My new windows seem drafty and I haven’t seen a decrease in my energy costs. What is the problem?

Identify Your Home’s Drafts
CHECK FOR OBVIOUS ISSUES. You’ll need to identify these less-obvious air leaks to make an impact on your energy bills. You can do that yourself, with a careful visual inspection inside and out: Look for gaps and cracks at the common points of air leakage (e.g., knee walls, dryer vents, outdoor faucets, attic hatches, sill plates) and pay close attention to the building envelope — the outer walls, doors and other openings of your home. Take notes of any cracks, gaps or other openings, so you can return and air-seal them later.

You can also perform a simple test to supplement your visual inspection. One simple method is a DIY smoke test:
Pick a cool and windy day, and turn off all appliances or stoves that create air disturbances.
Shut all windows, doors and fireplace flues.
Carefully light a stick of incense and hold it near any potential points of air leakage (see the common points of air leakage list above).
If the smoke begins moving unsteadily back and forth, or if it’s sucked out of the room or blown into it, you have an air leak.

Drafts vs. Convection

Windows can draft for a variety of reasons such as cracked caulk, improper window locking, interlocks that are not lined up to seal properly, damaged or missing weather stripping, and poor insulation within the interior walls. These types of problems are easy to remedy.

However, windows may seem “drafty” for another reason; namely a process known in physics as convection. Convection can lead you to believe that your windows are drafty. Convection occurs when air gives up its heat to the cooler glass and sinks towards the floor. This movement sucks new, warmer air toward the glass that is in turn cooled, creating a draft. What you are actually experiencing is the process of warm air forcing colder air to move due to differing density properties. Heated air circulates through the home. When it reaches window glass it effectively pushes the existing cold air off of the glass.

This is an easy experiment and example of how convection works: Fill a glass with ice and water. Let it stand for about ten minutes. When you return, place your hands around (but not touching) the glass. You will feel cold air on your hands as warm air pushes it away from the glass surface. Convection is actually proof that your new windows are working well and energy efficient.

Tips to Reduce Convection: Leave your blinds or window treatments open about a ¼ inch, so that heated air can reach the glass. Make sure that your heat register exchanges are not obstructed by couches or other furnishings.