Gas Fireplace

We all know the importance of a supply of air for gas-fuelled appliances, including gas fireplaces, fifty-fifty if the reason for this render is non fully understood. If you wait into the building code regulations regarding this, yous come up across two price: makeup air together with combustion air.

These are really referring to 2 different things, as well as fifty-fifty though they are both mentioned inward the chapter on gas fuel, only 1 of them is required for gas fireplaces. Let’second clarify this further.

Gas fireplaces do not take makeup air. Makeup air is the air brought into the home to supervene upon air removed past exhaust systems. Gas fireplaces do, notwithstanding, take a render of air. This is known as combustion air, as well as it is separated from makeup air inwards when, how, too why it is brought inward.

Makeup Air Replaces Exhausted Air

Makeup air is necessary to fill the negative pressure level created when appliances with exhaust systems, such equally range hoods, bath fans, in addition to dryers, actively remove air from the family’sec interior.

On their own, gas fireplaces don’t call for makeup air.

However, according to Section G2407.iv of the International Residential Code (IRC), exhaust fans besides every bit appliances such every bit apparel dryers too kitchen ventilation systems should not interfere amongst appliances fuelled past gas, like gas fireplaces.

So, if exhaust systems are present inwards the same room every bit a gas fireplace, regulations require makeup air to live provided to avoid interference.

Interference tin manifest inwards two main ways.

Firstly, if in that location is no makeup air, the exhaust systems tin can make negative force per unit area in the room, which pulls air back out of the gas fireplace vents to attempt together with residual the pressure.

This is called backdrafting too it is really unsafe when it occurs alongside appliances that generate harmful combustion byproducts that are supposed to live removed from the home through the vents/chimneys.

Secondly, if the combustion air furnish is non direct fed into the appliance simply is, instead, delivered more by and large into the room inwards which the gas fireplace is installed, so the combustion air will live prevented from entering the appliance as well as serving its purpose.

Instead, it will act every bit makeup air to residue the uneven force per unit area organization.

But gas fireplaces require this combustion air, which is what we volition be discussing before long.

Makeup Air Can Become Combustion Air

If yous have a device that is exhausting air from the room containing the gas fireplace, then the air pulled inward from outside past the makeup air unit tin then live drawn into the appliance’s vicinity together with live used every bit combustion air.

However, yous tin can involve makeup air without having a gas fireplace in addition to y'all tin can accept a gas fireplace without a makeup air unit if in that location are no exhaust systems nearby. This is why the air supplies are given different price as well as are differentiated inwards terms of their part.

Gas Fireplaces Need Combustion Air

For combustion to fall out, three things are needed: fuel, estrus, together with air.

While makeup air replaces the air expelled from exhaust vents, combustion air is supplied specifically for the combustion of fossil fuels to be carried out.

The difference between complete as well as incomplete combustion, 1.e., safe and efficient combustion as well as dangerous together with inefficient combustion, is the sum of oxygen available for the reaction.

If combustion air is not supplied, the gas produced by burning fuel is carbon monoxide as opposed to carbon dioxide. You don’t call for me to tell you lot which of these 2 gases is more toxic!

In addition, incomplete combustion produces less heat, which is the use of a gas fireplace. This is what makes gas fireplaces inefficient when combustion air is lacking.

One other negative effect of a lack of combustion air is backdrafting.

Yes, combustion air is needed to ensure a proper provide of oxygen for burning the gas, but the fact that the appliance draws air inward means that the area about the fireplace tin endure from negative air force per unit area, which results in backdrafting.

In a way, this means that combustion air acts as makeup air for the fireplace, only technically, makeup air, which is associated amongst exhaust systems, is not required by gas fireplaces.

Sources of Combustion Air

Combustion air tin can live supplied from indoors, outdoors, or a combination of the 2.

According to Section G2407.five of the IRC, indoor combustion air tin live provided from rooms that are adjacent or otherwise connected to the room containing the gas fireplace.

The connections must live permanent (i.e., they cannot be coverable by doors) or they tin live peculiarly installed combustion air openings.

As stated by Section G2407.half-dozen of the IRC, outdoor combustion air is provided through three-inch-plus openings (vents) or ducts between the outdoors in addition to the infinite containing the gas fireplace.

Air pulled inward from a ventilated attic is too considered to live outdoor combustion air because of the complimentary communication between the attic as well as the outdoors.

Indoor as well as outdoor air tin too live used in combination to provide combustion air every bit long as they fulfill the IRC regulations every bit per Section G2407.7.

How Much?

Indoor combustion air should be provided at a minimum volume of fifty cubic feet per chiliad Btu/h (British thermal unit of measurement per hr) of the gas fireplace input rating.

Alternatively, or if the air infiltration charge per unit is confirmed to be less than 0.twoscore air changes per 60 minutes, the required volume can be determined using specific calculations.

You tin come across these calculations in the IRC or inwards my article: Furnace