What are zero-energy buildings?

The art and science of energy efficiency is evolving as consumers look for methods and products to help reduce overall energy consumption. 

From windows and doors to dishwashers and clothes dryers, today’s environmentally-conscious household products can help reduce energy usage. Now architects, designers and builders are taking energy efficiency a step further by creating buildings that produce as much energy as they use.

Zero-energy building (ZEB), or net zero-energy building, is the designation given to buildings that have zero net energy consumption and zero carbon emissions annually. These buildings harvest energy produced on-site to meet their own energy needs. 

Traditional buildings consume about 40 percent of the total fossil energy in the United States and European Union, according to the American Council for an Energy Efficient Economy. ZEB could help dramatically reduce greenhouse-gas emissions attributed to buildings.

Energy-conscious manufacturers like Pella Windows and Doors® are providing ZEB-friendly products that help take advantage of natural energy, like solar heat gain through windows to help heat a building. 

“We’re deeply committed to environmental stewardship and therefore we provide solutions to help minimize the impact a building has on the environment,” said Terry Zeimetz, AIA, CSI, CCPR, Pella’s commercial marketing manager. “Our goal is to provide architects and builders with products that deliver the most cost-effective results in terms of energy efficiency.” 

The power of yellow … sun
ZEB is a relatively new trend in both nonresidential and residential building design. The American Institute of Architects created the 2030 Commitment to challenge its firms to develop sustainable design goals that significantly reduce the use of natural resources, non-renewable energy sources and waste production. 

Increasingly, more builders, designers and architects are working to incorporate ZEB concepts into their designs, Zeimetz said.

Build it forward
Depending on a building’s design and location, architects can help heat the building by installing windows with a high solar heat gain coefficient (SHGC) — a measure that indicates how well a window blocks heat from sunlight. SHGC is expressed as a number between 0 and 1 — the higher a window’s SHGC, the more heat it transmits. 

“We work with architects to help fine-tune our windows to fit their needs,” Zeimetz said. “If they’re using solar heat gain to help heat the building, we might recommend the use of low emissivity glass with a higher SHGC to let the heat energy from the sun into the building.”

Low emissivity (Low-E) coatings, consisting of microscopically thin layers of silver or tin oxide, are applied to glass surfaces to improve energy efficiency. Two or three layers of silver can be used to fine-tune the energy performance of the glass. Two layers of silver (Pella’s Advanced Low-E) reduce the SHGC to 0.40 while allowing Visible Light Transmission (VLT) of 70 percent. VLT is a measure of the amount of visible light transmitted through glass. Three layers of silver (Pella’s SunDefense™ Low-E) further reduce the SHGC to 0.28 while maintaining a VLT of 65 percent.

Double- and triple-pane glazing options keep rooms warmer in the winter and cooler in the summer. Based on computer simulations, double-paned glass can reduce energy costs up to 17 percent and triple-paned glass can decrease energy bills by as much as 28 percent compared to a single-pane wood window. Pella’s between-the-glass blinds or shades can further help increase overall energy savings. 

If minimizing heat gain is the goal, choose windows with a low SHGC to keep the sun’s heat out and reduce the amount of energy needed to cool the building. Solar heat gain takes into account the direction the window faces. Maximize the insulation value of north-facing windows to keep heat inside the building.  

Use VLT to help maximize the amount of light inside a building. Installing windows with high VLT helps reduce the need for electric light sources. 

“Architects and builders want flexibility with VLT,” Zeimetz said. “They might want to keep visible light out in certain areas or sides of the building, but encourage more natural light in other areas. Pella products help them achieve those goals.”

Improving your building’s energy efficiency
To help improve your building’s energy efficiency and take advantage of natural energy sources, consider these tips:

  • For southern-facing windows, close the blinds, shades or curtains during the heat of the day during warm weather to reflect the sun’s heat away from the building interior. During cold weather, keep window treatments open during the day to capture the sun’s heat, and close them at night to help keep heat inside the building.
  • For northern-facing windows, maximize the insulation value to keep heat inside the building. 
  • East- and west-facing windows are least desirable for solar heat gain, so keep window treatments closed when the sun is shining in from either of those directions.
  • Choose double- or triple-glazed windows with Low-E coatings to improve energy efficiency and reduce heating and cooling costs. 
  • Remember that regardless of the type or style of windows and doors selected, it’s essential that they are installed properly for best performance in sealing out air and moisture. Pella provides specific instructions for installing its products properly. 

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