Your home’s front door has a lot to handle. It needs to keep the harsh weather out, be maximally energy efficient, provide security, and look at least reasonably good. Oh, and fit your budget, too. You’ll have three choices of materials: steel, fiberglass, and wood. Each has its pros and cons, and you should definitely go to a home center and look them all over, up close and personal. For this to be a sustainable choice, this door needs to be in place for decades. But first, let’s look at what makes for energy efficiency and sustainability in a front door.

What Makes An Energy Efficient Door

Doors that are energy efficient are both well sealed and non-conductive; that is, they don’t transfer very much heat or cold from inside to outside and vice versa. We can know the energy rating of many doors thanks to both ENERGY STAR and the National Fenestration Rating Council (NFRC). The NFRC is an independent non-profit that tests and rates doors, windows, and skylights. At the ENERGY STAR link, you’ll find information about rebates available in your area, as well as information about tax credits in effect thanks to the Inflation Reduction Act. You can claim $250 for one door or $500 for two doors!

According to the U.S. Department of Energy, doors, windows, and skylights can gain and lose heat in a few different ways, such as:

• “Direct conduction and convection heat transfer through the glass or multi-layer glazing and framing
• Thermal radiation into a house and out of a house from room-temperature objects, such as exterior walls and windows, people, equipment, furniture, and interior walls
• The solar radiation into a house, which is converted to heat when absorbed by building surfaces
• Air leakage through and around them.”

There’s a lot more information at that site about window U-factors, solar heat gain coefficient (SHGC), and sunlight transmittance. It can get a bit wonky, but what’s most important to know is that a door with more glass will have a lower insulating value than a solid insulated door. Even more important, though, is top-notch weatherstripping for complete air sealing.

Standard steel and fiberglass entry doors will range from R-5 to R-6 in their insulating value, while a solid wood door will be about R-2. Engineered wood doors, though, can be built like a fiberglass-clad door and have an R-5 insulation value. The R-value is the capacity of an insulating material to resist heat flow; the higher the R-value, the greater the insulating power.

If you choose a door with glass, three details will matter a lot: the size of the panes, getting double-pane or triple-pane windows, and getting windows with Low-E coatings to reduce the heat transfer.

What Makes A Sustainable Front Door?

This is where it gets a little more complicated and nuanced. Steel and fiberglass doors come out ahead for energy efficiency compared to solid wood doors, but solid wood doors hold less embodied energy than steel and fiberglass doors. In other words, solid wood doors are “built” rather than “manufactured.” An engineered wood door is probably somewhere in the middle.

Steel is often recycled, though, so that brings it up a notch. Plus, at the end of its life, the steel will probably be recycled again, so there’s another point. The rest of it is the wooden frame and foam insulation; that will probably be landfilled, but who knows? Fiberglass doors can also be made of recycled materials, and fiberglass is a relatively low-energy product made from sand.

Overall, it looks like all of these three materials can be sustainable and qualify for LEED points, so they are acceptable in LEED projects. LEED is the green building standard developed by the U.S. Green Building Council. I found a lot of manufacturer’s claims, not good data, so I’m calling it a tie for now.

Material Choices In Doors

Whatever material you choose, you’ll see a variety of architectural styles, so rest assured you can find something you like in the material you prefer. You can buy all three types of materials as just the door itself, which is called a “slab” or a “blank,” or you can get them prehung. Some prehung doors come with the outer wood trim, called “brickmould,” and some don’t.

Steel Doors

Steel doors are great because they will have a magnetic strip that acts as weatherstripping, similar to a refrigerator door. They are as strong as can be and not that heavy, as they’re essentially a wood frame with polyurethane foam insulation and a steel skin. The potential issue with steel doors is denting, although you can fix the dents as you fix dents in your car. Sand the area, fill it with putty, sand the putty, and then paint the whole door.

At the world’s largest home improvement retailer, 36-inch faux six-panel steel doors are popular and start at about $275 for the prehung version in a primed finish, which has a 10-year warranty on the door slab. For just about the same price, I’m also seeing a similar door with a “fanlight,” which is a half-circle, at the top that looks quite nice. Naturally, they have thousands of choices, but that seems like a reasonable starting point for a prehung door.

Fiberglass Doors

Fiberglass doors offer some clear advantages. They won’t dent or rust like steel can, and they won’t warp, rot, or split like wood can. They take both paint and stain finishes well, and you can get a factory-applied finish, as well. At the big retailer, a standard 36-inch prehung door is just over $300 and has a limited lifetime warranty on the door slab. The next step up is a 9-light door for $379, so you definitely have to spend more across the range with fiberglass. I think they’re worth it, though.

Wooden Doors

As I mentioned earlier, you can get traditional solid wood doors and also engineered wood doors that are built much like a fiberglass door. Solid wood doors can offer a beautiful custom touch, but I see the drawbacks as outweighing the beauty. If you live in a place with large swings in temperature and/or humidity, solid wood doors will show some expansion and contraction that you might notice as the door sticking shut. The big retailer has a 36-inch prehung version in alder with a traditional style for just under $1000 and a one-year warranty. Plus, the warranty includes many stipulations, such as a certain amount of overhang so the sun doesn’t hit the door. That doesn’t seem very durable. It sounds like an interior product more than a front door.

Engineered wood doors, however, should act more like a fiberglass door and if they have a great factory finish, that could be an option. Right now, though, I don’t see one to offer as a comparison, which leads me to believe they are more of a boutique product.

Any wood doors should carry some sort of certification, such as those by the Forest Stewardship Council (FSC) or Sustainable Forestry Initiative (SFI).

A Door Is As Good As Its Installation

s your choice. Finally, precise and thorough installation of your new door is a must. This is a straightforward job, typically, but if you're working on an older home, you may have to shim and caulk a fair bit to get it right. Here's how the masters do it.

Fortunately, You Have Options

Both steel and fiberglass doors can give you excellent air sealing, about the same R-value, and stay in service for a couple of decades, if not more. They’re made for the daily grind. Wood has its place, too, but it’s always your choice.