, www.clearliving.co.uk,
So how do you stay warm behind your walls of glass, or even, how do you stay cool with the sun blazing in? By using a low e glass which is basically a heat resistant glass with a metallic coating applied on one side the sun’s energy is allowed to pass through from the outside whilst heat loss is resisted from the inside. This forms part of a sealed double or triple glazed system, which often has a gas filled cavity to make the unit more efficient.
Solar control can also be in the form of physical shading from overhanging roofs or even trees but for a more regulated approach consider blinds some of which can be neatly incorporated into your double glazed unit.
If this all seems a bit Heath Robinson, research is currently being carried out into glass, which can respond to external conditions. Photochromic glass has been used for some time in sunglasses. As light intensity increases molecules within the glass spread out to prevent sunlight passing through. The disadvantage of this is that on a sunny winters day sunlight will be prevented from passing through the glass and the occupants will not benefit from the solar gain.
Electrochromic glazing is looking like the hot contender to solve this problem as it’s controlled by an electrical current rather than the sun’s rays. This can be manually operated or linked into the buildings management system. The glazing was installed on the House of the Future at the ‘Living Tomorrow’ project in Brussels ( www.livingtomorrow.com ) but it is proving difficult to make these so called ‘smart windows’ affordable and it maybe some time before we see them in the UK domestic marketplace.
One of the biggest attractions of glass, it’s transparency, is also it’s biggest failing when it comes to installations in domestic properties. Whilst it’s very appealing to look out of your home it’s much less appealing for others to be looking in.
A very neat solution to this is switchable privacy glass, which is becoming popular in the retail market place (obscuring shop fronts etc). Often associated with internal applications (Offices, Fitting Rooms, Bathrooms) switchable privacy glass is available for use externally. A PDLC film is sandwiched in the glass and using a tiny electrical current the glass can be switched from clear to opaque and vice versa. The electrical supply causes the liquid crystal molecules to align making the glass transparent.
Fed up with cleaning your windows or paying someone to clean them? Pilkington were the first to introduce a self-cleaning glass with the Pilkinton Activ range, a glass with a dual action coating designed to use the sun’s rays to break down and loosen the dirt and the rain to wash it away.
Various other companies now do similar products so it’s worth shopping around. The glass is around 15-20% more expensive but it’s well worth considering if you are installing new glazing if only to avoid the need for dangerous feats from ladders!
With windows being the biggest source of heat loss in your house surely the logical thing would be to use the windows to provide the heat? Yes, you can really buy glass which acts as a giant heater (www.iqglass.com www.finglassuk.com). The glass is coated with a transparent metal oxide which is semi-conductive. An electrical current is fed in and the glass acts like a conventional electrical resistor creating radiant heat.
The advantages of this are clear, no obtrusive radiators, no condensation, no wasted heat, minimal maintenance etc. The catch is that to effectively heat a space you will need ¼ of the area of a room to be in glass. However, it can be connected into other heating systems and you can even have heated mirrors or ‘glass radiators’ in rooms where the amount of glazing is insufficient.
So what price do you pay for this level of innovation? The glass is approximately £700 per square metre, so far from cheap. However, the running costs are substantially lower than a standard gas or electrical heating system.
With solar power coming out as the driving force of the renewable technologies the race is on to incorporate photovoltaic cells into as many building elements as possible. Much research has been carried out into generating electricity from the sun’s rays on glass. The main stumbling block for this has been the level of transparency able to be achieved. After all the main attraction of glass is a clear uninterrupted view.
The latest development is an ultra-thin coating of spray-on liquid consisting of ultra-small solar cells, which despite their size, have been proven to successfully generate electricity. This in combination with heated glass could result in some really exciting products reaching the domestic marketplace, which will delight architects and eco-warriors alike.
Glass may no longer be an indulgent inclusion in your home with its meager thermal performance needing to be balanced by more substantial counterparts. Imagine looking at the world through walls which not only let light in and allow views out, but which react to their surroundings and are truly integrated into the way the building functions and the way the occupants live.
Glass is one of the rare materials which sits comfortably against all other materials; traditional and contemporary. It is unique in its ability to blur boundaries, capture light and soak up the sun. It is these qualities that enable it to truly enhance the spaces we inhabit.
· Follow the solid surfaces from inside to outside to help blur the boundaries whether it be a seamless sandstone floor, a run of Kitchen units or an exposed brickwork wall.
· Consider where you want light to fall within a space and the effect that will have. For example a simple rooflight centered over a dining area or rooflighting over Kitchen worktops.
· Explore internal layouts carefully as everything is ‘on show’ if you choose to construct a glass box. Solid walls can hide a multitude of sins (storage, electrics, radiators etc)
· Glass is expensive but is long-lasting and can completely alter and transform a space
· A little goes a long way as glass helps to create the illusion of space.
· Consider using a specialist glass engineer to really push the boundaries of what is achievable (eg. www.fluidstructures.com)
· Using glass is a clever way to appease Planning Authorities particularly in conservation areas or with listed or historic buildings due to its translucent and reflective qualities.