Fall Is The Best Time To Weatherstrip Your Doors!

Weatherstripping
You can use weatherstripping 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.

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.