Use of solar control window film improves the wellbeing and performance of pupils and teachers reduces energy costs and protects valuable assets but it can also make a school look more ‘cool’, according to specialist supplier and installer, Advanced Glass Technology.
Any teacher will testify that a hot and sticky classroom is not an environment conducive to happy, productive learning, the reverse in fact. Glazing has a dramatic effect not only on the energy performance of a building but also the human performance of its occupants. A research study undertaken in the USA by biomed expert, David Wyon, showed that productivity drops by a massive 40% when the temperature rises from 68 Degrees Fahrenheit (20 degrees Celsius), the temperature at which productivity is at its optimum, by just 7 Degrees to 75 Degrees Fahrenheit (23.9 degrees Celsius).
When solar radiation penetrates glass, it causes heat to build up inside, leading to hotspots, requiring a necessity for the majority of schools to obtain costly mobile air conditioning units or ineffective desk and floor mounted fans. Solar heat gain from unprotected windows is substantial, making them an ideal target for efficiency improvements. A big challenge in school facility management is balancing energy usage with climate control and interior comfort. Some solar control window films reject up to 80% of solar energy, helping to regulate heat absorption and reduce the dependency on high wattage cooling solutions.
Major window improvement projects are generally challenging for schools as they are expensive, time consuming and disruptive but they can also be unnecessary. Instead of replacing windows, retrofitting existing glazing with special window film, is often a far cheaper, quicker and more practical solution, if the windows remain in good condition. It’s also a more environmentally responsible option, avoiding the need to generate large amounts of waste material when frames and glass are removed during replacement.
So what exactly are the advantages? Window film reduces solar heat gain by blocking the sun’s radiation (see graphic). Solar radiation, or solar energy, is made up of three components: ultraviolet radiation, visible light and near-infrared radiation. Near-infrared radiation makes up 53% of the solar spectrum, visible light 44% and ultraviolet 3%. When sunlight hits a window, some of the energy is absorbed and some reflected by the glass but most is transmitted through it. According to the International Window Film Association (IWFA), a pane of clear glass reflects about 6% of solar radiation, absorbs 5% and transmits the remaining amount. When this energy enters a space and is combined with the ambient heat already present, this excess heat can make an uncomfortable difference.
Installing solar control window film increases the amount of solar energy both reflected and absorbed by the window. Most window films have an ultra-thin metallic coating, made up of aluminium, stainless steel, silver or a combination of these, that reflects and absorbs solar radiation. Of the radiation absorbed, most of it is re-radiated outward, though some is radiated into the building.
The most important performance measurement of the heat rejection ability of solar control window film is the solar heat gain coefficient (SHGC), which measures the total amount of solar energy transmitted into a room. This includes both solar energy directly transmitted through the glass and solar energy absorbed and radiated into the building by the film. The heat rejection ability of window film can be as high as 80% according to IWFA.
Of course, the amount of energy reflected and absorbed varies depending on the types and quantities of metals used in the film and it’s important to ensure that the right film is installed for the application to achieve the optimum results, as Martin Westney, Managing Director of Advanced Glass Technology, explains:
“If two window films have an equal SHGC and one rejects more near-infrared radiation than the other, it would also transmit more visible light. This is because more of the solar energy rejected is in the near-infrared range.
The rejection capabilities of window films vary which is why it’s important to ensure the correct application depending on what the objectives are.”
AGT retro-fitted mirror-reflective solar control film to the inside of south-west facing windows of a primary school in East London (see photos), which was suffering from significant solar heat gain, as well as excessive glare in some of the classrooms. The school had invested in new whiteboards, which were proving difficult to see in conditions of bright daylight. There was an option to choose blinds but apart from being more expensive, the knock-on effect is that, when closed, natural light is swapped for artificial light, which consumes energy and generates lots of heat, thus exacerbating the problem further and creating a vicious circle. By installing solar control film in one swift application, AGT solved both issues.
“The mirror-effect solar control film improved conditions instantly,” said Westney. “As well as dramatically reducing internal heat, the film completely eradicated issues with screen glare in the school’s ICT suite and in terms of design, improved the aesthetic appeal of the building itself, prompting a number of students and even parents to say that it looked ‘cool’. That was an added bonus as it’s more than likely this will have a positive impact on the learning environment.”
Although it’s early days, Westney claims that the school will recoup its investment within three years, in terms of better thermal efficiency and reduced energy consumption. In addition to providing energy savings all year round, solar control window film offers a number of other integral benefits. Although natural daylight is a desirable quality in a building, allowing the sun to stream through clear windows can expose students, teachers and fixtures to dangerous UV rays. Prolonged exposure is not only harmful to health, it also causes fading of carpets, equipment, materials and furnishings.
AGT’s range of solar control films block 99% of the sun’s damaging UVA and UVB rays. Because window film can offer UV protection without sacrificing outlook or compromising the benefits of natural light, window film is an ideal solution. Customers can choose a tinted shade to block more incoming light and enhance privacy, or a clear, barely detectable film and still achieve the same UV benefits.
Equally, the safety of pupils and premises is paramount. Window film also provides significant protective qualities, as it’s specifically designed to hold shattered glass together to prevent injury in the event of window breakage during severe weather, accident or even an explosion. Similarly, a window fitted with protective film will form a barrier preventing internal damage caused by vandalism or access through the windows in an attempted burglary.
All window films installed by AGT carry a 10-year guarantee, as Martin Westney concludes:
“Window film acts as a protective layer on glass but unlike our own skin, the film is constantly exposed to sunlight, so the effects of temperature and UV rays on the adhesive are accelerated. This is more acute in particularly hot climates but even in the UK, film should be replaced within ten years and tested regularly from installation.”
With over forty years of experience, Hertfordshire based AGT can offer guidance to schools facilities managers seeking cost effective solutions to energy reduction, as well as health and safety and security improvements.
As a special summer offer, AGT is discounting all solar control film installations by 20% for projects booked before 1 September 2014. Please quote this article.