Air Barriers: Increasing Building Performance, Decreasing Energy Costs

[Marcel R. Cyr]

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

Also available for Continued Education.
http://archrecord.construction.com/r...onttyvek-1.asp

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


Typar

Water Vapor Trans. Rate

13.7 perms

Air Leakage Rate (Air-Ins)

0.0023 L/S-sq m @ 75 pascals


ProWrap

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)

Water Vapor Permeance

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