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

Discussion Forum

Discussion Forum

Vapor Barior on Existing 3-Season Porch

Dudley | Posted in General Discussion on September 29, 2009 10:03am

Friend is installing new windows on an already build 3 season porch – he ash installed new windows and is interested in tightening the space up as much as he can with out pulling off the old siding.

Siding is masonite (original siding) covered by vinyl siding.

he will put insulation in the walls – his question – should he also put a vapor barrier against the siding? tks Dudley

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

Replies

  1. DanH | Sep 30, 2009 12:55am | #1

    He would be making it into a conditioned space, and the vapor barrier should be placed "as appropriate" for your climate, which I would guess would mean towards the inside in MD, not the outside.

    But likely a vapor barrier isn't needed at all, since the space is inevitably going to be leakier and therefore lower humidity (in the winter) than the rest of the house. (Whether local code may require something is another issue.)

    He might want to put some sort of wind barrier (eg Tyvek) against the siding, but retrofitting such a barrier can be difficult.

    As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
    1. Porchguy | Sep 30, 2009 07:07pm | #2

      So Dan (I'm the one insulating the porch), are you saying that, I put in foil backed (one sided) insulation with the foil on the inside of the 2x4's?  No foil back on the exterior side?  And/or, if I caulk the 2x4's that sit on a (4 courses) brick base all around to keep bugs, dampness etc. should I put a sheating with tyvek on it before insulating? 

      Thanks,

      Porchguy

      1. User avater
        Mongo | Sep 30, 2009 08:03pm | #3

        A little clarification; The exterior side of the walls are sided and are going to stay as-is, right? And the interior of the walls are open 2x4 stud bays?The framed walls are sitting on brick, is the brick going to remain exposed on the interior or covered up?If the walls are sitting on 4 courses of brick, is porch floor slab-on-grade? Or framed and elevated with a crawl space underneath?

        1. Porchguy | Sep 30, 2009 09:25pm | #4

          Here's the skinny.  This was a screened porch which I have ripped out and put in slider windows that sit on a shelf.  Below the shelf is simply 2x4 studs on top of a 4 course row bricks to get above grade.  The height of the 2x4's on the brick to shelf is 1 1/2'.  When the porch was built (26 years ago) they simply nailed masonite siding onto the studs.  They have since been covered with vinyl siding.  So, I was going to caulk the stud joints and where they meet the bricks to keep out dampness and bugs.  I will not cover the brick to floor (which is concrete) on the interior.  But, given that I want to insulate, I was wondering if I need to put a vinyl (vapor barrier) cover next to the interior siding before putting the insulation in to avoid mildew and moisture.  This will not be heated or cooled in the winter/summer months simply a kind of Floriday room off the family room which has a sliding door from the house to the porch.  The windows are to keep the snow, rain and dirt out year round now and, make it more longer seasonal room.

          As for the concret floor, I was thinking about putting down a TREX floor on a 2x4 frame.  What do you think?

          Porchguy   

      2. DanH | Sep 30, 2009 11:30pm | #5

        Based on your description below, you probably don't NEED a vapor barrier, period. But if you install one (eg, the one that comes attached to the insulation), it should (based on the conventional wisdom) be installed towards the "warm" side.The purpose for installing Tyvek or something similar would be to prevent air from blowing through cracks it the siding and degrading the insulating value of the (I presume fiberglass) insulation in the walls. You alternatively could just caulk every crack you can find, or install the insulation backwards (from what's described above) so that the vapor barrier serves as a wind barrier (of sorts -- not very good but better than nothing). You run a very slight risk of creating conditions that could lead to condensation in the walls if you install the insulation "backwards" like this, but probably not enough of a risk to worry about.
        As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz

        1. Porchguy | Oct 01, 2009 12:50am | #6

          Thanks for your insight, I'll follow your instructions and simply install it as it is supposed to be.  I'll also caulk, REAL GOOD!

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

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

Up Next

Video Shorts

Featured Story

A Classic Paint Sprayer Gets a Thoughtful Refresh

The Titan Impact X 440 offers great coverage with minimal overspray.

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

  • Podcast Episode 693: Old-House Hazards, Building Larsen Trusses, AI in Construction
  • FHB Podcast Segment: Finding Hazardous Materials in a Fixer-Upper
  • A Classic Paint Sprayer Gets a Thoughtful Refresh
  • Podcast Episode 692: Introduction to Trade Work, Embodied Carbon, and Envelope Improvements

Highlights

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

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

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

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • 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 2025
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

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 70%

Subscribe

Enjoy unlimited access to Fine Homebuilding. Join Now

Already a member? Log in

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