04:51PM | 11/30/06
Member Since: 11/29/06
2 lifetime posts
We are at the insulation stage of our new home. Fairly large home with cathedral ceilings. We have chosen the blown insulation for the majority of our home and the question arose regarding the use of a vapor barrier for the blown insulation. I know the ole plastic trick has been famous for years but is the same true for blown. I am hearing so many sides both pro and con and I am officially confused. Any assistance is appreciated.

I was all over the web and talked with local vendors and contractors and just could not find any consistency to the answer. Does any one really know or is this just a guess?

Appreciate any help and have a great holiday season everyone.

James Straley Chambersburg, Pa (I live in Southern Pa so I also found that location is important as well when deciding on Vapor barriers....aahhhhhhhhhh)


07:18PM | 11/30/06
Member Since: 04/25/05
1915 lifetime posts
It looks like you are in a mixed-humid climate.

Go through this and match up with what you are doing.

You have to control the movement of moisture, but that might not be a poly barrier.

But be warned with a cathedral ceiling can lights or other ceiling penatrations can allow moisture into and through the insulation to the underside of the roof where it can condenses.


07:05AM | 12/01/06
Member Since: 01/28/03
693 lifetime posts
The answer depends upon what type of blown insulation you chose to use.

Blown fiberglass would normally require a vapor retarder on the warm-in-winter side of the thermal envelope, but polyethylene plastic is a poor choice for mixed climate use. Such can lead to moisture issues inside framing cavities.

Blown cellulose requires no vapor retarder at all in most cases because of the manufacturer's installation sepcifications.

Even with blown fiberglass or other blown insulations, however, you may not want a vapor retarder at all depending on whether you have a continuous rigid foam on the exterior of the structure and your house is considered "unusually tight construction."

In such a case, the vapor retarder should not be used on the warm-in-winter side of the thermal envelope since it could actually trap moisture inside of framing cavities. No vapor retarder should be used in such a case allowing for deying to the inside of the structure (as in the Building Sciences Links cited in the previous post)

Pennsylvania Uniform Construction Code requires you to conform to one of several approved Energy Compliance paths for your structure, inncluding the 2003 International Energy Conservation Code, The US Department of Energy's RESCheck program, PA's Alternate Residential Energy Provisions, or others...

As a reminder, Pennsylvanai State Code requires you to first indicate to your local code office when you apply for permits which compliance path for energy conservation you will follow, be issued permits on that basis, and have a mandatory state energy inspection once installation is completed based upon your compliance path.


05:23PM | 12/01/06
Member Since: 11/29/06
2 lifetime posts
Appreciate the great information. I will sit down and discuss further with my builder and insulation sub.

Appreciate it!!

Click to reply button
Inspiration banner


Post a reply as Anonymous

Photo must be in JPG, GIF or PNG format and less than 5MB.

Reply choose button


Post new button or Login button

To test the boundaries of small-footprint living, interior designer Jessica Helgerson moved her family to a 540-square-foo... Filling an underutilized area beneath the stairs is a smart way to save space. Doing so with a stash of wood, however, is ... The Audubon Society inspired wallpaper in this Adirondack-styled mudroom will get you in the outdoor mood. Grab your coat ... Chalkboard paint opens up endless possibilities for customizing your dresser time and time again. Use chalk to label the c... A fireplace in the bathroom creates the ultimate setting for relaxation. Homeowners often choose electric or gas over wood... This roomy boot tray made from punched metal stands up to all the elements. Station it in your mudroom or at your back doo... There’s nothing like a new set of cabinet hardware to refresh a room. The possibilities are endless: Go modern, rustic, or... FLOR tiles are an affordable way to customize a carpeted floor covering for any space. Make anything from runners to wall-... Chalkboard paint features prominently in this elegant yet unpretentious headboard design. Add a new message daily to reflec... Salvaged boards in varying widths and colors make up the dramatic accent wall in this attic space. The high-gloss white of... The indecisive homeowner need not fret over choosing one (or even two) cabinet colors. The kitchen cabinets in this artist... Incorporate nature into your lighting scheme by securing a dead tree in a concrete mold and draping your pendant lamp from... Simple and striking, a couple of pieces of "lovingly used" furniture creates a special kind of charm. A weathered chair fo... First dress up your metal shelves with a coat of paint in an accent color that complements your kitchen decor. Then arrang... Dark wood shelving and a matching upholstered bench keep this closet sleek and refined. The large window brightens the sub...
Follow banner a
Newsletter icon Flipboard glossy Facebook Twitter Pinterest Youtube Rss icon