High rise HVAC is a major concern in New York City
New York City is home to about 7000 high rise buildings, typically defined as structures with 12 or more stories. And that number is growing every day. According to the Wall Street Journal, over the past five years the city has experienced the largest construction boom in a generation.
Especially for luxury residential construction projects, high rise HVAC requirements are a prime concern. Buyers and tenants demand nothing less than consistent comfort, quiet operation, and even the ability to customize the heating and cooling of the space according to their individual requirements. Yet for builders of high rise residential buildings, those needs have been tough to meet with the traditional high rise HVAC options. They tend to be noisy, inefficient, and they take up too much valuable space within the building.
Why high rise HVAC is a challenge
Heating and cooling high rise buildings presents difficulties not encountered with structures that have fewer stories. For example, as the building increases in height, the air temperature outside the building decreases and the wind speed increases, which can impact the ambient temperatures inside as well as operation of outdoor equipment. Skyscrapers above 60 stories high have the most difficulty with this issue. Also remember that heat rises, so heating and cooling requirements for the upper floors can be quite different than the lower floors. The high rise HVAC system must be capable of accommodating the varying conditions throughout the building.
Tall buildings also use a great deal of energy simply because of their size. When you consider that as much as 30 percent or more of a building’s energy usage is consumed by the air conditioning system, it’s no wonder that developers want the most efficient high rise HVAC systems they can find. That’s one area where the traditional choices for high rise HVAC have fallen short.
Another problem is space. In New York City, where space is such a valuable commodity, no one wants to waste it on space to house high rise HVAC systems. Developers want to minimize plant areas and maximize salable living space, and residents don’t want to give up high ceilings or closets to heating and air conditioning ductwork or equipment.
Traditional high rise HVAC options are losing favor with builders
In New York City as well as other large cities, the traditional options for high rise HVAC systems are beginning to lose ground. As demand for cooling in particular has increased, due to climate change, increase in power consumption and expectations of residents, the disadvantages of older high rise HVAC technology have become more problematic.
These were the high rise HVAC system of choice for older construction (at the time) and are still used today especially in landmark buildings, due to restrictions in new holes through the wall. These individual units are installed through an existing wall opening and can only serve one or two rooms. Especially for luxury spaces, these units just can’t measure up to the comfort requirements of today’s homeowner. They are also very noisy and an eyesore in well-appointed spaces.
Individual split systems
As opposed to a large, central building system, this option consists of individual units for each living space. These small, air-cooled units are installed with condensing units mounted under windows and on balconies of each apartment, and indoor fan coil units somewhere within each living space. They are inexpensive to install, but the problem can be finding the space for the indoor units without giving up closet space or lowering ceilings heights to make room for ductwork. They are also noisy, inefficient and don’t work well for higher floors.
Four-pipe water systems
This high rise HVAC option consists of a central piped water system with air-cooled chillers for air conditioning and boilers for heat, which supply indoor fan coil units inside each living space. While they can be energy efficient, the four-pipe system is extremely expensive to install and it can be problematic to measure (and bill residents for) individual energy consumption.
Central water-cooled systems
These have been the high rise HVAC systems of choice in the city’s largest buildings, consisting of central cooling towers and boilers that serve water-sourced heat pump units in each apartment. One of the biggest downsides of chilled water systems is the presence of water pipes running though the wall, which can cause expensive damage in the event of a water leak. The heat pumps can also be excessively noisy and have the same space issues as split systems. Perhaps the most troubling are the potential problems with cooling towers that plagued New York City a few years ago: the possibility of legionella contamination and the need for regular disinfection and chemical treatment.
Related article: HVAC Cooling Tower Maintenance Checklist
VRF systems: the high rise HVAC system of choice
As an alternative to the problematic older high rise HVAC choices, builders and developers are looking to a newer technology called Variable Refrigerant Flow, or VRF systems.
VRF has been the high rise HVAC system of choice in Japan and Europe for many years. Yet VRF systems have only been introduced in the US within the past decade or so, and have been quickly gaining popularity due to the efficiencies of the system and the superior comfort levels they can provide.
The VRF system is consists of a large condensing unit the feeds numerous smaller air handlers throughout the space. It’s air-cooled, which eliminates both the danger of water leaks and the need for chemical treatments to prevent the growth of bacteria. Here are some of the reasons why more builders are choosing the VRF system for high rise residential construction projects.
Advantages of VRF systems for high rise buildings
CUSTOM COMFORT: The system is capable of varying the amount of refrigerant being piped to individual air handlers (hence the name), which gives VRF technology an unequalled ability to provide customized heating and cooling via multiple zones within a space. This customization also helps with the issues of varying demand between upper and lower floors.
ENERGY EFFICIENCY: The technology used by the VRF system minimizes energy consumption. The system is also designed to reuse heat given off in the condensing process to provide heat in other areas of the space, so it can be used for supplemental heating.
QUIET OPERATION: The use of smaller air handlers, and lack of ducts for many installations, means quiet for the homeowner.
LESS SPACE REQUIREMENTS: Those smaller air handlers also translate to less indoor space required to house the units.
MORE DEPENDABLE: Since the compressor runs at a lower capacity in a VRF system, there is less wear and tear, which results in fewer breakdowns.
Related article: Residential Air Conditioning: What is a VRF System?
Sounds like an ideal solution for high rise HVAC, doesn’t it?
What else to know about choosing VRF systems for high rise buildings
However, there is one caveat to keep in mind when considering a VRF system: they require considerable training and expertise to install and maintain. Be sure to choose an HVAC installation and service provider that has proven experience with VRF systems, because if the installer does it wrong, you’ll have poor performance and face the expense of hiring someone else to fix it.
With all the available options for HVAC systems, it can be tough to choose the right high rise HVAC technology for your project, especially given the unique challenges of New York City. Here’s a resource that simplifies the task: The Ultimate Guide to Air Conditioning for NYC Luxury Residential Spaces. Get your free copy with the all the information you need to make the right choice for the project.