The Importance of Make-Up Air
Airflow is just as important to a building as keeping the lights on and the water running. When it comes to water heaters, it’s an important safety issue as well.
Builders spend a lot of time and effort ensuring the elements don’t get in. More precisely, they do their best to route the elements where they want them to go: the rain goes down the rainspouts on the side of the building and the air goes out the exhaust fans of a ventilation system. While you might be entirely able to manage water, air is a much trickier element to control. Knowing how to control the air flow through a building keeps heating costs down, protects equipment from damage and keeps employees happy.
What is Make-Up Air?
Make-up air is the air needed to replace air lost through ventilation. Exhaust fans, water heaters and other equipment push out air from inside the building, causing negative air pressure. You’ve probably experienced this walking into a building where the door is hard to open and slams shut hard when it closes. Making sure the air pressure is properly balanced inside a building can keep an owner from making costly repairs and installing unnecessary equipment. More modern buildings have less natural gaps in their construction, so more thought needs to be put into how to keep the good air in and push the bad air out.
Negative air pressure affects the inside of a building in multiple ways. Negative air pressure can cause exhaust fans and hoods to work harder than they need to, which can make them more likely to break down or need replacement sooner. Cross-draft from air pressure can cause unwanted air to drift into unwelcome areas. Ever eaten in a restaurant at a hotel where you can strongly smell the chlorine from the pool even though it’s on a different floor? That’s a result of bad air pressure.
How Make-Up Air Affects Your Water Heater
Fuel-burning appliances like boilers and water heaters need a steady supply of air to work properly. If your water heater isn’t getting enough air, your water heater is not running at peak efficiency. It’s essentially gasping for air. At the very least, you’re wasting money burning more fuel for less heat. At worst, it could cause your water heater to backdraft into the building, causing much more serious issues—like a fire.
While negative air pressure needs to be evaluated in many operations, it’s a particular problem in restaurants. Restaurants can have even more challenges because of their extra equipment. Hoods, exhaust fans and other equipment made to push cooking fumes and other noxious gases out can tighten up the air pressure inside restaurants very quickly. Water heaters are also very important in restaurants because they affect everything from the product to the restrooms, plus they’re essential to helping restaurants comply with cleanliness codes. Ensuring your water heater is appropriately sized for your space can mean the difference between efficient operations of a profitable and code compliant restaurant and a restaurant you might have to sell.
Choosing the Right Water Heater
Commercial water heaters come in two major categories. Atmospheric water heaters, also known as standard water heaters are most common in older buildings. They are less expensive to install, less expensive to maintain and affordable to lease. Atmospheric water heaters often use the chimneys in older buildings or have separate flue venting. Their efficiency usually runs at around 85%.
These units do require some time and thought given to the air pressure in the room. Since these water heaters draw air from their surroundings, they are impacted by air pressure issues as they draw in air to heat the water. If that intake air is sparse, the water heater may end up gasping for the air that’s trying to escape through the exhaust chimney, causing backdraft and flame rollout—a serious problem.
High-efficiency (sealed combustion) water heaters extract as much heat as possible from the air before letting it out the combustion chamber. These units do not need make-up air because they are sealed and both the intake and exhaust are outside the building. These water heaters operate on the same principles as the atmospheric water heaters, but tend to have efficiencies in the mid- to high-90% range. These water heaters have fewer restrictions on where they can be installed as they are “sealed” from the elements. Because the technology is newer, the electronic components cost more for sealed combustion water heaters. They also need service from properly trained technicians, who can charge a bit of a premium when your system is down. (Just one reason renting a commercial water heater is a great option.) They’re more versatile than a standard water heater, but they still need to be put in a room with external walls or a roof so the venting can be constructed within the proper parameters.
With winter on its way, now’s the time to ensure you have the right water heater for your property. Improper (negative) air balance means more cold air will get into places you don’t want it. Make-up air rushes in when your building pushes out exhaust air, regardless of the source (hood fans, water heaters etc.). Careful consideration should be taken of your building’s air pressure and how it affects heating costs and equipment operation. Sources of humidity, like swimming pools, should be accounted for, as well as low pressure (or high air usage) areas like a commercial kitchen. Standard water heaters also affect airflow, but can be a good choice for older buildings as long as they can be located in areas with sufficient make-up air. High efficiency water heaters save money but need special considerations during installation and maintenance. Keeping the air and water balanced in your property goes beyond feng shui; it can mean saving thousands of dollars in energy costs this winter…plus, it’ll save you from serious safety hazards.