BASC Search | Building America Solution Center

Batt Insulation for Existing Vented Attics

Guide describing how to increase insulation in existing homes by installing batt insulation on the ceiling plane of a vented attic.

Right – Battens are installed above the cork insulation to provide a ventilating layer between the insulation and the roof sheathing and cladding.

Schematic of exterior insulated roof assembly

Right – Battens were installed above the cork insulation to provide a ventilating layer between the insulation and the roof sheathing on this “hot roof” design.

Publication Date

Mon, 09/30/2019 - 12:00

Above Deck Rigid Foam Insulation for Existing Roofs

Guide describing the installation of insulating sheathing above the roof deck on existing homes. This retrofit assembly is appropriate for homes with conditioned attics or where the retrofit is intended to create a conditioned attic.

To reduce the risk of condensation on the interior of the roof sheathing in cold weather, the ratio of exterior (above-deck) insulation must be increased as a percent of total attic insulation as outside temperature decreases

Publication Date

Sat, 10/01/2011 - 12:00

Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck

Guide describing a method for insulating an unvented attic by spraying foam insulation along the underside of the roof deck.

Water Managed Roof – Re-roofing and Adding Insulation Over a Sloped Roof

Guide describing how to re-roof an existing home with a sloped and add insulation above the roof deck.

Water Managed Roof – Re-roofing and Adding Insulation over a Flat Roof

Guide describing an approach to re-roofing an existing flat roof to improve thermal, water, and air control performance.

Right - These roof insulation panels are installed in multiple layers with joints offset both vertically and horizontally. The plywood nail base fastened to the roof framing holds the insulation layers together snuggly thus minimizing gaps

Sloped roof with cavity spray foam insulation, strapping, and gypsum board thermal barrier

Publication Date

Fri, 05/01/2015 - 12:00

Sheathing is removed from a flat roof to retrofit with air sealing, insulation, and water control layers

Polyisocyanurate rigid foam insulation is installed in multiple layers with staggered, taped seams over the flat roof

Right - Raised-heel trusses increase the roof height above the eaves allowing more space for insulation above exterior wall top plates; exterior wall sheathing extends up to keep wind from soffit vents from disrupting insulation.

Flat roof with cavity spray foam plus loose-fill insulation and gypsum board thermal barrier.

Publication Date

Fri, 05/01/2015 - 12:00

Right-Wall-insulating sheathing is extended up to roof rafters and sealed around the framing with spray foam

Technology Solutions Case Study: BA-1312: Application of Spray Foam Insulation Under Plywood and OSB Roof Sheathing

Author(s)

Building Science Corporation

Organization(s)

BSC

Publication Date

November, 2013

Case study describing research about spray foam roof insulation and moisture management.

Sloped roof with cavity spray foam insulation sprayed on underside of roof deck and covered with sprayed-on thermal or ignition barrier coating.

Publication Date

Fri, 05/01/2015 - 12:00

The wood blocking for future PV panel installation extends above the surface of the top layer of polyisocyanurate rigid foam insulation installed as part of a flat roof retrofit

Retrofit an existing roof by installing rigid foam, new moisture and air control layers, new sheathing, and new cladding plus cavity insulation in the roof rafters to create an unvented attic

Publication Date

Mon, 07/01/2013 - 12:00

This roof is hurricane proofed with a coated insulated OSB deck sheathing that is caulked and taped at all seams with a water-resistant tape, then fully covered with a peel-and-stick membrane, and asphalt shingles.

Roof/Attic to Exterior Wall Air Control Upgrade

Guide outlining how to retrofit an exterior wall and/or attic to provide continuous air sealing.

Attic Radiant Barriers

Guide describing application of a radiant barrier layer in the attic to block radiant heat transfer between hot surfaces and heat-absorbing surfaces.

The retrofitted flat roof has PV panels and walking mats installed over the roofing membrane

Closed-cell spray foam fills the roof joist cavities forming an air barrier between the masonry parapet wall and the roof sheathing

Closed-cell foam is sprayed into roof cavities along the masonry parapet wall to form a continuous air barrier between the wall and the sheathing of the flat roof

The builder installed 1.5 inches of soy-based spray foam on the outside of the walls over the OSB sheathing, then kept a ¾ inch gap between the foam and the brick veneer siding to allow moisture vapor from the bricks to dissipate.

The existing 2x8 roof rafters were topped with OSB; two layers of 2-inch rigid foam; plywood; ice and water shield at rakes, eaves, and valleys; underlayment; and fiberglass shingles, plus 6 inches of open-cell foam under the decking.

Low-Slope ("Flat") Roofs

A guide describing how to install low-sloped ("flat") roofs with insulation above the roof deck that resist wind pressures during high-wind events.

Typical Concrete Tile Roofs in Florida

Building in Extreme Cold, BSI-031

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

February, 2010

Article describing the control layers (air, thermal, and vapor barriers) needed to build homes successfully in very cold locations.

Unvented roof assembly at eave retrofitted with rigid foam, spray foam, and taped top edge of existing house wrap or building paper

Publication Date

Mon, 07/01/2013 - 12:00

Unvented roof assembly at rake retrofitted with a filler piece and taped top edge of existing house wrap or building paper to seal the top of wall-to-roof transition

Publication Date

Mon, 07/01/2013 - 12:00

Moisture Control for Residential Buildings

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC,

U.S. Department of Energy,

DOE

Publication Date

September, 2020

Report providing extensive guidance on controlling moisture in building envelopes through proper selection and installation on air, water, thermal, and vapor barriers.

Roof Deck Sheathing and Sealing for Sloped Roofs

Guide describing requirements for sheathing and sealing the roof decking in accordance with the requirements of the IBHS Fortified Home Program's Hurricane and High Wind Standards, and other roofing considerations to increase the roof's disaster resistance.