FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In
There's a Better Way Video Tips

Make Your Own Rigid Foam Roof-Vent Baffles

A simple cutting tool made with scraps of wood and a utility-knife blade allows you to make baffles to put between your rafters for a better insulation job.

By Official Fine Homebuilding Post
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles
Video Player is loading.
Current Time 0:00
/
Duration 0:00
Loaded: 0%
Stream Type LIVE
Remaining Time -0:00
 
1x
    • Chapters
    • descriptions off, selected
    • captions settings, opens captions settings dialog
    • captions off, selected

      This is a modal window.

      Beginning of dialog window. Escape will cancel and close the window.

      Text
      Background
      Window
      Font Size
      Text Edge Style
      Font Family

      End of dialog window.

      This is a modal window. This modal can be closed by pressing the Escape key or activating the close button.

      This is a modal window. This modal can be closed by pressing the Escape key or activating the close button.

      If you’re insulating a cathedral ceiling and need to maintain an air-sealed vent space from the soffit all the way to the ridge, you could use plastic baffles stapled into place between the rafters and try to air seal them, but there’s a better way.

      When Bob Kelly of Kensington, NH had to insulate a cathedral ceiling, he came up with a clever way of using rigid foam as his vent baffle, so that he could maximize the air value of his ceiling and easily air seal at the same time. The secret is a homemade cutting jig that holds a utility knife blade. The rigid foam is cut to be 2 inches wider than the space between rafters, then 1 inch of foam is scored and folded over on either side of the foam, creating standoffs that hold the foam away from the roof sheathing, providing a space for air to flow. When set into place and sealed with spray foam, the vent baffles are insulated and air-sealed.

      Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

      Signing you up...

      This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
      See all newsletters
      See all newsletters
      ×

      Get home building tips, offers, and expert advice in your inbox

      Signing you up...

      This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
      See all newsletters
      See all newsletters

      New Feature

      Fine Homebuilding Forums

      Ask questions, offer advice, and share your work

      • X
      • facebook
      • linkedin
      • pinterest
      • email
      • add to favorites Log in or Sign up to save your favorite articles

      View Comments

      1. bonnercd | Jun 30, 2016 11:16am | #1

        So in this application, the rafter bay is air sealed, right? Nothing coming in at the soffit, and nothing going out at the ridge? Or am I reading this wrong?

        If it is air sealed, what is the function of the air space?

        Thanks for the clarification.

      2. stukinftw | Jun 30, 2016 02:57pm | #2

        what method was used to secure the now cut for the correct depth rigid foam to the under side of the roof decking or the sides of the rafters? Thanks

      3. kmead | Jun 30, 2016 06:30pm | #3

        I believe the point here is that they have sealed to the edges of the rafters which creates a seal between the roof area and the insulation below. There is no seat at the top and bottom so it will still allow airflow from the soffit to the top vent, just like the leaky plastic troughs.

        Keeping air from migrating up through the rafter bays will significantly improve the general sealing of the house. Keep in mind that the relative air pressure (due to the temperature differential) at the top of the house is quite a bit higher than ambient outside the house, doing this greatly reduces the migration of air through the structure.

      4. user-1137422 | Jul 01, 2016 10:39am | #4

        I'm a big fan of these quick tips. However I'm sad to see finehomebuilding sponsor Home Depot so prominently. I loath the big box stores because everything they sell is of questionable quality. Wood, tile, paint - it's all just horrible.

      5. JFink | Jul 01, 2016 01:48pm | #5

        stukinftw - the rigid foam baffles can be fastened with angled nails or screws driven tight against the face of the foam and up into rafters on either side. You don't need much to hold them into place, just enough to temporarily hold them until a bead of spray foam sealant applied along each edge sets up and does the permanent holding.

      6. JFink | Jul 01, 2016 01:49pm | #6

        bonnercd - kmead is correct in his/her explanation. The soffits and ridge vent are still open to airflow, and these vent baffles are simply providing a fully separated path so the ventilation air can run from eave to ridge without washing through the insulation in the rafter bays.

      7. Efp1 | Jul 03, 2016 10:25am | #7

        Most research shows that a minimum of 1 to 2 inch air gap is required for adequate air flow. So, perhaps it would be better to cut the board 4 inches longer, then score on both sides to create a z fold. This would give an air gap of 1 to 1.5 inches.

      8. jimcrook | Apr 06, 2017 07:55pm | #8

        So let's say you have rafters that are 16" on center. The bays are 14.5" wide. You add a couple of inches to the foam board you're working with per this video's instructions. That's 16.5". You can only get two lengths that wide out of a 48" wide board and are left with another piece that's about 15" wide. I guess you could adapt and use inch-high sticks for this last bay, but it does seem a bit annoying.

      9. youngga2 | Jan 09, 2020 07:07pm | #9

        If the rafters are 16" on center why not cut the insulation 16" wide and make 3/4" wide slices down the sides, this way you could get three pieces out of each sheet of insulation. Also if you use a thicker insulation this gives you an air gap of whatever thickness the insulation board is since it is folded over on itself. I believe this was shown years ago in a tip at the back of the magazine and it has always stuck in my mind. I always thought I would use 2" thick insulation to give a 2" air gap and secure it with a bead of spray foam on the inside surface. You also need to box off the soffit and ridge vents so the air can flow in the soffit through your baffle and out the ridge vent.

      Log in or create an account to post a comment.

      Sign up Log in

      Become a member and get full access to FineHomebuilding.com

      More There's a Better Way Video Tips

      View All
      • Bending Rebar with Pipes
      • Shimming Roof Jack
      • Foam-Gun-Tip Cleaner
      • Bucket-Mixed Concrete
      View All

      Up Next

      Video Shorts

      Featured Story

      Tools and Gear for the Moms Who Get it Done

      From work boots to power tools, these favorite picks make perfect gifts for moms and women who build.

      Featured Video

      SawStop's Portable Tablesaw is Bigger and Better Than Before

      The 10-in. Jobsite Saw PRO has a wider table, a new dust-control port, and a more versatile fence, along with the same reliable safety mechanism included in all SawStop tablesaws.

      Related Stories

      • A Practical Approach to Exterior Insulation
      • FHB Podcast Segment: Designing and Building an Efficient Slab-On-Grade Home
      • Makeshift Foam Tip for Tight Spots
      • Insulation Shield for Wafer Lights

      Discussion Forum

      Recent Posts and Replies

      • |
      • |
      • |
      • |
      • |
      • |
      View More Create Post

      Highlights

      Fine Homebuilding All Access
      Fine Homebuilding Podcast
      Tool Tech
      Plus, get an extra 20% off with code GIFT20

      Video

      View All Videos
      • FHB Podcast Segment: Insulating the Roof of a Small Balloon-Framed House
      • FHB Podcast Segment: Old Home Insulation Troubles - How to Find the Right Contractor
      • FHB Podcast Segment: Is There a 'Right' Spot for a Vapor Retarder in this Climate Zone?
      • FHB Podcast Segment: Ductwork in a Vented Attic
      View All

      Attics

      View All Attics Articles
      • HVAC for a Slab-on-Grade House
      • Strategies for Making an Old House Airtight
      • Podcast Episode 649: Sealing Crawlspaces, Problem Porches, and AC in Attics
      View All Attics Articles

      Fine Homebuilding Magazine

      • Issue 331 - June 2025
        • A More Resilient Roof
        • Tool Test: You Need a Drywall Sander
        • Ducted vs. Ductless Heat Pumps
      • Issue 330 - April/May 2025
        • Deck Details for Durability
        • FAQs on HPWHs
        • 10 Tips for a Long-Lasting Paint Job
      • Issue 329 - Feb/Mar 2025
        • Smart Foundation for a Small Addition
        • A Kominka Comes West
        • Making Small Kitchens Work
      • Issue 328 - Dec/Jan 2024
        • How a Pro Replaces Columns
        • Passive House 3.0
        • Tool Test: Compact Line Lasers
      • Issue 327 - November 2024
        • Repairing Damaged Walls and Ceilings
        • Plumbing Protection
        • Talking Shop

      Fine Home Building

      Newsletter Sign-up

      • Fine Homebuilding

        Home building tips, offers, and expert advice in your inbox.

      • Green Building Advisor

        Building science and energy efficiency advice, plus special offers, in your inbox.

      • Old House Journal

        Repair, renovation, and restoration tips, plus special offers, in your inbox.

      Signing you up...

      This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
      See all newsletters

      Follow

      • Fine Homebuilding

        Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

        Start Free Trial Now
        • Facebook
        • Instagram
        • X
        • LinkedIn
      • GBA Prime

        Get instant access to the latest developments in green building, research, and reports from the field.

        Start Free Trial Now
        • Facebook
        • YouTube
      • Old House Journal

        Learn how to restore, repair, update, and decorate your home.

        Subscribe Now
        • Facebook
        • Instagram
        • X
      • Fine Homebuilding

        Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

        Start Free Trial Now
        • Facebook
        • Instagram
        • X
        • LinkedIn
      • GBA Prime

        Get instant access to the latest developments in green building, research, and reports from the field.

        Start Free Trial Now
        • Facebook
        • YouTube
      • Old House Journal

        Learn how to restore, repair, update, and decorate your home.

        Subscribe Now
        • Facebook
        • Instagram
        • X

      Membership & Magazine

      • Online Archive
      • Start Free Trial
      • Magazine Subscription
      • Magazine Renewal
      • Gift a Subscription
      • Customer Support
      • Privacy Preferences
      • About
      • Contact
      • Advertise
      • Careers
      • Terms of Use
      • Site Map
      • Do not sell or share my information
      • Privacy Policy
      • Accessibility
      • California Privacy Rights

      © 2025 Active Interest Media. All rights reserved.

      Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

      • Home Group
      • Antique Trader
      • Arts & Crafts Homes
      • Bank Note Reporter
      • Cabin Life
      • Cuisine at Home
      • Fine Gardening
      • Fine Woodworking
      • Green Building Advisor
      • Garden Gate
      • Horticulture
      • Keep Craft Alive
      • Log Home Living
      • Military Trader/Vehicles
      • Numismatic News
      • Numismaster
      • Old Cars Weekly
      • Old House Journal
      • Period Homes
      • Popular Woodworking
      • Script
      • ShopNotes
      • Sports Collectors Digest
      • Threads
      • Timber Home Living
      • Traditional Building
      • Woodsmith
      • World Coin News
      • Writer's Digest
      Active Interest Media logo
      X
      X
      This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

      Main Menu

      • How-To
      • Design
      • Tools & Materials
      • Video
      • Blogs
      • Forum
      • Project Guides
      • Reader Projects
      • Magazine
      • Members
      • FHB House

      Podcasts

      • FHB Podcast
      • ProTalk

      Webinars

      • Upcoming and On-Demand

      Podcasts

      • FHB Podcast
      • ProTalk

      Webinars

      • Upcoming and On-Demand

      Popular Topics

      • Kitchens
      • Business
      • Bedrooms
      • Roofs
      • Architecture and Design
      • Green Building
      • Decks
      • Framing
      • Safety
      • Remodeling
      • Bathrooms
      • Windows
      • Tilework
      • Ceilings
      • HVAC

      Magazine

      • Current Issue
      • Past Issues
      • Magazine Index
      • Subscribe
      • Online Archive
      • Author Guidelines

      All Access

      • Member Home
      • Start Free Trial
      • Gift Membership

      Online Learning

      • Courses
      • Project Guides
      • Reader Projects
      • Podcast

      More

      • FHB Ambassadors
      • FHB House
      • Customer Support

      Account

      • Log In
      • Join

      Newsletter

      Get home building tips, offers, and expert advice in your inbox

      Signing you up...

      This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
      See all newsletters
      See all newsletters

      Follow

      • X
      • YouTube
      • instagram
      • facebook
      • pinterest
      • Tiktok

      Join All Access

      Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

      Start Your Free Trial

      Subscribe

      FHB Magazine

      Start your subscription today and save up to 81%

      Subscribe

      We hope you’ve enjoyed your free articles. To keep reading, become a member today.

      Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

      Start your FREE trial

      Already a member? Log in

      Privacy Policy Update

      We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

      Cookies

      Analytics

      These cookies help us track site metrics to improve our sites and provide a better user experience.

      Advertising/Social Media

      These cookies are used to serve advertisements aligned with your interests.

      Essential

      These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

      Delete My Data

      Delete all cookies and associated data