Why is my utility room vented to the outside?

[Jon Bon]

So I have a 10x10 utility room in my basement containing an 80% efficient furnace. In this room there is a 6 inch pvc pipe that is vented to the outside.

Why is it like this? Is there anything else I can do?

Can I simply vent the utility room to the rest of the basement and the cover up the vent to the outside? It makes the basement (which has a bedroom in it) very cold in the winter and I have to assume kills the efficiency of the furnace being in such a cold room.

Appreciate any help on this one.

[Sibley]

Well, you need to have ventilation for the furnace. Is there a vent attached to the furnace, separate from the pipe?

That's about all I've got though.

[Dave1442397]

We had our furnace replaced in 2001, and they installed 6" PVC pipe for intake and exhaust by drilling thru the basement wall. I assume if you have a gas furnace that it should be hooked up like that too.

Next time we replace our (gas) water heater, they said new regulations say it has to be vented thru the wall too.

If your pipe isn't for one of those items, could it have been a dryer vent? If that's all it is, you should be able to cap it on both ends, and maybe stuff some insulation in there too.

[Jon Bon]

So to be a little more clear.

the furnace is exhausted correctly through the chimney, so no surprises there. I have some sort of massive passive supply vent. Basically its a six inch hole in the side of my house, which feels pretty stupid to have!

I guess my point is like every (80% or less efficient) furnace for the past 50 years or so was in the basement or utility room with no supply vent correct? Obviously all those old houses with their non-supply vented furnaces worked fine correct?

The furnace has to draw air from somewhere. So cant it just be the 60 degree basement and not the 20 degrees it is outside?

[mre]

The furnace has to draw air from somewhere. So cant it just be the 60 degree basement and not the 20 degrees it is outside?

When the furnace pulls air from the 60 degree basement, it is pulling 20 degree air into the house somewhere.  Most newer appliances use outside air that is brought in through a pipe for combustion to avoid pulling cold air into the house.

My guess for your situation is that the 6" hole w/ pipe was installed with the expectation that the pipe would go to the intake on your furnace, but for some reason that didn't happen.  It could have been forgotten, installer didn't have the correct fittings, etc.

[Syonyk]

It's likely a combustion air source for the furnace.  Is the utility room normally well sealed?  If not, you might consider doing that.

The difference in efficiency between sucking 0F air and 70F air, to the furnace burner, would be quite difficult to measure.  But sucking cold air through the rest of your house will have an impact.

On the plus side, you're probably set up when you want to install a high efficiency condensing furnace!

[Jon Bon]

It's likely a combustion air source for the furnace.  Is the utility room normally well sealed?  If not, you might consider doing that.

The difference in efficiency between sucking 0F air and 70F air, to the furnace burner, would be quite difficult to measure.  But sucking cold air through the rest of your house will have an impact.

On the plus side, you're probably set up when you want to install a high efficiency condensing furnace!

I guess its probably a safety thing as there is a bedroom in the basement, if the furnace was drawing from the house it would pull CO from the hot water tank? Probably overly cautious but I guess I will leave it for now. Really I want to cap the huge hole, and have it draw from the house air.

I mean its gotta be super inefficient, Its all of my un-insulated ductwork originating in a room that is about 10 degrees in the dead of winter. Luckily I dont pay the gas bill on that house. However it does make the downstairs somewhat uncomfortable.

[canadian bacon]

I am having a hard time figuring out your problem but here I go:

A gas furnace should be attached to outside by 3 ways.   
6" PVC  Intake for combustion (clean air)
6" PVC Exhaust (air containing carbon monoxide)
optional?   large clean air intake for house circulating air  (this will be rectangular and a foot and a half wide by a foot deep)

So anyway none of these are open (allow air to leak outside the pipes/vent box) to the furnace room and none of these should cool the furnace room.  They should all be part of a sealed system and you can insulate the air intake box if you want.

If this is in a basement and you have an "open hole" it may be a cheap solution for argon gas venting although it should have a fan to pull the argon gas air out of the basement.
or it could be an old hole from a dryer vent that no one covered up.

[Jon Bon]

I am having a hard time figuring out your problem but here I go:

A gas furnace should be attached to outside by 3 ways.   
6" PVC  Intake for combustion (clean air)
6" PVC Exhaust (air containing carbon monoxide)
optional?   large clean air intake for house circulating air  (this will be rectangular and a foot and a half wide by a foot deep)

So anyway none of these are open (allow air to leak outside the pipes/vent box) to the furnace room and none of these should cool the furnace room.  They should all be part of a sealed system and you can insulate the air intake box if you want.

If this is in a basement and you have an "open hole" it may be a cheap solution for argon gas venting although it should have a fan to pull the argon gas air out of the basement.
or it could be an old hole from a dryer vent that no one covered up.

OK so this is an 80% efficient furnace, this is important to note.

A 90% efficient furnace and above will have a supply and exhaust 2 inch pvc line vented to the outside, this is very common. This is known as direct vent.

Older less efficient furnaces which is what I have (mine is maybe 5 years old?) are exhaust vented directly into the chimney, they 'draw' their air from the area around them.  This is usually the design on every house built from like 1940-1980. None of these homes have a big ass holes to the outside.

Why do I have a big ass hole to the outside when my furnace does not require one, when like half of existing homes have the exact same set up as mine without the hole!

All I can come up with is they want it to prevent the furnace from creating negative air pressure thus pulling carbon monoxide from the hot water tank? I feel like creating this massive inefficiency is a poor way to do it. Its essentially putting my furnace outside, this feels stupid to me.

Note: No furnace in my area uses a six inch line, that's a HUGE pipe.

[Heroes821]

Depending on your location, this could be a Radon mitigation as well.  Usually the pipe should be going into your slab, but the $1000 Radon Mitigation System the previous owners of my first house put in, because it failed the inspection was basically a pvc pipe into the ground, an elbow, and a pvc pipe through the wall outside.  Now are you talking 6 inch diameter or 6 inch long?

[canadian bacon]

Thank you for correcting me.   Yes, the furnace intake and exhaust will be definitely in the 2" range, not 6"

I still think you are looking at a argon gas vent or an old hole for a dryer.   Nothing related to the furnace should be open to the basement air

[Ocinfo]

I have this in the basement of my rental unit. Have had a home inspector and HVAC tech state that it's to provide fresh air to prevent negative pressure. Unit was built in 70s and has a 80% furnace. Had never seen this before.


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[nedwin]

As others have stated, the pipe you refer to allows combustion air into your utility room.  The vent relieves negative pressure caused by the furnace when it is operating (the exhaust going up the chimney has to come from somewhere).  If you have a gas water heater in the same utility room the vent also helps it draft sufficiently while heating water.  This ventilation is likely required by your local building code.  If the vent is plugged, the furnace and water heater will draw combustion air from the utility room, which may not be able to provide sufficient ventilation for the proper operation of either appliance.  In the worst case, plugging the ventilation could cause CO to build up in the living space.  You should not plug the ventilation pipe.

Here's additional explanation via google:  https://www.google.com/search?q=combustion+air+vent+requirements&ie=utf-8&oe=utf-8

As an example, in our unfinished basement we have an 80% furnace and a gas water heater.  Neither have "sealed" combustion, instead they draw combustion air from the surrounding space.  Our basement has TWO vents from the outside, one 6" the other 8".  The vents are galvanized duct material (not PVC like yours) and empty directly over the furnace and water heater.

[Jon Bon]

As others have stated, the pipe you refer to allows combustion air into your utility room.  The vent relieves negative pressure caused by the furnace when it is operating (the exhaust going up the chimney has to come from somewhere).  If you have a gas water heater in the same utility room the vent also helps it draft sufficiently while heating water.  This ventilation is likely required by your local building code.  If the vent is plugged, the furnace and water heater will draw combustion air from the utility room, which may not be able to provide sufficient ventilation for the proper operation of either appliance.  In the worst case, plugging the ventilation could cause CO to build up in the living space.  You should not plug the ventilation pipe.

Here's additional explanation via google:  https://www.google.com/search?q=combustion+air+vent+requirements&ie=utf-8&oe=utf-8

As an example, in our unfinished basement we have an 80% furnace and a gas water heater.  Neither have "sealed" combustion, instead they draw combustion air from the surrounding space.  Our basement has TWO vents from the outside, one 6" the other 8".  The vents are galvanized duct material (not PVC like yours) and empty directly over the furnace and water heater.

Thanks Nedwin

That is what I suspected, but you summarized better than I could!

However I think this is a STUPID way to do things. Do we know how many homes have an 80% or less furnace creating negative air pressure that 'could' (and I emphasis  could) create a CO problem? Its got to be in the millions, like 25 million? Maybe more?

An 80%  furnace is not going to create a CO problem if its not supply vented to the outside. That just cannot be true. I am not an HVAC guy, but again I have a million reasons listed above why this has to be the case right?

So the solution to a almost zero chance of someone being hurt by CO is to require code to say yeah just cut a huge ass hole in your house and crush the efficiency of your furnace? I say screw the code, I want a warm house, if there is a .000001% of someone getting hurt by CO I am going to roll those dice. This is kind of why sometimes I hate the code, but tahts a whole differnt post!

I still dont think I will plug it, but I think I could and it would not create problems.  I probably should call my HVAC guy....



More info: the hot water tank is on the complete other side of the basement in a different utility room. House has had a major remodel to the basement int he past 5-10 years so being done 'to code' at huge cost to efficiency might be the reason.

[Ocinfo]

As others have stated, the pipe you refer to allows combustion air into your utility room.  The vent relieves negative pressure caused by the furnace when it is operating (the exhaust going up the chimney has to come from somewhere).  If you have a gas water heater in the same utility room the vent also helps it draft sufficiently while heating water.  This ventilation is likely required by your local building code.  If the vent is plugged, the furnace and water heater will draw combustion air from the utility room, which may not be able to provide sufficient ventilation for the proper operation of either appliance.  In the worst case, plugging the ventilation could cause CO to build up in the living space.  You should not plug the ventilation pipe.

Here's additional explanation via google:  https://www.google.com/search?q=combustion+air+vent+requirements&ie=utf-8&oe=utf-8

As an example, in our unfinished basement we have an 80% furnace and a gas water heater.  Neither have "sealed" combustion, instead they draw combustion air from the surrounding space.  Our basement has TWO vents from the outside, one 6" the other 8".  The vents are galvanized duct material (not PVC like yours) and empty directly over the furnace and water heater.

Thanks Nedwin

That is what I suspected, but you summarized better than I could!

However I think this is a STUPID way to do things. Do we know how many homes have an 80% or less furnace creating negative air pressure that 'could' (and I emphasis  could) create a CO problem? Its got to be in the millions, like 25 million? Maybe more?

An 80%  furnace is not going to create a CO problem if its not supply vented to the outside. That just cannot be true. I am not an HVAC guy, but again I have a million reasons listed above why this has to be the case right?

So the solution to a almost zero chance of someone being hurt by CO is to require code to say yeah just cut a huge ass hole in your house and crush the efficiency of your furnace? I say screw the code, I want a warm house, if there is a .000001% of someone getting hurt by CO I am going to roll those dice. This is kind of why sometimes I hate the code, but tahts a whole differnt post!

I still dont think I will plug it, but I think I could and it would not create problems.  I probably should call my HVAC guy....



More info: the hot water tank is on the complete other side of the basement in a different utility room. House has had a major remodel to the basement int he past 5-10 years so being done 'to code' at huge cost to efficiency might be the reason.

At least put a CO detector in the area. Also, the air has to be drawn from somewhere so you're just going to pull in cold air throughout the house instead of in a room you don't care about.

The vent in my place does make more sense because it's a small room (10x6) with the furnace, water heater and dryer with a solid door.


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[nedwin]

Jon Bon-

I have no idea what the chances of CO accumulation would be, I'm not an expert, so call your HVAC guy for a more satisfactory answer.  But I think the vent to your utility room may be more efficient than plugging it.  The combustion air has to come from somewhere, so it makes more sense to me that it come directly to your utility room than through other penetrations/wholes in your house (windows, doors).  It seems that the combustion air delivered directly to the utility room would be drawn out of the house through the furnace more quickly than the combustion air that enters through windows and doors, and would have less affect on the temperature in the conditioned space.

Can I ping Paddlehat on this?  He has a strong opinion regarding the code but also has extensive home building experience and might be able to help you better than me.

[Jon Bon]

Jon Bon-

I have no idea what the chances of CO accumulation would be, I'm not an expert, so call your HVAC guy for a more satisfactory answer.  But I think the vent to your utility room may be more efficient than plugging it.  The combustion air has to come from somewhere, so it makes more sense to me that it come directly to your utility room than through other penetrations/wholes in your house (windows, doors).  It seems that the combustion air delivered directly to the utility room would be drawn out of the house through the furnace more quickly than the combustion air that enters through windows and doors, and would have less affect on the temperature in the conditioned space.

Can I ping Paddlehat on this?  He has a strong opinion regarding the code but also has extensive home building experience and might be able to help you better than me.

Yeah I was just kind of waiting around until he showed up!

Maybe I should have posted to the DIY section.

[Syonyk]

Seriously. It's not like it's heating the outside air to blow in the rest of the house. It's just combustion air.

Insulate that room and seal it a bit better if you like. It's still a lot better than pulling air through all the other gaps in the house and running old sir through everything to get combustion air.

[Jon Bon]

Seriously. It's not like it's heating the outside air to blow in the rest of the house. It's just combustion air.

Insulate that room and seal it a bit better if you like. It's still a lot better than pulling air through all the other gaps in the house and running old sir through everything to get combustion air.

All, I really appreciate your insight on this, I learn so much on these boards every day.

True.

But also true, every single one of my ducts is sitting in 10 degree temperature. So all the air in the ducts ends up in the house. And all the ducts are losing a ton of heat in that ice cold air are they not?

This has got to be a new code requirement in the name of safety, but is it at the cost of efficiency? And it sure  makes that bedroom in the basement cold.

And maybe I am wrong on which is more efficient, but I have a hard time believing what is essentially putting your furnace outside your house makes anything more efficient.  Yes a furnace with no venting to the outside will draw cold air from outside, but only when running. This 'passive vent' as I am calling it is open all the time, dumping cold air into my house 24/7.

I reiterate my previous points, millions of homes have an 80% furnace in the basement with no hole cut in the side of the house. Surely if something as easy as cutting a small hole in the house increased efficiency it would have been done in the past right?

Really what I want to know is this simply done for code purposes, or is there an actual legitimate reason for it?

A quick google search shows that 500 a year die from CO poisoning. However the vast majority of these happen from portable propane type heaters in enclosed spaces.  In my situation obviously the furnace vents the CO correctly, the issue is the negative air pressure on the gas hot water tank.

[jbfishing]

Sounds like you need to check  your local codes.  They are only a phone call away, or stop by in person for a visit.

[nobody123]

In my old house, I ran into this when I was going to finish my basement.  The inspector gave me three options: use a louvred door to the unfinished side so the gas furnace and water heater could continue to draw air from the entire basement, make the finished side smaller so the area of the unfinished side was bigger, or cut a vent.  We only had to move a wall like 6" to meet the space requirements, so we chose to do that.

[ChpBstrd]

Build a sealed, insulated closet around the furnace, and dump the insulated air supply duct into the closet. Do the same for the water heater. Use materials not vulnerable to mold because there will be a large temperature/humidity difference across those surfaces.

[Mgmny]

Sorry for bumping this dead thread, but OP is still active.

What did you end up doing? My house has the same thing, and it's annoying that i'm heating the entire house, then have this giant insulated tube that basically runs from the back of the house to the floor in my basement dumping in tons of cold (albeit "fresh") air.

And why do i have this if i also have a fresh air exchanger?

[Fishindude]

Has been answered, but this is combustion air intake for your furnace to run off of.   
I furnace fire needs air to burn so having the air intake close like this and directly from the outside is most efficient.   Otherwise, it will pull air under the door crack of this room from other areas of the house.

[Mgmny]

Has been answered, but this is combustion air intake for your furnace to run off of.   
I furnace fire needs air to burn so having the air intake close like this and directly from the outside is most efficient.   Otherwise, it will pull air under the door crack of this room from other areas of the house.

Well, i know the "purpose" of the tube, yes. But I don't know if OP plugged his anyways. In my case, I also have an fresh air-exchanger that i'd much prefer my air to flow through than just this random open insulated non-filtered ducting.

Maybe air exchanger need to exchange at 1:1, i have no idea.

[Jon Bon]

Yeah I am still here.....

I did not end up doing much of anything as it is a rental.

However I still maintain the code is at minimum stupid, and at maximum just plain wrong.  Most houses with a 80% furnace have it sitting in the basement right next to the water heater, no one dies. No CO alarms go off. Literally nothing ever happens.

This requirement that my furnace needs to basically be outside (due to the venting) has got to be one of the worst ideas ever. That means all my duct work dumps cold air into the house while the furnace is off. My furnace room is about ~ +-10 degrees from the outside air. With the emphasis on efficiency these days, there has got to be a better way.

My end game with be to replace with a direct vent furnace and seal up the vent.

*Rant over*

[Mgmny]

Yeah I am still here.....

I did not end up doing much of anything as it is a rental.

However I still maintain the code is at minimum stupid, and at maximum just plain wrong.  Most houses with a 80% furnace have it sitting in the basement right next to the water heater, no one dies. No CO alarms go off. Literally nothing ever happens.

This requirement that my furnace needs to basically be outside (due to the venting) has got to be one of the worst ideas ever. That means all my duct work dumps cold air into the house while the furnace is off. My furnace room is about ~ +-10 degrees from the outside air. With the emphasis on efficiency these days, there has got to be a better way.

My end game with be to replace with a direct vent furnace and seal up the vent.

*Rant over*

Thanks JB. I will probably leave mine (unless someone chimes in about my air exchanger serving the same purpose). I think i'll eventually wall this off and caulk/insulate the walls from the inside so it's "air tight" so the outside air only gets into this room and not the rest of my house. Doing this is a WAYS away though, so in the meantime, i'll just be heating outside air just to dump it back outside.

I agree with you though. My last house had exactly 0 venting from the outside and we had a CO monitor near the furnace and it never made a peep. Granted, that house was sealed much worse than my current house, but still. Dumb.

[APowers]

I agree that the purpose of the hole is to provide combustion air. I agree that dumping frigid air into your house seems like a terrible idea. Perhaps you could route the vent more directly to the furnace combustion chamber? Also, I would consider adding insulation to the inside-air ducting. However, when I redid my basement, I didn't want louvered doors on my furnace closet, so I (reluctantly) piped a 6" outside vent to the furnace room to provide combustion air.

Another perspective that no-one here has mentioned is the problem with a whole-house fan. [Source, am a handyman, and have encountered this before.] In the case where your house has a whole-house/attic fan (the kind that pulls air from the house and blows it outside, usually through a big vent in the attic); with inadequate venting (i.e., no windows open), it can create a low pressure in the house that results in reversing the flow of air/exhaust through the furnace/water-heater chimneys. Obviously, this is extremely dangerous due to CO buildup as well as possibly putting out the pilot light and filling the house with gas. However, having a 6" duct into the furnace room would almost certainly alleviate this, as the fan could pull air from outside without it coming down the chimney.

[Syonyk]

If the pilot light goes out, the thermocouple should shut down the gas flow awfully fast - and if it doesn't, then something is broken and needs to be fixed.  But usually that system fails closed - so the pilot light won't stay lit, not so the gas stays running with the pilot light out.

[APowers]

If the pilot light goes out, the thermocouple should shut down the gas flow awfully fast - and if it doesn't, then something is broken and needs to be fixed.  But usually that system fails closed - so the pilot light won't stay lit, not so the gas stays running with the pilot light out.

I mean, yes. But still not a risk I would want to take....