RMS-LB 2018 with 12/20 Revisions

Building Investigations Prior to Design 11 ANSI/AARST RMS-LB 2018 (with 1220 revisions) Radon Mitigation Standards for Schools and Large Buildings Note—Investigative actions can include measurements of building air exchange rates and airflow volume and pressures induced by air handlers. 5.4.10 Repairs or modifications Repairs or modifications to HVAC systems that might be recommended as a result of this investigation shall be conducted in accordance with Section 12.8 . 5.4.11 Evaluate design viability Evaluations for viable design shall account for appropriate system design as described in Section 5.3 and otherwise applicable to the mitigation method. 5.4.12 Design diagram To facilitate evaluations for viability, design plan(s) for the proposed layout of the mitigation system(s) shall be annotated on a diagram to include mechanical system components of the systems (i.e., ASD fan, piping and suction points). 5.5 Diagnostic investigation Whenmitigating schools and large buildings, diagnostic procedures shall be performed to enable appropriate and effective system design. Note—Procedures chosen will depend upon the complexity of identifying or characterizing conditions under, beside and within buildings to adequately project the effects of various systemdesigns. Diagnostic investigation can include one or multiple procedures such as: sub-slab pressure field extension (PFE) tests or analysis; visual assessment(s); characterization of pressure or air exchange rates between indoors and outdoors and also between floors or adjoining air spaces; and diagnostic radon measurements at locations of interest (e.g., common areas, mechanical spaces and spaces not in ground contact). 5.5.1 ASD designs Design of ASD systems in schools and large buildings shall include a pressure field extension analysis. PFE Analysis is a set of commonly needed diagnostic techniques to aid design and optimization of soil depressurization systems: a) Qualitative evidence shall be sought to identify the distance potential of PFE across the soil gas collection plenum (e.g., airspace under slabs or soil gas retarder). b) Quantitative measurements shall also be employed for analytical determination of: 1. air volume capacity needed to overcome leakage from any side of the soil gas collection plenum such as at the soil or at foundation cracks; and 2. vacuum strength needed to overcome indoor air pressures and resistance posed by fill materials within the soil gas collection plenum. Quantitative Measurements The PFE analysis shall be conducted under closed-building or normal operating conditions using, among other tools, a differential pressure gauge that is: a) capable of reading to 1/1000 inch water column (.25 Pa); and b) calibrated in accordance with national standards or manufacturers’ recommendations. Reliance on Experience in Like Structures When designing for like structures within the same building complex: Information gained at one structure regarding air volume and fan vacuum needs can sometimes be applied to similar structure(s). For this consideration, the minimum requirements of this standard have been met if: a) The like structures being compared are located within the same building complex and are of similar size and built with similar construction practices; b) At least one PFE measurement is made in each structure that indicates a similar distance for PFE; and c) Sufficient additional information is gained from each structure to indicate like conditions exist. Pressure Across the Building Shell Informative advisory —Characterization of pressure differences between indoors and outdoors can be a critical diagnostic tool in high-rise buildings or buildings with large air handlers.