JJI-Joists - Build It Green

38 WALL DESIGN
INTRODUCTION
JJI-Joists are ideally suited for use as wall studs where their
availability in depths up to 450mm allows designers to insulate
external walls to unprecedented levels. Even when shallower
joists are used the narrow web profile provides a restricted path
to heat transfer (reduced repeated thermal bridging) when
compared with solid timber.
DESIGN CONSIDERATIONS
Where the wall is subjected only to horizontal wind loads with
no vertical axial loads (e.g. ground level to eaves level infill
panels in a portal frame structure) JJI-Joists allow very tall walls
to be built using a continuous structural member.
James Jones & Sons recommend that JJI-Joists are incorporated
into prefabricated wall panels in order to take advantage of the
improved precision and quality typically available in a factory
environment.
For further information on axial compression strengths please
contact James Jones & Sons.
Each timber frame kit manufacturer will typically produce their
own set of standard details to suit their specific production,
manufacturing and technical requirements.
The structural design of JJI-Joist studs should be undertaken by
a suitably qualified Engineer who should pay particular attention
to buckling restraint, axial load distribution between inner and
outer flanges and member to member fixings.
It is our recommendation that the use of JJI-Joist studs is
best suited to external wall closed panel type manufacturing
with a separate service zone on the inside face of the internal
sheathing. It is beneficial to manufacture long panels due to
the JJI-Joists being lightweight and particular care should be
taken when insulating to avoid cold spots.