Bathroom Exhaust Fan Roof Vent Kit | What Works & How To Install

A roof vent kit for bath fans, such as the Broan-NuTone RVK1A, includes the ducting and roof cap needed for slanted-roof installation.

Most homes with a slanted roof need a bathroom exhaust fan roof vent kit, and the Broan-NuTone RVK1A is the standard choice. This roof vent kit combines flexible aluminum duct, a 4-inch metal connector, a 3-to-4-inch reducer, and a black steel roof cap — everything required to route fan exhaust through the roof while keeping weather and pests out. The sections below cover exactly what the RVK1A includes, how to install it step by step, and the common mistakes that cause leaks.

What Does A Bathroom Exhaust Fan Roof Vent Kit Include?

A roof vent kit bridges the gap between your bathroom fan’s discharge outlet and the roof termination. Instead of piecing together separate components, a complete kit supplies everything in one box.

• Flexible aluminum duct — 4-inch diameter, 8 feet long, routed from the fan to the roof cap.
• Metal duct connector — A 4-inch connector that locks onto the roof cap assembly inside the attic.
• Reducer — A 3-inch-to-4-inch adapter for fans with a smaller discharge collar.
• Roof cap — Black steel, weatherproof, with a damper that prevents backdraft when the fan is off.
• Nylon zip ties — For securing the duct to the connector.

The RVK1A covers both 3-inch and 4-inch duct sizes, which means it fits the vast majority of residential bath fans on the market.

Broan-NuTone RVK1A Specs & Kit Contents

Broan-NuTone’s RVK1A product page confirms the full parts list and shows the locking connector mechanism that simplifies attic work.

Can You Use The RVK1A On A Flat Roof?

No. The RVK1A is designed exclusively for pitched or slanted roofs. A flat roof needs a different termination — typically a gooseneck-style vent or a low-profile cap that doesn’t rely on gravity drainage. Installing the RVK1A on a flat roof guarantees poor performance and leaks, because the cap’s flange and slope assume water will run downhill. Flat-roof installations require specialized flat-roof vent kits with taller standoffs and different sealing methods.

Roof Vent Kit Installation: The Step-By-Step Process

Installing the RVK1A requires attic access and roof access. The sequence below follows the official Broan-NuTone installation guide and pro installer demonstrations.

1. Locate and drill. From inside the attic, find the fan’s discharge location. Go onto the roof and drill a pilot hole. Widen it to a minimum 4.5-inch hole through the shingles, plywood, and all roof layers. A 5-inch hole saw is ideal for the final cut.
2. Assemble the connector. Line up the VCU edge of the 4-inch metal duct connector under the notch in the roof cap opening. Rotate the connector 360 degrees until it locks in place. You will hear and feel it seat.
3. Insert and trace. Push the assembled cap and connector into the roof hole so the flange sits flat against the shingles. Trace the outline of the roof flange onto the shingles with a pencil or chalk.
4. Trim the shingles. Remove the cap. Cut the shingles inside the traced outline — follow the hood edge, not the flange edge. This lets the shingles overlap the flange when reinstalled.
5. Slide and nail. Carefully lift the adjacent shingles and slide the roof cap flange underneath them. Nail the flange to the roof at the top and two sides using 1.5-inch roofing nails. The nails must sit under the shingle overlap.
6. Seal everything. Apply a continuous bead of polyurethane roof cement or tripolymer caulking over the top and sides of the cap. Cover every nail head with sealant. This step prevents every leak.
7. Connect the duct in the attic. Back inside, attach the flexible aluminum duct to the metal connector using HVAC foil tape or a metal clamp. Never use standard duct tape — it degrades quickly and leaks air. Secure the connection with the included nylon zip ties.
8. Finish the roof seal. Press the lifted shingles back over the flange. Add a final bead of sealant along the outer edge of the flange for waterproofing.

When the fan runs, you should feel steady airflow at the roof cap with no whistling or resistance — that confirms a tight seal and clear duct path.

Common Installation Mistakes To Avoid

• Flat roof installation. Using the RVK1A on a flat roof causes pooling water and leaks. Buy a flat-roof-specific vent kit instead.
• Standard duct tape on interior joints. Foil tape or metal-clad HVAC tape is the only option. Duct tape fails within months in attic heat.
• Double-venting two fans. Never tie two bathroom fans into a single roof termination. Each fan needs its own vent path and separate roof cap.
• Nailing below the shingle line. Nails exposed to weather rust and leak. All nails must sit under the overlapping shingle and be covered with sealant.
• Cutting the hole before locating the fan. Drill your pilot from inside the attic, not from the roof side. A misplaced roof hole means patching and re-cutting.
• Long duct runs. The kit works best with the shortest possible straight duct run. Long, sagging, or kinked duct reduces airflow and causes moisture buildup.

Choosing The Right Vent Kit For Your Setup

The Broan-NuTone RVK1A fits most slanted-roof installations with 3-inch or 4-inch round duct fans, but your situation may call for something different. If you need a longer duct than the 8-foot flexible aluminum included with the RVK1A, the Lambro Industries 402UL kit offers a similar layout with extended reach. For a rigid-pipe installation where you want a painted galvanized finish and a built-in damper, the FAMCO Piped Roof Exhaust Vent is a solid alternative. Before you buy, check your fan’s duct size, your roof pitch, and your local building code — and see our tested bath fan roof vent kit reviews for side-by-side comparisons of the top options available today.

Make sure the vent kit you choose matches your fan’s duct diameter and your roof type. The right kit installed correctly will run silently, vent moisture effectively, and never leak — for the life of the fan.