Heat Loss Calculator for Domestic Extensions
Approved Document L1B (2010 edition) relates to the conservation of fuel and power in existing dwellings. This includes guidance on the required thermal standards for elements forming the building fabric and the amount of glazing allowable in extensions. In order to prevent this simplified guidance from being too prescriptive, guidance is given as to how, for example, an increased area of glazing is permissible if this is offset by improved thermal standards for the building elements.
To aid architects, designers and owners in ensuring that their proposals will satisfy Building Regulations in this respect when designing extensions to dwellings, a heat loss calculator spreadsheet is available for free to download from this site. To view click here and follow the easy to understand instructions and the calculator will assist in giving you more design freedom. Please note, however, that you should ensure that insulation values must not be less than the threshold values and for more guidance on this reference should be made to the Approved Document which is available for free download from the Planning Portal website.