A Guide on How to Insulate Under a Suspended Timber Floor
A guide offering the best practice advice for insulating under a suspended timber floor
Knowledge Article5 min read
Having identified a need for affordable housing within the local area, Sharbrook Parish Council commissioned Hastoe Housing Association to carry out a detailed survey and identify opportunities for a new estate.
Together with Parrott Construction and DP Architects, they developed the Lower Furlong estate to provide four homes for affordable rent along with a further five shared ownership dwellings and four houses for general sale. In addition to creating attractive properties which sit naturally within the rural setting, the project team were also determined to minimise heating bills for owners by constructing the two storey properties to the Passivhaus energy efficiency standard.
LOCATIONBedfordshire, UK
ArchitectDP Architects
The standard sets clear energy performance and space heating targets which must be met post-construction for properties to be certified. Homes must be highly insulated, airtight and virtually thermal bridge free.
In order to meet these requirements, a number of our insulation solutions were installed within the homes.
To insulate the beam and block floor construction of several of the homes, a 225 mm layer of Kooltherm K103 was installed. The underfloor insulation boards provide outstanding performance. This allowed the project team to reach a ground floor U-value of just 0.08 W/m2K on these properties whilst limiting the depth of groundworks.
TEK SIPs were used to form the external walls of the properties and were fabricated and installed by Kingspan Timber Solutions (KTS). The panels feature a high-performance insulation core bonded between two layers of OSB/3. Their proprietary jointing system helps to limit air-leakage whilst maintaining insulation continuity throughout the building envelope.
Once the designs were agreed for the homes, KTS cut the panels to the project dimensions including precisely measured entrances for the triple-glaze windows and doors. This accurate offsite manufacturing process limited the need for onsite adjustments and supported accurate detailing around openings to minimise thermal bridging. It also allowed the external walls to be rapidly erected with a small team of site operatives.
An airtight barrier was fitted on the internal face of the panels and airtight tape was applied to all junctions. By paying close attention to these details, the project team were able to keep air-leakage from all completed properties below the Passivhaus limit of 0.6 ACH @ 50 Pa. Mechanical ventilation heat recovery (MVHR) systems were installed in all of the properties to maintain a steady flow of fresh air within the homes. These systems use the heat from exhaust air to warm incoming fresh air – further limiting heating demand.
Page Reviewed 28/07/25
