Building Energy Audit (ASHRAE Level 2)
Saving Electricity with a Professional Energy Audit
Electricity is often regarded as a cleaner form of energy than natural gas and heating oil. However, this is only true for clean technologies like solar panels and wind turbines, not for coal and gas-fired generation. There are two main ways to reduce building emissions resulting from electricity consumption:
- Reducing your electricity consumption directly with measures like LED lighting, NEMA Premium motors, and air conditioning upgrades.
- Consuming less electricity from the grid and generating your own, using renewable energy sources like wind and solar power.
- In both cases, the electricity consumption measured by your building’s power meter is reduced. Your indirect emissions are also reduced, since the building uses less electricity from conventional power plants.
Local Law 97 of 2019 provides emission factors for multiple energy sources, and this includes electricity from the NYC grid: 0.000288962 metric tons of CO2 equivalent per kilowatt-hour. In other words, a building produces 289 grams of indirect emissions for each kilowatt-hour consumed from the grid.
With a professional energy audit, you can identify the building upgrades that will save the most kilowatt-hours during their service life. As a quick example, let’s assume you get an energy audit, and the consultants identify potential upgrades that can save 500,000 kWh per year:
- If your electricity price is 20 cents/kWh, this project saves you $100,000 per year. Even greater savings will be achieved if your electricity provider increases its tariffs.
- Based on the LL97 emission factor, your building is also reducing its carbon footprint by 144.48 metric tons of CO2-equivalent per year.
- Consider that LL97 of 2019 penalizes buildings with $268 per metric ton above their annual emission limit. In this case, the building owner also saves almost $39,000 per year in avoided penalties.
As mentioned above, a building energy retrofit can be an expensive project with a long payback period. However, NY Engineers can help you qualify for financial incentives that reduce your out-of-pocket costs, shortening the project payback period while increasing its return on investment.
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Saving Natural Gas with a Professional Energy Audit
Many buildings rely on natural gas for space and water heating, and this represents a major energy expense in places with cold winters. However, there are several factors that increase the heating cost of buildings, and many of them remain undetected until you get an energy audit:
- Low insulation and air leaks can drastically increase your energy bills, since the building is constantly losing heat to the outdoor environment. Your heating equipment must work harder to compensate for this loss and keep an adequate indoor temperature.
- Old heating equipment also tends to be inefficient, especially when it lacks proper maintenance. In this case, energy consultants will often recommend an equipment upgrade.
- There are many buildings that suffer from both issues, and their heating costs are extremely high as a result. In these cases, a deep energy retrofit can sometimes achieve savings of over 50%.
Building envelope upgrades not only save on space heating during the winter months, but also on air conditioning during summer. An efficient envelope reduces heat flow in both directions, which means the building can keep more heat inside during winter, while minimizing heat gain during summer.
With only a visual inspection, you can’t determine the insulation level of walls, roofs and floors. You can have two wall sections that look identical, and their insulation levels could be very different. However, consulting engineers can use thermal imaging cameras to visualize heat movement through your building envelope, and they can pinpoint areas that lack insulation.
- Before upgrading your air conditioning or heating equipment, you must make sure the building envelope has adequate insulation and airtightness
- Otherwise, you will continue to waste energy even after installing energy efficient equipment. You could upgrade to an ENERGY STAR boiler, and you will still have high gas bills if your building is constantly losing heat.
Local Law 97 also provides emission factors for natural gas and other fossil fuels that are commonly used in NYC buildings. The following tables summarizes these factors, and also the emissions avoided for every 100,000 BTU saved:
|
Type of Fuel |
Emission Factor |
Emissions Avoided per 100 kBTU |
|
Natural gas |
0.00005311 tCO2eq / kBTU |
5.311 kg |
|
#2 fuel oil |
0.00007421 tCO2eq / kBTU |
7.421 kg |
|
#4 fuel oil |
0.00007529 tCO2eq / kBTU |
7.529 kg |
In this example, we’re comparing the three fuel types based on the same amount of energy (100,000 BTU). However, note how the emissions of natural gas are 28.4% less than those of #2 fuel oil, and 29.5% less than those of #4 fuel oil.
When upgrading from oil to gas heating, you can also use the opportunity to install a more efficient boiler or furnace. This reduces both your heating costs and your emissions, while helping you avoid penalties under Local Law 97.
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An energy audit can propose building upgrades that will lower your energy consumption, and this reduces your bills and emissions. However, depending on the conditions found in your building, you may also get recommendations that focus on switching to cleaner energy sources. The following are some examples:
- Upgrading from heating oil to natural gas
- Upgrading from combustion-based heating to fully electric heat pumps
- Replacing electricity from the grid with onsite generation, using renewable energy systems like solar panels and wind turbines
An energy source conversion can often reduce your operating costs, building emissions, or both. In the case of NYC, you save on both energy bills and LL97 emission penalties. For example, if you install solar panels on a commercial building, each kilowatt-hour generated by them subtracts 289g of CO2-equivalent from your annual emissions
Electric heat pumps have a major potential to cut building emissions, since they can match the operating costs of gas heating without the associated emissions. By combining heat pumps with clean generation, it’s possible to heat building interiors and water with zero emissions. Geothermal heat pumps have a high upfront cost, but they can achieve low-cost heating and cooling while using only electricity.
Energy Modeling: An Important Step of a Professional Energy Audit
Many energy efficiency measures are implemented with only a basic analysis: their savings are estimated with simple “rules of thumb”, or based on typical percentage savings advertised by equipment vendors. This approach is useful as a starting point, since it provides a rough estimate of the energy savings you can expect. However, a more accurate analysis is strongly recommended before a major investment decision.
- As mentioned above, the costs of a deep energy retrofit can be high in a large building, and you will want to ensure that the benefits exceed the costs.
- A simplified analysis may overestimate your savings, which means your actual ROI is less than the estimated value, and your payback period becomes longer than expected.
- Consulting engineers can use energy modeling software to simulate your building before and after the upgrades, and this provides much greater accuracy.
Energy efficiency upgrades are often analyzed independently from each other, but this approach does not consider how different measures interact. Some energy efficiency measures achieve synergy, which means the combined savings are higher than the sum of individual savings. However, there are also cases where specific measures interfere with each other. This type of behavior can only be analyzed accurately with energy modeling.
You may have access to financial incentives that cover the cost of an energy upgrade, and in this case your net costs are minimal or even zero. However, these incentive programs tend to have stringent requirements, and you must prove that the measures planned for your building will actually work. An energy audit can help you qualify for these incentive programs, since you can submit a report prepared by professional consultants.
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