Glass block windows aren’t fire hazards; fire-rated glass block windows can increase your home’s fire safety. Modern glass blocks are made with materials that can resist high temperatures and prevent fire spread. Most offer a 45-minute fire rating, while some increase it to two hours. Compared to the typical 20 to 90 minute rating for a double-pane window, glass block can increase your home’s safety in the event of a fire.

Glass block mortar is the best choice for glass block window units. It is specifically formulated for glass block window installation. Glass block mortar is usually a mixture of Portland cement, sand, and special chemicals. It is a white mortar that is applicable inside and outside your home. Do not use regular tile mortar because it may not have the binding strength and flexibility required for glass block windows.

You can still see vaguely into some types of glass block windows at night. Although there won’t be clear definitions, passersby may still see shapes, shadows, and movement through the glass. If you want complete privacy, consider installing diamond glass block windows rather than the typical clear or wavy glass blocks.

Glass block installation can be relatively expensive due to the range of material costs and the labor time to assemble this type of specialty window. The process proceeds slowly as the glass does not absorb moisture from mortar and silicone caulk takes longer to harden, leaving spacers to hold up the structure until the caulk or mortar begins to cure. Plus, if your current windows have structural issues or damage, you’ll need to repair them before beginning the project, increasing your bottom line.