Public Review Draft. ASHRAE Standard

Transcription

1 BSR/ASHRAE Addendum s to ANSI/ASHRAE Standard Public Review Draft ASHRAE Standard Proposed Addendum s to Standard , Ventilation and Acceptable Indoor Air Quality in Low- First Public Review (September 2009) Full Public Review (Draft Shows Proposed Changes to Current Standard) This draft has been recommended for public review by the responsible project committee. To submit a comment on this proposed addendum, go to the ASHRAE website at and access the online comment database. The draft is subject to modification until it is approved for publication by the Board of Directors and ANSI. Until this time, the current edition of the standard (as modified by any published addenda on the ASHRAE web site) remains in effect. The current edition of any standard may be purchased from the ASHRAE or by calling or (for orders in the U.S. or Canada). This standard is under continuous maintenance. To propose a change to the current standard, use the change submittal form available on the ASHRAE web The appearance of any technical data or editorial material in this public review document does not constitute endorsement, warranty, or guaranty by ASHRAE of any product, service, process, procedure, or design, and ASHRAE expressly disclaims such. September 11, This draft is covered under ASHRAE copyright. Permission to reproduce or redistribute all or any part of this document must be obtained from the ASHRAE Manager of Standards, 1791 Tullie Circle, NE, Atlanta, GA Phone: , Ext Fax: standards.section@ashrae.org. AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS, INC Tullie Circle, NE Atlanta GA

2 (This foreword is not part of this standard. It is merely informative and does not contain requirements necessary for conformance to the standard. It has not been processed according to the ANSI requirements for a standard and may contain material that has not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.) Foreword The addendum proposes coefficients to account for the effect of system types and operation. The proposed system coefficients are based on three factors: the difference between balanced and unbalanced systems; the difference between fully ducted and not fully ducted systems; and the effect of mixing. The addendum increases mechanical ventilation system flow rates for systems that are unbalanced and not fully ducted. The addendum does not increase mechanical ventilation system flow rates for systems that are balanced and fully ducted or systems that are balanced and not fully ducted that have a provision for mixing and systems that are unbalanced and fully ducted that have a provision for mixing. A simulation study was performed to evaluate the proposed changes. The analysis supporting the coefficients values was based on annual average exposure and assumed that contaminants are distributed in houses roughly 1/3 for occupants, 1/3 for furnishings and materials uniformly distributed throughout the house and 1/3 split between the kitchen and the bathrooms. The addendum excludes buildings that have leakage rates of 7 50 Pa or greater; systems in building enclosures other than single family detached; and systems installed according to the Existing Building Appendix of Standard The proposed change could increase installation and operating costs for some systems as it will require either larger fan flow rates or provision of minimum turnover. [Note to Reviewers: This addendum makes proposed changes to the current standard. These changes are indicated in the text by underlining (for additions) and strikethrough (for deletions) except the reviewer instructions specifically describe some other means of showing the changes. Only these changes to the current standard are open for review and comment at this time. Additional material is provided for context only and is not open for comment except as it relates to the proposed changes.] Addendum s to Reviewer Note: Revised the definition in Section 3 as follows: balanced ventilation system: one or more fans that simultaneously supply outdoor air and exhaust building air at substantially equal rates. A single supply point and a single exhaust point that are located in the same room does not qualify as a balanced ventilation system. If the supply and exhaust points are connected to a central forced air distribution system then the central system fan must operate simultaneously with the ventilation fan. Reviewer Note: Add new definitions to Section 3 as follows: fully-ducted ventilation system: a ventilation system that supplies ventilation air through a duct to each common area and bedroom, or a ventilation system that exhausts air through a duct to outdoors from all kitchens and bathrooms, or a ventilation system that exhausts air through a duct to outdoors from all bedrooms.

3 forced air distribution system: an air duct and fan system by ducts supply air to all habitable spaces of the conditioned space and a provision for return air exists from all habitable spaces served with supply air. minimum turnover: whole-building air mixing such that at least 50 % of the house air volume is moved through a forced air distribution system each hour. Reviewer Note: Revise Section 4.1 as follows: 4.1 Ventilation Flow RateVentilation Rate Mechanical ventilation air shall be provided to each dwelling unit using a balanced fully-ducted ventilation system to provide whole-building ventilation with outdoor air at no less than the rate specified in Table 4.1a and Table 4.1b or, equivalently, Equations 4.1a and 4.1b or using alternative systems with ventilation flow rates as specified by equation 4.2.A mechanical exhaust system, supply system, or combination thereof shall be installed for each dwelling unit to provide whole-building ventilation with outdoor air each hour at no less than the rate specified in Table 4.1a and Table 4.1b or, equivalently, Equations 4.1a and 4.1b, based on the floor area of the conditioned space and number of bedrooms. Q v =0.01 A floor + 7.5(N br + 1) (4.1a) Q v = ventilation flow rate in cubic feet per minute (cfm) A floor = floor area in square feet (ft 2 ) Q v =0.05 A floor +3.5(N br + 1) (4.1b) Q v = ventilation flow rate in litres per second (L/s) A floor = floor area in square meters (m 2 ) Q fan = 0.01A floor + 7.5(N br + 1) (4.1a) Q fan = fan flow rate in cubic feet per minute (cfm), A floor = floor area in square feet (ft 2 ), Q fan = 0.05A floor + 3.5(N br + 1) (4.1b) Q fan = fan flow rate in liters per second (L/s), A floor = floor area in square meters (m 2 ), 2

4 TABLE 4.1a (I-P) Ventilation Flow RateAir Requirements, cfm Bedrooms Floor Area (ft 2 ) >7 < > TABLE 4.1b (SI) Ventilation Flow RateAir Requirements, L/s Bedrooms Floor Area (m 2 ) >7 < > Reviewer Note: Remainder of Section 4.1 remains the same. Reviewer Note: Insert new Section as follows and renumber subsequent sections Fan Flow Rate The required ventilation flow rate specified in Table 4.1a and Table 4.1b or, equivalently, Equations 4.1a and 4.1b, shall be provided by fan flow rate as follows: Q fan = Q v C s (4.2) Q fan = fan flow rate (cfm) C s is the system coefficient from Table 4.2 Exception 1: All systems installed in building enclosures having a leakage rate of 7 ach@50 Pa or greater as tested using ASTM E shall have a C s =1.0. 3

5 Exception 2: All systems installed in building enclosures other than single family detached dwellings shall have a C s =1.0. Exception 3: All systems installed according to the Existing Buildings Appendix shall have a C s =1.0. Reviewer Note: Renumber the existing Table 4.2 as Table 4.3 and add a new Table 4.2 as follows Table 4.2 System Coefficient based on system type Ventilation Type Ventilation Ducting With Minimum Turnover Without Minimum Turnover Balanced Fully ducted Not fully ducted Not Balanced Fully ducted Not fully ducted Reviewer Note: Revise Section 4.4 as follows: Addendum b of (included in the 2008 Supplement) made changes to Section 4.4 in the published standard. The 2008 Supplement is available for free download from the ASHRAE website at Delivered Ventilation. The delivered ventilation rate shall be calculated as the larger of the total supply or total exhaust and shall be no less than specified in Section 4.1 during each hour of operation. Exception: The effective ventilation rate of an intermittent system is the combination of its delivered capacity, fractional on-time, cycle time, and the ventilation effectiveness from Table 4.2. The fan flow rate required to achieve an effective ventilation rate that is equivalent to the continuous ventilation requirement shall be calculated from the following equation: Q fan.intermittent = Q rfan /(ε f) (4.2) Q f = fan flow rate during the on-cycle, Q r = ventilation air requirement (from Table 4.1a or Table 4.1b), Q fan.intermittent = fan flow rate during the intermittent operation on-cycle (cfm) T cyc = fan cycle time, defined as the total time for 1 on- and 1 off-cycle (used in Table 4.32) ε = ventilation effectiveness (from Table 4.32), f = fractional on time, defined as the on-time for one cycle divided by the cycle time. 4