Bathroom Fan

Big Gaping Hole

Big Gaping Hole

May 17, 2015

Installing a Bathroom Fan
Or
How to Cut a Big Gaping Hole In a Perfectly Good Wall

I finished putting up my siding before Christmas and I have to say that it continues to bring me great joy to see it. Seriously, it really looks good. That’s why it breaks my heart a little bit to have to cut a hole in it. Actually, the design of my house requires that I cut two holes in it, neither of which I’m terribly happy about. The first hole is for the water feed for my water tank. Since it is a gravity feed, it has to be higher than the tank which means it has to go through a wall. All the other lines that need to go in or out of the house can be run through the floor except one: the bathroom fan.

Of course, a fan is necessary in any bathroom, especially a tiny one inside a tiny house. As I and others have discussed in multiple tiny house blog posts, moisture can be a real issue inside a tiny house and I don’t want a lot of it building up inside my bathroom when I take a shower. So I have to have a fan.

The first challenge regarding the fan was to pick the right fan. Many tiny house builders choose the Panasonic whisper quiet fan which seems like a great choice. Unfortunately, the Panasonic fan runs on 110 volts and I really wanted a fan that ran on 12 volts. I’m trying to do as much of my electrical as possible in the house using 12 volts to save energy by eliminating power losses from converting back-and-forth between various voltages. It was hard to find a 12 V fan appropriate for a 3 1/2 inch deep bathroom wall. However, after much looking on line, I finally settled on an Atwood 3″ diameter bilge blower which I combined with two Speedi-Products EX-EVML 03 3-Inch Diameter Micro Louver Eave Vents, one for outside and one for inside. The total length of the blower and the two vents was about 5 1/2 inches which is exactly the distance from the outside of my interior siding to the outside of my exterior siding.

Atwood Fan

Atwood Fan

Vent

Eave Vent

Fan and Vent Together

Fan and Vent Together

I bought the fan and vents weeks ago but have been putting off installing them because, as I may have mentioned earlier, I really didn’t want to cut holes in my walls. Yesterday, I finally got over that fear and installed the fan. Now that I have done it, I’m pretty happy with the result and even find myself finally willing and perhaps even a little bit eager to cut the remain hole for my water tank inlet.

Step one in installing the fan was very carefully and precisely determine where to cut the hole. The last thing I wanted to do was cut a 3 inch hole in my siding in the wrong place. Finding the right place to cut the hole was not trivial. I wanted the vertical location of my fan to be exactly in the center of a single piece of exterior siding. However, I wanted the horizontal location of my fan to be based on the location of an interior stud that I could screw it to. Locating something precisely using a vertical measurement from the outside of the house and a horizontal measurement from the inside of the house was not easy. After measuring from the inside stud to the inside edge of the bathroom window, I then attempted to transfer that measurement to the siding by measuring back out from the outside of the window. When I was pretty sure about the position, I drilled a very small pilot hole all the way through the siding and the inside wall. It’s a good thing I did this because despite all my careful measuring, I still ended up being off by a quarter of an inch in the horizontal direction. Because the pilot hole was still well within the 3 inch diameter of the final hole, I could easily correct the center of the circle.

Once I was knew where the center should be, I removed the piece of siding so I could cut the hole. I traced a 3 1/4″ hole (the outer diameter of my vent) around the corrected center and cut the hole using a jigsaw. I made the cut from the back side, remembering from all my siding installation that that is the way to get a level hole through the siding. After the hole was cut, I applied stain to the freshly cut wood.

Siding Hole Cut

Siding Hole Cut

Once the hole was drilled and stained, I held the siding back in place and traced a corresponding circle on the exterior sheathing beneath it. Then, I cut that hole out with a jigsaw also.

Sheathing Hole Cut

Sheathing Hole Cut

Next, I did a little bit of prep work to the fan and the vents. The fan had a couple of fins on both sides and one of them was keeping the fan from fitting through the hole in the sheathing. The fin didn’t seem to have any structural or functional purpose, so I took a pair of pliers and simply ripped it off. After that, the fan fit nicely through the hole. The vents came with about 3 inches of aluminum conduit attached to it. My spacing required that I attach the fan directly to the vent, so I ripped off the aluminum as well.

Removing Fin from Fan

Removing Fin from Fan

Next, I installed the fan. I applied a generous amount of caulk to the inside of the hole in the exterior sheathing, pushed the fan through the hole and screwed it to the stud. I then smoothed out the caulk to make sure there were no holes or gaps. I went outside and applied another bead of caulk around the fan. Then, I reinstalled the piece of siding, applied caulk to the hole in the siding and installed the vent, screwing it to the siding with 2″ stainless steel screws. I also applied caulk to the top and both sides of the vent, leaving the bottom edge of the vent clear of caulk so that any water that did get inside the vent could drain back out.

Fan Installed and Caulked on the Inside

Fan Installed and Caulked on the Inside

Fan Installed and Caulked on the Outside

Siding Replaced and Caulked Around Fan

Vent Installed

Vent Installed

The last thing that I did was connect the fan to the wiring I had run to that part of the wall. The wiring runs through a switch on the right side of the bathroom window that will allow me to turn the fan on on and off when I want. I hooked up my 12 V battery to the system, flipped the switch and listened to the fan hum to life.

I think the installation look fairly attractive from the outside and believe it will look good on the inside also. The little fan that I purchased seems to push a good amount of air as well. The only downside to the fan is that it is a little bit noisy. I’m sure it’s much noisier than the Panasonic whisper quiet fans. However, I think I will only be running the fan when I am showering, cooking or using the loo, so I don’t think it will be that big a deal.

Next up: water inlet!

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