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So you’ve decided to build your extension or house incorporating a beautiful bespoke green oak frame which features lots of traditional carpentry, exposed timbers and soaring trusses, but just as important will be how you decide to insulate and clad the structure.

Historically oak frames were exposed externally and internally with lime rendered infill panels of wattle and daub. This system can still be achieved but there has been a move away from such methods for two important reasons: firstly it is becoming more and more difficult to meet exacting energy efficiency requirements for providing well insulated and airtight homes when the oak structure cuts through  the insulated envelope creating a whacking great “cold bridge”, and secondly, dealing with the natural shrinkage of green oak makes it almost impossible to prevent an infill panel system from leaking (air and water!)

So what’s the alternative?……SIPs (Structural Insulated Panels)

What are SIPs?

SIPs are a sandwich comprising 2 layers of structural board bonded to an insulated core. The structural board is made of OSB (Oriented Strand Board) and the insulated core is either expanded polystyrene or rigid urethane.

More and more projects are choosing to sacrifice the external aesthetics of the oak frame in favour of an insulated envelope made from Structural Insulated Panels which wraps around the oak frame. Such a construction method has so many benefits, it’s hard to know where to start

  • A continuous insulated shell can provide mind boggling energy efficiency with low u-values and high air tightness
  • Low heating requirements are a consequence of such high energy  performance , often requiring underfloor heating on the ground floor only and MVHR (Mechanical Ventilation and Heat Recovery) upstairs. These systems work well with ground source and air source heat pumps
  • The oak frame can be seen in it’s entirety inside the building, and is no longer partially lost within the wall buildup
  • The separation of the structure and the envelope allows the green oak frame to dry out and shrink without any adverse impact
  • Offsite cutting and fabrication of the SIPS takes place in a controlled factory environment which reduces unnecessary waste
  • Fitting a SIPS wrap to an oak frame can take as little as a week, and so it is quite possible to have an entirely insulated and weather tight shell within two weeks
  • SIPs can accept any external cladding – weather boarding, render, stone or brick. An internal service void is created at the design stage for electrics and plumbing
  • External door and window openings are precut in the factory. Fitting windows and doors into the envelope makes so much more sense than fitting between an oak frame that is liable to move as it dries out over time
  • Shorter build time and less dependence on favourable weather
  • SIPs are 7 times stronger than standard timber frame and nearly twice as strong as masonry

What SIPs options are available?

We work closely with our SIPs partners to coordinate the panel design and the oak frame to ensure that the dry shell and the frame fit. Manufacturing is also synchronised so that the SIPs shell erection can proceed as soon as the oak frame has been raised.

We have two SIPs companies who we work with and can thoroughly recommend:

Just down the road from us in Hereford, Glosford Timber Solutions are delivery partners for market leaders Kingspan Tek SIPs. Kingspan (again another local company) have been making their own 144mm rigid urethane sip panels for many years, and have recently developed a thicker 172mm panel  giving u – values of 0.14

Do you want a quick quote?
Or to discuss your project?

If you're considering an oak framed building (or larch, or douglas fir), let's talk. We'll gladly put together an outline quote (completely free, with no strings attached). And we need very little information from you to do so.
Equally, we're always here, at the end of the phone, to talk through your ideas. 01547 560 231
Castlering Wood, Beggars Bush, Evenjobb, Powys, LD8 2PB