Ventilation basis of design, Silver Station Middle School conversion
Schematic design ventilation narrative for converting a 1978 office building in Silver Station, Virginia, into a grades 6–8 middle school. Performance requirements are organized by CSI MasterFormat section with no manufacturers named, and each one traces to the source documents. The school needs 2.6 times today’s outdoor airflow, so Floors 2 and 3 get a new air handling unit.
Sources: Educational Specifications Rev C, HVAC Design Standards, TAB report, condition survey, drawings and life safety plansScope: ventilation and exhaust, with controls interfaceOrganized by CSI MasterFormatOwner: Silver Station City Public SchoolsPrepared Nov 5, 2026
Summary
Outdoor air · AHU-1 and AHU-2
The school needs 2.6 times today’s outdoor air
At 30 students per classroom, design outdoor airflow is 11,010 cfm, against 4,200 cfm measured in the TAB report (p. 3). Existing AHU-1 can carry Floors 1 and 4: 3,810 of a maximum 4,400 cfm per the condition survey (p. 9).
Floors 2 and 3 get a new AHU-2 rated 7,500 cfm, enough for up to 32 students per classroom.
Conflicting requirements · BOD-1
Design Standards and Ed Specs disagree on airflow control
The Design Standards (p. 12) require constant volume in every room. The Educational Specifications (p. 7) require demand-controlled ventilation in classrooms and the cafeteria. The narrative specifies DCV in those 15 zones and flags it for a decision.
The owner needs to pick one approach. Unit sizes don’t change.
Proprietary-name check
3 proprietary requirements in the sources, 0 in the narrative
The Design Standards (p. 21) require controls by the same manufacturer as the existing BAS. That is replaced with native BACnet/IP integration into the existing BAS front end. The requirements for diffusers (Design Standards p. 19) and replacement parts (condition survey p. 10) are rewritten the same way.
The narrative by MasterFormat section
Pick a section to see its requirements and the ones that apply to it from higher levels of the hierarchy. Click a requirement to see the source passage behind it.
Requirements in the narrative
Traced to the sources
Conflicting requirements in the sources
Proprietary terms in requirement text
Highlight in the tree
Unit
Airflow control
Design outdoor air after renovation
Outdoor air today per TAB report (AHU-1, whole building)
Compared with today
Outdoor air with DCV zones unoccupied
Design outdoor airWith DCV zones unoccupiedUnit maximum airflowToday per TAB report
Voz per zone = (Rp × Pz + Ra × Az) ÷ Ez + toilet exhaust makeup (50 cfm per fixture), with Ez = 1.0, rounded up to the next 10 cfm. Classrooms and the science classroom use the selected enrollment plus one teacher. DCV minimum = Ra × Az. Both units are 100% outdoor air, so unit airflow is the sum of its zones.
Sources and method
Sources
SSCPS_Educational_Specifications_RevC.pdfEducational specifications with room data sheets for 64 rooms46 pages
SSCPS_HVAC_Design_Standards_2025.pdfOwner’s HVAC and controls design standards38 pages
TAB_Report_AHU-1_2024-03.pdfMost recent test and balance report with measured airflows6 pages
Existing_Conditions_Survey_Mechanical.pdfCondition assessment of AHU-1, ductwork and shafts14 pages
A-101_to_A-104_Floor_Plans_SD_RevB.pdfFloor plans after renovation with room numbers and areas4 sheets
LS-101_to_LS-104_Life_Safety_Plans_SD.pdfFire-resistance-rated assemblies, shafts and HVAC shutdown4 sheets
Method
Room data sheets in the Educational Specifications and SD floor plans A-101 to A-104 were read room by room: number, area, occupancy and use.
Outdoor air was calculated for each zone with the ASHRAE 62.1 Ventilation Rate Procedure (Rp, Ra, Ez = 1.0), plus makeup for toilet exhaust, and summed by unit.
AHU-1 capacity from the condition survey was compared with the airflow measured in the TAB report.
Each requirement in the sources was placed in the MasterFormat section that best matches it. Requirements repeated on room data sheets are stated once, at the highest level where they apply.
Requirement text in the sources and in the narrative was searched for manufacturer names, model numbers, “or equal,” “OEM” and “match existing.” Hits in the sources were rewritten as performance requirements.
Conflicting requirements were flagged for an owner decision instead of being resolved silently.
Assumptions and limitations
30 students plus one teacher per classroom (Educational Specifications p. 4). The cafeteria is sized for 130 seats per lunch period.
AHU-1 maximum airflow of 4,400 cfm is the condition survey’s estimate; confirm with fan selection in design development.
Ez = 1.0 and the occupancy category assigned to each room set the outdoor air rates. The mechanical engineer of record (licensed PE) should confirm both in design development.
Space heating and cooling (fan coil units and hydronic plant) are covered in a separate narrative.
Code basis: 2021 Virginia Uniform Statewide Building Code (Virginia Construction Code with the IMC, and the Virginia Energy Conservation Code). The 2024 edition is scheduled to take effect in October 2027; confirm the edition in effect at permit application with the building official.
Section numbers and titles follow CSI MasterFormat. Quantities, products and execution requirements are added in the construction documents.
Fire/smoke damper locations follow the SD life safety plans and change if those are revised.