The game has changed

Posted on December 1st 2015

by Phil Slater

We’ve seen a gradual change in Scotland from traditional block building towards timber frame structures, the problem is that timber frame is struggling to reach the new building code, needing ever thicker walls to integrate the required insulation.

Structurally Insulated Panels (SIPs) have been around for decades and have acquired a growing following due to the ease of build and rapid deployment characteristics. However there have been problems, standard SIP panels use Orientated Strand Board (OSB) on the outer skin with a layer of insulation between. In some cases these are glued together causing some de-lamination problems and OSB is effected by water and needs membranes or treatments to make the panel fireproof. Joining the panels is usually left to on site contractors with mixed results, these problems effect the thermal envelope of the structure and need expensive membranes fitted on site to ensure the airtightness now demanded by Building Control.

The principle of SIPs panels should have been a revolution in building, however this has been let down by the execution of current systems. Enter a new generation build system that addresses all of the problems of standard OSB panels and sets a new benchmark for ease of build, rapid deployment, thermal performance and airtightness.

Magnesium Oxide (MgO) faced SIPs panels. MgO is highly water resistant and fireproof. The common use for MgO is in firebricks for smelters and chimneys. It’s been around for a very long time, for example, all of the mortar in the Great Wall of China is MgO based!

MgO panels are formed in a press and the bond between the panel and the insulation is chemical so there can be no de-lamination issues. BASF closed cell foam is injected and heat treated to form a very strong structural panel. The closed cell foam is water and air tight, essentially the panel does not breathe, this eliminates the need for any membranes to complete a fully water and airtight build.

Having addressed the issues of OSB based panels the next critical consideration is joining them together. To date this has either been left to on site trades or simple timber splines have been supplied. The key issues here are thermal bridging, air tightness and waste. Off site manufacture is the key, manufacturing components that only need assembly on site will eliminate waste and ensure an airtight fit. Fully engineered components have all but eliminated thermal bridging, which along with the airtight characteristics means that building to Passivhaus standard is easily achievable.

The case is clear for SIPs panels, rapidity of construction, thermal performance and preservation of internal spaces. A 150mm panel gives a U-value of 0.20, whilst a 250mm panel U-value is 0.12, far exceeding the current building codes.

With the ability to batten directly onto the system for roofing or cladding or render directly onto the outer surface the benefits of MgO are clear. Using the this type of system for internal walls (down to 100mm thick) means that kitchen units or shelving can be hung directly onto walls, tape, fill and skim to finish. Acoustic performance far exceeds any stud wall and the system is flexible enough to accommodate most designs.

…The revolution is here.