Here’s how we look at windows: we start while examining the exterior of the house, looking for missing or damaged trim, deteriorated caulking, clouding due to lost insulating gas in double-pane windows, and bent, damaged or missing screens. We also check for flashing at the top of the window trim. Later on, while testing sprinklers, we note any heads that are spraying on the windows.

   Then, inside the home, we test the window locks, open the the window, and look for evidence of water intrusion—such as powdered or stained drywall/plaster and cracks due to movement of wet wood. We verify that bedroom windows have emergency egress size openings (big enough for a person to get out and a fireman with a backpack to get in).

   Also, while doing an infrared scan of the interior walls and ceilings we pay special attention to the areas surrounding each window. Most of the water intrusion damage observed is found in the wall framing below the window. 

    Here’s our top 10 list of common window defects:

1) Fogged windows due to lost insulating gas - An insulated window has two panes of glass with an inert gas sealed between them which provides the thermal insulation. When the seal is broken, through damage or deterioration, moist air and dust come into the center area and condense on the interior surface of the glass, eventually building up a hazy film. The leakage of the insulating gas also reduces the R-value of the window. See our blog post What is causing a foggy haze on my windows? for more on this.

2) Damaged wood trim on exterior - Seasoned carpenters like to talk about avoiding “water traps” when installing a window sill and trim. A water trap is any surface that is not sloped downward away from the wall and allows  rainwater to sit until it evaporates. These areas soon develop spots of wood rot and, if left unrepaired, allow water to enter the wall and begin to rot the wood framing. 

3) Cracked window panes - A cracked glass pane lets a minor amount of outdoor air into a home, but is mostly a safety concern. The fracture line shifts slightly over time and develops a sharp raised edge. Also, once the glass is cracked, any further stress will cause it to shatter.

4) Lack of exterior flashing - One hallmark of a quality building contractor is a strip of metal flashing that covers the top of the window trim and is secured behind the siding directly above the window, as in the photo below. It’s an effective deterrent to water entry at the top of the window. Some builders depend on a bead of caulk to seal the seam between the siding and top trim, but the caulk eventually fails.

5) Missing or damaged screens - Sometimes they are stored in the attic or a corner of the garage. We check around before declaring them missing. To learn more, go to our blog post Are openable windows required to have window screens? Will windows with no screens pass a home inspection?

 
6) Windows do not open or difficult to operate - We test each window that is reasonably accessible, and note any problems operating them. If the seller has furniture in front of the window, or delicate bric-a-brac on the window sill, sometimes can’t risk moving the belongings to test the window. 

7) Evidence of water intrusion - Staining, especially around or below the window sill, is our visual clue of water intrusion. Further evaluation with a infrared camera and/or moisture meter follows. 

8) Broken locks - Older window locks that don’t function can be due to damaged lock hardware or misalignment of the sash.

9) Missing operating handles - Can’t test the window without them.

10) Lack of tempered glass at required locations - We look for the “bug” (manufacturer’s tiny imprint on the glass indicating tempering). See our blog posts Where is safety/tempered glass required for the windows of a house? and How can I tell if a window or glass door is safety glass? for more on this subject.

   “Fenestration” is a fancy word that architects use to describe the door and window openings in a building. Because problems often show themselves around these openings, we look at each of them carefully.

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  To learn more about doors and windows, see these other blog posts:

• What causes sweating (condensation) on the inside of windows in the winter? 

• Is every exterior door of a house required to have a landing outside? 

• What are the small slots at the bottom of the outside of my window? 

• Why does condensation form on the outside of some windows and not others in the morning? 

• Why if the garage door track a white tube? 

• What is the raised metal plate on the floor under the garage door?

• Why do I have to hold down the button to close the garage door?  

• Should a front door swing in or out? 

• Why is pressure washing double pane windows an expensive mistake? 

• How many exit doors are required for a house?

• How many exit doors are required for a mobile/manufactured home?  

• Can a bedroom door open into the garage?

• What are the building code requirements for a door from the garage to the house?

• What is "low-E" window glass? 

• What does ANSI 297.1 on glass mean?

• Why is a double cylinder deadbolt lock on an exterior door a safety hazard?

• How can I check my garage door to make sure it is safe?  

• What is an egress window?

• Does a home inspector test all the windows and doors in a home? 

• How difficult is it to change a window to french doors or a sliding glass door?

• How do you determine if a door is left-handed or right-handed?

• Why are window security bars dangerous?  

• What do those numbers on the manufacturer's stickers in new windows mean?

• What does a home inspector check on an electric garage door? 

• What is the tempered label on glass at windows and sliding glass doors called?

• Do I need to have two exterior exit doors in my house? 

• When is safety glass required for windows at stairs and stair landings?

    Visit our DOORS AND WINDOWS and COMMON PROBLEMS pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.