Doors
Doors keep out wind, rain, and intruders; it greets guests and provides light and fresh air; and it gets used every single day. For an exterior door to do a good job, its beauty must be more than skin deep—it’s the things you don’t see at first that determine whether an exterior door is ready for the long haul.
Overview
The Ins and Outs of Exterior Doors (Fine Homebuilding)
Exterior wood doors just under 2 inches thick don't offer much in the way of insulation, just R-2 or less. When weatherstripping is of poor quality or worn out, the effects are magnified. Doors don't represent a huge amount of wall area, but they can help nullify all the effort of insulating outside walls carefully. Insulated doors will help, along with high quality weather-stripping. Window area in doors, along with sidelights, should be kept on the small side or eliminated altogether.
Storm doors may seem like an antiquated idea, but they can be helpful in reducing energy losses while providing an extra weather barrier. They are especially useful when the primary door is exposed to the elements and not protected by a roof overhang or porch.
Steel
Steel is the least expensive option. You can find prehung steel entry doors for less than $150. The most expensive setup with sidelights and a transom could be $2000 to $3000. Steel paints nicely, but staining is difficult. Steel slabs also can’t be easily trimmed to fit an existing opening. This material isn’t a good idea for those living close to salt water, but in noncoastal areas, a regular paint job can keep rust at bay for decades.
Fiberglass
Fiberglass doors are in the middle to high end. Prices start at a few hundred dollars for a basic prehung door to $5000 to $10,000 for fully optioned models with sidelights and a transom. Fiberglass doors can be painted or stained to look like wood, and some models have a smooth skin, while others have a faux-woodgrain texture. The big pros of fiberglass doors is they don’t rust, and they offer the look of wood with little maintenance.
Wood
Wood doors have a wide price range. Six-panel pine doors can be found for a few hundred dollars, or you can commission a hardwood door that costs thousands. The great thing about wood is the wide variety of species and finishes available, but each comes with the universal downside of necessary ongoing maintenance. Because of this, wood doors should be covered by a storm door, roof, or generous overhang.