If an entire home is clad with Exterior Insulation Finishing Systems, it's a possibility that it might be aesthetically optimal for the chimney to be clad with EIFS too.
Risk of fire
There are two large concerns with regards to EIFS being installed on chimneys.
- EIFS is not a non-combustible material.
- Expanded polystyrene foam, the foam insulation board, has a relatively low melting point.
Wood is also not non-combustible, so the flue and fireboxes are usually created to be suitable for use within wood enclosures with no problem. It's at the top of a chimney where the EIFS issues may present themselves. EIFS chimneys may also face sparks coming from inside the chimney which can easily land on them and start a fire, so these risks need to be mitigated. If the chimney uses an old fashioned stove pipe, it's important that the heat is directed away from the EIFS as it could melt and begin to flow down the sides of the chimney.
Lightning rods are sometimes placed on chimneys. If the chimney uses EIFS, any lighting rods or similar devices should be installed away from the EIFS using an insulated mounting so that if they do get hit by lightning, the EIFS won't melt or catch fire.
Aside from heat issues, using EIFS on a chimney takes care. The chimney may be shaped in such a way that it results in a slope, exposing the EIFS to more than its fair share of elements and water. The shape of the roof the EIFS chimney is installed on may also direct water right at its base, saturating the EIFS. To prevent water intrusion on an EIFS chimney, a system of proper roof sloping, adequately backwrapped terminations and flashings to direct water away from the roof's edge (so it doesn't run down into the wall) should be implemented. Keep in mind that prefabricated and pre-shaped kickout flashings are available just for this use, and they will save a lot of time.
Chimney tidbits to consider
Sometimes it seems like it might be a good idea to continue the chimney material down inside the house and over the fireplace, as is commonly done with brick and stone. EIFS can't be used inside because of most fire codes, but the finish can be painted over the indoor walls to achieve the same look.
Using foam shapes that resemble stones can add a desirable look to EIFS chimneys, but it is important to ensure the same EIFS system is used and that it's from the same manufacturer so you don't end up mixing materials from two different manufacturers. Mixing materials from different manufacturers voids warranties and removes any accountability as to whose materials they are.
One last chimney tidbit to consider is that as with wanting to follow the same "look" down the chimney on the inside, the same may be desired for the outside. If this would have the EIFS terminating at or below grade, forget about it. Most building codes won't allow it, and it will only result in the EIFS turning to mush, separating, or inviting bugs such as termites into a home.
Not so much a functionality issue, but soot from combustion byproducts that land near the opening of the chimney will run when it rains or snows, leaving streaky black stains that are very difficult to remove from the EIFS. Properly installed chimney caps or metal flashings can assist in preventing this problem.
EIFS looks great when it's used on the whole home, or on part of the home. It can be nicely mixed with bricks and stone or stand alone on its own. Mixing different claddings on a chimney can have a nice effect, or it can be left as EIFS-only if special care is taken.