by Ali Kriscenski


Energy used for heating and cooling makes up a significant portion of a building’s operating costs. For this reason, energy-efficient strategies can have a positive impact on a business’s bottom line. When addressing seasonal cooling demand, the best place to start is to find the right type of air conditioners to use in your facility. 


5 Types of Air Conditioners

Finding the right AC system or units for your facility depends on the building size, the conditioned space, existing HVAC ductwork, your capital investment budget and your operating budget. The different types of AC can accommodate large buildings, smaller spaces and temporary and permanent cooling requirements.



1. Central Air Conditioning

If you are looking to cool multiple rooms in a large building, a central air conditioning system is ideal. Central AC is typically configured with an exterior unit that houses a condenser and compressor. Inside the building, an air handler and series of ductwork move conditioned air throughout a building. 


Central AC can be effective for cooling demand and humidity control in large buildings. Adding central air conditioning will impact energy costs, but a centralized system with programmable or smart thermostats can help create thermal comfort while meeting energy efficiency goals.


2. Mini-Split AC 

Mini-split air conditioners are similar to central AC in that they use outdoor units to house a compressor and condenser. They differ in that mini-splits don’t require ductwork for conditioned air distribution. Instead of ductwork, mini splits connect the outdoor units to wall mounted air handlers with blowers. These units can be installed in offices, retail spaces or any other space where cooling is needed.


Rather than centralized temperature control, mini-splits are better suited to individual rooms. They offer quick cooling capacity and, unlike window or portable units, they can remain in place year round without energy loss.


3. Window Mounted Air Conditioners

Window air conditioners are ideal for cooling small rooms or buildings with small open floor plans. This type of AC is a self-contained unit that includes compressor, condenser and air handler/blower.


These units are effective and inexpensive for seasonal cooling demand. They can be easily installed in double-hung windows. Most units come with adjustable panels to accommodate any size opening to the sides of the AC unit. Window units can be removed during colder months and stored out of the elements. 


4. Portable Air Conditioners

Portable air conditioners work similarly to window mounted air conditioners except rather than sitting in a window they are freestanding and can be rolled from room to room. These units do require an exhaust, however, because the unit itself is inside — the exhaust is a small hose about the size of a dryer vent.


Portable ACs are ideal for spaces that don’t have traditional windows. These units can be used with casement windows or irregular-size windows. They can operate with a single exhaust hose or dual hose which draws fresh air in from the outdoors.


5. Programmable and Smart Air Conditioners

Planning for cooling demand throughout the different solar gain and temperature changes of day and night. Occupancy levels also vary throughout the day making spaces require more or less cooling. Programmable thermostats and smart air conditioners can help with energy savings by reducing significant swings in energy demand. Where spaces are occupied by tenants, smart units can be operated like central AC where temperature is set for the building as a whole. This reduces modifications made by tenants or occupants in each individual space.



Occupant Thermal Comfort Survey

Part of an effective energy efficiency strategy for building owners is to survey the tenants and occupants on thermal comfort. This type of survey can help identify areas within a building where occupants experience conditions outside of thermal comfort parameters. While thermal comfort varies between individuals, a survey can identify conditions that may be too cold, too hot, too drafty or too humid. This information can be used to identify HVAC adjustments or maintenance that can improve thermal comfort and energy efficiency.


Expertise for Cooling Strategies

Even if you handle most maintenance in-house, you can engage an HVAC professional to become familiar with the HVAC systems in place at your building or facility. Their expertise can help you to identify the best type of air conditioning to meet your thermal comfort and energy goals. Contact Therma’s team of heating and cooling experts to learn more.


​​Ali Kriscenski was trained in high-performance building design at Boston Architectural College. She has worked with leading architecture and construction firms in NYC and New England and served on the executive team at the Forest Stewardship Council International. She was the managing editor at Inhabitat and has worked pro bono for the Green Building Institute, ISEAL Alliance and Habitat for Humanity.



Buildings – 8 Simple Strategies to Maximize Energy Savings

Environmental Protection Agency (EPA) – Building Air Quality Guide: For Building Owners and Facility Managers

Environmental Protection Agency (EPA) – Moisture Control Guidance for Building Design, Construction and Maintenance

Facilities.Net – Strategies for Cooling Efficiency in Existing Buildings

Scientific American – Green Building Retrofits – Decreasing the demand from HVAC systems