The case for SIPs

Jim Nolan at hemsec Manufacturing discusses the case for adopting structural insulated panels (SIPs) to create more thermally-efficient superstructures in the housebuilding sector.

The superstructure of a building – the frame, or its load-bearing framework including walls, main floor and roof – is where the majority of heat loss occurs, and is the place where thermal efficiency starts.

While architects and builders are gradually adopting this ‘fabric first’ approach, it is hard to see why most industry players fail to use more energy-efficient building envelopes, particularly considering how they simplify construction. On a social level, homes with inefficient energy ratings are one of the key causes of fuel poverty in the UK, because of heat loss and the need to keep replacing it by paying for more fuel.

Fuel prices are rising, and everyone in the industry should be working to mitigate the effects, particularly those involved in building for low-income families, such as social housing and build-to-rent, where fuel demands a greater proportion of lower incomes.

With COP26 came an even greater awareness of the urgent need to control the rise in the earth’s temperature. A thermally-efficient superstructure is a major step towards decarbonisation, along with the ban on the installation of gas boilers in newbuild properties from 2025, for which a thermally-efficient envelope is ideal, because it obviates the need for this kind of heating.

Well before COP26, the UK government had already announced its 2025 introduction of the Future Homes Standard: changes to Parts L and F of the building regulations for new dwellings, which will require the industry to uplift the energy efficiency of new homes. These standards can be difficult to meet using traditional methods of construction, so it’s a good idea for architects and builders to start the change process now.

One of the most cost-effective and thermally-efficient superstructures is created by using high-quality SIPs. Manufactured offsite, SIPs are thin but thermally efficient insulated panels. High quality, well-engineered SIPs of appropriate thickness, when used correctly for walls, floors and roofs, create airtight building envelopes that can deliver U values well below the current building regulation requirements. In addition, thermal conductivity in SIPs is 0.028 λ D (W/mK) for the foam core thickness greater or equal to 120mm, and panel joint air-tightness equals 0.01 m3/m2/hr at 50 Pa when tested to EN 12114 in accordance with BS EN 14509:2013.

Many of the best-engineered SIPs can ‘exceed’ the Passivhaus standard when other energy-saving methods are adopted, such as solar panels, MHVR systems and storage batteries.

While thermal efficiency is one of the most important benefits that SIPs bring to construction, there are a number of further, highly significant benefits.

Improving quality  

Poor housing is costing the NHS in England £1.4bn a year, according to a report produced by the Building Research Establishment and highlighted by ITV News correspondent Dan Hewitt. While there are many factors which influence quality throughout a house, having a simple SIP superstructure gives major benefits:

Industrially manufactured, SIPs are not subject to the inconsistencies of man-made construction such as hand-built, hand-rendered walls, therefore the results are straighter and flatter walls.

There is less to go wrong with reduced requirements for onsite adjustments with fewer components; often ‘Data Sheets v. Actual’ as well as the inevitable user error, mean considerable additional work onsite. However, with precision-engineered SIPs from a reputable manufacturer delivered to site, what you order is what you receive. 

High quality SIPs are very strong load-bearers, and come in a variety of thicknesses depending upon whether they are being used for the walls, floors or roof. As well as having insulation built-in, even the thickest SIP is very narrow. This gives a significant amount of additional space, particularly in a property with a small footprint.

The strength of a SIP means that roof spans can be much larger than in a traditionally built property, allowing for additional living space and light.

A further benefit is that many SIPs have been fire tested to BS476-21 and can achieve a fire resistance of FR60 in a full build up. Hemsec SIPs also hold LPS 1208.

SIPs create an extremely tough, durable barrier, and a property built with a SIPs envelope is capable of resisting extreme weather. For example, in Kobe, Japan in 1993, an earthquake devastated a large area of the city, but houses built with SIPs came through it virtually unscathed. 

Further Benefits  

Positively, architects and construction workers are learning to design and build with SIPs, and are becoming increasingly skilled and creative in their use. 

For the developer, the envelope is much quicker to install than the majority of other building methods, which means faster builds with fewer unforeseen delay costs and therefore a faster return on investment. For the builder, the speed of construction saves time, money and the need for highly paid skilled labour. With fewer components to cost, order and work with, there is less management and less to go wrong.

With so much positive change being driven in the construction industry, the pressure to attain a variety of new standards is getting stronger. SIPs are tried and tested, and are one of the best ways for the industry to meet this challenge.

Jim Nolan is operations director at Hemsec Manufacturing