The Basics of Window Energy Ratings

Window Energy Ratings1

Things feeling a little drafty in your neck of the woods? If you notice yourself shivering every time you walk through your home, it may be time to think about buying a new set of windows. But a lot has changed for windows in the past decade or so. Specifically, the products on the market now have gotten a lot more efficient, thanks to material and design improvements that help reduce drafts and keeping heating and cooling inside your home, where it belongs.

However, unlike a washer and dryer, where the end game for efficiency is pretty much the same across households, buying the right energy-efficient window depends a lot on the climate in your area. For instance, if you live in the North, you might want your windows to allow in more passive solar heat than you would if your home was in a warmer part of the country. And getting the recipe just right for your region can seriously affect your home’s energy consumption.

Window Energy Ratings2

NFRC Ratings and ENERGY STAR Certifications

To help homeowners make sense of how different windows behave in various climate conditions, the National Fenestration Ratings Council created a system for gauging their performance. The NFRC runs a voluntary program which tests different products for both their heat loss and gain, as well as the amount of visible sunlight windows allow into your home. After a product has been tested, a label displaying the ratings can be applied to the window’s packaging and product brochures.

These ratings are used to determine whether or not a window can be labeled as ENERGY STAR certified, meaning that it meets the EPA’s minimum criteria for energy efficiency. This certification is a sure sign that a window will be more efficient than one that doesn’t bear the ENERGY STAR label—however, if you want the maximum energy efficiency, you may need to dig a little bit deeper. A minimum requirement is just that—the minimum. So you may find that slightly higher or lower ratings are needed to keep your home comfortable and to truly save money on your energy bills. To help you pick out the best window for your area, let’s take a look at each individual rating and what it means.

Window Energy Ratings3

U-factor Ratings and Climate

A window’s U-factor indicates how much heat escapes through a window once it’s installed. Most windows rate somewhere between 0.15 and 1.20 for U-factor, although the lower the U-factor, the better the window is at preventing heat loss. That doesn’t necessarily mean the lowest U-factor you can find is the best, however. In hotter climates, a slightly higher rating may actually be ideal, since it will keep your home from overheating throughout the winter. For instance, the minimum U-factor requirement needed to achieve ENERGY STAR certification is 0.27 or lower in the country’s northernmost reaches, whereas it’s only 0.40 or less in the south. To view the minimum U-factor requirements for each region, check out the EPA’s program requirements.

When shopping for windows, make sure the U-factor has been determined by the NFRC, however, since the ratings council tests the whole window—including the frame and insulation—for overall performance, rather than basing its rating on just how the glass performs. A window’s frame is one of its weak points, so a product that hasn’t been tested for leaks in this area may not perform as well.

Window Energy Ratings5

Solar Heat Gain Coefficients and Extreme Temperatures

On the other side of the equation, there’s a window’s solar heat gain coefficient, or SHGC. This measure indicates how well a window’s glazing shades a home’s interior, preventing heat gain from solar radiation. You’ll want to pay particularly close attention to your window’s SHGC if you live in a warmer climate, since reducing excess heat in your home can make your AC work more effectively. A rating below 0.25 will serve you well in these areas—the lower the SHGC, the better the window is at shading your home.

However, northern homeowners who find themselves saddled with high heating expenses may also find their window’s SHGC a useful measurement. Higher heat gain coefficients can be used as a passive heating technique to lower HVAC energy consumption in the winter. To do so, it’s important to balance the SHGC with the appropriate U-factor rating to achieve a beneficial equivalent energy performance. These comparisons can also be found in the North Climate Zone table in the ENERGY STAR program requirements.

Window Energy Ratings6

Air Leakage Also Plays a Role in Energy Efficiency

While a window’s U-factor rating gives an indication of how much heated or cooled air escapes through the window, there’s also a separate measurement for how much outside air a product allows into a home. This is the Air Leakage, or AL, rating. The lower a window’s AL rating, the less air it allows inside. In order to be labeled as an ENERGY STAR window, it should measure no higher than 0.30 cubic feet per minute.

Window Energy Ratings7

Visual Transmittance Helps with Lighting Expenses

The previous measurements express how a window affects your home’s heating and cooling efficiency. But that’s not the only benefit energy-efficient windows can provide. Windows with a high Visual Transmittance (VT) rating also allow more visible daylight to filter into your home, which can be used in the daytime to offset lighting costs. Lighting a home typically makes up about 10 percent of a home’s total energy expenses, so a little relief there is helpful. To help homeowners understand the relationship between a window’s VT and SHGC ratings, the NFRC also created the Light-to-Solar-Gain rating, or LSG, which indicates how effectively a window allows daylight into your home while still shading the interior from solar heat gain. If you’re hoping to use VT to reduce your lighting expenses, it’s a good idea to look for products that display an LSG rating as well—the higher the number, the more light you’ll get without excess heat.

If you’re smart about your energy ratings, you can effectively use your windows to reduce energy costs in your home. When you see the rate of return on your energy bills, the time you invested reading and understanding window measurements will seem well worth it.

Author Bio
Erin Vaughan is a blogger, gardener and aspiring homeowner.  She currently resides in Austin, TX where she writes full time for
Modernize.com, with the goal of empowering homeowners with the expert guidance and educational tools they need to take on big home projects with confidence.

By |September 10th, 2016|Energy Efficiency, Green Building|0 Comments

Smarter and Greener: The Future of Building

Print The face of construction is changing fast as innovative technologies introduce smarter and greener building methods and materials to help the industry’s future meet consumer demands to save energy and the environment.

 


Inspiration from the way termites build their mounds has engineers at Harvard researching swarm robotics, which are thought to be the way forward. This pioneering technology uses robots which can multi-task rather than just being programmed to carry out one duty. This means should a robot malfunction another can immediately take its place to get the building completed on time.

3D printed houses are another area where designers are looking to change the face of construction. This type of housing is already in existence in China and have been tested by the WinSun company, while DUS architects in the Netherlands are also experimenting using 3D printed buildings. Coupled with swarm robots, 3D printed houses could potentially be built virtually anywhere, including other planets or the moon.

Construction materials are also under constant research and development. Some of the latest innovations include Aerogel Insulation, an ultra-strong, lightweight, see-through aluminium that has super-insulating properties and Microalgae which has the ability to produce renewable energy and provide shade.

The infographic offers an insight into these new building materials and construction methodologies. It also takes a look at some buildings that are leading in the way in smarter and greener construction, including the Crystal in London and The Edge Building in Amsterdam.

With smart buildings breaking the mould from design and conception, the materials being used to the way they are built, they are showing us how to be more eco-friendly and potentially increase productivity without having detrimental effects on the world around us.

Using renewable energy sources, having their own recycling abilities and using data collection to make working spaces more efficient, smart buildings are becoming a reality on a global level.

Infographic courtesy of RubberBond.co.uk.

Cleaner and Smater Green Technology

By |September 8th, 2016|Green Building|0 Comments

Couple Build a Fun Tiny Home

ext

Samantha and Robert, a couple hailing from Yakima, Washington, recently built their first home together. They both enjoy an adventurous lifestyle, from backpacking through Europe and South America, to road tripping across the US, so moving into a tiny home will be just another adventure for them. Samantha is a nurse, and Robert is an architectural designer. They both work full time, and it took them about 14 months to complete the home in their free time. (more…)

By |September 1st, 2016|Green Building|0 Comments

Spend Your Vacation in a Tiny House Village

village

Ever wish you could rent out a tiny home so you could see how living in one actually feels like? Well now you can. The Tumbleweed Tiny House Company are currently building a new tiny house vacation village near Portland, Oregon, and the houses there will soon be available to rent.The village will consist of five homes and it will be located inside the Mt. Hood RV Park. This means that guests will also be able to use the park’s amenities, namely the swimming pool and spa, game room, as well as the hiking and biking trails. (more…)

By |August 19th, 2016|Green Building|1 Comment

Rent a Box in Someone’s Home

podext

Rents in cities across the US are going up like crazy, and San Francisco is no exception. Illustrator Peter Berkowitz wanted to rent an apartment or room there, but could not find one to fit his budget. Instead of moving to the suburbs, he came up with an ingenious solution to cut rent and live in the city. With the help of a few friends he built the so-called Living Pod, which is basically a box that can be installed in a larger apartment, and offer the inhabitants privacy. The rent he’s paying now is $400, and the pod cost only $1300 to build. It was inspired by the Japanese Capsule Hotels. (more…)

By |August 8th, 2016|Green Building|2 Comments

Beach House Clad in Cork

ext

Cork is an often overlooked insulating material, even though it is a great choice for the job, since it’s completely renewable. In the renovation of this 1920s beach house in Essex, UK they used it for cladding and it’s a great choice. The beach house itself is a great example of modern architecture and renovation done right. The renovation was completed by UK-based architect Lisa Shell. (more…)

By |August 4th, 2016|Green Building|0 Comments