BASC Search | Building America Solution Center

Wrong – Roof underlayment is not fully adhered and roof deck seams are not sealed so roof is susceptible to high-wind events

Right – Roof underlayment is fully adhered and roof deck seams are sealed so roof is resistant to high-wind events

Right - The underside of the attic roof deck is insulated with open-cell spray foam to provide an insulated space for HVAC equipment.

Publication Date

Fri, 01/01/2010 - 12:00

There are three potential locations for an attic radiant barrier – adhered to the underside of the roof decking, hanging from the rafters, or on the ceiling insulation

Publication Date

Wed, 06/01/2005 - 12:00

Fully enclosing the area under the deck increases its resistance to wildfire by minimizing the space where embers can lodge.

Publication Date

Tue, 04/20/2021 - 12:00

Wrong – Conventional wood deck risks ignition from embers falling on the surface or from unmaintained vegetation burning below.

Publication Date

Sat, 12/01/2012 - 12:00

Baffles allow ventilation under roof decking while keeping wind from blowing insulation back from the edges of an attic.

Publication Date

Thu, 09/01/2011 - 12:00

IECC Climate Zone 1A: Unvented Attic with Spray foam at Roof Deck, 2x6 Wall-CMU Wall, Elevated Slab

Publication Date

Thu, 01/11/2024 - 12:00

Low-slope roof assemblies constructed of two deck sheathing layers sandwiching rigid foam, and topped with mechanically fastened membrane

IECC Climate Zone 2A: Unvented Attic with Spray Foam at Roof Deck, 2x6 Wall/CMU Wall, Elevated Slab

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 2A: Unvented Attic with Spray Foam at Roof Deck, 2x6 Wall/CMU Wall, Elevated Slab

Publication Date

Wed, 10/18/2023 - 12:00

A patio and wall constructed of noncombustible concrete, stone, or brick helps to deflect heat and protect the deck and house from approaching wildfires.

Publication Date

Tue, 04/20/2021 - 12:00

Detail of an unvented cathedralized attic showing air-impermeable spray foam insulation plus batt insulation installed on the underside of the roof deck.

2021 IECC Climate Zone 2A: Unvented Attic with Spray Foam at Roof Deck, 2x6 Wall-CMU Wall, Elevated Slab

Publication Date

Thu, 01/11/2024 - 12:00

Baffles provide an air space over the insulation to guide ventilation air from the soffit vents up along the underside of the roof deck

Publication Date

Thu, 06/28/2012 - 12:00

The attic is sealed and insulated along the underside of the roof deck with 5.5 inches of polyurethane spray foam, providing conditioned space for the HVAC system.

Continuous load path failure due to improper connections between the roof decking and roof framing resulting from hurricane force winds.

Reference

Coastal Construction Manual - Principles and Practices of Planning, Siting, Designing, Constructing, and Maintaining Residential Buildings in Coastal Areas, Fourth Edition, Volume II, FEMA P-55

Author(s)

Coulbourne William,

Jones Christopher P,

Kapur Omar,

Koumoudis Vasso,

Line Philip,

Low David K,

Overcash Glenn,

Passman Samantha,

Reeder Adam,

Seitz Laura,

Smith Thomas,

Tezak Scott

Organization(s)

Federal Emergency Management Agency,

FEMA,

Applied Technology Council,

ATC,

URS Group,

DK Low and Associates,

Atkins,

TLSmith Consulting

Volume II of a two-volume report providing a comprehensive approach to design, construction, and renovation of homes located in coastal environments.

Publication Date

Mon, 08/01/2011 - 12:00

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

Right – The roof membrane is fully adhered and deck seams are sealed so the membrane will not flutter and fail due to negative pressure from high winds

Right – Closed-cell polyurethane foam is sprayed on the underside of the roof deck to provide structural connections and seal seams in the sheathing to increase wind resistance

A roof drain is installed in an existing flat roof retrofitted with above-deck rigid foam insulation that is integrated with new air and water control layers

Publication Date

Thu, 09/10/2015 - 12:00

Standard Specification for Establishing Performance Ratings for Wood-Plastic Composite and Plastic Lumber Deck Boards, Stair Treads, Guards, and Handrails, ASTM D7032-21

Author(s)

ASTM International

Organization(s)

ASTM

Publication Date

December, 2021

ASTM standard for wood-composite decking and guardrail materials under a variety of tests, including fire performance and UV resistance. Available for preview and purchase at the reference link.

This builder applied an air-sealing layer of spray foam along the underside of the roof deck and the inside of the walls before filling the wall cavities with blown cellulose.

On top of the ice-and-water shield, the builder installed horizontal beams that were raised 6 inches off the deck to allow room for spray foam insulation.

Spray foam insulation is applied along the underside of the roof deck to provide a conditioned and non-vented attic space for ducts and air handlers.

Reference

40% Whole-House Energy Savings in the Hot-Humid Climate, Volume 15

Author(s)

Baechler Michael C,

Gilbride Theresa L,

Hefty Marye G,

Cole Pam C,

Adams Karen T,

Noonan Chrissy F,

Love Pat M

Organization(s)

Pacific Northwest National Laboratory,

PNNL,

Oak Ridge National Laboratory,

ORNL,

U.S. Department of Energy,

DOE

A guidebook helping builders in hot-humid climates design and construct homes for energy efficiency, durability, health, safety, and comfort.

Publication Date

Thu, 09/01/2011 - 12:00

Step and kick-out flashing at all roof-wall intersections extending ≥ 4 in. on wall surface above roof deck and integrated with drainage plane above

Publication Date

Tue, 02/01/2011 - 12:00

The mechanical curb for a skylight is integrated with the water management and air control layers on a flat roof retrofitted to include new above-deck rigid foam insulation

Publication Date

Fri, 05/01/2015 - 12:00

Wrong - Roof is missing metal drip edge to cover the edge of OSB roof decking, roof underlayment should be trimmed back, and asphalt shingles are poorly installed.

Publication Date

Mon, 09/28/2020 - 12:00

Unvented roof assembly at rake retrofitted with spray foam installed along the underside of the roof deck and extended to the rake edge to insulate and air seal the attic

Publication Date

Mon, 07/01/2013 - 12:00

Right - Metal drip edge on this south Florida CMU home protects the top of the fascia and edge of the roof deck from water, wind-blown rain and embers, and insects.

Publication Date

Tue, 06/01/2021 - 12:00

Unvented Attic with Spray foam at Roof Deck, 2x6 Wall-CMU Wall, Elevated Slab

1A

Unvented Attic with Spray Foam at Roof Deck, 2x6 Wall/CMU Wall, Elevated Slab

2A

The unvented attic is insulated along the underside of the roof deck with 7 inches (R-49) of closed-cell spray foam, providing vaulted ceilings and a conditioned knee wall space for ducting.

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

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.

Wrong – If roof membrane is not fully adhered, it can flutter and fail due to negative pressure from wind above and positive pressure from air leakage through roof deck below

Right - This new sealed attic has 5.5 inches (R-20) of spray foam insulation along the underside of the roof deck providing a conditioned attic space for the heating and cooling ducts.

Right – Metal flashing is installed between the deck boards and house wall with the top of the flashing extending up behind the siding and the bottom of the flashing extending out and down over the ledger board

Publication Date

Fri, 03/01/2019 - 12:00

This attic was insulated with 5 inches of closed-cell spray foam on the underside of the roof deck plus 6.5 inches of blown fiberglass covered with sheetrock as a firebreak for a total R-58 roof assembly insulation value.

The icicles and the bare spot along the left roof ridge indicate that heat from the second-story room may be heating the underside of the roof deck, melting the snow and likely leading to ice dam formation.

Publication Date

Mon, 10/30/2006 - 12:00

Right – Spray foam air seals and insulates the walls including the walls behind the fireplace and covers the underside of the roof deck of this mixed-dry climate home to provide an insulated attic space for HVAC ducts.

Publication Date

Thu, 09/30/2021 - 12:00

Heated or partially heated garages with podium decks should be thermally isolated from both ambient exterior space and interior conditioned space by insulating the interior of the garage walls and ceiling and extending the insulation below grade.

Publication Date

Tue, 09/17/2024 - 12:00

In 2009 IECC CZ 5 and higher, install self-sealing bituminous membrane or equivalent over sheathing at eaves from the edge of the roof line to > 2 ft. up roof deck from the interior plane of the exterior wall.

Publication Date

Tue, 02/01/2011 - 12:00

The OSB roof decking product comes with an adhered radiant foil barrier which helps to prevent heat transfer in or out of the vented attic, while R-13 unfaced fiberglass fills the advanced-framed 2x6 walls.

Retrofit an existing roof by installing rigid foam above the roof deck with a ventilation space between the rigid foam and the new roof sheathing plus new moisture and air control layers and cavity insulation in the roof rafters.

Right – Flex ducts are properly supported with straps that don’t pinch the insulation; closed-cell spray foam will be applied to the underside of the roof deck of this hot-humid climate home to provide an insulated attic space for the HVAC ducts.

Publication Date

Thu, 09/30/2021 - 12:00

Wrong – Tree branches close to the house are prone to spreading crown fires to the house; the tree should be trimmed so that branches are at least 10 feet back from the red dashed line indicating the deck railing of the house.

Publication Date

Fri, 01/22/2021 - 12:00

The simple gable roof is constructed at an unusual 6.55 pitch that allows exactly four and a half sheets of 4-foot- wide coated, taped roof sheathing to be installed as the roof deck with enough space at the peak for a continuous ridge vent.

ICF walls and an attic sealed and insulated to R-63 on the underside of the roof deck with 10 inches of open‐cell spray foam plus 2.7 inches of closed‐cell spray foam provide a complete thermal break around this home.

This roof was constructed to meet the IBHS Fortified Roof standard by sealing the decking seams with flashing tape, installing synthetic roof underlayment secured with metal drip edge and nailed every six inches, and using self-adhered starter shingles.

Publication Date

Thu, 08/17/2023 - 12:00

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.

Wrong – This roof membrane on a low slope roof is fluttering and may fail because it is not fully adhered and deck seams below are not sealed, allowing air to leak up into the assembly while the membrane is pulled up due to negative pressures from wind

This home survived the Laguna Beach fire of October 1993, which claimed more than 400 neighboring homes, thanks to a fire-resistant tile roof, stucco exterior, stucco-covered boxed eaves and under-decks, double-pane windows and selective landscaping

Publication Date

Fri, 12/08/2017 - 12:00

The 8-foot deck/overhang on the left provides better summer shading than the 2-foot extended-width overhang, which performs better than the 2-foot window-width overhang, which performs better than the 2-foot vertical fin (late summer, 36N latitude)

Publication Date

Tue, 07/25/2023 - 12:00

Unvented Insulated Sloped Roofs

Guide describing construction of sloped roofs that are unvented and are insulated above the roof deck.

Unvented Attic Insulation

Guide describing methods for insulating an unvented attic along the roof line.

Insulating Garages in Multifamily Buildings

Guide describing how to properly insulate garages in multifamily buildings.

Attic Air Sealing, Insulating, and Ventilating for Ice Dam Prevention

Information guide describing proper attic air-sealing, insulation, and ventilation to combat ice dam formation on roofs in cold climate zones.

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.

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.

Construct Roofs and Attics for Ice Dam Prevention

Guide describing how ice dams form and how roofs can be constructed to prevent them.

Condensation Control in Attics and Roofs in Cold Weather

Guide describing causes of condensation in attics and roof assemblies during cold weather and ways to reduce this condensation.

Roof Valleys and Penetrations Sealed

Guide describing how to seal roof valleys and how to seal around pipes, chimneys, and other roof deck penetrations.

Roof Eaves Sealed with Self-Adhering Membrane in Cold Climates

Guide describing how to apply heavy membranes at eaves in cold climates to help guard against ice dams.

Existing Skylights Repaired or Replaced and Fully Flashed

Guide describing how to repair or replace skylights in existing homes.

Vented versus Unvented Attic

Guide describing options for designing and locating the thermal boundary at either the attic floor or along the roof line in new and existing homes.

Hurricanes and High Winds Overview

Overview guide outlining home construction techniques used in hurricane and high wind areas.

Clay or Concrete Tile Roofs

Guide discussing disaster resistance related to clay or concrete tile roofing when installing roofing on new construction or when repairing or replacing roofing on existing homes.

Metal Roofs

Guide discussing disaster resistance related to metal roofing when installing roofing on new construction or when repairing or replacing roofing on existing homes.

FORTIFIED Roof System - Hurricane

Publication Date

December, 2014

Animated video showing how to properly apply roof decks in hurricane regions according to IBHS practices.

Inside FORTIFIED: Sealing Roof Seams with Tape

Publication Date

May, 2018

Video showing how to seal the roof deck with tape per IBHS Fortified Requirements.

Living With Fire in the Big Sagebrush/Bitterbrush Environment

Publication Date

November, 2015

Author(s)

UNRExtension

Organization(s)

UNRExtension

Video presentation from the University of Nevada - Reno showing how to prepare a home and attached structures such as decks, surrounded by sagebrush for wildfires through steps such as defensible space, land maintenance, and materials selection.

Framing of Gable Roof Overhangs

Guide describing construction of gable roof overhangs to resist uplift pressures in high winds.

Inside FORTIFIED: Fastening Sheathing on Existing Roofs in Hurricane Areas

Publication Date

May, 2018

Video showing how to correctly install sheathing on existing roof deck in hurricane regions in accordance with IBHS Fortified Home practices.

Air Sealing, Insulating, and Venting Attics and Roofs to Reduce Heat Gain

Information guide providing links to guides describing specific ways to air-seal, insulate, and ventilate attics and roofs to minimize heat gain in new and existing homes.

Floors: Above Unconditioned Basement, Vented Crawlspace, Cantilevered Floors, and Floors above Garage, Code Compliance Brief

New language in the 2015 IECC allows different installation of insulation in floors over unconditioned spaces.

Installing Chimney Flashing - Counterflashing Overlaps Base Flashing To Repel Water Along The Chimney/Roof Line

Author(s)

Litchfield Mike

Organization(s)

Fine Homebuilding Magazine

Publication Date

September, 2020

Article describing how to counterflash a chimney by tucking the upper pieces of counterflashing into the chimney mortar joints and overlapping them over the various pieces of base flashing, which are nailed to the roof deck.

Project Overcoat: Airtightness Strategies and Impacts for 1 1/2-Story Homes, Minneapolis, Minnesota

Author(s)

University of Minnesota

Organization(s)

NorthernSTAR,

NSTAR

Publication Date

November, 2014

Case study describing the External Thermal and Moisture Management System developed by the NorthernSTAR Building America Partnership for retrofitting roofs with rigid foam over the roof deck, especially on one and a half-story homes.

Roof Edge Protection

Guide describing designs and construction retrofits for roof assemblies to resist pressures at roof edges during high-wind events.

Radiant Barrier

In sunny climates, sun beating down on the roof can cause high attic temperatures and threaten the comfort of the adjoining rooms below. It can also cause air conditioning equipment to work harder, especially if the air conditioner or ducts are located in an uninsulated attic. A sun barrier...

Cost Analysis of Roof-Only Air Sealing and Insulation Strategies on 1-1/2 Story Homes in Cold Climates, Minneapolis, MN

Author(s)

University of Minnesota,

NorthernSTAR

Organization(s)

NSTAR,

UMN

Publication Date

December, 2014

This case study describes costs associated with the External Thermal and Moisture Management System developed by the NorthernSTAR Building America Partnership for retrofitting roofs with rigid foam over the roof deck, especially on one and a half-story homes.

FORTIFIED Home Selection & Installation of Metal Roof Panels - Metal Panel Roof Covering: Guidance on Selection, Installation and Documentation

Author(s)

Insurance Institute for Business and Home Safety

Organization(s)

IBHS

Publication Date

January, 2019

Checklist providing selection and installation guidance for residential, non-structural metal roof systems installed over wood roof decks with a roof slope 2:12 or greater to comply with section R905.1 of the 2015 IRC for a FORTIFIED Roof – New Roof Designation.

Inside FORTIFIED: Installing Underlayment Over Taped Seams

Publication Date

May, 2018

Video showing how to install synthetic underlayment over taped seams on roof deck per IBHS Fortified requirements.

Cost Analysis of Roof-Only Air Sealing and Insulation Strategies on 1 1/2-Story Homes in Cold Climates

Author(s)

Ojczyk Cindy

Organization(s)

University of Minnesota,

U.S. Department of Energy,

DOE,

NothernSTAR

Publication Date

December, 2014

Report exploring alternative methods to find long-term solutions to energy loss in 1 ½-story homes to save energy, improve comfort, prevent frost buildup on the underside of the roof deck, and reduce the risk of ice dam formation/reformation.

Roof/Attic to Exterior Wall Air Control Upgrade

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

Wildfire Resistant Home

Wildfire damage can be minimized by designing landscaping to include “defensible space,” using noncombustible materials to block embers from entering vulnerable areas such as soffits and under decks and porches, and choosing fire-resistant roofing materials and double-pane tempered glass windows. In...

Step and Kick-Out Flashing at Roof-Wall Intersections

Guide describing how to install step and kick-out flashing on roofs.

Heavy Membrane Valley/Eave

Valleys and penetrations through the roof decking are some of the areas of the roof most vulnerable to leaks. A peel-and-stick bituminous membrane is installed for protection at these critical locations, including all roof valleys, roof-to-wall transitions, and roof edges to minimize ice dam damage...

Hurricane Resistant Home

Hurricanes pose a serious threat along the Gulf and Atlantic coasts. Designers and builders can choose from a variety of features to help minimize losses from high winds and the impact of flying debris. Measures are available to fortify all typical construction types, including concrete, masonry...

Standard Specification for Elastomeric Joint Sealants, ASTM C920-18

Author(s)

American Society for Testing and Materials,

ASTM International

Organization(s)

ASTM

Publication Date

January, 2018

Standard specification covering the properties of a cured single- or multicomponent cold-applied elastomeric joint sealant for sealing, caulking, or glazing operations on buildings, plazas, and decks for vehicular or pedestrian use, and types of construction other than highway and airfield pavements...

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.

Severe Winter Storm Resist. Home

Power outages, freezing water pipes, and ice dams are among the risks that accompany severe winter weather. A thoroughly air sealed and insulated house can stay warm for hours or even days if the power goes out. Water pipes should be protected from freezing conditions by not locating them in...

Wind Resistant Home

Designers and builders can choose from a variety of features to help minimize losses from high winds. The choice of features will depend on the severity and type of local wind events, but the entire continental United States is exposed to high winds. This is especially true for tornado and hurricane...

Design for Wildfire Resistance

Information guide describing defensible space, fire-resistant materials, and other features to include when designing a home for wildfire resistance.

Asphalt Shingle Roofs

Guide discussing disaster resistance related to asphalt shingle roofing when installing roofing on new construction or when repairing or replacing roofing on existing homes.

Water Managed Roof Assembly

The roof is the home's primary defense against water intrusion from rain, snow, and ice. Water that seeps into the house through the roof can quickly ruin insulation, create conditions for mold growth and pest invasion, and even set into motion structural rot. Valleys and penetrations through the...

Tornado/Hail Resistant Home

Tornados pose a serious threat in the midsection and southern parts of the nation, but many other regions are also at risk. Designers and builders can choose from a variety of features to help minimize losses from high winds and the impact of flying debris. Measures are available to fortify all...

Retrofit of Existing Roofs for Hurricane, High Wind, and Seismic Resistance

Guide describing ways to retrofit an existing roof to increase its resistance to damage during hurricanes, high winds, and earthquakes.

Flashing of Roof-Wall Intersections in Existing Homes

Guide describing how to install and properly integrate flashing at the intersection of the wall and roof on an existing home.