Net Zero Energy homes are the epitome of high-performance buildings.
The definition of a Net Zero Energy home is one that is designed, modelled and constructed to produce as much energy as it consumes on an annual basis. These homes achieve this standard via the balance of reducing the amount of energy needed to operate and by generating energy on site through alternative energy sources.
By meeting this standard, homeowners are awarded with significantly reduced operating costs, a quiet and more comfortable living atmosphere, health benefits of high indoor air quality, and the satisfaction of making a significant contribution to the reduction of carbon emissions.
When the home is in the design process, an energy model is used to optimize specifications to properly confirm that a home will achieve Net Zero Energy (or Near Net Zero Energy) with the most responsible use of financial and material resources.
Advanced Wall Systems
HP+ Wall System
- Developed by BASF, the HP+ Wall is engineered for strength, durability, and efficiency and is a solid option to consider when building a Net Zero Energy home.
- A combination of Neopor exterior rigid insulation, Wall-Tite spray foam, and batt insulation to provide maximum insulation levels.
- Rigid insulation is fully sealed with Masterseal NP1 caulking and flexible air barrier tapes and is placed on exterior to prevent thermal bridging through wall studs.
- Spray foam insulation is installed on the interior face of Neopor, adding thermal performance, air tightness, structural rigidity, and vapour permeance protection.
- Effective R-values can range between R-25 to R-50 depending on Neopor thickness and type of cavity insulation.
- Two walls separated to eliminate thermal bridging and provide a deep cavity for high-insulation levels which is a requirement in Net Zero Energy homes.
- Exterior wall used for structural load-bearing, separated from interior for total thickness of 12”-16”.
- Cellulose insulation is compressed into the wall cavity to deliver effective R-values from R-42 to R-56.
Insulated Concrete Form (ICF) foundations are superior to conventional methods. A stay in place expanded polystyrene concrete forming system that delivers high energy performance. With integrated air/vapour barrier and finish attachment provisions, additional framing and plastic vapour barriers are unneeded. Dimpled damp-proofing membrane is used underground to ensure basement dryness.
Depending on the results of the Net Zero Energy modelling sometimes an additional layer of interior insulation on the foundation may be required to reach the desired amount of insulation. One method is to add 4” thick layer of expanded polystyrene. A framed wall with batt insulation inside the ICF foundation is another method. These result in a foundation with a NET R-40 insulation value which contribute to the overall performance of the Net Zero Energy home.
Most of the heat loss in a building escapes through the windows. With this in mind, good windows are critical in a Net Zero Energy home. Triple pane windows with a low-e film, Argon insulating gas, and insulating spacers between panes are a good choice. In a northern climate the glazing should be optimized to encourage solar energy to flow into the home while insulating to reduce heat loss to the outdoors. High-quality frames with certified sealing systems are recommended.
Solar-electric systems use photovoltaic (PV) modules to generate electricity. The arrays can be grid-tied, meaning that the home will provide energy to the electrical grid during the day, while drawing from the electrical grid during the evenings or when the home needs more energy than can be generated.
Solar PV systems can also be connected to batteries to store excess energy. This opens up the opportunity to disconnect from the electric grid and eliminates the costs of line service charges from utility companies. Effect Home Builders office in Edmonton is disconnected from the electric grid using a PV system with battery storage.
South-facing windows allow energy from the sun to be absorbed by the thermal mass of the concrete floor. This thermal mass gathers the heat energy in the daytime, releasing it in the nighttime hours.
Expanded polystyrene (EPS) is often used under the concrete floor in the basement. EPS is also part of the Insulating Concrete Form and as a method for adding additional insulation to the interior of basement walls. EPS is non-toxic, CFC-free, mould-free, and provides a stable insulating value that will not diminish with age.
A combination of insulation materials contribute to a well insulated Net Zero Energy home. For example exterior rigid insulation, Wall-Tite spray foam, and batt insulation are used in combination to in the HP+ wall system.
Cellulose was compressed into the double stud wood framed walls and blown into the attics. Cellulose is made predominantly from post-consumer recycled paper.
Glass fibre batt insulation was used in the interior framed wall in the basement of the one of the homes. Glass fibre batts were chosen based on their high recycled content (73%) and performance characteristics.
There are various methods that can be used to heat a Net Zero Energy home.
Geothermal or Ground Source Heat Pump (GSHP) requires a higher initial investment, but with proper engineering and the right soil conditions it can run at approximately 250% efficiency leading to long-term energy savings.
Electric baseboard heating
Electric baseboard heaters require a low initial investment however they are less efficient than other heating options. This option may be considered when the building envelope is very well insulated and air tight and the demand on the heating system is lower. Electric baseboard heating is sometimes incorporated into Net Zero Energy homes with a large PV system which offsets electricity used by the heating system.
Air-source heat pump
Air source heat pump is a heating option used in Net Zero Energy homes which is designed for cold weather climates. Efficiencies range from 100%-400% depending on outdoor temperature. The Belgravia Green home in Edmonton is an example of a Net Zero Energy home heated by an air source heat pump.
High efficient Heat Recovery Ventilators (HRV) are very important in an air-tight Net Zero Energy home. These units provide fresh air by exchanging stale indoor air with fresh outdoor air. The incoming air is pre-heated by the exhausting air, recovering up to 88% of the heat. Electrical usage is low due to Electronically Commutated Motors. This allows the home to be both extremely energy efficient and a healthy environment.
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