ProductAlert ·

Beat the Heat: Installing the AVC Aluminum AC Furring Kit

Hey everybody, welcome back to AVC Chronicles! On today’s post, we’re tackling one of the most critical parts of a climate-controlled build: installing our Aluminum AC Furring Kit.

If you’ve ever worried about your rooftop AC unit leaking or warping your roof, this post is for you. Let’s get into the "why" and the "how" of getting that unit mounted properly.

Why Use a Furring Kit?

Most rooftop air conditioners don't use fancy adhesives to stay waterproof; they use compression. There is a thick foam gasket on the bottom of the unit that sits on your roof. You tighten bolts from the inside, pulling the unit down to squeeze that gasket and create a seal.

The Problem: The sheet metal on a Ford Transit roof is relatively soft. If you tighten those bolts against just the sheet metal, the roof will comply (bend) before the gasket fully compresses. This leads to a weak seal and, eventually, a wet interior.

The Solution: Our aluminum furring kit provides a rigid, sturdy structure for those bolts to pull against. This ensures the gasket gets the squeeze it needs without turning your roof into a taco.

Two Kits, Two Locations

We’ve designed two versions of this kit because there are two popular spots for an AC unit:

  1. The Rearmost Bay (148" Long Body): This is our favorite spot. The roof ribs are already spaced at 14 inches, which is the standard size for most AC plenums. This kit includes two north-south brackets that span the ribs.

  1. The Front Section: Often where people put a MaxxAir fan, the spacing here is wider. This kit includes two north-south brackets plus a third cross-section to create a perfectly square 14-inch frame using a factory roof rib as the fourth side.

The Installation Process

1. Cut and Prime

First things first: cut your 14-inch square hole. We patterned ours for the rear bay of the Transit.

Pro Tip: Do not skip this—prime those raw metal edges. Exposed metal in a van is just an invitation for rust.

2. Dry Fit

Before you break out the glue, line up the interior edge of the brackets with the side of your cut opening.

  • Use only two screws on the end of each bracket for a temporary fit.

  • We use "fresh" holes for the final install later to give us a little wiggle room for adjustments.

3. Apply Adhesive

Take the brackets back to the bench (or the van floor). You need a high-quality polyurethane adhesive.

  • AVC Choice: We use 3M 550, but SikaFlex or a leftover window adhesive works too.

  • Apply a nice, healthy bead of glue on each side of the bracket where it contacts the roof and the ribs.

4. Final Mounting

Mount the brackets back into place. You want to see some glue squeeze-out—that tells you you have a solid, gap-free bond. Secure them with the remaining screws and let the adhesive cure.

5. Drop the AC Unit

Once the glue is stiff, head up to the roof and drop your AC unit into the hole.

  • From the inside, install the hardware that came with your AC.

  • Tighten the bolts so the unit pulls against the aluminum brackets.

  • Once it's cinched down, you can trim the excess length off the bolts for a cleaner look.

Ready for the Road

With the aluminum kit in place, you can drive off knowing your AC is rock-solid and leak-proof. No more checking the ceiling every time it rains!

If you have any questions about the install, don't hesitate to reach out! Ready to grab a kit for your own build?

Thanks for reading and we'll see you on the next one!

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