Insulating Concrete Forms (ICFs) have been around since just after World War II. While they offer many benefits, there are still some performance issues which can affect interior humidity and lead to water leakages.

A new study from Canada is investigating how Insulating Concrete Forms (ICFs) can be used more effectively as walls in building structures.

ICFs are polystyrene forms that stack like blocks with steel rebar inside. Once the blocks have been assembled, concrete is poured into their hollow core to create walls. They are either shaped into pre-formed interlocking blocks or separate panels connected with plastic ties.

They are easy to install and highly energy efficient. They provide not only continuous insulation on both sides of the wall, but also a backing for drywall on the inside and stucco, lap siding or brick on the outside.

“In Phase 1 of the tests, we looked at several traditional methods of making ICF wall systems and interfaces,” said Brian Hubbs, the senior building science specialist at RDH Building Engineering Ltd., which led the B.C. Ready-Mixed Concrete Association’s (BCRMCA) ICF Steering Committee in the performance of tests.

“We found that some commonly used installation methods have lower than expected performance levels. But, we also discovered that all ICF cores exhibited a very high resistance to both air and water infiltration.”


The primary technical concern for using ICFs is determining the best practice for addressing water intrusion in windows. This was a fundamental component of the study.

In Phase 2, RDH Building Engineering tested a total of 12 prototype wall panels consisting of ICF concrete walls with different combinations of moisture barriers, opening buck details and window installation details to determine the leakage paths of the panels. The tests measure expected air leakage and simulate performance during one-in-10 year rain and wind events.

“We obtained performance levels normally seen only on high-rise cladding and glazing systems,” Hubbs said. “The results are very encouraging and provide several moisture management strategies that could be developed into working details to be constructed and tested full-scale in field trials.”

Hubbs added that the results of the testing program will form the basis of an ICF best practice guide and industry-standard details and installation practices.

“We are of the view that ICF building construction represents one of the superior construction systems to address energy conservation and earthquake resistance objectives,” said BCRMCA president Charles Kelly. “This is true for residential, mid and high-rise, and commercial construction. ICF construction is available today to meet Passive House and Net Zero energy goals.”

Douglas Bennion, chairman of BCRMA’s ICF Promotion Committee, said market acceptance of ICFs has been increasing since the 1990s, and referred to the solution as “concrete with brains.”

Although ICFs can be used in all types of buildings, Bennion suggested their most practical application was for multi-family rental buildings.

“They keep the cost of operation low, which is a very attractive benefit to someone who owns rental apartments,” he said.

Two subsequent phases to the study are now scheduled to take place. Phase 3 will field-test a house, while the final phase will see anticipated revisions to Canada’s Homeowner Protection Office envelope guide.