With rising concerns over global warming and energy efficiency, construction materials like EIFS (“stucco”) and ICF (Insulated Concrete Forms) have become increasingly popular. Both incorporate varying thicknesses of insulation to decrease the amount of heat lost (during the winter) or gained (during the summer), thereby lowering the amount of heat that needs to be generated/removed. This not only means less fossil fuels are used, but that what you pay to heat and cool your home is decreased. While EIFS is seen in both new construction and renovations, ICF is primarily new construction, but the two products are not mutually exclusively. Actually, one of the larger EPS manufacturers in Toronto supplies the insulation for both products.
EIFS has been around for decades in various forms, while ICF has really only begun to take off in the last 10 years or so. EIFS newest form incorporates a weather barrier with drainage which has been shown to be the most effective at managing moisture, compared with any other cladding. ICF lacks the weather barrier and drainage channels to properly accommodate moisture that will at some point get into the wall.
So what is the correct method of applying EIFS to ICF? All joints in the ICF should be taped with EIFS mesh, and a full cementitious weather barrier applied. This surface should serve as the base of which to apply a full EIFS system including the insulation and vertical channels of adhesive. This provides a drainage layer to ensure the insulation will last as long as possible. ICF being styrofoam itself, one could even groove out vertical channels into the ICF forms through which moisture could drain out when placing your EPS board layer on top.
Adding another layer of insulation will increase the R-value, though typically not to an appreciable degree. ICF walls themselves provide more-than-adequate resistance to thermal transmission through walls. Ensuring that areas such as the roof is properly insulated, and windows are properly sealed would be an intelligent idea, as they would likely be the weak points on a home.
More often than not, what is typically done is to simply apply the mesh, basecoat and finish coat directly over top of the outer layer of insulation in the ICF. While the styrofoam used in the ICF is suitable to apply EIFS over, contractors should make sure it is free from dust, dirt and grease (it’s not uncommon to have dirty ICF forms). Doing this turns the EIFS into a barrier system as opposed to a Dual-Barrier, it will entirely lack a drainage layer which is the key to ensuring walls last as long as possible.
From a design standpoint, it would be simple to add stucco reveals right into the ICF itself as a unique architectural feature.