Air Barriers: Increasing Building Performance, Decreasing Energy Costs

This article is a very good source of information for all.

Also available for Continued Education.

I listed a few of the building wraps available and their performance specification for comparison. 

Perm ratings differ by quite a bit.

Permeability, rated in perms, is a measure of the transference of grains of water through a material at a standard vapor pressure and temperature. Vapor retarders have permeability ratings of 1.0 or lower. Asphalt felt paper (tar paper]( has a permeability rating of 5, so it is inappropriate as a vapor retarder.

I have provided these different products and their specifications for comparisons.

Product Name: Tyvec
Water Vapor Trans. Rate
58 perms

Air Leakage Rate (Air-Ins)
0.007 cfm/sq ft @ 75 pascals


Water Vapor Trans. Rate
13.7 perms

Air Leakage Rate (Air-Ins)
0.0023 L/S-sq m @ 75 pascals


Water Vapor Trans. Rate
ASTM E 96, Procedure A: 125 g/24 h•m2

Air Leakage Rate (Air-Ins)
ASTM E283: 0.017 CFM

                    GreenGuard  **Water Vapor Permeance**

ASTM E 96, Procedure A: 105 g/m2/24 hrs (@75ºF/50% RH)

Air Leakage Rate (Air-Ins)
ASTM E 283: 0.03 cfm/sq ft (@ 75 pascals/25 mph)

                    Prime Wrap  

Water Vapor Permeance
ASTM E-96-A: 5-15

Air Leakage Rate (Air-Ins)
ASTM E283: 0.017 CFM

                    Valeron Vortec  **Water Vapor Trans. Rate**
  • ASTM E-96A: 50 gms/m2/24 hrs @ 50% RH

  • ASTM E-96A: 6.5 perms
    Air Porosity (Gurley Hill)
    TAPPI T-460: 8.1 sec/100 cc

                    Green Guard RainDrop   **Water Vapor Trans. Rate**

ASTM E 96, Procedure A: 10 perms (@75ºF/50% RH)

[size=3][FONT=Times New Roman]Water Vapor Permeance[/size]
ASTM E 96, Procedure A: 73 g/m2/24 hrs (@75ºF/50% RH)


Look at the difference in the Product Performance and make your own decision as to which is better.

Hope some enjoy.

Marcel :slight_smile: :smiley:

30 lb felt has a perm rating of 5, 15lb is over 10 and is considered permeable

When looking into building wraps or (WRB) Weather Resistive Barriers, one has to look at the best suitable material that will serve as ;

Air Barrier

Vapor Barrier

Rain Barrier

Copied from;
What Materials Should Be Used?

Water Resistance: Perforated housewraps do not resist water as well as the non-perforated types. Building felts/papers are resistant to water penetration but the extent of resistance varies greatly depending on their construction. Typical 15# building felt is less water resistant than most non-perforated housewrap types but more resistant than the perforated types.
Recent research indicates that water resistance decreases when surfactants (surface-acting substances), such as those found in cedar and redwood siding and sometimes in other exterior finishes, are introduced to water. As surfactants are picked up when moisture moves through these finishes, they reduce the surface tension of water, allowing it to pass through a much smaller opening. Most non-perforated housewraps still have better water resistance than building paper even after surfactants are introduced.
To alleviate this problem, coat all wood siding sides with a clear water-repellent wood preservative, then install, prime, and paint with two finish coats. Furring out siding will also help prevent moisture problems.

Vapor Permeability: All weather-resistive barriers are vapor permeable, which is generally desirable because it promotes drying. However, in hot, humid climates, a vapor retarder may be preferable. Building papers and felts become more permeable as they get wet, which may be an advantage if moisture gets behind the barrier.

Air Resistance: All these materials resist air movement, but it is critical that all seams and penetrations are sealed. Building papers are not usually sealed in this manner, so they are generally not considered air barriers.

Moisture Absorption: Housewraps are plastic-based materials and do not absorb moisture. Building papers and felts vary widely in their construction but all may absorb some moisture under certain conditions. In some cases this may be an advantage—if moisture gets behind the barrier, the barrier will absorb it then slowly dry out, protecting wood materials.

Durability: Housewraps are very tear resistant. Building papers/felts vary widely in this regard but are generally more prone to tearing than housewraps. Tear resistance may be an advantage during installation and perhaps afterward if left uncovered and subject to wind damage. Housewraps vary widely in UV resistance, as well; building papers/felts are generally not very UV resistant. This may be an important consideration if siding will not be applied for some time. Housewraps are very moisture tolerant, while building papers/felts may deteriorate over time if repeatedly subjected to water.

Hope this helps. :):smiley:

Good one…

Marcel, what is the weatherization/energy audit market in Maine looking like these days?

I find around here that people can’t seem to conceptualize energy loss until it’s wintertime. They seem to be able to withstand the blazing heat but as soon as the temperature hits about 50° and below they start jumping through the window about weatherization issues.

I know your market is slow, but energy performance and building assessment to achieve this performance is a significant investment were people can get money back after their initial investment is paid off in a significantly short period of time.

I have an alternative program to all this weatherization hype. I also have a cousin in your neighborhood that is a senior executive for a local bank that may be interested in generating loans for this type of home improvement.

Have you given this any thought in relation to the extremely poor home residential market in Maine?

I love the winter. My uncle lived next to George HW. Bush in Kennebunkport and we used to go there for Christmas all a time. Maybe we can get something brewing. I would even be excited about coming by for Christmas! :slight_smile:

Hi Dave and thanks for the interest, and Hope all is good with you buddy.

It appears that I am surrounded with contractors that do this type of work.

Right now, my only interest is work another 3 years at the shipyard until I recieve medicare if it still exist then.
I have good benifets there and don’t do enough inspections to invest in a camera or equipment to persue this energy auditing.

I am doing well with a few commercial inspections and home inspections here and there.

I still do some light remodels on weekends If I have too also. :wink:

Once I retire, that would give me some extra time to persue some of these avenues that would certainly interest me then.

I never thought I would have ended up in a shipyard after 45 years in the building industry. :slight_smile:

It is what it is and thanks for being there.

Oh, and I almost forgot, if you should ever come this way, better let me know. It would be a pleasure to meet again.


Big time thanks.
just getting into perm rating Marcel.
Hope all is well.

I started using house wrap in the early 1980’s. New system for me at that time and had little thought behind the application although I followed the installations to the letter.
They were using polyethylene 6 mil behind stapled to the ceiling joists before they installed the sheet rock as the vapor barrier. I was managing the construction of the home. I said craft with foil reflective side facing the warm side of the home. My boss listened. I was just being introduced to vapor and reflective barriers.
Last (Tyvek) was 5 years ago on a siding job. I would like to know if I made the second floor too air tight.

You can never make a building too airtight; you just have to know the other things to do concurrently when a building is being made airtight.

Marcel, I will not pass you by like I did to Peter in Alton, NH this summer!

Didn’t know he moved till just after I got back!

Never knows when a Nore-easter may blow and I show up for a cup of coffee! :wink:

GPS will bring you right to my driveway David. :wink:

Just Goggle my website for the address.

To bad we missed each other, would have been nice to see you again.
Next time.

Maybe in our travels, we could all meet somewhere where it is all convenient for all. :slight_smile:

I would be up for that!!!

Controlled ventilation must be there or it can cause adverse conditions to arise within components of a home as you well know.
I see suspect organic growth becoming more prevalent an issue in homes I am inspecting lately. I will try to make some sense of it as I build my business and home inspection exuberance.
Ether insulation installers or the self proclaimed tradesman seem to be the biggest issue. Not understand the difference between vapor barrier or vapor retarders and ventilation.
Shame for the individual that opens up that can of worms because it will be found eventually.

I remember making an a s s out of myself when a very intelligent individual on the subject of insulation and air tight homes was posting over a year back. He mentioned about an insulation form installer injecting form into every ceiling electrical box and light switch box also but could be mistaken.
I wish several things had not happened and the situation be resolved including the installers enlightenment upon reflection. Mostly I reflect upon my words and thoughts HI. They were minced with a bias and negative attitude. All of my own making. I should have and wish I had opened a fuller formal dialog & discussion in hopes that other INACHI members would be rewarded by the knowledge. Hind sight is 20/20 they say and wish I could see into the future, if just to see the errors of my ways, how words can effect other and not for monetary gain. That being said.
You never know HI, :roll: If there’s a slim chance he runs by this post I hope he sees he did effect this fool after all.
I’ll leave him a message ether/or. You never now.
Sorry Brian . All the best.

Looks like more individuals are concerning themselves with energy and auditing in your neck of the woods Marcel.
Thanks for the insight.
Time to add another feather to the Montreal Home Inspection Services Inc. cap.
All the best to you and yours.