Should I exhaust my central vacuum outside?
Let's use some common sense...

Let's take a moment to fill you in on our own professional thoughts, and what seems to be the latest trend for central vacuums. Venting central vacuums started back in the 70's and lasted through the 90's. People would either vent them up into their attics, crawl space or outside away from the home. It sounds good in theory, but there are some major problems with doing either, which we will get into more detail throughout this page. One big reason is that venting your central vacuum in the attic or outside can lead to potential motor and heat problems, which could potentially cause a fire.

Going Green Helps Not Only the Environment, but Allergy Sufferers As Well.

In 2002, the Division of Allergy and Immunology at the University of California, Davis, conducted a clinical study that proved a link between central vacuum systems and allergy relief. The study found that patients experienced a 40% to 61% improvement in their symptoms when they switch from using a portable vacuum to a built-in central vacuum system to clean their homes. Thanks to UC Davis, Builders Magazine and the American Lung Association for supplying this information. - National Association of Homebuilders, Green Building Standards One important note of caution, if your primary concern is removing dirt, dust, pet hair, allergens, etc.. then venting the central vacuum outdoors is an option, but we have found it to be certainly not the best idea for environmental reasons because it will suck out a lot of conditioned air from inside your home which will increase your utility bills, it really makes common sense. We recommend that a true finer filtration system such as the ActiVac II (seen below) that does not require the exhaust to be vented outside. It's more eco-friendly to have an airtight insulated home.

 About Central Vacuum Motors:
Central vacuum motors are engineered for suction only, not to be used as a blower. Motors are designed to have an intake valve/opening, which is where the suction comes from, and an exhaust valve, where old air can be vented out to keep the motor cool. The majority central vacuum units have a built-in filter to protect the motor and your health. All the motor is designed to do is suck in air. The dirt and dust being sucked up to get trapped in a filter, bag, or cartridge. This keeps any unwanted particles from going into the motor. A good example would be a swimming pool filter. The water goes through the filter to clean it out and the filter retains any dirt and debris, leaving the only clean water and protecting your pump from any debris. Back in the day, central vacuums were very loud while the motor was working. These days you can simply put a muffler on the exhaust to reduce the noise by up to 6 decibels. Older central vacuums before the 1990's did not have the greatest filter system so particles were often caught in the motor. About 8-10% of what was picked up just gets exhausted right through the motor, decreasing suction power and motor life, making venting even more important. This didn't paint a clear picture of hygienic dust removal back in the day.

Venting in your Attic:

Venting in the attic is done for two reasons, mainly for noise reduction. It was quieter to just vent into the attic. Also, since warm air rises, people figured that the attic would be a suitable place to vent to. However, there are some major problems with doing it this way. Since older motors gave off more heat than they do today, it could pose a serious fire hazard. The heat coming from the ventilation pipe was often very hot, and could easily melt things such as PVC pipes being used through the house. If a spark from a bad motor should fly up into your attic, it could easily ignite your insulation on fire. Also, since all the dirt and dust and germs that were vacuumed up are being vented right above you in the attic, those particles would just settle to the floor and absorb into the insulation. The vent was basically just an open pipe, so any object blocking or partially blocking the opening could melt or ignite whatever was blocking it. Even worse, smaller objects could just fall right into the open tube down into the vacuum, potentially ruining the motor and causing a fire. Back then, there were very few regulations for venting central vacuums, unlike today. There were no building codes that were enforced and some house fires were started this way until building regulations kicked in and started enforcing safety laws. Today's motors are engineered with airflow in mind, keeping them cool and prolonging the life of the motor/unit.

Central Vacuum - Venting Outside:
When you exhaust a central vacuum system outside, there could be numerous problems you may possibly encounter. In the worse case scenario, it may cause a potential fire hazard. For example, a dryer vent. Here are some thoughts from some companies that don't approve of the idea. After all the many years of venting outside or in your attic, it is no longer a mandatory practice as it will suck much-conditioned air from inside your home and exhaust it outside, thus increasing your utility bills. Your heating bill goes up in the winter, sometimes caused by your central vacuum as well as your air conditioning cooling bill in the summertime. That is just wasting your hard earned money. You might as well put the air conditioning on and open the windows and front door and leave.

To the right is a typical outside central vacuum exhaust vent. The flaps (or louvers) open when the force of the air being exhausted from the central vacuum push them open, and close when it's not being used. Now, what would happen if you live in a place where it snows regularly? All of the snow and ice would freeze over and cover the flaps, keeping them shut and suffocating the motor. That would lead to it overheating and possibly failing or igniting. Again, the idea of a motor is to suck in air and exhaust air out.

What would happen should your motor start suffocating? Within 30-60 seconds, it would rev up to a screaming decibel level, and a lot of back pressure would build up. You'd also start to smell the electronics burning from the heat. The PVC pipes connected to it would start to melt from the extreme temperature, which could cause a fire hazard. It would start violently vibrating and quite possibly fall right off the wall, and if it landed on anything flammable like cardboard or paper...well, you'd have a problem on your hands. It could potentially cause a catastrophic failure and most likely will destroy your whole central vacuum unit. The motor is considered the "brain" of the unit, and just like humans if the brain is not getting enough air it will die. It could turn into a fire safety nightmare. There's always the possibility, so taking the proper steps now will save you from any problems later.First, to make the initial venting opening, you have to drill a 2 1/4" hole from the inside of your house to the outside. Another big problem with outside venting is flooding. Since you're drilling a hole that goes inside your home from the outside, any rain and water that falls can leak through and flood your basement or garage.

A lot of people also were complaining to their servicemen that their house was infested with all kinds of rodents and bugs. Little bugs and varmints like ants, bees, and roaches, even mice, and rats, are able to crawl right down the exhaust tube, or even travel between the pipe and housing material into your home where they continue to breed and cause infestations.

On extremely hot days, direct sunlight could melt or warp the plastic flaps on the exhaust vent shut, preventing it from venting.

On very windy days, you wouldn't want the dust and everything else that was exhausted to be whisked back inside your home through a window, carport, or open door.

Like the illustration to the left shows, sometimes the length of the exhaust pipe which includes the 'elbows' causes the motor to strain. It's like blowing too much air through a drinking straw, it causes back pressure, which in turn causes the motor to work harder. Again, motors were made to suck in air, not blow it out. When venting, the longer length of the pipe means it has to work harder to move the air out and can cause a back pressure that harms the central vacuum unit.

The two largest motor manufacturers (Ametek and Domel) don't really have an official opinion on how to vent their motors, the main focus is to have them run as cool as possible without any dirt, sand, or exhaust back pressure occurring. From an engineering standpoint, central vacuum motors require a balance of air flow. The delicate balance means the air that gets sucked into the motor must be allowed to be released somewhere equally. If the balance is thrown off, problems will occur and in turn, will cause a loss in suction and shorten the life of the motor.

If you decide to vent the central vacuum system exhaust outside you are limited to installing it within a short distance from the exterior wall. It limits the placement options of where you can place the unit, and it could cause you to have to rearrange where you have things placed just to make room for the vacuum. If you choose to install an outside exhaust vent/louvers remember the outside elements such as rain, snow, sleet, and humidity cause the dust to stick on the side of your house near the exhaust vent. On a windy day, that very same dust and dirt may even be blown back into the house through an open window. If you still decide to exhaust, you could use one short straight piece of the tube directly outside (recommended - no more than 6 to 8 feet from the central vacuum unit).  In conclusion, we are not opposed to venting outside, we just believe that the outside elements should stay outside and that there is a better way to vent your central vacuum.

The newest and best way to exhaust your central vacuum is through an ActiVac II Exhaust Filter with advanced HEPA and charcoal filtration capabilities.  No more breaking another hole through your building. The ActiVac II Exhaust filter installs in just minutes and is easy to maintain thus eliminating the problems mentioned above. 

Customer Warning

Cyclonic or "true-cyclonic" systems have to be vented outside, but the average customer wouldn't figure that out until after they've actually bought the vacuum and read the instructions. If you asked a typical pushy salesman
"why do I have to vent outside?" they will try to dodge the question because that is a very big downside to cyclonic vacuums. That should send a RED-FLAG to any customer. Not only is it a filthier system to clean out and maintain, but a small percentage (3-9%) of the lighter dust such as carpet fibers, pet hair, and regular dust typically get sucked up into the motor entering the fan blades, bearings, armature, and the electric components.

You may now know this, but approx. 4-6.5% of that actually PASSES through the motor, and that is EXACTLY the reason why you MUST vent outside - the dirt would otherwise be vented into your home where it came from. Dirt and dust that don't pass through it get caught in the motor easily, causing it to heat rapidly and can lead to premature motor failure. This is why cyclonic vacuums typically have a lower life expectancy. Think of it like a clothes dryer, after a while the lint starts to pile up and blocks most of the airflow. Like the header to this page says, let's use some common sense here. Without any ventilation, it could overheat and cause a fire. 98% of the top central vacuum manufacturers do not believe in a gimmicky theory like "true-cyclonic". Some of the claims you would hear coming from a company who pushes cyclonic vacuums would be "never loses power", "no filters to clean", "no loss of suction", and so on. Be careful of these shady marketing tactics.

Click here to learn more about cyclonic vacuums.

* We've also heard some mistruths on the internet about people claiming their own private-labeled cyclonic central vacuums are like the world-famous Dyson vacuums which are heavily advertised on TV, which is also cyclonic and needs no bags. But the real truth is, it's completely the opposite. Dyson's have a HEPA filter built into it, knowing that there are particles that still get through the system, and their patented technology is considered "true" cyclonic. Trust us, we sell them in our retail store. The private-labeled cyclonic systems try to affiliate themselves with the Dyson name by listing similarities between their vacuums, just because Dyson's are well known throughout the world. A very cheesy marketing strategy. ...To be continued...
The information provided is the opinion of ThinkVacuums.com