The Roadmap to 80×50 is one of the most ambitious GHG-reducing initiatives undertaken in the United States.
The greenhouse gas reduction target is daunting due to New York City’s density, tremendous energy demand, aging infrastructure and space constraints. Greening the city’s electrical grid and shifting from fossil fuels to cleaner electricity was one of the biggest GHG reduction measures identified in this report. Specifically, electrifying building heating systems in order to reduce the consumption of oil and natural gas in multifamily and residential buildings was said to be crucial in meeting the city’s reduction targets.
In July 2018, representatives from leading HVAC manufacturing companies—Carrier, Fujitsu and Ice Air—gathered at Project Farmhouse to discuss the impact of widespread electrification, advancements in heating technologies, and the challenges of working in NYC.
Products that will get the job done
All three manufacturers were optimistic about the 80×50 goal and the opportunities it presents in terms of energy efficiency and product development. The products most suited to tackle the electrification challenge were ductless mini-splitsMini-split systems are heat pumps with two main components: an outdoor condenser and an indoor unit. They require only a small hole through a wall for conduit that links the units and carries power, … Continue reading, variable refrigerant flow (VRF) unitsVRF systems are another type of heat pump configuration. These systems can vary the flow rate of refrigerant to different spaces and can use a single outdoor unit to serve multiple indoor units. A … Continue reading and potentially high-efficiency packaged terminal units (PTAC’s)PTAC stands for “packaged terminal air conditioner.” PTACs are single, self-contained heating and air-conditioning units installed through a wall. A PTAC system requires large vents … Continue reading.
Nick Conklin (Carrier) and Brendan Casey (Fujitsu) spoke about their VRFs and ductless mini splits, which have been extensively used in the Asian residential and nonresidential market for the past 30 years but crossed over to the Western market in the last five to10 years. These units are able to provide heating and cooling with a much higher efficiency than current systems—especially inverter-based heat pumps, which allow operation at different speeds and provide only as much cooling or heating as needed.
Many existing units have leaky enclosures; Mo Siegel (Ice Air) estimates that replacing them with new PTAC units could slash energy costs due to higher efficiencies and sealed enclosures. However, most new PTACs will not fit into existing sleeves, meaning installation would require opening up building facades—driving up a project’s budget. Understanding this need, Ice Air has developed packaged heat pumps that fit into existing sleeves, but their performance in cold weather needs to be measured and compared to the performance of other heat pumps.
Challenges in the NYC market
Many retrofit projects require work to be done throughout the entire building, all at once. This can be a challenge, as entry to tenant units is notoriously difficult. However, VRF systems can be installed floor by floor or tenant by tenant, meaning that building owners can retrofit each unit based on tenant turnover.
Ice Air also touched upon a design challenge in dense apartment buildings: there may not be an adequate area for heat extraction and condensate disposal, which could affect heating and cooling performance. No solution to this problem exists yet, since moving more heat usually requires opening up the façade (a problem that requires additional cost and permits). Condensate disposal requires additional piping and drains to get rid of the water which might not be available.
Meanwhile, it’s crucial for systems in New York to have extreme cold weather heating efficiency: this is becoming less of an issue for heat pumps, as more and more new models are designed to meet extreme conditions. (The new inverter-driven heat pumps that can provide a heating COP as high as 4.5 and operate well below freezing.)
Finally, because these systems use refrigerants, there are concerns about safety, leaks and refrigerant piping. The manufacturers said that while refrigerants can leak over time, it happens very slowly, and building safety standards and properly functioning leak detection devices prevent them reaching unsafe levels. Properly training installers and commissioning systems correctly provide additional safeguards.
Electrification will improve efficiency, but not by itself
Retrofitting existing multifamily buildings would be an excellent opportunity for individual tenants and owners to reduce energy costs, as well as for the city to meet its target. Ductless mini splits and VRF units are versatile HVAC systems, suitable for many residential applications. They are easy to implement in new construction buildings and require only electrical infrastructure—as opposed to traditional natural gas, steam or hot water piping. But an easily scalable approach to retrofitting existing buildings with these systems has not emerged.
Overall energy efficiency is achieved by more than just replacing equipment. It requires a holistic approach that involves improving existing building systems (such as envelopes), training installers and periodic maintenance. And, on a larger scale, while electrified systems will help improve efficiency, and therefore help NYC achieve 80×50, it’s just one piece of the puzzle.
Published August 22, 2022
|↑1||Mini-split systems are heat pumps with two main components: an outdoor condenser and an indoor unit. They require only a small hole through a wall for conduit that links the units and carries power, refrigerant (the cooling and heating fluid) and condensate. These are most commonly found in residential buildings, especially single family homes.|
|↑2||VRF systems are another type of heat pump configuration. These systems can vary the flow rate of refrigerant to different spaces and can use a single outdoor unit to serve multiple indoor units. A VRF system has the advantage of being able to simultaneously heat and cool a space. These are mostly found in commercial applications.|
|↑3||PTAC stands for “packaged terminal air conditioner.” PTACs are single, self-contained heating and air-conditioning units installed through a wall. A PTAC system requires large vents to cool its condensing coils, and these are usually cut into the façade introducing infiltration problems. These are commonly found in residential and hotel applications.|