How to Check for Window Leaks

As windows are often the culprit for both water and air leaks into the home, it’s important to do both a physical and visual inspection of your windows to prevent future damage.   It is quite simple to check windows for leaks.  By following these easy steps, you can ensure your home is protected from the elements and in turn, more energy efficient.  Even if your windows are relatively new, if they were not properly installed and insulated, you could be experiencing pesky window leaks in your home.

Double Hung

Physical Inspection of the Windows

Performing a physical inspection of your windows is the first step you should take in checking for air leaks.  Depending on the number of windows you have in your home, this is a relatively quick process and you only need a few supplies.

1) Close all your windows

This may seem obvious, but in order to best check windows for leaks, it is important that your windows are closed.  In addition, make sure to lock the windows as well in order to get the tightest seal possible.  Even if you are only checking the windows in one specific room, it’s a good idea to close the windows in other rooms as well to limit potential air flow. This will make the inspection you perform more accurate.

2) Turn off furnace and fans

To increase the accuracy of your inspection and best determine if you have any air leaks, you should turn off your home’s furnace or air conditioner.  Let the system cycle down so there is no additional air movement in the home.  You want your house as still as possible so turn off any floor fans, exhaust fans and any wall or window air conditioning units for the best results!Bad Window Installation

3) Light a candle

As the flicker of a flame or the flicker of smoke is the best way to determine if you have a leaky window, grab a lighter or some matches and light a candle.  Long, skinny taper candles work best, but pillar candles can work well too.

You just need something that you can securely hold in a steady fashion.  If you don’t have any candles, a stick of incense can work as well.  While there isn’t a lit flame with incense, the smoke would be enough of a visual cue.

4) Get moving around the window

Once your candle is lit, slowly move it around the perimeter, or edges of the window.  If you have a window with two operable sashes, like a double hung window or a sliding window, you could also move the candle along the place where the two sashes meet.  If you see the flame flicker or the smoke blow away from the window, you probably have a leaky window.  As you perform this part of the candle test, be sure to take caution to avoid any curtains or drapes which could catch fire.

Visual Inspection of the Windows

Not only is it a good idea to test window leaks from the inside, it is also important to perform a visual inspection of all your windows from both the inside and outside of your home.  This is especially true if you performed the candle test on a day without a lot of breezes. Even if your test showed only a handful of windows may have a potential leak, it is still a good idea to give them the visual once-over to see if there are any other contributors to a leaky window.

Interior Inspection

Board Up Windows

Pull back your window treatments and look all around the window for any obvious signs of daylight entering your home where there shouldn’t be.  If you do have curtains or drapes, do they move when the wind blows? Even the smallest gap could be a problem so take a good look around all the window’s edges and make a note to further inspect that window from the outside.

Exterior Inspection

Now it’s time to take a tour of the outside of your home and inspect your windows from the exterior.  Look for any gaps in the frame around your windows.  Check to see if there are any cracks in the caulking around the top, bottom or sides of the windows.  If your window is single paned, check all the putty between the panes of glass to make sure it’s not cracked.  If you notice any of these issues with your window, you are probably experiencing water or air leaks, if not both!

How to Fix Window Leaks

If you have in fact discovered that you do have an issue with leaks, you now need to know a few things you can do to fix a leaky window.

Reapply Caulk

One of the simplest fixes for a leaky window is to reapply caulk around the window.  The first step includes removing the old and dried out caulk.  This can be done best with a putty knife.  Then take your new tube of caulk and cut a hole in the tip at an angle, leaving the hole the same width of the gap you will be filling with new caulk.  Apply the caulk to the edges of the window and then smooth out and clean any excess.  Caulk is best applied outside when the temperature is over 45° and with low humidity.

Re-glaze Single Pane Windows

If you have old, single pane windows, you can also consider reapplying the putty that holds the glass in place.  Like caulking, you first need to remove the old, dried out putty.  Remove the glass and clean out the area in which it will be replaced.  Set the glass back in place on a bed of latex caulk.  Place glazing points into the wood.  You will then cover the perimeter of the glass with a heavy layer of glazing compound.  The last steps include using a putty knife to smooth the compound and then clean up.

Window Replacement

If DIY projects aren’t your thing or you don’t have the time to fix leaky windows, window replacement may be the route you want to take.  While there is a greater initial cost outlay to replace an entire window, a new window can provide even greater energy efficiency.  With double pane construction and professional installation, you can have someone else take care of the window leaks and eventually save money on your heating and cooling bills.

Now that you have learned how to check window leaks and what fixing them entails, you can make the best decision for you and your home to remedy the situation.  Regardless of the fix you choose, addressing leaking windows as soon as possible can reduce damage to your home, lower your energy bills and ultimately keep you more comfortable year round.

Share this article:


Get started with

*View our privacy policy

Or call us at 1-866-4FELDCO®
or visit one of our locations.


window privacy options

Beginner’s Guide to Installing Window Blinds

The Complete Beginner’s Guide to Installing Window Blinds Embarking on ...
remodeling after kids leave for college

Empty Nest Makeover: Redecorating After Kids Leave for College

The Empty Nest Makeover: A Guide to Redecorating After Kids ...
installing roof vents

Step-by-step Guide: Installing A Plumbing Vent Through Your Roof

Step-by-Step Guide to Installing a Plumbing Vent Through Your Roof ...
young woman cleaning her front door

How to Clean Your Entry Door

How to Clean Your Entry Door: A Step-by-Step Guide for ...
Sliding Patio Doors

Why Patio Doors Drop and How to Fix Them

Why Your Patio Door Drops & How to Fix It ...

Book Today and Save!

Over 500,000 homeowners have trusted Feldco with their windows, siding and doors. Click the button below and we’ll get started on your quote!