Written by By Hayley M. Abernathy
When it comes to heating and cooling the air in a smaller-scale home, conventional central HVAC is not the only — and perhaps not the best — option. These two alternative systems may fit your plans more effectively:
The Small-Duct, High-Velocity HVAC System
How it works: Like central air, a small-duct high-velocity (SDHV) HVAC is a whole-home, forced-air system controlled by a single thermostat. Air flows through flexible tubes about 3.5 inches in diameter, much smaller than conventional supply ducts.
Conditioned air is released via discreet “outlets” that are smaller and more customizable than conventional registers. Expect about eight outlets per 1,000 square feet of living space.
The benefits: The compact size of SDHV supply tubes allows them to “snake and weave through existing cavities,” explains Ashton Gavelek, marketing director of Unico, a major SDHV manufacturer. That means there’s no need for drop ceilings or soffits – a huge benefit for retrofitting and for flexibility in new designs.
Using a distribution principle called “aspiration,” SDHV also achieves a more even temperature in a space (with max temperature variation of about two degrees Fahrenheit).
The Mini-Split HVAC System
How it works: A mini-split unit uses no ducts at all. Instead, a conduit — usually small enough to fit through a 3-inch hole — connects the system’s outdoor compressor or condenser to its indoor component. Each area you want to condition needs its own indoor unit, containing an individual fan and evaporator, which can be mounted to a wall, ceiling or floor. Though not as visually discreet as SDHV or central air, according to the U.S. Department of Energy (DOE): “Most indoor units have profiles of about 7 inches deep and usually come with sleek, high-tech-looking jackets.”
The benefits: Without ducts, a mini-split is a good option for tight spaces and retrofits. With multiple indoor units (each with its own thermostat), you can set the temperature of each room or “zone” independently.
Let’s Talk Cost-Efficiency
For retrofits, SDHV and mini-splits offer substantial savings compared to remodeling to accommodate central HVAC. On new builds, both systems can be more expensive initially.
However, look for savings later:
- According to the DOE, more than 30% of the energy used for conventional HVAC can be attributed to duct losses.
- Without ducts, mini-splits are much more energy efficient. Plus, zoning means you don’t have to spend money conditioning unused spaces.
- According to Unico's Ashton Gavelek, SDHV systems have very tight ducts, with less than 5% leakage — also much more efficient than conventional HVAC.
- The Unico SDHV system reduces humidity in small-load homes while using less energy. The effect: “In cooling mode, you can set your thermostat at a higher temperature and feel as comfortable as you would by cranking it down to a low temperature with a conventional system,” says Ashton.
