Planning Stage

Design and Construction

Completion & Post Completion

Part O – Overheating Calculation

At Focus 360 Energy, we provide an Overheating Risk Assessment service as part of our New Build Services. This assessment is designed to assess the risk of overheating that may occur in a new building or extension, and provides guidance on potential solutions.

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What is an Overheating Risk Assessment?

At Focus 360 Energy, we are dedicated to providing our customers with the best risk assessment services. Our Specialised Assessment Procedure (SAP) Calculation tools allow us to accurately assess the level of overheating risk associated with a building and its location. We use two methods, such as the Simplified Method and Dynamic Thermal Modelling technique in order to thoroughly determine the potential for excessive heating within a dwelling.

Our SAP results range from negligible-low to moderate, high or even excessive levels of risk determined by factors including solar gain, window positions for ventilation and cross-ventilation, as well as thermal mass summer temperature depending on your dwelling’s geographic area. Anything below moderate risk is considered acceptable according to current Approved Document O: Overheating standards.

The SAP methodology is a powerful tool to help you navigate the complex London planning requirements, and our team of knowledgeable experts are on hand to provide tailored support.

Please don’t hesitate to reach out if you have any questions or need further guidance – we’re happy to help with all your SAP Calculation requirements!

  • SAP Calculations for New Builds – often done in tandem with Part O Calculations
  • SAP Calculations for Conversions
  • SAP Calculations for Extensions

Often coupled with:

SAP Calculation - New Build
Energy Statement
Energy Statement - London Plan
Air Pressure Testing
Flood Risk Assessment
BREEAM Assessment
Water Consumption Calculation (Part G)

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Why performing an Overheating Risk Assessment is important

Overheating Risk Assessments are important for a variety of reasons, particularly in the UK. Overheating in buildings can lead to discomfort and potential health issues, such as dehydration and heat exhaustion.

In London and Manchester, the urban heat island effect makes cities particularly prone to soaring temperatures. During summer nights, London can become 8 degrees hotter than its surrounding rural areas. To combat this issue, designers must offer effective shading measures such as shutters, improved glazing g-values or overhangs for windows facing away from the north.

To prevent this, Focus 360 Energy offer detailed Overheating Risk Assessments that provide an informed insight into the likely risk of overheating in a building.

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What is the Simplified method?

We understand that meeting the requirements detailed in Document O may seem like a daunting task. However, our Simplified Method provides an alternative route to assess the risk of overheating without having to undertake a more complex TM59 assessment. This method focuses on two areas: limiting solar gains and removing excess heat, with different requirements depending on the location of your building and whether it has cross-ventilation or not.

We calculate this by looking at the ratio between glazing area and floor area, prescribing a minimum free space (the geometric open area of ventilation openings) required for compliance. We understand that sometimes a ‘Simplified Method’ calculation of glazing area in relation to the floor area is not enough to assess the risk of Overheating. That’s why Approved Document O prescribes more complex Dynamic Thermal Modelling – so you can have peace of mind that your home is safe from overheating risks.

Designs may require adjustment to:

  • Glazing and ventilation size
  • Shading by way of:
    – External shutters with means of ventilation
    – Glazing with a maximum g-value of 0.4 and a minimum light transmittance of 0.7
    – Overhangs on south-facing façades

We are here to provide you with knowledgeable advice on this subject, and help you make an informed decision.

What is Dynamic Thermal Modelling CIBSE TM59?

It’s possible to use dynamic thermal modelling for a more in-depth simulation, as per CIBSE TM59 standards. This could be especially beneficial for cities with an increased risk of overheating due to the urban heat island effect – like London – where local councils commonly request this kind of assessment during the planning process. Our team of experts is well-versed on how to best employ this methodology and can guide you through the process.

When assessing property, there are certain criteria that must be met in order to ensure natural ventilation.

If your home is predominantly naturally ventilated, your living room, kitchen and bedroom temperatures should not exceed 1°C over the desired level more than 3% of the time. Additionally, bedrooms must remain below 26°C during sleeping hours (10pm-7am) for no more than 1% of the year.
On the other hand, if you have a mechanically ventilated home, all rooms should stay at or under 26°C for less than 3% of annual occupied hours. For further guidance on how to calculate this accurately and ensure conformity across different areas, refer to TM59 for standardised details.

Criteria for homes predominantly mechanically ventilated

For the comfort of all occupants, we ensure that individual rooms should not remain above 26°C for more than 3% of the year. To provide consistent overheating calculations across different areas, TM59 provides standardised details for factors such as occupancy and equipment heat gains and lighting. To get even more design flexibility over simplified methods, we suggest using dynamic simulation software to calculate temperatures and provide more flexibility with compliance.

Frequently Asked Questions

How do I comply with Part O building regulations?

To comply with Part O building regulations in the UK, you need to ensure that your building meets the requirements related to resistance to the spread of fire. Here are some key steps to comply with Part O:

1. Use fire-resistant materials: Make sure that the materials used in the construction of the building, such as walls, doors, and floors, have the required fire resistance rating.

2. Install fire protection measures: Include fire protection measures such as fire doors, fire-resistant glazing, and fire barriers to prevent the spread of fire.

3. Plan escape routes: Ensure that the building has adequate and safe escape routes, including stairways and exits that are easily accessible in case of a fire.

4. Provide fire detection and warning systems: Install fire alarms, smoke detectors, and emergency lighting systems to alert occupants in case of a fire.

5. Regular maintenance: Regularly inspect and maintain fire protection measures to ensure they remain effective and compliant with regulations.

6. Seek professional advice: Consult with a fire safety expert or building control officer to ensure that your building meets all the necessary requirements of Part O regulations.

By following these steps and ensuring that your building adheres to the guidelines set out in Part O of the building regulations, you can ensure the safety of occupants and minimise the risk of fire spread in your building.

Does Part O apply to extensions and conservatories?

Yes, Part O of the Building Regulations in the UK does apply to extensions and conservatories. Part O deals with the resistance to the passage of sound, ensuring that adequate measures are in place to minimize the transmission of noise between different parts of a building. This is important for maintaining a comfortable and peaceful indoor environment. When constructing an extension or conservatory, it is important to comply with the requirements of Part O to ensure that the sound insulation performance meets the necessary standards.

Where can I find detailed information on Approved Document O: Overheating?

Where can I find detailed information on Approved Document O: Overheating?
You can find detailed information on Approved Document O: Overheating on the official UK government website. The document provides guidance on preventing overheating in buildings and is part of the Building Regulations in England. You can access Approved Document O on the government’s Planning Portal website or by searching for it on the government’s official website.

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