Exterior Doors

Exterior Doors

Heat naturally flows from warmer spaces to cooler spaces. In the winter, heat flows from heated living spaces to the outdoors and to unheated spaces in your home such as attics, garages, and basements.  In the summer, heat flows from the outside into your home. When heat is lost or gained due to poor insulation, your heating and cooling systems must work harder to maintain a comfortable temperature in your home, resulting in higher energy costs.

Exterior doors are responsible for some of this heat transfer, so it is important to purchase replacement doors that are well insulated, and have a good air seal. Older wooden doors have an R-value of about 2 while the R-values of most steel and fiberglass-clad replacement entry doors with polyurethane foam cores range from R-5 to R-6 (not including the effects of a window.) For example: A 1-1/2 inch  thick door without a window offers more than five times the insulating value of a solid wood door of the same size

Door Ratings.  The National Fenestration Rating Council (NFRC) is a non-profit organization that determines the energy performance ratings of windows, doors and skylights. When purchasing an exterior door, look for the NFRC label on the product.  It lists the door’s performance ratings, including its R-value.

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How to buy?

Replacing an exterior door: A few things to consider

Material. Common materials for exterior doors are wood, steel, fiberglass, and composite materials. 

Steel doors are durable and offer good insulation.  A steel door with a polyurethane foam core has an R-value of about 6. Make sure any steel doors you buy are insulated, because if they are not, it will be worse than having a single-pane glass door!

Fiberglass doors insulate well, with R-values between 5 and 6, and can be more aesthetically pleasing than steel doors.

Composite doors are usually a bit more expensive.  These doors are made to look like wood, with a wood veneer placed over a steel door with a one-inch foam core.  Other models feature a wood panel over a ½ inch foam core.

Glazing. For exterior doors with windows or glass patio doors, you should consider investing in high-efficiency glazing.

There are many different types of glazing technologies, including: insulated (double-glazed, triple-glazed), low emissivity (Low-E) coatings, gas fills, heat-absorbing tints,  reflective coatings, and spectrally selective coatings. The NFRC label on the product lists the type of glazing used, so you can see how each type performs.
 
Common features to look for are low-E coatings and gas fills. Low emissivity, or low-E, coatings allow light to come through the window while reflecting the inside heat back into the room.  A double-pane window with a low-E coating can insulate as well as a triple-pane window with no low-E coating.

Gas fills are a technology that involves filling the space between each glass pane with harmless, inert gases (typically argon) that act as a better insulator than air. This improves the thermal performance of the door.

Patio doors. When replacing a patio door, note that sliding patio (glass) doors account for more heat loss than other types of doors.  They are prone to more air leakage because of the sliding seal. Consider installing a swinging patio door instead.

ENERGY STAR offers a wide variety of energy efficient exterior doors for your home. When purchasing an exterior door, you should first identify your ENERGY STAR climate zone to determine what door will be best for your area. The chart will help you determine which door will be most efficient for your home according to your climate zone.  To see a map with ENERGY STAR climate zones, click: ENERGY STAR Climate Zones

Next, you should look for the ENERGY STAR label on the product or ask the product manufacturer about ENERGY STAR qualified exterior doors.  An ENERGY STAR label should include the ENERGY STAR certification mark, a map indicating the regions in which the door is qualified, and a qualification statement.
   
To find an ENERGY STAR exterior door manufacturer, visit: Door Manufacturer Search

To find a store near you that sells ENERGY STAR exterior doors, visit: Store Locator

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How to improve the energy efficiency of existing doors
Storm Doors. If your existing exterior door is old but still in good condition, adding a storm door could help you save energy and money by reducing air leaks and providing better insulation.

Storm doors typically cost $200 or less, but this varies by type and performance rating.  Storm doors insulate by creating an air space between the storm door and your existing exterior door.  Their frames are usually made of aluminum, steel, fiberglass, or wood, and some may be insulated.  High quality storm doors use low-emittance (low-E) glass for greater efficiency.  Low-E glass increases a door’s resistance to heat flow, allowing for better insulating value.

Storm doors are meant to be a permanent addition to your home, but there is a temporary, do-it-yourself option.  If you have doors that are not opened for long periods of time, you can make a storm door by sealing your existing door from the inside with a plastic sheet mounted on a light-weight wood frame.  This is an inexpensive way to save energy and money. 

Note: Adding a storm door to a new, well-insulated door is not cost-effective since the energy savings are minimal.  Also, never install a glass storm door if your existing exterior door gets more than a few hours of direct sunlight each day. The glass will trap heat, which could damage your existing door.

Weatherstripping. Modern steel doors with polyurethane foam cores often do not require additional weatherstripping since they usually come with a thin magnetic strip that serves the same purpose.  For all other exterior doors, though, weatherstripping is a simple and affordable technique that involves placing a thin strip around your door to create a tighter seal.
 
Weatherstripping can be found at most hardware stores in a variety of materials, such as foam, rubber, felt, spring metal, and plastic.  Often, rubber and foam materials are the best choice since they stay flexible for years.  They are also inexpensive, easily replaced, and effective at sealing air leaks.
   
In general, when installing weatherstripping, you should:

Weatherstrip the entire door jamb.
Apply one continuous strip along each side and the top.
Make sure that the stripping meets tightly at the corners when the door is closed.
Make sure that the stripping is thick enough to press tightly on the door and the door jamb, but not so thick that it makes the door hard to close.
Use a “door sweep” at the bottom or replace the threshold with one that contains weatherstripping, and adjust so it is snug against the bottom of the closed door.
Some types of weatherstripping can be used for sliding patio doors as well, though it is difficult to achieve a tight seal without preventing the door from functioning properly.

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Benefits of Energy Efficient Exterior Doors
Comfort
Better insulation
Less fading of carpets, furniture and draperies
Reduced condensation
And, best of all, energy efficient exterior doors help you save energy, money, and the planet!

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