1 item tagged "Over Glazed Extensions"

  • Over Glazed Extensions

    Over Glazed Extensions Part L Calculations

    If you are planning to add an extension to your property and intend to add a lot of glazing such as an orangery that is open to the rest of the house then the chances are building control will ask for a SAP Calculation to show that the additional CO2 emissions from the home will be within Government allowances.

    If you intend to have a straight through entrance to the extension and if the extension has glazing over 25% of the extension floor area you will need to provide calculations to building control when applying for planning permission.

    In order to carry out the calculations we will require a full set of plans, ideally the plans should show the whole house as well as the extension, this is in case the extension is failing to meet the criteria on its own and we have to look for ways to cost effectively improve the main house in order to offset to extra CO2 that the extension will produce in use. This may be something like adding extra loft insulation or improving the rating of the boiler, there are several options we can look at to help the extension pass part L1b.

    In general we can get most extensions to pass or exceed the required criteria, in order to help get the pass we recommend looking into the following cost effective measures:

    • Buy the best insulation for the extension - buy buying the best you can improve the thermal conductivity of the main wall, roof and floor, because extensions are not usually huge the extra cost is negligible for the benefits in fabric improvement, also don't forget, you will have to pay to heat the extension, so the savings over the years soon mount up, the better the insulation, the less heat loss through the fabric
    • Buy the best thermal block for the walls - again because the extension will use only a small amount of internal block work the cost is not large compared to the short and long term benefits.
    • Buy the best glazing - glazing is the week point in any construction project, weak in terms of heat loss, there are glazing units available that provide excellent thermal properties, and again will pay for themselves over time by reducing heat loss, and the word "loss" is the keyword, by reducing heat loss you save the energy and heat that you have paid for, and keep it in your home as long as you can before it finally escapes.

    These are just a few of the things to bear in mind for your project, although the cost of materials may be higher, the benefits are equally as high, don't waste your hard earned money by building an extension to a home you will live in by buying the cheapest possible materials, it really is a false economy.

    If you are not sure of the materials and insulation types you should be using let us know, and we can include some recommendations in our report, and provide U-Value calculations to show the improvements over Part L1b for planning and building control.

    Why not request a quote for your project today:

    In order for use to provide an accurate fee quotation please send the following information to This email address is being protected from spambots. You need JavaScript enabled to view it.  

    • Full set of plans (including main house)
    • Details on the materials and insulation you would like to use

    That's pretty much it, once we have the information we can provide the fee quotation within 24 hours, and should our quote be successful we can provide the finished calculations within 48 working hours. Thanks for reading this and we look forward to being of service to you in the near future.

    We also provide the following fully accredited services:


    • SAP Calculations for new build homes
    • SAP Calculations for conversion of use to a dwelling
    • Sustainability statements for planning
    • Energy statements for planning
    • Potable Water PART G Calculations
    • Surface Water Run-Off Calculations
    • SUD's reports
    • Air Tightness testing
    • Contaminated Land Studies
    • Invasive plant remediation

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