Tanklets > Ventilation Issues

Q: My ~60 year old home has a dedicated water heater closet with an exterior door. The original door was hollow core without vents and was replaced when the luan sheeting began to deteriorate. It has been replaced twice now with hollow core doors that had vents pre-cut in them. It is due for another replacement and I have bought a solid core door so that I can finally put this job to rest. The question is, "Do I need to add vent(s) to the door?"

The original sill plate at the bottom of the door is a two-by-four with 3/4 inch holes running through it, the closet ceiling vents into the attic, and there is a flue above the heater that vents out through the roof. This is a single story home in Southern California. Wondering how much the building code may have changed in this regard, or if the original measures taken when the house was built still suffice. Thank you for your expertise.

A1: I think you you're going to need those vents, but I don't remember the formula for determining how many square inches they need to be. Likely someone else posting here can be more specific. If there is not enough combustion air, the heater will soot up and create a fire hazard. I doubt the holes in the sill are even close to enough. -- Randy

A2: Hello,  The rule of thumb is one square inch of free vent space per 1000 BTUs. Your heater may be 30,000 or 35.000 BTUs.  What I just found, looking this up is code wants two vents, each within a foot of the top and bottom of the door.  They also want 100 square inches at each... which seems generous to me.  You might want to look up "combustion air" under whatever code you use and see what it says. -- Larry

Q2: Thank you for your direction. I will track down my code and see what it says. (3/16/2018)