A ‘blow-out’ is a break in the form, generally due to the pressure from the liquid concrete during the concrete placement and/or consolidation. Fox Blocks ICFs are designed to maintain a high safety factor of pressure from the liquid concrete. Damaged forms or failure to support areas where forms have been cut leaving a large area of EPS between the web supports may cause a blow-out. Over consolidation may also cause a blow-out.
Fox Blocks recommends the Pre-Placement Checklist be reviewed for all wall assemblies prior to the placement of concrete, to find potential problem areas and install additional strapping or support to prevent blow-outs. Generally, for an Fox Blocks form, the size of a blow-out may be limited to the EPS between the webs, 6″ or 8″ wide by the height of one form. If a blow-out occurs, the concrete pour moves to another area on the wall, the hole is patched by replacing the EPS, installing wood support over the area, and then resuming the pour.
The clear R‑Value of an Fox Blocks is R22, however current Energy codes recognize the lack of thermal bridging in an ICF and the contribution of the mass concrete on the influence of the thermal performance. Whole wall calculations indicate a Fox blocks wall assembly provides an R24 rating.
The continuous double layer (inside and outside) of insulation, the elimination of thermal bridging and minimal air infiltration through the mass concrete wall assembly, allows Fox Blocks walls to performance in the high performance wall assembly category. Completing the envelope with energy efficient windows and doors and roof insulation, Fox Blocks homes can easily meet and exceed energy code requirements and exceed the minimum requirements for Energy Star and EnerGuide. A Fox Blocks structure requires 44% less energy to heat and 32% less energy to cool.
Fox Blocks has conducted numerous fastener tests for pull-out strength and shear capacity for various fasteners – screws, ring shank nails and staples into the plastic webs. The recommendation for interior and exterior applications of finish materials is for the use of screws which provide the best holding capacity into the plastic webs or fastening strips in the forms which are identified on each block.
The EPS insulation does not provide any holding capacity for fasteners.
All building codes in the USA and Canada specify that plastic insulation (EPS) must be covered by a thermal barrier equivalent to 15 minutes of fire protection in habitable spaces. This is achieved with ½” gypsum board or an equivalent material. Fox Blocks has specific fire testing that proves regular ½” gypsum board with regular drywall screws fastened into the plastic webs remains on the wall for the required 15-minute time period.
Fox Blocks walls are designed as reinforced concrete walls, with steel reinforcement bars specified to be installed vertically and horizontally, as the walls are built. Typical reinforcement bar sizes used are #4 or #5 (10 m or 15 m).