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Thermal Comfort & Overheating

Part O, CIBSE TM52 and TM59 overheating risk screening for planning submissions

Building Details

Determines ventilation potential and solar exposure characteristics
Required for TM59 Criterion B assessment
Gross internal area of the dwelling
Top floors have increased roof exposure
Direction of main glazed facade
Urban Heat Island effect varies by location

Glazing Characteristics

Percentage of facade that is glazed (typical 20-40%)
Affects solar transmittance
Typical values: Clear 0.75, Low-E 0.3-0.4, Tinted 0.2. Default 0.4 for standard double glazing

Ventilation Strategy

Cross-ventilation and mixed-mode provide best cooling
Can windows be left open safely overnight for free cooling?
Road or rail noise limits natural ventilation cooling

Solar Shading

External shading is highly effective; internal blinds less so
Internal blinds provide partial additional shading
East/west facades benefit most from tree or building shading

Building Construction

Higher mass dampens temperature swings
Better insulation reduces thermal bridging
Green roofs provide significant thermal mass and evaporative cooling

Part O Compliance & Active Cooling

Part O defines zones by overheating risk; Zone 2 requires more stringent assessment
Active cooling significantly reduces overheating risk

Heat Balance Summary

Solar Gain (W) -
Location UHI Multiplier -
Adjusted Solar Gain (W) -
Ventilation Cooling Capacity (W/sqm) -
Thermal Mass Damping Factor -
Net Heat Balance -

Overheating Risk Score (0-100)

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TM59 Overheating Criteria Assessment

Criterion A (Living Rooms/Kitchens/Bedrooms)

Part O Building Regulations - Overheating Risk Screening

Planning Submission Guidance

    Contributing Risk Factors (Ranked by Impact)

    Design Recommendations

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