ID#1083 made on
EQp2 - Environmental Tobacco Smoke (ETS) control
LEED BD+C: New Construction, LEED ID+C: Commercial Interiors, LEED BD+C: Core and Shell, LEED O+M: Existing Buildings
The project, part of a HOPE VI development, is a six-story building containing 119 units of affordable housing. It employs non-combustible construction, interior partitions use metal stud framing. The...
The project, part of a HOPE VI development, is a six-story building containing 119 units of affordable housing. It employs non-combustible construction, interior partitions use metal stud framing. The project development team decided early in the process to render high performance and green in an affordable housing project even though this goal had not been proven in the local market. As compliance with the ETS control provisions is prerequisite, nothing short of the totality of this project's efforts toward LEED1/2 certification as well as all contingent funding is in the balance. The 12/3/2003 Credit Ruling describes an alternate compliance option that may be used in residential buildings. The performance target of 1.25 sq. in. equivalent leakage area per 100 sf. (ELA/100) of total enclosure area is beyond practicality for this project and may generally be so for other buildings of this type. Complex building systems coupled with accepted building practices inhibit continuous internal air(or smoke) separation between spaces. These difficulties multiply in steel construction where structural members and metal stud walls act like ducts connecting spaces within a building. Corrugated metal decks create conduit fields that impose monumental challenges to compartmentalizing by readily available products and skills. Abundant resources might be able to approach the nominal target, but such efforts may distract from more effective means to achieve the intent of the prerequisite. While a robust level of compartmentalization is essential for control of indoor air contaminants, control of pressure differences is also crucial. Each dwelling unit in this building has continuous mechanical exhaust of ~50 cfm and no other mechanical exhaust. Each apartment is also equipped with a dedicated outdoor air intake to help assure that make-up air is drawn directly from the exterior. With the residential ventilation system being direct, in-unit, and constant duty, the common area ventilation system is able to be more nearly balanced thus minimizing mechanically-induced pressure differences between corridors and other spaces as well as between floors. The building has a fluid-applied air barrier at exterior walls and a membrane roof that help to reduce the impact of exterior pressures acting on the building. The alternative compliance option references ASTM E779. We pose that ASTM E1827 is more relevant to the compliance option. It expressly provides guidance to the use of blower-door equipment, which has significant advantages in application to the ETS standard: - More widely available in region and significantly less costly than larger purpose-built pressure testing apparatus. - Multiple blower-doors are capable of inducing sufficient pressure to overcome background variability. It is unlikely that a building's mech. system would be able to induce such pressure unless it is enormously oversized. - Multiple blower-doors able to induce more even depressurization of whole buildings than a single fan. ASTM E779 indicates that "uniform pressure be maintained within the conditioned space to within +/-10% of the measured inside/outside pressure difference." There are also important differences between the standards' measurement procedures. E779 requires multiple measurements across a range of pressures starting as low as 10 Pa. Measurements toward the lower end of the pressure range are subject to greater background variability and, therefore, have a de stabilizing effect on conclusions. E1827 provides a "Single-Point Method" that requires multiple measurements near 50 Pa. Project Proposes: Performance Target: 3.0 ELA/100. In combination with the ventilation strategy and exterior air barrier strategies, this performance target represents huge progress toward effective control of indoor air contaminants. It also requires substantial effort beyond standard industry practice. Methodology: "Single-Point" methodology described in ASTM E1827.
This revised ruling (posted 11/2/05) is intended to restate and clarify the CIR ruling of 5/13/2005. 1 - the requestor's proposal to use ASTM E1827 to verify apartment leakage rates instead of ASTM E779 is unacceptable. Although the two test protocols serve similar purposes, E1827 requires fewer data points (either one or two) over a narrower pressure range (12 to 50 Pa) compared to E779 (five points, at different pressures from 10 to 60 Pa). Compared to E779, E1827 provides a less complete and less robust leakage curve, and thus a less accurate leakage rate value. 2 - the request that the leakage rate requirement be weakened from 1.25 square inches of leakage area per 100 square feet of enclosure area to 3.00 ELA/100 is denied. The value of 1.25 ELA/100 appearing in the 12/03/2003 ruling is the Technical Advisory Group's judgment of a reasonably achievable goal. This goal was derived from knowledge of existing industry practice for good, airtight construction in apartment units. Structural design traits have little if any impact on achievability of the goal; the main drivers are the sealing properties of the doors, windows, and wall finishing (drywall, penetrations, etc.). The requestor's proposed alternative of simply providing 50 CFM of continuous mechanical ventilation does not guarantee that this prerequisite's intent will be met. Moreover, the passive-oriented "prevention" approach of having a tighter leakage rate is more robust to fluctuating real-time conditions than increased mechanical ventilation. As further points of clarification, note that a) the leakage requirement applies to each member of a sample of individual apartment units, not the building as a whole, and b) the whole-apartment unit leakage test must be performed regardless of whether the project uses weatherstripping on the doors to the hallway. Use of weatherstripping only eliminates the need for hallway pressure tests. --------------------- ORIGINAL RULING: The project is proposing a higher allowable equivalent leakage area (ELA) performance standard (3.0 ELA/100 vs. 1.25 ELA/100) on the basis that each residential unit is at roughly the same pressure as adjacent units, which will result in low leakage rates. Based on the information provided, it is not possible to conclude whether the proposed approach will satisfy the prerequisite requirements. First, it is not apparent how the value of 3.0 ELA/100 was calculated. Is this a direct result of applying the ASTM E1827 methodology instead of ASTM E779? Is it correlated to the 50 cfm of exhaust air per unit? It is not clear whether the corridors are positively pressured compared to the apartments. A CIR Ruling on 10/5/2004 provides guidance that corridors should be positively pressurized if weather-stripping is not present on the doors. You will need to meet either the weather-stripping or corridor pressurization requirement to satisfy this prerequisite. Make sure to assess your outdoor air intake design for compliance with ASHRAE 62 (the referenced standard in EQ prerequisite 1). The approach of providing a dedicated outside air intake and high volume exhaust fan in each unit will qualify as an alternate compliance path if these two issues can be resolved.
Related Addenda (Corrections & Interpretations)