Specifications

2008 Residential Appendices RA3-4

Appendix RA3 – Residential Field Verification and Diagnostic Test Protocols

shall be made available to the enforcement agency, installing contractor, and HERS rater for use during the

installation work and for all applicable inspections.

RA3.1.4.1.2 Verifying the Duct System Installation

The location

of all supply and return registers shall be verified from an inspection of the interior of the dwelling

unit. The location of the 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 design shall not be allowed.

RA3.1.4.1.3 Verification

for Ducts to be buried in Attic Insulation

This procedure and the procedure of RA3.1.4.2 shall be carried out prior to covering the ducts with insulation.

Ducts to be buried shall be insulated to R4.2 or greater. In addition ducts designed to be in contact with the

ceiling shall be in continuous contact with the ceiling drywall or ceiling structure not more than 3.5 inches from

the ceiling drywall. A sign must be hung near the attic access reading “Caution: Buried Ducts. Markers indicate

location of buried ducts.” All ducts which will be completely buried shall have vertical markers which will be

visible after insulation installation at not more than every 8 feet of duct length and at the beginning and end of

each duct run.

RA3.1.4.2 System Fan Flow

For the pu

rpose of establishing duct leakage criteria, the system fan flow shall be calculated using RA3.1.4.2.1,

RA3.1.4.2.2, or RA3.1.4.2.3.

RA3.1.4.2.1 Default Sys

tem Fan Flow

Default system fan flow 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 fan flow shall be 0.5 CFM per ft

of Conditioned Floor Area.

RA3.1.4.2.2 Nominal Sys

tem Fan Flow

For heating only systems the fan flow shall be 21.7 CFM x Heating Capacity in thousands of Btu/hr. For

systems with cooling, the fan flow shall be 400 CFM per nominal ton of cooling capacity as specified by the

manufacturer or the heating only value, whichever is greater.

RA3.1.4.2.3 M

easured System Fan Flow

The fan flow shall be as measured according to a procedure in Section RA3.3.3

RA3.1.4.3 Diagnostic Duct Leakage

Diag

nostic 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. Diagnostic Duct Leakage from Fan

Pressurization of Ducts (Section RA3.1.4.3.1) is the only procedure that may be used by a HERS rater to verify

duct sealing in a new home. Table RA3.1-2 shows the leakage criteria an

d test procedures that may be used

to demonstrate compliance.