Thread: Ventilation requirements for natural gas water heater

I am replacing a louvered door with a standard 6 panel door for a closet that contains a natural gas hot water heater. The louvered door is the only source of incoming air for the room. I am planning to install a vent in the wall to allow air to enter the closet (which is roughly 4' x 10') but not sure how large of a vent I will need to ensure that proper air flow is maintained. Any advice would be appreciated. Thanks.

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It depends on where the water heater is. If in the home and drawing air from the home then the door should probably be sealed with weather stripping and combustion air brought in from the attic with a pipe just abobe floor level. Also a screened opening in the ceiling for ventilation for the unit. Of course this all depends on the location of the unit and the size of the unit for proper sized combustion air supply. You should consult a plumber for proper codes and installation.

You will need at least two vents, at least 3" minimum dimension, at least 144 sq inches (with a metal louver, with a wood louver the size will go way up), one within 12 inches of the ceiling and one within 12 inches of the floor, and ... you may need larger openings depending on the size of the water heater (Btu/hr input rating, not gallons).

There are many variables, but the above would be minimums, you may need more.

Ted's advice to have a plumber come out is a plus and a minus ... a plus in that they SHOULD KNOW what you will need ... a minus in that many DO NOT KNOW what you need - this is based on seeing as many water heaters incorrectly installed 'by plumbers' as we do. Either 'they do not know', or 'do not care', what is required - I would hope that 'they do not know' instead of 'they do not care'.

Jared

As I do agree with a good portion of what Jerry says I also have great faith in tradesmen if approached properly. Yes many plumbers will screw it up. The other half will do it right.

However. If you press them on it and literally have them show you the proper instalation by the newest code (and that is what you should go by where you are making changes) then the likelyhood of screwing up is extremely minimised. After all you appear to be doing this yourself. If you know a plumber or even consult with a plumbing company, press the on proper instalation for todays codes. If they are not doing the work they a not likely to cheat or ignore proper installation.

As I also mentioned. It depends on where in the home the water heater is. Or more to the fact of where it is drawing combustion air from and where or what room it will be possibly venting to. Way to much going on with water heaters or heating units and their combustion and or ventilation to get hits from this or any site. There mmay be factors in your home that might not get conveyed.

Ventilation of any type of fired unit is not something to take litely. After all it is you and your families lives at stake. Don't mess up.

Originally Posted by Jerry Peck

You will need at least two vents, at least 3" minimum dimension, at least 144 sq inches (with a metal louver, with a wood louver the size will go way up), one within 12 inches of the ceiling and one within 12 inches of the floor, and ... you may need larger openings depending on the size of the water heater (Btu/hr input rating, not gallons).

There are many variables, but the above would be minimums, you may need more.

Ted's advice to have a plumber come out is a plus and a minus ... a plus in that they SHOULD KNOW what you will need ... a minus in that many DO NOT KNOW what you need - this is based on seeing as many water heaters incorrectly installed 'by plumbers' as we do. Either 'they do not know', or 'do not care', what is required - I would hope that 'they do not know' instead of 'they do not care'.

Would the total vent space need to be 144 in^2 or would each vent need to be 144in^2?

Originally Posted by Ted Menelly

Jared

As I do agree with a good portion of what Jerry says I also have great faith in tradesmen if approached properly. Yes many plumbers will screw it up. The other half will do it right.

However. If you press them on it and literally have them show you the proper instalation by the newest code (and that is what you should go by where you are making changes) then the likelyhood of screwing up is extremely minimised. After all you appear to be doing this yourself. If you know a plumber or even consult with a plumbing company, press the on proper instalation for todays codes. If they are not doing the work they a not likely to cheat or ignore proper installation.

As I also mentioned. It depends on where in the home the water heater is. Or more to the fact of where it is drawing combustion air from and where or what room it will be possibly venting to. Way to much going on with water heaters or heating units and their combustion and or ventilation to get hits from this or any site. There mmay be factors in your home that might not get conveyed.

Ventilation of any type of fired unit is not something to take litely. After all it is you and your families lives at stake. Don't mess up.

Thanks for your reply. The water heater is in a closet that connects to a foyer in the house. There is an overhead exhaust hood that leads to the roof and the only current air intake is through the louvered door that I am planning to remove.

Being in the entry foyer, adding vents in the wall will be unsightly. I am sure this is why you are changing the louvered door out. I would take combustion and ventilation to the attic.

Just my personal preference for that area.

How would you recommend ventilating through the attic for the intake? I agree that it would look much better and yes that is the reason I am removing the louvered door.

http://www.americanwaterheater.com/s...flameguard.pdf
Take a look at these installation instructions. Your brand may vary and you should look at those, but this will give a few ideas of the options for venting and the requirements for sizing.

Originally Posted by Jared Mitchell

How would you recommend ventilating through the attic for the intake? I agree that it would look much better and yes that is the reason I am removing the louvered door.

Click on Jims link and check out page 9 second diagram

Thanks to both of you for your help. These diagrams and the information are great.

Originally Posted by Jared Mitchell

Would the total vent space need to be 144 in^2 or would each vent need to be 144in^2?

The minimum net free vent area of EACH opening is 100 square inches. Install a louver and the net free vent area is reduced, which is why a metal louver opening needs to be 144 square inches.

But, that is the minimum based on the information you gave, there are many variables which would affect that in various ways.

Please refer to a contractor certified by the Building Performance Institute or the National Comfort Institute. The real issue here is Combustion Zone Depressurization and it has to do with the whole house and not with the size of the openings to the closet containing the water heater. The answer is found with a digital manometer and not with a one-size-fits-all opening.

Originally Posted by Ed Voytovich

The real issue here is Combustion Zone Depressurization and it has to do with the whole house and not with the size of the openings to the closet containing the water heater.
.
The answer is found with a digital manometer and not with a one-size-fits-all opening.

Hi Ed,

Code Is The Minimum ( you have to at least Start With The Minimum.)

Would you go to the top left, click on User CP and put in your location,occupation?

thanks,

I wonder what this critical life threatening need for combustion air is about?
Simpson the Bvent manufacturer wants the dilution air to protect its vents from corrosion.
Saying
" Ventilation of any type of fired unit is not something to take lightly. After all it is you and your families lives at stake. Don't mess up."
is silly.
New code standards for a confined space in a energy star level home ,applied universally are ludicrous in some conditions.
The math for burning gas shows a need for half of what the minimum amount is by the 50 cubic feet per 1000 btu's rule.
Half is what you really should have. Leave a little room under the new door, "the undercut"
Use a normal looking register that matches the rest of the house if you want a hole thru the wall and move on . It's only a water heater.on for maybe 20 minutes twice a day.
When I think about a turkey in the oven for 6 hours and 4 burners cookin , wheres the ventilation air and venting then?

Originally Posted by Richard Pultar

I wonder what this critical life threatening need for combustion air is about?
Simpson the Bvent manufacturer wants the dilution air to protect its vents from corrosion.
Saying
" Ventilation of any type of fired unit is not something to take lightly. After all it is you and your families lives at stake. Don't mess up."
is silly.
New code standards for a confined space in a energy star level home ,applied universally are ludicrous in some conditions.
The math for burning gas shows a need for half of what the minimum amount is by the 50 cubic feet per 1000 btu's rule.
Half is what you really should have. Leave a little room under the new door, "the undercut"
Use a normal looking register that matches the rest of the house if you want a hole thru the wall and move on . It's only a water heater.on for maybe 20 minutes twice a day.
When I think about a turkey in the oven for 6 hours and 4 burners cookin , wheres the ventilation air and venting then?

Hopefully, no one follows the above advice to 'do what you want because someone thinks that is all that is needed'.

Hopefully, they will instead at least meet minimum code (remember, I keep saying minimum, could need more based on many variables) then have a licensed competent contractor come in and verify the variables and make the final recommendations.

Originally Posted by Richard Pultar

.
I wonder what this critical life threatening need for combustion air is about?
.
" Ventilation of any type of fired unit is not something to take lightly. After all it is you and your families lives at stake.
.
Don't mess up."

.
Well let's Start Here!!! Carbon Monoxide Poisoning: Fact Sheet | CDC APRHB
.

the supply air is for combustion.. to reduce corrosion to the connector and venting.
Ventilation for humans is another issue.
The standard for combustion air is twice the amount required by engineering calculations.
My point is that the air we breath in the newer tight homes is a code deficiency that is rarely mentioned.

Commercial buildings get balence reports that show quantity not quality of air. Same with the house .very rarely do I see fresh air brought in .even if a fireplace is burning with a oven on for hours on end.
I just feel that monoxide issues are from leaking vents or nonexistent venting and not from incomplete burning . or inefficient combustion in a properly sized and maintained vent system.

Combustion air for gas-burning appliances

Exterior: Direct Openings - 12 inches from ceiling and 12 inches from deck (floor)

Horizontal Direct:
2 openings (Hi / Low) minimum of 1 square inch for each 4,000 BTu (each vent)
Ex: 150 K BTu's (75 square inches)(@ 4K BTu's)


Horizontal Ducts: (to exterior)
2 openings (Hi / Low) minimum of 1 square inch for each 2,000 BTu (each vent)
Ex: 150 K BTu's (37.5 square inches)(@ 2K BTu's)

Vertical: 2 openings (Hi / Low) minimum of 1 square inch for each 4,000 BTu (each vent)(can be to a space i.e. attic that is equivalent to outdoors)

Ex: 150 K BTu's (75 square inches)(@ 4K BTu's)

10 inch diameter pipe (circular) is equal to 78.5 square inches (radius squared * Pi)(25 * 3.14)


Interior:
Indoor air source alone only OK if air infiltration rate (ACH) is greater than 0.4 per hour
Minimum volume of appliance space is 50 Cubic ft per 1000 BTu's

Space (closet) with volume less than 50 Cubic ft per 1000 BTu's is OK only if 2 permanent openings to a space with sufficient volume and infiltration ACH 0.4

Ex: 150 K BTu's (150 square inch opening to unconfined space of 7500 cubic feet)

Local codes may vary.