Ask a Designer, Custom Residential
HVAC and the Residential Remodel, Part 1: Treated Air Systems
You might not be Pinteresting HVAC systems for your home remodel, but if you overlook it, you'll regret it! The products might not always be photogenic, but that doesn't mean you don't have some important choices to make. In this installation, Sara Emhoff explores the pros and cons of mini-splits versus forced air systems.
June 16, 2016
Welcome to the rabbit hole that is heating and cooling options! During the course of a remodel or addition, one thing that often goes overlooked during design is the heating and cooling system. Many times, the existing systems are old, inefficient, and just plain in need of a change. The possibilities for new systems are seemingly endless, and good comparative information on different systems is often hard to get your hands on. In this series, we will attempt to talk through the pros and cons of the solutions available, and take away some of the confusion surrounding them. After a brief description, the cost, nuisance, and efficiency information will be listed for reference. For this first installment we will look at two systems that are fairly common, just to get the ball rolling: full forced air and ductless mini split.
Full Forced Air System
This is the most traditional and ‘mainstream’ solution that involves pushing conditioned air through the house. It involves a central air handler (ideally placed in a central location in the home) and metal ducts that will need to be positioned throughout the house, venting into each room. Many homes take advantage of forced air, but if we are installing a new system, or adding additional square footage to your home, it's not always possible to hide the ductwork inside the walls and floors. So, in those remodel conditions, a forced air system likely means the addition of soffits in the ceilings of the basement and main floor (or lowered ceilings in some of the main floor rooms altogether), and a chase that would allow the duct work to connect between floors.
Even though they lower the ceiling, soffits aren't always a bad thing – sometimes they even help shape a space.
Soffit Hiding Ducts for Forced Air Systems
Often, this is the most cost effective solution, as it’s a tried and tested technology, and it supports both heating and cooling solutions in the same delivery system. When you opt for heating and cooling, you will need both the air handler (usually gas or oil fired), as well as a separate air conditioning condenser unit, which can be a large and loud addition to your yard.
Condenser for a Forced Air Cooling System
These condensers are often quite large; hopefully you can hide them somewhere.
Here in Western Washington, it's quite common to not bother with air conditioner, but – with or without the AC unit, and, for better or for worse – forced air systems are by far the most common systems in residential projects.
Cost: $$
Nuisance: Many systems can be very loud. You usually know when the heat (or air conditioning) is on.
Efficiency: New heating systems can be very efficient, up to an AFUE rating of 98%! (The AFUE, or Annual Fuel Utilization Efficiency, rating is how the federal government measures efficacy. Anything over 90% is considered a high-efficiency heating system.)
Ductless Mini-Split System
Mini-split systems are an efficient way to heat and cool your home, and work well in remodel conditions where ducts either don’t exist, or can’t be extended to additional places. Much like the forced air system above, these guys have two components: condensers and air handlers. An outdoor condenser unit is usually smaller than the large condensers shown for the forced air AC system above, and are augmented by several small air handlers that are placed inside individual spaces.
Mini-Split Condenser
These aren't the most attractive pieces of equipment, but their smaller size makes them somewhat easier to hide than larger units.
Sure, these guys are not the most beautiful components on the planet. (Actually, they are very ugly, and I have resisted them for a long time, but recent advances in the product line have made me reconsider, which I’ll explain below.) However, their major advantage is that they are very efficient and require little to no displacement of ceilings and no vertical chase in the house. So, if you've got a good spot outside to hide it, you can preserve the look of clean ceilings inside.
Though, unfortunately, if we are talking about using this solution for a large space, or want separate control over many areas of a space, several of these units may be needed, as most units can only handle two to three interior air handling units, or zones. In some remodel situations, there is also the danger of design warts, such as gutter-sized tubing that connects a compressor outside to an air handler inside, perhaps even a floor up. Very conspicuous, not super desirable.
Another challenge is that each room, or zone, gets its own indoor unit that acts as a mini air handler conditioning that particular space. Until recently, the biggest drawback has been that the indoor units are big, bulky, and do not fit the aesthetic of your space in any way.
Mini-Split Air Handler
Typical mini-split systems include a large, less-than-subtle air handler mounted on the wall of the room it serves.
Fortunately, they have started rolling out ceiling housed “cassettes” that allow the unit to disappear more in to the ceiling like I’ve highlighted below: much better. Though this solution does require some ducting in the ceiling above the cassettes, which you'll need to be plan for.
Mini-Split Cassette
These systems are much more minimal, and begin to fade away much like the vents of a forced air system.
So, for the right case, especially for remodels and additions, mini-splits can be a viable solution, particularly as some of these aesthetic downsides are resolved.
Cost: $$-$$$, depending on size and zoning.
Nuisance: Have you seen those huge indoor air handlers? Not great. Also, they can have a hum that many find distracting.
Efficiency: Also efficient, but rated on the SEER scale, or Seasonal Energy Efficiency Ratio, with numbers reaching above 30, which is considered very high efficiency.
Next Up...
So, that's your quick review of forced air versus mini-split systems. Next time, I will walk you through hydronic heating options. Not all hot water heating needs to flow through your floors!
