What is the energy efficiency of a building?
The energy efficiency of a building is the extent to which the energy consumption per square metre of floor area of the building measures up to established energy consumption benchmarks for that particular type of building under defined climatic conditions.
An energy efficient building reduces maintenance and utility costs, but, in many cases, improves durability, lessens noise, increases comfort and creates a healthy and safe indoor environment. A further goal of energy efficient construction is to limit damage to the ecosystem and reduce the use of natural resources like energy, land, water, and raw materials. Reducing energy consumption is crucial because it means fewer emissions of greenhouse gases, a known cause of global warming.
Global warming refers to the modern-day rise in global temperature near the earth’s surface. The increase in temperature is due to increasing concentrations of greenhouse gases (carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases) in the atmosphere. The explanation for global warming is straightforward.
The sun’s energy falls on the earth as ultraviolet, visible (light), and infrared (heat) electromagnetic energy. The earth absorbs some of the sun’s energy as thermal energy. The earth reflects another part of the sun’s energy (infrared heat) back into the atmosphere where it either passes through the atmosphere or is reflected back to the earth’s surface. Nitrogen and oxygen, which are the dominant gases in the atmosphere, allow infrared heat to pass through the atmosphere, while the greenhouse gases absorb infrared heat and redirect it back to the earth. The more greenhouse gases, the more heat is redirected back to earth; hence the increase in global temperatures near the earth’s surface.
Why is energy efficiency in buildings important?
Governments have a responsibility to ensure that there is secure supply of energy to ensure economic growth. In many developing countries there is normally very high margin between existing power supply and electricity demand. With increasing electricity use from existing consumers and new connections, new generation needs to be brought on line to meet increasing demand. In addition, due to changing climate patterns and the increasing risk of drought, countries that are highly dependent on electricity from hydro as their main source of electricity are losing much of their generation capacity resulting in intensive power rationing. Although renewable sources of electricity such as hydro, geothermal or wind provide electricity at a much lower cost than electricity generation from petroleum, their capital outlay is large, they are complex and take much longer to implement. Petroleum-based generation is usually brought in, in the short term to meet this demand, which results in increased cost of electricity, over dependence on petroleum and subsequently vulnerability to oil price fluctuations.
By setting energy efficiency targets for buildings, governments share the burden and cost of ensuring the security of energy supply with end-users.
The need to increase generation capacity in developing countries is unavoidable.
However, governments can solve peak demand constraints by finding a balance between reducing demand and increasing supply. To increase supply, governments in developing countries often have to allocate funds to subsidize new generation capacity or subsidize the cost of petroleum-based generation – as the case may apply in your region.
Reducing demand by setting up a low interest, easy payment energy efficiency revolving fund to incentivize consumers to implement energy efficiency measures would be a more sustainable approach and repayments could be based on energy savings.
The main benefit from measures to improve energy efficiency buildings is lower energy costs but there are usually other benefits to be considered too. Energy efficiency measures are meant to reduce the amount of energy consumed while maintaining or improving the quality of services provided in the building. Among the benefits likely to arise from energy efficiency investments in buildings are:
- Reducing energy use for space heating and/or cooling and water heating;
- Reduced electricity use for lighting, office machinery and domestic type appliances;
- Lower maintenance requirements;
- Improved comfort;
- Enhanced property value.
In developing countries where electricity is intermittent and power rationing is frequent, there is a large demand for diesel or renewable energy-based backup/stand-by power generation from end-users. Reducing power and energy requirements in buildings reduces the capital outlay required and the running costs of these stand-by systems.
In industrialized countries, policy, incentives, climate change targets and corporate image drive more efficient approaches to energy use in buildings. Codes and practice on energy regulations for buildings in developed countries include obligations for energy audits, requirements for building certification with ratings based on energy efficiency, carbon reduction targets for buildings, levies on energy consumption—charged per unit consumed to discourage high consumption, incentives such as exemption from building tax for good energy efficiency ratings, access to interest free/low-interest loans and grants for undertaking energy efficiency measures in buildings and, as part of their corporate social responsibility, some companies would like to be seen as a green company that promotes energy efficiency.
How to Make Your Building More Energy Efficient?
Energy efficient measures can be integrated into new construction or retrofitted into an existing building.
Energy Efficient Techniques in Renovations and New Construction
New construction gives architects, contractors and building owners the opportunity to design and build an energy efficient building, and even a net-zero energy project. A net-zero energy building consumes less than or equal to the amount of energy that it produces on site through renewable resources. The steps for constructing a modern energy efficient structure begin with choosing a site and implementing a detailed, holistic design plan.
Design of an Energy Efficient Building
Designing and building a new house or renovating an existing house to be highly energy-efficient requires careful planning and attention to detail. A whole-house systems approach helps homeowners, architects, and builders develop successful strategies for optimizing home energy efficiency.
This approach considers the house as an energy system with interdependent parts, each of which affects the performance of the entire system. It also takes the occupants, site, and local climate into consideration.
To ensure that your new or renovated home takes full advantage of a whole-house systems approach, hire an experienced design and building team and insist that they use a whole-building systems approach from the beginning of the design process. Your designer can perform a whole-house computer simulation that compares multiple combinations of variables to arrive at the most cost-effective and energy-efficient solution.
- The design should make efficient use of water and electricity and other natural resources and energy sources.
- The design of an energy efficient building should easily allow for future retrofits without impacting the performance of the building.
- The design should take into consideration building orientation. The way a structure is situated on a site and the placement of windows, roof lines and other features is critical for efficiency.
- The design of an energy efficient building should be sustainable. A sustainable design aims to lessen depletion of critical resources like land, water, energy, and raw materials. Sustainable design of facilities and infrastructure also averts the destruction of the ecosystem.
Utilizing an energy modeling software is an effective way to estimate a building’s energy use. The model’s output can help architects, contractors, and building owners modify a building performance and cost before construction starts.
An Energy Efficient Roof
An energy efficient roof (cool roof) is designed to reflect sunlight and absorb less heat than a standard roof. Cool roofs reduce energy bills, improve indoor comfort, and may extend the service life of the roof. There are several techniques for creating a cool roof.
- Cool roof coatings have special reflective pigments or are white to reflect sunlight. A light-colored roof absorbs less than 50 percent of the solar energy, which reduces a roof’s temperature. In contrast, dark roofs absorb 90 percent of the solar energy.
- Green roofs are perfect for urban buildings with flat or shallow-pit roofs. Green roofs include anything from basic plant cover to a working garden.
- Glazing Systems (windows, skylights, vents, and glass portions of doors) of an Energy Efficient Building
- Purchase energy efficient windows appropriate for your climate zone.
- Installing storm windows can lower energy bills by up to $350 a year.
- Face major glazing areas to directions that will take advantage of the solar heat gain when the sun is low.
- For warmer climates, install overhangs or other shading devices over windows to prevent excessive heat gain during.
- Low-emissivity (low‑e) window glazing helps to control solar heat loss and gains. In fact, computer simulations indicate that advanced window glazing reduces the space cooling requirements of new homes in warm climates by more than 40 percent.
- Choose energy-efficient skylights that have established minimum ENERGY STAR® performance rating criteria by climate.
- New exterior doors typically fit and insulate better than old doors. When selecting a new door, consider buying the most energy-efficient door possible according to energy performance ratings.
- Improve an existing window’s energy efficiency with caulking and weather-stripping, and the use of thermal window treatments or coverings.
Ventilation in an Energy-Efficient Building
Proper ventilation is necessary for an energy-efficient home because air sealing techniques may trap pollutants (like formaldehyde, volatile organic compounds, and radon). Ventilation also helps control moisture, which can cause mold growth and structural damage.
An energy efficient building should include an energy recovery ventilation system. An energy recovery ventilation system provides controlled ventilation and minimizes energy loss by transferring energy from conditioned air going out to fresh incoming air.
Install localized exhaust fans above kitchen ranges and in bathrooms to create spot ventilation. Spot ventilation improves the effectiveness of natural and whole-house ventilation by removing indoor air pollution and moisture.
While natural ventilation is the least expensive and most energy-efficient way to cool buildings, it works best when combined with spot ventilation, architectural louvers, ceiling fans, and window fans. For large homes and buildings, whole buildings fans are a worthwhile investment.
Heating and Cooling Systems of an Energy Efficient Building
Cooling, heating, and water heating account for the largest energy expenses in homes and commercial buildings. Incorporating energy efficient measures into a building’s heating and cooling systems are essential to creating an energy-efficient structure.
- Choose a high energy efficient heating, ventilation and air conditioning (HVAC) system. For instance, the most efficient HVAC system is 95 percent efficient; meaning 5 percent of the energy produced is expelled. Consider replacing the HVAC every ten years.
- Proper installation of a new HVAC system is essential to an energy efficient building. Improperly installed HVAC systems can reduce a system’s efficiency by up to 30 percent.
- Ensure that the fronts of vents are clear of obstructions like furniture and paper. Blocked vents require as much as 25 percent more energy to distribute air.
- Install a programmable thermostat to manage periods of time where the heating and cooling can be turned down and up.
- Change the air filter of the HVAC system as prescribed by the equipment manufacturer. Dirty filters slow down air flow and make the system work harder to keep a building warm or cool. Also, a clean filter prevents dust and dirt from building up in the system. Dust and dirt in an HVAC can lead to expensive maintenance and early system failure.
- Maintain the HVAC annually to ensure its high efficiency, longevity, and the comfort level of the building.
High-Efficiency Water Heaters
Because heating water accounts for about 7 percent of commercial building energy use and 15 percent of home energy use, it is essential, for a high efficiency building, to consider energy efficiency when selecting a water heating system.
- A tankless water heater heats water just when needed, eliminating energy lost during the standby operation.
- Install a high-efficiency storage (tank) water heater. High-efficiency water heaters use 10 to 50 percent less energy than standard models, saving energy and money on utility bills.
- A high-efficiency heat pump water heater transfers energy from the surrounding air to water in a storage tank. High-efficiency heat pump water heaters are most effective in warm climates with long cooling seasons.
- A high-efficiency solar water heater can reduce operating costs up to 90 percent.
Renewable Energy Sources for an Energy Efficient Building
- Install grid-tied or off-grid solar photo-voltaic (PV) panels for a cost-effective form of renewable energy. Solar photo-voltaic can power all the energy needs of a building including lighting, heating and cooling systems, appliances and hot water.
- Install a small wind system either connected to the electric grid through your power provider or stand-alone (off-grid). A small wind electric system can lower electric bill by 50 to 90 percent. A variety of applications can use a small wind system, including water pumps.
- A small “hybrid” electric system combines home wind electric and home solar electric (photo-voltaic or PV) technologies. A hybrid system is best in regions where peak times for wind and solar systems occur at different periods of the day and year.
- On properties with flowing water, Micro hydro-power is a simple and consistent form of renewable energy. A micro hydro-power system requires a turbine, water wheel, and pump to transform the energy of flowing water into rotational energy, and then into electricity.
Energy Efficient Lighting
- Switch to light-emitting diode (LED) light bulbs. LED bulbs are energy-efficient, durable, and long-lasting.
- Install controls such as timers and photocells that turn lights off when not in use. Dimmers, when used to lower light levels, also save money and energy.
- Use task lighting where suitable. A task light consumes far less energy than a typical overhead lighting fixture.
Energy Efficient Appliances
- Select ENERGY STAR® refrigerators because they use 15 percent less energy than non-qualified models. Also, refrigerators with top-mounted freezers use 10 – 25 percent less energy than side-by-side or bottom-mount units.
- Select ENERGY STAR® dishwashers. ENERGY STAR® dishwasher use less water and energy than required by federal standards. Dishwashers are currently required to use 4.25 gallons of water per cycle or less.
- Select commercial convection ovens that have earned the ENERGY STAR® rating. ENERGY STAR® commercial ovens are about 20 percent more energy efficient than standard models.
- An automatic electric ignition system on a natural gas oven or range can save gas because the pilot light is not continuously burning.
- Monitor flame color of natural gas ovens or ranges. A yellow flame indicates the gas is not burning efficiently and an adjustment is needed.
- Keep ENERGY STAR® range-top burners and reflectors clean, so they will reflect the heat better and save energy.
- Select clothes washers and dryers that have earned the ENERGY STAR® rating.
Energy Efficient Electronics, Computers, and Office Equipment
Whether working in an office building or from home, utilizing energy efficient electronics, computers, and office equipment can save building owners energy and money.
- Purchase ENERGY STAR®-labeled office equipment which can save as much as half the electricity of standard office equipment.
- Use a laptop computer because laptops use much less energy than desktop computers.
- Use sleep mode and power management features on the computer.
- Unplug electronics when not in use because many electronics continue to draw a small amount of power even when switched off. These little draws on energy can occur on most appliances that use electricity: DVD players, TVs, stereos, computers, battery chargers, and kitchen appliances.
- Turn off the monitor if not using the computer for more than 20 minutes.
- Turn off both the CPU and monitor if not using the computer for more than 2 hours.
Other Ways to Make a Building More Energy Efficient
- Incorporate energy efficient landscaping into the overall building design. For instance, shady landscaping protects a building from direct sunlight during the summer and allows more sunlight to reach through windows during the winter. Additionally, planting trees on the southern and western side of a building can keep the building cooler because it blocks sunlight from falling directly on the building during the winter; then, when after the trees lose their leaves, the trees allow more sunlight to reach the building.
- Optimize system control strategies with occupancy sensors, CO2 sensors, and other air quality alarms.
- Choose window treatments or coverings not only for decoration but also for saving energy. For example, triple layer cellular shades can significantly reduce your utility bill and make the interior of a building more comfortable.
While the upfront costs of making a building energy efficient may seem high, building owners soon recoup the extra cost through reduced utility and maintenance expenses. Also, incorporating energy efficient features into a building make it more valuable.
- According to the National Climatic Data Center, before the Industrial Revolution (about the year 1800), levels of carbon dioxide were about 280 parts per million by volume (ppmv); current levels are greater than 380 ppmv and increasing at a rate of 1.9 ppm per year since 2000. The burning of fossil fuels (coal, natural gas, and oil), solid waste, trees and wood products, and certain chemical reactions (e.g., manufacture of cement) are responsible for the increase in greenhouse gases. Furthermore, because plants absorb CO2 (thus remove it from the atmosphere) as part of their biological carbon cycle, deforestation and also lead to increased CO2 levels in the atmosphere. Adverse impacts of global warming are extensive. A few of the impacts include rising sea levels due to increasing rates of glacial melting, more acidic oceans due to increasing carbon dioxide levels, and more frequent and severe weather events — like hurricanes.
- Sustainable energy regulation and policy-making for Africa
For more information and designs for energy efficient buildings, contact us.