Tempered vs. Regular Glass: What You Need to Know | Ep. 1

Welcome to Stay Glassy — the show that makes windows and doors actually make sense. In Episode 1, Newman Windows and Doors pros Maria and Duncan kick things off with everything you need to know about glass: the critical difference between tempered and annealed glass, exactly where building codes require tempered glass in your home, how to tell if your existing windows have it, and what happens when tempered glass is mishandled. If you've never thought twice about the glass in your windows, this episode will change that.

Tempered vs. Annealed Glass: What Every Homeowner Needs to Know About Window Safety.

Key Takeaways from This Episode:

• Glass is not just glass — tempered and annealed (regular) glass behave completely differently when broken, with dramatically different safety implications
• Tempered glass is 10 times stronger than regular glass — but when it does break, it shatters into thousands of small, dull pieces rather than sharp shards
• Regular annealed glass breaks into razor-sharp shards that can cause severe lacerations — it is genuinely dangerous in the wrong location
• Building code requires tempered glass in all glass doors, within 2 feet of a door, within 18 inches of the floor, within 60 inches of a bathtub, shower, pool, or jacuzzi
• To check if your window has tempered glass: look in any corner of the glass for a small stamp — called a “bug” — that reads “tempered safety glass”
• Tempered glass is more brittle on its edges and corners — hitting a tempered dual-pane unit on its corner can cause the entire unit to shatter instantly
• Milgard's lifetime warranty transfers to new owners as a 10-year warranty — the original lifetime coverage applies only to the original homeowner
• Always get a warranty that covers both parts AND labor — a replacement glass unit doesn't install itself, and glazing labor is the expensive part
• If a contractor installed your windows and is no longer reachable, the sales order number stamped inside the window frame can help a manufacturer verify your purchase and warranty status

Tempered vs. Annealed Glass — Why It Matters

Most homeowners assume glass is glass. It isn't. Tempered glass and annealed glass — standard, untreated glass — look identical from a distance, but they behave completely differently when broken. Annealed glass fractures into large, irregular shards with razor-sharp edges capable of causing severe lacerations. Tempered glass, by contrast, is heated to a high temperature and then rapidly cooled, a process that leaves it approximately 10 times stronger than annealed glass — but when it does break, it shatters into thousands of small, dull fragments that are far less likely to cause serious injury. This is why your car's side windows are tempered, and why building codes require it in specific locations throughout your home.

Where Tempered Glass Is Required by Code

California building code mandates tempered glass in any location where a broken pane could cause serious injury. All glass doors — sliding patio doors, French doors, entry doors with glass — must be tempered without exception. Beyond doors, tempered glass is required in any window within 18 inches of the floor, within 2 feet of a door (measured as an arc from the door edge), and within 60 inches of a bathtub, shower, pool, or jacuzzi drain. Kitchen windows are not included in these requirements. If you're unsure whether your existing windows meet these requirements, checking is straightforward.

How to Tell If Your Windows Have Tempered Glass

Look in any corner of the glass pane for a small permanent stamp — called a “bug” in the industry — that reads “tempered safety glass,” typically including the manufacturer's name. It's small and sometimes requires getting close to the window or even getting down on the floor to find it, but it will be there on any compliant tempered unit. If you can't find a bug in a location where tempered glass is code-required, that's worth following up on with a qualified window professional.

One Important Caution About Tempered Glass

Tempered glass's strength applies to impacts across its face — not to its edges and corners. A dual-pane tempered unit placed on its corner on a hard surface will shatter completely and instantly. This is relevant during any window handling, installation, or removal. It's one of many reasons window installation requires trained professionals, not improvised DIY handling.

Does the Milgard lifetime warranty transfer to a new owner? Partially. Milgard's lifetime warranty applies to the original homeowner for as long as they own the home. When the home is sold, the warranty becomes a 10-year warranty from the original installation date. If you purchase a home where Milgard windows were installed 15 years ago, there is no remaining warranty coverage. If you're buying a home with Milgard windows, ask the seller for the original installation documentation and check the remaining warranty period.

What should a window warranty cover? At minimum, a warranty should cover both parts and labor. A warranty that covers replacement glass units but not the labor to install them leaves homeowners paying glazing contractor fees out of pocket when something fails — and that labor is typically the most expensive part of the repair. Always ask explicitly whether labor is included, for how long, and under what conditions before signing a contract.

What if my installer is no longer in business and I need warranty service? The sales order number stamped inside the window frame can help. Manufacturers can use that number to verify when the windows were purchased, who the original homeowner was, and whether warranty coverage applies. If you can demonstrate you were the original homeowner at the time of installation, you may still have coverage directly through the manufacturer — even if the installing dealer has closed.