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5 Signs Your House Needs (more) Make-up Air

Whether you have a very air-tight house or a large exhaust system, then you might need more makeup air than you were expecting or was recommended to you. Here are five signs that you need to add or increase the amount of makeup air provided.

Makeup air should be added or increased if the following are noted:
  • Struggling exhaust systems
  • Widespread drafts
  • Gurgling drains
  • Sewer smells
  • Inexplicably high utility bills

1. Exhaust Systems Are Struggling

Poor performance by exhaust systems isn’t always caused by mechanical faults or aging.

Exhaust systems function by moving air from an indoor location to the outdoors. Therefore, for them to perform optimally, there needs to be balanced air pressure in the room. 

If your entire house or parts of the house lack sufficient makeup air, one of the things you will notice is that any exhaust systems in affected locations do not function optimally.

This is because the lack of replacement air leads to negative air pressure and this, in turn, limits how much air the device can pull from the room. 

Negative air pressure, air enters the room and leaves through exhaust

For instance, a 1000 CFM (cubic feet per minute) range hood in a room with poor makeup air might function at the capacity of barely 600 CFM hood. 

Ducted ventilation devices like range hoods and bathroom fans can only provide the desired result if there is both removal of “old” air and the inflow of “new” air.

If air isn’t drawn in to make up for the air that has been exhausted, the unit would have to work harder to ventilate the space because it would be working to pull against a vacuum.

As the air cannot be removed well, the contaminants that you are trying to get rid of would linger in the house to cause all the issues you are trying to avoid in the first place.

Here are some of the effects of insufficient makeup air on exhaust systems:

  • Grease buildup on kitchen surfaces even while running the range hood.
  • Range hood takes too long or is unable to completely remove smoke from the cooking area.
  • Bathroom fans take too long to ventilate and expel steam from the room.
  • Poor indoor air quality.

Household devices like vented dryers also depend on ambient air to function, and low makeup air means that they would be unable to draw in enough air from the room, causing them to take longer to perform dry your clothes.

2. Widespread Drafts

The absence of makeup air in a space creates a negative air pressure system in the room. This causes air to be drawn in from surrounding areas to balance out the air pressure in the room. 

Since there is no established route through which makeup can enter the space, air would be drawn in from openings, cracks, and gaps in surrounding areas. 

If any of the openings lead to the outdoors, or unconditioned parts of the house, it can lead to drafts. Air can even be pulled in from under your baseboards.  

The intensity of the draft would be influenced by the size of the room, how much air is expelled, and the size and number of spaces through which air can pass. 

Homes with powerful range hoods or houses that use a lot of exhaust devices would most likely experience worse drafts than those that do not.

In addition, if a house has low-quality weatherproofing, then there will be more sources of drafts.   

So, if you often notice cool air coming in through the gap underneath your doors and windows or you experience unexplained drafts in your house, especially while running your exhaust system, it might be an indication that your house does not have sufficient makeup air. 

3. Gurgling Drains

One of the often-overlooked signs of insufficient makeup air in a house is noisy drains.  

Whenever there is a negative air pressure, air would be drawn from every available place to create a balance in the air pressure. We have spoken about air being pulled through cracks and gaps, but did you know that it can also be pulled from your drains?

It’s easy to associate drains with water-filled pipes, but the truth is that most of your plumbing is filled with air. This is vital to its ability to drain and function properly.

Air is mostly drawn from drains if there is a pressure imbalance in your entire house or if the room with the issue is close to a drain(s). 

Air is mostly drawn from drains if there is a pressure imbalance in your entire house

The noise released can range from being barely noticeable to being annoyingly loud. 

If a large amount of air is pulled from the drains, it would most likely result in loud gurgling noises.

Sometimes, the gurgling can be accompanied by backflow, which is when the waste and water that is supposed to be going down the drain to the waste pipe, is suctioned back up through the drain.

4. Bad Smells in the House

Air being pulled up from the drains is not just going to make an annoying sound. The air is coming from your plumbing system, so it will contain sewer gasses.

Sewer gas can be pulled from your toilet, obviously, but also from your sinks, basins, showers, bathtubs, dishwashers, and washing machines.

Once the foul-smelling air enters a room, the stench would eventually move to other parts of the house, causing your whole home to smell funky. Not only is this unpleasant but it can also be bad for your health.

Additionally, range hoods and bathroom fans usually remove odors associated with cooking and toilets. If they are struggling to exhaust air, then this can add to the smell in the house.

Air can also be drawn from chimneys or vents responsible for expelling smoke and dangerous gasses out of your home. This can expose you and other people living in the house to increased levels of toxins like carbon monoxide. 

5. Utility Bills Are Inexplicably Higher

If it isn’t addressed appropriately, the imbalanced air pressure caused by insufficient makeup air can result in an increase in utility expenses.

Kitchen range hoods and bathroom exhaust fans that are functioning sub-optimally are going to need to stay on for longer, which requires more electricity.

Old woman checking her bills while the range hood is switched on

Of course, you may end up just turning these devices off before they have done their jobs, but something like a humidity-sensing bathroom fan would just stay on until all the steam was removed. If you leave the house before your fan goes off, you might not notice it is running longer than it should.

If your clothes come out of the dryer still damp, then you are likely to throw them in for another cycle. Even if it’s just a short cycle, it’s more electricity or gas than you would use if there was sufficient makeup air entering the house.

Another way that a lack of makeup air can increase your utility bills unexpectedly is by drawing in unconditioned air through gaps and cracks.

If your house’s environment is controlled with an HVAC system, or even if you are just running a wall-mounted AC or a portable heater, then the entrance of unconditioned air makes the system work harder to maintain your desired or pre-set temperature.

How much energy is required to achieve this would be determined by the difference in temperature between the indoors and outdoors as well as how long the exhaust system is left to run.


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