HVAC—the acronym for heating, ventilating and air conditioning also refers to the integrated system within a multifamily building that regulates temperature, humidity, air flow and indoor air quality. As the Green evolution in building and development has progressed, HVAC systems, designs and technologies have received considerable attention, primarily as to how a building’s energy-efficiency portfolio is affected but also in relation to indoor air quality.

Randolph Gerner, AIA, principal with New York City-based GKV Architects, says the application of different multifamily HVAC systems and designs should be based on the geographical climate. “What makes sense in New York will not make sense in California,” says Gerner. “In New York City, HVAC systems need to account for cold winters and hot and humid summers, whereas in the Southern regions of the U.S., and especially the Southeast, cooling is the primary strategy because the heating requirements are so minimal. However, differences in HVAC strategies can be profound over relatively short distances. For example, despite the proximity, Washington, D.C., has a completely different heating philosophy as compared to New York.”

According to Gerner, while direct HVAC heating systems are more practical for cold temperate environments, heat pump systems, which can both heat and cool, are preferred for moderate regions. “In moderate climates, there is enough outside ambient heat that can be converted via a heat pump to the interior of a multifamily building,” says Gerner.

In rental multifamily buildings located in New York City, Gerner says package terminal air conditioner (PTAC) systems are very popular because of economic and functional considerations. “PTACs are affordable and more appropriate for rental communities because they are flexible, more forgiving, and can be upgraded very easily. They are turned on or off just like a light switch, and can cool very effectively in hot environments,” he says.  

Another HVAC system that, although not widespread in use, offers advantages over other systems is a fan coil installation. Consisting of a centralized plant that delivers hot or cold water to a fan coil unit located in an interior space, these systems function by drawing air into a unit, circulating the air over a water coil to heat or cool it, and then expelling the air back into the room. As compared to HVAC systems that utilize ducts, fan coil installations require only piping, which takes up less space and makes them generally easier to install. “Fan coil systems are occasionally used in high-end condominium buildings and are very sophisticated and can be adjusted infinitely,” says Gerner. “They can also accommodate cooling needs very efficiently from room to room.”  

For higher-end and smaller multifamily communities, Gerner says split HVAC systems, which are primarily used in Asia, could become more prevalent in the States. These systems include an outdoor compressor that is usually placed on a rooftop or a ledge. A 1- to 2-inch pipe connected to the compressor transfers cold gas to a small air-handling unit in the interior, which can hang from a wall and even be disguised architecturally. “Although they can be complicated to install and condensation needs to be continually managed, split systems are highly flexible and can heat or cool very quietly,” Gerner adds.

These systems are also becoming more efficient. “With newer split systems, one single compressor can now interconnect with multiple air handling units,” says Gerner. “This increases the overall efficiency of the system.”

HVAC for Hot and Humid

In hot and humid climates, such as the South, HVAC design and engineering is primarily focused on strategies to keep buildings cool. A considerable amount of energy can be expended each year running air conditioning systems in these regions. This is especially the case in the summer months.

While incorporating high-efficiency HVAC systems is an important consideration for maintaining comfortable indoor air temperatures as well as adequate air flow in hot climates, the design and placement of these systems can arguably be equally if not more significant. This is the philosophy behind the cooling and air-circulation strategies of Houston-based Shade House Development.

“For cooling buildings in hot and humid regions, builders and developers should take into account a structure’s attic space,” says Matt Ford, co-founder of Shade House. “Attics can get as hot as 150 degrees in the summer. This is where most of the heat pressure in a structure will occur.”

As part of the design for a five-unit condominium development located in Houston’s historic Heights neighborhood, Ford created an innovation called Sun-Flow, a ventilating system that circulates air through the attic space. Fans and vents, powered by rooftop solar panels, work to maintain a flow of air though duct channels, drawing fresh air in from outside the roof and expelling hot air out. “Sun-Flow is specifically designed to keep air moving through the attic in order to achieve ambient temperature,” Ford says. “This helps prevent heat from building up and eventually seeping into the living space.”

Another HVAC design strategy that Ford implemented with this project involved the specific placement of each unit’s air conditioning system. “In many areas, including Houston, air conditioning units are traditionally installed in the attic spaces of homes and buildings,” Ford says. “But this is like placing an ice maker up there—it doesn’t make any sense. Even the most insulated air conditioning ducts can take up heat loads fairly easily and are susceptible to leakage. Having them run through the attic is not a wise strategy.”

Instead, Ford integrated high-efficiency air-conditioning systems within the living space of each unit. “We took out a centrally located closet in each unit and placed an air conditioning system and sealed furnace in that space with ducts that branch out to each part of the home. This increases the operational efficiency of the system, and if duct leaking occurs it is not wasted since the leaking is occurring within the home space,” Ford says.

The Case for Advanced HVAC Technology

In contrast to conventional HVAC systems, which generally require less upfront capital, advanced HVAC systems and technologies can be more expensive, but because they are also more efficient, the operating costs over the life of the project will most likely be considerably less. Determining what type of system to incorporate depends in large part on financial analysis and whether or not the numbers work in your favor, says Terry Egnor of Portland, Ore.-based MicroGrid, a company that offers engineering management for high-performance buildings.  

“Another important consideration is energy costs,” Egnor says. “High-efficiency systems inevitably use less energy. This means less exposure to energy volatility. In terms of risk management, this is a fantastic financial hedge.”

Acting as project manager, Egnor oversaw the installation of an advanced HVAC system for a mixed-use development located in Beaverton, Ore. The Round at Beaverton Central, which was built around a light-rail urban transit system and includes condominiums, restaurants, retail stores, a hotel and office buildings, incorporates an ultra-efficient HVAC technology called the Hartman Loop.  

According to Tom Hartman, founder of Georgetown, Texas-based the Hartman Company and creator of the Hartman Loop, his network-based HVAC technology is engineered for variable speed, high-efficiency heating and cooling. “Most conventional systems are designed around peak load requirements,” Hartman says. “However, most of the time during a given day, peak heating and cooling is not reached. This is why it is more important

to design systems for part-load capacity. By doing so, the system’s overall efficiency is maximized.”

The Hartman Loop, based on a new control technology called the Equal Marginal Performance Principle, is able to self-optimize for any demand needed, says Egnor. “Instead of lunging from one level to the next, the system components will adjust ever so slightly while using the least amount of energy needed to fully meet demand,” he says. “Each component is in its optimum position for every load all the time.”

Taking into account the overall life of a project, Egnor says developers who incorporate advanced HVAC systems designed for highest possible efficiency will ultimately come out ahead. “The life-cycle costing is in your favor ,and your risk exposure to energy costs is substantially reduced,” he says.