By Michael Tobias
A zero-energy home, which produces as much energy as it consumes, is the ultimate in energy-efficient home design. Although virtually impossible for the average homeowner to achieve on their own, professional designers, architects, and engineers will help you to build a net-zero energy home, or remodel an existing house to maximize its energy efficiency.
Of course, whether you are planning to build a new home or upgrade an old one, there will be legal ramifications including a host of municipal codes and regulations that will need to be followed. While some might seem to constrain, and they may indeed restrict you in some ways, many have been designed specifically to ensure that houses are as energy efficient as possible, in terms of individual circumstances and local environmental conditions.
In reality, designers don’t always specify all the energy-related details and they sometimes neglect to incorporate strategies that will improve energy performance.
These top 10 tips, simplified for the layman, will help you recognize the steps your designer, architect, builder, and/or engineer should take when they design and build an affordable energy-efficient, or better still, zero-energy home for you and your family.
- Start with energy modeling to achieve a net-zero energy design
Whole-building energy modeling (BEM) involves the computerized simulation of buildings, including homes, to assess potential energy consumption and the life cycle costs of all items related to energy including heating, ventilation, and air-conditioning (HVAC), hot water, and lighting. It is also used to develop codes and to help to develop policy decisions, as well as assess inherent performance ratings of buildings for green certification, code compliance, and so on, and to ascertain which energy-saving features are the most cost-effective.
BEM takes place once the preliminary plans, including the floor plans, dimensions, elevations, the position of doors and windows, and so on, have been completed. The plans are then adjusted according to the modeling results to ensure that the building will reach its zero-energy goal at the lowest possible cost with renewable energy options such as wind turbines.
Architects use BEM when they design buildings that are energy efficient. In addition to minimizing operation energy costs, BEM programs can help to reduce up-front construction costs too.
Mechanical engineers use BEM when they design HVAC systems, to ensure that they meet building thermal loads. BEM is also useful for designing and testing control strategies for HVAC systems and are commonly used by those offering HVAC engineering solutions.
- Ensure there is an air-tight building envelope
The building envelope is a thermal shield that protects the interior from the outside elements. It includes all parts of the house including the walls, roof, insulation, windows, and doors, which must all be effectively sealed to improve energy efficiency. It keeps heat in, weather out, blocks drafts, and helps to ensure the materials used for construction resist decay.
There are various different air-sealing techniques and materials that can be used, the choice depending on climate, budget, and which part of the building is being worked on. Ultimately, it is vital that there is a continuous air barrier along the thermal boundary of the building. The more architecturally complex the building is the more complicated it is to ensure that the building envelope is airtight.
An experienced professional will know where the thermal boundary is. For example, typically crawlspaces and vented attics are not inside conditioned spaces.
- Incorporate super-efficient insulation for the building
In addition to tightly sealing the building envelope, insulation is another key component of successful energy efficiency and it plays a critical role in ensuring that the building envelope is zero energy. Additionally, the air barrier mentioned above, and the insulation must always be in the same plane.
Architects can choose framing strategies that increase the efficiency of building envelope insulation and help to minimize thermal bridging. Energy modeling can help designers to optimize insulation in homes and other buildings.
- Opt for renewable energy and avoid fossil fuels
Zero energy homes rely on renewable energy to cut costs and minimize greenhouse gas emissions. Currently, the most cost-effective option is solar photovoltaic (PV) panels that are connected to the electric grid.
Solar PV systems can power all the energy requirements of a home, hotel, or office building including heating and cooling, lighting, provision of hot water, and running of appliances. While a remarkably cost-effective renewable energy source, solar PV panels aren’t cheap and it is important that the needs of each building are correctly calculated for affordability.
- Control heat loss and heat gain through doors and windows and incorporate passive heating
Doors and windows can be the biggest threat to a properly insulated building, basically presenting as large holes out of which energy can leak. But they also offer surprising cost-effective opportunities for making building energy efficient.
Designers can control heat loss and gain through doors and windows simply by selecting products carefully, using double- or triple-glazing, locating them carefully, and making sure that their orientation and size are both optimized.
Passive heating is an important concept too. For example, in the northern hemisphere, it is good practice to design houses and other buildings with south-facing windows to reduce heating costs in winter. These same windows should be shaded in some way during summer to reduce cooling costs.
- Optimize the ventilation system to ensure constant clean, fresh air
A genuine zero energy home will be so airtight it will be critical for HVAC engineers to ensure that there is a continuous source of fresh air that is filtered through the system. On the upside, this will ensure that the home is more comfortable and a lot healthier than homes where this kind of attention to air quality has been ignored.
The same concept applies to large buildings, where ventilation systems should be designed to ensure that air quality is reliable and germs won’t spread through the building. Effective air filtration and purification are also paramount, especially during the current coronavirus pandemic.
- Install heating and cooling systems that meet net-zero goals
Heating and cooling systems are generally expensive and they have the potential to gobble energy, so for a house or larger building to be net-zero or even just highly energy-efficient, it is essential for these systems to be carefully designed.
Many engineers opt for air-source heat pumps without ducts. Also known as mini-split heat pumps, they don’t have the recognized shortcomings of central air-conditioning systems that rely on forced air or the much higher costs of thermal heat pumps.
- Opt for an energy-efficient hot-water system
Nobody can do without a hot-water system in their home, and, like space heating and cooling systems, they can use a lot of energy.
There are various types of water heaters including solar and heat pump water heaters. Both are considerably more energy-efficient than standard water heaters. A plumber or mechanical, electrical, and plumbing (MEP) engineer will advise which type is the best for your home or building. They will also advise on the best location for the heater.
- Choose lighting systems and components that are energy efficient
Even though designers and architects can make the most of natural lighting opportunities, every indoor environment needs artificial lighting. Currently, the most efficient light source, which is also the longest-lasting, are light-emitting diodes (LEDs).
- Use appliances and electronic devices that are highly energy efficient
A feature of zero energy homes and larger buildings are their energy-efficient shells and thermal envelopes. They incorporate high-efficiency HVAC systems and energy-efficient water-heating and lighting. Heating and cooling systems are also highly energy efficient.
Now the home or building owner needs to step up and ensure that appliances and electronic devices are also energy efficient. It really isn’t difficult!