BASC Search | Building America Solution Center

Seal all drywall-to-top plate seams and penetrations at the attic floor

Publication Date

Mon, 02/01/2010 - 12:00

Air-seal the attic kneewall door opening with weatherstripping.

Publication Date

Thu, 01/01/2009 - 12:00

Technology Solutions Case Study: Complete and Fully Aligned Air Barrier

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

August, 2012

Case study describing the elimination of excessive humidity in the attic of a multi-floor, single-family home that was causing condensation and water damage along the roof and eaves.

De-Icing Ice Dams, BSI-097

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

October, 2018

Article describing the importance of air sealing, insulation, and roof ventilation in reducing the likelihood of ice dam formation on roofs in cold snowy climates.

Technology Solutions Case Study: Field Testing an Unvented Roof with Asphalt Shingles in a Cold Climate

Author(s)

Building Science Corporation

Organization(s)

BSC

Publication Date

September, 2015

Case study describing an experiment to build and instrument unvented test roofs using air-permeable insulation in a cold climate and to analyze the moisture effects over time.

How to Prevent Roof Damage from Winter Ice Buildup

Author(s)

Dorsi Chris

Organization(s)

Montana State University Extension,

MSU Extension

Publication Date

January, 2019

Article from Montana State University Extension explaining how proper insulation techniques can greatly reduce the risks of ice dams 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.

DOE ZERH HIA 2017 Case Study: Thrive Home Builders, Courtyard Rows, Lone Tree, CO

Author(s)

Pacific Northwest National Laboratory,

U.S. Department of Energy

Organization(s)

PNNL,

DOE

Publication Date

September, 2017

Case study describing a DOE Zero Energy Ready Home 2017 Housing Innovation Award winner that scored HERS 41 without PV and 8 with PV.

Air Sealing Bathroom and Kitchen Exhaust Fans

Guide describing how to air-seal bathroom and kitchen exhaust fans.

Thin-profile attic eave baffle and vent

DWG

PDF

Raised ceiling duct chase installation technique

Stuff cavities under kneewalls with rolls of fiberglass batt and spray foam in place

The seams in the ceiling drywall are sealed from the attic side with spray foam.

Right - R-100 of blown cellulose covers the floor and rafters of this attic.

Right – Open-cell spray foam fills the attic floor joists.

Publication Date

Mon, 09/30/2019 - 12:00

Wrong: Duct is hung between truss members by strapping and not buried

Right: Side-entry boots are used to keep ductwork close to the ceiling

Right: ductwork is fully encapsulated with ccSPF prior to ceiling installation and burial

Right – Spray foam fills the roof joist cavities of this vaulted, unvented attic.

Publication Date

Thu, 09/30/2021 - 12:00

Air seal floor joist cavities under kneewall with rigid foam, plywood, or OSB caulked in place

Publication Date

Thu, 02/16/2012 - 12:00

Form a sheet metal shield around the flue pipe

Pre-Retrofit Assessment of Attics, Ceilings, and Roofs

Information guide describing things to consider in the attic, ceiling, or roof before attempting retrofits of items including HVAC, wiring, or structural systems.

Duct boots and other ceiling penetrations are air-sealed using spray foam

Publication Date

Wed, 09/29/2021 - 12:00

Form sheet metal shield around pipe keeping 3-inch clearance

New Whole-House Solutions Case Study: Tommy Williams Homes: Longleaf Village & Belmont, Gainesville, FL

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

April, 2012

Case study describing a production builder that achieves HERS scores of 60, compared to 85 for other builders that build new homes to Florida code.

Install wood framing cross pieces in the attic rafter bays on each side of the duct chase

IECC Climate Zone 1A: Unvented Attic, 2x6 Wall, Monolithic Slab

Publication Date

Fri, 09/29/2023 - 12:00

IECC Climate Zone 2A: Unvented Attic, 2x6 Wall, Monolithic Slab

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 2A: Unvented Attic, 2x6 Wall, Pier Foundation

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 2B: Vented Attic, Block Wall, Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 2B: Unvented Attic, CMU Wall, Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

Install wood framing cross pieces in the attic rafter bays on each side of the duct chase

Wrong: Ducts are not laid across the lower truss cords or ceiling, but are hung from the rafters by straps. As a result, ductwork is not buried

Wrong: Ducts are held from the rafters with strapping and a large beam prevents ducts from properly lying on the ceiling plane

Southern Energy Homes worked with DOE researchers to develop an efficient way to dense-pack blown fiberglass into the low attics of manufactured homes.

IECC Climate Zone 3A: Unvented Attic, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 2A: Unvented Attic, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 2B: Unvented Attic, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 3A: Vented Attic, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 3B: Unvented Attic, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 3B: Vented Attic, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 1A: Flat Roof, Unvented, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Fri, 09/29/2023 - 12:00

IECC Climate Zone 2A: Flat Roof, Unvented, 2x6 Wall, Monolithic Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 3A: Vented Cathedral Celling, 2x6 Wall, Vented Crawl Space

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 3A: SIP Roof, SIP Wall, Stem Wall, Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 3B: SIP Roof, SIP Wall, Stem Wall, Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

IECC Climate Zone 4A: SIP Roof, SIP Wall, Stem Wall, Slab on Grade

Publication Date

Wed, 10/18/2023 - 12:00

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

An IR camera image shows gaps around HVAC flue pipes allow conditioned air to leak through blown fiberglass into the attic

Publication Date

Tue, 12/17/2013 - 12:00

Right - Open-cell polyurethane spray foam to R-28 on underside of roof turns new attic into conditioned space for HVAC.

Dropped Ceiling/Soffit Below Unconditioned Attic

Publication Date

July, 2015

Video describing how to air-seal soffits below attics.

Right - The energy recovery ventilator ducts supply filtered outside air to multiple locations in the home and continuously exhaust stale air to provide clean, balanced ventilation.

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

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

Right – Open-cell spray foam is installed over closed-cell spray foam in this hybrid approach to achieve adequate attic ventilation while allowing some vapor permeability.

Publication Date

Mon, 09/30/2019 - 12:00

How to Keep Attic Vent From Freezing Up in Winter

Publication Date

December, 2017

Author(s)

Tinsley

Organization(s)

Cold Climate Housing Research Center,

CCHRC

Video describing techniques to prevent attic plumbing vents from freezing during Alaskan winters.

The thermal boundary for a gable roof can be located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic

New Whole-House Solutions Case Study: Imagine Homes: Stillwater Ranch, San Antonio, TX

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

April, 2012

Case study describing a new home builder that strives to address health, safety, and durability issues in a hot and humid climate.

New Whole-House Solutions Case Study: Insight Homes: Deep Creek, Seaford, Delaware

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

April, 2012

Case study describing a home builder that has refined its home designs to achieve HERS scores of 49 to 56 on 40 to 70 homes per year.

DOE ZERH HIA 2013 Case Study: Preferred Builders, Old Greenwich, Connecticut

Author(s)

Pacific Northwest National Laboratory,

U.S. Department of Energy

Organization(s)

PNNL,

DOE

Publication Date

April, 2013

Case study describing a DOE Zero Energy Ready Home 2013 Housing Innovation Award Winner in Old Greenwich CT, that scored HERS 42 without PV and HERS 20 with PV.

Right: Ductwork is installed in direct contact with lower truss cords. In this picture the main trunk is laying on the truss cords and branch ducts are temporarily held with strapping across truss cords. Ducts are well sealed with mastic

A low-sloped shed roof with the thermal boundary located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic

Right – R-23 of blown fiberglass fills the walls and unvented vaulted attic cavities of this marine-climate home while an additional R-20 (4-inches) of graphite-enhanced expanded polystyrene is installed above the roof sheathing.

Publication Date

Thu, 09/30/2021 - 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.

No Sweat, BSI-094

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

April, 2016

Guide providing information on controlling attic ductwork sweating.

Ice Dams, BSD-135

Author(s)

Straube John

Organization(s)

Building Science Corporation,

BSC

Publication Date

October, 2006

Article outlining the casuses and solutions for ice dam problems.

Kick the Can! No Recessed Lights in the Building Envelope

Author(s)

Bailes Allison

Organization(s)

Energy Vanguard

Publication Date

April, 2011

Article discussing the downside to recessed can lights.

Zeroing In, BSI-081

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

October, 2014

Report describing Net Zero house design with sloped roof assemblies.

Pumpkin Ridge Passive House Video #010: Attic Truss Details

Publication Date

January, 2013

Video describing the attic truss details in a passive house.

A 1- and ½-story home with a room located in the attic and the thermal boundary located at either a) the walls and ceiling of the attic room with small vented attic spaces or b) the roof line for an unvented attic

This kneewall has no top plate and the resulting gap provides a wide-open pathway for air and vapor to travel between the living space and the attic

Wrong – No top plate was installed.

Publication Date

Fri, 10/28/2011 - 12:00

Venting Vapor, BSI-088

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

July, 2015

Guide providing information on controlling attic ductwork sweating.

Vulnerability of Vents to Wind-Blown Embers

Author(s)

Quarles Stephen L

Organization(s)

Insurance Institute for Business & Home Safety,

IBHS

Publication Date

August, 2017

Report covering the migration of wind-blown embers in roof vents.

Pumpkin Ridge Passive House Video #012: Interior Attic Air Barrier

Publication Date

January, 2013

Video describing the interior attic air barrier details in a passive house.

Wrong – There is no weather stripping or gasket around the attic stair hatch

Publication Date

Fri, 10/28/2011 - 12:00

Wrong – No rigid backing was installed on the attic knee wall.

Publication Date

Fri, 10/28/2011 - 12:00

Ping Pong Water and The Chemical Engineer, BSI-016

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

October, 2016

Article outlining moisture accumulation in open cell spray polyurethane foam.

Building Cavities Not Used as Supply or Return Ducts

Guide describing the use of building cavities as supply or return ducts.

Air seal attic access panels and drop-down stairs to minimize air leakage.

Publication Date

Fri, 10/28/2011 - 12:00

Cool Hand Luke Meets Attics, BSI-077

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

July, 2015

Article describing the difference between conditioned or unvented attics and unconditioned or vented attics.

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.

Measure Guideline: Buried and/or Encapsulated Ducts

Author(s)

Mantha Pallavi,

Zoeller William,

Shapiro Carl

Organization(s)

U.S. Department of Energy,

DOE

Publication Date

August, 2013

Project discussing buried or encapsulated ducts and their pros and cons.

Right - Blocking has been installed between the ceiling joists and air sealed in place with canned spray foam to stop air flow beneath the attic knee wall.

Publication Date

Fri, 01/01/2010 - 12:00

Cold Climate Building Techniques and Concepts: Cathedral Roofs

Publication Date

January, 2014

Author(s)

Cold Climate Housing Research Center

Organization(s)

CCHRC

Video describing roof and attic construction for cold climates, including cathedral roof design and insulation strategies, from Cold Climate Housing Research Center.

Pumpkin Ridge Passive House Video #13: Completed Wall-to-Attic Air Barrier Details

Publication Date

February, 2013

Video describing the wall-to-attic air barrier details of a passive house.

Right - Continuous wall sheathing and blocking has been installed to brace the raised heel trusses.

Publication Date

Sat, 10/01/2011 - 12:00

Right – Attic access door has foam and rubber weatherstripping installed that remains in contact when closed.

Publication Date

Fri, 10/28/2011 - 12:00

Existing Whole-House Solutions Case Study: Retrofitting a 1960s Split-Level Cold-Climate Home

Author(s)

Steven Winter Associates

Organization(s)

CARB,

SWA

Publication Date

September, 2015

Case study describing the retrofit of a 1960s split-level home.

Design Options for Locating Ducts within Conditioned Space

Author(s)

Zoeller

Organization(s)

Steven Winter Associates

Presentation with technical training covering several possible approaches to locating ducts within the home’s air and thermal barriers, and then dig into design considerations and details for the spray foam encapsulation approach.

Attic Air Sealing Guide and Details, GM-1001

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

February, 2010

Document providing background and approach for the prep work necessary prior to adding attic insulation - focusing on combustion safety, ventilation for indoor air quality, and attic ventilation for durability.

Field Testing Unvented Roofs with Asphalt Shingles in Cold and Hot-Humid Climates

Author(s)

Ueno Kohta,

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC,

U.S. Department of Energy,

DOE

Publication Date

September, 2015

Report to understand the long-term moisture performance of unvented roof assemblies with fibrous insulation.

Radiant Barrier: Effect of Radiant Barriers on Heating and Cooling Bills

Author(s)

Oak Ridge National Laboratory

Organization(s)

ORNL

Publication Date

September, 2022

Fact sheet describing analysis of potential heating and cooling savings from radiant barriers in attics.

Measure Guideline: Guide to Attic Air Sealing

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation

Publication Date

September, 2014

Guideline describing information and specifications relevant to air-seal existing attics.

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

Vented roof assembly at eave retrofitted with rigid foam, spray foam, and fully adhered membrane to air seal the top of wall-to-roof transition

Publication Date

Mon, 07/01/2013 - 12:00