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Furnace Fresh Air Intake: What You Should Know

Furnace Fresh Air Intake: What You Should Know

Wondering why your indoor air feels stuffy? It may be time to re-assess your furnace combustion system. Request a free quote for a fresh air intake installation from an HVAC technician.

Furnaces need to refurbish the indoor air with outside air to maintain a fresh, healthy, and clean atmosphere inside your house. When fresh air vents are installed in your home they ensure that the furnace combustion system doesn’t malfunction which might push inside impure air, causing a number of illnesses and damage to your property.

Let’s take a deeper look into why installing fresh air intakes and vents is important and what types of intake systems are available for your furnace.

Importance of Fresh Air Intakes 

A fresh air intake sends air to your furnace and water heater through a duct. Newer homes today use a direct air combustion pipe connected to the appliance. 

For a furnace, gas appliance, and water heater, having a dedicated air intake can make all the difference for air combustion purposes. You need the air in all your rooms to stay clean at all times since the lack of combustion can cause your appliance to break down and respiratory illnesses for family members.

Additionally, they keep air pollutants at bay that infiltrate from cracks, crawl spaces, and exposed areas of your home. 

clean air inside home
Source: Max Vakhtbovych

Where Intakes Live in Your Home

Gas Appliances

Having a dedicated air intake hooked up to your gas pipeline will ensure there’s no unnecessary heat buildup and that air is regularly ventilated in your kitchen. This air is usually passed out through the chimney.


Your home furnace is legally mandated to have a fresh air intake system in keeping with health standards administered by the City of Edmonton. If your air intake is clogged, it can lead to carbon monoxide forming in your atmosphere which can be lethal. A fresh air intake provides your furnace with clean air instead of your furnace burning indoor oxygen to reproduce fresh air. Hence, if your furnace air intake goes without periodic maintenance, you will notice the quality of indoor air deteriorates.

Water Heater

The higher the consumption, the larger the presence of air in the room where water heaters are used. Air intakes of gas-powered water heaters are typically hooked up to the furnace where the air passes through a vertical and upward vent.

If you find that your water heater is in a room where air combustion is inadequate or tight, consider installing a direct vent where the exhaust gases are vented outside via the direct ducted air intake.

Types of Fresh Air Intake Systems for Furnaces

The furnace is your main HVAC system to keep the air clean within your house. A gas furnace is known to use 30 to 40 feet of air for every unit of gas utilized across the house. Since the furnace ensures the air inside your rooms stays clear of dust and air-borne bacteria, it needs a dedicated and robust ducted air intake for direct venting.

Here are the two most popular types of furnace air intakes installed.

Conventional Furnaces

Standard or conventional furnaces extract air from the room they’re located in and exchange it with a direct ducted intake for venting. However, this type of venting system leads to air being sucked from crawlspaces and corners laced with contaminants of the room building negative air pressure. The interior surfaces and furniture will decay quickly if you continue using this type of air intake system for a long time. 

High-Efficiency Furnaces 

High-efficiency furnaces have a dedicated pipeline that runs directly from the exterior vent into the furnace’s combustion chamber. A lot of homeowners shy away from installing exterior vents during winter as they feel they will freeze. However, this isn’t true as the vents are critical to keeping your furnace functioning properly. 

Since these furnaces draw air from outside, they can also bring excess moisture into your house. However, with a sound winter-proof installation, you can prevent your furnace from breaking down.

Does Furnace Bring Fresh Air from Outside?

Fresh air could also be called ‘replacement air’ as that is exactly what it is all about. Houses have to maintain a slightly positive pressure in them. This is so that whenever you run a bathroom fan, dryer, or range vent, the air you are exhausting gets replaced with ‘fresh air’. 

Fresh air is usually tied directly into your ducts and is drawn into the home by the furnace fan or just due to the negative pressure that exhausting systems create. If a house doesn’t have a fresh air then exhausting systems in your house will create a negative pressure that will start to draw in air from outside through the weakest points in the home’s Vapor barrier. This creates moisture problems.

HRVs are fresh air devices that use exhausting air to help heat incoming air and keep some of that heated air from being wasted, as well as maintain that interior pressure.

All said and done, fresh air is air for breathing and combustion air is air for burning.

Contact Always Plumbing and Heating for a consultation on the best fresh air intake system for your residence.

Have Questions About Fresh Air Intakes?

How often should combustion air and HRV systems (heat recover ventilation fresh air intake) run?

Combustion air should run whenever a gas appliance is operating. This should be set up on installation as it will be an automatic process. On the other hand, fresh air intakes, such as HRV, should be run more often in the winter to control humidity and prevent attic rain.

How can I get combustion air and HRV systems without losing heat?

Most combustion airs are equipped with a combustion air pot. This created an air pocket that prevents the continuous flow of air into your house. Most new gas-fired appliances have their own combustion air supply. On the other hand, in order to prevent heat loss when operating your HRV system, you should have a timer installed that senses humidity levels so the system only kicks in when it is necessary. Also, you should ensure your attic is insulated up to the building code. You will need to contact a roofing or general contractor for this part. 

How do you know if your combustion air is clogged? What about your HRV?

If there is a clog in the system, your gas appliances will not operate properly. Contact a plumbing contractor with a professional gasfitter to complete the job safely. Alternatively, if your HRV system is clogged, the system may start making noises and you may notice poor air quality in your home. When the filters are clogged or dirty, the air coming back into the home is polluted. Change your HRV filters twice per year, and clean them every 2 months for optimal performance. Also, check your HRV intake and outtakes and ensure they are not blocked with leaves or snow. Remove any obstructions. 

How much does it cost to install a combustion air intake? 

This depends on what the combustion air is feeding and the size that is required. You will run into this situation in the event you are building a new home or are adding gas appliances in place of electric. Just the air intake costs roughly $350-$1000, which doesn’t include the costs of gas lines and permits. 

How much combustion air and fresh air does your house need in the winter?

The amount of combustion air is determined by your use of gas appliances (including your furnace). You will use more combustion air in colder weather. The amount of fresh air will depend on the operation and cycling of your HRV system. You can adjust this when you have a humidity detector installed, which you can set to kick in when the attic reaches a certain humidity level. 

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