Hydronic vs Forced-Air vs Mini-Split Systems

What is the best residential heating system? Good question. There are three common types: hydronic systems, force-air systems, and ductless mini-splits. Each has their own set of pros and cons. We’ve installed all three, so we’re prepared to give you the most unbiased opinion out there. Let’s dive in.

Hydronic Systems

A hydronic system uses boiler circulating pumps to pump hot water through your floors, radiators, or baseboards to heat your home.

Pros

  • Operating cost. Your monthly utility bill with a hydronic system is going to be C-H-E-A-P compared to the other systems. Why? Because transferring heat through fluid is extremely efficient: roughly thirty percent more efficient than other systems.
  • Uniform heat distribution. This is one of our favorites. In a radiant in-floor system, you’re transferring the heat uniformly throughout the full thermal mass. Translation: it’s real comfortable. If you’re on one side of the room, it’ll be the same temperature as the other side of the room. No cold pockets. Just consistent warmth all the way around.
  • Cozy heat. When you’re getting out of a shower on a cold winter day, you’ll be glad you have radiant in-floor heating. Stepping onto a heated floor rather than chilly tile? There’s no beating that.
  • Quiet. Hydronic systems are practically noiseless. So quiet, in fact, that you’ll need to check the thermostat to make sure the heating system is on.

Cons

  • High initial investment. Boiler systems and the distribution piping are not cheap. A residential and entry-level size can be a $12,000 investment for just the mechanical room piping, plus $7,000 for distribution.
  • High maintenance. Like any advanced heating system, there are more moving parts. This means maintenance will play a bigger part in operating a hydronic system.
  • Dry heat. When you live in dry environments like ours in Montana, it can be nice to add moisture to your heating system. Unfortunately, boiler systems don’t provide that opportunity. You will be forced to supplement the system with room humidifiers or another alternative.
  • Air gets stale. During long winters, the air in your home can get stale. You will have to open a window to get air moving around the house — not an exciting prospect in below-zero temperatures.

Forced-Air Systems

A forced-air system uses a furnace to heat the air and circulate it through ductwork, using the warm air as the medium to transfer heat.

Pros

  • Low initial investment. Forced-air systems are the most economical (at least upfront) of the three systems covered in this article. The initial investment can be $7,000 for the furnace and piping, and maybe another $4,000 for the ductwork in your house.
  • Can filter air. This system give you the best opportunity to increase indoor air quality, by filtering air through electronic or pleated filters. However, if those filters go untreated, the indoor air quality plummets — which can be a con.
  • Can do in-line humidification. Unlike with hydronic systems, you can add humidity to forced-air systems without the need for external solutions.

Cons

  • Noisy. This is a big one. We can’t sugar-coat this one: forced-air systems are loud. If the furnace is located near a well-trafficked room, prepare for considerable noise coming out the registers.
  • Uneven heat distribution. Forced-air systems generate a highly uneven heat. Near the registers, the temperature may be as hot as 110 degrees; near the windows the air may be as chilly as 60 degrees.
  • Bad for allergens. As we mentioned above, if you ignore maintenance on your filters, it can make indoor quality much worse — and be a nightmare for your allergies.

Mini-Split Systems

A ductless mini-split system — also known as a mini-split — is a compact, split-system air conditioner or heat pump. Since these aren’t as common as hydronic or forced-air systems, we’ll explain this one further. Like a forced-air system, a mini-split uses an inside unit and an outdoor unit. The main difference is how the energy is transferred: in forced-air, the medium is air; in a ductless mini-split, the medium is refrigeration lines. Although they have been used in Europe for years, mini-splits are relatively new to the United States. In states like Montana, however, this system is becoming quite popular.

Pros

  • Ideal for retro-fits and remodels. Mini-splits are perfect for something like a bonus room above a garage — a room that gets way too hot in the summer, way too cold in the winter, but is too small to run any ductwork or piping. This solution can be as cheap as $4,000 for a single-zone unit.
  • Efficient. Like hydronic systems, mini-splits use an efficient medium for transferring heat. In this case, refrigeration lines, which are much more efficient than air.

Cons

  • High initial investment. Like hydronic systems, mini-splits can be about thirty percent more expensive than a traditional forced-air system, if used as a whole-house solution.
  • Heat load calculations must be perfect. If the calculations for your mini-split system are not made exactly, it will cost you. Your units will short-cycle, your system will lose efficiency, and there will be unnecessary wear-and-tear on your equipment. To make sure you do it correctly, check out our article on doing a Manual J heat load calculation.
  • Aesthetics. Let’s face it: mini-splits aren’t pretty. The cassette, or head, of a mini-split is quite bulky. While there have been a lot of improvements over the years, including drop-in devices, the look of the unit is not too classy.
  • Can’t humidify or filter the air. Since the air on a mini-split system is not circulating through ducts, you will run into the same problems as with hydronic systems: any solutions for humidifying or filtering the air will require an external workaround.
  • Not ideal for sub-zero temperatures. In Montana, sub-zero temperatures are common — which is not good news if you have a mini-split system. Even with a cold-weather package on a ductless mini-split, the system loses its heating output once temperature dips below fifteen degrees.

Summary

So what heating system do we recommend? We’re going to cop out and say: it depends on the application. Forced-air is the best application for an economical system that provides both heating and cooling. But as plumbers, we do love our hydronic heat. If you’re looking for a luxurious, efficient heat, hydronic systems are the way to go. Lastly, ductless mini-split systems are a life-saver for providing heating and cooling to systems that aren’t zoned correctly, or to home additions that aren’t worth running additional piping or ductwork for.

Have any other questions? Reach out to us today, and we’d be happy to help.

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