Noise is a ductwork undersizing problem. Fan speed may be set too high for ductwork available. Your solid door idea depends on a couple variables, 1. what does the furnace use as a return, is the return a hole on the side of the furnace with the filter there or does it go out into the house and have grilles in various locations 2. if the return is specifically in the closet, you need to have vents large enough to accomodate

Probably need a tech to come check return size and fan speed. Then they could recommend what you need for the solid doors. If you have a decent return system (which I doubt due to noise) then you wouldnt even need the door vents.

If the new doors have openings for air passage, then you will still hear noise.

If you change the doors then you will need to install a vent to bring in outside air for combustion. Make sure you hire someone who knows what he is doing. A mistake could be lethal.

Who should I hire? An HVAC Contractor? I called one today, and they said they do not add vents themselves but that they could come out and do a "diagnostic test" for $79 to advise best course of action. Still waiting to hear back from them.

I get people on occasion who think they know better or request this or that to a system that I have never looked at. I am the pro... tell me what your problem is without your opinion as to what you want. I can't work with people who think they know more than I do when I've done this for 22+ years. *SIMPLE* Silver bullet solutions do not exist very often for complicated problems that you've noted here.

So depending on how this initial conversation went with them may be the reason for the standoffish behavior by them. Time is money, a contractor doesn't have time to waste on things that go no where. I know this sounds like 'my way or the highway...' but what exactly are you looking for... a solution or more trouble?

You use a pro, because their opinion is worth what you pay for it. If you have a question after the fact then ask the questions. The answers to those questions should give you more confidence in your selection.

Everyone is looking for a 'simple solution' to their complex problem. How do you think or have come to the conclusion that a complex problem such as this can be remedied by simply adding a vent?

This is likely why you got the response you got. If not look for another contractor... but realize we are a slim minority from the list of companies out there.

I did have a major error in my previous post. I was thinking about return air and noise, and overlooked the fact that we are dealing with gas and also with the water heater. Both appliances need combustion air if they do not have dedicated intakes from the outside, so changing to a solid door w/ vents is not an option if you dont have a return that pulls air from the house not from the closet.

The best option for your situation, considering the furnace closet is not going to be moved and you still have this problem, is a real return system installed, along with dedicated combustion make up air in the closet and THEN a solid door.

You should still have the fan speed checked, if it can be lowered the noise goes down as well.

Vith, the fan speed cannot be lowered. Also, I don't understand what you're saying about the return...our furnace does not pull air from outside. So wouldn't it already have a return system that is pulling air from the house? We currently have louvered doors over the closet.

With new high efficiency heating systems and water heaters it is common for them to have a pipe (often PVC) running to the outside of the house to provide air for combustion. This increases efficiency because it does not pull in heated air from the house. It sounds like you do not have that type of intake. That means that your furnace and water heater must have a combustion air supply, which is probably why the doors are louvered. If you can find another way to provide adequate combustion air, you may be able to use solid doors and reduce the noise.

For example, I have a gas water heater in an interior garage cabinet with a solid door, and it has two vents/intakes into the attic above. I was required to have one high vent (a hole in the ceiling connecting directly into the attic) and one low vent (a metal pipe running from the attic down to the lowest point in the cabinet).

Bruce

When you speak to the HVAC contractor tell them you have a gas hot water heater and furnace in a closet and you need to provide outside air for combustion. If they can't do it then call someone else.

If would be helpful if you knew the gas input of the water heater and furnace (ex; 40K and 80K BTUs). This would give someone who is knowledgeable an idea of how much combustion air will be required.

If there were a new installation, using the interior air with louvered doors may not be enough. An outside air vent may still be required. But I suspect the typical HVAC contractor does not know how to determine what is actually needed for safe combustion.

Bruce, that is helpful, thanks. Right, I do not have an intake that brings air from the outside. It is a non-direct vent furnace. My understanding is that I just need two vents in the door, one at the top and one at the bottom. Hoping a solid wood door would not be a fire hazard?

Mike, when you say "outside air" do you mean literally outside? If so, that is not a possibility because of the type of furnace and where it is located in our house. That's my problem. Or do you just mean air from outside the closet? Right now it's getting combustion air from the rest of the house, through the louvered doors. My gas heater is 88,000 BTU. Not sure about my water heater, but it is 88 gallons. I would be surprised if an HVAC contractor would not know what is needed for safe combustion. How DO we determine how much ventilation is needed then? My furnace closet in its current state passed inspection before we moved in, so that tells me that louvered doors bringing interior air are enough right now. This is a non-direct vent furnace which means outside air is not an option.

You need to know if return air is only in the closet as well. If it is, then you can NOT use a solid door period.

I do mean air coming from the exterior of your house. Is there a way to install a PVC pipe so it can make its way to the outside? It can go out the side of the house or through the roof, even a ventilated attic.

Using the air within house is OK but it is limited. If you reduce the air going into the closet then you potentially have a problem. Having outside air coming in give you peace of mind that a sufficient amount of oxygen (what is required for combustion) will enter the closet.

A 88 gallon hot water heater! That is a serious amount of water heating. A your sure it is that big? If we assume it is, then the input must be at least 75,000 BTUs. Add that to the furnace and you have a total of 163,000 BTUs. That is a lot of combustion to stuff into a closed with louver doors. You should install a carbon monoxide detector to make sure you currently don't have a problem.

You would think professionals would know if your set up is safe or not. In order to make that judgement they would have to do a calculation and determine how much air is entering your house. Most don't know how or can't be bothered to do the calculation. The amount of air entering is difficult to determine without elaborate testing. At best they will make an assumption which may or may not be accurate.

Actually Mike, upon looking again, the water heater is 50 gallons. I also called the company that provided my water heater (AO Smith), and they said my model is 40,000 BTU. We do have a carbon monoxide detector installed in the kitchen (which is right next to the furnace closet). It has never gone off. We have an extremely open floor plan downstairs.

It's not a fire hazard to put a solid wood door on the entry of a closet that houses a furnace / water heater. There are safety controls for the water heater as well as the furnace that would shut it off in the event a fire related problem occurred.

With that said you don't want to store combustible things near or around any gas fired appliance... things like oily rags, varnish rags, rags with any amount of combustible material.

The hazard is putting these appliances in places that do not have the proper ventilation required to provide enough combustion air for both appliances. If the combustion air opening is only sized for one appliance, when both run there isn't enough combustion air and CO -carbon monoxide is produced as a by product of the combustion cycle as opposed to carbon dioxide.

This is another reason why installing gas appliances within the envelope of the conditioned home an extremely poor idea.

Carbon monoxide is a colorless odorless gas. In high concentrations it's death. Pets, the elderly and children are affected first. This is nothing to play around with.

Austin -- I understand that installing them in the middle of a home is a poor idea. But I'm not the one that put them there. It's what I have to deal with. Relocating is not an option. I also understand that combustion air is important. That's why I'm asking all of these questions and have contacted 3 HVAC contractors to give advice. I'm not playing around with anything. As a reminder, my original questions were: is hanging solid doors a possibility? If so, what size vents would I need?

Things become poor ideas if they are installed incorrectly.

"The furnace/AC is very low efficiency, so it is extremely loud and annoying. The previous owners installed this unit in 2014, right before we moved here."

Noise has nothing to do with efficiency. If it was installed in 2014, it had to meet minimum efficiency standards for your region.

Your best bet is to look on the side of the furnace for the name of the installing company and call them telling them your concerns and see if there's anything they can do to help.

Curliegirlie1189

The statement about placing the unit within the structure was not directed at you... I was highlighting a discussion from another thread unrelated to this one. So I realize this was likely not your decision. With that said, that information doesn't hurt you for future reference.

I'm not playing around with anything: It's hard to ascertain what someone is doing from a forum board in which a lot of DIY's come to garner information for this or that. I can't count the number of times this occurs. I can only guess based on statistics of others who have come here before you.

Conclusions many times are drawn from the topic of the post - the header of the post. You state you are looking to cover up sound related issues, by sound proofing. In other words let's ignore why the sounds are there and just cover them up.

Air noise most of the time relates to design of the system. Improper designs will produce more noise. This is most likely due to high static pressure being placed on your system when it runs.

Design related problems can be a challenge to over come. I am not there... so with the information you have provided I can only guess.

Guessing never leads to anything good. Combustion air is important which is why I posted the warning about it. The last thing you want is a quiet system that kills you in your sleep or makes you really sick.

Noise has nothing to do with efficiency. Yep. It has to do with the sum of the parts of your system. (duct system included)

an 80% gas furnace with multi tap blower will be a bit noisier than an 80% gas furnace with variable speed blower.

Neither are virtually quiet... noise is very subjective. How loud is loud?