Summary
¦ A two-storey extension is being built at a Bicester church.
¦ It is iFrame’s first Passivhaus project.
¦ iFrame comprises storey-height panels using Masonite engineered timber studs.
¦ U-values of 0.10W/m²K for walls are targeted.

Code 4 Roof & Timber Frame Ltd has high ambitions for the 7,000ft² two-storey timber frame extension it’s building at a Bicester church.

The project involves the construction of a new parish centre facility at the Catholic Church of the Immaculate Conception and the extension, which will be attached to the north-west end of the church, will consist of a function/meeting room as well as reception, kitchen, storage, administration areas and a lift.

The aim is for Passivhaus certification, and Code 4 Roof & Timber Frame is using the iFrame small panel wall system, featuring Masonite I-beams, to help it achieve this.

By using iFrame the company, which is subcontracted to developer Ardent Contractors Ltd, is hoping to achieve U-values of 0.10W/m²K for walls and 0.09 W/m²K for the roof. In addition, it has the target of achieving the stringent Passivhaus airtightness requirement of 0.6 air changes per hour – ie the building must not leak more air than 0.6 times its volume per hour at 50 pascals. This level of airtightness is well over 10 times better than that of the current regulatory requirement.

According to Nick Jones of Inbuilt Ltd, Passivhaus expert and certifier for the scheme, the company is on track to achieve its targets.

“The team quickly grasped the stringent demands Passivhaus put on the system and responded with a very considerate and thoughtful approach to predicted high levels of airtightness,” he said. “Plus the flexibility shown with regards to achieving required U-values was excellent.”

Flexible build system

iFrame is designed as a flexible build system which can be adapted on site. It takes Masonite Beams’ standard engineered timber studs and uses them as storey-height panels.

These specialist panels, along with the integrating service panels made specifically for the system, are delivered to site as components. They are assembled with their web members in the same plane as the run of the wall elevation, thereby forming the desired wall in situ.

The secondary vertical/horizontal service panels overlap the insulated spaces between each storey-height panel and are the subject of a patent application.

This panelised wall elevation assembly allows for greater design flexibility because gaps for windows and doors can be repositioned during the build process.

Insulation

Multiple leaf wall assembly includes layers of identical depth insulation in sets of standard widths and depths.

A secondary internal panel assembly includes upper and lower horizontal service/bridging panels with vertical service/bridging panels in between. This is designed to provide adjustable wall elevations, greater racking performance (compared with standard timber frame) and facilitates isolation of services in relation to the vapour control layer and optimised service routes.

Unlike with traditional timber frame, no expensive crane was required at the Bicester Church site, since the wall components are offloaded from a delivery vehicle using a fork lift. Components for the whole timber wall assembly can be loaded onto one vehicle, even for large construction sites.

Keeping delivery costs down and reducing the carbon footprint of the builder will become increasingly important in the construction trade.