CIBSE TM52 Thermal Comfort Analysis

Thermal comfort analysis

Detailed analysis against the CIBSE TM52 thermal comfort metric

CIBSE TM52 Thermal comfort analysis

The risk of overheating in buildings is becoming more prevalent as changing climates and global energy insecurity make the control of indoor climate increasingly problematic. Overheating occurs in a building either through inappropriate design, poor management or inadequate services. Features of a design that support lower winter heating demand (such as large areas of south facing windows, high levels of insulation, low air permeability rates and low thermal mass) can result in excessively high internal temperatures during summer months.

In response to this increasing level of risk, CIBSE have developed an adaptive methodology to assess the predicted level of thermal comfort within a building. This assessment can be carried out at the detailed design stage by way of Dynamic Simulation Model. CIBSE TM52 sets three criteria for compliance. A building that fails two or more of the criteria  is deemed to be at unacceptable risk of overheating:

  1. Criterion 1: Hours of Exceedance

  2. Criterion 2: Daily Weighted Exceedance

  3. Criterion 3: Upper Limit Temperature

Our experienced consultants can guide you smoothly through compliance, from concept to completion. In addition to producing a detailed analysis of your building against the CIBSE TM52 thermal comfort metric, our service includes all the support and advice required to ensure every building achieves a pass.

How Energytest can help

Fast and accurate CIBSE TM52 thermal comfort analysis at a competitive price.

Comprehensive advice and support to ensure you arrive at the most economic and feasible solution to achieve compliance.

CIBSE TM52 reports can be used to aid building design, gain credits under BREEAM, support Planning applications, and satisfy industry requirements: such as for education or healthcare buildings.

Using the same dynamic simulation model, we can provide natural ventilation calculations, daylight analysis, and an assessment of Part L Building Regulations compliance (SBEM).

Where Planning conditions have been applied, we can provide Energy Statements and BREEAM assessments as required.

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Criterion 1 sets a limit of 3% on the number of occupied hours that the operative temperature can exceed the threshold comfort temperature, Tmax, by 1K or more during the occupied hours of a typical non-heating season – 1 May to 30 September. Tmax is a function of the outdoor running-mean temperature.

Criterion 2 deals with the severity of overheating within any one day, which can be as important as its frequency. This is a function of both temperature above Tmax and its duration. This criterion sets a daily limit for acceptability. If each hour (or part-hour) in which the temperature exceeds Tmax by at least 1K is multiplied by the number of degrees by which it is exceeded, then this ‘excess’ should not be more than six degree-hours.

Criterion 3 sets an absolute maximum temperature of (Tmax + 4) °C for a room (Tupp), beyond which the level of overheating is unacceptable. The overheating risk is assessed between the 1st of May and the 31st of September.

  • The geometry of the building.

  • The fabric of the building, including levels of insulation and thermal mass.

  • External and internal shading, such as overhangs, louvres and blinds.

  • The size and orientation of windows, and presence of solar control glazing.

  • Internal heat gains arising from occupants, lighting and equipment.

  • The level of natural or mechanical ventilation provided.

The CIBSE TM52 overheating criteria only apply to “free-running” buildings, i.e. buildings where the peak internal temperature is not controlled by air-conditioning.

What our clients say:

“We have used Energytest to produce all of our SAPs and SBEMs for the last 5 to 6 years. After working with other energy consultants we stuck with Energytest for a number of reasons.  They are very quick to respond with quotes and queries and there is always someone on the other end of the phone. Even if the assessor who produced your calculations isn’t available everyone at Energytest is more than happy to look over the calculations and has the knowledge to answer your query.

They provide more than just a calculation service, they are also problem solvers finding the thermal solutions to make sure our designs pass. I have recently been very impressed with the service we received on a large commercial project. On the calculations for this particular project they produced an additional report alongside the SBEMs detailing how and where we could reduce the specification to significantly save on the build costs whilst meeting the requirements of Part L.”

L Gittens – bi Design Architecture

CIBSE - TM52
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