Space heating represents the largest energy consumption in New York City buildings. Furthermore, domestic hot water and space cooling systems use less energy than space heating, but they are also among the top five building systems that use the most energy. As a result, a building can drastically reduce its energy consumption by replacing its existing heating and cooling systems with modern, high-efficiency equipment.
However, before proceeding with a large-scale building modernization it is necessary to define a starting point. After all, building improvements are investments where the owner spends capital with the goal of achieving a permanent reduction in the cost of ownership of the building. In other words, building system upgrades only make financial sense if the long-term benefit outweighs the associated initial expenses.
Will there be a major renovation in the future?
Heating and cooling upgrades provide long-term benefits but can harm the building's function. If a major renovation is planned in the short term, it represents an excellent opportunity to improve HVAC performance as well.
A major renovation also offers an excellent opportunity to improve the building envelope. Poor insulation and air leaks can be detected and corrected, reducing the heating and cooling capacity required after renovation. In this way, new heating and cooling systems can be specified not only with greater efficiency, but also with lower capacity.
- For example, if you replace a 100-ton air-cooled chiller that consumes 1.2 kW/ton with a more efficient water-cooled unit that uses just 0.6 kW/ton, you will achieve 50% energy savings.
- However, if the new unit has a required capacity of just 80 tons, thanks to improvements to the building envelope, the energy savings increase to 60%.
An improvement to the building envelope can be complemented by an upgrade to the lighting system. Solid-state LED lighting emits significantly less heat than older incandescent, halogen or fluorescent lighting. All of this heat is subtracted from the space's cooling loads, providing additional energy savings beyond those achieved directly by upgrading the lighting.
Consider that a 60-watt incandescent bulb can usually be replaced with a 10-watt LED bulb, and a 4-lamp T12 fluorescent fixture (4x 34W) can usually be replaced with an integral LED fixture consuming 40-45W. The heat reduction from lighting is not significant for a single luminaire, but it can save several tons of cooling capacity in a building with hundreds of inefficient luminaires.
Building upgrades: cost and benefit
When updating a building in New York, it can be tempting to prioritize space heating systems since they consume the most energy. However, it is also important to consider the energy source used by each appliance.
For a given amount of energy delivered, electricity is much more expensive than gas in New York. Con Edison's natural gas is priced at about $1.05 per thermoelectric for residential users, which translates to approximately 3.6 cents per kWh of heat, before considering appliance efficiency. On the other hand, electricity prices typically exceed 20 cents per kWh. Even though most combustion appliances are less efficient than electrical appliances, the price of electricity is too high compared to gas. This effect is evident in electric resistance heaters, which are about four times more expensive to operate than gas heaters in New York.
Homeowners can get the best results by getting a professional energy audit before deciding which building improvements to make. With an energy audit, homeowners can get a detailed analysis of energy efficiency measures, along with the expected cost of each. Most importantly, an energy audit helps determine the return on investment for each energy efficiency measure – how many dollars will it return over its lifetime for every dollar spent upfront? Given the price difference between electricity and gas in New York, upgrades targeting the electrical system generally offer a shorter payback period and higher ROI.
Before proceeding with any building upgrades, we highly recommend checking out the Con Edison incentive program. Many energy efficiency measures are eligible for attractive cash rebates, which further improves your financial performance. Consider that some rebate programs only apply during certain times of the year or have limited funding, so building upgrades should be planned accordingly.
Importance of the type of building
Not all buildings consume energy in the same way. For example, mechanical ventilation typically accounts for about 13% of energy consumption in office buildings, but only 1% in multifamily residential environments. This is a consequence of requirements established by New York building codes for each type of property – natural ventilation design is mandatory in residential construction, but designers can choose between natural and mechanical ventilation for office buildings. Domestic hot water systems experience the opposite effect to ventilation systems, accounting for just 2% of energy consumption in office buildings but 19% in multi-family residential buildings.
Differences like this are present in many construction systems. For example, office occupancy is typically higher than residential occupancy during the day, which extends the lighting and cooling hours of office buildings, as well as the corresponding energy expenses. However, this does not mean that lighting and cooling upgrades should be discarded in the residential sector: these systems represent a small percentage of energy consumption, but they are typically older than those found in office buildings, which can result in a attractive financial return.
Final Recommendations
When deciding which cooling and heating upgrades to prioritize, it is very important to select an appropriate time frame for the project and obtain an energy audit to determine the cost and benefit of each measure. Ideally, deep retrofits should be scheduled alongside major renovations to minimize disruptions and costs. It's also important to find synergy between upgrades, for example when the space's lighting and cooling are updated. Of course, financial return is also a very important consideration: as an owner, you will want to prioritize measures that maximize the return on every dollar invested.
In general, energy efficiency measures targeting electrical systems will have better financial performance than those targeting gas-fired systems. However, there are exceptions; A building energy audit is the best way to find out.
