When insulating a property, it is important to limit the number and size of any breaks in the insulation layer. If not properly treated, these areas can act as thermal bridges, providing a path for heat to bypass the insulation and escape out of the building. At the same time, there are cases where penetrations through the insulation are unavoidable. These include where downlights or spotlights are fitted in an insulated ceiling / roof space and where pipework or flues need to be installed.
To limit the risk of thermal bridges, it is important to carefully plan any penetrations before you start so you are only making as many as are necessary. Each penetration should be cut to the specific size required and fully sealed up once work has been completed.
There are best practice details available which can be followed to effectively insulate around building services, limiting the risk of condensation or additional heat losses. The specific approach will depend on the type of pipe or flue that is being installed, and the requirements and tools needed may differ for each.
In this article, we discuss how to achieve good results when making penetrations through insulation for pipework and flues.
How to run gas or oil pipes through insulation
When running a gas or oil pipe through a wall, you should use a pad saw or core drill (a circular disc drill bit) to cut through the insulation to provide a snug fit and reduce the oversize to a bare minimum. Any damage to the insulation should be made good by filling any large gaps (10 mm +) with expanding foam insulation and the pipe perimeter should be sealed with flexible sealant.
How to run a flue pipe through insulation
For flue pipes there may be a requirement to create a separation layer between the insulation and the flue pipe. This will vary depending on the operating temperature of the flue and the flue specification itself. This needs to be checked before installation. In all cases, the installation of gas, oil pipes, flues, electrics and telecoms should only be done by a competent person such as a qualified electrician, Gas Safe, OFTEC, HETAS or BT certified engineer. It is also vital that ventilation requirements for certain combustion appliances are not removed, blocked or reduced in size. All works involving appliances, fittings or flues should be carried out in accordance with Approved Document J for England & Wales, or Section 3.17 – 3.24 of the Scottish Technical Standards and / or manufacturer’s guidance.
The diagram below shows best practice of a flue installed in a wall insulated with Kooltherm K118 Insulated Plasterboard.
For more information on insulated plasterboard, download the Kooltherm K118 Insulated Plasterboard brochure.
