HVAC Closet Dimensions: Air Handler and Furnace Closet

Residential HVAC closet dimensions start at 26” wide and 40” high. Depth should be at least 32” to 42” depending on the HVAC equipment you’re installing.

Air handler closet dimensions: Minimum of 30”W x 49.5”H x 32”D for small units and 39”W x 60.5”H x 36”D.

Furnace closet dimensions: Minimum 26”W x 40”H x 42”D for small furnaces and 37”W x 46”H x 41”D for large furnaces.

Of course, those are minimum dimensions, and the closet can be much larger. But these AC, furnace or air handler closet sizes meet manufacturer recommendations for clearance space that allows enough airflow into and around the HVAC system.

Air Handler Closet Dimensions

Your air handler supports an AC or heat pump in distributing the cooled or heated air through the ductwork of your home.

They can be more compact than a furnace because they do not include a gas valve assembly and burners. For this reason, HVAC closet dimensions for an air handler can be quite small.

Keep in mind that these are minimum widths. Closets with much bigger dimensions are fine.

Air Handler Closet Dimensions:

CapacityMinimum WidthMinimum DepthMinimum Height
1.5 Ton30 inches32 inches49.5 inches
2 Ton30.5 inches33.5 inches51 inches
2.5 Ton32 inches34 inches51.5 inches
3 Ton34 inches35 inches55 inches
3.5 Ton35.5 inches35.5 inches59 inches
4 Ton36.5 inches35.5 inches62 inches
5 Ton39 inches36 inches60.5 inches

Air handlers are discussed in terms of tons because it refers to the size of the outdoor unit they support and the rating of the matching indoor coil found inside the air handler.

Furnace Closet Dimensions

Residential furnace closets have to be a little larger than air handler closets because furnaces are larger than air handlers, it needs fresh combustion air and a furnace gets hot – so it needs more clearance room on sides and top.

Furnace Closet Dimensions:

Btu of FurnaceMinimum WidthMinimum DepthMinimum Height
40,000 Btu26 inches42  inches40  inches
50,000 Btu28 inches41 inches41  inches
60,000 Btu29 inches41 inches42  inches
70,000 Btu30 inches41 inches41  inches
80,000 Btu31 inches41 inches42  inches
100,000 Btu33 inches41 inches42  inches
120,000 Btu37 inches41 inches43  inches
140,000 Btu37 inches41 inches46  inches

HVAC Closet Door

There are a couple of considerations when discussing an HVAC closet door.

First, it is essential that an HVAC closet door have a louver front on it to allow for air flow. This is especially true of a furnace closet. The louver allows for cool air into the space to prevent the furnace or air handler from overheating. And if the equipment is a furnace, the louvers or slates allow fresh air for combustion to get to the furnace.

Secondly, the HVAC room door should be at least 2” wider than the furnace or air handler – 4” or more is better. This allows you or an HVAC technician to access the equipment more easily and to service it when necessary.

Did you know? Some HVAC closets should not have doors. This is because furnaces in some manufactured homes do not have return air ducts, just supply ductwork.

So, those homes should not have an HVAC closet door, even one with a louver. Return air is pulled directly into the furnace, and a door will block the airflow.


How much space is needed for an AC closet?

An AC closet for the smallest air handler needs to be a minimum of 30 inches wide and 50” high. Depth should be at least 32 inches. That’s for a 1.5 ton system.

The largest system, a 5 ton air handler, needs a minimum space 39” wide and about 60” high.

If the AC runs with a furnace, then the AC closet can be a little smaller: 26” wide and 40” high for a 40,000 BTU furnace up to 37” wide and 46” for a 140,000 BTU furnace.

Can you enclose a furnace in a closet?

Yes you can enclose a furnace in a closet. But the closet must have the minimum clearance required by the manufacturer. This minimum space is usually 26 to 40 inches wide, 40 to 60 inches high and 30 to 40 inches deep.

Secondly, the door should have an area with louver slats – or vented opening – to allow for excess heat to escape and for fresh air to flow into the closet. This ventilation helps to prevent the furnace space from overheating.

Does a furnace closet need ventilation?

Yes it does. The best way to ensure ventilation is to install a door with a louver or slats to allow for airflow. Or you can simply remove the door to allow unhindered ventilation and airflow. 

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.
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