Sunday, August 22, 2010

Bath Fan Sealing

Noted poor installation of a bath fan had a few reporting errors.

There were two fans, both Panasonic FV08VQ3, a very common, excellent, extremely quiet 80 cfm unit that in fact is very easy to install. Light from bathrooms could be seen from the attic, corresponding of course to heat loss.

From below, installations seem to be tidy. The installer probably thought he had followed directions, and has probably done many similar installations.

Directions do not consider the most-common need, remodel installation through existing drywall. Here openings were enlarged, to replace silly American noise-makers.

Begin with knowing the guts of each fan must be removed. All screws are Phillips drive. Collect four that release the lightweight cover plate. Three more are machine screws that release the motor assembly, not dropping out.
In each case, the fan body flange was traced, and drywall was cut through to reveal half of the width of a truss bottom chord.

Drywall scraps, and the dead fans, were tossed into the trash heap of loose-fill insulation above.
The solution available to me, with the flexible grout I offer, was to reset scraps  in properly-framed openings. This was possible in part because drywall was strong, 5/8" fire-rated, for condominium construction. The repair is as-new on three edges with wood backing. I will adequately glue the unsupported side, with flexible grout.
Here are the two openings, ready for fan insertion. 2x3 frame sides spaced 10 1/2" are attached to truss chords, with 3" deck screws. The openings in the other direction are 10 5/8".
Fan adapter assemblies, still wired, stand securely, with bottom flanges engaging the underside of the drywall.
Each fan body is pushed through from below, and is loaded against 2x3 rails, with 2 1/2" deck screws.

Complete reassembly of fans can happen now, ready for paint.

The adapter assembly top clips are rotated onto fan bodies, completing tight assembly, from above.

Foil-tape the ducts, and reset cable staples.

The above is an exercise in blogging, further learning what is possible with the free resources of I think this sharing of experience is a necessary investment to fight installation error, and waste of energy. I have started another blog as another way of trying this. I think an installation methods forum of some kind is needed, and will hope to at least be a contributor.


Staci said...

Yes, poor installation of a bath fan gets you poor performance in return. It is primarily designed to eliminate moisture and unpleasant odor in the room. Where was it located, by the way? Mine was between the shower and the toilet. Our contractor said it would give the highest efficiency there.

-->Staci Severns

Phil Norman said...

More often than not, we are dealing with replacement, where we are inclined to accept the found location. Panasonic fans here are 10.5" square, usually larger than an old noisemaker, and some logical shifting will be done. I think a center of the ceiling usually is best, with only lights getting "aimed."