Conservation of Fuel & Power

At the time of writing Approved Document L of the Building Regulations for England came into force on the 6th of April 2014. Further revisions are planned for 2016 and 2019 implementing further reductions in energy use through improved insulation values, renewable energy sources and more efficient heating, lighting and ventilation services, culminating in all new buildings being “Zero Carbon” by 2019.


The Government’s aim is to similarly reduce energy use in existing buildings through the Building Regulations (Consequential Improvements) and initiatives such as “The Green Deal” for residential buildings.


For Wales and Scotland, similar requirements are contained in the local Regulations & Approval Guidance for the individual country. Building Regulations (Wales) and section 6 (Energy) of the Scottish Building Standards Agency’s Technical Handbooks.


The latest edition of the local Building Regulations should always be referred to.


Approved Document L (England & Wales) is divided into four separate parts dealing with the following.

  • Part L1A- New dwellings, Part L2A – New Buildings other than Dwellings. Parts 1A and 2A require C02 emissions targets to be met and there are also limited ‘U’ Value standards for various thermal elements of a building such as roofs, rooflights, ventilators, etc.
  • Part L1B – Existing Dwellings. Part L2B – Existing Buildings other than Dwellings. Parts 1B and 2B require specific ‘U’ values and minimum services performance to be achieved.

New Buildings

The Building Regulations require that all aspects of the construction are to be taken into account in the design process in assessing the potential overall carbon emissions of the building. Apart from the construction materials themselves it includes the design of the details, choice of heating system and its controls, type of lighting, etc. When constructing the building envelope, the major factors in meeting the requirements to limit energy losses will be the incorporation of insulation and the achievement of a level of air tightness.

Existing Buildings

For existing buildings, the regulations require that if any refurbishment works are being instigated the need to upgrade the thermal performance of the existing construction must be considered. Generally, if renovating a ‘thermal element’, a roof or wall for instance, there are certain specific ‘U’ Values that need to be met, usually by the provision of extra insulation.

The requirements are limited by a cost effectiveness factor, which would normally expect ‘pay back’ from the works within 15 years. They can also be limited by factors of technical feasibility. There are exemptions, for example some specific types of building uses are exempt, listed buildings may not need to meet the full requirements under certain circumstances. However ultimately this should be confirmed with the local building control body.


These are a complex set of regulations and reference to the actual document is recommended for each individual project as is the advice of a ‘competent person’ as outlined within the regulations themselves.



In all roofs heat will flow from the warm side to the cold side. In nearly all cases Building Regulations will require a certain level of resistance to this flow in order to conserve energy, limit heat loss and reduce carbon emissions.


Considerations in the design of a roof build-up;

  • Compatibility with other materials in the roof build-up, this is to avoid the risk of a reaction with the waterproofing membrane and other components, or the corrosion of metal items.
  • Compressive strength – In relation to traffic both in construction and in use.
  • ‘U’ Value requirement measured in W/m²K. 130mm Decotherm Insulation will achieve Part L (Control of Condensation in Buildings) minimum requirements of 0.18W/m²K onto new/existing structural deck surfaces where there is no insulation present both internally and externally. In refurbishment situations where a thermal upgrade is required and the existing build-up is to be considered, the existing insulation can be accommodated within the calculation allowing for a thinner insulation board within the new system, achieving the required ‘U’ Value.
  • Fire Resistance related to the application
  • Costs – Both of the materials and installation; Some products may require more materials and effort to install than others.
  • Moisture Resistance – products should be able to accept a degree of wetting during the installation process without deteriorating.


Decotherm® Insulation

Decotherm® is a high performance CFC/HCFC free, Polyisocyanurate (PIR) insulation with a glass fibre facing. It is available as flat board or tapered scheme for roofs that require improved falls to increase drainage efficiency. The Decotherm® board is bonded using Decostik® SP - a cold applied mid foaming single pack adhesive.


A wet lay glass fibre tissue faces both sides of the insulation board ensuring compatibility with other product used within the cold fusion bonded built-up roof system.


Mechanically fixed Systems – Decotherm Insualtion can also be mechanically fixed in areas where the wind loadings are high. Mechanical fixing of the boards is deemed to cause thermal bridging, to avoid this potential issue Sika Liquid Plastics employs the use of thermally broken fasteners negating the need for increased insulation thicknesses of around 10%.

Changes to Energy Efficiency Legislation: Payback Calculations

New Government legislation MEPS (Minimum Energy Performance Standards) are likely to come into play in 2018, forcing all building owners who let their properties to have an energy rating of E or above.


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