SIPs - the future in MMC

Edited by the Buildingtalk editorial team Jul 3, 2008

Jim Caldwell, Technical Services Manager at Norbord explains why Structural Insulated Panels are increasing in popularity in the UK.

If you haven't heard of SIPs before, you're sure to hear a lot more about them in future.

SIPs stands for Structural Insulated Panels, a type of modern building component which is rapidly increasing in popularity in the UK.

A typical SIP panel comprises a layer of closed-cell CFC-free polyurethane foam sandwiched between two facing boards of oriented-strand board (OSB).

OSB is a wood-based board comprising of softwood strands bonded together under pressure with thermal cure resin.

In the UK, the majority of SIPs panels are made using Norbord's Sterling OSB3, the leading moisture-resistant OSB product.

The combination of two OSB boards bonded either side of a foam core creates a very lightweight, rigid panel with excellent load bearing characteristics.

As a leading producer of OSB worldwide, Norbord has worked closely with manufacturers in the development of SIPs.

SIPs were developed in the US more than 50 years ago and are now an established method of house construction there.

However, modern SIPs technology was only introduced into the UK during the 1970s and is still regarded, in some quarters, as a novel method of construction.

SIPs comprise one of the so-called 'Modern Methods of Construction' (MMCs) which are currently promoted by Government to improve construction efficiency and reduce energy wastage in new buildings.

Because SIPs panels are load-bearing building components, no separate structural frame is needed.

SIPs can be used to construct the floor, walls and roof of a building, allowing uniform detailing at interfaces to provide continuity of insulation and minimal air leakage.

OSB - already a major component of mainstream timber frame construction - is the ideal board product for the manufacture of SIPs.

Not only does it fulfil the physical requirements in terms of strength and rigidity, it also contributes to the panel's environmental benefits.

Sterling OSB is a sustainable product made from timber grown in Scottish forests mostly within a 60 miles radius of the Inverness mill.

Because the board is made from softwood strands (typically 120mm long and 25mm wide), forest 'thinnings' are the ideal raw material; these are the smaller trees which are harvested early to allow space in which the larger specimens can mature.

The cross orientation of fibres in a sheet of OSB results in a panel with excellent bending performance suitable for structural uses.

And although costing significantly less than comparable plywood sheets (which must be made with premium quality logs), OSB is just as strong and no less durable.

Compared to the US, and even mainland Europe, the UK was late in adopting the use of SIPs.

However, the current drive to lower building costs and conserve energy is helping SIPs penetrate the market.

Last year, analyst AMA Research estimated the value of the UK market for off-site manufactured buildings at around GBP490 million.

And, while timber frame takes roughly 45 % of the MMC market by value, SIPs now accounts for 10 % and is among the fastest-growing new building methods on the market.