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Looking for a quick fix to increase your home’s energy efficiency? If so, the exterior door to your home can be a good point of entry in more ways than one. After all, improvements to your “building shell” — the structural skeleton of your home, which includes exterior doors — can directly impact your home’s energy costs, indoor air quality, resilience to extreme weather, resale value, and more.

But even though it may seem simple, picking the right exterior door is anything but. Forget concerns that are purely aesthetic — first, there’s jargon to decipher and rating systems to decode, and beyond that, you’ll probably have questions about designs and materials.

To make all of this easier, here’s what you need to know to purchase the right high-performing door for your home.

Doors and Home Energy Efficiency

Everyone knows that keeping exterior doors closed is a simple best practice for conserving energy at home. Less widely recognized, however, is that the design of the door and the materials used in its manufacture — regardless of whether it’s open or closed — can contribute to or detract from your home’s energy efficiency to an equally significant degree.

That’s because exterior doors can influence energy efficiency in a number of different ways. For example, they’re often sources of air leakage, even when the door is closed. Beyond that, they can also waste energy through conduction, which is the process by which heat moves through a solid material. If your doors are old, uninsulated, improperly installed, or inadequately air sealed, the odds are good that they’re doing both.

Related Post: Second Step to a High-Performing Home: Air Sealing

Finding the Right High-Performing Door

Like most home improvement projects, there’s no one-size-fits-all approach to finding the right exterior right door. A lot depends on the climate where you live, as well as the structure of your home. So what should you be looking for? And when will you know you’ve found the right fit?

Let’s start with how the energy efficiency of doors is measured. To that end, the National Fenestration Rating Council (NFRC), an independent body that tests, certifies, and labels the performance of products, has developed a door-specific rating system to help you understand the likely energy efficiency of a given door prior to purchase and installation. This rating system consists of two values: Solar Heat Gain Coefficient and U-Factor.

Here’s a quick rundown of these two key terms:

  • Solar Heat Gain Coefficient (SHGC) ranges from 0.00 to 1 and measures the extent to which a product allows sunlight to impact interior air temperatures. This can get tricky, however. If you live in New England, for example, it’s true that a door with a low-SGHC will help keep your home cool during the summer months. But it may also prevent daytime sunlight from significantly warming your home come winter.

  • U-Factor ranges from 0.00-2.00 and measures how effectively a product prevents heat from escaping an interior space. Doors with low U-Factors are better at retaining heat.

Having a baseline understanding of these two concepts will help you understand the energy-efficiency ratings that you’ll see on doors once you begin looking at possible replacements for your home. But to make things easier, here’s a simple rule of thumb to keep in mind as you explore:

  • If you live in a warm climate — one in which your primary concern is keeping the indoor air temperature cool — you should look for a door with a low SHGC.

  • If you live in a colder climate that requires heating, look for a door with a high SHGC and a low U-factor.

Door Types, Designs, and Materials

Not all doors are created equal, and the materials used in the design of your new door will impact the energy efficiency of your home. So what should you be looking for?

Before addressing that, a little bit of background first: The relative resistance to conductive heat flow of insulating materials, such as those used in doors, is measured by what is called an “R-value.” Materials with higher R-values are more effective insulators; those with lower R-values, less so. Generally speaking, the thicker the insulating material is, the higher its R-value should be.

With that in mind, here are some pointers to help you make the right decision about door materials:

  • On the basis of R-values, the best materials for doors are fiberglass or steel with foam insulation, which typically have R-values of R-5 or R-6.

  • By contrast, exterior doors made of wood or aluminum usually have R-values around R-2 and R-1 to R-2, respectively, depending on the thickness of the material.

  • If you’re in the market for glass patio doors, look for those that feature a “thermal break,” or a layer of plastic insulation between the inner and outer door frame, and note that swinging doors generally outperform sliding doors from an energy-efficiency standpoint.

Bear in mind, too, that anything with an ENERGY STAR® label is going to be a good bet; just make sure the model you select is appropriate for your climate. Finally, you should also be aware that, no matter which type of door you go with, its “weatherstripping” — the material, such as the aluminum in a door shoe, used to seal small air leaks around the door — will eventually begin to wear and need to be replaced.

Related Post: The Ins and Outs of Insulation

Storm Doors

Considering adding a storm door, or a second outer door, to your home, too? A few words of advice: The consensus among home performance experts is that there are relatively few use cases in which adding a storm door actually improves your home’s energy efficiency. In fact, installing one could even lead to problems: If your outer door receives direct sunlight during the day, for example, your storm door could trap that heat against your entry door and damage it over time. Plus, if you already have a porch or overhang protecting your entry door from the elements, a storm door doesn’t add much in the way of protection.

Next Steps

Replacing your old exterior door with a modern, energy-efficient replacement doesn’t need to be so difficult, just keep the guidance outlined above in mind as you begin to evaluate options.

In the meantime, if you’re really serious about taking your home’s energy performance to the next level, not to mention increasing its resale value, be sure to download Green Door, our free app. You can use it to Identify home performance improvements that will deliver the most bang for your buck, connect with Pearl Network Contractors, arrange for Pearl Certified installation, and more.

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