The majority of heat loss in an ICF home comes through wall openings such as windows and doors. You want to ensure that you have maintained as much insulation as possible around your openings. We have recommended V-buck for a number of years, but sadly they are no longer in business.
Disadvantages of wood window and door bucking
- Wood is an organic food source for mold, mildew, and other hazards.
- Wood is a potential food source for infestations such as termites.
- Wood will also decay over time and there is a potential for wood to react to the chemicals in concrete causing damage.
- During the concrete pour, if the wood is untreated (not just pressure treated) then it can absorb water. This could cause the wood to swell, warp, or twist. Once the entire system is finished there is no place for that moisture to go and it stays trapped in the wood.
- Wood is a poor insulator and is a thermal bridge, conducting heat through the wall around openings.
We currently recommend a product called Gorilla Buck. http://www.gorillabuck.com. It is an ICF bucking material made from the same components as BuildBlock ICFs and provides an insulated envelope between your the wall and your window and door openings. Its other advantage is an embedded plastic webs similar to BuildBlock ICFs that provide strong attachment points and easy placement of rebar around the openings.
If you want to use wood to ensure you have a solid attachment point across the face of the openings then we would suggest a product like Prebuck that is made from engineered wood and is extremely water resistant. If you choose to use pressure treated lumber, then we recommend painting the concrete facing side of your bucking with an undercoat to isolate moisture from the wood.