If you’re installing exterior doors or windows in your home, then you’re going to want to ensure that they’re high-quality, energy-efficient doors that won’t let all of your furnace-generated heat or cold A/C out of the house. Otherwise, you could end up with an astronomical power bill!

Thankfully, today’s folding door systems can be customized with energy-efficient technology that prevents them from being a drain on your heating or cooling system. In today’s post, we’re going to discuss thermal efficiency and explain the various methods that manufacturers employ to increase folding door thermal efficiency.

Get your notebooks out, because we’re about to get scientific!

What Is Thermal Efficiency?

Thermal efficiency measures how efficient a material, door, or window is at regulating temperature. Materials that have a high degree of thermal efficiency are commonly known as insulators. They keep the outside temperature out and the inside temperature in.

Conversely, materials that have a low degree of thermal efficiency do not; the outside temperature can easily get past the material and vice versa.

To simplify the concept, think of a thermos mug compared to a regular ceramic mug…

The insulated thermos mug will keep your coffee nice and hot for up to an hour, while the traditional ceramic mug will allow your coffee to get cold after 15 or 20 minutes.

Will Folding Doors Increase My Power Bill?

One of the most common questions that folding door shoppers have is, “Will folding doors increase my energy bill?”

At first glance, folding doors certainly don’t look very energy-efficient. They’re essentially large glass doors with a small doorframe, and glass (by itself) isn’t very thermally efficient. So one might expect that the doors would be a huge drain on your energy, right?

Wrong.

Thanks to advancements in glass glazing technology, thermal breaking with synthetic materials, and low-emissivity glass, today’s all-glass folding doors can be customized to be incredibly energy efficient. As long as the door panels are closed, your inside temperature will stay consistent, and very little (if any) air will escape or be able to penetrate the doors.

California’s Title 24 And Why It Matters

Before we get into too much detail on how today’s folding doors are designed to be so energy efficient, we’ll give you a bit of background story.

As you’re probably aware, California is one of the most progressive states in the country when it comes to energy efficiency and green power. So, in 1999, Title 24 was adopted in an effort to make buildings that were more energy-efficient. The result was that less power needed to be generated, resulting in fewer greenhouse gasses, less pollution, and cleaner air for California residents.

Essentially, Title 24 regulates how efficient building materials such as doors, windows, roofing systems, and more are manufactured to be. For example, all doors and windows must have a U-Value of 0.3 or lower if they’re to be installed in California.

Folding doors first became popular in California thanks to its fair weather and scenic vistas. Currently, California remains the state with the most folding doors in the country; so, almost all major folding door manufacturers design their door systems in compliance with Title 24.

What Is U-Value In Folding Doors?

You may have noticed the term “u-value” that we used above. Sometimes referred to as the u-factor, this number ranges between 0 and 1 and is a measurement of a door or window’s thermal efficiency. 0 represents a fully insulated system that is 100% thermally efficient, while 1 represents a non-insulated system that is incredibly inefficient.

Title 24 dictates that all windows and doors must have a u-value of 0.3 or lower, meaning that the standards are quite rigorous. Folding door systems with a 0.3 u-value are incredibly efficient, and release only minimal amounts of thermal energy.

How Energy-Efficient Folding Doors Are Manufactured

The u-value of a folding door is only half of the story, though. As we mentioned, glass doors by themselves aren’t very efficient at all. This is why traditional “sunrooms” have always been regarded as hot rooms of the house that might double as a greenhouse room for your plants.

However, thanks to modern manufacturing technology, today’s doors are incredibly efficient. Here’s how they’re made!

1) Thermally-Broken Doorframe

The two most common folding door frame materials are vinyl/PVC and aluminum. They’re strong, durable, lightweight, and corrosion-resistant, making them the perfect choice for a doorframe. However, neither of these materials is particularly efficient, and heat/cold can easily transfer from one side to the other.

That is unless the doors are thermally broken.

Thermal breaking is a process by which an otherwise inefficient material (such as aluminum or vinyl) is turned into a thermally efficient material. This is accomplished by lining the hollow interior of the vinyl or aluminum doorframe with a layer of synthetic polymer.

The polymer used to “break” the doors has a high resistance to thermal energy transfer and won’t allow hot or cold energy to transfer through the doorframe out of (or into) your home.

The only doorframe material that does not need to be thermally broken is hardwood. Wood is a natural insulator, so you don’t have to worry about the material’s energy efficiency.

2) Advanced Weatherstripping

In traditional doors, the edges around the door have always been the most susceptible to letting drafts of air into your home. Today’s high-quality folding door systems are manufactured with advanced weatherstripping that won’t significantly expand or contract in the cold or hot seasons. It’s also resistant to moisture and ice.
The result is weatherstripping that’s incredibly durable and won’t let any air escape your home and get outside. It also won’t let any water seep in through the multiple door panels.

3) Glass Glazing

So far, we’ve shown you how the doorframe itself is made to be energy-efficient. However, most folding door systems are over 85% glass, so the glass has to be just as efficient as the doorframe itself.

This is accomplished through several glass technologies, but the first layer of defense is glass glazing. This is the art of “stacking” sheets of glass in a window or door system. Dual-glazed glass is the most common in folding door systems and features two sheets of glass aligned in parallel. Triple-glazed glass isn’t as common, but it can provide enhanced efficiency in extreme climates.

By adding multiple layers of glass to the system, you create an extra barrier that the hot or cold air has to pass through, slowing down the thermal transfer.

4) Low-E Glass Systems

Glass glazing, by itself, isn’t enough to create energy-efficient folding doors. Low-E (low-emissivity) glass utilizes a dual or triple-glazed glass system to create a vacuum space in between the sheets of glass. This vacuum space is then injected with Argon gas.

Due to its chemical properties, Argon is naturally resistant to temperature change. So, this provides a huge layer of defense against thermal transfer and ensures that your system is as efficient as possible.

5) Protective Window Film

By combining glass glazing and low-E Argon glass technology, manufacturers can easily create a folding door with a u-value of 0.3. However, many of today’s top manufacturers prefer to go a step further, boasting folding door systems with a u-value of 0.2 or even 0.15!

This is typically accomplished by adding an additional protective layer of protective window film to the exterior pane of glass. Like the thermal break applied to aluminum and vinyl, this film is made from a transparent synthetic polymer that resists temperature change, acting as the first line of defense to the outside elements.

Those who live in regions that receive lots of sunlight may also opt to install a ceramic tint to their windows to deflect UV rays and make their folding doors even more efficient.

6) Swinging Doorway

One of the more obvious ways that manufacturers ensure their doors are energy-efficient is by adding a swinging doorway. This allows for easy entry and exiting, without having to open the entire door system and let all of your inside air out. You won’t find these on multi-slide doors, which is one of the reasons why folding doors are a bit more popular than sliding door systems.

7) Ultra-Tight Locking Mechanism

Most of today’s high-tech folding door systems feature multi-point locking systems that utilize several different locking points along the doorframe to create an ultra-secure doorway. In addition to preventing break-ins, though, these multi-point locks also increase the energy efficiency of the folding doors by holding the door panels tightly together, creating a better seal.

Can I Get A Tax Break For Energy-Efficient Doors?

Some states (especially those that are trying to enforce new green energy measures) are actually offering tax credits to homeowners who’ve installed energy-efficient doors and windows in their homes. It may not be much, but hey – who can’t use a bit of extra cash in their pockets these days?

Conclusion

Despite first appearances, modern green technology has dramatically improved folding door thermal efficiency. Almost all doors on the market are designed in accordance with California’s rigorous Title 24 to create energy-efficient doorways that won’t significantly increase your home’s power bill.

For those wondering why folding door systems are such a high-dollar home addition, we’ve also done our best to explain all of the technology that goes into creating these high-tech door panels. So, hopefully, you have a better appreciation for just how awesome exterior folding doors are!