– Written by Nichelle Lemmer
Transparency, sustainability and being energy-efficient are not just buzz words in the business sector anymore. With the new SANS 10400 Part XA regulations now applicable and the pressure from government to lower one’s carbon footprint, these words are becoming principles.
In the glass and aluminium industry, manufacturers and suppliers have to enter the low-energy market by providing products that will specifically cater for these needs. Walls & Roofs took a closer look at the low-energy products and new trends emerging on the market.
Facades and energy-efficiency
Bernice Bailey, the marketing manager of PG Glass, says it is now a fairly complex exercise to evaluate glass in design. “One is required to satisfy legislation in the areas of heat loss, heat gain and air infiltration,” she says. According to her, a series of formulae have been compiled to generate these values based primarily on frame material, glass type, overhangs and opening size.
Niels Eichhorn, the managing director of Aluglass, says that in South Africa clients are mostly looking for products that allow the right amount of natural light into working and living spaces while minimising the heating associated with this. He commented that several solutions exist to achieve this, one of which is the application of a low emissivity coating on glass that appears clear, but reflects a good portion of incoming heat-energy back out of the window. Low emissivity coatings were originally developed for colder climates to retain heat in living and working spaces. By changing the location of the coating relative to the heat source, this allows some of the incoming solar radiation to be reflected off the building before it has had a chance to heat the space.
He notes that a low E surface is best accommodated on the inside of a double-glazed element where glass-cleaning activities cannot harm the coating. According to him, productivity improvements from people remaining visually connected with the outside world have been demonstrated.
He suggests that various other products can be used to achieve similarly effective heat control. Internal roller blinds with highly reflective external surfaces reflect between 75% and 77% of the incoming solar radiation.
He says there are other high-performance shading systems on the market that specialise in daylight management systems making the most natural daylight. “The individual louvres of the blinds are profiled so that up to 85% of the incoming heat radiation is reflected back out of the window while allowing a phenomenal level of view through,” Eichhorn explains. The louvres can also be used to direct light onto the underside of ceilings to allow the natural light to penetrate the space more deeply. This reduces the need for artificial light. He says the blinds are aesthetically appealing and can be used to complement various designs.
Bailey says there are about 35 types of low-energy glass available on the South African market, and they need to be evaluated and priced depending on their properties that have been combined with other glass types. “One also needs to consider thicknesses, coatings and double-glazing possibilities,” she says.
The role of tinted windows
Eichhorn says tinting integration of a reflective surface, alters the natural light entering a room to be compromised. “Certain colour elements of the light get filtered out, creating an artificially unpleasant lighting situation.” He is of the opinion that the only way to correct this is by using the right artificial lighting.
He further adds that using artificial light can have a psychological effect on the inhabitants of a room, and could also affect job performance and the well-being of a person. Eichhorn says that specifiers could expect a solution to this problem in the near future, as the development of systems that would allow lighting as close to natural light as possible through is top priority for international manufacturers.
According to Eichhorn, there is glazing available that is not so dark. This allows a room to stay connected to its surroundings. He says that in some cases glass products like this can be used when a client has a need for privacy. The only additional pitfall of using tinted glass is that it absorbs heat and gets hot. “This can be balanced out with other products such as blinds if needed,” he says. “It all depends on the client’s needs and the ambience one wants to create in a room or building.”
According to Bailey, tinted glass types have good glare-control qualities and medium sun-control qualities. She further explains that coated-glass types have good sun and glare control and that double-glazing has excellent temperature and sun control. “There are very few shortcomings with these glass types. Highly reflective glass may not suit a particular project, but this is compensated for with very good heat-reflecting qualities. Decisions are often made on price.”
Glass and solar heat gain
Bailey explains that solar strike is the amount of sun that hits the glass. “Energy is dispersed in three ways: radiation through the glass into the space, conduction through the material itself and the remainder is reflected away from the glass.” She adds that solar heat gain coefficient (SHGC) is heavily affected by the glass type. “Single clear float, for example, has an SHGC coefficient of 0,81 (allows 81% solar radiation through), whilst a tinted double-glazed unit has an SHGC of 0,54.
Eichhorn explains that solar strike can be managed by investing in external shading systems that limit the amount of sun exposure to a window or facade. “This can be done by using a roof overhang. The size of the roof overhang is based on the need to control the shade that falls on the window or facade during various times of the day.”
He further explains that sun-control structures can also be used to stop direct sunlight from reaching a window or facade. Such systems can make it easier to manage light and heat harvesting by controlling the access of sunlight to a building. “In the winter months it should be positioned to harvest the heat and in the summer it should be able to stop the sunlight from reaching the windows or facades.”
Using the various products available on the market to optimally manage energy efficiency is a balancing act. A list of pitfalls and advantages of the products should be weighed up against each other to find the perfect solution for each project. A combination of these products could create the right setting to enhance energy-efficiency and add more benefits, like cost savings, to a client.
Full acknowledgement and thanks are given to Aluglass and PG Glass for the information given to write this article.