WHAT’S WRONG WITH DUCTLESS MINI-SPLITS

The title of this article is intentionally provocative, challenging the conventional norms of the HVAC industry. No doubt you’ve experienced the widespread adoption of ductless mini-split heat pumps, which dominate both new and retrofit cooling projects.

But what might be problematic with this approach?

Our concern is not merely about the inconvenience of another remote control for the homeowner (or the risk of it being chewed by the family dog) or the aesthetic impact of a wall-mounted air handler. Rather, it echoes the sentiment in Michael Easter’s Comfort Crisis—that this is yet another modern convenience that distances us from our natural environment. For instance, homeowners may use the heat pump to cool their spaces even when the outdoor temperature is a mild 50 degrees Fahrenheit. The heat pump will operate efficiently, achieving an impressive 300% efficiency (producing 3,000 BTU/hour of heating or cooling for every 1,000 BTU/hour or roughly 300W of electricity).

We understand the appeal of these systems. They are straightforward to install, requiring no ductwork or strategic placement of air grilles. They are reliable, and most HVAC technicians are well-versed in their maintenance.

However, the limitation lies in the heat pump’s inability to utilize the cooler outdoor air to regulate indoor temperatures, relying instead on electricity. This shift from natural ventilation to mechanical solutions, though convenient, is neither energy-efficient nor environmentally friendly. As building codes become increasingly stringent and construction techniques make homes more airtight, the need for fresh air becomes crucial. Without proper HVAC systems that introduce fresh air, indoor air quality inevitably declines.

While new homes are often equipped with Energy Recovery Ventilators (ERVs) that efficiently manage both bathroom exhaust and tempered fresh air, the concern is far more significant for the vast inventory of existing buildings undergoing renovations.

As HVAC professionals and building designers, you have the ability, and dare we say the responsibility, to advocate for more sustainable HVAC solutions. Team Engineering has two church HVAC renovation projects in the pipeline, both of which are considering ductless mini-splits. In these cases, we are encouraging our clients to consider integrating economizer technology. The principle behind an economizer is simple: when the outdoor air temperature is closer to the desired indoor temperature, why not harness this natural resource? This approach can be applied to both heating and cooling, potentially achieving efficiencies in the range of 1000%.

So, the next time you upgrade your heating and cooling systems, consider the benefits of leveraging Mother Nature.

Deb Barney

Senior Mechanical Engineer