Understanding Insulation and the Part It Plays in Building Regulations

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The building regulations Part L sets out clear guidelines for how to make a new property more energy efficient and this is measured with a new Target Emissions Rate or TER. This is based on elements such as insulation as well as heating, lighting, building materials and windows on the property.

At the design stage, the TER is calculated and approved by the local building control department. It is calculated with a system known as Standard Assessment Procedure or SAP and there are computer programs that run this. The procedure lays down rules such as the specific U-values of the elements used in the house but this can make understanding insulation a little complicated.

Anywhere from 25-33% of heat lost in the building goes out through the roof. But it is also the easiest area to insulate and there are a number of different options to use. Mineral wool or glass fibre are the most cost effective options, and are available in soft slabs sandwiched between plastic sheets to make for ease of handling. It is also easy to cut with scissors and makes for a quick insulating method. It can also be used to insulate water tanks while pipes around the tank should be insulated with foam tubing.

Cavity walls were invented back in the 1920s and involve leaving a gap of 50-100mm between the layers of externals walls. This adds to the weather resistance of the property and the gap can be filled with insulation to prevent heat escaping. However, solid walls are a re-emerging idea that can be used in new build properties and can be even more insulating than cavity walls. Weatherproof cladding can be used that can knock as much as 25% from heating bills although it is quite expensive to install in the first place.

If you are using wooden floors in your property, then you can lay mineral wool insulation under the boards using a netting system. To get a U-value of 0.22 you will need to use around 150mm worth of wool, which can save around £40-50 a year on heating costs. It is important to leave underfloor airbricks to get plenty of airflow.

Whatever method of insulation you use or if you decide to add all of them to achieve the maximum energy efficiency, ensure you include the details in your designs as a part of your building regulations submission.