Exhaust Fan Installation and Placement Guide

a close-up of a huge industrial exhaust fan with six bladesSometimes the easiest thing to do when a home exhaust fan needs installation and placement is to call a handyman. That can be pricey though, and some handyman agencies have inconvenient timetables which cause you to take a whole day off of work, just to sit at home and wait for them to come. With the following information and only a little bit of skill, you can change your own home exhaust fans—without dealing with the inconveniences of relying on a handyman.

How Placement Affects Fan Efficiency

Though home exhaust fan installation and placement is not necessarily hard, there is a right and a wrong way to do it. Placement itself has a large “system effect”, or effect on fan performance and efficiency. Below are some examples of how placement can affect fan efficiency:

Roof Exhaust Fans

an exhaust fan positioned on roof made from red tilesIn a normal roof exhaust fan, the roof exhaust fan will have a vertical straight duct. According to the AMCA Publication 210, the fan testing procedures outlined by the Air Movement and Control Association International, Inc. (AMCA), the normal, uninhibited performance associated with the vertical straight duct is refered to as “free inlet, free outlet.”

Any additional vertical straight ducts will have little to no effect on the fan’s performance. If, however, poor installation with horizontal ducts can cause an abrupt elbow at the inlet of the fan, causing poor performance. Installation of a damper can also cause significant fan performance issues.

Tube Axial Fans

Tube axial fans will generally be tested with straight inlet ducts and inlet bells, which is supposed to cause good performance. This would be refered to as “free inlet, ducted outlet” by the AMCA. If, on the other hand, the tube axial fan is installed with a poor inlet condition, then an elbow will be created directly at the fan inlet, causing the air entering the fan to be forced to one side. Installing the fan too close to the wall, which causes a poor outlet condition, can also cause performance issues since tube axial fans require an appropriate length of discharge duct in order to perform at an optimal level.

Centrifugal Fans

For good centrifugal fan performance, or “free inlet, ducted outlet” according to the AMCA, there are multiple options of proper installation. This is because centrifugal fans have so many pieces involved: ducted inlets and outlets, multiple available arrangements, discharge positions, and CW or CCW rotations.

For example, an elbow installed directly at the fan discharge will cause poor performance, but if you just select a fan with the correct rotation and discharge position, then the poor installation can be avoided. If you have installed an abrupt discharge into a plenum, install an elbow directly at the fan inlet, or install a duct design that causes inlet spin, then you may also experience poor performance.

Conditions That Affect Fan Efficiency

There are many conditions that affect fan efficiency, but most of those conditions can be divided into two categories: inlet conditions and outlet conditions.

two roof exhaust fans in front of a blue skyCommon inlet conditions include:

  • Elbows too close to the fan inlet
  • Abrupt duct transition
  • Inlet spin due to duct design
  • Dampers not being fully open
  • Damper locations
  • Poorly designed guards
  • Inlet boxes
  • Installing the inlet too close to a wall or bulkhead

Common outlet conditions include:

  • Elbows too close to the fan outlet
  • Abrupt transitions
  • Free discharge
  • Damper locations
  • Weatherhoods
  • Discharge guards
  • Installing the discharge too close to a wall or bulkhead

It may look overwhelming, to see all of the things that can be done wrong. Luckily, we gathered some tips here to help you avoid these installation problems. The first thing you need to do is make sure you understand how the fan you have chosen was tested. This information may be found by referring to the catalog statements under the fan manufacturer’s performance tables. Understanding how the fan was tested can help you avoid some of the common mistakes above. Another thing you can do to try to avoid installation problems is to consider using different types of fans.

Depending on your needs and the location of where the fan needs to be installed, a different fan may be a better choice. When installing centrifugal fans, make sure to select centrifugal fans that have the proper rotation and best discharge position for your specific situation. Finally, if space constraints require you to install an elbow at a fan inlet, also use an inlet box that has a predicted loss in lieu of the elbow.

Attic Exhaust Fans

Though ventilating your attic may not be the first priority on your mind when it comes to home maintenance, it is actually an important one. Attic ventilation can reduce the high temperatures typically in attics that can cause discomfort, decrease utility bills, and increase the useful life of your roofing materials. All you would need to do is install a few vents, and possibly a fan, in your attic.

Placement

the interior of an attic with ventilation shaftsVents for your attic exhaust fan should be mounted 24 inches below the peak. In addition to this, all exhaust vents should be installed at the same heights along your roofline. If you do not install all of the exhaust vents at the same height, then one of the lower-installed exhaust vents may become an intake and will diminish your ventilation program. Also, do not mix exhaust vents; choose either static exhaust vents or powered exhaust vents. Instead of correctly pulling air from the intake ventilation, the powered exhaust vent will instead pull air from any static exhaust vent around. This, in turn, will reduce the airflow in your attic.

Installation

Once you have determined what your house’s current attic ventilation is, then you can determine how many and what kind of vents you will need. The two types of fans used in attics are those made for roof installations, and those meant to be mounted into a gable wall. First you will need to install the shutter by removing the old one and installing your new piece in its place. You may need to use a saw to get rid of any obstructions.

You will screw in the shutter and caulk it, after which you will nail the old blocking in place. Then you will need to mount the fan after cutting a hole in the mounting panel. Orient the fan assembly vertically, and then finally wire the fan. You may need to change the circuit to accommodate your fan. You will need a bit and drill to bore the holes, pull the cable through, and staple it within 8 feet of the block.

After you connect the matching wires to their leads, you should replace the cover and set the temperature to 105 F. To finish the wiring, go back and attach two 8-in. lead wires to the pull-chain fixture. Connect a black lead to the brass terminal screw; then attach the white wire to the silver terminal. Finally, join the wires that have the same colors within twist connectors before mounting the final product.

Bathroom Exhaust Fans

Bathroom exhust fans might be the most important ones in your home. Between moisture and smells, you want to make sure this is a room that stays ventilated so you don’t end up with dangerous mold.

Placement

The best place to put your vent is usually on the ceiling or by the shower, as it will have the most effect there. Also, remember to keep your vent away from your air intake source.

Installation

a man inserting a bathroom exhaust fan into a hole in the tile on the wallFollow the instructions that came with your fan and make sure your attic exhaust fan is powerful enough for the size of the room. Blow the air outside instead of to another part of the house, and install a wall or roof cap that will close when the fan is off. Insulate your ductwork properly if you live in a cold area. When installing your vent, use smooth ductwork and keep the length as short as possible so it doesn’t get in the way of anything else. Also, make as few bends as possible in the ductwork. You may need to be strategic.

Kitchen Exhaust Fans

Kitchens are also a very important area to keep the air moving properly. Most kitchen exhaust fans are over the stove in the range hood, and they work to cut down on grease, smoke, and fumes in your home.

Many rv vent fans will also be placed near the kitchen area to help with ventilation for cooking odors.

Placement

There are two kinds of kitchen exhaust fans:

  • Ducted kitchen exhaust fans stir air through a duct before releasing it outside. Installing ductless kitchen exhaust fans is an expert level job. The ducted fans also remove moisture.
  • Ductless kitchen exhaust fans, on the other hand, draw the air from your kitchen and through a carbon or charcoal filter before recycling it back into your kitchen. Ductless fans will need to be cleaned or replaced every year, but they are more versatile and can fit almost anywhere in your kitchen. They don’t remove humidity, so your kitchen can become quite humid.

Installation

a stylish modern kitchen exhaust fanDuctless kitchen exhaust fans don’t require ductwork or piping but do need their own electrical outlet. Before you get started, measure to make sure your new fan will fit. Your new fan will come with instructions, which you should follow carefully.

Installing a ducted exhaust fan is more complicated because it requires you to pipe the exhaust outside. You may have to install the piping yourself and put it through your wall, which is a complicated job. You will also have to use a saw or drill to cut through the drywall before caulking and replacing your vent cup and mounting your hood. Remember, turn off the electricity when installing an electrical appliance.

When to DIY and When to Hire a Professional

As a general rule of thumb, don’t attempt anything on your own that could cause a real disaster that would cost a lot to fix. Plumbing, heating, and electrical work are all areas where there is a lot that could go wrong. Even then, there are some simple jobs which you could handle on your own, such as a simple leak with an obvious source.

The most important thing to do is get advice from a professional. That is easy to do nowadays, as many professionals have free videos which show how to perform simple do-it-yourself jobs. So don’t try to rewire your house or remove your own walls without help, but do simple projects like laminating your own counters, refacing your cabinets, or installing battery-powered lighting in your bathroom.

Even if you hire a professional, you can probably save money by finding deals on the equipment and materials you need. As long as it is quality, your professional should be willing to use your discounted products.

Conclusion

industrial sytle exhaust fans in a buildingInstalling your own exhaust fans is a project you can probably do yourself, but you need to be careful and make sure that you are comfortable with all the steps. For instance, if you aren’t comfortable working with tools, it might be a terrible idea for you to use a drill even for a small project. Also, make sure that you assess the situation carefully. You don’t want to use the wrong size or materials on your project, as that could lead to problems down the road. If you need help, it never hurts to ask. The more projects you do on your own, though, the more confidence you will feel and the more you will be capable of.