Energy-Efficient Doors for Utah: What to Look For

Why Doors Matter for Energy Efficiency

When homeowners think about energy efficiency, windows get most of the attention. But your exterior doors and their frames account for 10 to 15 percent of your home's total air leakage. A typical Utah home has three to five exterior doors, including the front entry, back door, and garage access. Each one is a potential source of heat loss.

The energy loss from doors comes in two forms. First, conduction: heat transfers directly through the door material from the warm side to the cold side. An uninsulated solid wood door has a U-factor around 0.50, meaning it loses heat about twice as fast as a modern insulated door. Second, and often more impactful, is air infiltration. Gaps around the door edges, worn weatherstripping, and improperly adjusted thresholds allow cold outdoor air to flow directly into your home.

Research from the Department of Energy shows that the air leakage component alone can account for the equivalent energy loss of a 6-inch-diameter hole in your wall. If you can see daylight under your door, feel a draft around the edges, or notice that the area near an exterior door is noticeably colder than the rest of the room, your door assembly is bleeding energy.

For a broader perspective on how doors fit into your home's overall energy picture alongside windows, see our complete energy-efficient windows and doors guide.

Door Energy Ratings Explained

Like windows, exterior doors carry NFRC ratings that measure their energy performance.

U-Factor

The U-factor for doors works the same way as for windows: lower numbers mean better insulation. Energy Star requires a U-factor of 0.21 or lower for opaque doors (doors without glass) and 0.27 or lower for half-glass doors in Climate Zone 5 (Utah). The best insulated doors achieve U-factors of 0.13 to 0.17, rivaling the performance of an insulated wall section.

Air Leakage

Door air leakage is rated in cubic feet per minute per square foot of door area. Look for ratings of 0.30 cfm/ft2 or lower. Some premium doors achieve 0.10 or lower, which means virtually no air movement through the closed assembly.

Solar Heat Gain Coefficient

SHGC applies only to the glass portion of doors with window inserts. For south-facing entry doors with decorative glass, a moderate SHGC of 0.25 to 0.35 allows some beneficial solar heat gain. For sliding patio doors with large glass areas, the same SHGC guidance as windows applies.

Door Materials Compared

The material your door is made of has the biggest impact on its energy performance, durability, and maintenance needs.

Fiberglass

Fiberglass doors have emerged as the gold standard for energy efficiency in cold climates. A fiberglass door with a polyurethane foam core achieves U-factors of 0.15 to 0.17 for opaque models, making it the best-insulating residential door available.

Fiberglass does not expand and contract with temperature changes the way wood does, which means it maintains a tight seal year-round. It does not rot, warp, crack, or rust. It can be stained or painted to mimic the look of natural wood grain. And it requires virtually no maintenance beyond occasional cleaning.

For Utah's climate, where doors face temperature swings of 100+ degrees between seasons and intense UV exposure at high elevation, fiberglass is the most reliable choice. Entry-level fiberglass doors start around $600 to $800 installed, with premium decorative models reaching $2,000 to $3,500.

Steel

Insulated steel doors with foam cores are the most affordable option for energy-efficient entry doors. An insulated steel door achieves U-factors of 0.17 to 0.20, which is strong performance at a price point of $350 to $700 installed.

The trade-off is thermal bridging. The steel skin itself is an excellent conductor of heat. In extreme Utah cold (below 10 degrees Fahrenheit), you may notice cold spots on the interior surface of a steel door, and in rare cases, slight condensation where the steel contacts the frame. Modern steel doors use thermal breaks to mitigate this, but they cannot eliminate it entirely.

Steel is also susceptible to denting and, if the finish is damaged, rust. In Utah's dry climate, rust is less of a concern than in humid regions, but it is still a possibility over decades of use.

Wood

Solid wood doors are the traditional choice and offer natural insulating properties. A 1.75-inch solid wood door has a U-factor around 0.40 to 0.50, which is significantly worse than insulated fiberglass or steel. Some manufacturers offer wood doors with insulated cores that improve this to 0.25 to 0.30, but they still lag behind fiberglass.

The bigger issue with wood in Utah is maintenance. Wood doors require repainting or restaining every 2 to 4 years to protect against moisture damage and UV degradation. Utah's intense high-altitude sun is particularly hard on wood finishes, especially on south-facing and west-facing doors. If you love the look of wood, consider a fiberglass door with a realistic wood-grain finish for the aesthetics without the maintenance burden.

Composite and Engineered Materials

Several manufacturers now offer doors made from composite materials that blend wood fibers with polymers. These doors offer better insulation than solid wood, better moisture resistance, and lower maintenance. Their energy performance typically falls between wood and fiberglass, with U-factors around 0.20 to 0.30.

Glass Inserts and Sidelights

Decorative glass panels in entry doors add curb appeal and natural light. They also reduce the door's overall energy performance because glass insulates far less effectively than a foam-filled core.

Minimizing the Energy Impact

If you want glass in your entry door, follow these guidelines:

Limit the glass area. Doors with glass panels occupying 25 percent or less of the door surface maintain strong energy performance. Full-glass or three-quarter-glass doors sacrifice significant insulation.

Insist on insulated glass. Decorative glass inserts should be double-pane or triple-pane with Low-E coatings and argon gas fill. Single-pane decorative glass panels have U-factors of 0.90 to 1.00, which creates an extreme thermal weak point.

Choose Low-E. Low-E glass in door inserts blocks UV radiation that fades your entryway flooring and furniture while maintaining most of the visible light transmission.

Sidelights

The narrow windows flanking many entry doors (sidelights) are often forgotten in energy discussions. Older sidelights are frequently single-pane and poorly sealed. If your entry includes sidelights, replace them when you replace the door. Many door manufacturers offer integrated door-and-sidelight systems with consistent energy ratings and coordinated weatherstripping.

Weatherstripping and Thresholds

Before committing to a full door replacement, evaluate the weatherstripping and threshold on your existing doors. In many cases, replacing worn weatherstripping and adjusting the threshold recovers 50 to 70 percent of the energy benefit of a new door at a cost of $20 to $60 per door in materials.

Signs Your Weatherstripping Needs Replacement

• Visible daylight around door edges when the door is closed
• Drafts felt near the door perimeter
• The door does not close with a firm, compressed seal
• Weatherstripping is cracked, flattened, or missing sections

Threshold Adjustment

Most adjustable thresholds have screws that raise or lower the threshold to maintain contact with the door bottom sweep. Over time, the sweep wears and the threshold settles, creating a gap. Raising the threshold until it contacts the sweep firmly and evenly eliminates under-door drafts.

If the threshold is damaged, warped, or corroded, replacement thresholds are available at any home improvement store for $15 to $40. Aluminum thresholds with thermal breaks are the best performers for Utah.

Patio and Sliding Doors

Patio doors present a unique energy challenge because of their large glass area. A standard 6-foot sliding patio door has approximately 40 square feet of glass, more than some entire bedroom window configurations. That much glass area demands the same energy attention as your windows.

Modern energy-efficient sliding patio doors use the same technology as windows: double-pane or triple-pane insulated glass with Low-E coatings and argon gas fill. The best units achieve overall U-factors of 0.22 to 0.28, with SHGC values appropriate for the exposure direction.

For west-facing patio doors, which are common in Utah homes designed to capture backyard sunset views, choose the lowest SHGC available. West-facing patio doors are the single largest source of summer solar heat gain in most homes.

French patio doors (hinged double doors) generally offer better air sealing than sliding doors because they compress against weatherstripping when closed, similar to casement windows. If energy performance is a priority and your opening accommodates them, French doors are the better choice for Utah.

Garage Doors and Energy Loss

If your home has an attached garage, the garage door may be the largest single opening in your building envelope. An uninsulated single-layer steel garage door has virtually no insulating value and allows cold air to fill the garage, which then transfers through the garage-to-house wall and door.

Insulated garage doors with polyurethane foam cores achieve R-values of 12 to 18, transforming the garage from an energy liability into a reasonable thermal buffer. If your garage shares a long wall with conditioned living space, an insulated garage door upgrade can reduce the heating load on adjacent rooms by 10 to 15 percent.

The cost of an insulated garage door runs $800 to $2,000 for a standard two-car door, including installation. Considering the large surface area (approximately 160 square feet for a two-car door), the cost per square foot of insulated surface is actually lower than most other building envelope improvements.

Choosing the Right Door for Utah

For most Utah homeowners, the priority order for door energy improvements is:

1. Replace weatherstripping on all exterior doors first. This is the highest-return, lowest-cost improvement.
2. Replace the front entry door with an insulated fiberglass model. The front door is typically the largest entry point and the one most exposed to weather.
3. Replace sliding patio doors with double-pane or triple-pane Low-E units, especially west-facing doors.
4. Upgrade the garage door to an insulated model if you have an attached garage with living space adjacent.
5. Replace secondary doors (back doors, side entries) last, as they are typically smaller and contribute less to total energy loss.

For security-focused features including smart locks, reinforced frames, and impact-resistant options, see our front door replacement guide on security and style.

Energy-efficient doors work best as part of a whole-building approach that includes quality windows, adequate insulation, and thorough air sealing. When these elements work together, they create a comfortable, efficient home that stands up to everything Utah's climate throws at it while keeping your energy bills under control.