What Makes a Window Energy-Efficient?
An energy-efficient window minimizes heat transfer between your home’s interior and the outdoors. It does this through a combination of advanced glass coatings, insulating gas fills between panes, and frame materials that don’t conduct heat.
In Virginia and North Carolina, energy efficiency is mostly about keeping heat out. Our summers run from May through September with temperatures regularly hitting 85-90°F and humidity sitting at 70-80%.
That means your AC works overtime, and your windows are either helping or hurting that effort. The right combination of glass, frame, and installation can cut your energy costs by 25-40% compared to older or underperforming windows.
The key performance metrics to understand are:
- U-Factor measures how well a window prevents heat from escaping. Lower is better. Look for 0.30 or below for Virginia.
- Solar Heat Gain Coefficient (SHGC) measures how much solar radiation passes through the glass. Lower is better in hot climates like ours. Look for 0.25 or below.
- Visible Transmittance (VT) measures how much natural light comes through. Higher is better, since you want efficiency without sitting in the dark.
- Air Leakage (AL) measures how much air passes through gaps in the window assembly. Lower is better. Quality windows rate 0.30 or less.
The Top 5 Energy-Efficient Windows for Virginia and North Carolina
1. Double-Hung Windows with SmartSun Low-E4 Glass
Best for: Most rooms in your home
Double-hung windows are the Virginia Coastal Area’s most popular style, and when paired with Renewal by Andersen’s SmartSun Low-E4 glass, they become one of the most efficient options available. SmartSun glass is 70% more energy efficient in summer and 49% more efficient in winter compared to ordinary dual-pane glass. It also blocks over 95% of harmful UV rays, protecting your furniture, floors, and artwork from fading.
The double-hung design gives you ventilation from both the top and bottom sashes. Open both on a mild evening, and warm air exits through the top while cooler air enters from the bottom. During Virginia’s comfortable spring and fall months, that natural circulation can replace your AC on many days.
2. Casement Windows with Low-E4 Glass and Argon Fill
Best for: Waterfront homes, kitchens, and rooms where you want maximum airflow
Casement windows open fully, giving you 100% of the window area for airflow. That alone makes them efficient in a different way: on comfortable days, you can ventilate naturally instead of running the AC at all.
But the real efficiency advantage comes when they’re closed. Wind pressure pushes the sash tighter against a compression seal, which means casement windows have some of the lowest air leakage ratings of any operable window type.
Paired with Low-E4 glass and argon gas fill, casement windows deliver excellent thermal performance. Low-E4 glass blocks 84% of UV rays and helps keep your home warmer in winter and cooler in summer.
The argon gas between panes adds another layer of insulation beyond what air alone provides.
3. Picture Windows with Enhanced Triple-Pane SmartSun Glass
Best for: Waterfront views, living rooms, and any room where you want maximum efficiency with maximum light
Picture windows are fixed, meaning they don’t open. That’s actually an efficiency advantage because there are zero operable parts that can leak air. A well-installed picture window has the lowest air leakage of any window type, period.
For Virginia homes with Chesapeake Bay, Elizabeth River, or oceanfront views, combining a picture window with Enhanced Triple Pane SmartSun glass gives you the absolute best thermal performance available.
You get all the UV blocking and solar heat reduction of SmartSun technology, plus the added insulation of a third pane of glass. The result is near-silent interior comfort with dramatically reduced cooling costs.
4. Awning Windows with Low-E4 SmartSun Glass
Best for: Bathrooms, kitchens, and any room where you want ventilation, even during rain
Awning windows hinge at the top and open outward from the bottom, creating a canopy effect that keeps rain out while letting air in. In Hampton Roads, where afternoon thunderstorms can roll through on summer days, that means you can ventilate moisture-prone rooms without worrying about water damage.
With Low-E4 SmartSun glass, awning windows deliver strong energy performance in a compact package.
They seal tightly when closed (similar to casement windows, wind pressure actually improves the seal), and their smaller size means less total glass area exposed to solar heat gain. That’s especially helpful on south and west-facing walls where summer sun hits hardest.
5. Sliding Patio Doors with SmartSun Low-E4 Glass
Best for: Back patios, decks, and any large opening connecting indoor and outdoor living spaces
Patio doors are the largest glass openings in most homes, which makes their energy performance especially important. A poorly insulated patio door can be a massive source of heat gain in summer and heat loss in winter. Renewal by Andersen sliding patio doors with SmartSun Low-E4 glass address this by applying the same advanced glass technology used in their windows to these larger panels.
The Fibrex composite frame keeps the door operating smoothly year after year without the expansion and contraction that causes air gaps in vinyl or aluminum doors. Tempered safety glass comes standard, and the multi-point locking system creates a tight seal when closed.
How Does Glass Technology Affect Energy Efficiency?
Glass is the single biggest factor in window energy performance. The frame matters, the installation matters, but the glass is where most heat transfer happens.
Renewal by Andersen offers several glass packages, and here’s how they compare:
- Low-E4 Glass is ideal for seasonal climates where both heating and cooling matter. It blocks 84% of UV rays and provides balanced performance year-round. This is a solid choice for any Hampton Roads home.
- SmartSun Low-E4 Glass is their most popular energy-efficient option for hot climates. It’s 70% more efficient in summer than standard dual-pane and blocks 95% of UV rays. For Hampton Roads, where cooling costs outweigh heating costs most years, this is the best overall choice.
- Enhanced Triple Pane Glass adds a third pane for maximum insulation. Available with either Low-E4 or SmartSun coatings. Best for homeowners who want peak performance or need serious noise reduction.
- SmartSun with HeatLock Technology combines hot-climate performance with a room-side coating that reflects heat back indoors during winter. Delivers near triple-pane performance from a dual-pane window.
All of these include argon gas fill between panes for added insulation.
Why Does Frame Material Matter for Energy Performance?
Your frame material affects both the thermal performance and its longevity. A frame that warps, expands, or contracts over time develops gaps that leak air, undoing the benefits of great glass.
Here’s how common frame materials perform for energy efficiency:
- Fibrex composite maintains a tight seal for decades because it doesn’t significantly expand or contract with temperature changes. It also insulates up to 700% better than aluminum. Zero maintenance means it doesn’t degrade in Southeastern Virginia’s humidity and salt air.
- Fiberglass performs similarly to Fibrex in terms of thermal stability. Strong and durable, but fewer style and color options.
- Premium vinyl offers decent insulation when new, but can warp over time in extreme heat, potentially creating air gaps. Lifespan in Virginia is shorter, at 20-30 years.
- Wood insulates well naturally, but absorbs moisture in our humidity, leading to swelling, gaps, and eventually rot. Constant maintenance is required to maintain energy performance.
- Aluminum conducts heat and cold readily, making it the worst performer for energy efficiency. It also corrodes in our salt air.
How Much Can Energy-Efficient Windows Save You in Virginia?
Most Virginia homeowners save $300-$700 per year on energy bills after upgrading to energy-efficient windows. The exact amount depends on what you’re replacing and what you’re replacing it with.
Over 20 years, those savings add up to $6,000-$16,000, depending on your starting point. Factor in the 70-85% resale value return that quality windows provide, and the investment makes strong financial sense.
Southern Virginia’s climate actually makes window upgrades pay back faster than in many other parts of the country. Our long, hot summers mean AC runs heavily for five months or more. Reducing solar heat gain through better glass has a bigger impact here than in cooler regions, where heating is the primary concern.
What ENERGY STAR Ratings Should You Look For?
For Virginia (which falls in the ENERGY STAR South-Central climate zone), look for a U-Factor of 0.30 or lower and an SHGC of 0.25 or lower. These ratings ensure your windows are optimized for our hot, humid conditions.
ENERGY STAR certification means the window meets minimum efficiency standards set by the EPA for your climate zone. But “minimum” is the keyword.
Renewal by Andersen’s SmartSun glass exceeds ENERGY STAR requirements, which is why many of their windows qualify for the ENERGY STAR Most Efficient designation.
When comparing windows, make sure you’re looking at whole-window ratings (which include the frame and installation), not just the center-of-glass rating.
Center-of-glass numbers always look better because they don’t account for heat transfer through the frame and edges.
Do Energy-Efficient Windows Qualify for Tax Credits?
Yes. The Energy Efficient Home Improvement Credit allows homeowners to claim up to $600 for qualifying windows. The credit covers 30% of the cost, capped at $600 per year for windows specifically.
To qualify, your windows must meet ENERGY STAR Most Efficient criteria for your climate zone. Renewal by Andersen windows with SmartSun or Low-E4 glass typically meet this standard. Keep your receipts and the manufacturer’s certification statement for your tax records.
This credit resets annually, so if you’re replacing windows in phases across multiple tax years, you can potentially claim the credit more than once.
Since these laws and regulations change constantly, check current IRS guidelines or consult a tax professional for details specific to your situation.
Frequently Asked Questions
What is the most energy-efficient window you can buy?
For Virginia, a fixed picture window with Enhanced Triple Pane SmartSun glass and a Fibrex composite frame is the most efficient option available. Among operable windows, casement windows with SmartSun Low-E4 glass and argon fill deliver the best combination of efficiency and ventilation.
Are triple-pane windows worth the extra cost?
Triple-pane windows add 15-25% more efficiency over double-pane windows with Low-E, and cost an additional $100-$200 per window. They’re worth considering for maximum efficiency, noise reduction near busy roads, or rooms with large window areas facing south or west.
How much more efficient are new windows vs. 20-year-old windows?
Modern windows with SmartSun Low-E4 glass are roughly 40-70% more efficient than windows from the early 2000s, depending on what glass technology those older windows used. The improvement is even more dramatic compared to single-pane or failed-seal windows.
Do window coverings help with energy efficiency?
Window coverings (blinds, shades, curtains) help, but don’t replace the performance of quality glass. They block some solar heat gain, but the heat is already inside your home at that point. Low-E coatings reflect heat before it enters, which is fundamentally more effective.
What is the difference between Low-E4 and SmartSun glass?
Low-E4 glass blocks 84% of UV rays and provides balanced heating and cooling performance. SmartSun glass blocks 95% of UV rays and is 70% more efficient in summer. For Virginia, where cooling costs exceed heating costs, SmartSun is the better choice.
How long do energy-efficient windows last?
Renewal by Andersen windows with Fibrex frames and Low-E glass are designed to last 40+ years while maintaining their energy performance. The Fibrex frame doesn’t warp or degrade, so the seal stays tight for decades.
A 20-year limited warranty backs the glass, frame, hardware, and installation.
See Which Energy-Efficient Windows Are Right for Your Home
Ready to find the best energy-efficient windows for your home? Mr. Rogers Windows and Doors offers free, no-obligation consultations, during which we’ll evaluate your current windows, discuss your priorities, and recommend the right combination of glass, frame, and style for your situation.
Schedule a consultation today!
Mr. Rogers Windows 📍 2100 Scenic Parkway, Suite 101, Chesapeake, VA 23323 📞 (757) 512-6242 🕐 Monday – Friday: 8:30am – 5:00pm | Saturday – Sunday: Closed
In Your Free Consultation: – Discuss your needs and priorities – See samples of all window styles – Review color and customization options – Get precise measurements – Receive detailed quote (valid 1 year) – No pressure, no obligation
Serving Hampton Roads Since 1986: Virginia Beach, Norfolk, Chesapeake, Suffolk, Newport News, Hampton, Portsmouth, Yorktown, Williamsburg, Smithfield, Gloucester, Elizabeth City, Moyock, Outer Banks, and surrounding communities.
Mr. Rogers Windows is Hampton Roads’ exclusive source for Renewal by Andersen replacement windows. We combine 39 years of local expertise with industry-leading products and factory-trained installation to enhance the comfort, efficiency, and value of your home.
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