BASC Search | Building America Solution Center

Wrong - Duct insulation and vapor barrier do not cover all of the flex duct.

Wrong - Duct insulation and vapor barrier do not cover all of the flex duct.

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This IR camera image shows an HVAC duct in the attic that may have displaced insulation.

This IR camera image shows an HVAC duct in the attic that may have displaced insulation.

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Wrong - Flex duct insulation is overly compressed in 3 ways; Zip-tie fastener is over the insualtion not under the insulation at the duct boot collar, duct turning radius is too tight, and support strap is too tight.

Wrong - Flex duct insulation is overly compressed in 3 ways; Zip-tie fastener is over the insualtion not under the insulation at the duct boot collar, duct turning radius is too tight, and support strap is too tight.

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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.

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.

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Wrong- A tie strap should not be used over the duct outer liner because it can compress the insulation. Tuck in the fibrous insulation and seal the outer liner to the connecting duct with mastic or foil tape (Steven Winter Associates 2013).

Wrong- A tie strap should not be used over the duct outer liner because it can compress the insulation. Tuck in the fibrous insulation and seal the outer liner to the connecting duct with mastic or foil tape (Steven Winter Associates 2013).

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Cavity used for return is not insulated and is not air sealed, which will pull in air from outside

Cavity used for return is not insulated and is not air sealed, which will pull in air from outside

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All other supply ducts and all return ducts in unconditioned space have insulation ≥ R-6

All other supply ducts and all return ducts in unconditioned space have insulation ≥ R-6

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The pipe insulation on this exterior refrigerant line is intact but significantly degraded from ultraviolet (UV) exposure.

The pipe insulation on this exterior refrigerant line is intact but significantly degraded from ultraviolet (UV) exposure.

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Right - Insulating sleeve for small through-the-wall HRV unit with sealing gasket; 3 of 14.

Right - Insulating sleeve for small through-the-wall HRV unit with sealing gasket; 3 of 14.

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A nylon draw band and tensioning tool are used to secure the inner coil of the pre-insulated flexible duct

A nylon draw band and tensioning tool are used to secure the inner coil of the pre-insulated flexible duct

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A nylon draw band and tensioning tool are used to secure the inner liner of the pre-insulated flexible duct

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Baffles are installed to protect airflow from the soffits to the ridge vents before the ceiling drywall and attic insulation are installed.

Baffles are installed to protect airflow from the soffits to the ridge vents before the ceiling drywall and attic insulation are installed.

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When wrapping metal ducts with insulation allow two inches of overlap and staple along the seam with outward clinching staples

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If HVAC duct must be installed in an exterior wall, separate it from the exterior with at least R-6 of continuous rigid insulation

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Right – Rigid foam is installed behind HVAC ducts to provide additional insulation to the ducts which are installed within the conditioned space.

Right – Rigid foam is installed behind HVAC ducts to provide additional insulation to the ducts which are installed within the conditioned space.

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

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

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A ducted central return brings air from central return registers back to the air handler through insulated, air-sealed ducts

A ducted central return brings air from central return registers back to the air handler through insulated, air-sealed ducts

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To attach the flex duct to a main trunk duct or any other connection, the flex duct is pulled over the connecting collar at least 2 inches past the raised bead, then the insulation is pulled back

To attach the flex duct to a main trunk duct or any other connection, the flex duct is pulled over the connecting collar at least 2 inches past the raised bead, then the insulation is pulled back

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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 – 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.

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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

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

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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

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

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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.

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.

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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.

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.

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Building Science Introduction - Heat Flow

Information Guide

Information guide describing the concept of heat flow in residential buildings.

Ducts in Raised Ceiling Sections

Guide

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

Encapsulated Ducts

Guide

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

HVAC Ducts Shall Not Be Run within Exterior Walls

Guide

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

Bedford Farmhouse High Performance Retrofit Prototype

Case Study

Case study describing a retrofit project in the cold and very-cold climate zones.

Home Performance Assessment

Information Guide

Information guide describing how to apply a whole-house approach to home improvement with energy efficiency upgrades, improved indoor air quality, and increased comfort.

High Performance Builder Spotlight: G.W. Robinson, Gainesville, FL

Case Study

Case study describing a new home construction project in the hot-humid climate.

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