Exterior Insulated Finishing Systems (EIFS) are multi-layered exterior wall systems that are used on both commercial buildings and homes. EIFS typically consist of the following components:
- panels of expanded polystyrene foam insulation fastened with adhesive to the substrate. Sometimes the foam insulation panels are mechanically fastened to the substrate (i.e. held by screws), but usually they are held there by adhesives,
- a base coat that is towelled over the foam insulation panels,
- a glass fibre reinforcing mesh that is laid over the polystyrene insulation panels and fully embedded in the base coat, and,
- a finish coat that is towelled over the base coat and the reinforcing mesh. The base coat, mesh and finish coats are usually 1/8 to 1/4 inches thick.
Here are two types of EIFS in use:
1) Water-managed EIFS – this type envisions some water penetration into the surface and incorporates water-management features (flashing, weeping, drainage plane and water-durable substrates) to ensure that water, which breaches the exterior finish, will quickly exit the system.
2) Barrier EIFS — are generally designed to divert all water at their exterior surface. They are EIFS are non-load bearing exterior wall systems with four primary components. Behind them are the wall substrate and wall studs. The substrate is usually gypsum board, plywood or oriented strand board sheathing. In some cases, the substrate may also be masonry. In Europe (where EIFS originated), the EIFS substrate is usually masonry.
Benefits of EIFS – The benefits of EIFS can include increased energy efficiency and virtually unlimited design flexibility. EIFS are definitely not a do-it-yourself wall-cladding project. They should be installed only by experienced applicators have completed an EIFS manufacturer’s training program.
Concerns with barrier EIFS – In one study, the National Research Council of Canada (NRCC), authorities on exterior building envelopes, found that water was intruding into the exterior walls near window assemblies, doorways, hose bibs and roof rakes in certain situations. In particular, vinyl combination windows were problematic, and many homes did not have the flashing and sealing recommended by EIFS manufacturers. There was little evidence that water had penetrated through the field of EIFS cladding. Because barrier EIF systems provide no means for allowing water to escape the wall cavity, intruding water is trapped inside the system, where it can remain for extended periods of time and eventually damage and even rot wood framing, sheathing and other moisture-sensitive building components. In the specimens without penetrations (windows) but with different base coat thickness’, results revealed that both wall assemblies were relatively airtight and watertight.
The same tests were conducted on the water-managed specimen “as-built” and with the various defects introduced. Results indicated that the drained-cavity design managed water penetration. No water was evident in the OSB or the stud cavities even though there was considerably more water behind the cladding. Water passed through the defects typical of those found in actual homes, and the drainage cavity directed that water out of the wall.
Homes should be monitored for possible moisture problems. Considerations include:
Windows – on wood windows look for peeling paint, a telltale sign of a moisture problem. If you see a gap where the sill and jamb of the window frame meet, it should be caulked with the window manufacturer’s recommended sealant.
Openings — wherever EIFS are installed and meet another material, for example window frames, doors, light fixtures, hose bibs, dryer vents, etc. they must be sealed appropriately. Check to make sure the existing sealant is soft and flexible.
Flashing — Good construction practices include flashing details that are installed so that water is directed out and away from the house.