DIY: How to reduce electric bills by caulking windows and doors


Check outside. Is it a sunny day with temperatures above 60 degrees? There won’t be many more of these before winter weather comes. What a perfect time to load a tube in a caulk gun and shoot a bead of air-blocking silicone or latex into the joints around windows and doors where energy waste can drive up your electric bill.

Home energy efficiency measures need not be complicated nor expensive. Simple, cost-effective solutions are available to anyone with marginal do-it-yourself skills. Middle Tennessee Electric (MTEMC), your trusted energy advisor, recommends caulking as a means of reducing air leaks that can drive up kilowatt-hour consumption during heating and air conditioning seasons.

Of all the residential energy efficiency fixes available, caulking is the cheapest and boasts a quick payback in terms of electricity savings.

Where and When to Caulk

Whether you live in a newly constructed home or one 10 years old, it makes sense to inspect the joints around windows and doors or a regular basis. The “joint” is an angle where two planes or types of material meet. The frames around windows and doors are examples. These joints need to be sealed to prevent infiltration of outside air and the loss of conditioned air from the home’s interior.

Caulk doesn’t last as long as some people think. Sunlight, the freeze-thaw cycle, rainwater, extreme heat, and dryness can cause sealant to crack, buckle and break away.

Visual inspection can reveal caulk failure. Another way is to observe from inside the house. Often light can be seen around window and door frames where the caulk is either insufficient or has started to fail. In the same way, drafts can be felt around the frames.

Also, a telltale sign of air leakage is what happens to curtains or drapes on windy days. If the fabric seems to move when gusts occur, it’s likely that air is getting inside. If windows that rattle when the wind blows, this too is a symptom of an air sealing problem.

Caulking is best done when there is no rain in the forecast and temperatures are above 50 degrees and below 90.

Tools Needed

To complete the job, you’ll need the following items found at your local hardware store.

  • Caulk Gun
  • Tubes of Caulk
  • Pocket Knife or Box Cutter
  • Putty Knife
  • Cleanup Rags
  • Container of Water

Before You Get Started

Ensure that old caulk has been stripped from the joints. Do not apply new caulk over old. This is where the putty knife will come in handy to loosen the old sealant. Clean all the exposed joints to remove dirt and dust before reapplying caulk.

Different types of caulk are made for particular applications: indoor-outdoor, interior only, kitchen-bathroom, colored, clear, paintable or not. The caulk might be acrylic, silicone, latex, adhesive, butyl rubber or elastomeric. All have different price points. Match the caulk to the job. Don’t hesitate to ask someone at your local hardware store or building supply center for advice.

Getting the Job Done

Now that your tools and tubes of caulk are at hand, the old caulk is gone, and the joints have been cleaned, here’s what to do:

  1. Using a knife or box-cutter blade, cut the tube’s plastic nozzle at an inward diagonal in the approximate diameter needed to fit the joint’s angle. Try to keep the cut within the tapered section of the tube. Use the piercing attachment on the caulk gun or a section of wire coat-hanger to break the seal at the base of the nozzle.
  2. Load the tube of caulk in the applicator gun. Slide the serrated rod forward until it is secure against the back of the tube. Turn the rod so the serrated section is upside-down and lever the caulk gun’s handle until you see caulk begin to emerge from the nozzle.
  3. Place the nozzle at the top of the joint, diagonal cut flush to the joint, and firmly squeeze, applying a bead of caulk by moving the applicator downward. Release the lever and squeeze again when the bead starts to get smaller.
  4. For horizontal joints, use the same technique, working from the direction you feel most comfortable.
  5. The next step is important. Wet you’re a fingertip with water and use it to smooth the caulk bead into the joint. Use rags to clean the excess caulk from your finger before resuming the process. This will compact and widen the sealant in the joint and make for a neater appearance.
  6. Clean up your tools per manufacturer’s instructions. Partially used tubes of caulk can be saved by inserting a plastic or wooden plug into the nozzle. Allow the new caulk to cure, according to the time suggested by the manufacturer. It should not be subjected to rain or freezing during this curing period.


MTEMC wants members to become more energy efficient and their homes to be more comfortable. Many DIY projects like caulking can be done with a minimum of cost, fuss, and mess. These are good first steps toward reducing energy waste.

As always, approach any home project with an eye toward safety, especially if ladders must be used. Stay away from electric lines and use tools with care. Our energy advisors are always happy to help with advice and information about energy efficiency programs offered by MTEMC. Check out our website or download the free myMTEMC mobile app for more information.

Looking for some more information about this project?

Here are some helpful links to help you get the job done.

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