Overheating Assessment for Non-Domestic Buildings
TM52 Commercial Overheating
Dynamic thermal modelling for schools, offices, care homes and other commercial buildings. BREEAM compliance and planning conditions.
Prefer to talk to someone? Call 0333 567 9010.
TM52 Commercial Overheating
What is TM52?
CIBSE methodology for assessing overheating risk in non-domestic buildings.
Which buildings need TM52?
Schools, offices, care homes, healthcare, and buildings seeking BREEAM credits.
What are the criteria?
Three criteria must be met: hours of exceedance, daily weighted exceedance, and upper limit.
Why is it required?
BREEAM Hea 04, planning conditions, BB101 for schools, HTM for healthcare.
How much does it cost?
From £350 depending on building size and complexity.
How long does it take?
Typically 4-7 working days depending on complexity.
Need TM52 for BREEAM or planning? We provide clear reports and practical mitigation advice.
What Is TM52?
TM52 is the CIBSE methodology for assessing overheating risk in non-domestic buildings. It uses dynamic thermal simulation to predict internal temperatures and assess comfort.
Unlike domestic assessments (which use TM59), commercial buildings use TM52 criteria. The methodology simulates the building hour-by-hour through a Design Summer Year and assesses three criteria relating to temperature exceedance and thermal comfort.
TM52 is commonly required for BREEAM assessments (Hea 04 credit), planning conditions, and specific building types like schools (BB101) and healthcare facilities (HTM guidance).
Which Buildings Need TM52?
TM52 assessment is commonly required for:
Education
- ✓ New schools and academies
- ✓ School extensions and refurbishments
- ✓ Universities and colleges
- ✓ BB101 compliance requirement
Healthcare
- ✓ Care homes and nursing facilities
- ✓ Hospitals and clinics
- ✓ GP surgeries
- ✓ HTM guidance compliance
Offices
- ✓ New office buildings
- ✓ Office refurbishments
- ✓ Speculative developments
- ✓ BREEAM Excellent/Outstanding
Other Commercial
- ✓ Retail buildings
- ✓ Community centres
- ✓ Libraries and public buildings
- ✓ Mixed-use developments
Why Is TM52 Required?
TM52 may be required for:
- BREEAM Hea 04 - Thermal comfort credit requires TM52 assessment to demonstrate overheating risk is addressed.
- Planning conditions - Many local authorities require overheating assessment as a planning condition for major developments.
- BB101 (Schools) - Building Bulletin 101 requires dynamic thermal modelling for new school buildings.
- HTM (Healthcare) - Health Technical Memoranda reference TM52 for healthcare building design.
- Client requirements - Many institutional clients require TM52 as part of design validation.
- Part O adjacency - Mixed-use buildings with residential elements may need both TM52 and TM59.
TM52 Pass Criteria
TM52 sets three criteria - a space fails if any two criteria are exceeded:
Criterion 1: Hours of Exceedance
The number of hours where the operative temperature exceeds the comfort threshold by 1K or more should not exceed 3% of occupied hours.
Criterion 2: Daily Weighted Exceedance
On any one day, the weighted exceedance (We) should not exceed 6 degree-hours. This prevents severe overheating events.
Criterion 3: Upper Limit Temperature
The operative temperature should not exceed the comfort threshold by 4K or more (i.e., absolute upper limit).
The comfort threshold is based on adaptive comfort theory - it varies with external temperature, allowing higher internal temperatures when people have adapted to warmer weather.
TM52 Assessment Pricing
Pricing depends on building size and complexity.
Small Commercial
From £350
Small offices, single classrooms, small care homes. Straightforward geometry.
Medium Commercial
From £500
Small schools, medium offices, larger care homes. Multiple zones.
Large/Complex
From £750
Large schools, hospitals, complex geometry. Multiple worst-case zones.
How TM52 Assessment Works
We build a thermal model of your building and simulate performance through design summer conditions.
-
1
Send us your drawings
Floor plans, elevations, sections, construction details, glazing schedule, ventilation strategy, and internal gains information.
-
2
We identify worst-case zones
We determine which spaces are at highest risk - typically south/west facing with high glazing or internal gains.
-
3
Build thermal model
We create a detailed thermal model of the building in approved dynamic simulation software.
-
4
Run annual simulation
The model is simulated hour-by-hour through the Design Summer Year to assess TM52 criteria.
-
5
Receive results and recommendations
Pass/fail assessment for each zone with mitigation recommendations if needed. Report formatted for BREEAM or planning submission.
Common TM52 Mitigation Strategies
If initial modelling shows overheating risk, these strategies often achieve compliance:
Passive Measures
- ✓ External solar shading (brise soleil, louvres)
- ✓ Solar control glazing (low g-value)
- ✓ Increased thermal mass (exposed soffits)
- ✓ Night cooling ventilation strategy
Active Measures
- ✓ Mixed-mode ventilation
- ✓ Mechanical ventilation with night cooling
- ✓ Comfort cooling (if passive measures insufficient)
- ✓ Demand-controlled ventilation
We rank recommendations by cost-effectiveness and energy impact. Passive measures preferred where possible.
TM52 FAQ
What's the difference between TM52 and TM59?
Do all rooms need to be modelled?
What BREEAM credits does TM52 support?
Can you model mechanical cooling?
Do you model natural ventilation?
Need TM52 for your commercial project?
Professional TM52 assessments for BREEAM, planning, and regulatory compliance.