The location of all supply and return registers shall be verified by inspection of the interior of the dwelling unit. The location of the space conditioning equipment and the size, R-value, and location of each duct segment shall be verified by observation in the spaces where they are located. Deviations from the approved Duct Design Layout shall not be allowed without a revised a Duct Design Layout approved by the enforcement agency.
A visual inspection shall confirm space conditioning systems with air handlers located outside the conditioned space have 12 linear feet or less of duct located outside the conditioned space including air handler and plenum. If the space conditioning system has more than 12 feet of duct outside of conditioned space, the system does not pass.
A visual inspection shall confirm space conditioning systems are located entirely in conditioned space. If any part of the space conditioning duct system is outside of conditioned space, the system does not pass.
Compliance with Verified Duct System Design procedures specified in RA3.1.4.1.1 are prerequisite for compliance with the Supply Duct Surface Area Reduction compliance credit. A visual inspection shall on confirm the installed duct system layout conforms to the Duct Design Layout.
Compliance with Verified Duct System Design procedures specified in RA3.1.4.1.1 is prerequisite for compliance with the Buried Ducts on the Ceiling compliance credit. A visual inspection shall confirm the installed duct system layout conforms to the Duct Design Layout. This procedure shall be carried out prior to covering the ducts with insulation.
Ducts designed to be buried shall be insulated to R4.2 or greater. In addition, ducts designed to be in contact with the ceiling shall be not more than 3.5 inches from the ceiling drywall. A sign shall be hung near the attic access that displays a warning: “Caution: Buried Ducts. Markers indicate location of buried ducts.” All ducts that will be completely buried shall have vertical markers that are visible after insulation installation, placed at least every 8 feet of duct length and at the beginning and end of each duct run.
Compliance with Verified Duct System Design procedures specified in RA3.1.4.1.1 is prerequisite for compliance with the Deeply Buried Ducts compliance credit. A visual inspection shall confirm the installed duct system layout conforms to the Duct Design Layout. This procedure shall be carried out prior to covering the ducts with insulation.
Ducts designed to be buried shall be insulated to R4.2 or greater. In addition, ducts designed to be in contact with the ceiling shall be not more than 3.5 inches from the ceiling drywall. A sign shall be hung near the attic access that displays a warning: “Caution: Buried Ducts. Markers indicate location of buried ducts.” All ducts that will be completely buried shall have vertical markers that are visible after insulation installation, placed at least every 8 feet of duct length and at the beginning and end of each duct run.
RA3.1.4.2 Determining Air Handler Airflow for Calculation of Duct Leakage Rate Compliance Targets
For use in establishing the target duct leakage rate compliance criteria, the system air handler airflow shall be calculated using RA3.1.4.2.1, RA3.1.4.2.2, or RA3.1.4.2.3
Default air handler airflow may be used only for homes where the duct system is being tested before the air conditioning and heating system is installed and the equipment specification is not known. For heating only systems the default air handler airflow shall be 0.5 CFM per ft² of Conditioned Floor Area.
For heating only systems the nominal air handler airflow shall be 21.7 CFM per kBtu/hr of rated heating output capacity. For systems with cooling, the nominal air handler airflow shall be 400 CFM per nominal ton of condensing unit cooling capacity as specified by the manufacturer or the heating only value, whichever is greater.
The system airflow shall be as measured according to a procedure in Section RA3.3.3. The system airflow can be used as the air handler airflow for the purpose of establishing duct leakage percentage.
RA3.1.4.3 Diagnostic Duct Leakage
Diagnostic duct leakage measurement is used by installers and raters to verify that total leakage meets the criteria for any sealed duct system specified in the compliance documents. Table RA3.1-2 shows the leakage compliance criteria and test procedures that may be used to demonstrate compliance.
|
Case |
User Application |
Leakage Compliance Criteria (% of Air Handler Airflow) |
Procedure(s) |
|
Sealed and tested new duct systems in single family homes and townhomes |
Installer Testing at Final HERS Rater Testing |
6% |
|
|
Sealed and tested new duct systems in single family homes and townhomes |
Installer Testing at Rough-in, Air Handling Unit Installed |
6% Installer Inspection at Final |
|
|
Sealed and tested new duct systems in single family homes and townhomes |
Installer Testing at Rough-in, Air Handling Unit Not Installed |
4% Installer Inspection at Final |
|
|
Sealed and tested new duct systems in multi-family homes regardless of duct system location. |
Installer Testing at Final HERS Rater Testing |
12%Total Duct Leakage |
|
|
Sealed and tested new duct systems in multi-family homes regardless of duct system location. |
Installer Testing at Final HERS Rater Testing |
6% Leakage to Outside |
|
|
Verified Low Leakage Air Handler with Sealed and Tested Duct System Compliance Credit |
Installer Testing at Final HERS Rater Testing |
compliance target values 6% or less as specified on the Certificate of Compliance |
RA3.1.4.3.1 and |
|
Verification of ducts located entirely in directly conditioned space, and Low leakage ducts in conditioned space compliance credit. |
Installed Testing |
25 CFM Leakage to Outside |
|
|
Sealed and tested altered existing duct systems |
Installer Testing |
15% Total Duct Leakage |
|
|
Sealed and tested altered existing duct systems |
Installer Testing |
10% Leakage to Outside |
|
|
Sealed and tested altered existing duct systems |
Installer Testing and Inspection HERS Rater Testing and Verification |
Fails Leakage Tests but All Accessible Ducts are Sealed Inspection and Smoke Test with 100% Verification |
The objective of this procedure is for an installer to determine or a rater to verify the total leakage of a new or altered duct system. The total duct leakage shall be determined by pressurizing the entire duct system to a positive pressure of 25 Pa (0.1 inches water) with respect to outside. The following procedure shall be used for the fan pressurization tests:
(a) Verify that the air handler, supply and return plenums and all the connectors, transition pieces, duct boots and registers are installed. The entire duct system shall be included in the total leakage test.
(b) For newly installed or altered ducts, verify that cloth backed rubber adhesive duct tape has not been used and if a platform or other building cavity used to house the air distribution system has been newly installed or altered, it contains a duct or is ducted with duct board or sheet metal.
(c) Seal all the supply registers and return grilles except for one large centrally located return grille or the air handler cabinet access panel.
(d) Attach the fan flowmeter device to the duct system at the unsealed return grille or the air handler cabinet access panel.
(e) Install a static pressure probe at a supply register located close to the air handler, or at the supply plenum.
(f) Adjust the fan flowmeter to produce a positive 25 Pa (0.1 inches water) pressure at the supply register or the supply plenum with respect to the outside or with respect to the building space with the entry door open to the outside.
(g) Record the flow through the flowmeter; this is the leakage flow at 25 Pa (0.1 inches water).
(h) Divide the leakage flow by the total air handler airflow determined by the procedure in Section RA3.1.4.2 and convert to a percentage. If the leakage flow percentage is equal to or less than the compliance criterion from Table RA3.1-2 the system passes.
Installers may determine duct leakage in new construction by using diagnostic measurements at the rough-in building construction stage prior to installation of the interior finishing. When using this measurement technique, the installer shall complete additional inspection (as described in section RA3.1.4.3.3) of duct integrity after the finishing wall has been installed. In addition, after the finishing wall is installed, spaces between the register boots and the wallboard shall be sealed. Cloth backed rubber adhesive duct tapes shall not be used to seal the space between the register boot and the wall board.
The duct leakage measurement at rough-in construction stage shall be performed using a fan pressurization device. The duct leakage shall be determined by pressurizing both the supply and return ducts to 25 Pa (0.1 inches water). The following procedure (either RA3.1.4.3.2.1 or RA3.1.4.3.2.2) shall be used: