PassivHaus Building with SIPs – Structural Insulated Panels

MySipHouse

MySipHouse

Looks like our dream house may be an as-PassivHaus-as-possible extension of a traditional 3-bed semi. So now I’m looking at how we make that happen. One of the things I’ve come across are Structural Insulated Panels. Essentially these are a thick “sandwich”, with two wooden panels separated by a thick layer of insulating foam. One of their advantages is size – you can get panels up to about 6m long, factory-cut to your dimensions, with all the window and door holes pre-cut. And that means that you can have a very short on-site build time – some SIPs builders claim to be able to have the house built in under a week. It also means you have less joints to compromise your insulation and airtightness.

While they are not all natural – the core is plastic – they do have several real positives:

  • All the  offcuts can be recycled at the factory – no skip required!
  • They use up to 50% less raw timber than a timber-framed house
  • They can result in thinner insulated walls than other methods – 150mm vs 250mm for a cavity wall
  • A typical U Value would be .22 w/m2K – heading for PassivHaus standards

There are lots of considerations when using them though:

  • You need to do all your planning up-front.
  • Use an architect and builder with SIP experience or you’re in for a world of (expensive) pain  caused by last-minute changes.
  • Try to ensure as much of the electrical and plumbing work is done on the internal walls to reduce the impacts on the insulation
  • Ensure that the builders seal all joints correctly with insulating foam (urethane) 
  • You may need to use a vapour barrier to prevent condensation inside panel, which could lead to rot.

They certainly seem to tick a lot of our boxes – they’ll go on the list as a possible option.

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