Darkroom ventilation fan

[BetterSense]

I want to put a ventilation fan in my 8x8 2nd story darkroom. I was going to put in a bathroom exhaust fan but it seems like a better option might be to install a fan in the attic and run ducting down to the actual room. I don't see any reason why the darkroom can't be vented into the attic. I know that if the fan is noisy I will never use it because I like my darkroom to be quiet, so having a fan installed in the attic seems like a good solution compared to the bathroom fan. The problem is that I don't know where to get a fan like this or what it would be called.

[Shadowtracker]

I use two fans often. One is in the ceiling, a bathroom exhaust fan - it's tied into the dryer vent and I made my own closure so the exhaust doesn't go into the dryer. The second fan is outside the darkroom, and I made my own duct; it goes into a hole in the wall that is light tight. I caulked around the duct at the wall joint. This arrangement pushes fresh air into the room, while the exhaust fan pulls it out. The blower motor is a squirrel-cage arrangement. I have 1/4" hardware fabric around it so the cat doesn't get chewed up by it. I plan on building a work table over the top of this, then staple the hardware fabric to some legs. Right now, I have a filter on the inside of the darkroom for dust control and it works great. Once the work table is made, I will have three filters on the outside part of the hardware fabric so there is plenty of air flow, and I will retain the filter that is inside the darkroom as a secondary safety. The squirrel cage blower pushes air into the room faster than the vent fan can pull it out, so there is a positive pressure inside the room when it's in use. I don't have any photos of this arrangement, but can take some and send them to you if you like.

[DanK]

Sounds like you are looking for an 'in-line' fan.....

Here's an example....

http://www.grainger.com/Grainger/BROAN-Ventilator-4TR47


Thanks,
Dan

[Jon Shiu]

You can get very quiet bathroom fans. They all have sound level ratings that you can compare. Of course the quiet ones are a bit more expensive, and larger.

Jon

[Keith Fleming]

In our area, the local building code requires every home to have a "whole house fan" that runs on a timer (located in a hall closet) every day and gradually exchanges all the air in the house. It's a rather strong exhaust fan, and not very noisy. For those reasons, I installed one of them in my darkroom, but on a wall switch rather than a timer, and ducted it outside. There's a light-tight louver in the darkroom door to allow air to come in when the fan is running. I mention this only because a bathroom fan is rather puny when it comes to actually moving air.

Having a fan venting into an attic doesn't seem like a good idea to me. It could increase the humidity in your attic, and the fumes may diffuse into the rest of the house.

Not sure if this is useful info. Good luck in working out the best solution for your situation.

Keith

[Louie Powell]

I want to put a ventilation fan in my 8x8 2nd story darkroom. I was going to put in a bathroom exhaust fan but it seems like a better option might be to install a fan in the attic and run ducting down to the actual room. I don't see any reason why the darkroom can't be vented into the attic. I know that if the fan is noisy I will never use it because I like my darkroom to be quiet, so having a fan installed in the attic seems like a good solution compared to the bathroom fan. The problem is that I don't know where to get a fan like this or what it would be called.

The only concern you might have about venting directly into the attic is that if you are in an area with very cold winters, you might not want to put any additional humidity into the attic that could freeze, and then later melt to create free water.

There are two ways to ventilate a darkroom. One way is to use negative pressure - use a fan to exhaust air from the darkroom. That works, BUT the issue is that the air that is withdrawn must be replaced. And as that replacement air enters, it can bring dust and other undesirable things.

The alternative is to use positive pressure - force air into the darkroom (through a filter), and allow it to flow out as it will. That does a better job of managing dust.

As far as remotely mounting the fan - I'm a strong advocate of that for the very reason you cite - noise. I have positive pressure ventilation in my darkroom. The fan is mounted on a sheet of plywood installed between the ceiling joints outside the basement darkroom. A second sheet of plywood closes off the joist space about a foot away, and I have a furnace filter over the bottom of the joist space to filter the air. I use vinyl ventilation duct originally intended for use with bathroom extractor fans to connect the fan to a small louver inside the darkroom.

I bought a fan at Radio Shack. It's a computer-style 'muffin fan', only it operates at 120v rather than the much lower voltage that is actually used inside computers. It's rated at 300 cfm and provides a reasonable interchange of air; but the design of my DIY between-the-joists plenum allows for adding a second fan (in parallel) if I ever want to increase air flow. And the fan is far quieter than bathroom extractor fans.

[BetterSense]

Since I work in semiconductor cleanrooms I'm familiar with the benefits of positive pressure. I just haven't figured a way to set it up. The air coming into the darkroom needs to be clean and heated/cooled, and it has to be a substantial volume if it's to force out air in the room satisfactorily. My darkroom is a converted closet, with no HVAC ducts running in, so that's a problem in itself. I figured if I had a good exhaust fan in the ceiling, then at least I could turn the fan on to exhaust chemical fumes and I could open the door and let it draw in fresh air from the room next door. I can't very well pump air in from the attic.

I live in Texas, so there's no cold weather to worry about, and my attic is very well ventilated and insulated with blow-in insulation. There are 3 of those big turbo vents in the ridge, and when I was up there wiring up the outlets, there was actually a breeze up there from the eaves to the ridge vents.

[John Powers]

This is a post I made here in 2009. There have been no problems with the system since then.

" I built my darkroom 11x13 feet by 7’ 2” height in 2004. I have bad allergies, wanted a good flow of clean air, and quiet, either as quiet, or as not intruding on a good sound system. Every bathroom fan I had heard was noisy and for me irritating. Many had very short life spans. Someone recommended Panasonic fans. I must admit that I had thought of Panasonic as sound and video systems.

All wall and ceiling joints are sealed with tape to avoid dust. The door has rubber insulation around it. I bought two inline fans that fit in the rafters. I used white septic system 4” PVC pipe coming down from the sealed rafters to an 8 foot sink along a basement wall. The two pipes come down to points at 2 and 6 feet at the sink back. The pipe on the developer, stop, first fix side of the sink has a T opening taking air in from either side of the pipe. The wash, second fix pipe has a curved 90 degree opening pointing at the second fix. The fans exhaust two feet to the outside through drier type trap doors. One does not want summer bees visiting the darkroom.
(To clarify. I have two exhaust fans and one input fan)

Air coming into the room goes through a high quality furnace filter into a wall fan on the wall opposite the sink. The fresh air comes by me over the sink and trays when I am standing at the sink. The fans are so quiet that I only hear moving air in the PVC pipes. There have been no maintenance or service problems in this time. The fans were mail ordered from a CA building supply distributor.

If you get up to the Cleveland, OH area you are certainly invited to have a look.

http://www2.panasonic.com/consumer-e...00000000005702
(this link valid as of April 2011)

John"

I would agree with the suggestion not to vent into the attic. Duct work to an outside wall with a drier vent type self closing door would avoid excess moisture and possible dry rot in attic wood.

[BetterSense]

The link actually doesn't work at all. I have family in Cleveland FWIW.

[William Whitaker]

Since you're concerned about noise level (and I can sympathize with that), you might want to consider that your system will be a lot quieter if you try to move a large volume of air slowly rather than a small volume of air quickly. Remote mounting of the fan is a good idea. But the longer the duct run, the more powerful your fan has to be to move the same volume of air. And that leads to more noise.

In the past what I've done is to use a positive pressure system very similar to that suggested above. I remote-mounted an old furnace blower in an adjoining room (a closet actually) to push air into the darkroom through a duct which was both short and had a large cross-section. Since the blower was overkill for one room, I changed out the belt pulley to slow it down. While this may sound more like Tim-the-Toolman engineering, the system worked extremely well. I could still hear the fan, but the overall noise level was not intrusive and the frequency of the noise was more of a rumble than a screaming banshee.

The air was exhausted directly outside through spring-loaded vents which kept the outside air from blowing in when the fan wasn't operating. Inside the darkroom with the fan on there was a detectable change of air in the room (but no wind!). Of course, with such a system you have to be concerned with a source of make-up air and in the winter that may overtax your furnace and your heating bill. But maybe not so much in Texas...

[BetterSense]

The adjacent bathroom has a closet on the darkroom wall. I could mount a blower in that closet and have it blow into the darkroom. The thing is I would have to leave the closet doors open to provide any air to the fan and I'm not sure that would have acceptable WAF. I appreciate all the suggestions.

[William Whitaker]

The adjacent bathroom has a closet on the darkroom wall. I could mount a blower in that closet and have it blow into the darkroom...

There may be times you don't want to use that fan. I haven't found a filter that good yet.;)

Since I'd given my closet over almost exclusively to being a fan housing, I replaced the door with a panel of 3/4" melamine-clad MDF in which I had cut a hole for a large (16x20) filter frame which took standard readily-available furnace filters. Because i would need to get into the closet to service the fan, I devised some homemade latches. It was cheaper than trying to replace the door. I also weather-stripped the whole thing so the air draw would be restricted to the filter opening.

From the outset that darkroom was designed with the idea that I would eventually have to sell the house. In spite of the fact that it was a full-blown darkroom (no pun...), everything was done so that it would be easily revertible. Drywall was cut on stud centers to make repairs easier. When possible, things were surface mounted. Sheets of 3/4" melamine-clad MDF were mounted to the studs. Plumbing and electrical distribution was then attached (in many cases bolted) to the MDF.

But I digress. I probably had more fun designing that darkroom than I did actually using it. I miss it. I'll probably never have that nice a darkroom again.

[John Powers]

The link actually doesn't work at all. I have family in Cleveland FWIW.

Sorry. It worked in the file where I copied it from. Odd that it would not work when copied.

Try this.
http://www2.panasonic.com/consumer-electronics/shop/Building-Products/Ventilation-Systems.75111_11002_7000000000000005702

It works here as of this posting.

We are holding the above mentioned "family in Cleveland" hostage until you are satisfied with the link.

John

[Drew Wiley]

Venting moist stinky air into an attic in any climate is a very bad idea, even if the attic
has a certain amount of cross-flow (as all should have). But you can mount the fan in
the attic and ventilate it to the outdoors. This accomplishes several things. First,
air can be pulled more efficiently than pushing it. Second, having extra efficiency will
allow you to design a better light trap to the ducting. Third, this will isolate the noise.
I have a very high opinion of Panasonic inline fans. You can barely hear them and they
seem exceptionally durable.

[John Powers]

....But you can mount the fan in
the attic and ventilate it to the outdoors. This accomplishes several things. First,
air can be pulled more efficiently than pushing it. Second, having extra efficiency will
allow you to design a better light trap to the ducting. Third, this will isolate the noise.
I have a very high opinion of Panasonic inline fans. You can barely hear them and they
seem exceptionally durable.

The Panasonic inline fan linked to above fits between the rafters giving you a direct shot to two outside walls. Just duct from the fan to the outside wall, cut a hole, hang a drier door on the end of the duct.

Do not make the standard mistake of putting the exhaust fan duct right over the sink. Fumes come up from the trays, pass your nose and exit the room. There is a reason you are installing an exhaust system. Don’t defeat it. Drop duct work down to the opposite side of the sink from where you will be standing. I use white 4” PVC sewage pipe. Bring fresh air into the room behind you. The fresh air will pass you, go over the trays, fumes will go into the collector duct and by pass your nose.

John

[John Powers]

I received a PM asking for clarification of my set up. I will post the answer here in case I was not clear to everyone.

My 11x13 foot basement darkroom has an eight foot x 30” stainless steel sink along the 11 foot exterior wall. The two inline exhaust fans are in the rafters above the sink at about 2’ and 6’ of the 8’ sink. PVC pipe comes down from the ceiling, along the outside wall, to a point just above the wall side of the trays. Fumes are sucked up the ducts from the edge of the trays opposite me. At closest I am standing 30+ inches away from the duct side of the sink. The fans send the fumes horizontally through the outside wall to drier type one way trap doors.

On the opposite wall, 13 feet from the above mentioned exterior wall, I mounted the wall fan in the link. It draws through a furnace filter to clean out any dust coming in from the rest of the basement. That fresh air crosses the room behind me, passes around me, and goes out the two exhaust pipes.

To avoid any dust coming in the room I paneled the walls and ceiling with white 1/8” board that has a smooth plastic surface. I think it is called Melamine. All joints in the board were sealed with white duct tape. It is not elegant, but it keeps out any dust in the rafters or walls. I vacuum the room frequently before printing. I develop film in a Jobo so that eliminates much dust from that process. I use well water filtered to 3 microns.

I hope that clears up questions. If not please ask more.

John