What CO₂ limit applies to a mechanically ventilated classroom?

BB101 requires ≤1,000 ppm daily average for mechanical ventilation. Naturally ventilated classrooms allow ≤1,500 ppm.

How many pupils should I design for in a standard classroom?

Typically 30–32 pupils plus one teacher in a 56–60 m² room (~1.9 m² per pupil). Confirm with the architect's FF&E schedule.

What ventilation rate should I use for a classroom?

Mechanical ventilation is commonly sized at 8 l/s per person minimum. Cross-check against BB101 CO₂ limits and acoustic criteria.

BuildFlo Design Guide · Sector playbook · BB101 / BB93

Designing a school classroom — MEP checklist

UK classroom MEP checklist: temperatures, CO₂, ventilation, lighting and acoustics. Built-in heat, duct and lux calculators.

General teaching spaces in UK schools sit at the intersection of BB101, UK design guidance, Building Bulletin 93 ( acoustics ), and Part F/L. This playbook is a single-room checklist for building services engineers at Stage 2-3.

Design criteria summary

Parameter	Typical target	Reference
Heating setpoint	20°C occupied	BB101
Overheating limit	≤28°C for max 120 hours/year ( simplified check )	BB101 / TM52 context
CO₂ ( natural ventilation )	≤1,500 ppm daily average	BB101
CO₂ ( mechanical )	≤1,000 ppm daily average	BB101
Ventilation ( mechanical )	8 l/s per person ( minimum check )	UK design guidance / BB101
Lighting	300 lux maintained on desks	BB101
Internal noise	NR 35-40 typical teaching	BB93
Small power	10-25 W/m² allowance	Brief-led

Occupancy for sizing: typically 30-32 pupils + 1 teacher for a standard 56-60 m² classroom (~1.9 m² per pupil). Confirm with architect's FF&E schedule.

Step 1 - Heating load

Size heating for 20°C internal when external is at UK winter design conditions for your location. Account for:

Fabric U-values from architect's spec ( don't assume notional if actual values exist )
Infiltration / ventilation heat loss at minimum fresh air rate
Internal gains from people and lighting ( modest credit at peak heating )

Use the heat loss calculator with typical classroom dimensions.

Step 2 - Ventilation and CO₂

Mechanical ventilation is common on new-build schools. Size fresh air for occupancy and check CO₂ limits in BB101.

For a 32-pupil room at 8 l/s/person → 256 l/s fresh air ( before accounting for infiltration ). Cross-check AHU duty and acoustic attenuation on supply/extract grilles.

Duct sizing check:

Step 3 - Lighting

Target 300 lux maintained on the working plane ( 0.85 m desk height ). Daylight linking and occupancy control are standard on BREEAM schemes.

Allow 10-12 W/m² LED small power for IT and teaching wall ( brief-dependent ).

Step 4 - Coordination items

Radiators / FCUs - Don't block window reveal or teaching wall
Supply grilles - Avoid direct draft on desk rows ( <0.25 m/s at occupied zone )
Light switches - Accessible height, Part M
Emergency lighting - Escape route from classroom to corridor
Sound - NR criteria; attenuators on plant and cross-talk via ventilation

All-in-one classroom calculators

Switch between heat, duct, and lux checks for the same room:

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*This playbook is indicative - DfE, BB101 revision, and academy client standards may override. Use BuildFlo to cite the current clause when it matters.*

Frequently asked questions

What CO₂ limit applies to a mechanically ventilated classroom?: BB101 requires ≤1,000 ppm daily average for mechanical ventilation. Naturally ventilated classrooms allow ≤1,500 ppm.
How many pupils should I design for in a standard classroom?: Typically 30–32 pupils plus one teacher in a 56–60 m² room (~1.9 m² per pupil). Confirm with the architect's FF&E schedule.
What ventilation rate should I use for a classroom?: Mechanical ventilation is commonly sized at 8 l/s per person minimum. Cross-check against BB101 CO₂ limits and acoustic criteria.