A solid wood door will have an R-value of R-2 or R-3. An insulated steel or fiberglass will have an R-value that is twice as good — generally R-5 to R-6, but in some cases as high as R-7. European manufacturers of Passivhaus-certified doors advertise R-values as high as R-11.
A fiberglass front door is your best bet for peak energy efficiency. Fiberglass doors have an exceptionally insulating polyurethane foam core that provides a high R-value. The R-value is a standard measure of insulation effectiveness; higher numbers mean better insulation.
Fiberglass. Fiberglass exterior doors are among the strongest on the market. They're also some of the most energy-efficient. Fiberglass is a poor conductor of heat, making it energy-efficient on its own, but when insulation is added, it's hard to beat.
When it comes to energy efficiency, fiberglass exterior doors are one of the best options on the market. Fiberglass exterior doors are manufactured with a solid polyurethane foam core that insulates the door against extreme temperatures.
The best energy-efficient doors you can buy right now are the Emerson Therma-Tru fiberglass and Masonite Steel Primed doors. These doors have a polyurethane foam core – one of the most energy-efficient materials on the market – placed in the middle.
Fiberglass. Fiberglass wins for the choice of the most insulative exterior door choice. While they fill a fiberglass door with foam much like a steel door, its low maintenance feature makes it superior to steel.
Sliding doors are generally more energy efficient than French doors. This is because they are made of single panels of glass that don't allow energy or air to escape as compared to the French doors which have several panels.
Fiberglass doors are versatile and heavy-duty. They offer nearly three times as much insulation as solid wood or wood core doors for a much higher R-value or insulation effectiveness.
And steel can get hot when exposed to sunlight and high temperatures, which makes it a little less efficient than fiberglass. Verdict: While both steel and fiberglass are energy-efficient options, fiberglass outperforms steel in this area, making it a favorite door replacement option for many homeowners.
Fiberglass doors are superior insulators and are suited for many climates — hot or cold, wet or dry. Unlike steel doors in wet climates, they are not susceptible to rust. Unlike steel, fiberglass does not transfer heat, which makes it a better choice for areas with greater seasonal fluctuations in temperature.
Best Types of Energy-Efficient Doors
While fiberglass, aluminum and steel are great exterior door options, the best kind of energy-efficient interior door is veneer wood doors. While a solid wood door provides some insulation, doors with insulating cores are more energy-efficient.
With this in mind, modern aluminium doors offer the best sustainability features as they're 100% recyclable.
Close the gaps. Caulking and weatherstripping can help to seal gaps around the doorframe. Assuming your door is in good shape, most energy loss likely occurs in the spaces around the door, rather than through the door itself.
Fiberglass doors are naturally more weather-proof than wood or steel. While steel will not crack from cold weather, it is more susceptible to dents and chipping and requires quite a bit of upkeep.
Rigid foam board insulation is available in many materials, including polystyrene (R-3.8 to R-5.0), polyurethane (R-5.5 to R-6.5) and polyisocyanurate (R-5.6 to R-8.0). Since it has the highest R-value, rigid foam is typically reserved for foundations and basement walls.
Why do black doors add value to your home? 'The number one front door color that buyers will pay more for is black. A black door with a shiny finish may sell for up to $6,500 more than a similar house with a different colored door.
Steel Door Disadvantages
Denting and Rusting – While steel doors cannot warp they can be dented if hit by something, and if the paint on the door gets chipped off at the dent then rusting can develop with the metal being exposed to the moisture in the air.
Drawbacks of Fiberglass Exterior Doors
The disadvantages of fiberglass doors include: Price – While not as costly as some types of wood, fiberglass is one of the more expensive options on the market. Sizing – The material is difficult to trim, so it's not well-suited for exterior doors that aren't standard sizes.
Security. Steel can be an excellent option if you have security concerns. Since it's a heavy, tough material, steel entry doors are very difficult to break down. Fiberglass doors are still a pretty secure choice, but they're far more lightweight than steel and are easier to manipulate.
Wood, Steel and Fiberglass Exterior Doors
Most homeowners don't mind the upfront investment for wood because of its traditional look and natural appeal. A metal or steel exterior door is the most budget-friendly of the three. Fiberglass comes in a variety of styles and is very durable.
Self-adhesive weatherproofing strips are one of the quickest and easiest answers to how to insulate entry doors. Simply cut to size and stick around the door frame, to seal any gaps without interfering with the function of the doors.
The cons of sliding doors
Being a large expanse of glass, you may notice a build-up of dirt, grease and grime, made worse in homes with pets or children. However, this is easily overcome with regular cleaning, and is a small price to pay for uninterrupted views and natural light.
French doors have a wider door frame.
A sliding glass door frame is typically narrower than a French patio door frame, which means it will allow more natural light into your home. However, the wider frame on a French patio door is a more traditional style, which many homeowners desire.
Cost of French doors—and resale value
All in all, they're a good investment in your home, since they don't cost much but add significant resale value, so they almost pay for themselves.