Water and EIFS Water Vapour
Water and Exterior Insulation Finishing Systems have a tumultuous relationship, one that is very much responsible for bringing an unfairly deserved reputation and a plethora of bad press to EIFS. Most of this concern is centered around water in its most basic form, liquid. Liquid water is not a large problem for EIFS as it can leave the materials quite easily, either by running off the surface or through drainage components.
However, when water is in its gaseous form, water vapour, it brings much more complicated issues to EIFS and their maintenance and installation. It should be noted that water vapour returns to its native form as condensation, which is also an issue when conditions are just right, and in frigid Toronto winters, the condensation can expand when it freezes.
This water vapour naturally exists in the open air depending on humidity levels, and water will either “permeate” the surface of the EIFS in water vapour form and very slowly make its way throughout, or trickle into it because of gaps and cracks.
Consequences of water vapour
EIFS can be described as waterproof, but this term is misleading. Water will indeed be mostly shed, but water vapour can penetrate it. EIFS are certainly not waterproof enough to be used where water may frequently pool, such as on a roof. Water vapour, on the other hand, passes through the system with ease, and can become trapped within it. The water vapour moisture will then pass through to the underlaying wood and other materials, like drywall. This leads to mould, mildew and rot, and a weakened structural integrity.
In EIFS, water vapour and subsequent condensation will often occur between the finish and base coat, or if paint is used over the finish, between the finish and the paint. If condensation occurs here the paint’s appearance can be severely affected, and blistering can occur, much similar to the bubbling of paint near a poorly-constructed windowsill.
When water soaks insulation media, its functionality is severely lessened as well, which can negate one of the more important purposes of EIFS – insulating homes and buildings.
All of the components of EIFS are able to transmit water vapour, and it can come from either inside or outside of the exterior wall. Because EIFS is such a tight material, it doesn’t ventilate very well if it becomes overly moist. Basically, the water becomes trapped behind it.
Mitigating water vapour issues
A decent vapour barrier is necessary to prevent water vapour from getting into places it shouldn’t, and faulty vapour barriers can allow much more water in behind the materials than would enter the material naturally through the surface. Quality craftsmanship with regards to the vapour barrier is essential for preventing water issues within the EIFS.
With regards to drainage EIFS, the additional waterproofing of the outside lamina can have a backfire effect, where it even further prevents the water vapour from escaping, although it can drain out effectively from behind.
There are some components of EIFS that require extra attention when it comes to moisture issues. Some of these include the use of uncommon insulation materials or insulation that is thicker or thinner than normal. When EIFS is repaired, placing another layer of paint or lamina on top of previous lamina as well as using sealants or epoxies on the exterior of the lamina all can prevent moisture from getting in, but also prevents it from escaping the material.
Specific climates may also call for special considerations. Some of these temperature and humidity concerns could include a building that is very high in humidity but in an area with very dry, cold winters, such as Ontario. They can also include Ontario summers, where the outside is hot and very moist but the inside of the building is over air conditioned and dry. Wet and cool climates like those areas next to the sea or large bodies of water during cooler months can also be a concern.
EIFS is a high-performing exterior insulation, and when it is installed with condensation and water vapour in mind it can pretty much mitigate most of these issues on its own. However, special care should be taken to ensure that the EIFS is not at risk of retaining too much moisture, which will result in some of the problems that cause it to have a bad reputation.