Dual-speed and multi-speed exhaust fans may sound like terms that can be used interchangeably, but there are distinct differences between the two. Let’s take a look at each.

Dual Speed Exhaust Fan

A dual-speed exhaust fan will have two speeds – a low speed and a high speed, which may be referred to as a boost speed. A dual-speed fan will operate continuously on the low speed, so it will always be running. In times when more ventilation is needed, it will boost to high speed. This can be accomplished via a wall switch, a motion sensor, or a humidity sensor.

Why does it need to operate continuously?

Building codes (known as ASHRAE 62.2) in the United States call for a continuously operating exhaust fan to ensure proper ventilation of the home, increasing the indoor air quality. A convenient way to solve this code is to have a dual-speed exhaust fan. This allows the builder to only have to install one fan that solves for both the bathroom ventilation and the continuous ventilation.

How It Works

A dual is typically installed in a main bathroom and has a very low sound level. In most cases, you might not even hear it running. This is important for a continuously running fan since it will be running all the time. When the bathroom is being used, the fan will switch to high speed. This might be triggered by a wall switch, a motion or humidity sensor/switch in the fan, or mounted on the wall. Once the room is unoccupied, the fan will return to the low speed.

Multi-Speed Exhaust Fans

Multi-speed exhaust fans are different from dual-speed exhaust fans in that they only have one operational speed that is selected from two or more options. On a multi-speed fan, there is a speed selector integrated into the fan where the end user chooses which speed is desired or is needed for the space. The speed can sometimes be set at a specific number, or it could be a variable speed dial that you increase or decrease.

Why Would You Use It?

Multi-speed fans are primarily used in new construction, where the ventilation amount might need to be adjusted on-site. When you see a CFM rating, this is a test lab certification. The testing labs do a great job of testing as close as they can to the real world, but it can sometimes be different. The ducting might be a little different; there is an extra bend, a different wall cap is being used, and so forth (see our blog on static pressure). A room might require 80 CFM of ventilation. If an 80 CFM exhaust fan was installed, but is only delivering 70 CFM, there is a problem, and more than likely the installer will need to remove the fan and replace it with a larger one. If you have a multi-speed exhaust fan, all the installer has to do is adjust the speed to the higher CFM, and all is well.

The main difference between a dual-speed fan and a multi-speed fan is the number of active speeds operating. A dual-speed fan will have two, while a multi-speed fan will have one. Both provide excellent ventilation and increase the indoor air quality of your home. To learn more about Air King’s dual speed and multi speed options, including the newly introduced SF5810 three-speed slim-mount exhaust fan, visit airkinglimited.com.

Do I need a Continuously Operating Exhaust Fan?

You might be getting ready to buy your first home, your dream home or even renovating your current home and the builder starts talking about a continuously operating exhaust fan. Your first reaction might be – what’s that? You’re not alone. For many homeowners exhaust fans are something that just comes with the house and not much thought is given to them. As home building has advanced, so has the need for ventilation within the home. Lets take a look at a few reasons you do need a continuously operating exhaust fan, starting with what is it.

What is a continuously operating exhaust fan?

The name is fairly descriptive. It is an exhaust fan that is continuously operating to remove moisture and contaminates from the home and providing multiple air exchanges per day (about one air exchange every 3 hours). To maximize their effectiveness they are typically installed in a central location of the home such as a family or living room. Because they are located in a main living space, they are required to have a very low sound level – less than the sound of your refrigerator.

Why do I need one?

The importance of a continuously operating exhaust fan will depend on the age and construction type of your home. In the paragraph above we talked about air exchanges. This is actually part of the national building code known as ASHRAE 62.2. The purpose of the code is to make sure the air inside the home does not become “stale” and in some cases dangerous. Newer homes are now being built to higher insulation standards, which make the home less susceptible to drafts. This is a good thing. What happens however is that because the house is so tight, it doesn’t allow for fresh air to come in or stale air to get out. This is where the exhaust fans come into play and in some cases a fresh air intake fan. In older homes, they generally have more air leaks and a continuously operating exhaust fan might not be as crucial. A benefit of using an exhaust fan is it puts the control in your hand instead of depending on drafts or other factors to determine the quality of your indoor air.

What should I look for?

As we mentioned, for these fans to be most effective they need to be installed in a centralized room such as a living room or family room. Choosing a fan with a low sound level is important. Exhaust fan sound levels are measured in sones with one sone being about the sound your refrigerator makes. The building code calls for a fan with a sound rating of one sone or below. The lower the sones, the quieter the fan is. A second consideration that is just as important is to make sure the fan has enough airflow. Airflow is measure in CFM or cubic feet per minute. Air King provides an easy calculator along with ASHRAE 62.2 information here. It is important that you have enough ventilation without over powering it and causing a negative pressure in the home (exhausting more air than is coming into the home). A final consideration is that you want an energy efficient fan. Since it will be running continuously, you don’t want it to be a burden on your electric bill. Air King offers a wide range of ENERGY STAR® certified models to fit almost any residential home need.

For more information about Air King exhaust fan solutions as well as continuously operating exhaust fans and ASHRAE 62.2 building codes, visit airkinglimited.com.

What is Air Exchanges Per Hour?

When talking about ventilation the term Air Exchanges Per Hour is probably going to come up, but what is it? The simple answer if how many times the air inside your home is replaced by either outside or filtered air per hour. Think of it this way – if you have a glass full of water and you pour it all out, then fill it back up with water you have exchanged the water in the glass one time. The same holds true with air but it is a little more difficult to see.

How is the air exchanged?

Air exchanges take place in one of three main ways.

Exhaust Fans: Exhaust fans are one of the most effective ways to exchange the air in your home. They take the stale indoor air and exhaust it to the outdoors allowing fresh air to replace it. National building codes now require a continuously running fan to be installed in all homes for this very reason.

HVAC system: Your HVAC system also helps provide air exchanges but there are some challenges with using this as the only method. The biggest one is that the system has to be running in order to provide air exchanges. You can set your system to just run the fan, but this is a very inefficient way to exchange air in your home. Another challenge is for this to be effective, the system needs to be drawing fresh air into the home or have filters installed that will take out the “bad” stuff. A good amount of HVAC systems do not draw fresh air in – you can check with your technician. As for the filters, most systems utilize a MERV 6 or MERV 8 filter. These are good for capturing dust and larger particles but when it comes to the stuff we are really trying to remove, they are not as effective. It is recommended that a MERV 13 or above be used, but not all HVAC systems can handle that (see our blog on Filters).

Natural exchange: It sounds so nice – Natural, but there are also some issues with this method. Most of the time this means opening a window or door and letting the air come in. If you have a nice breeze blowing on a moderate temperature day with good outdoor air quality (low pollen, smog, etc.) this is a good way to exchange the air. The big issue is you can’t control how much air is coming in or what is in the air. A second and significant issue it temperature, think Texas in the summer or Minnesota in the winter. Opening doors and windows probably is not an option.

Why are air exchanges important?

A key component to Indoor Air Quality is air exchanges. When we are not properly exchanging the air we allow all kings of contaminates to linger in the air. Think of a smoky bar room. Without any ventilation or air exchanges the smoke just lingers in the air. While hopefully our homes are not full of smoke, they are full of contaminates in the air caused by breathing, cooking, pets, and just general everyday living. Having a plan to continually remove these contaminates is key to better living. 

How many air exchanges per hour should take place?

This is where we come to the great debate. Home many air exchanges are needed, what is too little, what is too much. There is always a balance and as we learn more about our indoor air quality the numbers can change. As of this posting ASHRAE, who sets most of the building standards when it comes to indoor air quality recommends that a minimum of 0.35 air exchanges per hour occur in your home. Other organizations recommend up to 5 per hour. Our thought is that 5 per hour might be a bit extreme and will definitely have a negative effect on the efficiency of the home in that you have to condition all that air coming in to replace the air going out. With that being said, lets examine what 0.35 exchanges per hour looks like. For a 1,000 square foot home with 8-foot ceilings you have 8,000 cubic feet of space. Divide 8,000 by 60 (minutes) to get 133. Now times 133 by 0.35 to get 46.67. This is the amount of CFM you would need to provide the recommended air exchanges per hour. ASHRAE also provides a calculator that is a bit more involved to determine how much continuous ventilation your home needs. You can access the calculator on the Air King site by clicking here.

For more information about the indoor air quality of your home and how you can improve it, please read through the many articles we have written over the years. For information regarding Air King exhaust fan and fresh air intake solutions visit airkinglimited.com.

 

Is the Code Enough? Part 3

Over the past few blog posts we have been looking at code compliance and the difference between meeting the code and exceeding the code. In this post we are going to look at the ASHRAE 62.2 ventilation standard. In past blog posts we have described aspects of the standard such as local ventilation and continuous ventilation. In short ASHRAE 62.2 is a national ventilation code to promote air exchanges in your home to better the indoor air quality (IAQ). The basics of the code are to have an exhaust fan running continuously at a low speed, then using other fans throughout the house to take care of higher ventilation needs like cooking or when the shower is in use. Meeting the code means that you have an exhaust fan installed in a centrally located area of your home.

Great, that sounds fairly easy and for the most part it is. A popular way to solve for this is to install a two-speed exhaust fan in the bathroom. This is a fan that runs constantly on low speed at an almost silent sound level then when more ventilation is needed boosts to high speed. This can be done by a switch, humidity sensor, or motion sensor that is integrated into the fan.

So far so good; I think we have it covered. Code met, let’s move on to the next item. Here’s the thing (okay, you didn’t really think we would end it there did you?), while to the letter of the code, this installation might meet it, we need to look at it a little closer. First we need to think a little about how air travels and where contaminates are located in the home. Generally, the kitchen cooking area is going to be the location of the largest amount of contaminants generated in the home. If you are installing the continuous running exhaust fan in a bathroom, it is generally going to be on the other side of the home as the kitchen. This means that the exhaust is going to be pulling air from the kitchen throughout the home and through the living spaces. Not exactly an ideal solution. Here is another issue. What happens when the bathroom door is closed? Now you have either cut off or severely restricted the airflow. Let’s take it one step further. If the fan is installed in a master bathroom, that typically means two closed doors to navigate through.

Some installers will place the fan in the living room or a hallway. This is better as you won’t have to deal with the closed-door issue as much, but you are still drawing air that you want to exhaust through living areas. So I guess we are doomed. Can’t install it in the bathroom, can’t install it in a living area, where then?

There is a solution that takes all these issues into account. Place the continuous ventilation in the kitchen. There are reasons the kitchen is called the heart of the home. Typically the kitchen will be in a central location of the home or at least open to the rest of the home. This makes it a perfect location. There are now range hoods available that have multiple speeds. They have a continuous operation speed that will solve for, as the name states – continuous airflow. The sound level at this speed is barely detectable. When the cooktop is being used, they have higher speeds to take care of the additional airflow needed to properly ventilate while cooking. Now you have the ventilation placed at the source of one of the largest contaminators of the home. The added benefit is that the continuous speed will take care of the residual contaminants in the air after the cooking is done. While we would like to think everyone is properly using their range hood, we also know that is not always the case. These range hoods install the same as traditional range hoods, so if you are installing one anyway, why not solve two things at once. The only consideration is that they are going to cost more than an entry-level basic range hood. The counter to that is if you go the bathroom route, a two-speed exhaust fan is also going to cost more than a standard exhaust fan also. Another point is that you will also have a much quieter operating range hood.

When it comes to solving for ASHRAE 62.2 continuous ventilation, there are options. Some designed to meet the code, some designed to exceed the code. Hopefully this gives you some things to consider. For more information about continuous operation range hoods or ASHRAE 62.2 solutions visit www.airkinglimited.com