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Pros and Cons of Installing a Furnace in the Attic


Typically, a furnace is installed in a basement, garage, or some closet on the ground floor. However, you’re not necessarily limited to those options. Many homeowners choose to place their furnace up in the attic, especially in areas like California where basements are less common. It’s always a good idea to question the placement of your furnace and explore every option, even if you do end up just putting it in the usual space. Whether or not an attic-based furnace is a good idea will depend pretty heavily on your situation and preferences. Here’s a little information on the pros and cons of installing a furnace up in the attic instead of on the ground floor or basement.


Pros of Installing a Furnace in the Attic


Many of the pros and cons of putting your furnace up in the attic will depend pretty heavily on the state of the attic itself. We recommend bringing a professional out to take a look at the room before making a decision one way or the other. That way, you’ll know if your attic is properly set up for a furnace or not. If the attic is outside what we call the “thermal envelope,” then the benefits of putting a furnace there are always going to be outweighed by the negatives. However, if your attic is fully sealed inside the thermal envelope, which means heat won’t escape through cracks or other open spaces, then you should be fine to consider both the pros and cons. Here are a few benefits of an attic-based furnace.


Ease of Installation


This particular benefit will depend pretty heavily on the size and shape of your attic, and whether or not it’s fully finished. A cramped or unfinished attic will be difficult to move around in, making installation significantly more complicated. However, if your attic is in good shape and finished, then there should be no problem installing a furnace up there. An unfinished attic isn’t really a good place for a furnace anyway, since it’s likely not included in the thermal envelope of your home and therefore isn’t sealed tightly enough to keep heat from escaping.


While older furnaces would have been difficult to fit in an attic due to their size and shape, modern furnaces are much more flexible and offer significantly more options for installation. They tend to have multiple components that can be shuffled around a little bit to fit better and can now be installed either horizontally or vertically, depending on whichever orientation is an easier fit for your attic. In fact, it’s often a lot easier to install a furnace up in your attic than down in a closet or tucked away in the garage. That makes this advantage especially relevant to people who live in California or other places where full-sized basements are rare. Instead of trying to squeeze the furnace into a tiny closet, you can have the full space in the attic available.


Despite the relative ease of installing a furnace up in your attic, we still wouldn’t recommend doing it yourself unless you have a ton of experience with HVAC systems. Even the simplest furnaces can be pretty tricky to install, and any mistakes can have severe consequences later on down the road or even present a fire hazard. A professional HVAC contractor is your best bet, even if you consider yourself to be relatively handy. The risk of a subpar installation is too great to mess around with, especially if you don’t want your power bill to skyrocket.


More Storage Space Downstairs


This is probably the most significant and relevant benefit for most homeowners. Anybody who owns or even rents their own home knows how precious storage space can be, especially if you have a whole family living there. It’s easy to collect a ton of stuff over the years and, next thing you know, every closet in your house is suddenly filled with Christmas decorations, ski equipment, and anything else that you need to have packed away most of the time. Although furnaces have become increasingly compact over the years, it’s still difficult to store things in the same closet, especially since you need to be able to access the furnace now and again for maintenance purposes. Once you install a furnace in a closet or a corner of the garage, it owns that space pretty much indefinitely.


Placing your furnace up in the attic obviously provides you with more storage space downstairs. As a general rule, storage space on the ground floor is much more valuable than up in the attic since you don’t have to pull down the ladder and climb up to access the stuff kept there. By putting the furnace up in the attic and bringing stored stuff downstairs, you’re able to keep more frequently needed items closer to you and keep an appliance that you rarely need to visit upstairs.


Furnaces also have the added drawback of being fairly unsightly, which means putting them in the garage or in a room downstairs can take away from the decor you have there. For better or for worse, attics are rarely thought of as well-designed spaces, so large metal units like furnaces will fit right in among the cobwebs and exposed beams while leaving the downstairs public area nice and clean for home decor.


Dust Mites in your HVAC Ducts


Lower Cost of Installation


The cost of buying and installing an HVAC system, including a furnace, can be pretty significant. Currently, the national average is between $2,000 and $6,000 all told, which is a hefty chunk of change. If you’re on the fence about where you should put your furnace and all the other factors are balancing out, then the cost of installation can easily become a tipping point. Putting your furnace up in the attic can shave down that cost by a notable amount, saving you a little extra money that you can put towards something else in your home.

The cost of installing a furnace in the attic will depend on whether you’re putting in a new system or replacing an existing furnace somewhere else. Every furnace requires two sets of ducts for the central air system. One is the usual duct system to distribute warm air throughout the house, and the other is to vent exhaust away from the furnace to the outside. That second set of ductwork is where the savings come in. A furnace installed in the attic can just vent exhaust through a hole in the roof directly outside instead of having to pass it through ducts first. This saves you the cost of both purchasing and installing those ducts, which can be a pretty solid amount of money.

Of course, if you’re replacing an existing furnace somewhere else in your home, the exhaust ducts are probably already there and you can just attach the new furnace to them. That means moving an existing heating system up to the attic from the downstairs isn’t going to save you any money on installation, although the other benefits still apply. In fact, having to create new access points for the existing ductwork will make putting your new furnace somewhere else more expensive than just plugging it in wherever you had the old one.

Lowered Risk of Flooding


This may not be a relevant factor in every climate, but those of us who live in areas that get a lot of rain know how serious the water damage from flooding can be. Whether it’s from heavy rainfall, melting ice, or a busted sump pump, flooding inside your home can cause a ton of damage to everything it reaches, including the furnace. Anything located in the basement is especially at risk, although houses without a basement can easily end up with a flooded ground floor.

As you might imagine, placing the furnace up in the attic significantly reduces the risk of water damage from a flood. The water level during a flood is rarely higher than a couple of feet above the ground, which means that anything on the higher floors or in the attic is perfectly safe. Of course, it’s possible to experience flooding severe enough that it reaches the attic, but in that situation, you have significantly bigger problems than just the furnace. The Bay Area is considered to have a severe risk of flooding when compared to the rest of the country, so if you live here in our service area, the potential of a flooded ground floor is something to keep in mind.

Any furnace damaged by a flood will almost definitely have to be replaced entirely. Furnace units aren’t really designed to handle water damage, and in fact, a flooded furnace can easily create a hazardous situation on the ground floor. Of course, anything placed in an unfinished attic is also vulnerable to water damage from regular rain coming through holes in the ceiling, so it’s important to make sure your attic is fully conditioned if you’re considering installing a furnace up there.

Cons of Installing a Furnace in the Attic


We’ve talked a bit about the benefits of putting a furnace up in the attic, which means it’s time to address some of the downsides. Even if your attic is fully inside the thermal envelope of your home, we tend not to recommend putting a furnace up there for reasons we’ll detail below. Still, don’t let that discourage you if you feel it’s the best solution for you. After all, everybody’s home is different, and it’s possible that an attic furnace is ideal for your house.

Problems May Go Unnoticed


One benefit of an attic furnace that we didn’t mention is that it’s a lot easier to ignore the sound when it’s all the way upstairs. This is generally mentioned as a positive thing by homeowners, but it can actually be a serious drawback for the long-term health of your furnace unit. Out of sight, out of mind, as the saying goes, and that can lead to some pretty major problems if you’re not careful to check on your furnace regularly. It’s easy to accidentally miss some minor sign of a small problem and end up having to pay a ton of money to fix it when it turns into a big one.

Strange sounds are the most commonly noticed signs of a problem inside your furnace, whether that’s the squeal of a grinding motor bearing or the buzz of a broken piece vibrating inside the unit itself. By placing the furnace up in the attic, you save yourself from having to hear it working all day every day, but you’re also much more likely to miss potential issues when they first arise. If you’re waiting to fix a problem until it starts to seriously affect the actual function of the unit, then you’re already on the road to higher repair bills.

Having the furnace out of sight can also lead to a lapse in regular maintenance, which is extremely important for the lifespan of the unit. When you’re not regularly seeing and hearing the unit, it can be tough to remember to swap the air filters, for example. If you do have a furnace in your attic, or you’re just a generally forgetful person, we highly recommend marking regular maintenance tasks like switching filters on your calendar so you don’t leave it for too long.

Increased Chance of Damage to Ductwork


While it’s tempting to put most of your focus on finding the best HVAC units to heat or cool your air, the truth is that your ducts are just as important, especially when it comes to energy efficiency. Poorly maintained ducts can leak heat and force your furnace to work harder to keep your home warm, sending your power bill through the roof. It’s important to keep in mind that when you’re deciding where to place your furnace unit, you’re also deciding where the ductwork is going to be. Unfortunately, an attic isn’t usually the best place for ducts.

Because hot air rises, the attic tends to be the warmest room in any house. This is compounded during the summer months when the sun beats down on the roof, transferring heat to the attic below. This can make the attic a pretty hot and uncomfortable place to be during the summer. Not only that, but the heat can actually cause damage to your ducts.

When any material is heated, the atoms and molecules that form it start to move more, creating kinetic energy. This is essentially how any heat transfer works – as atoms move faster, they create more energy that’s felt as heat. However, the movement also causes the atoms to spread a little further apart, expanding the material. This isn’t usually all that noticeable, but when the metal that ducts are made out of starts to expand, it can create small holes and tears in the ductwork. The hotter the room, the higher the risk of damaging the ducts and even the smallest pinholes in the ductwork can cause problems for your HVAC system. The air escaping through the small holes will cause them to get bigger and bigger until you’re losing enough heat that it starts to affect the efficiency of your furnace. Because attics are usually the hottest room in the house, the risk is higher there than elsewhere in your home.

Lower Overall Energy Efficiency


We touched on this in the last section, but one potentially significant effect on the energy efficiency of any HVAC system comes from a form of heat transfer called convection. Remember how heating any material causes the atoms to spread apart and the material itself to expand? This works for air too, and it’s the reason why hot air rises and cold air sinks. As the atoms in the air spread further apart, it makes the warm air less dense, and it’s displaced and forced upwards when gravity pulls the denser cold air down towards the earth. That’s why the attic is the warmest part of the house, and it also creates a problem for a furnace placed up there.

When you have a furnace installed in your basement, you have convection working in your favor. The warm air that’s been heated by the furnace will naturally flow upwards through the ducts to the floors above, which means that the fans in the furnace don’t have to work as hard to distribute it. However, if your furnace is in the attic, you need the warm air to go down to the floors below it. Because hot air naturally wants to go up, the furnace will have to work extra hard to force it down through the ducts into the rest of your house. When the furnace works harder, it requires more power, and suddenly your electricity bill is going up, up, up.

There’s another problem that comes along with this, too. In order to ease the strain on the furnace’s blower fan, an HVAC contractor will usually make more duct openings leading to the lower floors. This helps mitigate the effects of convection, but it creates its own efficiency-related issues. Any hole in the thermal envelope or joint in the ductwork is a potential spot where heat can leak out. Unless you have heat blowing into your attic to create an equal temperature, warm air from the floors below will leak up through the duct openings to the attic, creating inefficiency. This problem is compounded by the joints in the ducts, which are weak spots and tend to spring leaks. These leaks will only allow more treated air to escape, again forcing the furnace to work harder. Between these two factors, the energy efficiency of an attic-based furnace is pretty far below a ground-floor or basement unit, so you’re likely to experience higher power bills every month.

This problem is really the chief drawback of placing a furnace in your attic. While most of the other advantages and disadvantages are small quality-of-life issues, poor energy efficiency can make a serious dent in your pocketbook. Generally, this is the reason why we don’t recommend installing a furnace so high up. However, there are some instances where the pros will outweigh this fairly significant con, so make sure you’re doing all the research before you make a decision one way or the other.

Get in Touch With a Professional to Help Make Your Decision


When you weigh the pros and cons of putting a furnace in the attic by themselves, it’s pretty easy to see why most people place them in the lower parts of their homes. However, this decision never exists in a complete vacuum, so there are plenty of factors specific to your house that should be considered before you come down on one side.

We highly recommend getting professional help to take a look at your home before you make the decision on where to put the furnace. HVAC systems can be pretty complicated, and it’s easy for a regular homeowner to miss something potentially important when looking over their situation. Someone with years of experience in this industry, however, can let you know everything you might have missed and help you make a more informed decision. With consultation from a heating professional, you can make the call knowing that you have all the information to help you enjoy efficient and consistent heat for years to come.

If you’re in Marin, Sonoma, or Napa Counties and you’re thinking of installing a new furnace, or you just want a little more information on where HVAC units should be placed, feel free to get in touch with Valley Comfort Heating & Air. We have all the experience your project will require, whatever it might be, and our towers of positive reviews showcase our strong commitment to customer service. You can give us a call at (707) 664-7201, or get in touch with us through our website here.