Insulating your Doors

It’s almost winter and we’re already beginning to feel the cold settle in here in New England. Now is the perfect time to start insulating your house before the real winter cold fronts start to hit us! In this four part series we will take a look at the most common places you suffer heat loss in your home. This blog will take a look at the best ways to weatherproof your doors for this upcoming winter, don’t forget that when it comes to doors, we offer a great variety of services, we even offer the best commercial door hardware services!

This is the second part in our series, if you missed the first part “Insulting Your Windows”, CLICK HERE to check it out!

Doors are some of the most highly trafficked areas in your house. The constant opening and closing of doors will jar the door, it’s frame, and the threshold. Over time this will lead to cracks around the trim, wearing down of the installed insulation, and worn out thresholds. Let’s Take a look at how to fix these common problems and save money this year!


Koopman caulking door frame

Start by looking at the trim all around your door frame. frame. Are there any gaps between the frame and the wall? Gaps will let heat escape and allow cold air to infiltrate your home. Does the caulking that is currently applied look old and cracked? Depending on the size of the gap, you’re either going to need a fresh bead of caulking or backing rod and caulking to complete the job.
Start by removing the old caulking with a scrapper. Make sure not to be so rough that you peel the paint away! One handy tip is to use a utility knife to very carefully score the caulking right where it meets the wall surface.  After that ready your caulk gun (which we talked about HERE in our last blog) and begin to apply the caulk at a 45º angle to the frame. Slowly work your way down on side of the frame. Dip your finger in warm water and then run it down the length of the new caulking to smooth it out. Wipe your finger off with a rag and continue on the other side and top of the door frame.  Now is also the time wipe off any excess caulking that has gotten onto either the trim or wall before it dries.

Backer Rod
If the gap between your trim and your wall is too big for a bead of caulking alone, you will need to use backer rod.  This foam material takes up space in gaps that would otherwise be too deep or too wide for a bead of caulking alone.   Backer rod comes in several sizes, so make sure that you select one that is the proper fit for your gap.  Once you’ve cut it to the appropriate length, apply a thin bead of caulking and you will have created a smooth, paintable finish.


The next step is to take a look at the current weatherstripping on door jamb. Many older doors used a strip of aluminum or other metal as insulation. These wear down over time and don’t insulate nearly as well as more recent weather stripping products.  They should be replaced.  There are two replacement options for a jamb seal; an easy to install but temporary strip or a permanent door jamb compression seal.

Temporary Jamb Seal
This is a low-cost and easier type of weather stripping to apply to your door. Begin by measuring the height of your doorstop and cut down the strips to the correct size (for the top and both sides). Place one end of the foam strip in the upper corner of either side of your door jamb and pull the edge of the adhesive covering off. Adhere the edge of the strip and slowly peel away the rest of the backing while simultaneously applying the weather strip to the jamb. Repeat this process for the opposite side and the top of the door.

Koopman-Lumber-EPDM-rubber-weatherstrip-insulationOne of the best and most affordable products we’ve seen is the M-D EPDM Weatherstripping  Subzero Weatherstrip. It’s an easy to apply, self-adhering weatherstripping made of EPDM rubber.  It has a longer life than most foam weatherstripping. For more info or to order one today CLICK HERE.

Permanent Jamb Seal
The more durable and longer lasting door weatherstrip is wooden door stop kit with vinyl and foam compression seals. Cut down the strips to match the size of your door frame and then hold the strip up against the closed exterior of your door. You want the vinyl part of the weatherstrip to be touching the door, but not pushing into it too hard as it might affect the seal of the door and the integrity of the weatherstrip. The flat section of the reinforced vinyl section should be lying flat against the door. Once you have it in place mark the holes with a pencil and get your screws ready (they should come with the weatherstripping kit). Open the door and screw the weatherstripping into door stop on top of the door.

Now repeat this process of marking each side of the door but don’t install the strips yet! First you’ll need to cut the top side of this weather strip at a 45º angle so that it will line up with the installed top piece. You can use a hacksaw to cut through the aluminum (if your strip has it) and a pocket knife to cut though the reinforced vinyl. Once it’s been cut, line your strip up to the holes and attach it to the door stop with the screws.

Koopman-Lumber-DM-vinyl-weather-compression-stripOur favorite for this type of weatherstrip is another product from M-D, the Vinyl Clad White Door Stop Compression Weatherstrip.  It’s a pre-primed, wood door stop with reinforced vinyl weather strips on it for maximum insulation. It looks great and will last for significantly longer than foam or rubber seals. For more information or to order on today, CLICK HERE.


The final step is to seal the gap between the bottom of your door and the threshold. To do this we’re going to install a door sweep on the bottom of the door. Start by measuring the gap between the bottom of the door and the threshold, and the length of the door. The first measurement will tell you how tall the sweep needs to be.  The second measurement will tell you what length to cut the sweep to.

There are 5 main types of door sweeps:


The 5 main types of door sweeps

Depending on the type of door you have you’ll be looking to get a different type of sweep. Steel or fiberglass doors generally use a slide on or snap in (the easiest to install by far). Wooden doors almost always use staple (or nail) on sweeps. The wrap around and L-shaped sweeps are versatile and can be installed on most doors.

Slide / Snap on
By looking at the bottom of the door, you’ll be able to identify these pretty quickly. A slide on weather strip is relatively easy to install; simply slide the old one off and slide the new one on. There will be tracks on the bottom of your door that help facilitate this.

Snap-on weather strip can be a little bit trickier. After pulling off the old door sweep, you will have to identify the kerf pattern (the kerfs are the slots on the underneath of the door) before purchasing a new one. The pattern will be a single or double kerf (how many rows) and the spacing profile will vary depending on what brand your door is. If you have any additional questions about a specific sweep, our experts at Koopman Lumber can hunt down any info for you. Just reach out to your nearest location over at www.koopmanlumber.com/locations.html

Wrap Around / L-Shaped
Remove the old bottom (if applicable) and make sure you purchase a sweep tall enough to make contact with the threshold. If, when you’re cutting the sweep to length, you cut off one of the pre-drilled screw holes, drill a hole near the edge for the most secure fit. Slide your new sweep into place and fasten it with the screws through the pre-drilled holes, then open and close the door to test the sweep’s fit.  These types of sweeps are a little bit more involved than the slide/snap-on style,  but are still relatively easy to install!

Staple on
This type of sweep is the most difficult to install because it requires you to take the door off, but it also provides a very secure finish. Start by removing your door by popping out the hinge pins, then lay it on it’s side. Carefully remove the old sweep and line up the new sweep along the door bottom. Working from the center to the edges, staple the sweep to the bottom of the door (you can also use wood nails on a wooden door). Working from the center out gives you the best control to prevent wrinkles from forming in the material. When you’re done, simply re-install the door.

Caution: doors can be heavy! Don’t endanger yourself handling a door all alone, get a friend to help you out!


Doors are a big factor in heat loss, but by installing good weather stripping, you’ll be saving money AND keeping your home warm. Watch for the next part of this insulating series – Garages! Next week, we’ll be looking at the best ways that you can save money in what is often the most neglected space in the house (and also a giant heat sink).

Thanks for reading our Project Book Series on insulting your home! If you have any additional questions then feel free to reach out to us at Koopmanlumber.com. Don’t forget to check out the next part in this series “Insulating Your Garage” by clicking here!

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