Using Rigid Exterior Insulation Under Hardishingle Siding

The boards are available in several thicknesses and r values.

Using rigid exterior insulation under hardishingle siding.

The nails have a plastic cap that keeps them from damaging the foam. 1 inch and 2 inch thicknesses are common. And even though some manufacturers call it rigid foam insulation for the purpose of vinyl siding it basically has the same insulating value as a piece of plywood. Continuous insulation under new siding has become a popular way to improve energy efficiency on an existing home because it addresses a problem known as thermal bridging.

Rigid insulation provides thermal protection and it can also serve as an air and moisture barrier. Several manufacturers of rigid foam insulation recommend metal strap bracing as a structural solution for foam sheathed walls. To secure the foam use two inch cap nails. The method works for both new construction and remodeling and doesn t affect siding and trim details very much.

Always follow the manufacturer s instructions for installing rigid foam insulation. These irregularities should be corrected before the siding is installed. How to install rigid foam under siding. Using exterior rigid foam board insulation is a great way to make a building more energy efficient quieter and more likely to prevent moisture infiltration problems.

Fit the rigid foam insulation snugly and seal all. I m an architect in wisconsin climate zone 6b and am planning to build a 300 s f. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards. In reality rigid foam board which sometimes comes in fanfold usually only has an insulating factor of r 1 and does not add any appreciable insulation effect to your home.

Most homes in the united states are built with traditional wood frame construction with studs every 16 on center. I d like to side it in fiber cement siding to match the existing house. So using 1 4 let in braces may not be an automatic solution when building foam sheathed walls metal bracing may not be the answer either. According to my calculations if i want to use rigid foam insulation on the outside of the 2x6 walls with r 21 fiberglass in the wall cavities i need at least r 11 25 in order to avoid condensation on the inside.

Under driven nails can telegraph through to the fi nished siding and trim. Building codes allow them as substitutes for 1 x4 let in braces. There are three primary types. Bottom line is exterior foam insulation is a good investment.

When using continuous insulation foam sheathing avoid over driving fasteners which can result in dimpling of the siding due to the compressible nature of the foam sheathing.