There are many perspectives when you look at windows.  Depending upon your perspective is where you find yourself.  If you are the housekeeper, you are worried about keeping them clean.  If you are a small child you are looking at the big world out there.  If you are the homeowner you may be looking at one of the most expensive replacement items in the home.  

If you are the home inspector you are looking at a very complex and diverse system that has deliberately placed a hole in the exterior envelope for the sole reason of making the home less efficient, less water and weather tight, and has a huge potential of liability or call-backs.           

Before you can really sit down and start to discuss the construction, installation, maintenance, failures or any other features of windows it is only right to look at the industry standards and understand what the home inspector is actually supposed to look at and inspect.

American Society Of Home Inspectors (ASHI)


4.1 The inspector shall:

  1. inspect:
    1. wall coverings, flashing, and trim.


10.1 The inspector shall inspect:

   D.  a representative number of doors and windows.

International Association of Certified Home Inspectors (InterNACHI)

3.2. Exterior

I. The inspector shall inspect:

C.  a representative number of windows;

3.10. Doors, Windows & Interior

I. The inspector shall inspect:

  1. a representative number of doors and windows by opening and closing them;

Both of these standards have one thing in common, they both talk about a representative sample.  The rest of it is up to experience and background.  This leaves a great deal up to each individual to determine what their professional expectations are, as well as what the client expectations are.  This why it is important to have a good thorough understanding of windows, not only the functionality but where the potential failures might be as well.

Gaining a good understanding has to begin with understanding the basic styles of windows.

  • Single Hung – There is a top and bottom sash but only the bottom sash moves or opens and closes.
  • Double Hung – There is a top and bottom sash and both the top and the bottom sashes move or open and close.
  • Arched Window –  Typically a fixed or non-moving pane of glass with rounded tops that add an architectural design element.
  • Awning Window – These are ideal in climates with a lot of rain.  They have a sash or window that opens upward like an awning.
  • Bay Window – Bay windows protrude from an exterior wall and create a small shelf in the home. Bay windows rely on flat windows set into an angled frame that are built out of the home.  These can be casement, fixed, single or double hung windows.
  • Bow Window -Bow windows rely on custom curved windows that create a circular area along the outside of the home. Depending on the amount of window panels you want to use to create the curved bow window, a bow window can sometimes run more expensive than a full bay window.
  • Casement Window – Casement windows swing out to the side or up to open. This allows the window to be constructed of solid glass and offers a less obstructed view overall. 
  • Garden Window – Garden windows are essentially mini bay windows that are meant for plants. They’ve earned their name because they act like tiny little greenhouses that protrude from the inside of your home.
  • Glass Block Window – Most commonly, glass block window types are frosted or adorned with a patterned design, which simultaneously provides light and privacy. They are ideal for use in bathrooms, basements, and other private spaces.
  • Hopper Window – Hopper windows open from the top and usually crank open to tip down. They make efficient use of compact spaces, which is why they’re commonly found in basements or bathroom. These windows can open inward or outward depending on the need or design.
  • Jalousie Window – Jalousie windows are a unique window style that splits into many different slats of metal or glass. The windows open like a set of blinds. Simply crank the lever and the slats tilt to the side, which creates a series of gaps for air to flow through.


  • Picture Window – Picture windows are fixed windows that can not be opened. Picture windows are large window types that don’t have any breaks or visible frames, resulting in an unobstructed beautiful view.
  • Round Circle Windows -Round, half round, elliptical, or oval—the the round circle window category encompasses many different shapes that add architectural interest to your home. In particular, round windows give your space a nod to historical decor, such as Victorian or Gothic era structures. 
  • Skylight Window – Skylights are typically found on the roof and add an excellent window style option to those looking for more natural light into the home.  These windows can be fixed or moving.
  • Sliding Windows -Sliding windows have two sections that are usually made from single windows, and one of the sections slides horizontally overtop of the other to open or close. 
  • Storm Windows -Storm windows are exterior windows that install right in the same frame as your current windows. Storm windows add another layer of blocking out drafts and heat loss perfect for when cold weather rolls in. Storm windows are also perfect for areas who often get inclement weather.
  • Transom Windows – A transom window is the decorative windows that you see installed above doors in upscale homes, or even above other windows in some instances.  Many times these windows are located over interior spaces as well as exterior locations.

Now that there is an understanding about the types of windows there needs to be an understanding of the parts of the windows.

  • Interior Casing: The finished trim or holdings around the window frames. They help prevent cold air from entering as well as add a finishing touch and enhancing the overall look of the window.
  • Head: The horizontal part of the window frame.
  • Muntin: A bar / strip of wood or metal between adjacent panes of glass that create a grid or latticework appearance.
  • Sash Lock: The locking mechanism attached to a single-hung or double-hung window.
  • Upper Sash (Upper Panel): The upper part of the fixed or movable framework holding the pane of a window, this can be fixed or movable.
  • Side Jamb: The vertical parts that form the sides of a window frame.
  • Stile: Vertical members of the window frame.
  • Window Pane: A plate of glass within a window frame.
  • Lower Sash (Lower Panel): The lower part of the fixed or movable framework holding the pane of a window this cab be fixed or movable.
  • Channel: A groove around windows.
  • Exterior Sill: The external horizontal bottom part of the frame that protects from water intrusion and can be used as a decorative element.
  • Apron: The decorative raised section below the window sill.
  • Stool: The bottom horizontal shelf of the window attached to the window sill where the sash descends.  This is where plants may be placed.
  • Bottom Rail: The lowest horizontal part of the window frame that connects to its vertical parts.
  • Top Rail: The top horizontal part of the window frame.
  • Air Latch: Makes it possible to keep the window open regardless of the position you set it.
  • Aluminum Bracket: Brackets made of aluminum and part of a window bracket system that offsets the window from the wall by a few inches.
  • Glass Sealant: A silicone-based product that can take on the form of a liquid, gel or foam.  This is applied to glass surfaces as a protective coating and used to preserve its clean and dry exterior.
  • Hollow Glass: Window panes made of hollow glass.
  • Pane: A sheet of glass in a window.
  • Spacer: An insulating glass unit typically made of aluminum that’s sealed between two glass layers and keeps the glass panes apart.
  • Meeting Rail: The horizontal rail of a sash that meets the rail of the other sash when the window is closed.
  • Pulley: A simple machine with a wheel and a rope / chain used to lift heavy objects.
  • Sloped Sill: The exterior part of the window sill that is designed to be sloped downward to enable water to run off.
  • Drain Hole or Weep Hole: A short channel where fluids can flow.
  • Lift Rail: A handle used to open and close a window that goes all the way across the sash.
  • Lower Sash: The lower part of the fixed or movable framework holding the pane of a window, and it can be fixed or movable.
  • Frame: The framework that makes up the window’s perimeter and supports the entire window system.

Now that the types and parts of a window have been identified, it is time to start to discuss the failures that can happen.

The industry standards provide the inspector the opportunity to inspect a representative sample of the windows.  The superior and confident inspector will go beyond that and might not operate or exercise every window for operation the inspector should lay hands on or observe the condition of every window.

Glass can break.  A very common failure to windows is the simple break or fracture in the panes of glass.  Glass can be relatively inexpensive, but there are circumstances where the replacement of cracked glass can be costly.  Cracked glass can also be dangerous, and should be considered a safety hazard as well as functional issue with the window.

There can be deterioration to any elements of the window: the glazing bean holding the glass to the sash can fail; the paint or finish can fail; troughs or sill can decay from standing water; and rails and stiles can be damaged or cracked. 

In addition, exterior water can run down the glass and filter into the claddings or behind the claddings and this can cause the wood structure of the frame and sash to deteriorate.  This is very common on casement windows with a wooden frame and cladded exterior. Any issues with windows can cause problems for owners, including costing them more on energy.