Comparison of smart vapor retarder and air barrier products

When it comes to constructing a high-performance building, the choice of membranes is important to ensure a continuous and watertight envelope. Here is an overview of the solutions available and the most suitable for wall assembly for our Quebec climate.

Back to appellations

Vapor barrier membrane

Also called polyethylene or vapor barrier, this membrane limits the diffusion of water vapor in the walls from inside the house (kitchen, shower, etc.). In English, we speak of Vapor Retarder (VR) or Vapor Barrier (VB).

Intello vapor barrier, 475 High performance Building supply, August 2019

The main purpose of a vapor barrier is to protect the wall from moisture. It must therefore be impermeable to water vapor, the humidity being mainly evacuated by the ventilation system of the building. There are so-called “intelligent” membranes that allow water vapor to be evacuated through the wall, without causing any damage under certain conditions.

Air barrier membrane

Known as an air barrier, this membrane protects the walls against wind, water, in short, bad weather. In English, the terms used are Air Barrier (AB) and Water Resistance Barrier (WRB).

Note, after reading several articles dealing with high-performance buildings, the terms Water Sheeting Surface (WSS) and Thermal Barrier (TB) can be confused when designating types of membranes. However, these terms refer to characteristics ensured respectively by the exterior cladding and the insulation in the wall.

Vapor barrier comparison exercise

A few details about our approach:

• The information used to carry out this study is based on the technical data sheets of the suppliers available on their website, dated February 2021.
• The prices were collected during this same period and are naturally subject to change over time.
• The analysis focuses only on wall membranes, bituminous membranes are therefore excluded from the study.
• With the exception of the polythene in the vapor barrier section, all the other membranes presented can be considered as performing. The objective of this article is to understand their differences in order to make a more informed choice.

What is the location of a vapor barrier?

The location of the vapor barrier membrane in the wall depends on the climate in which it is located. Indeed, the latter must be installed on the side from which the humidity (water vapor) comes. In a cold climate like ours, humidity mainly comes from inside. The vapor barrier is therefore installed between the gypsum (or plywood) and the wood studs.

What are the important characteristics of a vapor barrier?

Vapor barriers are compared according to 5 criteria, each with a different weighting, presented in the following table. There is also the weighting of these criteria.

The previous table also allows us to observe the weighting considered for each criterion according to consumer requirements:

1. The price is obviously one of the main considerations;
2. The water vapor permeability is also important because it is the reason for the presence of the membrane in the wall;
3. The humidity variability of the membrane allows the wall to be more resilient. Indeed, in the event that the interior relative humidity is too high, this property allows the walls to "open its pores" to evacuate the excess humidity to the outside;
4. Finally, in order to obtain the Passive House certification, the membrane as well as any other component must be PHI certified in order to facilitate the modelling of the building in PHPP. This certification is also a guarantee of quality since it is held to the highest standard in the industry.

The final grade is obtained following a weighted average of the results displayed. To make the comparison easier to read, symbols are used as notation: 3 symbols indicate a maximum score of 3/3. Only exception for the price, where 3 dollar symbols indicates a very expensive product (ie a rating of 1/3).

1. The best students in the class is the best value for money. It is composed of the membrane SopraSeal HVM et de la Clima Control de Rothoblaas. The unique between these two membranes lies in the resistance of the membrane to tearing. This factor is taken into account during storage and handling. Once installed, these two membranes are very similar;
2. The second group is made up of membranes that perform better but are less affordable. We find there the Majrex 200 de Siga et l’IntelloPlus sold by 475 High Performance Building Supply. Very similar, these 2 membranes are very present in passive houses, and rightly so. In addition to being very efficient, these two membranes are easy to install;
3. Finally the third group represented by Neovap are used more in code construction and accessible to all, however their level of performance is lower than the first two groups.

These membranes have the most competitive prices on the market but also the lowest performance because they are not hygrovariable. When you know the importance of a good seal, this is certainly not the place (of the house) where you have to cut corners.

Regarding the availability of these products, almost all of them require going directly through an authorized distributor. High-performance products are little or not accessible in renovation centers, such as Réno-Dépôt or Home-Depot because there is too little demand.

Air Barrier Membrane Comparison Exercise

Although certain types of insulation or building substrate can play a role as an air barrier (AB), this is a membrane only. The idea is to compare the membranes available on the market that ensure a tight and waterproof envelope. This membrane being installed on the cold side of the house (outside for a cold climate), must be able to let water vapor escape in order to guarantee a dry wall and thus avoid unpleasant and costly surprises.

What are the important characteristics of an air barrier membrane?

In the same way as for vapor barriers, weather barrier membranes are compared according to 6 criteria, each with a different weighting, presented in the following table.

In the same way as before, the criteria that have the greatest weighting are the price and the air permeability of the membrane, which constitutes the "raison d'être" of the membrane. The resistance to UV exposure as well as the installation method come next with a weighting of 2. The resistance to UV is not to be neglected for this type of membrane because the installation of the exterior covering is generally done long after the weather barrier has been installed. Prolonged UV exposure will cause deterioration of other physical properties of the membrane. Regarding the installation method, a stapled membrane perforates the building envelope and is therefore not as efficient as a self-adhesive membrane. Finally, tear resistance and water vapor permeability are less important elements because they are very similar between these membranes.

The parameters having been established, we can now dive into our comparison study, the results of which are illustrated in the following table.

The method of evaluation and calculation of the “note” value is carried out in the same way as before. As with the analysis of vapor barriers, 3 categories can be distinguished.

1. The 1st group is once again made up of Soprema products (SopraStick VP 1100) accompanied this time by Tyvek from Dupont. These products offer the best value for money. Widely used in Novoclimat-certified buildings, Tyvek must be installed a maximum of 4 months before laying the exterior covering, otherwise this performance will decrease. The self-adhesive installation of the SopraStick VP membrane makes it possible to completely adhere to the substrate, optimizing the performance of the membrane to the maximum.
2. The 2nd group consists of products Majvest from Sigan, Solitex Mentho Plus from Pro Clima et Delta Vent by Dorken. Once again, this group includes high-performance membranes that are not financially accessible to everyone.
3. Finalement la 3e catégorie est composée de la Traspir 110 from Rothoblaas. Although effective, this membrane does not stand out elsewhere. Its low resistance to U.V. will force you to speed up the installation of the exterior covering.

What you must remember

The market for air and vapor barrier membranes is booming. These membranes, which are essential for good insulation, are becoming more and more intelligent in adapting to the climatic conditions in which these new buildings and dwellings are built.

Nevertheless, the price remains for the vast majority of consumers and builders the number 1 decision factor, well beyond the performance, the life cycle of the product, and the carbon footprint that these membranes can have.

At psb, our favorites are the products offered by Soprema, Siga and Pro Clima both for their performance and their ease of installation by our teams of carpenters.