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Discussion Starter #1
I live in a town home built in 1977 in Southern California.
I noticed that there are 2 air ventilation vent and 1 air hole for which I do not understand their purpose well.

The photos below show the air vent underneath the 2nd floor room. I can understand the air vent underneath the roof for the attic ventilation, but this one is under the 2nd floor room.
20201017_083942.jpg


20201017_085204.jpg



The photo below shows a hole underneath of outside stucco wall near the bottom. There are more holes like this apart from each other.
20201017_114259.jpg



The photo below shows the air vent inside the HVAC closet. The air to the HVAC heating/air-con comes from the underneath the HVAC unit connected to the outside big air vent.
20201017_120936.jpg


Could you explain what their purposes are?

Thank you very much.
 

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Naildriver
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Being California, I'd say it was for make up air for the HVAC system. Other parts of the country would probably not use it due to the influx of cold air freezing everything in the room.
 

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Discussion Starter #5
Thank you chandler48, Half-fast eddie, Nealtw very much for the comments.

Do you mean that the vent in the closet is to provide the oxygen for the gas furnace to burn or for the gas to escape in case it leaks? The the closet is inside near the middle of the house on the first floor, and is the air coming in from the enclosed wall where the stud is? Or is the gas going to escape to the inside of the wall? I think the wall is the closed space with the drywall on all 4 or 6 sides

Nealtw, where is the vented soffi connected to? Is that connected to the 1st floor ceiling void all over the place? There were termite droppings at the entrance, and one of the termite treatment company staff suspected that the dropping might be coming from the soffi vent. So, I am wondering what could be there inside.

How about the hole? What is the purpose? Is that to circulate the air inside the drywall where the fiberglass insulation is?

Thank you very much.
 

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retired framer
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Thank you chandler48, Half-fast eddie, Nealtw very much for the comments.

Do you mean that the vent in the closet is to provide the oxygen for the gas furnace to burn or for the gas to escape in case it leaks? The the closet is inside near the middle of the house on the first floor, and is the air coming in from the enclosed wall where the stud is? Or is the gas going to escape to the inside of the wall? I think the wall is the closed space with the drywall on all 4 or 6 sides

Nealtw, where is the vented soffi connected to? Is that connected to the 1st floor ceiling void all over the place? There were termite droppings at the entrance, and one of the termite treatment company staff suspected that the dropping might be coming from the soffi vent. So, I am wondering what could be there inside.

How about the hole? What is the purpose? Is that to circulate the air inside the drywall where the fiberglass insulation is?

Thank you very much.
Fire air does supply oxygen fire the fire and air for the draft so the exhaust vent works properly.
Your floor sticks out passed the lower wall that part of the floor is insulated.
631238
 

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The low one in the furnace room is a combustion air intake, should also be one higher about 12" from the ceiling.
 

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The low one in the furnace room is a combustion air intake, should also be one higher about 12" from the ceiling.
The hole reflected in the mirror is a weep hole in the weep screed if you were to clean the stucco off the bottom of the weep you will find many of those holes.
 

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Discussion Starter #9
Thank you Nealtw, beenthere, ClarenceBauer very much for the comments. I understand better thanks to your explanations.

Nealtw, I do not quite understand the diagram and your statement. Could you please paraphrase this?
Your floor sticks out passed the lower wall that part of the floor is insulated.
I guess that the 2 vents in the first and last photos are connected as the diagram below via air duct. Is this correct?

HVACvent3.png


Beenthere, I noticed that there is a vent pipe at the ceiling in the closet, and I now think that it is for gas combustion exhaust to the outside. I thought the combustion air intake is used by the air coming from the air filter. I think then there are two incoming air for the furnace, one filtered air for the warm air supplied to each room and the other for the gas furnace combustion.

ClarenceBauer, I learned new words weep hole and weep screed. I found the weep hole because I noticed the termite droppings right below the weep hole. I had it treated by the professional termite company. If there is a dropping, is there a bad damage already to the stud? If there is a weep hole, is there usually a path to the stud and insulation material? I am asking this because if I apply some termite insecticide diluted with water on to the stud behind the drywall via needle injection, will the moisture from the water eventually evaporate and escape to the outside instead of being trapped forever inside the drywall, causing some unknown damages to the stud like mold?

Thank you very much.
 

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Combustion air, and the air for the house, are not the same/don't use same ducts.
 

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Discussion Starter #12
Thank you Nealtw very much for explaining it again. Now I understand what you mean by the sentence. Still, my question remains. Where is the air vent in the outside connected to? Or are the air vents in the 1st and last photos connected via air duct as I showed in the diagram?

I took a photo of the air vent inside, using the endoscope, in the last photo, and it seems that is is connected to something at the top as the photo below shows. Is that really connected to the outside air vent in the 1st photo for the air?

20201018_111033.jpg
20201018110801.jpg


Also, I took another photo in the closet, and there is another air vent duct at the ceiling in addition to the gas furnace exhaust pipe. So, as Beenthere mentioned, I think this is for the gas leak or air circulation inside the closet . Am I correct by saying this?

20201018_090517.jpg


Thank you very much.
 

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The hole in the ceiling would be for combustion air.
 

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Discussion Starter #14
Thank you Beenthere very much for the comment.
So, then the combustion air is coming in from the hole in the ceiling and the wall air vent.
Thank you.
 

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retired framer
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Thank you Nealtw very much for explaining it again. Now I understand what you mean by the sentence. Still, my question remains. Where is the air vent in the outside connected to? Or are the air vents in the 1st and last photos connected via air duct as I showed in the diagram?

I took a photo of the air vent inside, using the endoscope, in the last photo, and it seems that is is connected to something at the top as the photo below shows. Is that really connected to the outside air vent in the 1st photo for the air?

View attachment 631313 View attachment 631314

Also, I took another photo in the closet, and there is another air vent duct at the ceiling in addition to the gas furnace exhaust pipe. So, as Beenthere mentioned, I think this is for the gas leak or air circulation inside the closet . Am I correct by saying this?

View attachment 631312

Thank you very much.
The round pipe going out the ceiling is doing the job of a chimney, it takes the gases away after the fuel has burned.
THe fire needs air and would take it from the house if it did not have a supply from outside.
As it is in a closet it could have trouble pulling air from the house and then it would try to pull air down the chimney and all those exhaust gasses would fill the closet and maybe the house. Deadly.
 

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Discussion Starter #16
The round pipe going out the ceiling is doing the job of a chimney, it takes the gases away after the fuel has burned.
THe fire needs air and would take it from the house if it did not have a supply from outside.
As it is in a closet it could have trouble pulling air from the house and then it would try to pull air down the chimney and all those exhaust gasses would fill the closet and maybe the house. Deadly.
Thank you Nealtw very much for the comment.

The air vent on the wall in the closet must be there for a reason. I looked inside further up, and it is a rectangular tin air duct going all the way up to the 1st floor ceiling. It looks like it is connected to somewhere to get the air. The outside air vent in the 1st photo and this air vent seem to be on the straight line, so it looks they are connected to the outside vent. Can the 2 air vents can be connected like this? Should I ask this question to the HVAC forum?

Thank you very much.
 

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retired framer
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Thank you Nealtw very much for the comment.

The air vent on the wall in the closet must be there for a reason. I looked inside further up, and it is a rectangular tin air duct going all the way up to the 1st floor ceiling. It looks like it is connected to somewhere to get the air. The outside air vent in the 1st photo and this air vent seem to be on the straight line, so it looks they are connected to the outside vent. Can the 2 air vents can be connected like this? Should I ask this question to the HVAC forum?

Thank you very much.
I don't know what the extra one is for at the ceiling
 

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I have not seen that before
Actually, code required it when that house was built, or when that furnace was originally installed.

In 2015 IFGC changed to allow a single high opening, that must be with 12" of the ceiling, or through the ceiling.
 
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