Heating and Cooling Solutions for Bonus Rooms

Rooms that don’t stay a comfortable temperature are something we spend a good amount of time helping customers with. These days, the most common small room heating and cooling problems we run into are bonus rooms, enclosed porches and garages that people want to use as workout rooms or shops. Of these, the bonus room above the garage…or as some people have called it, a FROG (Finished Room Over Garage). All of these tend to share the characteristic that they are too hot or too cold most of the time. The bonus room issue is probably more frustrating to most homeowners since they expect it to be heated and cooled like the rest of the house, but it often doesn’t come close to matching the comfort in other spaces.

Photo of inside of a bonus room which are typically harder to keep comfortable than the rest of the house

Why Bonus Rooms Are Often Heating and Cooling Problem Spots.

Bonus rooms are almost always built over garages. This is one of the big reasons they are a problem spot. Most rooms in your house back up to other comfort controlled areas. A bedroom might have a couple outside walls with a ceiling that borders attic space, but there are usually still a couple of interior walls that don’t cause heat gain or loss to the room. Bonus rooms tend to be on a heating and cooling island. Usually, the ceiling borders the attic, the floor is over an non-temperature controlled garage, and 3 to 4 walls also border attic or the outside. Since they are surrounded by hot or cold on nearly all sides, they are more likely to have comfort issues. That’s because they heat up (or cool down) faster than most rooms in the house and generally don’t have their own thermostat or air return. When the door is shut and the rest of the house is comfortable, the system feeding this room won’t turn on, allowing the temperature in the bonus room to vary greatly from what your thermostat is set to.

Solutions for Bonus Room Comfort

Depending upon how often you use the room, what you use it for, and how bad your temperature swings are, there are a number of possible solutions to improve comfort in a bonus room or FROG.

Smart Thermostat with Sensors

smart thermostat with sensors to improve comfort in hot or cold bonus rooms

One of the newer options available now, that wasn’t just a few years ago is changing your thermostat to a smart thermostat that can accommodate room sensors. Small sensors can be placed in multiple rooms so that the HVAC system is not just relying on a single data point (the thermostat location) to determine whether to kick the A/C or heat in. You can set these sensors to average across two or more locations. Placing a sensor in your bonus room and averaging it with the thermostat should kick everything on a little more often and reduce the temperature swings in the bonus room. This will work wonders if your temperature swings are only a few degrees. However, if the temperature in your bonus room gets extremely out of line with the rest of the rooms the thermostat is controlling, you might find this approach will leave everything uncomfortable.

For example, if the thermostat is set to cool the home to 75 degrees, but it can get up to 85 degrees in the bonus room during normal operation with your current thermostat, averaging won’t help a lot. The smart thermostat will see the 75 degrees from your thermostat and the 85 degrees from the bonus room and kick the system in. If your air conditioner drops the temperature in both rooms 5 degrees (to 80 in the bonus room and 70 at the thermostat), the system will kick back off. Now you are still hot in the bonus room, but cold in the rest of the house. No Good.

Adding some additional sensors would keep the main part of the house from getting so cold, but will also keep the system from kicking in as often, leaving the bonus room still too hot. This is why most of the time, simply adding a smart thermostat and sensors won’t solve your problems.

Window or Portable Air Conditioner/Space Heater

Window air conditioning unit - an option for cooling bonus rooms

Another option is to buy a small window or portable air conditioner and install it for the summer months. The more expensive models have temperature controls, timers for on/off operation, and even remotes. In the winter, you’d need to switch out the A/C window unit for a space heater.

Using a window A/C unit and space heater can provide comfort in these spaces rather well, but has drawbacks as well.

You can’t use this method if:

In addition, there are a number of other negatives to using this method:

  • Window A/C units are ugly on the outside of your home
  • Noise – Window and portable A/C units are typically much louder than other options
  • Dust, Dirt and Grime – Window units tend to let in dirt, insects and make a mess around the window
  • Possible water damage – Drain issues have been known to cause water leaks that impact window sills, walls and carpeting
  • Increased Fire Risk – The U.S. Fire Administration says window and wall air conditioning units cause 55% of all air-conditioning equipment fires, even though they account for just 35 percent of the air-conditioning equipment in residences. Space heaters are a well known fire risk.
  • Cleaning, moving and storing the A/C unit during the winter months

Adding a Zone to Your System

Adding a 2nd zone to your current system is another possible solution to keeping the bonus room comfortable. Whether this is the best solution depends on the size of your bonus room compared to the rest of the house and other factors. Adding a zone allows the HVAC system to turn on or off in that area of the house (in this case the bonus room) without impacting the rooms in other zones. Your bonus room would have its own thermostat so you can control the temperature.

However, there are some considerations that may not make adding a zone the best solution.

  • Depending on how your duct work has been run, it may require extensive renovation of your duct work.
  • You’ll like have to have the system dump extra air someplace because the bonus room will be too small for the full air flow from the system.

Adding a Ductless Mini-Split (or ducted mini-split)

ductless air conditioning system in a television room

Ductless mini-split systems are built for smaller spaces. These are very common in small apartment living in Europe. Instead of using ductwork, the main system hangs off the wall, while an outdoor unit operates in much the same way most heat pumps. You can get ductless systems with both heating and cooling, which provides you with year-round comfort. You’ll either have a thermostat in the bonus room or use a remote control to adjust the temperature.

Ductless mini-splits are built for small spaces, which makes them ideal for bonus rooms. They will be on the more expensive side of the possible solutions listed above, but likely in the same price range as adding a zone. They are quiet and efficient which also makes them a great solution.

In some bonus rooms, there isn’t a lot of room to put a ductless unit on the wall. In this case, there are some ducted mini-split options that could come into play. They use the same type of small system technology, but hide the air handling unit in the attic and use ductwork to deliver the air flow to the room.

Something People Ask About That Isn’t a Realistic Solution

2nd Standard A/C Unit

An unlikely solution, but one most people wonder about. The smallest central A/C units out there are general 1.5 ton units. Using an old rule of thumb (not the proper way to size an air conditioner to your space), that says 1 ton of A/C can cool about 600 square feet of your home, you can see the problem. The smallest traditional units cool small homes, not small rooms. Even if your bonus room is a generous 250 square feet, this unit will be extremely oversized. And then there is the problem and expense of having to install a second furnace. Not a solution any good HVAC contractor would recommend.

Finding the Right Solution for You

Heating or cooling your bonus room so that it works for you is a matter of finding the right solution for the way you use the room. If you use the room regularly and for many hours at a time (including as a bedroom), a permanent solution like a zone or a mini-split will be the best for your lifestyle. If the bonus room only gets occasional use, then a less expensive solution, like a window air conditioner might do enough to solve the problem for you. Permanent solutions come with a higher price tag, but also provide you with a room that can remain comfortable 24 hours a day.

If you do want to explore permanent solutions, the best approach is to talk to a reputable heating and cooling contractor. They can examine the space involved, take note of the current heating and cooling system and provide you with recommendations and pricing on solving your bonus room temperature issues.

For the Charlotte area, we’d like to be the heating and cooling contractor that helps you live in your bonus room again.

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