Energy-Efficient Windows: A Complete Buyer’s Guide

What Are Energy-Efficient Windows?

Why Energy-Efficient Windows Matter

1. Save money. Energy-efficient windows lower your energy bills by reducing the need for constant heating and cooling.
2. Improve comfort. They keep your home’s temperature steady by blocking drafts and cutting heat loss in the winter or heat gain in the summer.
3. Let in natural light. These windows let in lots of natural light and block harmful UV rays.
4. Cut condensation. They help reduce condensation, preventing mold growth and damage to your window frames.
5. Protect valuable items in your home. Low-E coatings protect your furniture, artwork, and flooring from UV rays that cause fading.
6. Block inside/outside noise. Multi-pane windows block outside noise and make your home quieter.

How Do I Know If a Window is Energy Efficient?

Key Features of Energy-Efficient Windows

• Low-E coatings. These special coatings reflect heat to keep your home warm in winter and cool in summer and still let in natural light.
• Insulated frames. Energy-efficient windows have frames filled with materials that keep the temperature inside your home steady. They do so by reducing heat transfer.
• Multiple panes of glass. Double- or triple-pane windows have air- or gas-filled spaces between them to act as extra insulation.
• Gas fills. Some windows are filled with gases like argon or krypton between the panes, which further cuts heat transfer.
• Better seals. Energy-efficient windows have strong seals to prevent drafts, moisture, and air leaks.
• UV protection. This blocks harmful UV rays from penetrating your home.
• Noise reduction. Look for energy-efficient windows that also block outside noise and keep your home more peaceful.

What are Window R-Values?

Why Is It Important?

Factors That Affect Window R-Values

1. The kind of glass used in a window can make a big difference in its R-value. Some options include:
   • Double-pane glass traps air between two panes of glass for moderate insulation.
   • Triple-pane glass adds an extra layer of insulation with three panes and two air-filled spaces for even better insulation.
   • Low-E coatings, or thin metallic layers on the glass, reflect heat and let light in.
2. The space between window panes can be filled with gases (gas fills) like argon or krypton. These gases reduce heat transfer and improve the R-value:
   • Argon is a more affordable option, great for double- and triple-pane windows.
   • Krypton is more expensive, but it provides better insulation, especially for narrow spaces between panes.
3. The material of the window frame also affects its R-value. Common frame types include:
   • Vinyl: cost-effective and energy efficient.
   • Wood: good insulation, but needs more maintenance.
   • Aluminum: strong and durable, but needs a thermal break to improve insulation.
   • Fiberglass: offers both durability and great energy efficiency.
4. Spacer technology and heat transfer are used to separate the glass panes in multi-pane windows. Newer spacers made from foam or rubber cut heat transfer at the edges of the window, which boosts the R-value.

Window Types and Parts

Window Types

• Single-hung windows. These windows have one movable pane, usually the bottom one, which slides up and down. They’re affordable but not the most energy-efficient since the top pane stays fixed and can let in drafts.
• Double-hung windows. Double-hung windows are like single-hung windows, but both the top and bottom panes slide up and down. You get better airflow and insulation; that’s why they are more energy-efficient.
• Sliding windows. These windows slide open horizontally (side to side). They’re easy to open and close and provide good ventilation. When paired with the right glass, sliding windows are energy-efficient, too.
• Casement windows. Casement windows are hinged on the side and open out like a door. They’re great for energy efficiency because when they close, they form a tight seal, keeping drafts out.
• Awning windows. These windows are hinged at the top and open outward. They’re useful in rainy weather because the window stays open while the rain is blocked. They’re also energy-efficient if you use the right type of glass.
• Fixed windows. Fixed windows don’t open at all, but they’re great for letting in light and adding to the look of a room. Since they don’t have any moving parts, they can be sealed tightly for better insulation.
• Skylights. Skylights are installed in the roof and let in a lot of natural light. To make sure they don’t let heat out, you’ll want to choose an energy-efficient option that’s well insulated.

Window Glazing

• Single-panel windows. These windows have just one layer of glass. While they’re cheap, they’re not very energy efficient because they let a lot of heat escape in the winter and let cold air in during the summer.
• Double-pane windows. Double-pane windows have two layers of glass with a gap in between that acts as insulation. These are the most common energy-efficient windows.
• Triple-pane windows. Triple-pane windows have three layers of glass and two gaps filled with insulating gases. These are the best options for extreme climates since they provide the most insulation.
• Low-E glass windows. Low-E glass is great for reducing energy costs and protecting furniture from fading due to UV rays.

Window Frames

1. Metal frames, like aluminum, are strong and durable but not the best at keeping heat in. They’re usually more expensive, but some have special coatings to improve insulation.
2. Since wood is a natural insulator, wooden frames are great for energy efficiency. However, they need regular maintenance to keep them from rotting or getting damaged by water.
3. Vinyl frames are affordable, low-maintenance, and provide good insulation. They’re a popular choice for homeowners looking for energy-efficient windows on a budget.
4. Composite frames are made from a mix of materials, combining the benefits of wood and plastic. They offer good insulation, are low-maintenance, and are durable.

Gas Fills

Spacers

Window Replacement Options

1. Repair existing windows. If your windows are still in good shape, fixing any gaps and adding storm windows will make them more energy efficient.
2. Retrofit windows. This means installing new glass panes into your existing window frames to improve performance without replacing the whole window.
3. Insert windows. Here, new windows are installed into the old frames. The structure doesn’t change, but you get updated windows that work better.
4. Full replacement windows. This is the most complete option, where both the window and the frame are replaced. It’s the best choice for maximum energy efficiency.

• Look for ENERGY STAR certification.
• Check the U-factor. A lower U-factor means better insulation. The lower the U-factor, the better the window is at keeping heat in during winter and out during summer.
• Consider solar heat gain coefficient (SHGC). For hot climates, look for windows with a lower SHGC to block out heat from the sun. In colder climates, a higher SHGC is better to let in some warmth from the sun.
• If you live in a place with extreme temperatures, you might need special windows like triple-pane.
• Balance the cost of new windows with how much energy savings you can expect. Cheaper options might save less on energy bills over time.
• If you live in a noisy area, triple-pane windows will better reduce sound from outside.

Installation Tips from the Experts at Boelter Is Better

• Make sure there are no gaps around the frame. Air leaks let in drafts and waste energy. Use quality weatherstripping or caulk to seal any openings.
• Insulating foam around the window frame will keep your home warm in winter and cool in summer.
• A slightly off-center window can cause gaps over time. Use a level and secure it well to avoid warping.
• Before adding trim or sealing everything up, open and close the window to make sure it operates as it should.

FAQs

Final Thoughts