Today, many vinyl windows offer some version of a lifetime warranty. But not all those warranties are created equal, experts warn. And contractors who don’t know what a warranty really says can be left holding the bag if customers have problems.

“Warranties are not guarantees,” said Jeff Lowinski Window and Door Manufacturers Association’s tactical services vice president. “A warranty can be great or useless depending on what it says.”

That’s true even in the case of lifetime warranties, because there are no laws governing them, Lowinski says. Some states have tried to set minimum guidelines, but those are hardly a safeguard. For example, California only requires a minimum of three years to meet the lifetime warranty threshold.

To make matters more confusing, some manufacturers’ lifetime warranties cover only parts, not labor, and the definition of “lifetime” can vary from the life of the consumer to the expected life of the product. “You’ve got to read the fine print,” said John Gorman president of Save Energy Company, a residential window and door installer.

For contractors, knowing the subtleties of the fine print in lifetime warranties is not only smart business, but also crucial to helping customers find the right product. “If you don’t understand the terms of the warranty, how can you correctly and appropriately recommend a product to a homeowner?” Lowinski asks. “It’s no different than if you didn’t understand the product itself.”

Savvy contractors say fully understanding warranties is key to closing deals. “First and foremost, warranties are a great selling tool,” Gorman said. “It’s just a sense of security for the homeowner. ‘I’ve got a lifetime warranty. And if anything goes wrong, I’m covered.’ It just takes that issue off the plate.”

Gorman and others say lifetime window warranties aren’t just good for customers. The right warranty saves contractors a lot of hassle, lost time and money. But once again, even seasoned contractors can become confused by terms such as prorating and the true definition of “lifetime.”

Here are six points to consider when examining a lifetime warranty:

1. Tempered glass. Today, many windows come with tempered, or toughened glass, sometimes called safety glass. But tempered glass can also be temperamental, which can result in sudden explosion or breakage, Gorman says. Because of this, tempered glass is often not covered in a lifetime warranty, he warns. So if you’re installing a tempered glass product, check the fine print on the warranty.

2. Labor. If a warranty doesn’t cover labor, contractors have to handle repairs themselves. When only parts are covered, contractors must still do the labor. “That’s taking money out of my pocket. It’s huge to have warranties that cover labor so we don’t have to spend time going back and fixing something that’s not our issue,” said Phil Isaacs, president of California Energy Consultant Services. He added that customers don’t really distinguish between manufacturers or contractors — they just expect the problem to be fixed one way or another.

3. Response time. Even if a warranty legitimately covers labor, parts and materials, it’s still not a sure thing. Gorman says some companies underestimate the amount of warranty issues they’ll have to cover and become backlogged so badly they’re essentially not covering the warranty. Because the customer’s relationship is with the contractor, “it reflects poorly on you,” he warned. So when you’re investigating warranties, don’t be afraid to ask the company about typical response times. A reputable company will have an answer.

4. Company longevity. It can be tempting to work with an upstart company that offers an attractive price point. But longtime installers like Isaacs warn that if it seems too good to be true, it probably is. That’s especially applicable to lifetime warranties, which are only good if they company stays in business. “There are a lot of risks with lifetime warranties in general,” Isaacs said. “And if you go with a company that’s really on the low end, they’re warranty is probably not going to be very solid.”

5. Transference. Some of the most established companies don’t just offer lifetime warranties, they also offer transferrable warranties. Sometimes, this comes in the form of a “double” lifetime warranty, which means the current homeowner can transfer the lifetime warranty to the next homeowners. Other warranties offer a prorated lifetime warranty should the client sell the home within the life of the warranty. “We use the double lifetime warranty in our sales presentations,” Isaacs said. “The more sophisticated buyers see that as a nice option to pass on to a potential buyer.”

6. Glass breakage. This is one of the newer offerings manufacturers are including with lifetime warranties. And Isaacs says it’s got real “sizzle factor” with his clients. Glass breakage coverage does exactly what it says: If the glass accidentally gets broken, the warranty covers replacing that glass. “Someone saved $600 to $800 from the glass breakage warranty and they didn’t have to deal with a glass company they didn’t know,” Isaacs said. “People like that.”