BASC Search | Building America Solution Center

Duct insulated with a minimum of R-8 insulation

Publication Date

Thu, 08/01/2013 - 12:00

Ducts Buried in Attic Insulation

Guide describing buried ducts in loose-fill attic insulation, a method that can only be used in dry climates.

Ducts Buried in Attic Insulation and Encapsulated

Guide describing approaches to burying and encapsulating ducts in unconditioned attics to increase the overall R-value of duct insulation.

Ducts Encapsulated in Spray Foam and Buried in Attic Insulation

Publication Date

September, 2015

Video describing various ways to bring HVAC ducts installed in an attic within the thermal envelope of the home by insulating the attic or by covering the ducts with spray foam and burying them in fibrous insulation.

Wrong: Ductwork is not fully encapsulated with ccSPF insulation. The duct jacket is still fully visible at sections of the duct

Spray foam insulation used for raised ceiling duct chase

Spray foam insulation used for raised ceiling duct chase.

The attic duct chase insulated and sealed to the attic floor with spray foam

Right: Ducts are completely buried beneath insulation to the depth specified in the plans

Wrong: Ducts are held above the ceiling plane with strapping to provide a good angle into top-entry boots. Once the ceiling insulation is added, this duct will protrude from the ceiling insulation and will not be buried

Standard 2 in. by 4 in. stud secures duct chase - made of rigid insulation in this example

Buried Ducts within Ceiling Insulation of Vented Attics in all Climate Zones - Code Compliance Brief

Publication Date

January, 2020

The intent of this brief is to provide code-related information about buried ducts in vented attics to help ensure that the measure will be accepted as being in compliance with the code. Providing notes for code officials on how to plan review and conduct field inspections can help provide jurisdictional officials with information for acceptance. Providing the same information to all builders, designers, and others is expected to result in increased compliance and fewer innovations being questioned at the time of plan review and/or field inspection.

Buried ducts are laid on the floor of a vented attic then covered with spray foam and blown attic floor insulation

Publication Date

Wed, 09/01/2021 - 12:00

Right - Spray foam insulation has been sprayed onto the underside of the sloped roof and the gable end wall to provide a sealed, insulated attic for housing the HVAC ducts

Right – Spray foam insulation is sprayed on the underside of the roof deck to provide a conditioned space in this low attic for the HVAC ducts.

Publication Date

Fri, 12/31/2021 - 12:00

The spray foam-insulated attic provides a temperate place for the ERV ducts, which provide filtered fresh air to every room in the house.

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

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

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.

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.

A floor cavity between the first and second floor can provide a conditioned space for HVAC ducts if the rim joists are insulated and air sealed, if sufficient space is available, and if open-web floor joists are used

Publication Date

Wed, 01/01/2014 - 12:00

Encapsulated Ducts

Publication Date

July, 2015

Video describing air sealing and insulation for encapsulated ducts.

Encapsulated Ducts

Guide that illustrates how and when to encapsulate ductwork in unconditioned attics, increases the R-value of duct insulation, mitigating condensation issues and reducing air leakage.

Diagram of buried ducts

Publication Date

Thu, 08/01/2013 - 12:00

Support at Intervals for Flex Ducts

Guide describing how to hang ducts with supporting straps or saddles to adequately support ducts so they do not sag and are not pinched or compressed in a manner that would cause damage to the ducts, the duct insulation, or the duct air barrier covering.

Ducts in Raised Ceiling Sections

Guide describing method for designing and installing ducts in a raised ceiling chase.

Ducts in Dropped Ceilings

Guide describing method for installing ducts in a duct chase above a dropped ceiling.

Burried and encapsulated ducts in a ceiling plane

Publication Date

Fri, 02/01/2013 - 12:00

Air Sealing Duct and Flue Shafts

Guide describing how to air-seal duct and flue shafts.

Encapsulated ducts are sprayed with ccSPF in an unconditioned attic

Publication Date

Thu, 08/01/2013 - 12:00

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

Building Cavities Not Used as Supply or Return Ducts

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

Compact Buried Ducts in a Hot-Humid Climate House

Author(s)

Mallay David

Organization(s)

Home Innovation Research Labs,

HIRL

Publication Date

January, 2016

Report on heating and cooling air-distribution ducts that are insulated, installed close to the ceiling in a vented attic and covered with attic insulation to minimize energy loss.

Raised ceiling duct chase installation technique

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.

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.

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

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

Publication Date

Wed, 09/29/2021 - 12:00

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

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

Unvented Attic Insulation

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

Moisture Performance of Unvented Attics with Vapor Diffusion Ports and Buried Ducts in Hot, Humid Climates

Author(s)

Kaufman Zoe,

Fontanini Anthony,

Withers Charles R,

Marden Craig,

Ueno Kohta,

Philip Ross,

Barker Greg M,

Hancock Ed,

Earle Lieko,

Garber-Slaght Robbin,

Meleika Sam

Organization(s)

National Renewable Energy Laboratory,

NREL,

U.S. Department of Energy,

DOE

Publication Date

September, 2024

Report on the use of vapor diffusion ports to reduce moisture issues with buried ductwork in unvented attics in hot-humid climates.

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

Second layer of rigid insulation is adhered with foam

Blown Insulation for Existing Vented Attic

Guide describing how to insulate a vented attic in an existing home using blown insulation added to the attic floor.

Why Are Attics Insulated With Open-Cell Spray Foam So Damp?

Author(s)

Holladay

Organization(s)

Green Building Advisor

Presentation describing issues with condensation in unvented attics insulated with open-cell spray foam.

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.

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- This flue pipe has been air sealed with sheet metal and fire-rated caulk and an insulation dam has been constructed to keep insulation from touching the hot flue pipe

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.

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.

Spray Foam Insulation Applied to Existing Attic Floor

Guide describing how to apply spray foam insulation to ceilings in existing homes.

Attic Eave Minimum Insulation

Guide providing guidance on insulating attic eaves in new and existing single-family homes and multifamily buildings.

Wrong: open wall cavity connected to this return air plenum is allowing cellulose attic insulation to be pulled into the furnace

Publication Date

Sun, 06/01/2014 - 12:00

Below Deck Spray Foam Insulation for Existing Roofs

Guide describing how to add spray foam insulation to the underside of the existing roof deck as part of the conversion of a vented attic to an unvented, insulated attic.

Sealing and Insulating Existing Vented Attics - Code Compliance Brief

Publication Date

May, 2016

The intent of this brief is to provide code-related information about sealing and insulating existing vented attics to help ensure that the measure will be accepted as being in compliance with the code. Providing the same information to all interested parties (e.g., code officials, builders, contractors, designers, etc.) is expected to result in increased compliance and fewer innovations being questioned at the time of plan review and/or field inspection.

Air Sealing and Insulating Ceilings in Vented Attics

Guide describing how to air-seal and insulate a ceiling where the insulation is installed on top of the ceiling (on the attic floor) in a vented attic.

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.

Ceiling gypsum board has been installed

Publication Date

Thu, 08/01/2013 - 12:00

Air Sealing Bathroom and Kitchen Exhaust Fans

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

Builders Challenge High Performance Builder Spotlight: David Weekley Homes, Houston, Texas

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

December, 2009

Case study describing new home construction in the hot-humid climate, optimizing thermal enclosure, HVAC, water heating and lighting measures.

Sealed Attics?

Author(s)

Coble Brian

Organization(s)

Home Energy Magazine

Publication Date

January, 2010

Article describing how insulating and air sealing unfinished attic spaces can lead to reduced energy bills in some homes.

Air Seal HVAC Cabinet Seams

Guide describing air-sealing of the seams and holes in HVAC air handler and furnace cabinets.

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

Form a sheet metal shield around the flue pipe

Form sheet metal shield around pipe keeping 3-inch clearance

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

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.

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.

Existing Whole-House Solutions Case Study: Deep Energy Retrofit in the Pacific Northwest

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

December, 2011

Case study describing a whole-house, deep energy retrofit project in the marine climate.

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.

New Whole-House Solutions Case Study: Tom Walsh & Co., New Columbia, Portland, OR

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

February, 2013

Case study describing a new construction building project of 20 homes that earned HERS scores that represent greater than 50% energy savings in heating and cooling over the 2004 IECC.

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.

Dropped Ceiling/Soffit Below Unconditioned Attic

Guide describing how to insulate and air-seal dropped ceilings and soffits to prevent air leakage.

Whole House Ventilation Strategies for Existing Homes

Guide describing how to select and install whole-house ventilation systems for existing homes.

Wind Washing

Guide describing wind washing and how to prevent it.

Controlling Moisture in Unvented Attics - Code Compliance Brief

Publication Date

May, 2017

The intent of this brief is to provide code-related information about controlling moisture in unvented attics by installing a vapor diffusion port/vent that would convey water vapor from an unvented attic to the outside when air-permeable insulation materials are installed and can be verified as being in compliance with the related codes and standards for residential construction. Providing consistent information to document compliance with codes and standards to all relevant parties responsible for verifying compliance (e.g., code officials, builders, contractors, designers, etc.) is expected to result in increased compliance and more timely, less challenging and more uniform plan review and field inspections.