Guide to Installing Ventilation

We know about the benefits that ventilation provides for both homes and the people living inside of them. Proper ventilation eliminates bad smells, reduces the likelihood of buildup from mold and other nasty microorganisms, and allows a home to maintain a comfortable temperature.

Good ventilation ensures that you have clean air to breathe while cooking in the kitchen or taking a shower. This fresh air also ensures that the structure of your home stays in good quality.

But how do we move from understanding the problem to providing a solution?

Let’s talk about how to install ventilation. Even if you’re not a contractor or someone who is planning on manually installing ventilation to their home – knowing about these steps is still useful. Your home is a big investment after all!

In this article we will walk you through how to prepare for a ventilation system installation, the tools you’ll need to install inlet and exhaust vents, a step by step guide to the vent installation process, and then finally how to test that the system is working.

This article will focus on the installation of inlet and exhaust vents in ‘balanced ventilation systems.’ While there are many types of ventilation systems available (such as natural ventilation, exhaust, supply, mechanical ventilation and energy recovery systems), focusing on a balanced ventilation system will allow us to explain aspects relevant to both the exhaust and supply ventilation systems.

A balanced ventilation system is designed to supply fresh air to areas where you spend the most time (such as bedroom and living spaces) and exhaust moisture and pollutants from areas where dirt air accumulates (such as the kitchen, laundry area, and bathrooms).

The balanced ventilation system that we will describe in our example today involves just one fresh air inlet and one exhaust air outlet that are connected to a heat/energy recovery ventilator (HRV or ERV).

The fresh air will enter through inlet vents on the wall of your home – this will feed air through a duct that supplies air to the HRV/ERV and then to bedrooms and/or living space.

The dirty air will be fed through duct systems to the HRV/ERV and then exhausted through a roof vent. Because this simple design utilizes strategic placement of supply and exhaust vents, this is an extremely common and cost effective design.

technician preparing to install ventilation

Preparing for a ventilation system installation

What do I need to consider when choosing a ventilation system?

The most important thing to keep in mind when purchasing a ventilation system is how often the air is able to enter and exit a room or the ‘air change rate.’

The math behind calculating air change rate is pretty simple, especially with a continuous balanced home ventilation system. Essentially you just need to know the size of the space you are trying to ventilate and how powerful the ventilation fans are in that space. Here’s the formula: ACPH=(Q*60)/Volume

ACPH = The number of air changes per hour.

Q = Fan volumetric flow rate. This is measured in cubic feet per minute (cfm) so the value is multiplied by 60 to convert to an air change rate per hour.

Volume = To calculate the volume of a room you first measure the length and width of the walls in feet, then measure the ceiling height in feet. Finally multiply these three numbers together and you have the volume of a room.

The greater the ACPH value, the better the ventilation is in a space.

An ACPH of between 6 to 8 is generally recommended for family living rooms, while a residential kitchen or laundry room might be a bit higher at 7 to 9. This resource created by Contracting Business is a useful tool for determining ACPH targets in different indoor spaces.

Look at how high the recommended ACPH is in a residential bedroom versus in a public smoking area!


Do I need a permit to install ventilation on my home?

Maybe, it depends on where you live and what type of ventilation system you’re installing. For example in Austin, Texas installation of a portable ventilation appliance is exempt from building permits. But in Portland, Oregon a mechanical permit is required for any work on ventilation systems.

Be sure to check on your local residential permit laws.

What are the costs of installing ventilation? This depends on a number of factors as well (labor costs, size of home, type of ventilation, etc.). The short answer – a simple bathroom fan can be as cheap as $35 while a roof vent plus labor can run over $650.


Steps for ventilation installation

What tools and parts will I need to install ventilation?

For our example, the tools required for the wall inlet vent are:
  • 4 inch rigid or flexible duct with insulation
  • 4 inch metal sleeve
  • Hooded inlet vent with animal grille
  • 4 inch hole saw
  • Caulk gun


The tools required for the roof exhaust vent are:
  • 4 inch rigid or flexible duct with insulation (exhaust length and width requirements)
  • 4 inch metal sleeve
  • Hooded exhaust vent with animal grille
  • Utility knife
  • Flat pry bar
  • 4 inch hole saw
  • Caulk gun


I’ve got everything – now what?

Now we can begin walking through the steps for installing a wall air inlet vent and an roof exhaust vent.


Steps for installing a wall inlet vent:

  • Drill a 4 inch hole into side wall. Be careful not to cut into any beams or electrical wires. Also, find a spot that is clear of any bushes or structures that may impact the ability of the ventilator to take in air. The inlet vent can also be placed on or near the roof if that is a more suitable position.
  • Insert the metal sleeve into the insulated duct. It may be easier to crimp the metal sleeve so that it fits inside the duct work.
  • Connect the duct to the side wall hole on one end and to the HRV/ERV on the other.
  • Add caulk to the inside perimeter of the hooded inlet vent and secure to building, covering the 4 inch hole.


Steps for installing a roof exhaust vent:

  • Determine where you want to place the vent on the top of the roof. It is important not to drill into any of the roof rafters.
  • Remove singles with a utility knife and pry bar before drilling a hole into roof.
  • Insert the metal sleeve into the insulated duct. It, again, may be easier to crimp the metal sleeve so that it fits inside the duct.
  • Connect the duct to the roof hole on one end and to the HRV/ERV on the other.
  • Add caulk to the inside perimeter of the hooded inlet vent and secure to building, covering the 4 inch hole.


How do I know that my ventilation system is working?

So, you’ve measured the ACPH in your space – you know the volume of air that your house is able to hold and you know the efficiency of the fresh air supply/exhaust fans – but is your ventilation system actually working?

The easiest way to measure supply and exhaust air flow is with a vane anemometer. These handheld machines allow you to pass the device over any vent so that you get a quick and accurate reading of air flow.

Contact a local home performance contractor for access to one of these or other air flow measuring devices.
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