Find the location for your Maxxfan. Left/right is easy: the adapter fits neatly into the indentations of the roof. For front/back, we centered ours between the frame and the edge of the recess at the front (this edge is visible outside as well, use it as a reference):

Apply painter’s tape over the trim line and a few inches beyond the adapter perimeter (2 layers thick because the jigsaw can rip through the tape easily and scratch the paint). Use the interior of the fan adapter to mark the contour of the 14″x14″ cutout:

Tape a box to the ceiling to catch the metal chips (our box eventually fell… use more tape or straps!):

Drill a hole at each corner, tangent to the contour lines, large enough for the jigsaw blade (1/8″ drill bit, and then we used a 3/8″ drill bit):

Using a jigsaw (or a nibbler), trim along the contour line (tip: before cutting the last edge, tape the other edges to prevent the panel from falling for a cleaner cut):

Install the adapter and the flange, then clamp to ensure nothing moves. Drill all 16 holes with a 13/64″ drill bit through the adapter and the roof, using the flange as a template

• Locate the flange so the metal inserts (used to secure the fan) are left/right.
• Our box fell off, so we installed a plastic bag instead…

Remove the adapter and the flange (they will have to be reinstalled in the same orientation for the holes to match perfectly, mark the front and rear!), then enlarge all holes in the roof (not in the adapter) with a 7/32″ drill bit (this will make the assembly easier subsequently) :

Deburr the edges with a deburring tool and a file, then smooth with 220-grit sanding paper (this promotes the paint’s adhesion).

Tip! To deburr the holes, it is easier and faster to use a large drill bit (e.g., 3/8″) or a countersink bit (use light pressure and just a few turns):

Apply painter’s tape around the perimeter of the flange (leave 1/4″ gap):

De-gloss the mating surface (adapter with roof) with a Scotch-Brite pad (see Tools section). No need to scuff, just dull the paint:

Clean the mating surface and the edges (contour and holes) with Isopropyl alcohol:

Apply 2 coats of rust preventive paint (let dry between each coat, follow product instructions):

Use isopropyl alcohol to clean the roof where it will mate with the adapter:

Clean the Maxxfan flange with isopropyl alcohol:

Apply the butyl tape around the Maxxfan flange perimeter, make sure to apply over the holes:

Apply 2 or 3 beads of Sikaflex 221 to the surface of the adapter mating with the roof:

Start by installing the adapter:

Then install the fan flange:

From the top, insert the screws and washers (poke the screws through the butyl tape). From the bottom, install the washers and nyloc nuts. Fasten all the nuts uniformly, but do not over-tighten! If there is too much pressure, the flange could eventually crack. The goal is to have a tight fit and have some oozing, but don’t go crazy:

The butyl tape and Sikaflex will ooze out a bit, which is a good thing. Trim the extra butyl tape, and use your finger to make a fillet around the Sikaflex (as required):

We didn’t get as much Sikaflex oozing as we wished, so we added a little to make a nice fillet around the perimeter:

Remove the painter’s tape within 15 minutes and let the Sikaflex form a skin for an hour:

Apply Dicor self-leveling sealant. Ensure to cover the flange, the screws, the adapter, and the roof. One cartridge of Dicor is barely enough, so make sure to have a second one handy just in case:

Heck that was hard work, so treat yourself while you wait for the sealant to cure for a few hours!

Slide the Maxxfan over the flange:

Install the 2 screws on each side, remove the protective film, and be happy!

Get in the van, yep there’s a fan!