So the objective is to replace the heater in the master bathroom with a fan also. I got a new fan from Lowe's, a Broan 683, just like the one in the back bathroom.
The painters, when they were scraping the popcorn off the bathroom ceiling, removed the heater.
But the fan will need to be installed above the ceiling, in the floor of the attic. Unfortunately, this is in a corner of the house, with two exterior walls, so there is not a lot of clearance to work in. To make things worse, that corner of the attic is essentially walled off by the loft area that we put in when we remodelled one of the bedrooms, and has been so well insulated as to be nearly unreachable.
But I realized that it was just behind the built-in bookcases in the attic. So if we remove the bookcase, we should be able to get right to the area we need to work in.
First, we need to empty the bookcase and clear away a lot of stored stuff.
Then the bookcase, which is just nailed in around the edges of the trim, can be pulled out.
But unfortunately, the loft area was built without the bookcases, and the area behind the bookcases is all finished sheetrock.
and thinking about it, the wall behind the bookcases should be very heavily insulated. One option is to cut thru the sheetrock and patch it later, but maybe this was not the best idea.
Let's try to remove the solar board radiant barrier in the attic and see if we can crawl back to work from the attic.
25 April 2014:
Removing the solar board, it becomes obvious that getting to the area we need to work in from the attic would be next to impossible.
So it seems the most reasonable way to approach the problem is thru the wall behind the bookcase. We cut out an area between two studs.
And that gets us into the attic. This part of the attic is not floored, so we move the insulation out of the way and lay a board down across two floor joists (or ceiling rafters), and this gets us back far enough to find the electrical box with the wiring for the old heater.
Removing the electrical box from the ceiling, and using the hole from that to define one corner, we cut a larger rectangle that is just the size of the new fan.
While it is a mess up in the attic, it looks pretty good in the bathroom.
The instructions say to position the new fan flush with the ceiling. To do that, since it has to be nailed to the ceiling rafter in the attic, I tacked two one by two pieces of scrap wood across the opening in the bathroom. This will leave 4 small holes that need to be filled in, and re-painted, but the new fan sits perfectly on the 1x2 pieces at just the right height.
Once the position of the fan is established, we then need to make a hole on the outside of the house for the exhaust vent. Careful measuring, and drilling a test hole, establishes where this should be
We then drill multiple holes in the rock along the outside of where we want the hole to be, and use a rock chisel to break the rock out, cut thru the blue Styrofoam insulation, and thru the tar paper covered exterior façade, behind the Styrofoam board and the rock exterior. This allows us to install the actual exterior vent.
Now, we can snake the vent tube from the fan across the attic to the exterior hole and attach it to the exterior vent. Having attached the wiring from the heater switch to the fan power wires, we now have a completely functioning vented fan.
Now we cover everything back up with lots of insulation. We bought two more rolls of unfaced R-30 fiber glass insulation, and add it to what was already there.
The insulation goes right up over the access hole. We add a 2x3 stud down each side of the access hole.
Which we then cover with a piece of plywood using decking screws, so that, if need be, we can just remove it if we need future access.
We slide the bookcase unit back into place and nail it to secure it.
This entire process took a couple of days, but we now have a vented fan, instead of an unvented heater.
The middle bathroom (guest bathroom) still has a heater; it appears replacing this unit would be nearly impossible from inside the house -- we would need to come in from the roof, so we are inclined to leave it until we need the roof replaced, in maybe twenty years.