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.
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.
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.
Cold. The best exterior doors for cold weather are well-insulated ones. When choosing a door for the cold, look for fiberglass insulated doors, solid wood doors, metal insulated doors, and other heat-trapping materials.
Wooden Doors
Being naturally insulating, they are excellent at retaining heat inside. For interior or external doors, a solid wood door is an excellent option for helping to keep your home warm.
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.
Steel doors traditionally are foam filled and have a higher r-value than wood or glass. For many, the limited design choices available in steel doors coupled with the maintenance requirements make steel a poor exterior door choice.
Exterior Door Factors for Cold Weather
While some homeowners opt for steel, the material's high thermal conductivity makes it important to find a steel door with the best interior insulation. For homeowners who seek a traditional wood door, a solid wood door is the best option for keeping out cold air.
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.
For hot weather, you'll need a front door able to withstand constant heat. A thermally broken door will keep the heat outside and the cool inside of the house. This door can be made of any material, but wrought iron and fiberglass are the most common options.
The most popular materials for an exterior door are wood, steel and fiberglass. 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.
The R-values of most steel and fiberglass-clad entry doors range from R-5 to R-6, excluding a window. For example, a 1-1/2 inch (3.81 cm) thick door without a window offers more than five times the insulating value of a solid wood door of the same size.
Built with a polyurethane foam core that offers up to four times the insulating R-Value of wood, Therma-Tru fiberglass doors insulate against cold and heat for exceptional energy efficiency. (Comparison of fiberglass to wood doors, both without glass.)
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.
Fiberglass doors come with foam insulation that, combined with their durability, makes them more energy efficient than wood doors. This insulation helps to keep hot air from escaping the home in the winter, as well as preventing drafts.
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.
Add insulation to doors and windows
If you can access the area behind the window or door trim, adding batt insulation or spray foam insulation is one of the best ways to insulate doors and windows for winter because it can keep cold air from coming through the window.
A thermally broken door uses thermal breaks to keep exterior temperatures from entering the house. The thermal break material is placed inside the door's structure, creating a thermally insulated barrier. It also prevents heat loss, an essential feature for extremely cold areas where heating is needed for long periods.
Rigid foam insulation packs in more R-value per cubic inch than fiberglass insulation does. If conserving energy is your main goal and there are no other influencing factors such as moisture, rigid foam may be your first choice.
Depending on where you live and the part of your home you're insulating (walls, crawlspace, attic, etc.), you'll need a different R-Value. Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.
Storm doors save energy by adding insulation to your home.
Because they add that extra layer and help prevent your temperature-controlled air from escaping, using storm doors may help decrease the amount of time you have to run your heater or AC unit.
The door type with the most secure frame will be a composite door. Composite doors are made of multiple materials (usually wood, metal, and PVC), which makes them very strong and durable – therefore increasing security levels as well as more weather resistant.
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.