Vapor Retarders, Sealants & Tapes

Vapor retarders are an integral part of creating your low-impact home. With high insulation values we need to try and keep water vapor out of cold areas and voids in the insulation envelope.

Though most often called "vapor barriers", we prefer the term vapor retarder. It is virtually impossible to completely seal your home from vapor, because of basic physics. We have accepted this fact and so prefer to call it a retarder since all we can hope to do, at best, is slow vapor transfer.

At the foundation level we ask the vapor retarder to prevent moisture from migrating into the structure where it can cause mold, mildew and rot problems. In this instance we also look to the retarder to help prevent soil gases, namely radon, from passing into the residence as well.

In the case of walls and ceilings, we look to the vapor retarder to slow down the transfer of moisture into the insulation cavities where it can condense, with the net result of lowering insulation values, as well as causing mold, mildew, rot and insect problems.

This is one of the major reasons that we prefer Structural Insulated Panels (SIP's) for our designs. As the SIP panel core is solid, and in effect a continuous vapor retarder, there is no place for condensation to occur! In other insulations...not so much. For more on SIP's, please see our SIP page Here.

Designing The Vapor Retardant System

Meanwhile, back at the vapor retarder, in any insulation that moisture vapor can travel through, there will be some point within the insulation that the dew point will be reached. This will allow the vapor to transform from a gas to a liquid. This effect is even more exaggerated at any breaks or voids in the insulation by a phenomenon called vapor drive. The laws of physics dictate that fluid materials are in a constant struggle to equalize themselves across differing values. In a cold climate the relative humidity inside your home might be 40-50%, while outside the humidity might be 20-30%. As this is trying to equalize, the moisture will find any break in the system and create vapor drive there.

What we strive to accomplish with a vapor retarder is to slow or limit this transfer. All non-solid wall construction will "breath" to the outside to some extent. Our goal is to limit the vapor travel to a low enough level that moisture can not build up in the cavity. Considering the consequences of mold, mildew, rot and insect infestations, not to mention the health effects on your family, using a stout vapor retarder should be a prerequisite. Properly detailing the installation as much as possible is the next step.

Building science testing in recent years has shown that the most common retarder used, polyethylene films, can break down under normal circumstances. We should be looking for better and longer lived films to use. Enter Tu-Tuf films! Tu-Tuf films are cross laminated using virgin high-density poly films. This gives Tu-Tuf high tensile strength and great puncture resistance. Through it's use on Timberworks project sites we have seen how it outperforms standard film in every instance. Tu-Tuf is also an integral part of our construction steps to seal out radon vapors!

For our selection of Tu-Tuf vapor retarder films, sealants and tapes, please Click Here.