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Ventilation design verification

Offices, a hospital ward and an operating theatre run through the same calculation the app uses, compared with CIBSE Guide A 2015, Approved Document F Volume 2, HTM 03-01 and Approved Document L Volume 2. Two cases use the calculator's ASHRAE setting and are checked against ASHRAE 62.1.

Result
14 of 14 checks pass
Cases
8 worked examples
Version / published
v1.0 · 2026-09-28
Engine fingerprint
9f46f99cf62e

Why we publish this

A ventilation rate is only as good as the table it came from. Each case below names the table, paragraph and page it is checked against, so the rate, the effectiveness correction and the fan power limit can be traced to the document rather than to our code. The UK documents come first because the calculator is CIBSE first; the ASHRAE cases cover the setting that switches the calculation to 62.1.

Editions

  • Approved Document F Volume 2 has no 2026 edition, so offices are checked against the 2021 edition.
  • Approved Document L Volume 2, 2026 edition, takes effect on 24 March 2027. Its Table 5.9 prints the same specific fan power limits as Table 6.9 of the 2021 edition in force until then.
  • ASHRAE 62.1-2025 is the 2022 standard with its addenda. The rates checked here are those printed in 62.1-2022; the air density factor comes from addendum j, which the 2025 edition incorporates.

What is not compared, and why

  • Schools (BB101:2018). The classroom rate is checked in the regression suite; BB101 is not among the documents this page quotes from.
  • Commercial kitchens on the CIBSE path. These are sized by the BESA DW172 thermal convection method, which prints no worked example to compare against.
  • The CO₂ check (CIBSE Guide B2 §2.2.2.4). It raises a warning rather than producing a number, so there is nothing to compare.

How to read the tables

  • Expected is the value printed in the standard, or a hand calculation from printed values. The working is shown under each quantity.
  • Tolerance is exact for tabulated values and selected sizes, and ±2 % for calculated quantities such as the outdoor-air and supply flows.
  • Every check re-runs automatically whenever the calculation code changes, and this page is regenerated from those results. The engine fingerprint above identifies the calculation code the results came from.

Sources

  • Approved Document F, Volume 2: Buildings other than dwellings, 2021 edition
  • Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
  • ANSI/ASHRAE Standard 62.1-2022, Ventilation and Acceptable Indoor Air Quality
  • Addendum j to ANSI/ASHRAE Standard 62.1-2022 (2024), incorporated in 62.1-2025
  • CIBSE Guide A 2015, Environmental design
  • HTM 03-01 Specialised ventilation for healthcare premises, Part A (2021)

Printed page numbers refer to the editions above.

Worked examples

VD-01

Open-plan office, 200 m² with 30 people, mixing ventilation (CIBSE)

Inputs

  • Open-plan office, 200 m², 2.7 m high, 30 people
  • Mixing ventilation, high-level supply cooler than the room
Checks for case VD-01
QuantityExpectedSourceMEPCalcΔToleranceResult
Outdoor air required
10 L/s per person × 30 = 300 l/s. The Approved Document F Vol 2 §1.32 area leg, 1 L/s·m² × 200 = 200 l/s, is lower.
300l/s
CIBSE Guide A 2015, Environmental design
Table 1.5, offices (held copy p71)
300l/s0.00 %±2 %Pass
Supply air after ventilation effectiveness
Mixing, high-level supply, supply cooler than the room: Ev 0.9 to 1.0. The calculation takes the lower 0.9: 300 ÷ 0.9 = 333.3 l/s.
333.33l/s
CIBSE Guide A 2015, Environmental design
Table 1.11 (held copy p101)
333.33l/s0.00 %±2 %Pass

VD-02

Cellular office, 30 m² with 2 people (CIBSE): the Approved Document F floor governs

Inputs

  • Private office, 30 m², 2.7 m high, 2 people
Checks for case VD-02
QuantityExpectedSourceMEPCalcΔToleranceResult
Outdoor air required
Per person 10 × 2 = 20 l/s; per floor area 1 × 30 = 30 l/s. §1.32 takes whichever gives the higher total: 30 l/s.
30l/s
Approved Document F, Volume 2: Buildings other than dwellings, 2021 edition
§1.32 (held copy p14)
30l/s0.00 %±2 %Pass

VD-03

Open-plan office, 200 m² with 30 people, displacement ventilation (CIBSE)

Inputs

  • As VD-01, with displacement ventilation (low-level supply cooler than the room)
Checks for case VD-03
QuantityExpectedSourceMEPCalcΔToleranceResult
Supply air after ventilation effectiveness
Displacement, supply cooler than the room: Ev 1.2 to 1.4. The calculation takes the mid value 1.3: 300 ÷ 1.3 = 230.8 l/s.
230.77l/s
CIBSE Guide A 2015, Environmental design
Table 1.11 (held copy p101)
230.77l/s0.00 %±2 %Pass

VD-04

Hospital general ward, 60 m² with 6 patients (HTM 03-01)

Inputs

  • General ward (level 0 and 1 care), 60 m², 2.7 m high (162 m³), 6 patients
Checks for case VD-04
QuantityExpectedSourceMEPCalcΔToleranceResult
Outdoor air required
6 ac/h × 162 m³ ÷ 3.6 = 270 l/s. The §4.22 minimum, 10 L/s per person × 6 = 60 l/s, is lower.
270l/s
HTM 03-01 Specialised ventilation for healthcare premises, Part A (2021)
Appendix 2, general ward (printed p147); §4.22 (printed p16)
270l/s0.00 %±2 %Pass

VD-05

Conventional operating theatre, 165 m³ (HTM 03-01 standard layout 1)

Inputs

  • Conventional operating theatre, 55 m² × 3.0 m = 165 m³, the volume of the printed standard layout
Checks for case VD-05
QuantityExpectedSourceMEPCalcΔToleranceResult
Air required for the air-change rate
Standard layout 1: theatre 165 m³ at not less than 22 ac/h, total flow 1.01 m³/s (primary 0.73 + 0.28 from the lay-up prep). 22 × 165 ÷ 3.6 = 1008.3 l/s.
1010l/s
HTM 03-01 Specialised ventilation for healthcare premises, Part A (2021)
Appendix 7, standard layout 1 (printed p154)
1008.33l/s0.17 %±2 %Pass

VD-06

Office space, 100 m² with 10 people, at sea level (ASHRAE setting)

Inputs

  • Office space, 100 m², 10 people, ceiling supply of cool air
  • Outdoor-air intake at 0 m
Checks for case VD-06
QuantityExpectedSourceMEPCalcΔToleranceResult
Outdoor air required
Vbz = Rp × Pz + Ra × Az = 2.5 × 10 + 0.3 × 100 = 55 l/s.
55l/s
ANSI/ASHRAE Standard 62.1-2022, Ventilation and Acceptable Indoor Air Quality
Table 6-1, office space (printed p19); Equation 6-1 (printed p16)
55l/s0.00 %±2 %Pass
Supply air after ventilation effectiveness
Ez 1.0 for ceiling supply of cool air: Voz = 55 ÷ 1.0 = 55 l/s.
55l/s
ANSI/ASHRAE Standard 62.1-2022, Ventilation and Acceptable Indoor Air Quality
Table 6-4, ceiling supply of cool air (printed p22)
55l/s0.00 %±2 %Pass

VD-07

The same office with its outdoor-air intake at 1600 m (ASHRAE setting)

Inputs

  • As VD-06, outdoor-air intake 1600 m above sea level
Checks for case VD-07
QuantityExpectedSourceMEPCalcΔToleranceResult
Air density correction factor Eρ
1600 m falls in the 1317 to 1664 m band: Eρ = 1.20.
1.2
Addendum j to ANSI/ASHRAE Standard 62.1-2022 (2024), incorporated in 62.1-2025
Table 6-5 and Equation 6-2
1.20.00 %exactPass
Supply air after ventilation effectiveness
Voz = Vbz ÷ Ez × Eρ = 55 ÷ 1.0 × 1.20 = 66 l/s.
66l/s
Addendum j to ANSI/ASHRAE Standard 62.1-2022 (2024), incorporated in 62.1-2025
Table 6-5 and Equation 6-2
66l/s0.00 %±2 %Pass

VD-08

Specific fan power limits for central balanced mechanical ventilation

Inputs

  • Central balanced mechanical ventilation with heating and cooling, new and existing building
  • All other central balanced mechanical ventilation, new and existing building
Checks for case VD-08
QuantityExpectedSourceMEPCalcΔToleranceResult
SFP limit, central balanced MV with heating and cooling, new building
2W/(l/s)
Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
Table 5.9 (printed p54)
2W/(l/s)0.00 %exactPass
SFP limit, central balanced MV with heating and cooling, existing building
2.6W/(l/s)
Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
Table 5.9 (printed p54)
2.6W/(l/s)0.00 %exactPass
SFP limit, all other central balanced MV, new building
1.5W/(l/s)
Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
Table 5.9 (printed p54)
1.5W/(l/s)0.00 %exactPass
SFP limit, all other central balanced MV, existing building
2W/(l/s)
Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
Table 5.9 (printed p54)
2W/(l/s)0.00 %exactPass