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Installing Insulation: Everything You Need to Know

No home is built to be air-tight, and nothing brings attention to this quite like the outside temperature dropping below freezing. With high Autumn and winter just around the corner, now’s the time to check up on your windows and doors and fix any drafty gaps. While it’s not possible to completely seal off your home from the outside air (or safe – you still need oxygen, no matter how cold it is out there), there are very simple measures you can take to better prepare your home for the cold.

Checking Existing Insulation

Chances are, you won’t have to install or repair insulation for all your doors and windows year to year, but you should check in on your existing insulation annually to see where repairs need to be made.

Most of the initial checks can be made with a simple visual inspection. If you can see daylight peeking through around your doors, windows, or through-the-wall or window ACs, then that is a sure sign those areas need to be insulated. Open your doors and windows and check existing weatherstripping for cracks and gaps, and check the caulking around stationary windows for cracks, as well.

Gently rattle your windows and ACs and if they are movable, that means there are gaps big enough to let in drafts. Finish your inspection by running your hand around the perimeter of your doors, windows, and AC units to feel for any extra gaps or cracks you may have missed.

After you’ve noted which areas of your home need attention, it’s time to think about exactly how to go about repairing or installing insulation.


Caulking is a super simple way of sealing cracks and spaces around your windows. The task is done in minutes and, if done correctly, can last you years.

Choosing Caulk

The task of insulating windows can be achieved with a simple, store-bought caulk. Choosing the right kind of caulk is important, however, as certain types (like acrylic caulk) are susceptible to shrinking and cracking and could end up causing you to have to re-caulk your windows year to year.

The best choice of caulk for a long-lasting seal is one that is permanently waterproof, 100% silicone, flexible, and specifically indicates that is shrink- and crack-proof.

While you will inevitably have to re-caulk your windows at some point, choosing the right kind will make it so the task only has to be done every 5-6 years.

How to Do It

To prepare the window for caulking, thoroughly clean the area and remove any old caulk with the side of a razor blade. Line the edges of the window with masking tape to ensure straight, clean lines.

Hold a caulking gun at a 45º angle and squeeze with even and consistent pressure all along the edges both in and, if possible, outside the home. Be careful not to squeeze too hard — when it comes to caulking, less is more! You really don’t need a lot of caulk to get the job done, and over-caulking your windows is wasteful and unnecessarily messy.

Remove the masking tape immediately after caulking and let sit for two to three minutes. Finally, use your finger or a wet caulk-smoothing tool to smooth and solidify your work. For best results, don’t let water hit the new caulking for at least 24 hours after application.


Weatherstripping is another option for insulating windows, and your best bet when it comes to insulating doors, as well.

Choosing Weatherstripping

There are so many different types of weatherstripping available that finding the option that’s best for you can feel a bit overwhelming. But here’s a little secret: there is no “best” option, and the kind of weatherstripping you choose has much more to do with your budget, location, and where you plan to install the insulation than the make of the weatherstripping alone.

The only types of weatherstripping you want to stay away from are felt and open-cell foam (as opposed to wrapped foam, which is perfectly fine). Though felt and open-cell foam types are generally less expensive than other types, they are inefficient at blocking airflow and are more susceptible to damage and tearing over a shorter period of time. Felt and open-cell foam types also have more “compression memory”, which means they do not retain their shape as doors and windows expand and contract with temperature changes. This guarantees that there will be drafty gaps for you to contend with once winter rolls around again, and so to avoid replacing your weatherstripping each year it’s best to stay away from felt and open-cell foam types altogether.

Weatherstripping comes in a variety of materials (silicone, plastic, metal, vinyl, rubber, aluminum, etc.) and forms (strips, tubing, sheets), and most newer doors actually come with weatherstripping already installed. When it comes time to replace your weatherstripping, it’s best to use the same kind the door originally came with. Check with the manufacturer and with your local hardware store; chances are they will either have or be able to order exactly what you need.

How to Do It

Measure along the top and sides of your door or window and cut the weatherstripping down to fit; most types of weatherstripping can be cut with a pair of scissors or metal snips. Ideally, measuring should be done before shopping so that the pieces you purchase are closer to the size you need, but when in doubt always purchase pieces that are slightly longer than what you think is required, just in case.

From here on out, installing weatherstripping is fairly simple, as most types are designed to snap or stick in place. Slide out any existing weatherstripping and replace with your new insulation.

Door Sweeps & Bottoms

All doors have slight gaps between them and the floor. Sometimes, the gap is small enough that installing some weatherstripping is enough to solve the problem. Often, though, a door sweep or door bottom is required to more efficiently block air and drafts.

Door Sweeps

Available in an array of makes (such as gold, brass, colored plastic, aluminum, and natural wood), door sweeps can be chosen to suit virtually any existing home decor. Installation is as simple as cutting the sweep to size and sliding under the door, making this method a popular choice for homeowners looking for a quick and easy solution to under-the-door drafts.

Because of the bristles, however, door sweeps are not ideal for areas where the door opens over carpet. Some homeowners also don’t prefer this method for how visible the door sweep is, and therefore decide to go with a different insulation solution.

Door Bottoms

Door bottoms are less visible than door sweeps but more suited to the task of insulating under the door than regular weatherstripping. Like all other types of weatherstripping, door bottoms are installed by simply cutting to size and sliding or screwing in place.

The most common types of door bottoms are U-shaped and L-shaped. U-shaped door bottoms wrap around the front and back of the door and slide into place, while L-shaped door bottoms extend up on only the inside of the door, and need to be screwed on. This means that door bottoms are slightly visible, but because they do not have bristles they are much less visible than door sweeps.

Door bottoms are suitable for use in spaces with both carpet and wood floors, and come in a variety of materials and colors, as well.

Through-the-Wall and Window ACs

Though they may do the trick in the summertime, through-the-wall and window air conditioners can be the bane of any homeowner’s existence in the winter for the way they let cold air seep indoors.

Covering the AC Unit

The quickest and easiest way to solve AC drafts is to cover the unit to block airflow. Make sure only to do this to the portion of your AC inside the home, however, as covering the air conditioner on the outside will cause condensation to build up and may lead to damage of the unit. While there are specific covers you can purchase to cover your AC it is just as effective to wrap the unit in a plastic tarp, securing the covering with bungee cords or duct tape.

Packing the AC Unit

The issue many people have with covering their AC is that plastic sheets and tarps do not make for particularly attractive home decor. Instead, many homeowners choose to pack the inside of the AC with fiberglass insulation.

To do this, simply remove the front grate of your AC and place a single piece of fiberglass insulation inside, cut to size. Replace the grate and secure in place with duct tape. It really is that easy.

Fiberglass insulation works well for both through-the-wall and window ACs, but window air conditioners may need a little extra attention, especially if they are equipped with accordion fans (which are incredibly thin) to keep them in place. Foam insulation boards, which can be purchased for cheap at any local hardware store, are great for this purpose. Simply cut the boards to size and fit them in place.

Another solution to dealing with a drafty air conditioner is to replace your wall or window unit with an HVAC system. HVACs, such as mini splits and PTAC units, double as a supplemental heat source, so there is no need to cover or pack the units in the wintertime.

If you have any further questions regarding insulating or replacing your AC unit, please do not hesitate to contact us at 1-877-847-0050 and speak to one of our qualified representatives.

Kristen Turner

Featured blogger for Total Home Supply.

3 thoughts on “Installing Insulation: Everything You Need to Know”

  1. Warm for the Winter: Insulating Your New Home - Walgrove says:

    […] your custom home builder will be able to do for you, but even if your house settles over the years, weatherstripping can be installed to fill any narrow […]

  2. Your Insulation Checklist - WillowTree says:

    […] most of your house is built, one of the finishing touches will be caulking window and door frames where needed to ensure that they are airtight. Because windows and doors are one of the biggest […]

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