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Old 01-18-2013, 09:10 AM   #1
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Enclosed HVAC room ventilation


I plan on enclosing my furnace and gas water heater in a 10x10 foot room in our basement to conceal them. I was researching ventilation needed for the room, and found that a high and low vent should be installed with the size depending on the BTU's.

However, from what I found louvered doors are not recommended? Can someone please explain. Louvered doors seem like they would be larger than a vent, and satisfy both the high and low ventilation requirements.

Any info on this would be appreciated.

Thanks

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Old 01-18-2013, 09:20 AM   #2
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The furnace (gas I assume) and water heater exhaust air from the house when they operate, so you need makeup air (vents to the outside). A louvred door doesn't provide makeup air.

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Old 01-18-2013, 09:27 AM   #3
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Shazapple - Thanks for your post.

But a high and low vent opening, will take care of this? Where a louvered door will not? I guess my confusion is that a 36 in louvered door would seem to have as much opening as the vents?
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Old 01-18-2013, 10:31 AM   #4
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Where your getting confused, is that the high and low vent would need to be cut in to an exterior wall, outside air. The louver door your refering to, would be drawing air from the basement itself.

I dont see how the high and low vent setup would work in an underground basement. However, there are many ways to pipe in the needed fresh air for combustion.
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Old 01-18-2013, 10:57 AM   #5
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So before building a mechanical room for the HVAC it is just ok sitting in the basement without outside air being pumped in, but once enclosed you need outside air pumped in?

I see mechanical rooms regularly in rehabbed properties that I visit with no such outside vents.

I am not challenging your knowledge, or that you are correct, more or less explaining where my view was coming from.

Thanks for the replies.
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Old 01-18-2013, 11:29 AM   #6
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Quote:
Originally Posted by troyce1 View Post
So before building a mechanical room for the HVAC it is just ok sitting in the basement without outside air being pumped in, but once enclosed you need outside air pumped in?

I see mechanical rooms regularly in rehabbed properties that I visit with no such outside vents.

I am not challenging your knowledge, or that you are correct, more or less explaining where my view was coming from.

Thanks for the replies.
Every state has different codes, need to check what yours would be.

I never really cared for the idea of using inside air for combustion, even in a large room. If my choice, I would want the equipment in a seperate room with outside air for combustion.
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Old 01-18-2013, 11:32 AM   #7
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Quote:
Originally Posted by sammy37
I dont see how the high and low vent setup would work in an underground basement. However, there are many ways to pipe in the needed fresh air for combustion.
In my area most basements are underground and we are required a high and a low combustion air pipe. For the high one we pipe it in from the outside and 90 the pipe down so it pours in air from up high. For the low one we do the same thing but then pipe it down to about a foot off the ground. We do all of this in 6" galvanized and have intake hoods on the outside
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Old 01-18-2013, 12:05 PM   #8
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Hmm. this unit was installed just 2 years ago, and is in a basement, and passed inspection by the county, but unless I'm missing something there is no intake or outtake.

I will take some pics and post online shortly.
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Old 01-18-2013, 12:35 PM   #9
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Originally Posted by HVAC1000 View Post
In my area most basements are underground and we are required a high and a low combustion air pipe. For the high one we pipe it in from the outside and 90 the pipe down so it pours in air from up high. For the low one we do the same thing but then pipe it down to about a foot off the ground. We do all of this in 6" galvanized and have intake hoods on the outside
Makes sense. I figured there must be some kind of pipe setup to get it in there.
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Old 01-18-2013, 01:47 PM   #10
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Originally Posted by troyce1 View Post
Hmm. this unit was installed just 2 years ago, and is in a basement, and passed inspection by the county, but unless I'm missing something there is no intake or outtake.

I will take some pics and post online shortly.
There probably isn't, I've never seen vents outside other than the actual pvc intake run outside. But I've seen plenty of units intaking basement air, none of them to my knowledge had vents going outside.

Your unit should work fine without them it's probably just a code thing that doesn't apply in your area. But I would recommend doing something 9like a louvred door) to allow more air into such a small room suuounding your furnace.
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Old 01-18-2013, 02:14 PM   #11
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if you do not bring in combustion air from the outside it will cause a negative pressure in your house. this negative pressure will pull in from somewhere. if you have a natural draft water heater it will pull in air from that flue. this will make the water heater not vent correctly and it WILL spill out Carbon Monoxide into your house. yes the combustion air is just a code thing but codes are there to protect people and lives. even if you just bring it in from louvered doors it will still cause negative pressure in your house. it is an inexpensive project that is very easily DIYed.

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Old 01-18-2013, 02:53 PM   #12
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if you do not bring in combustion air from the outside it will cause a negative pressure in your house. this negative pressure will pull in from somewhere. if you have a natural draft water heater it will pull in air from that flue. this will make the water heater not vent correctly and it WILL spill out Carbon Monoxide into your house. yes the combustion air is just a code thing but codes are there to protect people and lives. even if you just bring it in from louvered doors it will still cause negative pressure in your house. it is an inexpensive project that is very easily DIYed.
Yes it will create negative pressure, but it won't create any situation that he doesn't already have existing. And like I said I've worked almost 10 years in service and have seen many 90% furnaces intaking house air, not to mention all the 80% furnaces and I've never seen vent's going outside. None of those people have had any Carbon Monoxide issues and I can't imagine none of them had natural draft water heaters.

And yes codes are there to protect people, but some areas have codes that are a bit excessive. Just because something is against a code in some particular area doesn't make it dangerous.
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Old 01-18-2013, 03:29 PM   #13
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Quote:
Originally Posted by JScotty

Yes it will create negative pressure, but it won't create any situation that he doesn't already have existing. And like I said I've worked almost 10 years in service and have seen many 90% furnaces intaking house air, not to mention all the 80% furnaces and I've never seen vent's going outside. None of those people have had any Carbon Monoxide issues and I can't imagine none of them had natural draft water heaters.

And yes codes are there to protect people, but some areas have codes that are a bit excessive. Just because something is against a code in some particular area doesn't make it dangerous.
That is all true but my main concern is always safety rather than cost. And why does it hurt to spend a small amount of to ensure his families safety and peace of mind. It's true that you don't need to bring air if your house is old and leaky or your windows are not sealed properly. The furnace is currently pulling its combustion air from an unfinished basement which is a very large space to pull air from. Once you close it off in a smaller room. Even with louvered doors the unit is still pulling from a much smaller place. With the air intakes you are pulling air from outside. And the outside is a very large space. Considering everything said I am just telling my view on it all and what I would do from my years ( yes less than 10) of experience.
JScotty I respect you for all that you have said and defending your side of this. And you have given me a lot to think about and consider. I can see you have a lot of experience and truly know what you are talking about.
This whole situation is up to the homeowner all we can do is give advice and how we would do it in our customers houses
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Old 01-18-2013, 03:37 PM   #14
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I find all this to be hillarious. When I was young my Dad told me that you do not want to make a house too tight. "Why, Dad? arent you just wasting heat otherwise?"

"Well son, you have your pilot lights burning gas, and that uses oxygen, Your Furnace running, which burns a lot of gas, and you have all the chemicals in building materials, and think of your poor mom, what with all the cleaning materials and the stuff they put into the air."

"Yeah, I guess I see what you mean Dad, Thanks"

Fast forward to today. Foam "Stuff" in every crack. Magnetic weatherstripping to steel doors. 10+ inches of insulation in the attic floor, rubber seals on outlets. Poly vapor barriers.

"Sorry sir you have to put in air makeup in your furnace room, or you wont be to code"

What a giant crock of Bovine Scatology
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Old 01-18-2013, 03:42 PM   #15
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Hey HVAC1000, If he has louvered doors how is he pulling makup air from a smaller area? Hes pulling it from the whole basement through the louvered doors.

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