What Are The Key Points Of A Zero-net Energy Building Envelope Design?
Basil D Soufi / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)
7 Key Elements to a Net-Zero Energy Building Envelope
A building envelope for net-zero energy (NZE) is critical for reducing the use of energy and saving money for sustainable homes and buildings. The US Department of Energy ( DOE) defines an NZE building as a system that generates enough renewable energy to fulfill its own annual energy consumption needs, thus reducing the usage of non-renewable energy in the building sector. In the NZE building envelope, the exterior walls, roof, base, and exterior doors and windows have to be taken into account.
Consideration of every element of the envelope is important when designing an NZE building envelope. Below are seven concrete ways of improving the NZE envelope.
1. THE FOUNDATION, A SOLID STARTING POINT
A building must be isolated from the ground by the base of an NZE building envelope. With a continuous layer of rigid foam insulation under a concrete slab base, an efficient way to isolate a building from the ground is. Since concrete has a high thermal mass, it retains radiant energy and keeps a building inside dry and wet, ideal for the NZE building envelope base.
2. ADVANCED FRAMING
Advanced framing (Optimum Value Engineering or OVE) is a technique designed to minimize the amount of lumber used in the construction of a wood-framed house and the amount of waste produced. By replacing timber with insulation, advanced framing also increases energy efficiency. Maximizing the space of the insulated wall decreases thermal bridging and increases the R-value of the entire wall. Examples of advanced framing methods provide spacing for the wall studs, roof rafters, and floor joists up to 24-inches on-center.
3. CONTINUOUS INSULATION
A NZE building envelope requires continuous insulation. The ASHRAE Standard 90.1-2013 describes continuous insulation as uncompressed and continuous insulation, other than fasteners and service openings, overall structural members without thermal bridges. Wrapping the envelope of a building with a continuous insulation layer increases the structure's efficient R-value, which is an integral component of an NZE building.
4. A WEATHER-RESISTANT BARRIER
Continuous insulation can decrease the ability of a wall to release humidity from within the wall assembly. Inside a wall system, high moisture can cause the growth of mold, which is unhealthy for the occupants of the house. Wood rot may also be caused by moisture.
5. UTILIZING HIGH THERMAL MASS
Choosing thermal mass materials for an NZE building envelope can help regulate temperature changes inside a building by absorbing and storing heat energy.
Steel, wood, and carpeting have low thermal mass, so NZE building envelopes are not good products. Concrete, stone, and brick have high thermal mass and are excellent options for an envelope for NZE construction.
6. THE COOL ROOF
A cool roof reduces energy bills and increases comfort indoors. Cool roofs will also make the service life of the roof longer. A cool roof is designed to reflect more sunlight than regular roofing products and retain less heat. Materials for a cool roof include materials such as tiles, clay, and slate with low thermal mass. Such products are reflective or have pigments in light colors that throw out the sunlight.
7. THE EXTERIOR DOORS AND WINDOWS
ENERGY STAR-approved windows, doors, and skylights suitable to the building's climate zone should be included in the NZE building envelope. ENERGY STAR-certified windows will lower energy bills by an average of 12 percent, according to ENERGY STAR. Lower energy consumption not only saves money but also lowers building and power plant greenhouse gas emissions.
To decrease energy use and save cash for both commercial buildings and homes, a NZE building envelope is necessary. Attaining NZE reduces the cost of service and maintenance and is safer for the climate. Net-zero energy buildings are therefore more robust than non-NZE buildings to natural catastrophes.
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