Hello, this is Rick from Rascom GreenBuild Services and welcome to RGS Net Zero Now – The Blog.

This is part two of our four part series on the SIGA line of membranes and flashing tapes. As previously mentioned, RGS is the GTA dealer for SIGA. In this part, we will be chatting about some of the SIGA product benefits.

What are the benefits of building with SIGA?
SIGA air and vapour barrier membranes and tapes are considered high performance products in the Passive Haus/Net Zero market. How is this achieved?

Let’s start with the interior vapour barrier membrane, SIGA Majrex 200.This is what is known as a smart vapour barrier membrane, meaning that while it acts like a typical barrier preventing moisture migration into the wall assembly from the interior, it will as well allow the wall to breathe tothe interior under the right conditions. Building science has taught us that while in the winter time the vapour drive in the house is to the exterior (hotto cold), in the summer if the interior space is air conditioned, or cooled,the vapour drive reverses.

How the Majrex differs from a 6 mil poly A
Typical vapour barrier membrane placed on the “warm” side of the wall will not allow for vapour to pass in any direction let alone to the interior.Under interior cooling conditions, with a 6 mil poly in place and the vapour drive reversed, the vapour would end up getting trapped inside the wall when it hits the poly. Smart vapour membranes allow the wall to breath in either direction.

How does a “smart” vapour barrier membrane work?
Smart vapour barrier membranes dynamically adjust their vapour permeance based on humidity levels, acting as a retarder when dry and allowing moisture to pass through when humid. However, SIGA Majrex isunique in that it won’t allow vapour to enter into the wall cavity from the interior regardless of the humidity.

SIGA Majvest 200 and 500 SA
Majvest 200 & 500 are exterior air barrier membranes. If you can stop air movement in a wall cavity, you will stop the moisture flow as well. Available in a staple on (200) and a self adhesive version ( 500SA), the self adhesive is workable down to -10 C and the adhesion is so good that there is no need for a primer. This stuff sticks so well that you need a chisel to get it off once its on!

Flashing Tapes
There are various flashing tapes to compliment the membranes. The Rissan line is an interior vapour closed tape to work with the Majrex and for detailing around the interior of window and door openings. It acts as atypical PE tape although with the fibres embedded in the tape less prone to splitting.

The Wigluv tape on the other hand is a complimentary product for the Majvest membranes and works similarly as it is a vapour open product, allowing the substrate to “breathe”, or allow vapour to pass. Wigluv is generally used to flash window and door openings as well as to close off any seams in the Majvest.

 

Next we have the Fentrim line of split tapes. Available in various widths, these are used to tape the windows and doors to create continuity of the air barrier. They come with a fold to transition from the nailing fin to the wall assembly.
A bit of interesting info learned during my Building Sciences studies: Traditional low end bitumen based flashing tapes are not vapour open but vapour closed. Interestingly, I found out that if for any reason that the wall assembly becomes  overheated by thermal gain ( exposure to sun) there’s a potential for the bitumen to become overheated and dissolve away leaving nothing but factory tape!Anyone remember that car commercial: “You can pay me now, or you can pay me later?”

Save a bit of money now on lower cost and lower performing materials,but the potential to “pay for it later” increases. In part three of this four part series, I will get into a bit more detail on the SIGA products that we carry. Thanks for reading. Rick Stacey