impact of glazing on SAP assessment
Latest entries from the Blog:
- BREEAM Very Good for development in London Borough of Southwark, SE5
- Energy Strategy for a 27 unit change of use in Lewisham
- Energy Strategy Statement for 59 dwellings in Slough
- 50 unit new housing project in Harwich
- BREEAM Very Good and supporting expertise in Ealing, W5
- Carbon Life Cycle Analysis for London Borough of Richmond-upon-Thames
- New building to meet code level 3 in Wandsworth
- Successful planning permission for Orangery in Buckingham
- Planning challenges in Kensington & Chelsea
- Planning permission for glazed extension in Tring
- Local Authority regulations met for new Conservatory in Aylesbury
- Dynamic Energy Assessors provide multiple SAP calculations for client near Redhill
In this article I intend to deal with the three parameters commonly effecting adverse SAP assessments. This is not intended to be a definitive statement on glazing for that view SAP 2009 – Th Government’s SAP for Energy Rating of Dwellings
The three parameters are:
- U Value of entire window
- ‘G factor’ of the glass
- Summer overheating and the air flow rate
The U Value of the entire window is important to the efficiency of the building especially if the building is to have a large amount of glass however; the better the U Value the higher the cost. The openings in the building must not have a U Value greater than 2.0 (bear in mind an average door has a U Value of around 3.0)
The amount of heat the glazing lets into the dwelling, the G Factor, is dependent upon the coating put on the glass. The lower the G Factor, the better the glass is a resisting heat transfer, but the higher the energy used to heat the dwelling.
If the G Factor is to high the dwelling will fail due to summer over heating and if it is to low the amount of energy required to heat the building will be to large causing a DER/TER failure
Should there be a requirement to use renewable sources to provide say 15% of energy then the lower the G Factor, the lower energy requirement and therefore the lower the renewables required
If you require assistance on exactly how to balance these factors contact us
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