Thread: Gas Hot Water Heater Closet is VERY cold

I am hoping that you folks can help me with this issue.

We are in our new home for our first winter/cold spell. The gas water heater closet is located inside the house. The closet is vented with 2 pipes through the ceiling into the attic. 1 ends approx 12" off the floor and the other ends 12" from the ceiling. I understand this to be code.

The problem is that the pipes are pulling cold air into the closet from the attic. This morning the outside temperature was 24 degrees and it was 36 degrees in the closet. I am afraid that when it gets even colder outside that the water lines in the closet will freeze.

I have temporarily sealed the door (with a towel) so that the cold air is no longer coming into the house, but I am still concerned about the temperature inside the water heater closet.

Is this normal? If not, how can I correct this? Thanks in advance!

That's because the builder took the 'cheap way out' - a direct vent water heater would solve that problem.

Here is one example of direct vent water heaters, every manufacturer probably makes them:
- Direct Vent | Bradford White Water Heaters. Built to be the best.

With direct venting, the cold air from outside provides combustion air for the water heater (and stays inside the water heater) and the combustion byproducts vent back out to the cold outdoors.

No more cold air in the water heater closet ...

Weather strip the closet door is about your only option unless you want to replace the heater with a more efficient one. You can also insulate the water lines but do not place combustible insulation closer than 6 inches to the vent hood at the top of the heater. The heater itself and water lines near the top of the heater will not freeze as long as the heater is in operation.

Thanks for the replies. I still don't understand why having the closet vented to code would bring in so much cold air, it just doesn't make any sense to me. I will weatherstrip the door and hope it doesn't freeze. Thanks again!

Originally Posted by Chuck H

Thanks for the replies. I still don't understand why having the closet vented to code would bring in so much cold air, it just doesn't make any sense to me. I will weatherstrip the door and hope it doesn't freeze. Thanks again!

I'm guessing that the two pipes are around 8" diameter pipes? You basically have a 16" round hole in the ceiling of the closet that is sucking in the air. If you think about it like this, I bet it makes a little more sense...

Originally Posted by Scott Patterson

I'm guessing that the two pipes are around 8" diameter pipes? You basically have a 16" round hole in the ceiling of the closet that is sucking in the air. If you think about it like this, I bet it makes a little more sense...

OH I understand that, what I don't understand is why code requires a configuration that does that. I would think there would be a better way. And yes I understand that a different style of water heater would solve the problem, but SURELY there is a better method for what I have then the current code.

We spend all the time,energy and money to make our homes "air tight" then, as you said, create 16" of hole in the ceiling to let outside air in, because that is the code. There has to be a better way.

Originally Posted by Chuck H

OH I understand that, what I don't understand is why code requires a configuration that does that. I would think there would be a better way. And yes I understand that a different style of water heater would solve the problem, but SURELY there is a better method for what I have then the current code.

We spend all the time,energy and money to make our homes "air tight" then, as you said, create 16" of hole in the ceiling to let outside air in, because that is the code. There has to be a better way.

It is so the gas appliance will have the proper amount of combustion make-up air. If it was an electric or the direct vent type water heater you would not need the "high/low" vent. I would be considering an electric water heater to take care of this problem. Yes, it is a building code but it is really a requirement that is created with any conventional gas fired appliance that is located within an enclosed area.

Another option to the high/low vent would be to put a louvered door on the closet as long as the openings in the door louvers are are sized properly and are providing the proper amount of make-up air. Then you could seal off the two vents in the closet..

Energy savings is great but not if you die in the process. Without combustion air, the water heater begins producing carbon monoxide.
Yes, there are better ways:

• Design the house so that the heater is outside the thermal envelope.
• Use a a sealed combustion appliance that pipes the combustion air directly into the appliance.
• Use an electric heater.

If you weather strip the door so that it is leaks no air the amount of energy loss will be negligible.

Originally Posted by Scott Patterson

It is so the gas appliance will have the proper amount of combustion make-up air. If it was an electric or the direct vent type water heater you would not need the "high/low" vent. I would be considering an electric water heater to take care of this problem. Yes, it is a building code but it is really a requirement that is created with any conventional gas fired appliance that is located within an enclosed area.

Another option to the high/low vent would be to put a louvered door on the closet as long as the openings in the door louvers are are sized properly and are providing the proper amount of make-up air. Then you could seal off the two vents in the closet..

I do understand the need for combustible air for the water heater.

Scott - How would I determine the amount of opening that the louvered door would need? Also the back wall of the closet is the garage wall. Could I install a vent in that wall and pull the combustible air from the garage instead of the house?

Originally Posted by Chuck H

I do understand the need for combustible air for the water heater.

Scott - How would I determine the amount of opening that the louvered door would need? Also the back wall of the closet is the garage wall. Could I install a vent in that wall and pull the combustible air from the garage instead of the house?

I'm not Scott, But DO NOT pull air from the garage! You will introduce more CO into the house as well as breaching the fire separation.

Remember there are other requirements if you plan on installing a louvered door.
Such as the door must not open into a confined space such as a laundry room, bedroom, etc.
Also, remember you will be continually pulling combustion and dilution air from the house and sending it up the vent stack of the water heater, not a very energy efficient method either.

I have included a link the the appropriate code section below;


FIGURE G2407.5.3 (304.5.3) ALL AIR FROM INSIDE THE BUILDING (see Section G2407.5.3) G2407.5.3.1 (304.5.3.1) Combining spaces on the same story.
Each opening shall have a minimum free area of 1 square inch per 1,000 Btu/h (2,200 mm²/kW) of the total input rating of all appliances in the space, but not less than 100 square inches (0.06 m²). One opening shall commence within 12 inches (305 mm) of the top and one opening shall commence within 12 inches (305 mm) of the bottom of the enclosure. The minimum dimension of air openings shall be not less than 3 inches (76 mm).

G2407.5 (304.5) Indoor combustion air.
The required volume of indoor air shall be determined in accordance with Section G2407.5.1 or G2407.5.2, except that where the air infiltration rate is known to be less than 0.40 air changes per hour (ACH), Section G2407.5.2 shall be used. The total required volume shall be the sum of the required volume calculated for all appliances located within the space. Rooms communicating directly with the space in which the appliances are installed through openings not furnished with doors, and through combustion air openings sized and located in accordance with Section G2407.5.3, are considered to be part of the required volume.

G2407.5.1 (304.5.1) Standard method.
The minimum required volume shall be 50 cubic feet per 1,000 Btu/h (4.8 m³/kW). G2407.5.2 (304.5.2) Known air-infiltration-rate method.
Where the air infiltration rate of a structure is known, the minimum required volume shall be determined as follows:

For appliances other than fan assisted, calculate volume using Equation 24-1.

(Equation 24-1)

For fan-assisted appliances, calculate volume using Equation 24-2.

(Equation 24-2)

where:

Iother	=	All appliances other than fan assisted (input in Btu/h).
Ifan	=	Fan-assisted appliance (input in Btu/h).
ACH	=	Air change per hour (percent of volume of space exchanged per hour, expressed as a decimal).

For purposes of this calculation, an infiltration rate greater than 0.60 ACH shall not be used in Equations 24-1 and 24-2.

Chapter 24 - Fuel Gas