DIY solution to stay warm this winter and watch TV

November 7, 2010 6:36 PM

My gas furnace air intake is too loud. Am I doomed to adjusting my TV volume every 15 minutes for the rest of the winter?

The furnace in my 600 sq ft apartment is really loud and I'm looking for a solution to dampen the noise of the air intake vent. When I first moved in my landlord had a furnace guy look at it and apart from tightening some bolts on the fan he couldn't do anything. He said that its a cheap, old heater and they are just loud. My landlord is great about fixing things as long as they aren't too expensive and I can't ask him to put in a new heater just because its loud.

I have a lot of windows and even with weatherproofing and using a programable thermostat the furnace kicks on every 15-30 minutes (I keep it at 60-68). Since I work from home I hear it all day and often can't hear the music on my laptop in a different room when I'm sitting right next to it.

I've lived here a few years and am annoyed all winter long by this. It looks like I'm going to have to relocate my couch or TV right next to the vent this winter as well, which means turning the TV up more than double the volume when the heater is on, only to have it blasting when the heater turns off. Neighbors haven't complained but sound travels really well through the wood floors.

The air intake vent is located on the floor and is where all of the loud sound is coming from. Googling tells me to relocate the furnace and ductwork or to slow down the fan speed. I'd like to build a removable/non-permanent box around the vent that can muffle the sound but not impede air and break my furnace. Any ideas for what I can use and how far it needs to be built out from the vent? Other suggestions besides turning off my heat all evening? I'm in Chicago (cold winter) and have a wall of cheap double-paned windows in a 1930s brick building.

Here's my furnace in a pantry next to the living room and here's the air intake vent that's causing all of the problems.

posted by Bunglegirl to Home & Garden (21 answers total)

Is that your thermostat in the corner?
posted by lee at 7:01 PM on November 7, 2010

I've had exactly this problem in Chicago apartments. The problem is that the intake/return is placed too close to the furnace unit -- so the noise of the fan rattles right out of the intake and into the room. Is there even any ductwork at all between the furnace and the intake in your place? It looks like no. Most of the sound dampening solutions that I saw on the web involve putting "baffles" in the duct leading to the intake, but that won't help if there isn't a duct.

I have a feeling that building a box around the outside of the vent is not going to be feasible because anything that really dampens the sound will also restrict the airflow too much, which will burn out the furnace motor, eventually. (Though maybe "eventually" does not matter much in a rental?)

Maybe buy a really nice space heater? The sealed "radiator" kind are silent and run $100 or less.
posted by Mid at 7:05 PM on November 7, 2010

So what's the noise? Rattling from the vent itself? The ductwork?
posted by bonobothegreat at 7:06 PM on November 7, 2010

Response by poster: Yes. When I moved in it was an old 60s style hand-turn thermostat and I had it changed out. I know that its in a horrible spot, probably the coldest spot in the apartment. My heating vents are in duct work in the ceiling and the heat doesn't make it all the way down to the floor, unfortunately. This is an old building retrofitted to have central heat. I've though about putting magnetic clear plastic something over the vents to direct air down but haven't gotten around to looking if that sort of thing actually exists.
posted by Bunglegirl at 7:07 PM on November 7, 2010

You'd need to build a baffle box. The problem is the cross sectional area of your grill area needs to be maintained so the box is going to be huge (IE: minimum size would be (width of the grill) X 2x(height of the grill)X 2x(width of the grill). Larger would be better.

One thing you might be able to do is adjust the differential of your thermostat to a wider range. This won't reduce noise or run time but it'll reduce the number of cycles that happen per time unit. Also if your windows are drafty then reducing the loss through those windows with plastic and or heavy curtains would reduce the run time of your furnace.
posted by Mitheral at 7:07 PM on November 7, 2010

Response by poster: I do hear a rattling and roar of the furnace when it turns on but the loud sound is the noise of air coming though the intake and, I presume, the air intake fan.

Mid - you're right. There is no ductwork to insulate. The furnace is installed right against the wall with a hole cut out of the drywall and a vent shoddily placed over it. The vent isn't even in the drywall, its built out with a few pieces of wood to allow for a filter to slide in. Once I put something in front of it and it sounded great but the heater turned off and wouldn't re-start for a while—I learned my lesson. I was hoping if I built the box out say, 5 inches, and added some sort of felt-type sound absorbing material but left a few holes or slits for the air to come in it might work.

I'd prefer not to run an electric space heater. Besides safety (and I think they're banned on my lease, technically), that's going to be a high bill for heating a small area. The rest of my apartment would get really cold and I'm supposed to keep it heated to 50 for the pipes. I usually leave it on 60 as it is.

Mitheral - a baffle box has to be that big, really? The vent is 22" square, but the filter and hole in the wall is 16x20". I'll look into the differential. Although the thermostat is programmable it isn't a nice, highly customizable one and I don't think that is an option but I'll take another look.
posted by Bunglegirl at 7:17 PM on November 7, 2010

I'm supposed to keep it heated to 50 for the pipes. I usually leave it on 60 as it is.

....This may sound counter-intuitive, but...maybe setting the thermostat higher? Say at 65?

Go with me a second - if your thermostat is low, then it doesn't take long for your heater to bring things up to that temperature, and so it only runs a short amount of time before shutting off. And then the temperature drops again and it switches on again...for just a few minutes...and goes off again. However (and I'm really kind of speculating here), if you set your thermostat at a higher temperature, it would have to run longer to generate more heat to bring it up to that level...heat which would then stay around longer, so it wouldn't switch on again as fast.
posted by EmpressCallipygos at 7:32 PM on November 7, 2010

you said you weatherized. did you put up plastic on your windows? today's clear plastic is really clear and can still allow you to see out your windows.

i had a similar problem a few years ago in a small coach house i rented. putting plastic on my windows reduced the time in which the heater kicked on. i still had noise, but not as much of it.
posted by lester at 7:39 PM on November 7, 2010

Replacing the existing grille with something that is more open will help reduce the wind noise that you're hearing.

Try running the furnace with the grille completely removed to see if that helps (the furnace filter will prevent anything from getting sucked into your furnace for this temporary test)

If this helps, then I would work at building a new, less restrictive grille out of some expanded metal. A piece of this in a wooden frame would give you lots of airflow while preventing the cat from getting sucked into the furnace.
posted by davey_darling at 8:06 PM on November 7, 2010

However (and I'm really kind of speculating here), if you set your thermostat at a higher temperature, it would have to run longer to generate more heat to bring it up to that level...heat which would then stay around longer, so it wouldn't switch on again as fast.

This is not how heat works. Heat is not momentum (ie the faster you drive your car, the further you can coast) -- it is more like water in a leaky bucket. No matter how hot you make the house, the bucket still leaks.

I was hoping if I built the box out say, 5 inches, and added some sort of felt-type sound absorbing material but left a few holes or slits for the air to come in it might work.

You need to maintain airflow. A few holes or slits is not sufficient. Right now it has 16x20 inches (320 sq in) of airflow; reducing that to 20 or so sq in of holes or slits will choke the poor furnace.
posted by Forktine at 9:01 PM on November 7, 2010

Best answer: The best you can do is (as mentioned above) make a 'baffle box.' This is not really a big deal. Imagine a box 1/4 again as high, half again as deep (as the grill is wide), and half again as wide. And really, you could probably get away with just a top and two side.

One open side goes against the wall where the grill is. The adjacent into-the-room side, is also open. (They make 'boxes' like this these out of 'duct-work', pressed tin, and they have a 'felt-like' lining which helps with the noise issue. As I doubt you have access to a tin-knocker/ duct shop (though one should be easy enough to find) you'll probably have to get it built out of ply-wood (which will look better anyway) and line it with some kind of noise suppressant foam (or even egg-cartons). A duct one really would look like hell.)

Now, at the opening into the room side you could put a baffle. A baffle here would just be a piece of wood extending from the top to the bottom of the enclosure and extending into the enclosure at approx. a 45degree angle (like a half-open door). Make sure that the area between the inside edge of the baffle and the nearest baffle-box wall, this opening, has an area that is at least a little bigger than the area of the original furnace grill (so if that grill is 24X24 inches, the opening the baffle leaves has to also be at least ~590 sq. inches.) Also, the baffle should not occlude the grill any more than absolutely necessary. Constricting the airflow will screw up your furnace and might make a whistling sound that will put you completely around the bend.

Just putting a corner or two for the sound to get around should go far far far towards keeping it out of the room.

Good Luck!
posted by From Bklyn at 1:03 AM on November 8, 2010

Best answer: You could build out a long box that would double as a window seat. Then you could put a whole bunch of vents in it along the floor and at the end. Put a cushion on top of it and you should have a pretty good sound-deadener.

Maybe $80 in materials if you use all really nice plywood.
posted by chazlarson at 1:05 PM on November 8, 2010 [1 favorite]

I would ask the landlord if they could move the thermostat, which I am surprised whoever looked at it before didn't suggest or just do it!
Being next to the window, on an outside wall, in the corner, and just about in the path of the return stream (it's in the path of the cold air) makes it difficult to get a read on the temperature. It probably makes it run more often and for longer stretches.

It would be pretty easy to move it at least to the other side of the intake vent as far down the wall as possible. If I am picturing your place correctly, the wall behind the intake is the utility room and it would be pretty simple to run the wires there and put it through the wall wherever you wanted.
Good luck!
posted by lee at 3:23 PM on November 8, 2010

Response by poster: Baffle box: I'm trying to picture From Bylyn's baffle box suggestion but I'm not quite there. I'll need to look at a diagram to get it right. The box would have to attach only on the outside of the wall with the air intake as the furnace is literally right against the wall. Its actually how mice are getting in my place and we boarded up all the cracks running along the furnace up to the ceiling to stop them coming in there. Point is, there's only an inch of space between the wall and furnace so I can't build anything in there.

Vent mod: I'm trying to get the vent off to see if its quieter but the screws are stripped (and put in at an angle, ugh). These are times when I wish I had my own place so thing were done right.

Decorate it: The window seat idea is great! Except... that's where my new 93" sofa is supposed to go and the room is only around 10' wide. As you can see in the floor plan, my current TV is the farthest it could possibly be from the intake and its loud even over there. Its even woken me up at night and I'm not a light sleeper.

Thanks for all of the comments, its helping me brainstorm...

Weatherproofing: I do use plastic window coverings, draft dodgers on the doors, etc. but almost my entire north wall of my apartment is windows (awesome for light, not so much for warmth). I can mention moving the thermostat to my landlord but that might seem extravagant to him.
posted by Bunglegirl at 4:45 PM on November 8, 2010

Best answer: Maybe instead of a window seat it becomes a "coffee table" along the same wall as the vent. Line it with fiberglass insulation for extra Sound-Deadening Power.

Moving the thermostat is something you could do yourself and then undo when you move [assuming the thermostat is a regular one connected only to that furnace and not wired into some building-wide system].

There are wires going from the current thermostat to the furnace. Disconnect them at the furnace. [take a picture before doing anything, print it, and tape it to the furnace for future reference]

Go to Home Depot and get a new thermostat and some wire [$40-50]. Mount it on the same wall as the vent, closer to the middle of the apartment, poking a tiny hole through the drywall to run the wires. Run those wires alone the wall to the furnace and connect them like the original ones were.

When you move, restore the old wiring and patch the tiny hole in the wall.
posted by chazlarson at 6:37 AM on November 9, 2010

Window box/ coffee table is a very good idea as it gives you more lee-way with your dimensions and thus a better chance you will not be affecting the performance of the furnace by constricting the return airflow.

It could also look ok, and be useful - win win win.
posted by From Bklyn at 1:00 AM on November 10, 2010

Response by poster: Thanks for the great ideas. I'm going to work up a design for a baffle box/side table.
posted by Bunglegirl at 10:59 AM on November 10, 2010

Response by poster: I looked at my options this weekend and was wondering what to put inside of my wood box to deafen the sound. My boyfriend thinks pink insulation board is the way to go (if so, how thick?) but the guy at Home Depot didn't think it would help with sound. Granted, most people at Home Depot don't seem to be very knowledgeable these days. I realize that I'm going to have to see for myself but will take any suggestions.

Insulation, carpet remnants, egg cartons...? Sure, some special "sound proofing" material would be great but I'm not willing to put that kind of money into this.
posted by Bunglegirl at 4:14 PM on November 16, 2010

You want something soft with lots of air pockets in it to deaden the sound. Rigid pink board won't do that.

If you look at the sort of thing that is sold for sound-deadening purposes, you'll note that the common thread is that they're all soft and "fluffy".

The easiest thing would probably be standard fiberglass insulation. It's thick, sound-absorbing, and cheap.

I've got a pile of carpet and carpet pad remnants sitting in the garage you're welcome to use. ;)
posted by chazlarson at 12:02 PM on November 17, 2010

You don't want to use ridgid foam (or pretty well any foam for that matter) insulation for this purpose. The byproducts when foam burns are pretty poisonous so it should always be covered by something less combustible.

Standard fibreglass insulation is a poor choice to because the binders aren't all that good; hence the warnings to wear a face mask when you are installing it. You'll be blowing tiny little shards of spun glass into your living space for weeks which will float around in the air for hours.

Carpet would be decent or they sell special duct lining insulation that also acts as a sound absorber. Easier to haul around than carpet would be a couple sleeping bags or quilts from the thrift store.
posted by Mitheral at 7:18 AM on November 18, 2010

Yeah, that could be a problem with fiberglass. I suppose a guy could mitigate it by installing the stuff such that the paper side is lining the air channel so the air that's being pulled through the box is not actually travelling through the spun glass, just through a tube lined with spun glass. Also, this is an intake, not an outlet, so a high-quality filter on the furnace intake may catch any stray bits. Mitheral's right, though, that it's probably better to avoid that risk altogether.
posted by chazlarson at 11:16 AM on November 18, 2010