The Many Benefits of Energy Efficient Windows

Windows are an essential element in the building design of every home. They add aesthetic value and provide several important functions such as ventilation, egress, natural lighting, and outdoor views.

The majority of homeowners typically undergo at least one significant home renovation, presenting an excellent opportunity to replace outdated windows with energy-efficient alternatives. The benefits of switching to energy efficient windows include lower energy bills, improved home comfort, and an increase in property value.

Components of Energy Efficient Windows

Gas Fills 

Heat is a type of energy, and therefore it tends to move. Thermal conduction is the process by which heat transfers through a substance. To reduce heat loss or excessive heat gain, the space between double or triple paned glass is filled with krypton or argon gas. Both gases are denser than air, which makes them less thermally conductive, so heat transference between glass panes is reduced.

Heat loss also occurs when warm air rises and cold air sinks, a process called convection. When an insulated glass unit (IGU) is filled solely with air, heat circulates freely between the outer and inner window panes. By using gas instead of air in the IGU, the movement of heat molecules is inhibited, and heat loss is reduced.

Krypton and argon are colorless gases, so they can maintain a window’s visible transmittance while improving thermal efficiency. More abundant and therefore more cost-effective, argon is the most popular gas fill for energy efficient windows.   

Low-E Coatings

To further optimize the thermal performance of a window, energy efficient glass panes are covered with a low-emissivity (Low-E) coating. Low-E coating is a microscopically thin layer of metal or metal oxide that resists infrared and UV light.

With this coating, the heat energy that would otherwise be released through the glass is redirected away from the window. In addition to improving thermal performance, Low-E coatings can help block UV light that may cause furniture and rugs to fade.  

Airtight Design 

Old and inefficient windows are prone to air infiltration, meaning they allow excessive air to pass through the gaps where the sash meets the frame or around the perimeter of a closed window. When windows create these drafts, heating and cooling systems have to work harder to keep a room comfortable. Fortunately, innovations in window design have made modern windows more airtight than ever before.

For example, in Harvey window:

• The frames and sashes are fusion-welded to seal off potential air gaps.
  
• A silicon compound is applied to the sash (a process known as wet glazing) to create a permanent bond between the glass and sash that prevents air leakage.
  
• Serving as both an additional sealant as well providing structural support, a warm-edge spacer bar is positioned between the glass panes. The spacer insulates the glass edges, reducing heat transference through the window panes.

Energy Savings and Environmental Benefits

To help homeowners make energy efficient investments that align with the climate conditions in their regions, the US Department of Environmental Protection created the ENERGY STAR program in 1992. The ENERGY STAR logo is a government-approved symbol that indicates a product meets specific energy efficiency criteria.

To assess thermal performance in windows, ENERGY STAR criteria use values determined by the National Fenestration Rating Council (NFRC). The NFRC is an independent organization that provides ratings for windows based on standardized testing procedures. These ratings include U-factor, SHGC, visible transmittance, and air infiltration. While ENERGY STAR is the federally approved standard for energy efficiency, the NFRC ratings themselves provide a more thorough analysis of a window’s performance.

Energy Bills 

Replacement windows that meet the ENERGY STAR® rating for your climate zone may save you over $100 on energy bills in the first year, depending on number of units, utility, and consumption. According to the Department of Energy, ENERGY STAR-rated windows cut annual energy expenditures in half per square foot compared to less efficient windows. Depending on energy consumption, that reduction may range from $101 to $583 a year.

ENERGY STAR offers a savings calculator for those interested in upgrading their homes for energy efficiency.

Environmental Benefit

Energy efficient windows reduce energy consumption, which is one step in the many-sided move towards environmental sustainability. An individual’s carbon footprint is primarily composed of the greenhouse gas emissions generated by their activities. Residential energy usage (electricity, heating, and cooling) can make up to about 25% of a person’s individual carbon footprint. Energy efficient improvements in the home can help lower that portion of the carbon footprint.

Windows have an important role in making a home more energy efficient. According to the U.S. Department of Energy, windows make up 10% of a home’s surface area, but can account for 25% to 30% of heat loss, and that number can increase up to 45% during winter months.

Luckily, modern energy efficient windows reduce this percentage significantly.

With improved air infiltration rates, less treated air escapes from the home, which lessens the demand on heating and cooling systems. Low-E glass coating and gas filled  keeps homes cooler in the summer and warmer in the winter by controlling the amount of heat transfer. By helping to keep indoor temperatures consistent, energy efficient windows lead to lower household energy consumption and a smaller carbon footprint. 

Choosing Energy Efficient Windows

Frame Material

Energy efficient windows are manufactured in wood, aluminum, fiberglass, and vinyl. Wood is a traditional and sometimes costly option for windows, and it can provide sufficient energy efficiency. Applying an exterior cladding, such as aluminum, to wood windows shields the porous wood from decay. 

Aluminum windows may seem like a cost-effective choice, but they fall short on insulation and energy efficiency when compared to other materials. Aluminum is a thermally conductive substance which makes it very susceptible to heat transfer. It is not as sound-resistant in contrast to other materials, and it may rust over time.

Fiberglass is a lightweight material made from resins and woven glass fibers. It provides good energy performance, though it is often priced higher than wood, vinyl and aluminum due to the cost of its raw materials. Fiberglass is carried by fewer brands than wood or aluminum, and homeowners often experience longer lead times for fiberglass orders in comparison. 

Vinyl windows are made from polyvinyl chloride (PVC), a material which uses less petroleum to create than other plastics. Its low thermal conductivity makes it a high-performing insulator, especially when used in windows engineered with multiple air chambers in their frame and sashes.

Vinyl windows are less heat conductive than aluminum, which allows them to be more energy efficient and cost-effective. Wood can rot, aluminum is prone to corrosion, and fiberglass may need occasional painting, but vinyl is resistant to warping, cracking, and peeling, making it one of the most popular choices for replacement windows.

Form and Function

As a homeowner, would you want a dramatic wall of picture windows in a particular geometric configuration, or do you prefer windows that can open for airflow?

Well-constructed operating windows offer exceptional air infiltration rates, along with the advantages of ventilation and egress. Casement and awning windows open outward with a hinge along their sash, and the movement of closing them presses that sash closer to the frame for a stronger seal. Casements and awnings open at an angle that drives breezes more efficiently into the home.

New double hung windows have improved air infiltration rates due to better sash locking technology that helps eliminate gaps.

The operation style and configuration of windows you want to install should factor into your final decision, along with their energy efficiency features.

Budget 

Low-E coatings, gas fills, and the number of panes in the specified glass package will affect the cost of each window. Triple pane windows, with an additional pane of glass and another gas fill space, are higher performing than double pane windows, and  their price will reflect that. As mentioned above, window materials vary in price and affect the overall cost of energy efficient replacements. 

Installation by a professional contractor will carry its own fees, however proper installation can save homeowners time, prevent headaches from additional work, and protect them from voided warranties due to improper installation.

Homeowners should keep in mind that replacement windows are a long-term investment; energy savings would accrue from the first day that energy efficient windows are installed, and new windows are marketable assets if the house is being put up for sale. 

Ready for New Energy Efficient Windows?

At this point, you may be on the fence about investing in replacement windows. Here is a list of questions to consider: 

• Do you want to save money on energy consumption costs? 
• Do you want to improve the comfort of your home by reducing drafts?
• Would you like to increase the value of your home?

If you answered ‘yes’ to these questions, then assess your current windows:

• Are they more  than 20-30 years old?
• Are they only single pane? 
• Are the frames rusted or rotten? What material are they? 

Old, single pane windows are a prime opportunity to invest in energy efficient replacements. Wood or aluminum windows may need to be upgraded to a more durable choice like vinyl. Drafty or defective windows should be replaced as soon as possible. We recommend consulting a trusted contractor who can order and install replacement windows for you. 

Energy-efficient windows provide exceptional insulation, reducing drafts and maintaining stable temperatures year-round. With gas fills and low-E coated glass, they control heat gain and loss while reflecting UV rays. These windows offer long-term savings, yielding up to a 70% return on investment when the property is sold.

Upgrade to energy-efficient windows for enhanced comfort, reduced energy consumption, and a more sustainable future.

FAQs

• 1. What are the benefits of energy-efficient windows?
  • Energy-efficient windows can help offset energy consumption, improve home comfort and increase property value.
• 2. What are gas fills in energy-efficient windows?
  • Gas fills, such as krypton or argon, are denser than air and are used to fill the space between double or triple panes of glass in energy-efficient windows. They reduce heat transference and improve insulation performance.
• 3. What are Low-E coatings in energy-efficient windows?
  • Low-E coatings are thin layers of metal or metal oxide applied to the glass panes of energy-efficient windows. They reflect heat energy and block UV light, improving thermal performance and protecting furniture from fading.
• 4. How do airtight designs contribute to energy efficiency in windows?
  • Airtight designs in modern windows, such as fusion-welded frames, wet glazed sashes, and warm-edge spacers, reduce air leakage and heat transfer, making windows more energy-efficient.
• 5. How do energy-efficient windows save on energy bills?
  • Windows with energy efficiency features, including those that meet ENERGY STAR criteria, can help to reduce a household’s energy consumption. The amount of money that will be saved depends on the home’s number of units, their energy provider’s utility rates, and the amount of consumption itself. ENERGY STAR estimates that homeowners on average save anywhere between $100-$500 after replacing single-pane windows with double-pane energy efficient ones.
• 6. What environmental benefits do energy-efficient windows offer?
  • Energy-efficient windows reduce energy consumption, lowering an individual's carbon footprint and contributing to environmental sustainability by using less electricity for heating and cooling.
• 7. How do energy-efficient windows impact a home's carbon footprint?
  • Energy efficient windows are engineered to help regulate heat loss and gain, which keeps rooms comfortable. By decreasing the demand for heating and cooling, less energy is consumed, resulting in a smaller carbon footprint for the household.
• 8. What factors should be considered when choosing energy-efficient windows?
  • Factors to consider include frame material options (wood, aluminum, fiberglass, vinyl), form and function (design aesthetics and window operation), and budget (low-e coatings, gas fills, number of panes).
• 9. How do different frame materials affect energy efficiency?
  • Wood, aluminum, fiberglass, and vinyl are common frame materials. Vinyl windows are often the most energy-efficient and cost-effective, while wood windows may require exterior cladding for improved energy efficiency.
• 10. How do different styles of windows impact energy efficiency?
  • Well-constructed operating windows like casement and awning windows offer good air infiltration rates, a leading factor in energy efficiency. Double hung windows with improved sash locking technology also reduce air leakage.
• 11. Are energy-efficient windows a long-term investment?
  • Yes, energy-efficient windows provide long-term savings from the date of installation, and they can also increase the market value of a home when selling.
• 12. How do I know if I need new energy-efficient windows?
  • Consider factors such as the age of your windows (older than 20-30 years), single-pane windows, rusty or rotten frames, and drafts. If your windows have these issues, it may be a good time to invest in energy-efficient replacements. If you want a different operating style or new configuration, you may have a good opportunity to invest in energy efficient windows.