Multiple Vapor Retarders - Remodeling - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Remodeling


Thread Tools Display Modes
Old 11-26-2009, 11:31 PM   #1
Join Date: Nov 2009
Posts: 1
Rewards Points: 10

Multiple vapor retarders

Hi all-

Question: Should I remove the interior layer of tar paper on my house. I'm concerned with trapping moisture inside the walls. Given the house 'breathed' fairly well it didn't seem to present any previous issues, but the goal is to stop allot of the air infiltration and removing the interior layer seems like common sense. I did notice that above most of the windows the paper was de-laminating from the plaster brown coat and that there was no interior tar paper above the windows.Thoughts.

Details and Existing Construction.
1907 home in climate zone 7 (Tacoma, WA). 900sqft. Stick built with dimensional and rough cut cedar throughout, with the exception of two room additions. Lath and Plaster in orignal part of the house. CMU crawlspace foundation. Exterior finish consists of 3/4 ship lap with a layer of asphalt impregnated paper on the interior side and 30lb paper on the exterior side covered with a single course of raked ceder shingles set at the max 12" drop spacing.

Use R-15 non craft faced batts with a 4 or 6mil vapor barrier on the walls and coat wallboard with non PVA primer. Use blow in in the attic with a course of fiberglass batt over that and cover the ceiling wall board with a PVA primer.

Heat will be via electric hydronic baseboard heaters. I had a new roof installed last year with ridge vents and have since drilled out the bird blocks to add roughly 9sqft of free air space of low end venting. I may use an existing gas vent stack that is being eliminated to run a small exhaust fan to ensure enough air removal from attic space.



Last edited by Surlycraftsman; 11-26-2009 at 11:33 PM.
Surlycraftsman is offline   Reply With Quote
Old 11-27-2009, 08:37 AM   #2
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000

You are only supposed to have one vapor barrier/retarder
Otherwise moisture can be trapped between 2 layers


Scuba_Dave is offline   Reply With Quote
Old 11-27-2009, 02:57 PM   #3
Join Date: Feb 2006
Location: Minnesota
Posts: 938
Rewards Points: 500

Tar paper is water repellant, not to be confused with waterproof or a moisture barrier or a vapor barrier.

Do a google search for 15lb felt or 30 lb felt. You will find out what it really does and it's uses.

Poly should be on the inside and felt or house wrap on the outside.
MJW is offline   Reply With Quote
Old 11-27-2009, 06:31 PM   #4
Registered User
Join Date: Mar 2009
Posts: 11,730
Rewards Points: 526

For our Marine climate, don't use poly inside.

Felt paper has a permeability rating of 5 when dry and 60, wet. Asphalt coated faced insulation has a rating of less than 1. You shouldn't use either on the inside of the wall construction.

"I did notice that above most of the windows the paper was de-laminating from the plaster brown coat and that there was no interior tar paper above the windows." ------ please explain.......

Be safe, Gary in Tacoma
If any ads are present below my answer or words underlined/colored, I do not condone/support/use the product or services listed/linked to, they are there without my consent.
17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
Gary in WA is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Multiple wires under one staple WaldenL Electrical 15 08-29-2009 06:25 PM
multiple fixtures wired on a switch loop brotherman Electrical 7 07-09-2008 09:46 PM
Multiple Sub Panel Installation Handyman2007 Electrical 26 12-31-2007 05:47 PM
Feeding multiple subpanels with a single generator monsoon Electrical 8 10-02-2007 04:25 PM
Multiple lights/ceiling fans on 14/2?? sleepy23 Electrical 5 05-10-2007 10:27 AM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1