Vapour barriers


Now that the weather is quickly becoming more comfortable indoors than out, this is a great time to discuss indoor air quality.  We will start with vapour barriers (VB’s).  There are several approaches to vapour barriers; a generation ago there was a huge effort to implement VB’s in homes.  NRC Canada through R-0000 series made it very clear that VB’s were extremely important. Since then much has changed and come to light regarding this integral part of any building envelope.

In the 70’s it was clear that heating and vapour flows in building were integral, and that controlling them was key to a comfortable indoors.  VB’s also helped keep precious heat from escaping.  Today the average track home builder doesn’t really believe in a completely sealed vapour barrier. Many builders feel that VB’s should be installed and that the transition from one floor to the next or from the basement to the ground floor shouldn’t be continuously sealed. For them the building should breathe and that completely sealing a VB’s leads to sick building syndrome or at least a build up of unhealthy air in the home.  Couple continuously sealed vapour barrier with agglomerate based furniture and petroleum derived carpets and the air content in the home becomes overwhelmed with V.O.C.’s.  When your vapour barrier is properly sealed these gases have nowhere to escape and the air in the home can become unhealthy.  Builders usually only include very simple mechanical systems with new homes.  The only line of defence is a home owner that will flush the homes air on a regular basis; unfortunately you cannot rely on individual monitoring of indoor air quality. This is another reason why GC’s don’t seal VB’s properly.

Commercial buildings have the solution to this issue, in them VB’s are permanently sealed, but these buildings have sophisticated mechanical systems that are monitored. This is the solution to a properly sealed VB.  Your mechanical system has to be properly designed and monitored to avoid poor indoor air quality. There are several additional pieces of equipment that are required to properly monitor indoor air quality. First an air exchanger is required with a heat recovery unit.  This will allow the system to change the air in the home and recover the energy stored in the air before flushing it. Second, you need a monitoring system. This has to be designed into your mechanical system and co2 sensors should be placed in every zone to monitor the air quality.  This is included in the latest national building code.

It is recommended that your home be divided into as many zones as possible to allow for proper response to climate requirements. The issue is cost; sophisticated mechanical systems are pricey and can significantly add to the overall cost of the home. The trade off for high upfront equipment cost is reduced energy cost over the life of the system. When you do the math, these systems pay you back in savings not to mention increased comfort and a healthy indoor environment.

If you need a permit we can help call 514-839-3138.

Author: Tectonic

We have over thirty years experience.

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