Cutting a bathroom exhaust fan through vinyl siding?


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Old 11-11-09, 09:02 AM
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Cutting a bathroom exhaust fan through vinyl siding?

Hi everyone,
I am new to this website and need a little help. Currently I have 2 bathrooms on the second floor. Both of the bathroom exhaust fans are currently vented in the attic to the soffit. But they never actually cut a hole in the soffit. They just ran that flex tubing over and sat it on top
of the perferated soffit. My house uses the soffit and ridge vent for attic ventilation. I have read running the bathroom exhaust over to the soffit is a bad idea when you attic is ventilated this way.

So I had an energy audit done at my house. They recommended getting my attic air sealed and running the exhaust fans out the side of the house. There is plenty of room to do this.

But my house has vinyl siding and I am concerned how they are going to install this new vent. I want to make sure it is water tight. Well as much as it can be with vinyl siding.

I plan on asking these contractors how they are going to install this vent before letting them cut holes in my house. If I don't like there answer then I will tell them to forget it.

So what are the steps to properly install a vent through vinyl siding? I have read about vinyl surface mounts???

Help.
 
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Old 11-11-09, 09:41 AM
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Old 11-11-09, 01:51 PM
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Easiest and neatest way to cut the hole for the vent is with a hole saw (either 3" or 4", depending on the size of vent you will be using). That will go through the vinyl and the underlying siding. sealing the vent to the vinyl is simply a matter of caulking it with silicon.
 
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Old 11-11-09, 06:30 PM
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..not too many ppl have a 4" hole saw.. but you can do this neatly/cleanly...with a little care and a sharp 'Olfa' blade/knife...Dont rush it.. it wont cut sharply like a saw on wood..but you can do it... Cut it snug, then caulk the perimeter..either with white silone or clear...(depending on the color of your siding..- white for white siding..clear for anything else...Unless you can find a color match....-uh ..slim.)
 
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Old 11-11-09, 07:26 PM
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Jatco said it, in R.D., two different types of block. Don't just drill a hole and expect caulking alone to keep water out. The different thicknesses of materials on the wall will expand and contract differently, not together. The contractor should use some backer rod to make a bridge so the caulking can stretch at the attached ends: Exterior siding, trim, and finishes - Google Books
If a solid block, flash the cut above the block to shed water. Don't use 3" if you have the option (your local building department will know):

"What is the duct’s diameter? Fan exhaust ducts
should generally be a minimum of four inches in
diameter to be effective at moving air. Three-inch ducts
were commonly installed in the past. Upgrading to a
larger diameter duct should improve fan performance.
Is the duct smooth metal or is it “flex duct”
a flexible metal with spiraling ridges? Although
flex duct is often used, smooth metal ducts move air
more effectively than flex duct. A fan connected to flex
duct has more resistance to overcome and moves less air.
Small diameter flex ducts cause the most problems. If
your fan is connected to three-inch flex duct, it probably
doesn’t work very well. Changing to four-inch smooth
duct should greatly improve performance. If flex duct
must be used, make sure it is at least four inches in
diameter, kept as short as possible, and installed with no
dips or droops." From: http://www.pse.com/SiteCollectionDoc...S_Moisture.pdf
Be safe, Gary
 
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Old 11-11-09, 07:59 PM
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I haven't followed any of the links mentioned above, so in case it isn't covered in the links, you don't usually want to install just "any" dryer vent in a house with vinyl siding.

To do a neat, professional job, I would either want to do 2 things. 1). get a dryer vent that has a vinyl siding snap ring. (that matches the color of your siding exactly) To install it, drill a small pilot hole all the way through the wall and thru the siding. Drill the 4 1/4" hole (which your contractor or HVAC guy should have) through the siding and sheathing... then go inside and complete the hole through the drywall, insulation. The vinyl siding actually gets removed around the vent, half of the dryer vent ring goes on around the hole, the hole gets cut the right size to go around the vent ring, the siding gets reinstalled and then the snap ring goes on to cover up the cut edge of the siding. (No caulking required). It's basically like a tiny window opening in the siding. Flashing can be installed before the siding is reinstalled to kick water out over the nailing fin of the siding below... but very few people think to do that. Most houses are covered in housewrap (a WRB- water resistive barrier) and any water that gets behind the siding simply runs down the housewrap and leaks out around the bottom course of siding.

The 2nd thing they could do is remove 1 piece of siding and install a mounting block (square 6x6 block of wood) where the dryer vent will go, clad it with trim coil to match the color of your siding and then drill the dryer vent hole through that. The mounting block gives you a flat surface to mount a standard dryer vent to. You would j-channel around the block just like you'd j-channel around a window. Then cut the siding to fit and reinstall it.

The thing I hate to see is a standard dryer vent, which works fine on a flat surface, stuck on top of vinyl siding, overlapping one or more ribs on the siding, and a lot of ugly mismatched caulk slathered around the outside of it. Not that a plumber would ever do that... but you never know. A lot depends on the size of siding, the location of the hole, whether it can lay really flat or whether it's on the ribs or not.

As another idea, they do make roof vents for dryer exhaust which would probably be a lot better solution if the vent is currently already in the roof.
 
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Old 11-12-09, 07:10 AM
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XSleeper,
Thanks for that info. I have been reading alot of stuff on the internet and you get conflicting answers. But those were probably the most complete answers I found. Currently both bathroom fans go up in the attic and are vented directly onto the vinyl perferated soffits that are used for the soffit venting in my attic. I would rather not go through the roof because I live in New England and I don't know how those work when you have 2 feet of snow on your roof. Also I don't like the idea of blowing warm air onto my roof when there is snow on it. This could possibly cause an ice damming issue which is a big concern where I live.

Both fans are located less than 5 feet from the exterior wall in the attic. So the duct run will be nice and short.

The reason I am so concerned about this is because I believe the builder never flashed the windows properly when he installed them. I have not had a leak in the house yet. But he used the J channels to go around the window and I don't think he used the ice/water shield before putting the siding on around the windows.

I do have a reliable siding/windows guy that is going to take a look at the windows when Spring rolls around.

So I am going to grill these guys when they show up to vent the fans. If I don't like their answers I am going to tell them to forget it and get my own guy to do it in the spring.

Is there anything else I should ask these guys before letting them cut holes in my house????
 
 

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