Scope
When HVAC ducts are installed in a vented attic in any climate, encapsulate the HVAC ducts in attic insulation to protect them from temperature extremes in the unconditioned attic space.
- Install ductwork so that it is in direct contact with (i.e., laying on) the ceiling and/or truss lower cords.
- Use metal, flex, or fiber board ducts that are insulated to code. The duct insulation should include a vapor barrier cover.
- Mechanically fasten and mastic-seal all duct connections.
- Test total duct leakage. Add additional sealant if necessary.
- Completely encase the ducts in closed-cell spray polyurethane foam (ccSPF) to the desired foam depth.
- Install loose-fill insulation to cover the ducts and the attic floor to meet or exceed the code-required R value for attic insulation.
- This technique fulfills the DOE Zero Energy Ready Home program requirement that ducts be installed in conditioned space.
See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Single-Family New Homes, and Indoor airPLUS.
Description
For homes with ducted heating and cooling systems, the best place to locate the duct system from an HVAC performance standpoint is within the conditioned space of the home, either in dropped ceilings, or between floors, or in a sealed and insulated basement, crawlspace, or attic. If the ducts must be located within a vented attic, one option for protecting the ducts and helping to minimize heat transfer between ducts and the unconditioned attic is to lay the ducts on the attic floor and cover them with the same blown insulation that is used to cover the attic floor.
If using this technique in the humid or marine climates, the ducts must be encapsulated with spray foam before installing the blown insulation. Use a compact duct layout. The ductwork should be installed so that it is in direct contact with the ceiling and/or truss lower cords. Metal, flex, or fiber board ducts can be used. The ducts should be covered with R-8 or higher duct insulation and the duct insulation should include a vapor barrier cover. All duct connections should be mechanically fastened and mastic-sealed. The ducts should be tested for total duct leakage and any leaks should be sealed. Once these preparations are made, the ducts can be encapsulated in closed-cell polyurethane spray foam then buried in loose-fill insulation (typically blown fiberglass or cellulose) at the same time that the attic floor is being insulated. The insulation levels should meet or exceed the code-required R value for attic insulation. Figure 1 shows a duct that is encapsulated in spray foam and then partially, fully, or deeply buried in blown attic insulation.
The effective R-value of a buried and encapsulated duct installation depends on the size of the ducts, the insulation value of the duct insulation, the thickness of the ccSPF insulation, and the depth of the loose-fill insulation. The effective R-values of 8-inch round ducts encapsulated with 1.5 inches of ccSPF are shown in Table 1 for three insulation depths and three common duct insulation levels (R-4.2, R-6, and R-8).
Typically, the duct design will consist of one or more main supply trunk(s) and perpendicular duct branches serving each of the ceiling registers. If the trunk is perpendicular to the truss bottom chords, then the duct branches can be parallel and rest directly on the ceiling drywall. If the main truck is placed parallel to the ceiling supports, then the branches will need to run perpendicular to and rest on top of the truss chords. Either configuration will work, giving the designer the flexibility to select whichever method works best for a particular circumstance. In every case, a compact, low-profile duct layout should be designed.
The ccSPF may be installed before or after the ceiling gypsum board is installed. If the gypsum board is installed before the ducts are encapsulated, special care must be taken to fully encapsulate the ducts. The ccSPF may be installed to fully encapsulate and surround the duct. Or, the ducts may be laid on a piece of rigid foam board substrate, or laid directly on the ceiling drywall; in these cases, the spray foam in installed to encase the top and sides of the duct and to connect to the rigid foam or ceiling under the duct as shown in Figure 2.
How to Install Buried and Encapsulated Ducts after the Ceiling Is in Place
- Install ceiling gypsum board prior to installing buried ducts (Figure 3).
Figure 3. Ceiling gypsum board, HVAC ducts, and other services have been installed but not attic insulation. (Source: Steven Winter Associates.) - Install ductwork across lower truss cords or rafters or resting on the ceiling drywall. Install insulated ducts that have a minimum of R-8 duct insulation and an integral vapor barrier. Install the ductwork in accordance with a low-profile compact duct design (Figure 4).
Figure 4. This duct is laid directly on the ceiling drywall. (Source: Steven Winter Associates.) - Properly fasten and seal ducts at all connections. To attach flex duct, pull back the outer liner, fasten the inner liner over the collar with a tool-tightened tension tie, and mastic seal the connection. Pull insulation and outer liner over the joint and seal to the attached duct or boot with mastic or foil tape (Figure 5). The outer liner should not be attached with a tie as shown here but should be connected with mastic or foil tape to avoid compressing the insulation as shown in Figure 7.
Figure 5. The inner liner of the flex duct is fastened to the collar with a tension tie, the connection is sealed with mastic, then the outer layer is pulled over and sealed with mastic or foil tape. (Source: Steven Winter Associates.) - Test total duct leakage with a duct blaster to ensure that the ducts have been adequately sealed (total duct leakage < 3 cfm25 per 100 ft2 of conditioned space) (Figure 6). Testing should be performed before encapsulation because it may be difficult to correct sealing issues after the application of spray foam.
Figure 6. A duct blaster is used to test total duct leakage. (Source: Steven Winter Associates.) - Air-seal the ceiling plane penetrations, including sealing the duct register boots to the gypsum board ceiling using canned spray foam (Figure 7).
Figure 7. Duct boots and other ceiling penetrations are air-sealed using spray foam. (Source: Steven Winter Associates.) - Apply at least 1.5 in of ccSPF to all duct surfaces, including trunks, branches, and register boots. Where obstructions make the bottom of the duct inaccessible (such as when a wide trunk is placed on top of and perpendicular to the ceiling framing), the duct may be placed on 1.5-inch-thick XPS or polyisocyanurate insulation board. Ducts should be entirely encapsulated and sealed to the gypsum board or to the rigid insulation board with spray foam (Figure 8).
Figure 8. Completely encapsulate all surfaces of the ducts, trunks, branches, and register boots with > 1.5 inches of ccSPF. (Source: Steven Winter Associates.) - Install loose-fill insulation to the specified depth, and verify that the ducts are covered to the level desired (Figure 9). Fiberglass or other mineral fiber insulation must cover the ccSPF by at least 1.5 inches unless the foam is rated for exposure in attics or a separate ignition barrier is applied.
Figure 9. Loose-fill attic insulation is installed to the specified depth. (Source: Steven Winter Associates.)
How to Install Buried Ducts before Ceiling Is in Place
- Install ductwork across lower truss cords or rafters. Install insulated ducts that have a minimum of R-8 duct insulation and an integral vapor barrier. Install the ductwork in accordance with a low-profile compact duct design. Where ducts are running parallel to ceiling framing, provide temporary blocking to hang ducts approximately 2 inches above the ceiling plane to allow for the thickness of the spray foam. (Figure 8).
Figure 10. These ducts were installed before the ceiling drywall was installed. Ducts are supported by temporary strapping across the lower truss cords. (Source: Steven Winter Associates.) - Connect, seal, and test ducts as described above in Steps 3 and 4.
- Encapsulate ducts in spray foam as described above in Step 6.
- Install ceiling gypsum board after installing ducts.
- Air seal ceiling plane and and install attic floor insulation as described in Steps 5 and 7 above. Fiberglass or other mineral fiber insulation must cover the ccSPF by at least 1.5 inches unless the foam is rated for exposure in attics or a separate ignition barrier is applied.
Success
If buried and encapsulated ducts are to be used, duct design should be considered during the design stage in conjunction with framing design, so that the duct layout can be as compact as possible, with short, straight runs and a low profile, so that ducts lay on or as close to the ceiling as possible. Other best-practice measures include right-sizing the HVAC and using inboard registers which will result in is less ductwork to bury.
Return trunks and branches could be treated in the same manner; however, to keep the HVAC distribution system at a minimum, while simultaneously providing good comfort and proper airflow, the use of central returns is recommended. Return air paths from bedrooms and other spaces can be accommodated by low-profile jump ducts or other means.
To eliminate condensation concerns in moist or marine climates, ccSPF must be applied to all surfaces of the ductwork, or the ducts must be sealed to the ceiling gypsum board with ccSPF. All duct connections should be mastic sealed and ducts should be tested for leakage with a duct blaster before the ccSPF is applied.
Special attention is needed to ensure code compliance for buried & encapsulated ducts because they include spray foam insulation applied to ductwork. The 2009 IRC allows exposed installations of ccSPF in attics, but the spray foam must be specifically approved for installation without an ignition barrier. If the spray foam used is not specifically approved for exposed attic installations, at least 1.5 inch of mineral fiber insulation, such as loose-fill fiberglass or mineral wool, must cover the spray foam.
Climate
Buried and encapsulated ducts may be installed in all climate zones, including moist (A) and marine (C) climate zones. The ccSPF insulation mitigates condensation concerns in these climates.
The map in Figure 1 shows the climate zones for states that have adopted energy codes equivalent to the International Energy Conservation Code (IECC) 2009, 12, 15, and 18. The map in Figure 2 shows the climate zones for states that have adopted energy codes equivalent to the IECC 2021. Climate zone-specific requirements specified in the IECC are shown in the Compliance Tab of this guide.
Training
Compliance
Compliance
The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.
ENERGY STAR Single-Family New Homes, Version 3/3.1 (Rev. 11)
National Rater Field Checklist
HVAC System.
6. Duct Quality Installation - Applies to Heating, Cooling, Ventilation, Exhaust, & Pressure Balancing Ducts, Unless Noted in Footnote.
6.3 All supply and return ducts in unconditioned space, including connections to trunk ducts, are insulated to ≥ R-6.38
6.4 Rater-measured total duct leakage meets one of the following two options. Alternative in Footnote 40:39, 40, 41
6.4.1 Rough-in: The greater of ≤ 4 CFM25 per 100 sq. ft. of CFA or ≤ 40 CFM25, with air handler & all ducts, building cavities used as ducts, & duct boots installed. All duct boots sealed to finished surface, Rater-verified at final.42
6.4.2 Final: The greater of ≤ 8 CFM25 per 100 sq. ft. of CFA or ≤ 80 CFM25, with the air handler & all ducts, building cavities used as ducts, duct boots, & register grilles atop the finished surface (e.g., drywall, floor) installed.43
6.5 Rater-measured duct leakage to outdoors the greater of ≤ 4 CFM25 per 100 sq. ft. of CFA or ≤ 40 CFM25.39, 44
Footnote 38) Item 6.3 does not apply to ducts that are a part of local mechanical exhaust and exhaust-only dwelling unit mechanical ventilation systems. EPA recommends, but does not require, that all metal ductwork not encompassed by Section 6 (e.g., exhaust ducts, duct boots, ducts in conditioned space) also be insulated and that insulation be sealed to duct boots to prevent condensation.
Footnote 39) Items 6.4 and 6.5 generally apply to the ducts of space heating, space cooling, and dwelling unit mechanical ventilation systems. However, visual inspection is permitted in lieu of testing for a dwelling unit mechanical ventilation system not connected to the space heating or space cooling system, regardless of the number of dwelling units it serves. In such cases, a Rater shall visually verify that all seams and connections are sealed with mastic or metal tape and all duct boots are sealed to floor, wall, or ceiling using caulk, foam, or mastic tape. For duct systems requiring testing, duct leakage shall be determined and documented by a Rater using ANSI / RESNET / ICC Std. 380 including all Addenda and Normative Appendices, with new versions and Addenda implemented according to the schedule defined by the HCO that the home is being certified under. Leakage limits shall be assessed on a per-system, rather than per-home, basis.
Footnote 40) For a duct system with three or more returns, the total Rater-measured duct leakage is permitted to be the greater of ≤ 6 CFM25 per 100 sq. ft. of CFA or ≤ 60 CFM25 at ‘rough-in’ or the greater of ≤ 12 CFM25 per 100 sq. ft. of CFA or ≤ 120 CFM25 at ‘final’.
Footnote 41) Note that compliance with Item 6.4.1 or 6.4.2 in conjunction with Section 4a of the National Rater Design Review Checklist automatically achieves Grade I total duct leakage per ANSI / RESNET / ACCA Std. 310.
Footnote 42) Cabinets (e.g., kitchen, bath, multimedia) or ducts that connect duct boots to toe-kick registers are not required to be in place during the ‘rough-in’ test.
Footnote 43) Registers atop carpets are permitted to be removed and the face of the duct boot temporarily sealed during testing. In such cases, the Rater shall visually verify that the boot has been durably sealed to the subfloor (e.g., using duct mastic or caulk) to prevent leakage during normal operation.
Footnote 44) Testing of duct leakage to the outdoors can be waived in accordance with the 2nd or 3rd alternative of ANSI / RESNET / ICC Std. 301, Table 4.2.2 (1), footnote (w). Alternatively, testing of duct leakage to outdoors can be waived in accordance with Section 5.5.2 of ANSI / RESNET / ICC Std. 380 if total duct leakage, at rough-in or final, is ≤ 4 CFM25 per 100 sq. ft. of conditioned floor area or 40 CFM25, whichever is larger. Guidance to assist partners with these alternatives, including modeling inputs, is available at http://www.energystar.gov/newhomesguidance.
Please see the ENERGY STAR Single-Family New Homes Implementation Timeline for the program version and revision currently applicable in your state.
DOE Zero Energy Ready Home (Revision 07)
Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
Exhibit 1, Item 3) Duct distribution systems located within the home’s thermal and air barrier boundary or an optimized location to achieve comparable performance.
Footnote 14) Exceptions and alternative compliance paths to locating 100% of forced-air ducts in home’s thermal and air barrier boundary are:
- Up to 10’ of total duct length is permitted to be outside of the home’s thermal and air barrier boundary.
- Ducts are located in an unvented attic, regardless of whether this space is conditioned with a supply register.
- Ducts are located in a vented attic with all of the following characteristics: [Note that in either of these designs the HVAC equipment must still be located within the home’s thermal and air barrier boundary.]
- In Moist climates (Zones 1A, 2A, 3A, 4A, 5A, 6A and 7A per 2015 IECC Figure R301.1) and Marine climates (all “C” Zones per 2015 IECC Figure R301.1), minimum R-8 duct insulation with an additional minimum 1.5” of closed-cell spray foam insulation encapsulating the ducts; duct leakage to outdoors ≤ 3 CFM25 per 100 ft2 of conditioned floor area (in addition to meeting total duct leakage requirements from Section 4.1 of the ENERGY STAR HVAC Rater checklist); and ductwork buried under at least 2” of blown-in insulation.
- In Dry climates (all “B” Zones per 2015 IECC Figure R301.1), minimum R-8 duct insulation; duct leakage to outdoors ≤ 3 CFM25 per 100 ft2 of conditioned floor area (in addition to meeting total duct leakage requirements from Section 4.1 of the ENERGY STAR HVAC Rater checklist); and ductwork buried under at least 3.5” of blown-in insulation.
- Systems which meet the criteria for “Ducts Located in Conditioned Space” as defined by the 2018 IECC Section R403.3.7
- Jump ducts which do not directly deliver conditioned air from the HVAC unit may be located in attics if all joints, including boot-to-drywall, are fully air sealed with mastic or foam, and the jump duct is fully buried under the attic insulation.
- Ducts are located within an unvented crawl space.
- Ducts are located in a basement which is within the home’s thermal boundary.
- Ductless HVAC system is used.
2009 International Energy Conservation Code (IECC) / 2009 International Residential Code (IRC)
IECC R403.2/IRC N1103.2 Ducts.
IECC R403.2.1/IRC N1103.2.1 Insulation (Prescriptive). Supply ducts in attics shall be insulated to a minimum of R-8. All other ducts shall be insulated to a minimum of R-6.
Exception: Ducts or portions thereof located completely inside the building thermal envelope.
IECC R403.2.2/IRC N1103.2.2 Sealing (Mandatory). All ducts, air handlers, filter boxes, and building cavities used as ducts shall be sealed. Joints and seams shall comply with Section M1601.4 of the International Residential Code. [Exceptions may apply.]
Duct tightness shall be verified by either of the following:
- Post-construction test: leakage to outdoors shall be less than or equal to 8 cfm (226.5 L/min) per 100 ft2 (9.29 m2) of conditioned floor area or a total leakage less than or equal to 12 cfm (339.8 L/min) per 100 ft2 of conditioned floor area when tested at a pressure differential of 0.1 inches w.g. (25 Pa) across the entire system, including the manufacturer’s air handler enclosure. All register boots shall be taped or otherwise sealed during the test.
- Rough-in test: Total leakage shall be less than or equal to 6 cfm (169.9 L/min) per 100 ft2 of conditioned floor area when tested at a pressure differential of 0.1 inches w.g. (25 Pa) across the roughed in system, including the manufacturer’s air handler enclosure. All register boots shall be taped or otherwise sealed during the test. If the air handler is not installed at the time of the test, total leakage shall be less than or equal to 4 cfm (113.3 L/min) per 100 ft2 of conditioned floor area.
Exceptions: Duct tightness test is not required if the air handler and all ducts are located within conditioned space.
IECC R403.2.3/IRC N1103.2.3 Building cavities (Mandatory). Building framing cavities shall not be used as supply ducts.
IECC R403.2/IRC N1103.2 Ducts. Ducts and air handlers shall be in accordance with IECC R403.2.1 through R403.2.3 (IRC N1103.2.1-N1103.2.3).
IECC R403.2.1/IRC N1103.2.1 Insulation (Prescriptive). Same as 2009 IECC/IRC.
IECC R403.2.2/IRC N1103.2.1 Sealing (Mandatory). Ducts, air handlers, and filter boxes shall be sealed. Joints and seams shall comply with either the International Mechanical Code or International Residential Code, as applicable [Exceptions may apply.]
Exceptions:
1. Air-impermeable spray foam products shall be permitted to be applied without additional joint seals.
2. Where a duct connection is made that is partially inaccessible, three screws or rivets shall be equally spaced on the exposed portion of the joint so as to prevent a hinge effect.
3. Continuously welded and locking-type longitudinal joints and seams in ducts operating at static pressures less than 2 inches of water column (500 PA) pressure classification shall not require additional closure systems.
Duct tightness shall be verified by either of the following:
- Post-construction test: Total leakage shall be less than or equal to 4 cfm (113.3 L/min) per 100 ft2 (9.29 m2) of conditioned floor area when tested at a pressure differential of 0.1 inches w.g. (25 Pa) across the entire system, including the manufacturer’s air handler enclosure. All register boots shall be taped or otherwise sealed during the test.
- Rough-in test. Total leakage shall be less than or equal to 4 cfm per (113.3 L/min) per 100 ft2 (9.29 m2) of conditioned floor area when tested at a pressure differential of 0.1 inches w.g. (25 Pa) across the system, including the manufacturer’s air handler enclosure. All registers shall be taped or otherwise sealed during the test. If the air handler is not installed at the time of the test, total leakage shall be less than or equal to 3 cfm (85 L/min) per 100 ft2 of conditioned floor area.
Exception: The total leakage test is not required for ducts and air handlers located entirely within the building thermal envelope.
IECC R403.2.2.1/IRC N1103.2.2.1 Sealed air handler. Air handler shall have a manufacturer’s designation for an air leakage of no more than 2 percent of the design air flow rate when tested in accordance with ASHRAE 193.
IECC R403.2.3/IRC N1103.2.3 Building cavities (Mandatory). Building framing cavities shall not be used as ducts or plenums.
2015, 2018, and 2021 IECC / 2015, 2018, and 2021 IRC
IECC R403.3/IRC N1103.3 Ducts. Ducts and air handlers shall be in accordance with the entirety of section R403.3 (IRC N1103).
IECC R403.3.1/IRC N1103.3.1 Insulation (Prescriptive). Supply and return ducts in attics shall be insulated to a minimum of R-8 where 3 inches (76 millimeters) in diameter and greater and R-6 where less than 3 inches (76 millimeters) in diameter. Supply and return ducts in other portions of the building shall be insulated to a minimum of R-6 where 3 inches (76 millimeters) in diameter or greater and R-4.2 (R-6 in 2021 IRC) where less than 3 inches (76 millimeters) in diameter.
Exception: Ducts or portions thereof located completely inside the building thermal envelope.
IECC R403.3.2/IRC N1103.3.2 Sealing (Mandatory). Ducts, air handlers, and filter boxes shall be sealed. Joints and seams shall comply with either the International Mechanical Code or International Residential Code, as applicable.
Exceptions [In 2015 IECC/IRC only; these exceptions were not included in the 2018 IECC/IRC.)
- Air-impermeable spray foam products shall be permitted to be applied without additional joint seals.
- For ducts having a static pressure classification of less than 2 inches of water column (500 Pa), additional closure systems shall not be required for continuously welded joints and seams, and locking-type joints and seams of other than the snap-lock and button-lock types.
IECC R403.3.2.1/IRC N1103.3.2.1 Sealed Air Handler. Air handlers shall have a manufacturer’s designation for an air leakage of no more than 2% of the design air flow rate when tested in accordance with ASHRAE 193.
IECC R403.3.3/IRC N1103.3.3 Duct testing (mandatory). Ducts shall be pressure tested to determine air leakage by one of the following methods:
- Rough-in test. Total leakage shall be measured with a pressure differential of 0.1 inch water gage (25 Pa) across the system, including the manufacturer’s air handler enclosure if installed at the time of the test. All registers shall be taped or otherwise sealed during the test.
- Post-construction test. Total leakage shall be measured with a pressure differential of 0.1 inch water gage (25 Pa) across the entire system, including the manufacturer’s air handler enclosure. Registers shall be taped or otherwise sealed during the test.
Exception:
A duct air leakage test shall not be required where the ducts and air handlers are located entirely within the building thermal envelope.
[New Exception added to 2018 IECC/IRC] A duct air leakage test shall not be required for ducts serving heat or energy recovery ventilators that are not integrated with ducts serving heating or cooling systems.
A written report of the results of the test shall be signed by the party conducting the test and provided to the code official. [Because the ducts will be installed outside the building thermal envelope, this exception would not apply.]
IECC R403.3.4/IRC N1103.3.4 Duct leakage (Prescriptive).
The total leakage of the ducts, where measured in accordance with Section R403, shall be as follows:
- Rough-in test. The total leakage shall be less than or equal to 4 cfm per (113.3 L/min) per 100 ft2 (9.29 m2) of conditioned floor area where the air handler is installed at the time of the test. Where the air handler is not installed at the time of the test, the total leakage shall be less than or equal to 3 cfm (85 L/min) per 100 ft2 of conditioned floor area.
- Post-construction test: Total leakage shall be less than or equal to 4 cfm (113.3 L/min) per 100 ft2 (9.29 m2) of conditioned floor area.
[In 2021 IECC and IRC, a third test for ducts located entirely within the building thermal envelope is introduced. Where all air ducts and air handlers are located entirely within the building thermal envelope, the total leakage shall be less than or equal to 8 cfm per (226.6 L/min) per 100 ft2 (9.29 m2) of conditioned floor area.]
IECC R403.3.5/IRC N1103.3.5 Building cavities (Mandatory). Building framing cavities shall not be used as ducts or plenums.
2009, 2012, 2015, 2018, and 2021 IRC
Ducts are designed, constructed, and installed in accordance with the provisions of IRC M1601 and M1602, ACCA Manual D, and manufacturers’ guidance.
Retrofit: 2009, 2012, 2015, 2018, and 2021 IECC
Section R101.4.3 (in 2009 and 2012). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)
Chapter 5 (in 2015, 2018, 2020). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.
Retrofit: 2009, 2012, 2015, 2018, and 2021 IRC
Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)
Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.
Retrofit
SCOPE
In existing homes with vented attics and HVAC ducts that are installed on the attic floor, encase ducts in closed-cell spray polyurethane foam and cover with blown attic insulation.
- Before adding spray foam, remove any existing insulation that is covering the ducts. Note old insulation may contain asbestos.
- Inspect and test the ducts for missing or torn duct insulation; sagging, crushed. or excess flex duct; disconnected or leaking ducts.
- Repair and air seal ducts as needed before installing spray foam insulation.
- See the following for more information about insulating and air sealing metal, flex, or fiber board ducts.
- Flex duct runs should be pulled taut to reduce internal airflow friction. See the following guides to remedy installation problems prior to sealing or adding insulation to an existing flex duct system:
For more information, view the U.S. Department of Energy’s Standard Work Specifications regarding ducts.
Also see the Solution Center guide Pre-Retrofit Site Assessment of Attics, Ceilings and Roofs.
DESCRIPTION
Make any needed repairs as described above then follow installation guidance for new homes in the Description tab.
COMPLIANCE
See Compliance tab.
More
More Info.
Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.
The following authors and organizations contributed to the content in this Guide.
Steven Winter Associates, lead for the Consortium for Advanced Residential Buildings (CARB), a DOE Building America Research Team
Sales
Vented Attics with Buried HVAC Ducts =
Comfort systems installed in vented attics work much better when they are buried in insulation. Vented attics can reach extreme temperatures. Deeply burying the ducts in the attic's insulation provides significant protection from these harsh conditions. The ducts need to be tightly sealed to ensure optimum performance.
Sales Message