As the reality of climate change, the link between the use of fossil fuels and global conflict, and the rising cost of fuel (in the medium term, of course) becomes increasingly clear, many people are taking a serious look at how homes and buildings can be heated and cooled in a smarter, more ecologically healthy way. Moreover, the impact of poor air quality - which was barely on the radar for most Americans a few decades ago - is rearing its ugly head in the form of increased instances of asthma, allergies, and other maladies that affect adults, and sadly more and more children. Unfortunately, how one heats their home has historically been more a matter of local custom and fuel availability (gas, oil, or propane), combined with the constraining expense of tearing out and replacing systems in existing homes. However, a wonderful alternative has now become more common in the US, and perhaps the best news is that it isn’t new at all.
What are MiniSplits?
MiniSplit heating (explanation below) has been used in Europe and Asia for almost 50 years. More technically called “ductless heat exchangers,” Minisplits have many advantages over more “invasive” heating and cooling systems (such as ducted “forced-air” systems, radiators (electrical, steam, and hydronic), radiant heat, and baseboards). Minisplits are the most efficient, widely available heating and cooling systems in the US. They are far quicker and easier to install than the alternatives. Minisplits don’t require walls and ceilings to be specifically designed for ducts, holes to be drilled in structural members for pipes, or useful wall space to be dedicated to radiators and baseboards. And, most MiniSplit systems can provide all of your heating and cooling needs in one system - basically two-for-one - adding yet another reason why MiniSplit/Ductless Heat Exchangers are the most economical option for homes and other buildings.
How do they work?
A MiniSplit system basically acts like your refrigerator, if the latter also had a reverse switch. A magical liquid (the “refrigerant”) is pumped in a closed loop (i.e. the refrigerant never touches anything, air or otherwise, but rather is enclosed in a tube with no outlets). It moves between a fan and a heat exchanger, which in the MiniSplit case is outdoors. This refrigerant liquid is very good at absorbing heat, storing it, then giving it away. In the case of cooling, it is pumped outdoors (to the exchanger) and is zapped with a little bit of electricity, causing it to give up all its heat, coming back into your home as a very cold liquid. The process is reversed for heating, where it actually steals heat from the outside (even when it is very cold outside, there is still some heat stored in the air, ripe for the picking) and brings that heat inside to warm your house. The heat (or AC) is distributed into your home by a low-velocity, very quiet fan that blows over the heated (or chilled) refrigerant liquid (which again is still in its containment pipe/tube).
Why would I want a MiniSplit system to heat/cool my home?
Well, that’s the science (or, sort of), but why does it matter? First, you’ll notice that there’s absolutely no gas, oil, or propane involved in this process (we’ll get to the “electricity” part shortly). That’s always the case with AC systems, but folding heating into this clean, hassle-free mix is awesome! Indeed, just the fact that a single system takes care of your heating and cooling is a huge benefit, as there’s only one machine to install, to maintain, and to store. Actual storage of the system in your house exposes another benefit - it isn’t stored in your house! The main appliance that makes this all work is about the size of a dishwasher and is kept outside. This is a major advantage to people without basements or people in smaller (or even Tiny!) homes. There are fan units which are kept inside the home, but these typically are installed high up on walls (often above doors and windows, space typically used for nothing else). And, because you are “stealing” heat and coolness from the outdoors, MiniSplits use very little energy, as the electricity used to zap the refrigerant liquid into taking or giving up heat is small compared to the heat that is exchanged. (There is additional electricity used to pump the refrigerant and to run the fan on the inside unit(s), but the amount is relatively small.) Maybe the most important advantage of MiniSplit systems, in particular as compared to “forced-air” heating and “central-air” cooling, is the health benefit. Ducted systems like the ones mentioned above blow air through tunnels winding their way through your walls. These tunnels are very difficult to clean, meaning that you are potentially breathing air that is being pushed through years of dust, mold, and other pathogens. Ductless systems - like MiniSplits - get rid of these tunnels and keep the dust-bunnies out of your lungs.
What’s the catch?
The biggest catch is that MiniSplit systems really aren’t optimal for very large homes and buildings. There isn’t time to go into exact numbers here, but I’d say that McMansions and larger need not apply. The reason is that with large homes, you start to need more and more interior fans, all connected with refrigerant pipes to the outside unit, so at some point you might as well have a ducted, radiant, or radiator/baseboard system. Also, most people love the fact that the heating/cooling apparatus is outside (and traditional “central air” cooling systems have this already). But, regardless of where you place it or how you hide is, some folks would prefer to keep everything in the basement, which doesn’t fly with MiniSplits. Additionally, while the interior fans are very quiet and quite inconspicuous, some people prefer the absolute silence and invisibility of, for example, radiant-style systems. Finally, this is a system that runs on electricity. Given how little electricity is used relative to the heat (or cooling) gained, this fact is typically is no problem; but if you live in an area where electricity costs are extremely high, you might want to ask a pro to run the numbers before going “ductless”.
Another word on Electricity
The unfortunate reality is that, in the US, the vast majority of electricity is produced using coal or other fossil fuels. However, this will change, and I believe very quickly. Solar, Wind, and Hydraulic power resources are quickly catching up to the burning of dinosaur goo in both cost efficiency and prevalence. And, with the increased traction of companies like SolarCity - which make it possible to lease home solar panels very inexpensively - and advancements in renewable energy storage (like the new Tesla home battery), it soon will matter less and less what the big utility companies use to make their electricity. In my opinion, standardizing all home energy needs on electricity (rather than a mix of, say, gas and electricity) is the smart bet towards a near future where electricity is gathered for nearly free from renewable resources, stored in your home and elsewhere, and oil and gas are limited to inside the frying pan and, for cooking buffs, under it as well.
MiniSplits aren’t right for everyone, but they are ideal for many homes. If you are building a modest-sized home and are looking to simplify your build and life while reducing your ecological footprint and energy bill, take a look at the options available for MiniSplit Heat Pumps. They come in with all different BTU ratings (the bigger your house and colder your winters, the more BTU’s you’ll need), as well as single and multi-zoned systems. If you have an existing house of modest size and are sick of paying your gas bill or seeing oil trucks in your driveway every few months, talk to a local HVAC installer to see whether it makes economic sense to simply “mothball” your existing furnace/boiler system and install a few mini-split zones. You can then impress your friends not only with how cheap your heating bill is, but you’ll have the most popular house in your neighborhood when the summer rolls in and your “two-for-one” AC kicks on. Just think how smart and “European” you’ll look!
Thanks for reading!
founder and president
Homebuilt | Precise Kits for Personal Buildings
Please note: While Homebuilt uses (and loves!) MiniSplit systems in its designs, we are not affiliated with any particular brand.