For sustainable homes and buildings1, a net-zero energy (NZE) building envelope is key to reducing energy use and saving money. The U.S. Department of Energy (DOE) defines an NZE building as a structure that makes enough renewable energy to meet its own annual energy consumption requirements, thereby reducing the use of non-renewable energy in the building sector. The NZE building’s envelope must consider the exterior walls, roof, foundation, and exterior doors and windows.
Consideration of every element of the envelope is essential when designing an NZE building envelope. Below are seven specific ways to improve an NZE envelope.
The foundation of an NZE building envelope must separate the building from the ground. An effective way to separate a building from the ground is with a continuous layer of rigid foam insulation under a concrete slab foundation. Because concrete has high thermal mass, it holds radiant energy and keeps a building dry and warm inside, perfect for the foundation of an NZE building envelope.
Advanced framing (Optimum Value Engineering or OVE) is a technique designed to reduce the amount of lumber used and waste generated in the building of a wood-framed house. Advanced framing also improves energy efficiency by replacing timber with insulation. Maximizing the insulated wall space reduces thermal bridging and improve the whole-wall R-value. Examples of advanced framing techniques include spacing up to 24-inches on-center for the wall studs, roof rafters and floor joists.
Continuous insulation is essential for an NZE building envelope. The ASHRAE Standard 90.1-2013 defines continuous insulation as insulation that is uncompressed and continuous across all structural members without thermal bridges other than fasteners and service openings. Wrapping a building’s envelope with a layer of continuous insulation improves the effective R-value of the structure, and is an essential element of an NZE building.
Continuous insulation can lessen a wall’s capacity to release moisture from inside the wall assembly. High moisture within a wall system can cause the growth of mold, which is unhealthy to the occupants of the house. Moisture can also cause wood rot.
Therefore, the NZE building envelope must include a vapor permeable air- and moisture-resistant barrier, like the Barricade® Building Wrap. Barricade® Building Wrap is a high-quality weather-resistant barrier that meets and surpasses the requirements of the IBC 1402.2 and IRC R703.1.1. It is air- and moisture resistant, permeable, UV-resistant, has high tear strength, and is also easy to install.
|House Wrap||Perm Rating (ASTM E-96A)|
|Barricade Wrap||11 US Perms|
|Barricade Wrap Plus||16 US Perms|
|R-Wrap®||50 US Perms|
Choosing thermal mass materials for an NZE building envelope can help stabilize temperature shifts within a building by absorbing and storing heat energy.
Steel, wood, and carpeting have low thermal mass, so are not good products for an NZE building envelope. Concrete, stone, and brick have high thermal mass and are good choices for an NZE building envelope.
A cool roof lessens energy bills and improves indoor comfort. Cool roofs can also lengthen the roof’s service life. A cool roof is designed to reflect more sunlight and absorb less heat than standard roofing products. Materials for a cool roof include low thermal mass materials like tiles, clay, and, slate. These products are reflective or have light colored pigments that cast back the sunlight.
An NZE building envelope should include ENERGY STAR certified windows, doors, and skylights appropriate to the building’s climate zone. According to ENERGY STAR, ENERGY STAR certified windows can lower energy bills by an average of 12 percent. Lower energy usage not only saves money but lessens greenhouse gas emissions from buildings and power plants.
An NZE building envelope is essential to reducing energy use and saving money for both commercial buildings and homes. Achieving NZE lowers operating and maintenance costs and is better for the environment. Net-zero energy buildings are also more resilient to natural disasters than non-NZE buildings. Please visit Barricade® Building Wrap for more information on ways to improve a net-zero energy building envelope.
*1 Sustainable homes and buildings aim to reduce depletion of critical resources like water, land, raw materials and energy. Sustainable design also minimizes destruction of the ecosystem.