Are you knocking through to an existing conservatory? Building an extension with large levels of glazing? Then building control will require an “Excess Glazing Calculation” to justify the amount of glazing being proposed.

Building Regulations state extensions are only allowed 25% of the floor area to be glazed, this is due to glazing not being as thermally efficient as the rest of the envelope (floor, walls, roof) meaning the property may require more energy to heat and cool.

To justify the glazing, a calculation is performed to assess the design, offering potential solutions to upgrade the works to ensure your property is both efficient and comfortable to live in.

As fuel costs continue to soar, improving passive methods such as increasing insulation and window openings can mean properties are designed efficiently, requiring less power to heat them, whilst also ensuring they don’t suffer from overheating, which is a common problem with conservatories in the summer.

Through either an on-site inspection or desktop survey, we can assess your property as a whole, including the levels of insulation to your roof, walls & floor, and your current space and water heating systems & controls. We then model your property so that we can recommend potential improvements to the buildings’ fabric and systems, in an effort to improve the buildings’ efficiency, making it thermally more comfortable, and thereby lowering your energy bills.

Depending on the type of project and survey being performed, these recommendations are often shown within the EPC which is created following our SAP assessment, or through changes to your specification.

As of 15^th June 2022, “Approved Document – Overheating” (AD O) will come into effect where all the openings of the building are assessed to ensure that the property isn’t susceptible to overheating from excessive solar gains, and is adequately ventilated. We’re able to perform this assessment under the “Simplified Method” as stated within AD O, and this will be undertaken prior to the main SAP calculation/report to ensure the finalised openings are suitable for your project.

Though an overheating assessment can be used for extensions, they are currently only a requirement for new build projects.

To undertake the assessment we will require the dimensions and location of all the proposed openings (which can be provided either by plan and elevation drawings or a window schedule), and the opening angle of all windows.

Due to updated requirements with Security, AD O states that all ground floor and easily accessible bedrooms require fixed or lockable louvred shutters, grilles or railings, otherwise they are to be excluded from the assessment which may cause overheating issues within your dwelling.

The overheating assessment does not form part of the SAP assessment and is therefore provided at an additional charge when requested. This fee is assessed on a project-by-project basis due to the amount and type of glazing proposed. The fee will be highlighted separately within your new build SAP quote.

Overheating assessments are a building control requirement, not SAP, and therefore we can provide SAP assessments without an overheating assessment. Please see our FAQs for further information.

A Heat Loss Calculation is undertaken to assess the total heat loss of a dwelling so a heat pump (Air or Ground Source) can be installed having been sized adequately.

Heat pumps, unlike previous systems such as gas boilers, require a more accurate assessment to ensure they run efficiently and provide the COP that manufacturers advertise. The calculation will often be undertaken to size the system for both space and hot water heating, and provide both room-by-room assessments for heat emitter sizing, and a Noise Assessment to see if the system meets Permitted Development requirements.

Please see our FAQs for further information.