Ask any homeowner about what they really ‘love’ in their homes and one of the answers is invariably their views. Connectivity to the outdoors, natural light and a feeling of space, all play a key part in what makes us happy – so much so that architects and designers have been steadily increasing the number and size of windows in many modern homes.
From a practical point of view, however, all this glass comes at a cost. Nearly 40% of all the energy required in a home is used for cooling and heating and the major culprit for heat loss in winter (40%) and heat gain is summer (90%) comes from the very things that give us our lovely views – windows.
To counter the costs associated with solar gain and heat loss, design principles and material innovations have combined to make windows much more energy efficient. Here’s how:
Passive Solar Design
The overall design and orientation of your home is the first thing you should consider when it comes to energy efficiency. Orientating your house to take best advantage of your climate zone, mapping the course of the sun and wind to plan the position and size of windows, appropriate shading and thermal capture, all contribute to how comfortable you will feel and how much money you could save in heating and cooling bills.
Likewise, the glass you use in your home is also critical – bringing with it a range of technical considerations and decisions.
Single Glazed, Double Glazed and Thermal Break Windows
The first thing that many people think about when it comes to windows and glass is whether they want single or double glazing. Put simply, a single glazed window is constructed using a single pane of glass and is the only barrier between you and the outside world. Given that most glass is only millimetres thick, this can often cause headaches when it comes to insulation. Double glazed windows, on the other hand, use two separate pieces of glass that have a vacuumed layer in between to act as a barrier. This can reduce heat loss and gain by more than 50%.
Thermal break systems are another way to reduce heat and cold transfer via conduction. Essentially, it uses a resin or plastic to coat metal frames to separate the interior part of the window from the exterior part. This will greatly reduce heat or cold transfer between the inside and outside – thereby reducing temperature fluctuations within your home.
Even though the initial cost of double glazed windows or thermally broken double glazed windows is higher than single glazed alternatives, they will pay for themselves over time. One of the best ways to ascertain the potential value of any system, and the cost savings you are likely to make, is to calculate the U-value and solar heat gain coefficient (SHGC) measurements.
What Is A U-Value?
Builders and architects employ the U-value to measure the rate of heat loss through a material – the lower the score the better. While the calculation can be quite complex, when it comes to windows it can accurately gauge how much energy in watts the window will conduct based on temperature differentials within the house and outside of the house.
Solar Heat Gain Coefficient (SHGC)
When it comes to heat from the sun, the SHGC measures how much direct sunlight can flow through a window system, and how much energy can be absorbed within the window system for subsequent release. Once again, the lower the number the better, with the total number range being between 0 and 1.
Angle of Incidence
Importantly, solar gain varies according to the sun’s angle of incidence – with sunlight hitting a window square-on transferring much more heat than sunlight that hits at pronounced angle. As the sun changes location throughout the day and even throughout the seasons, the solar gain for any window will differ. However, all glazing manufacturers will measure and report on their products SHGC number based on an angle of zero. Depending on your climate and the position of your windows you may therefore select different SHGC results for different areas – sometimes wanting more heat transfer and sometimes wanting less.
So rather than use materials that produce the same U-value and SHGC across all of your windows, you can now mix or match, to produce even better energy efficiency.
Low Emissivity Glass
To further improve your U-value and SHGC numbers, new glass products have come onto the market, one of which is low emissivity glass (low-e glass). This glass has either a vacuum-deposited thin film metal coating or a pyrolytic coating which reduces the amount of solar heat gain while still allowing good levels of visible light.
The Window Energy Rating Scheme (WERS) provides a star rating for glazing units, as well as a window systems numerical U-value and SHGC values. In addition, it can measure visible light transmittance and air transfer. Most manufactures will use their WERS rating to promote their systems, listed according to the types of frame and glazing.
Glazing in Your Modscape Modular Home
Modscape’s perspective on sustainability is centred around a desire to create eco-friendly modular homes that are innovative, comfortable, healthy and environmentally sustainable. Your home will be optimised for passive design performance – harnessing the power of the sun and wind, specific to your individual building site.
High-quality, precision-manufactured, aluminium window frames with double glazing is standard in all Modscape’s modular homes with the option to upgrade to thermal break frames and low-e glass. Available in a wide variety of architectural profiles we’re able to create amazing and highly individual spaces.
We’ve utilised these windows to great effect in our Brooklyn display suite. Come see for yourself Monday – Friday 10am-4pm or Saturday by appointment. If you have any other questions, feel free to contact our team on 03 9316 6000.