Ensure envelope construction meets air tightness requirements through verified performance testing.
Building envelope air tightness must meet or exceed the performance target of 0.40 cfm/sf when tested in accordance with ASTM E779. A multi-point Envelope Air Tightness Performance Test will be performed during the Final Site Inspection using calibrated blower door diagnostic test equipment. The test result is expressed in terms of Envelope Leakage Ratio (ELR75) at 75 Pascals of pressure difference between the building interior and exterior.
ELR75 < 0.40
Additional points can be achieved for better performance results (i.e. BE 1: Exceed Envelope Air Tightness Performance Test).
Note: If the results of the Envelope Air Tightness Test exceed 0.40 ELR75 (0.25 ELR75 for Performance Badge) then leakage pathways must be identified and sealed, and a re-test will be required (at additional cost) before a project can be certified.
Building testing will follow the ECLC Envelope Air Leakage Testing Protocol.
- Final Site Inspection – Envelope Air Tightness Performance Test
ELR75 (Envelope Leakage Ratio at 75 Pa) The Envelope Leakage Ratio (ELR) is the quantity of air leakage expressed in cubic feet per minute at an induced pressure difference of 75 Pa (CFM75) divided by the total square footage of the building’s thermal envelope (shell area).
CFM75 (Cubic Feet per Minute at 75 Pa) The volume of air in cubic feet per minute moved through a fan that is set to induce a 75 Pa pressure differential between conditioned and unconditioned space.
Shell Area- The total square footage of a building’s thermal envelope: Building Envelope Floor + Envelope Ceiling/Roofline + Exterior Envelope Wall. Typically, these are insulated areas.
Pascal- A Pascal (Pa) is a small metric unit of pressure and is commonly used in lieu of inches of water column (1” water column = 248 Pa; 75 Pa = 0.3 inches of water column).
Building Thermal Envelope- The building thermal envelope is the portion of the building envelope that is comprised of the continuous air barrier and insulation and separates conditioned space from unconditioned space.
A 7,600 square foot building (First floor: 3,600 square feet and second floor: 4,000 square feet) has a shell area of 13,920 square feet. The blower door test measures a flow of 3,340 CFM75. What is the Envelope Leakage Ratio at 75 Pa? ELR75 is calculated by dividing the measured CFM75 by the total shell area of the envelope.