The Standards of Practice of the two national home inspector associations differ on what is required when examining insulated windows. The International Association of Certified Home Inspectors (InterNACHI) expects inspectors to call out any windows with clouded glass. Here’s how it is stated: "The inspector shall report as in need of correction any window that was obviously fogged or displayed other evidence of broken seals.” The American Society of Home Inspectors (ASHI), on the other hand, excludes examination for this defect: "The home inspector is not required to inspect coatings on and the hermetic seals between panes of window glass."

    It’s important to note that the InterNACHI standard specifies windows that are “obviously fogged” should be caught by the inspector. Fogging of the interior surfaces between the panes of glass is due to dust deposits from the air intrusion, and it’s about the only way that the loss of insulating capability can be observed. 

    The problem for an inspector is that windows do not immediately become clouded after loss of their gas. It can take a year or more before the first faint evidence begins to appear and, in the early stage, can only be observed when carefully looking at the glass obliquely and/or sunlight is hitting the glass obliquely. Because of this, it is possible that evidence of the lost gas was invisible at the time of the home inspection, but becomes observable several months later by the homebuyer—followed by an angry “the home inspector should have seen this” phone call.

    Repairing this defect can be expensive. It is possible to eliminate the fogging by removing one of the panes of glass, cleaning the surfaces and reinstalling the glass. Or simply leaving only one pane in place. But either solution does not regain the insulating ability of the window, which is only possible by window or sash replacement. 

    Also, see our blog posts How do you keep double-pane insulated windows from from getting cloudy? and Should I buy a house with double-pane insulated glass windows that are clouded? and What is causing a foggy haze on my windows? and How can I tell if a window or sliding glass door is double or triple pane (insulated) glass? and Why is pressure washing double pane windows an expensive mistake? 

    Click on any of the links below to read other articles about what is required to be included, or not, in a home inspection:

AFCI •• Air conditioner •• Ants •• Appliance recalls •• Appliance testing •• Attic •• Awnings •• Barns and ag blgs. •• Bathroom exhaust fan •• Bonding •• Carpet •• Ceiling fans •• Central vacuum •• Chimneys •• Chinese drywall •• Clothes dryer •• Dryer exhaust •• CO alarms •• Code violations •• Condemn a house •• Crawl space •• Detached carport •• Detached garage •• Dishwasher •• Docks •• Doors •• Electrical •• Electrical panel •• Electromagnetic radiation •• Fences •• Fireplaces  Furnace •• Garage door opener •• Garbage disposal •• Generator •• GFCIs •• Gutters •• Ice maker •• Inspect in the rain •• Insulation •• Insurance •• Interior Finishes •• Grading & drainage •• Lead paint •• Level of thoroughness •• Lift carpet •• Low voltage wiring •• Microwave •• Mold •• Move things •• Help negotiate •• Not allowed •• Outbuildings •• Paint •• Permits •• Pilot lights •• Plumbing •• Plumbing under slab •• Pools •• Questions won't answer •• Radon •• Range/cooktop •• Receptacle outlet •• Refrigerator •• Reinspection •• Remove panel cover •• Repairs •• Repair estimates •• Retaining walls •• Roaches •• Rodents •• Roof •• Screens •• Seawalls •• Septic loading dye test •• Septic tank •• Sewer lines •• Shower pan leak test •• Shutters •• Sinkholes •• Smoke alarms •• Solar panels •• Specify repairs •• Sprinklers •• Termites •• Toilets •• Trees •• Troubleshooting •• Wall air conditioners •• Walk roof •• Washing machine •• Water heater •• Water pressure •• Water shut-offs •• Main water shut-off •• Water softener •• Water treatment systems •• Well •• Windows •• Window air conditioners •• Window blinds •• Wiring 

• • • • • • • • • • • • • • • • • • • • • • • • • • • 

  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 is 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? 

• How can I tell if a window or glass door is safety glass? 

• What are the code requirements for safety tempered glass for doors?• 

• Should a front door swing in or out? 

• How many exit doors are required for a house?

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

• Are openable windows required to have window screens? Will windows with no screens pass a home inspection? 

• 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 are the common problems you find inspecting windows?

• 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 "DOES A HOME INSPECTOR…?” pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.