BASC Search | Building America Solution Center

Wrong – These flex ducts are pulled taut, which is correct but they are inadequately supported with straps that are spaced too far apart and are too tight causing pinching of the insulation and turns are sharp rather than gradual.

Wrong - Do not install a Class I vapor retarder over vapor-permeable insulation on the interior of a foundation wall because the vapor retarder can trap moisture in the wall, which can lead to mold.

Publication Date

Sun, 10/01/2006 - 12:00

Plan view (from above) showing how the existing garage wall gypsum board is cut away to air-seal the shared wall before adding rigid foam insulation on the garage and exterior walls of the home.

Publication Date

Mon, 07/01/2013 - 12:00

The builder in this very cold climate installed three layers of unfaced mineral wool batt in the double wall with a code-required vapor barrier between the middle and inner layers of wall insulation that is taped to barriers in the ceiling and floor.

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.

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

Brick veneer is supported by a concrete stem wall thermally separated from the slab-on-grade foundation with turn-down footing which is also insulated on top; anchorage for seismic resistance is also shown

Right - Permeable rigid mineral wool insulation and appropriate water-management flashing details are integrated with new rigid foam siding to keep water away from the sill beam above the foundation wall

A 5,000- 6,000 Btu/hr air conditioner drawing about 500 watts can be installed in one window of a designated cool room (it is important that the installation is insulated and well-sealed

The IR image on the right shows the sun is heating the southeast-facing wall of this concrete-block house to 36C (97F); this corner of the home would not be a good place for a cool room due to lack of shading and insulation

Publication Date

Mon, 11/14/2022 - 12:00

Right – the 2x6 walls are insulated with a flash-and-batt approach that includes spraying the wall cavities with one inch of open-cell foam to seal the sheathing to the framing then filling the wall cavities with R-19 fiberglass batts that are compressed

Publication Date

Fri, 12/31/2021 - 12:00

Plan view of exterior masonry brick wall retrofitted with furring strips, three layers of rigid foam insulation staggered and taped at the seams, and 1x4 furring strips to provide a nailing surface and ventilation gap under lap siding

Publication Date

Fri, 08/13/2021 - 12:00

This home’s exterior walls include Larsen trusses, 9-inch I-joists attached through exterior sheathing to wall studs creating a 9-inch wall cavity that was filled with blown insulation and forms extra deep windowsills.

Publication Date

Wed, 12/29/2021 - 12:00

Right – This home is framed with double walls – two 2x4 walls set next to each other then sheathed with OSB on the exterior and netted on the interior face to create an extra-deep wall cavity that can be filled with blown-in insulation.

Publication Date

Thu, 09/30/2021 - 12:00

Specially designed roof trusses come with a two-foot by two-foot notch cut next to the center post providing space to install an insulated duct chase inside the home’s conditioned space but above the normal ceiling height.

A paint-on waterproofing covers the exterior and tops of the concrete block foundation walls and piers to block moisture moving up through the concrete, while foil-faced R-13 insulation lines the inside surface of the exterior walls.

Publication Date

Fri, 01/01/2016 - 12:00

Right - Prevent condensation in fibrous insulation-filled basement wall cavities by installing rigid or spray foam between the frame wall and the concrete foundation wall and by not installing a Class I vapor retarder over the framed wall.

Horizontal furring strips are installed over a taped smart membrane that serves as an air and vapor barrier and holds in insulation; the furring strips will provide a nailing surface for tongue-and-groove wood porch ceiling cladding.

Publication Date

Fri, 12/31/2021 - 12:00

An ultra-efficient layer of R-20 rigid foam foundation insulation covers the ground underneath the vapor barrier and radiant floor loops, which will circulate water heated by an ultra-efficient geo heat pump.

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.

In this exterior wall retrofit of a masonry brick home, first the brick was covered with a fluid-applied water and air control layer (white), then 2x4 furring strips and two layers of rigid foam insulation, then 1x4 furring strips to attach cladding to

Publication Date

Fri, 08/13/2021 - 12:00

Thermally isolate heated garages in multifamily buildings from ambient space, and thermally isolate all garages in multifamily buildings from interior occupied space. This parking garage is thermally isolated from space above with spray foam insulation.

Publication Date

Tue, 09/17/2024 - 12:00

A simple vented attic with good air-sealing of the drywall ceiling air barrier, air flow from soffit vents to ridge vents protected by ventilation baffles, and lots of insulation covering the attic floor is unlikely to encourage ice dams.

Publication Date

Wed, 08/15/2012 - 12:00

Right – The raised slab foundation has a 3-ft stem wall of filled concrete block, then is back-filled with compacted dirt and crushed rock, then insulated with 1” rigid foam covered with taped vapor barrier, under a floor slab.

Publication Date

Mon, 09/30/2019 - 12:00

Right - Reduce condensation risks to blanket insulation by installing perforated vapor retarder covered fiberglass blankets over rigid foam that is air-sealed at all edges; staple the blanket to nailers and top/bottom plates and tape over the seams.

Publication Date

Fri, 01/01/2021 - 12:00

Right – This hot-humid climate home is constructed with concrete block that is insulated on the inside with rigid foam; the framing is borate-treated lumber; the roof design is a high-wind-resistant hip roof with only one small gable over the entry.

Publication Date

Thu, 09/30/2021 - 12:00

Right - A dimpled-plastic geotextile mat covers the below-grade insulated concrete form (ICF) foundation to help keep water out of the foundation and to reduce hydrostatic pressure on the foundation during freeze-thaw cycles in winter.

Publication Date

Fri, 12/31/2021 - 12:00

Green Coast Enterprises built this New Orleans home on piers so that the floor is 1 foot above the base flood level; borate treated framing and closed-cell spray foam insulation add to the home's moisture resistance.

Publication Date

Thu, 09/01/2011 - 12:00

Wrong - Plastic-covered blanket insulation that is installed directly against concrete walls with no rigid foam or closed-cell spray foam covering the concrete could trap moisture coming through the concrete, leading to mold, moisture, and odor problems.

Publication Date

Thu, 10/26/2006 - 12:00

Pest protection measures include a termite shield under the rim joist and extending out on either side of the stem wall, insect screening under the furring air gap, and brick veneer to protect slab-edge insulation.

Publication Date

Mon, 03/01/2021 - 12:00

Right – Insulated concrete form (ICF) blocks are stacked like bricks, then rebar is set horizontally and vertically in the plastic spacers, then concrete is poured; the rigid foam and spacers stay in place to add support and thermal resistance to the wall

Publication Date

Thu, 09/30/2021 - 12:00

Create a cool room to shelter from extreme heat by selecting a room in the basement or on the north or shaded side of the house, air sealing and insulating, providing low-wattage and battery-operated cooling, and reducing interior heat loads.

Publication Date

Mon, 11/14/2022 - 12:00

Plan view of exterior masonry brick wall retrofitted with furring strips, three layers of rigid mineral wool insulation staggered and taped at the seams, and topped with metal hat channel providing a ventilation gap surface to nail under the lap siding

Publication Date

Fri, 08/13/2021 - 12:00

Advanced framing techniques including 2x6 walls spaced at 24 inches on center and ladder blocking at wall intersections allow more space for insulation in the wall cavities while open-web floor joists provide space between floors for ducting.

Publication Date

Mon, 01/01/2018 - 12:00

This Habitat for Humanity builder ordered roof trusses with a 2-foot by 2-foot notch next to the center post then lined the cutout with rigid foam to form an insulated central duct chase to bring the heating and cooling ducts within the conditioned space.

Spray foam insulation extends down the foundation wall to the slab, which has been retrofitted by cutting the slab to install drainage mat against the wall and a new perimeter footing drain, along with rigid foam plastic above the slab.

Publication Date

Mon, 07/01/2013 - 12:00

HVAC ducts, cavities used as ducts, and combustion inlets and outlets may pass perpendicularly through exterior walls but shall not be run within exterior walls unless at least R-6 continuous insulation is provided on exterior side of the cavity

This raised-slab poured concrete foundation includes flood-resistant features such as a sloped grade, capillary break under the slab (gravel or sand), vapor retarder under the slab (rigid insulation), and capillary break at the top of the foundation wall

Publication Date

Sat, 01/01/2022 - 12:00

The mechanical room in the insulated basement houses the water heating equipment, including the storage tank for the solar thermal system and the wall-hung boiler as well as the air handler for the hydro coil and high-efficiency (16 SEER) air conditioner.

Right – The window header is filled with spray foam and sealant is used to air seal wood-to-wood seams; however, it would be preferable to design the wall to avoid so many stacked studs around the windows because they prevent wall insulation installation.

Publication Date

Fri, 12/31/2021 - 12:00

This close-up of an exterior wall retrofit of a masonry brick home shows the fluid-applied water and air control layer (white), 2x4 furring strips and two layers of rigid foam insulation (pink), then 1x4 furring which provides a ventilation gap

Publication Date

Fri, 08/13/2021 - 12:00

Capillary break beneath all slabs (e.g., slab on grade, basement slab) except crawlspace slabs using either: ≥ 6 mil polyethylene sheeting lapped 6-12 in., or ≥ 1 in. extruded polystyrene insulation with taped joints

Publication Date

Mon, 02/21/2011 - 12:00

Each floor of this two-story modular home is constructed in a factory, including the 2x6, 24-inch on-center walls, R-21 fiberglass batt cavity insulation, and rigid exterior foam, housewrap, windows, and trim, then connected on site.

An externally insulated slab-on-grade is pest-protected by a metal termite shield under sill plate, metal-flashing-wrapped foam under siding, a removable inspection strip of PVC-covered foam, and 2 feet of gravel next to the foundation.

Publication Date

Mon, 03/01/2021 - 12:00

Right - The precast insulated concrete walls of the basement provide a conditioned space for the high-efficiency (18 SEER, 9.5 HSPF) air-source heat pump, with its variable-speed fan, five-stage compressor, and MERV 11 filter.

This attic is insulated to R-64 with a hybrid application of 11 inches of open-cell spray foam (R-4.45/in) plus 2 inches of closed-cell spray foam (R-7.4/in) that completely fills the roof rafter cavities and encases the rafters.

This Texas homes uses a slab foundation including a 4-in.-thick post-tensioned monolithic slab with turned-down edges poured over a 6-mil polyethylene vapor barrier and capillary break; slab edge insulation is not used due to termite risk.

Publication Date

Thu, 09/01/2011 - 12:00

The highly efficient double wall system consists of two sets of stud walls set side by side to create a 12-inch-thick double-stud wall cavity that is filled with a continuous blanket of R-44 dense-packed cellulose insulation.

The exterior walls are double walls consisting of two 2x4 stud walls set 3 inches apart to form a 10-inch-thick wall cavity that is filled with blown-in fiberglass to provide a continuous R-40 blanket of insulation around the home.

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.

Skylight Shaft Walls

Guide describing insulation techniques for skylight shaft walls.

Karuna Passive House High-Density Cellulose

Publication Date

October, 2012

Video describing the high-density cellulose insulation installed in a passive house.

Floor Above Garage

Guide describing how to create an air barrier between the garage and the conditioned space above it to prohibit pollutants from entering a home's interior.

Walls Adjoining Porch Roof

This guide describes how to install a rigid air barrier to separate the porch attic from the conditioned space.

Double Wall Framing - Code Compliance Brief

Double stud wall wood framing is not specifically addressed in the International Residential Code (IRC) or International Energy Conservation Code (IECC); it is neither encouraged nor discouraged. Recommendations of where the vapor retarder and air barrier should be placed, based on research and testing are further defined in this Code Compliance Brief.

ROXUL Mineral Wool | Madrona Passive House

Publication Date

February, 2015

Video describing the installation of mineral wool monolithic exterior insulation.

Building Science Introduction - Heat Flow

Information guide providing background information about heat flow in residential buildings.

Roof/Attic to Exterior Wall Air Control Upgrade

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

Floor Above Unconditioned Basement or Vented Crawlspace

Guide describing how to air-seal and insulate the floor above an unconditioned basement or crawl space.

Double-Wall Architectural Feature

Guide describing air barrier installation, insulation installation, and air-sealing for double walls (half or full walls included in a home design as an architectural feature that provides a more dimensional appearance).

Attic Knee Walls

Guide describing how to insulate and air-seal attic knee walls and floor joist cavities under knee walls.

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.

Fold-Form

Author(s)

Owens Corning Insulation

Organization(s)

Owens Corning Insulation

Publication Date

August, 2006

Information sheet with manufacturer specifications about insulated concrete forms.

Walls Behind Showers and Tubs (1)

Publication Date

July, 2015

Video describing how to properly insulate walls behind showers and tubs.

Attic Knee Walls

Publication Date

July, 2015

Video describing how to insulate and air seal attic knee walls.

Walls Behind Showers and Tubs (3)

Publication Date

July, 2015

Video describing how to properly insulate walls behind showers and tubs.

High-Performance Window System

Homes with high-performance window systems are more comfortable and consume less energy than homes with traditional windows. High-efficiency ENERGY STAR-rated windows perform at least 15% better than a standard window and have an insulating value of R-3 or higher. Ultra-efficient windows perform at...

Continuous Air Barrier in Exterior Walls

Guide describing how to install continuous air barriers in exterior walls.

Monolithic slab with a grade beam

Publication Date

Fri, 05/01/2009 - 12:00

Slab independent of foundation wall

Publication Date

Fri, 05/01/2009 - 12:00

Easy access

Publication Date

Tue, 05/01/2012 - 12:00

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.

Wind Washing

Guide describing wind washing and how to prevent it.

Termite-Resistant Foundations and Walls

Guide describing techniques and measures for increasing the termite resistance of a home's foundations.

Building Materials with High Moisture Content Not Enclosed

Guide describing how to avoid using wet materials and reduce moisture exposure in construction.

Designing with SIPs: Design Considerations

Author(s)

Structural Insulated Panel Association

Organization(s)

SIPA

Publication Date

July, 2020

Guide informing architects and engineers about designing buildings to be constructed with structural insulated panels.

Encapsulated Ducts

Publication Date

July, 2015

Video describing air sealing and insulation for encapsulated ducts.

Building with SIPs: Need to Know

Author(s)

Structural Insulated Panel Association

Organization(s)

SIPA

Publication Date

July, 2020

Guide informing builders and developers about efficient building practice for constructing homes with structural insulated panels.

Dropped Ceiling/Soffit Below Unconditioned Attic

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

Crawlspaces – Either In or Out, BSI-115

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

March, 2020

Article discussing whether or not to seal and insulate crawlspaces.

Vinyl Siding with Integrated Rigid Foam for Existing Walls

Guide describing the design and installation considerations for recladding of above grade walls using insulated vinyl siding.

ICF bricks are stacked to form hollow walls that are reinforced with steel rebar before the concrete is poured in

Publication Date

Mon, 10/01/2012 - 12:00

Proper flashing around windows is especially important when the rigid foam serves as the drainage plane in the wall

Publication Date

Mon, 10/01/2007 - 12:00

Passive House Wall Assembly Mock | Hammer & Hand

Publication Date

March, 2015

Video showing a mock wall assembly used in Hammer and Hand’s passive houses.

Construct Roofs and Attics for Ice Dam Prevention

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

Air Sealing Attic Access Panels/Doors/Stairs

Guide describing how to air-seal attic access panels, doors, and stairs to provide a continuous air barrier at the ceiling.

Connection of roof truss to wall panel

DWG

PDF

High Performance Builder Spotlight: Scott Homes Inc.

Author(s)

Pacific Northwest National Laboratory

Organization(s)

PNNL

Publication Date

January, 2011

Case study describing a new home construction project in the marine climate.

Connection of two SIP wall panels at a corner

DWG

PDF

Connection of two SIP roof panels with beveled edges at roof ridge

DWG

PDF

Connection of a SIP roof panel to a beveled SIP wall panel

DWG

PDF

SIP roof panel detailing at eaves with an angled fascia

DWG

PDF

High-Performance Homes - A Simpler Design Strategy

Author(s)

Tom Patton

Organization(s)

Fox Blocks,

EEBA

Publication Date

August, 2020

Webinar from Tom Patton of Fox Blocks on how changes to building codes are driving changes to framing assemblies and insulation, highlighting how ICFs can take over for traditional wood frame wall assemblies. Free EEBA login required.

Westford House, BSI-018

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC

Publication Date

March, 2009

Report describing sloped roof assemblies with high levels of thermal performance.

Advanced Framing vs Traditional Framing

Publication Date

December, 2012

Author(s)

Risinger

Organization(s)

Build with Matt Risinger

Video describing traditional 2x4 16 inch on center framing versus advanced framing with 2x6 stud walls at 24 inch on center, insulated corners and headers, wall stud-ceiling joist alignment, etc. providing a strong wall with more room for insulation.

Increase Seismic Resistance and Thermal Performance of Basement, Crawl Space, and Crawl Space with Cripple Wall Foundations

Guide describing different options for providing seismic and thermal resistance for homes with basement foundations, crawlspace foundations, or crawlspace foundations with a "cripple" wall.

Cantilevered Floor

Guide describing how to air-seal and insulate a cantilevered floor.

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...

Staircase Walls

Guide describing how to create a fully aligned air barrier behind a staircase.

Ducts in Raised Ceiling Sections

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