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.
Did you know that we also offer a range of other services?
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!
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.
When did Part O come into force?
Part O Building Regulations have now been published and took effect 15th June 2022. Any development that was subject to a building notice, has made a full planning application or submitted an initial building notice before this date will not have to comply with the overheating regulations, providing the work is started on site prior to 15th June 2023.
It’s a good idea to take steps to minimise overheating in any construction project, regardless of whether the Building Regulations require it or not. Additionally, there may be other considerations like Planning Conditions related to excessive heat that must be met as well.
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?
When designing, there are two main approaches to meet the requirements of Part O. The first is a simplified approach that limits solar gains and makes the most of natural ventilation by tailoring window size and design. Alternatively, you could opt for dynamic thermal modelling based on CIBSE’s TM59 Design methodology which covers the assessment of potential overheating. Our team have an in-depth understanding of both routes so you can be confident in finding the best solution for your project.
The designers should also take into account any potential obstacles that would prevent the successful implementation of the simplified method. Examples include noisy or hazardous environments; restricted access to areas due to safety concerns, such as falling or entrapment; and pollution levels. If these challenges exist, alternative methods such as Dynamic Thermal Modelling must be used to ensure compliance with Part O regulations.
Does Part O apply to extensions and conservatories?
If your new home is being constructed, then you must adhere to the requirements of Part O. This also applies to any conservatories that are added onto a newly built residential property.
However, if you’re looking to extend or add a conservatory on an existing building, Part O does not apply. The same goes for buildings which are undergoing a change of use.
Where can I find detailed information on Approved Document O: Overheating?
Focus 360 Energy can provide expert advice on Approved Document O: Overheating. Our experienced team of professionals has extensive knowledge of the latest Building Regulations and Standards to ensure that you can remain informed and educated about your options. With our friendly, reliable service, you can rest assured that you are receiving the best possible advice tailored to your individual needs. Contact us today to discuss your specific requirements and arrange an online quote.
Further information can also be found at https://www.gov.uk/government/publications/overheating-approved-document-o
Where can I find detailed information on Approved Document O: Overheating?
Focus 360 Energy can provide expert advice on Approved Document O: Overheating. Our experienced team of professionals has extensive knowledge of the latest Building Regulations and Standards to ensure that you can remain informed and educated about your options. With our friendly, reliable service, you can rest assured that you are receiving the best possible advice tailored to your individual needs. Contact us today to discuss your specific requirements and arrange an online quote.
Further information can also be found at https://www.gov.uk/government/publications/overheating-approved-document-o
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