Just like doors, windows are a functional and aesthetic feature of a home. Through windows, you can regulate ventilation and natural lighting, view the scenery outside, and shield yourself from the elements and intruders. They also ensure your privacy and help protect the contents of both residential and commercial properties.
Energy-efficient windows not only perform the above functions but also help minimise your cooling and heating requirements by regulating indoor temperature. This means energy-saving windows can also reduce your carbon footprint significantly. So, if you’re keen on leading a sustainable lifestyle, energy-efficient windows for houses can make a world of difference.
If you’re looking to make your home energy efficient or need help shopping around for energy-efficient home windows, then this guide can help. Read on to know more about energy-efficient windows and the benefits they offer.
What are Energy Efficient Windows?
The first question that’s probably on your mind is: What are energy-efficient windows?
Also known as energy-saving windows, energy-efficient windows are designed to prevent heated or cooled air from seeping out of the interior living spaces of your home. This means that during winter, they help to keep your home consistently warm, whilst, during summer, they work to maintain the indoor air comfortably cool. The superior insulation they offer thereby reduces your home energy usage — and, of course, your bills!
Not just any type of window may be considered energy efficient. Energy efficient windows possess the following features:
- High level of resistance to airflow: Air carries heat or cold with it; therefore, the more resistant a window is to airflow, the more durable and energy efficient it is.
- Low solar heat gain coefficient: Energy-efficient windows can block harmful sun rays effectively.
Meaning and Definition of Energy-Efficient Windows
If we are to define energy efficiency or state the meaning of the term ‘energy efficient’, it refers to the practice of using less energy whilst providing a similar output quantity from a specific service, device or product. These services include lighting, cooling or heating.
Therefore, energy-efficient windows can cool or warm your home without adding to the consumption of energy. If anything, they actually reduce your energy requirements and help keep your carbon footprint low. Other examples of energy-efficient products include light-emitting diodes or LED lights and kitchen appliances, heating equipment and air conditioners with the Energy Rating Label.
How Much Energy is Lost Through Windows?
Now, you might be wondering how much energy is lost through conventional windows.
Around 30% (or more) of the heating energy inside a home is lost through its windows. During the cold seasons, about 76% of the sunlight that penetrates standard double-pane windows is converted into heat. To prevent energy loss and reduce your power bills, you can use window coverings or treatments, such as windows, blinds and drapes.
Beyond using window coverings, installing storm windows with low-E coatings and/or multi-layer glazing can improve window thermal performance significantly and reduce solar heat gain.
Significance of the U-Value of Glass
When it comes to assessing and measuring glass performance, the U-value of glass or its U-factor is considered the most important. The U-value measures glass insulating characteristics; that is, how much heat flow or heat loss takes place through the glass due to temperature differences between the indoor and outdoor air.
The U-value of window glass indicates how well an insulated glass unit (IGU) can retain heated or cooled air. U-values typically range from 0.1 — indicating very little heat loss — to 1.0 or high heat loss. The lower the glass U-value, the better its insulating performance.
What are the Most Energy Efficient Windows?
Which windows are the most energy efficient? The most energy-efficient windows available today are those that combine a variety of energy-efficient features. This includes the window material, glass, spacers, and double glazing, as these can all affect how energy efficient a window could be. Of course, windows that successfully combine all these elements would be deemed the most energy efficient.
- Low-E glass: Low-E glass reflects heat and UV rays from the sun, thereby keeping your home cooler. It also prevents indoor furnishings from premature fading and protects them from sun damage.
- Double-glazed or triple-glazed: Having two or three panes of glass with insulating gas in the gaps between each layer will not only decrease the amount of heat transfer into and out of your home and condensation but will also aid in noise reduction.
- Aluminium framed: Since aluminium window frames (and other metal frame types) tend to conduct heat quickly, they feature a thermal break or an insulating plastic strip placed in between the inner and outer sections of the frame and sash for energy efficiency.
- Wood framed: Wood, in general, insulates very well. However, it does require regular maintenance and could be quite expensive.
- Fibreglass framed: Considered better than wood-framed windows, fibreglass framed ones feature air cavities that can be filled with insulation.
- Vinyl framed: Composed of polyvinyl chloride (PVC), vinyl window frames have ultraviolet light stabilisers that protect them from sun exposure breakdown and hollow cavities that can be filled with insulation. Although this window frame material is the most inexpensive, the frame has very little resale value compared to other types of frames.
Aside from considering the type of energy-efficient windows you purchase, remember that the quality of the installation can also affect their energy efficiency. Poorly installed energy-efficient windows with gaps and cracks around them won’t function as they should.
Cost of Energy-Saving Windows
When it comes to the cost of energy-efficient windows, their prices vary greatly not only based on the window material, frame, glass, spacers, and glazing but also on the brand.
For example, the average cost of double-glazed windows in Australia that have been newly fitted is about $800 to $1,350 per square metre. The price will increase depending on other factors, such as what energy-saving features you want to be applied to your casement, fixed, or sliding windows.
You also need to factor in installation labour costs, which may be computed per hour or per window.
Best Window Coverings and Treatments for Energy Efficiency
Aside from the windows themselves, you can improve the thermal performance of your home by considering the best window coverings for energy efficiency, including the following:
- Insulated cellular shades: These have the highest R-value (rating for how a material resists the conductive flow of heat) of all types of window coverings. These are usually positioned at the top of each window (or sometimes at the bottom) and comprise pleated materials that fold up or are accordion-like. They can decrease heat loss by around 40% or more and can be automated, too.
- Window quilts: These are quilted sheets that can be rolled and unrolled and whose R-value is comparable to that of cellular shades. They are also cheaper but more difficult to operate.
- Window blinds: Whether it’s vertical (Venetian) or horizontal slat-type louvred blinds, window blinds, in general, can reduce summer heat gain and glare effectively. However, they don’t offer much in terms of reducing heat loss during colder months.
- Curtains and drapes: The ability of curtains and drapes to reduce heat loss or gain depends on the type of fabric and colour. But since they come in a range of materials and hues and can be customised, their energy performance is also variable and can be made efficient.
- Window films: There are specific types of window films designed to reduce unwanted heat gain and protect occupants against glare and ultraviolet exposure. There are also low-E films that are inherently energy-saving.
What is the Window Energy Rating Scheme (WERS)?
The Window Energy Rating Scheme (WERS) allows for the rating and labelling of windows for their annual energy impact on a household anywhere in Australia.
Window makers who want to participate in the WERS scheme need to get energy ratings for their products. Rating organisations accredited by the Australian Fenestration Rating Council (AFRC) are authorised to give these ratings.
This simple and accurate energy rating system can help home and building owners choose products that satisfy their energy efficiency requirements. For example, if you work with a WERS For Film accredited installer to apply a rated film in your household, you may be eligible to receive an energy certificate that’ll impact the energy rating of your home.
Government Grants for Energy-Efficient Windows
The Victorian Energy Upgrades program is designed to help residents and businesses reduce their power bills and carbon footprint by giving them access to discounted energy-efficient products and services — including double-glazed windows. Accredited product and service providers can receive Victorian Energy Efficiency Certificates (VEECs).
In Western Australia, the Household Energy Efficiency Scheme that’s planned to include household energy assessments, tailored education, LED light bulb replacements and other low-cost energy-efficient items have yet to be finalised.
And although there are currently no grants for energy-efficient windows and similar products available in Perth yet, the continued push to reduce greenhouse gas emissions across Australia is likely to take effect in the near future.
Other Factors to Consider for Window Energy Savings
Although the thermal efficiency and performance of windows are crucial to the overall energy efficiency rating of your home, other factors to consider include the position and design of the window and building.
Also, the type of glazing and glass material (e.g. thermally efficient glass), frame, design, window treatments or coverings you use can all impact the total performance of your windows.
Another important factor to remember is the quality of installation, as not even the most expensive energy-efficient windows will work when they are improperly installed. Therefore, it pays to work only with trusted window manufacturers and installers.
If you’re in the market for energy-efficient windows or would like to know your options, please get in touch with Perth Window and Door Replacement Company.