In this post you will learn:
- The performance criteria for an energy efficient window
- The anatomy of an energy efficient window (Framing/Glass/Spacing)
- Which types of windows are the best for energy efficiency
With the rising costs of living, it is important for homeowners to consider their long-term saving strategies when it comes to their windows.
While home renovations have often meant selecting new blinds, paints or window treatments – people often forget how much their windows can actually impact their electricity consumption, property value and overall utility bills!
One great way to reduce energy waste (along with their corresponding costs) is to replace outdated single-pane windows for one of the many energy-efficient alternatives on the market today.
At Stouffville Glass, we like to keep our clients well-informed. So let’s take a look at everything you need to know about your high efficiency window options:
Performance Criteria For an Energy Efficient Window
Before we can determine the best type of window for your next home-improvement project, it is important to understand how high efficiency window quality is measured.
The National Fenestration Rating Council is a third-party, non-profit organization that is responsible for the independent testing and certification of energy efficient windows, doors and skylights.
High efficiency windows that pass inspection receive an Energy Star label to help consumers identify them on the market!
It is important to note that the NFRC does not distinguish between “good” and “bad” windows, but instead provides rating and certification for windows that pass inspection.
These inspections are broken down into five rating categories:
The rate of heat-loss is represented by the U-Factor (or U-Value) of a window’s assembly.
Lower U-Factors will yield better insulation properties in energy efficient windows, as well as more resistance to heat flow.
Some double-pane, high efficiency windows can possess U-Factors of 0.30 or lower; while triple-pane, high efficiency windows are able to achieve U-Factors of 0.15.
2. Solar Heat Gain Coefficient:
The SHGC measures the solar energy transmitted by the window itself and will show you exactly how well the product can block heat produced by sunlight.
The SHGC measures in values from 0 to 1, with a ‘typical’ range sitting between 0.25 to 0.80.
The less solar heat being transmitted by the window, the lower the SHGC score will be.
3. Visible Transmittance:
Visible Transmittance measures the amount of light that gets pushed through a window.
Much like the SHGC, VT also measures between values of 0 and 1, with the typical range being 0.20 to 0.80.
High efficiency windows will measure up with a higher VT score when they allow more light to travel through.
4. Condensation Resistance:
Scored on a scale between 0 and 100, Condensation Resistance measures how well a window can hold up against water build-up.
this is a common problem for many run-of-the-mill windows that do not measure
on the NFRC’s Energy Star scale.
Energy efficient windows that stand up well against build-up will score a higher CR Factor than those that do not.
5. Air Leakage:
Air Leakage (AL) measures the cubic feet of air that travels through one square foot of window area per minute.
The typical industry standard for building codes asks for an AL of 0.3 cf-m/ft².
In this case, less air leakage will yield a lower AL value and provide higher energy efficient qualities.
Anatomy of an Energy Efficient Window
In recent years, manufacturers have favoured a wider variety of technology and resources in order to construct high-efficiency, energy-saving windows that meet the Energy Star window standard.
That being said, high efficiency windows are created with an intelligent combination of parts including frame/sash materials, spacers and (of course) the glass itself.
Quality Frames and Sash:
Energy-efficient windows can come with a variety of different framing options:
- Aluminum: Provides a durable, recyclable framing option. Designs can
include thermal breaks that can lower heat loss from the metal.
- Wood: Tried-and-true over time, wood is a strong material that
insulates fairly well. On the downside, wood can become very difficult to
protect if it is not covered in either vinyl or aluminum.
- Fiberglass: Can be left hollow or filled with foam to increase
insulation. Fiberglass frames are strong, reliable and low-maintenance.
- Vinyl: Much like fiberglass, vinyl can be hollowed out or filled
with foam insulation and the wider variety can be reinforced with other
materials such as wood and metal.
Vinyl windows have become an increasingly popular (and economical) alternative to the framing materials of the past.
With a wide selection of styles, vinyl can provide an excellent solution to high-efficiency and low-maintenance window framing.
- Low-E Glass: Glass by itself has never been a good insulator, but with the introduction of “low-emissivity” (or “Low-E”) glass, manufacturers have been able to create a coating that reflects ultraviolet and infrared light.
Low-E glass is treated with a combination of invisible tinting and reflective coating in order to reflect the sun. As an added bonus, Low-E glass can help protect your furniture from fading too quickly!
- Multi-Pane Glass and Gas Fills: Houses that were built over two
decades ago were typically built with single-pane windows that did not do much
for energy conservation.
Through the introduction of double-pane glass, window manufacturers have applied gas-fills by inserting odorless, non-toxic gases (such as argon or krypton) between the panes creating a barrier that reduces energy transfer from one side to the other.
Many energy saving windows will include two panes or more, as well as a gas fill for optimized efficiency.
Window Spacers maintain the correct distances between panes and are a vital part of any high efficiency window.
An often-overlooked element of energy saving window construction, the spacers are the brackets that grip the panes against both the window sash and frame.
Window spacers perform like energy conductors causing the use of inexpensive parts (such as aluminum) to decrease their thermal efficiency.
Alternatively, non-metallic spacers can serve to better reduce heat transfer and insulate the edges of the panes.
Which Types of Windows Are Most Energy Efficient?
The type of high efficiency window you select will ultimately come down to your individual preferences.
However, here are three major styles worth considering:
Casement & Awning:
A popular choice for its elegant style and design, casement windows are a fantastic addition to your home.
With powerful protection against high winds, these windows are also able to provide customized ventilation options. Opening as little as 2-3 inches, you can easily control how much air circulates throughout the room.
Easy to clean and difficult to damage, these windows do require some routine maintenance on the hinges and seals but are otherwise a prime choice for stability and efficiency!
The only downside is that they open outwards, making them less ideal for high traffic neighbourhoods.
Tilt & Turn:
A popular window style in Europe, Tilt & Turn windows offer an elegant combination of clean lines and minimal hardware.
Its single handle uses three functional positions including 1. downward to lock, 2. horizontal to swing the sash in, or 3. upwards to tilt the top of the window inwards for exceptional air ventilation.
With its clean and robust aesthetic, the (sometimes) tricky maneuvering is definitely worth getting used to.
Double/Single Hung & Slider:
The most versatile and economical of the three – hung sliders have been a popular choice since pre-war home construction.
Since then, the focus on energy conservation has inspired modern updates that include new configurations, glazing options and improved thermal technology.
Available in two variations (single hung and double hung), the movable panels simply slide up to allow for airflow throughout your home.
On a final note, energy efficient windows can only perform up to par if they are installed correctly.
While flashing and caulking may seem like the easiest parts of the process, improper installation can run the risk of air leaks, water damage, sky-rocketed utility expenses and more.
At Stouffvllle Glass, we pride ourselves on providing thorough and complete services that can be enjoyed for years to come.
If you are interested in renovating your home with high efficiency windows, we’re here to help!
Click here or call our experts
at (905) 640-4016 for a complimentary consultation.