Most people don’t realize good airflow is just as essential to building safety as properly installed electricity and plumbing. Make-up air is a critical safety issue when it comes to keeping your water heater functioning properly, too.
Building engineers and maintenance workers spend a lot of time and effort ensuring the elements can’t get into buildings where they don’t belong. 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 managing the flow of water seems pretty straightforward, air is a much trickier element to control, but knowing how to direct the airflow through a building keeps heating costs down, protects equipment from damage, and keeps employees and residents safe and happy!
What is Make-Up Air?
The answer is simple: make-up air, or replacement air, is the new fresh air required to replace the air used by appliances or pushed out of a building through ventilation systems. Exhaust fans, water heaters, and other equipment pump old air out continuously, which can cause negative air pressure, or “depressurization,” in the building’s interior if that air isn’t properly replenished.
You’ve probably experienced this before when walking into a building where the door is hard to open and slams shut when it closes – this is a sure sign of negative air pressure. Replenishing used air is essential for keeping the inside air clean, filtered, and safe to breathe, but ensuring the air pressure is in proper balance with adequate make-up air also needs to be part of the equation.
Most modern buildings have very few, if any, natural gaps in their construction, which means that air doesn’t quickly and naturally replace itself like it often does in older buildings. This is called the “natural infiltration rate of the building.” However, having negative pressure inside the building can lead your appliances to literally “gasp” for the air they need to work properly, leading to costly repairs, extra unnecessary equipment, and even backdrafts and fires.
Negative air pressure affects the indoor air quality of a building in multiple ways. It can cause exhaust fans and hoods to work harder than needed, making them more likely to break down or need replacement sooner. Cross-drafts from air pressure can also cause unwanted contaminated air to drift into unwelcome areas.
Have you ever eaten in a hotel dining room where you can strongly smell the chlorine from the pool even though it’s on a different floor? That’s a result of an imbalanced ventilation system. Without enough make-up air, appliances desperate for air can accidentally pull too much air in from wherever they can get it – typically from the exhaust vent or chimney, which also pulls exhaust gasses back in with it, putting you at risk of fires or harmful carbon monoxide poisoning.
How Make-Up Air Affects Your Water Heater
Fuel-burning appliances like boilers and water heaters need a steady air supply to work correctly. If your water heater isn’t getting enough air, your water heater isn’t running at peak efficiency. 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 and start a fire or even, in the most extreme cases, explode.
While negative air pressure needs to be evaluated any time it happens, it’s a particular problem in restaurants. Extra equipment like kitchen ventilation hoods, exhaust fans, and air pumps that handle cooking fumes and other noxious gases can quickly tighten the air pressure inside a restaurant. On top of that, commercial water heaters, which are vital for restaurants to ensure that they have adequate sanitation, hygiene, and cooking operations, use even more air to run correctly. This means that if the kitchen is causing too much negative air pressure, the water heater won’t have what it needs, which puts you, your staff, and your customers in danger!
Ensuring your commercial water heater is appropriately sized for your space can mean the difference between running an efficient, profitable, and code-compliant restaurant and running a restaurant you end up having to sell.
Choosing the Right Water Heater
Commercial water heaters come in two major categories: Atmospheric and High-Efficiency.
Atmospheric Water Heaters
Also known as “standard water heaters,” these are most common in older buildings. They use a thermometer to monitor hot water temperature inside the tank. When the temperature drops too low, an automatic spark ignites a flame in an open combustion chamber below the tank to heat the water. The flame draws on air from the environment (atmospheric air) to burn, and the gases produced are vented outside, often using the chimney in an older building or a separately installed flue vent.
Because atmospheric units use the standing air in the room, they require that you put some time and thought into making sure there’s enough make-up air to replace it. It also means they are significantly impacted by any air pressure issues in the building. If that intake air is sparse, the water heater may gasp for air and try to pull more air in through the exhaust chimney as the gasses are vented out, causing backdraft and flame rollout—a serious problem.
The good news is that because they can use any surrounding air as fuel, they can be installed in almost any interior space, as long as there’s enough make-up air, and they don’t necessarily need to be closer to an outside wall. This means they are less expensive to install, less costly to maintain, and affordable to rent or lease. Their efficiency usually runs at around 80-85%, and around 15% of the heat generated is lost through ventilation.
However, atmospheric water heaters are also facing extinction in the somewhat near future. New regulations have recently been set by the Department of Energy (DOE) that will affect the production of commercial water heaters starting on October 6, 2026, while the new residential water heater regulations will go into effect on May 6, 2029. Essentially, water heater manufacturers will no longer be able to produce atmospheric gas storage water heaters after those cutoff dates; they will only be allowed production of high-efficiency, sealed-combustion water heaters that have a minimum thermal efficiency of 95%.
High-Efficiency Water Heaters
High-efficiency (sealed combustion) water heaters extract as much heat as possible from the combustion gasses before letting them out of the combustion chamber. These units do not need to be installed alongside a make-up air unit because they are sealed, with both the intake and exhaust air pipes leading outside the building. These water heaters operate on similar principles as the atmospheric water heaters by transferring the heat from the hot exhaust gasses to the water inside the tank, but they tend to have 95-98% range efficiencies because their internal design maximizes their heat transfer capability.
High-efficiency water heaters have fewer restrictions on where they can be installed as they are “sealed” from the elements. However, they must still be put in a room with external walls or a roof to construct the venting within the proper parameters.
Additionally, because the technology is more advanced, the electronic components cost more for a sealed combustion water heating system. They also need service from properly trained technicians, who can charge a bit of a premium when your system is down. That’s just one reason renting a commercial water heater is a great option!
So Do I Need Make-Up Air?
Sometimes, you can tell if your building is stuck in a negative air pressure system. For instance, you may notice that your doors and windows let in a big ‘whoosh!’ when opened, or there may be dust, moisture, haze, odors, or fumes lingering in your restaurant’s dining areas. However, more often than not, you won’t know there’s an issue unless something goes wrong.
The best way to ensure your air system is “up to snuff” is to have it checked by a licensed professional HVAC technician or to have your specific appliances examined by approved repair or installation professionals.
Don’t Forget: The qualified service technicians at Reliable Water Services are available 24/7 to help ensure that your commercial water heater is working properly, so don’t hesitate to reach out if you have specific questions or suspect there may be a problem!
OK, I Need Make-Up Air. What Should I Do?
In most cases, there are two main options that commercial building owners can choose from when implementing a make-up air solution.
Standard Ventilation
The simplest and least expensive way to add additional air “input” into your building pressure system is to install standard ventilation fans into your roof or walls. Air supply fans bring in outdoor air “as is,” meaning they’re a great solution in mild climates where the air coming in won’t be hard to heat or cool to a comfortable level. However, it also means that the environmental conditions outside can be pulled inside, which could make more work for your building’s HVAC and filtration system.
Make-Up Air Unit
This type of HVAC solution pulls fresh air from the outside and then pushes filtered and tempered air into the building’s air system. Make-up air units typically:
- are more expensive to install
- require specialized service professionals to install and repair
- take up more space in your building
- save on energy consumption
- can help extend the longevity of all of your air-consuming appliances
- are a much better option for buildings in climates with hot summers or cold winters
Make-up air systems are the best choices for businesses like food service establishments, pharmaceutical manufacturing plants, and healthcare facilities, which require a high quality of air and tend to have more air vented outside than usual.
Being Prepared Will Keep Things Easy Breezy!
You know what they say: the best time to be prepared is yesterday, but the second best time is today! With winter never more than a few short seasons away, now is the time to ensure you have the right water heater for your property.
Ensuring your water heater is functioning well is one of the best ways to detect an imbalanced ventilation system. After all, if the water heater isn’t getting enough air, chances are good that your other appliances aren’t either. Balancing your property’s air and water systems can save thousands of dollars in energy costs. Plus, it’ll save you from serious safety hazards. Now that’s a win-win!
Are you interested in renting your commercial water heater? Contact Reliable Water Services today!
