Exterior Doors
An exterior door can contribute significantly to air
leakage in a home—as well as some heat transfer—if
it's old, not properly installed, and/or not
properly air sealed. This can result in energy
losses.
Here you'll find the following information:
Exterior Door Selection and Installation New exterior doors often fit and insulate better
than older types. If you have older doors in your
home, replacing them might be a good investment,
resulting in lower heating and cooling costs. If
you're building a new home, you should consider
buying the most energy-efficient doors possible.
When selecting doors for energy efficiency, it's
important to first consider their energy performance
ratings in relation to your climate and home's
design. This will help narrow your selection.
Types of Doors
One common type of exterior door has a steel skin
with a polyurethane foam insulation core. It usually
includes a magnetic strip (similar to a refrigerator
door magnetic seal) as weatherstripping. If
installed correctly and if the door is not bent,
this type of door needs no further weatherstripping.
The R-values of most steel and fiberglass-clad entry
doors range from R-5 to R-6 (not including the
effects of 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.
Glass or "patio" doors, especially sliding glass
doors, lose heat much faster than other types of
doors because glass is a very poor insulator. Most
modern glass doors with metal frames have a thermal
break, which is a plastic insulator between inner
and outer parts of the frame. Models with several
layers of glass, low-emissivity coatings, and/or
low-conductivity gases between the glass panes are a
good investment, especially in extreme climates.
Over the long run, the additional cost is paid back
many times over in energy savings. When buying or
replacing patio doors, keep in mind that swinging
doors offer a much tighter seal than sliding types.
Also, with a sliding glass door, it's impossible to
stop all the air leakage around the weatherstripping
and still be able to use the door. Also, after years
of use, the weatherstripping wears down so air
leakage increases as the door ages. If the
manufacturer has made it possible to do so, you can
replace worn weatherstripping on sliding glass
doors.
Installation
When you buy a door, it will probably be a pre-hung
frame. Pre-hung doors usually come with wood or
steel frames. You will need to remove an existing
door frame from the rough opening before you install
a pre-hung door. The door frame must be as square as
possible, so that the door seals tightly to the jamb
and swings properly.
Before adding the interior trim, apply an expanding
foam caulking to seal the new door frame to the
rough opening and threshold. This will help prevent
air from getting around the door seals and into the
house. Apply carefully, especially with a wood
frame, to avoid having the foam force the frame out
of square.
If needed, you'll also want to add weatherstripping.
Check the weatherstripping on your exterior doors
annually to see if it needs replacement.
Storm Doors
Adding a storm door can be a good investment if your
existing door is old but still in good condition.
However, adding a storm door to a newer, insulated
door is not generally worth the expense since you
won't save much more energy.
Storm door frames are usually made of aluminum,
steel, fiberglass, or wood (painted or not). Wooden
storm doors require more maintenance than the other
types. Metal-framed storm doors might have foam
insulation within their frames.
High-quality storm doors use low-emissivity (Low-E)
glass or glazing. Some doors have self-storing
pockets for the glass in summer, and an insect
screen for the winter. Some have fixed, full length
screens and glass panels that slide out of the way
for ventilation. Others are half screen and half
glass, which slide past each other. Some are
removable for cleaning, others are not. All of these
features add some convenience and higher costs.
Never add a glass storm door if the exterior door
gets more than a few hours of direct sun each day.
The glass will trap too much heat against the entry
door and possibly damage it.
Storm doors for patio doors are hard to find but
they are available. Adding one to a new,
multi-glazed, Low-E door is seldom economic.
Insulated drapes, when closed for the night in the
winter (or on sunny days in the summer) are also a
good idea.
Weather-stripping
You can use weather-stripping in your home to seal
air leaks around movable joints, such as windows or
doors.
To determine how much weatherstripping you will
need, add the perimeters of all windows and doors to
be weatherstripped, then add 5%–10% to accommodate
any waste. Also consider that weatherstripping comes
in varying depths and widths.
Before applying weatherstripping in an existing
home, you need to do the following (if you haven't
already):
• Detect air leaks
• Assess your ventilation needs for indoor air
quality.
Selection
Choose a type of weatherstripping that will
withstand the friction, weather, temperature
changes, and wear and tear associated with its
location. For example, when applied to a door bottom
or threshold, weatherstripping could drag on carpet
or erode as a result of foot traffic.
Weatherstripping in a window sash must accommodate
the sliding of panes—up and down, sideways, or out.
The weatherstripping you choose should seal well
when the door or window is closed while allowing it
to open freely.
Choose a product for each specific location. Felt
and open-cell foams tend to be inexpensive,
susceptible to weather, visible, and inefficient at
blocking airflow. However, the ease of applying
these materials may make them valuable in
low-traffic areas. Vinyl, which is slightly more
expensive, holds up well and resists moisture.
Metals (bronze, copper, stainless steel, and
aluminum) last for years and are affordable. Metal
weatherstripping can also provide a nice touch to
older homes where vinyl might seem out of place.
You can use more than one type of weatherstripping
to seal an irregularly shaped space. Also take
durability into account when comparing costs. See
Table 1 below for information about the common types
of weatherstripping.
Table 1:
Common Weatherstripping
Weatherstripping
Best Uses
Cost
Advantages
Disadvantages
Tension
seal:
Self-stick plastic (vinyl) folded along
length in a V-shape or a springy bronze
strip (also copper, aluminum, and stainless
steel) shaped to bridge a gap. The shape of
the material creates a seal by pressing
against the sides of a crack to block
drafts.
Inside the track
of a double-hung or sliding window, top and
sides of door.
Moderate; varies
with material used.
Durable.
Invisible when in place. Very effective.
Vinyl is fairly easy to install. Look of
bronze works well for older homes.
Surfaces must be
flat and smooth for vinyl. Can be difficult
to install, as corners must be snug. Bronze
must be nailed in place (every three inches
or so) so as not to bend or wrinkle. Can
increase resistance in opening/closing doors
or windows. Self-adhesive vinyl available.
Some manufacturers include extra strip for
door striker plate.
Felt:
Plain or reinforced with a flexible metal
strip; sold in rolls. Must be stapled,
glued, or tacked into place. Seals best if
staples are parallel to length of the strip.
Around a door or
window (reinforced felt); fitted into a door
jamb so the door presses against it.
Low
Easy to install,
inexpensive.
Low durability;
least effective preventing airflow. Do not
use where exposed to moisture or where there
is friction or abrasion. All-wool felt is
more durable and more expensive. Very
visible.
Reinforced
foam:
Closed-cell foam attached to wood or metal
strips.
Door or window
stops; bottom or top of window sash; bottom
of door.
Moderately low
Closed-cell foam
an effective sealer; scored well in wind
tests. Rigid.
Can be difficult
to install; must be sawed, nailed, and
painted. Very visible. Manufacturing process
produces greenhouse gas emissions.
Top and bottom
of window sash; door frames; attic hatches
and inoperable windows. Good for blocking
corners and irregular cracks.
Low.
Extremely easy
to install. Works well when compressed.
Inexpensive. Can be reinforced with staples.
Durability
varies with material used, but not
especially high for all; use where little
wear is expected; visible.
Rolled or
reinforced vinyl:
Pliable or rigid strip gasket (attached to
wood or metal strips.)
Door or window
stops; top or bottom of window sash; bottom
of a door (rigid strip only).
Low to moderate.
Easy
installation. Low to moderate cost.
Self-adhesive on pliable vinyl may not
adhere to metal; some types of rigid strip
gaskets provide slot holes to adjust height,
increasing durability. Comes in varying
colors to help with visibility.
Visible.
Door sweep:
Aluminum or stainless steel with brush of
plastic, vinyl, sponge, or felt.
Bottom of
interior side of in-swinging door; bottom of
exterior side of exterior-swinging door.
Moderate to
high.
Relatively easy
to install; many types are adjustable for
uneven threshold. Automatically retracting
seeps also available, which reduce drag on
carpet and increase durability.
Visible. Can
drag on carpet. Automatic sweeps are more
expensive and can require a small pause once
door is unlatched before retracting.
Magnetic:
Works similarly to refrigerator gaskets.
Top and sides of
doors, double-hung and sliding window
channels.
High
Very effective
air sealer.
Tubular
rubber and vinyl:
Vinyl or sponge rubber tubes with a flange
along length to staple or tack into place.
Door or window presses against them to form
a seal.
Around a door.
Moderate to
high.
Effective air
barrier.
Self-stick
versions challenging to install.
Reinforced
silicone:
Tubular gasket attached to a metal strip
that resembles reinforced tubular vinyl
On a doorjamb or
a window stop.
Moderate to
high.
Seals well.
Installation can
be tricky. Hacksaw required to cut metal;
butting corners pose a challenge.
Door shoe:
Aluminum face attachment with vinyl C-shaped
insert to protect under the door.
To seal space
beneath door.
Moderate to
high.
On the exterior,
product sheds rain. Durable. Can be used
with uneven opening. Some door shoes have
replaceable vinyl inserts.
Fairly
expensive; installation moderately
difficult. Door bottom planning possibly
required.
Bulb
threshold:
Vinyl and aluminum
Door thresholds
Moderate to
high.
Combination
threshold and weatherstrip; available in
different heights.
Wears from foot
traffic; relatively expensive.
"Frost-brake" threshold:
Aluminum or other metal on exterior, wood on
interior, with door-bottom seam and vinyl
threshold replacement.
To seal beneath
a door.
Moderate to
high.
The use of
different materials means less cold
transfer. Effective.
Moderately
difficult to install, involves threshold
replacement.
Fin seal:
Pile weatherstrip with plastic Mylar fin
centered in pile.
For aluminum
sliding windows and sliding glass doors.
Moderate to
high.
Very durable.
Can be difficult
to install.
Interlocking
metal channels:
Enables sash to engage one another when
closed
Around door
perimeters.
High.
Exceptional
weather seal.
Very difficult
to install as alignment is critical. To be
installed by a professional only.
Application
Weatherstripping supplies and techniques range from
simple to the technical. Consult the instructions on
the weatherstripping package. Here are a few basic
guidelines:
• Weatherstripping should be applied to clean, dry
surfaces in temperatures above 20°F (-7° C).
• Measure the area to be weatherstripped twice
before you cut anything.
• Apply weatherstripping snugly against both
surfaces. The material should compress when the
window or door is shut.
When weatherstripping doors:
• Choose the appropriate door sweeps and thresholds
for the bottom of the doors.
• Weatherstrip the entire door jamb.
• Apply one continuous strip along each side.
• Make sure the weatherstripping meets tightly at
the corners.
• Use a thickness that causes the weatherstripping
to tightly press between the door and the door jamb
when the door closes, without making it difficult to
shut.
For air sealing windows, apply weatherstripping
between the sash and the frame. The weatherstripping
shouldn't interfere with the operation of the
window.
