basement return question

[Columbus12]

Our old furnace expired last week and we had a new furnace and a/c installed. Our complaint with the old one was that the second floor never cooled well.
The techs said that it was because of the air return in the basement. It is located in the ceiling duct. What they said makes sense. A lot of air is being sucked from the basement causing less air to be drawn from the upper floors especially the 2nd floor. They said I didn't need a basement return and even offered to seal it closed with sheet metal. I told them I would have to think about it.
My basement consists of a crawl which is a part of the conditioned space (unvented to the outside) and the crawl is open to the finished utility room that is connected to the finished basement through a louvered door.
The return is in the ceiling duct work immediately past the louvered door (on the finished basement side). The duct hole behind the cover is 14x9.
The finished basement has three air vents located on the walls close to the floor with each being the 6x10 variety.
Each room on the first and second floors has a return with the exception of the kitchen and bathrooms.
Could closing the basement return cause damage to the furnace , a/c or air ducts? Or anything else? Where would the basement air go?
The basement return definitely appears to be pulling air in much heavier than the returns on the other floors. When I put a tiny piece of tissue paper under the basement return it get pulled in more rapidly than when I do it on the other floors. Or is this because the basement return is on the ceiling and the upper floors returns are on the walls? Is their any way to reduce the basement returns air intake rate?
Im also wondering if closing the basement return with or without closing the basement air vents could cause negative pressure in the basement or is most likely that the basement is already in negative pressure? Are there any handy tests I can do to find out?
Lastly...This also has me thinking about the crawl and its relationship to the basement return. The return is 8 feet from the open crawl, immediately past the louvered door on the finished basement side. The door is also 8 feet from the crawl. The crawl has its original 20 year old fiberglass insulation on its three walls. Its is tucked in (not affixed) and has no paper on either side. Could the return be sucking in fibers from the fiberglass and sending them throughout the house? I've always used the cheap furnace filters and wondering now if i should have been using the more expensive ones?
A lot to chew on especially for someone like me who is new to all this and doesn't know what to do.

[genduct]

Although a high return can help the situation, it will never be a substitute for a lack of supply air. You need to figure out how to either balance the system you have OR if the route the air needs to take to that problem area is too difficult, you need to figure how to install a new duct to do the job

[Columbus12]

So it sounds like having no basement return at all (sealing the existing ceiling duct air return) would be absolutely wrong. Would any of this relate to my basement door (door at top of basement stairs) now closing when left open slightly, when the furnace is running? Don't remember the pressure coming from the basement as being as strong with the old furnace. Does this also need to be corrected?

[Shophound]

Depending on how aged your old furnace was, new furnaces tend to move more air than the old models they replace did.

Along this line, you might wait to see how your new system cools upstairs before contemplating any changes. Genduct is correct in that lack of supply air is the primary culprit behind lack of comfort inside your house. Returns help the air that needs to be reheated or cooled/dehumidified again reach the air handler so this can happen. In cooling mode, you can't cool down air that does not get back to the air handler, and you can't displace heat building up in a room without adequate incoming conditioned (cooled and dehumidified) air to replace it. This is why you must have an adequate provision for both supply air inlets and return air outlets.

Most residential systems are not balanced after installation. Most multi-story residences need a greater quantity of air exchange upstairs in summer and downstairs in winter, to offset weaknesses in the building envelope and stack effect/reverse stack effect.

[Columbus12]

Thanks. Sorry but I'm not clear on a couple of things. Would covering the return in the basement improve air flow upstairs or should covering the basement return not even be considered. I'm worried about damaging the furnace/ac.
Can I live with negative basement pressure or is it not recommended?

[llskywalker]

From what you are describing there are supply vents as well as return vents in the basement. If this is the case then cover the return air vent and the supply vents will give the basement a little positive pressure. The real issue is your duct system that was installed during construction of the home. You can add things like turning vanes and curves to help air flow to the rooms.

[genduct]

We don't like return grills in the basement because of the possibility of "seeing" a negative pressure that would suck the flue gas out of the vent (chimney) It doesn't take much negative pressure for this to happen
SO you are going to need to depend on someone who knows about this potential problem and can SEE what is going on. With this forum, we can only guess

[llskywalker]

We don't like return grills in the basement because of the possibility of "seeing" a negative pressure that would suck the flue gas out of the vent (chimney) It doesn't take much negative pressure for this to happen
SO you are going to need to depend on someone who knows about this potential problem and can SEE what is going on. With this forum, we can only guess

Here in Colorado it is a code to have a return air vent installed in a finished basement. The return might be to big for the load. Was a load calc performed that shows how much air is needed in the basement, or the upstairs that seems to be your issues?

[Columbus12]

I just took the grill off and looked into the return. The return opening is one and a half inches below the duct and nothing was sealed. In other words not only is the return sucking in basement room air but also air from above the ceiling and who knows where else. If I could find the bum that put this in in 1996 I'd tell him what I'm thinking. I'm looking through my old receipts. However I'm the dummy for not noticing this. And to think this passed village code inspection. Thought it was done correctly.

[Columbus12]

With regards to having or not having a return in the finished bsmt, does the fact that the crawl is not vented to the outside play into this?

[genduct]

lance the return duct, it would be my opinion that the majority of the return will come from the point of least resistance, which means the basement WILL BE NEGATIVE. But what do the bureaucrats know?

[Columbus12]

My basement is in negative pressure WITH the return.
I thought eliminating the return would get the basement out of negative pressure.

[Shophound]

Would covering the return in the basement improve air flow upstairs or should covering the basement return not even be considered. I'm worried about damaging the furnace/ac.
Can I live with negative basement pressure or is it not recommended?

Covering up return air inlets, generally speaking, will not improve the flow of supply air. HVAC ducting is like an algebra equation...what is done on one side affects the other side.

That said, in your case if the return air inlets on the first and upper floor are of sufficient size, blocking the basement return might help the returns higher up draw an increased volume of air, which can help assure an adequate turnover of air in each area.

As others have said, the main concern about a return in a basement is if that same return has any influence on nearby combustion appliances, such as the furnace or a gas fired water heater. Regardless of whether they vent naturally or with a draft blower, the danger of vent gasses backdrafting into your finished basement remains possible if the combustion appliances are influenced by the return air in the basement.

[Columbus12]

Thanks. Am I understanding this correctly? Are vent gasses more likely to be put into the bsmt because of the return or would they be more likely to be put into the basement without a return or could it happen either way. Sorry for being so dense but I want to be sure of what the possibilities are before I have anything done.
If gas was being vented into the room would we smell it, or would we only know by physical ailments?
It's amazing how complicated HVAC can be.
I never realized the vastness of knowledge a HVAC person needs to be an experienced professional.

[Shophound]

Thanks. Am I understanding this correctly? Are vent gasses more likely to be put into the bsmt because of the return or would they be more likely to be put into the basement without a return or could it happen either way. Sorry for being so dense but I want to be sure of what the possibilities are before I have anything done.

The lack of a return in the basement would lessen the likelihood that combustion appliances would "backdraft" (meaning fumes entering the house) when the HVAC is running.


If gas was being vented into the room would we smell it, or would we only know by physical ailments?

Carbon monoxide is an odorless, colorless, tasteless gas. It can make you very sick or kill you and you never know it was there. That's why it's called a "silent killer". The only time combustion appliances produce noticable odors is when they are not burning properly or have just lit off.


It's amazing how complicated HVAC can be.
I never realized the vastness of knowledge a HVAC person needs to be an experienced professional.

Spread that word around. Many people are just like you in that they do not realize the depth that a good HVAC person must go to stay afloat in this trade. No fault of your own, but now that you realize it I think it will help you understand the value of a good HVAC person when you find one.

[Columbus12]

At least I have a carbon monoxide detector a few feet from the furnace on the wall close to the ceiling however being exposed to lesser amounts of it over a long period of time is probably bad for us. This leads me to the most important thing I have learned from this situation. I learned that an unqualified or inexperienced HVAC person can actually arrange your HVAC in a way that could lead to negative health issued such as the return drawing gas from furnace or a return drawing in radon and moving it throughout your home. My house is the only house in my area that has (had ) a radon issue. I had a mitigation system put in 2 years ago. Now I'm convinced that our level was were it was because of the damn ceiling return (15x10). If, I only realized this return could be a detrement when the basement was finished in 1996.
Finally, thank you to everyone who offered assistance. I am grateful. I now know we're I'm headed and it's in the right direction.
Good job and keep up the good work.

[Shophound]

Please be aware that most store bought carbon monoxide detectors do not alarm until they measure a sustained level of 400 parts per million for what I believe is 30 minutes. 30 minutes exposure to 400+ppm CO can leave you not feeling well at all. If your detector has a digital readout that actually reads CO levels below 400 ppm (but does not alarm) that is helpful (but not ideal. You want the thing to go off sooner, if possible). No readout or a readout that just sits at zero until an alarm condition occurs = worthless IMO.

[Columbus12]

My wife, my two children and I have lived with this return for the last 16 years. Because the return is so close to the furnace, only three feet away, it would seem that have been exposed elevated carbon monoxide levels even though there is a louvered door just before where the return sits.
Therefore the individual who installed the basement heating and the inspector who okayed everything, have effectively taken years and maybe even decades off of my families life spans. I wonder how many other people will or have suffered health wise because of shoddy HVAC work. I'm now depressed and sad for my kids. It's time to get the word out to people in my community about this potential and the community need to find out whatever it can to determine whatever it can about other potential life threatening HVAC nightmares. The whole country needs to be awakened.

[Shophound]

I wouldn't go so far as to say your life has been shortened by anything we've been discussing here. Without an on-site analysis, we're only discussing what could be happening, not what may have actually happened. I've been in HVAC work a long time, and it was only recently that I attended a class on carbon monoxide monitoring and safety (taught by the Carbon Monoxide Safety Association, or COSA) because my trade training organization is involved with furthering the training of HVAC technicians. COSA is working hard to get this knowledge out so it is more widely known, but it takes time.

Energy auditors specialize in measuring what's known as the combustion appliance zone (CAZ) to see if what we've been discussion actually occurs in any given house or building. They try to create a worst case scenario to see if the appliances will backdraft. If this condition is found it needs to be corrected. The lack of understanding in this realm is widespread; many things are done in this life that may have consequences, but until the cause and effect relationship is found and spelled out, these same things are done without any direct fault (IOW, done in ignorance, with that "i" word connoting "lack of knowledge" vs. "stupidity"), until the facts are more widely known.

In short, your installer may not have had training where he knew going in that an open return in a basement could possibly lead to backdrafting appliances. Those that are trained and understand the ramifications are less likely to create a situation where what they've been advised to avoid is done anyway.

[Columbus12]

Ok. Based on what you saying I quess I am probably overreacting to the installers responsibility. As you state, he most likely hadn't a clue. However he wasnt the pro I thought he was because all he did was cut a hole in the duct, cut a hole in the ceiling dry wall, put a grill on it and called it a day. The ceiling opening is 1 and a half inches from the duct. He never sealed it.
A just had a HVAC guy seal it and close it off with sheet metal. He said the duct itself was "huge".
The basement negative pressure seems to be gone. Now, instead of the basement door closing when open an inch or two, it now actually blows the door slightly away from the basement. He said "that's a good thing".
I believe homeowners also need to be educated as to the "potential" dangers of such items as discussed here. Even though the "gas" from the furnace being sucked into a nearby return and it's health effects may be in the research stage, the homeowner needs to know there are studies taking place and that steps can be taken to test for it or to eliminate the "potential" risk. As long as the possibility exists that we "could" have even inhaling carbon monoxide over these past years is enough to take interest.

[BadgerBoiler MN]

There are other factors that can effect gas appliance draft including infiltration, bath fans, kitchen fans, open windows, unsealed duct work, the size of the return and other returns in the system, not to mention the fact that a forced air system should be balanced supply and return. Unless the return is isolated or there is a large imbalance in the the supply and return allowing the the house as a whole to go negative, I don't see the threat.

A proper blower door test would answer the question and many more.

Oh yes; if the appliances are burning correctly no or little CO is created, have them tested with a combustion analyser.

[Columbus12]

The company that put in my new HVAC sent a tech over who appeared to know his stuff. He did a mental calculation (in his head) whereby he concluded that the number of return vents on my first and second floors calculated out to my not needing the return in the basement. He sealed it with sheet metal etc. So, unless I unseal it and test the blower door I'll never know. The basement door no longer closes when furnace turns on so at least he got rid of the negative pressure from the basement. Nothing we can do now about any carbon monoxide emittance into our indoor air from the past.
Thanks for the info. At least their is the possibilities that we weren't exposed to long term low to medium levels...........

[PowerPlay]

The "path of least resistance" comment is valid. Return openings closest to the furnace tend to draw more air than the ones farther away from the furnace. Blanking the return in the basement may help cooling of the upstairs to some degree because the upstairs returns should draw more warm air out of the space.

Do you have a balancing damper in the supply duct to the second floor? If not, did your HVAC contractor install one? Directing more supply air upstairs would improve cooling of that space in summer.

[Columbus12]

No one ever mentioned a balancing damper. There is a lever on the side of the ceiling duct directly above the furnace. It can be turned upwards to "open" or downward to "close". Never really knew it was there. Kinda crude looking with the words open and closed written with magic marker or sharpie. When I pull lever to close something directly over the furnace shuts. Not sure if this is a balancing damper. Now that the basement return is closed (sealed)I can feel the supply vents on my first and second floors shooting air a good two feet or more where before the air could only be felt just a couple inches above the vent.
My basement return (now sealed) was only three feet from the furnace.