Unvented Roof Insulation

Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation.

Unvented roof insulation.

Low slope and steep slope unvented roof systems i e. Designs and houses with unvented roof insulation systems have also been developed and constructed in cold and mixed climates. Over the past five years several unvented roof insulation systems have been developed by the building science consortium for use primarily in hot dry and hot humid climate zones. Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense.

However architects of these compact roof assemblies must consider vapor permeance and arrangement of the materials to produce acceptable hygrothermal performance and low risk of condensation in the resulting conditioned attic space. In the most recent issue of fine homebuilding martin holladay wrote a piece on insulating unvented roof assemblies. But in it unfortunately all four options provided are dominated by foam. Insulation and air barrier are applied directly to the underside of the roof deck are common in applications where designers are seeking cost effective and energy efficient roof assemblies.

Four options for building an unvented roof assembly. This piece originally the quest for greater energy efficiency in buildings has led to increasing interest and need for insulation improvements in hvac equipment more airtight construction new materials and assemblies.