Best Practices Manual

Continuous exterior insulation is like a winter sweater wrapping a building. It is also a key component in establishing a thermal bridge-free building envelope. Thermal bridges are penetrations in a building’s insulation layer, like the wood studs of a stud wall for example, that allow heat to escape and cold to intrude through the building envelope. In otherwise high performance assemblies, thermal bridges can be a source of tremendous energy loss and condensation risk.

By insulating around would-be thermal bridges, continuous exterior insulation establishes a thermal break between these building components and the exterior environment. As with insulation in general, as we introduce exterior insulation we need to understand and detail for the effects this insulation will have on moisture movement through the overall assembly.

Foil-Faced Polyisocyanurate (Polyiso)

• Exterior surface may be used as a WRB, with manufacturer approval.
• Install tape at seams per manufacturer specification.

1. Must use J-Roller on tape with good detailing to eliminate ‘Fish-Mouthing.’

Expanded Polystyrene (EPS)

• Multiple layers with staggered seams recommended to accomodate product shrinkage.
• While exterior surface may be used as a WRB, we do not recommend it.

1. Install tape at seams per manufacturer specification.
2. Must use J-Roller on tape with good detailing to eliminate ‘Fish-Mouthing.’

• For cutting, use knives and (for EPS and XPS) “hot wire” devices; minimize use of saws to limit dust for site cleanliness, carpenter health, and to prevent tool damage.
• If thicker than 2,” install in multiple layers with staggered seams to prevent thermal bypass.
• Fastening: consult manufacturer specifications or structural architectural drawings.

1. Install first layer of rigid insulation with limited number of nails or screws with washers.
2. Install second layer of rigid insulation with limited number of nails or screws with washers.
3. Fasten furring with screws; spacing and fastener size to be decided by weight of siding material and spacing of furring.

• WRB to be placed and fully integrated at wall structure.
• Exterior flashings should be installed to minimize thermal bridging (locate back dam on outer face of first layer of insulation).
• Minimize cutting of product; when needed use specific mineral wool knives.

Examples:
(Black) Fastenmaster Hedlock
(Silver) GRK