As building and construction industries worldwide continue to push for sustainability, net zero energy (ZNE) buildings are emerging as an alternative solution. These structures generate as much energy as they consume, resulting in reduced carbon footprint and cost savings for the owners.
In order to minimize energy consumption, ZNE buildings utilize a combination of energy-efficient systems and renewable energy sources. Among these, exceptional insulation and air-sealing is vital.
Passive Design Strategies
Passive design strategies use the natural environment to provide heating, cooling, ventilation and lighting to a building. These techniques are not as complex as the active systems that rely on mechanical devices, but instead utilize the principles of energy conservation and site location. These strategies take advantage of the local climate, utilizing windows for daylighting and cross-ventilation and materials with low embodied energy to reduce heating and cooling loads.
Insulation is a key component in these passive designs, as it helps prevent the transfer of heat between areas of the house. It is especially effective when installed as continuous insulation, as this significantly reduces thermal bridging. Insulation also works well in conjunction with other passive elements of the home, such as sloping roofs and eaves to reduce direct solar gain, and building mass and shape that enhance natural ventilation, cooling, and daylighting.
Other techniques used in net-zero energy buildings include water conservation fixtures and heat recovery units for waste water, high efficiency electric equipment (including light bulbs and appliances), skylights and solar tubes for daytime illumination without adding unwanted heat and reducing electricity usage, and exterior landscaping to provide seasonal shading. Miscellaneous electrical loads are reduced by eliminating unnecessary plug loads and specifying Energy Star appliances to minimize phantom power use.
Geothermal Energy Systems
Geothermal energy systems use pipes to transfer heat from the ground to radiators and other climate control equipment in homes and buildings. They also work in reverse during the summer to provide cooling. Geothermal energy systems can reduce the need for photovoltaic panels, making net-zero buildings more cost-effective.
The earth’s surface has a relatively constant temperature. This allows geothermal systems to convey energy from the ground to homes and buildings at the same temperature year-round, eliminating the need for mechanical heating and cooling.
In addition, the underground mass of rock, sand, and other soils act as a thermal battery that can store heat energy for long periods of time. Geothermal systems are able to capture the heat of summer and carry it through winter, producing more energy than they consume.
Another benefit of geothermal systems is that they produce power 24 hours a day, unlike solar and wind power generation, which are intermittent resources. These systems can help make net zero energy buildings viable for commercial applications, which could lead to a more efficient economy that reduces the need for fossil fuels.
While there are still many challenges to achieving a net-zero energy building, the advances in green construction techniques and technologies have made it possible for a new class of buildings that produce as much energy onsite as they consume on an annual basis. This will reduce carbon emissions and create a more sustainable future for all.
Energy Management Systems
The energy used in net-zero energy buildings is offset by the generation of renewable, zero-emission energy on the site. A building is considered a net zero energy building when its electricity use is equal to or less than its annual production of on-site solar and/or wind power. This is possible through innovative construction techniques, advanced design strategies and efficient occupant behavior.
In addition to highly insulating building envelopes, net-zero energy buildings are designed with high efficiency heating and cooling equipment (such as heat pumps that are four times more efficient than furnaces), radiant floor heating and cooling, daylighting with skylights and solar tubes, low emissivity windows and high energy performance lighting. Other energy-saving features include a waste water heat recovery system and rainwater collection systems for potable water. Appliances and miscellaneous electric loads are also optimized by minimizing phantom load or standby power consumption.
The cost of these new construction designs and technologies has been decreasing and the initial investment can be paid off by government and utility incentives and financing programs that have become increasingly available. For example, in some states, homeowners can receive rebates and tax credits for installing a geothermal system or other passive design improvements. As these incentives continue to grow and materials costs decrease, it is expected that the affordability of deep energy retrofits will improve allowing more buildings to reach a zero-energy status.
Insulation
Insulation prevents heat from moving between areas that have different temperatures. It keeps your home warm in winter and cool in summer, significantly cutting energy costs and increasing comfort. It’s easy to install and is a great way to add value to your home.
Most insulation is made from fibres that trap tiny pockets of air, which gives them high thermal resistance. It comes in many forms, including bulk batts, fiberglass blankets, cellulose insulation and polyurethane foam. It can also be blown into place, sprayed or poured in. It can be installed in new-build homes or added to existing walls and roofs.
In addition to saving energy, cellulose insulation offers other benefits: it is non-flammable and fire retardant, resists rodent and vermin infiltration, mould and mildew, and provides protection against the effects of condensation. It is also treated with borate, which makes it resistant to termites and other insects.
Foam boards are rigid panels that can be used in a variety of applications, from sheathing for wall frames to attic hatches. They can reduce heat conduction through structural elements and have a higher R-value than most other insulating materials of the same thickness. Foam boards can be supplied with an anti-condensation backing, but this needs to be carefully assessed for each climate zone. Foil-faced boards and foil-backed blankets should have the foil facing inwards if used in cooler climates, to avoid adding to the condensation risk.