Making Mini-Splits Disappear
A lot of homeowners and folks in the building industry in the United States don’t want to see their HVAC (a.k.a. heating and air) systems exposed, even if it means high performance, healthy living environment, and total control. There is a magical (OK, maybe that’s a bit of a stretch) way to have cake and eat it, too.
I design, specify and recommend mini-split heat pump systems because they are the quietest, most energy efficient, and most effective systems available for mechanically heating and cooling a home (or any building). Yes, they are generally more efficient and effective than residential ground source heat pump systems (a.k.a. geothermal), and they definitely cost less to install. I can prove it, but not now.
Most homeowners who say “no” to mini-splits are only familiar with the ductless fan coils (mini air handlers) that mount on the wall just above eye-level, in the ceiling above, or on the floor next to wall. They say, “Those things are too ugly, Chris!” By saying “no”, they give up the performance, low operation cost, location flexibility, indoor air quality, zoning capabilities, and controls of the mini-split technology. All of which are superior to conventional equipment. This is not to say that ductless is the superior option. In fact, when all factors are weighed, including initial costs and effectiveness, ductless (or duct-free) is NOT the be all to end all, despite what the industry and manufacturers try to tell you.
Here are a couple photos of a design, by students from Stanford University Architecture, for a Solar Decathalon project, showing a creative way to “hide” ductless mini-split air handler. While it will technically work, it’s performance is cut short by the millwork that is hiding it.
Homeowner: “If you could make them disappear, Chris, then I would consider them.”
Hiding the wall-mounted units behind a dropped soffit or in a wall recess behind a decorative wood grille has been tried many times before, and it doesn’t work. OK, well it does “work”, but it may or may not be as effective as it could and provide the occupants the maximum comfort and efficiency. They require clearance all around them to effectively circulate the air in the room they are in.
The magic is in the selection and design process. Instead of ductless, I specify the ducted fan coils that fit nicely in to a dropped ceiling cavity, crawlspace or attic (encapsulate these spaces, please), or just suspended from the ceiling in the mechanical room. They’re no more than 10″ tall, 48″ wide, and 32″ deep, depending on manufacturer. Conventional ductwork is used to deliver the air, and what the homeowner sees inside the home is no different than what they’re used to.
Some argue that the ductwork essentially wipes out the performance benefits of mini-split equipment, and I say, “Trust the duct design!” A properly designed and installed duct system will perform well if it follows industry standards and best practices. I use the a Manual D, a protocol from a ACCA, and design ductwork as long as 30′ that are tested after install and show that they meet the required air flow.
Every home we design and build, we integrate the HVAC design with the architecture, interior and structural designs early on to make sure the systems both physically fit and are sized appropriately to meet the heating and cooling demands. The Proud Green Home at Serenbe and the High Performance Bungalow are perfect examples; we decided on ducted mini-split heat pump system even before we started sketching the floor plan. On the main level, we designed dropped ceilings in closets, and we’ll run the ductwork through pre-engineered wood “I”-Joists above. For the second floor, we put the fan coil and ERV (Enthalpy / Energy Recovery Ventilator) in the encapsulated attic, which means all equipment and ductwork will be above the ceiling joists and below insulated roof rafters. In other words, within the building enclosure of the home.
This system is made by LG‘s HVAC division. I chose their Multi-V line to get more flexibility (more available static pressure) with the duct design. Plus, we can specify equipment with enough heating capacity to avoid using expensive resistance back up heat. Here is the indoor fan coil (above – 10″h x 18″d x 35″w) and the outdoor unit (below – 54″h x 37″w x 13″d). Both are quiet. The outdoor unit will never get louder than whispered conversation (35-45 db). The indoor units are even quieter (25-35 db).
Here’s a short video me describing the benefits of ducted mini-split heat pump system:
Mini-split heat pump systems with concealed ducted air handlers offers a LOT of flexibility in the design or renovation of a home, when it comes to the heating and cooling systems. There are also many creative ways to conceal return air pathways (grilles), and use supply diffusers that are less of an eye sore, and more effective than conventional diffusers. In other words, you can have your cake and eat it, too. We can make the heating and air conditioning systems “disappear”.
Thanks for stopping by. Hope this is a useful post, and look forward to having you visit in the future.