Commercial HVAC systems are responsible for your business’s energy efficiency, office comfort, and a significant proportion of your utility bills.
If you’re planning to develop a multifamily building, you need to select the type of HVAC system you’ll install before the project commences. In essence, an ideal HVAC system for multifamily buildings should be energy-efficient and meet the needs of multiple families occupying the building.
Unfortunately, choosing an HVAC system for multifamily building is one of the biggest challenges most property owners and developers encounter. More importantly, this decision will have both long-term implications and short-term effects in terms of installation and procurement costs.
Don’t worry though! In this guide, we’ll show you some of the things you should consider when looking for an ideal HVAC system for your multifamily building in California!
Typical HVAC systems
Installing mechanical systems offer various benefits like delivering appropriate ventilation, ensuring optimum efficiency, and providing better. Unfortunately, that is not why most developers install them in their multi-family facilities. Instead, most developers choose MEP systems depending on their upfront cost. This is why you’ll find most HVAC systems in multifamily buildings are usually single-stage traditional split heat pumps and air conditioning units.
Although these single-stage convectional MEP systems work, they don’t always properly achieve important HVAC system goals. For that to happen, the HVAC system must be properly sized to ensure that it’s neither too large nor too small for the space. If it’s too large, it will not maintain the ideal humidity (latent load), and if it’s too small, it will not maintain comfort (sensible load). The issue of low humidity levels usually occurs in smaller-sized condos and apartments since most conventional HVAC systems on the market are larger than 18,000 BTUs.
Building performance programs that specify HVAC design for Multifamily Building
Energy efficiency is one of the major factors that affect building performance, However, many building performance factors stipulate HVAC design criteria for multifamily buildings. Some of these programs include; lower air changes, tighter building envelopes, mechanical efficiency, and higher efficiency HVAC systems.
Sealing building envelopes is very effective at saving energy and reducing cooling loads, usually by reducing the run cycles of the air conditioner during the cooling season. In most cases, latent loads aren’t adequately addressed due to more efficient sensible cooling. Once that occurs, the occupants have one of two options. First, the occupant might choose a more comfortable temperature setting, leading to moisture buildup. Alternatively, they might choose to ‘overcool’ the space to meet the moisture removal requirements.
An oversized air conditioning unit isn’t an issue from the perspective of cooling or sensible loads. Oversized ACs cool the apartment quickly and cycle off once they reach the thermostat setpoint.
However, oversizing an air conditioner will negatively affect its latent capacity/ dehumidifying ability. This is precisely the case that happens in most senior living apartments. Naturally, our bodies become more sensitive to cold as we age. When combined with smaller apartments and limited incomes, using an oversized AC and mechanical ventilation drawing in humid air leads to a mold storm instead of an ideal HVAC system.
Moving on, more efficient HVAC systems with a higher SEER (Seasonal Energy Efficiency Ratio) are commonly used in performance programs. Most green building programs require higher SEER systems to meet their building program requirements. Some kinds of higher SEER HVAC systems tend to work against moisture control in MEP systems for multifamily buildings. The certification of HVAC SEER ratings is usually done by the AHRI (Air Conditioning & Refrigeration Institute).
You can match a smaller condensing unit with a larger evaporator coil or air handler to get a higher SEER rating. This usually appears on mechanical schedules of apartments as a 1.5-ton condenser matched to a 2-ton air handling unit. A larger evaporator coil helps the air conditioning unit reach the desired thermostat setpoint faster, leading to less run time. At the same time, it will hold more water than a smaller evaporator coil since less moisture will be removed. In addition, systems that use a fan cause the air handling unit to continue to run after the conder has cycled off, increasing the unit’s SEER rating by up to 0.5.
A common approach when creating an HVAC system design for handling part-load humidity is to match a multi-stage condenser with a variable air handling unit. An HVAC system, with a variable-speed air handling unit and a 2-stage compressor, can drop down at the 1st stage at about ⅔ of its total capacity when there are lower cooling loads. In addition, these systems will need a thermostat with an inbuilt humidistat to measure RH (Relative Humidity). That way, the control will reduce the air handler’s fan speed when it recognizes increased RH to make the evaporator coil colder and remove more moisture. However, this strategy of overcooling to dehumidify can lead to comfort issues, especially when used in small apartments and condos.
To sum up, a conventional mechanical split HVAC system will only work in multifamily buildings if it’s properly sized and used as intended.
Overall, the primary consideration of an ideal HVAC system for multifamily buildings should promote health, comfort, and efficiency. Luckily, HVAC experts at InnoDez Design & Engineering will help you create an MEP design for multifamily building projects in California without sacrificing any of these factors. Moreover, creating an ideal HVAC system design in the early phases of the construction process helps to optimize the building’s performance for its lifetime.