STRUCTURAL INSULATED PANELS

Structural insulated panels (SIP’s) are smart, next generation combined boards made of insulating foam core (PIR or EPS70) sandwiched between 9mm Oriented Strand Board (OSB3) or 6mm Plywood skins used for framing requirements, building partitions, shops, office fit-outs, self builds, flooring, garden rooms and roofs. They come as prefabricated boards that can simply be slotted together, to create the entire structure of your new home. They have only become popular in the UK in the last 8 years, however, panels have been used across the US for around 35-45 years. In fact SIP panels are made in the UK and their cost is much cheaper than you might think. There is less need for additional structure and beams when using this material. Average cost of 112mm 8'x 4' block as of 2023 is £159.71 which results in £55.45 per m2. The composite nature of the foam core and outer OSB or PLYWOOD means that they are more rigid than each of these elements on their own. It is considered to be up to 5 times stronger than a simple timber frame. If you consider the fact that in normal circumstances you would have to build a brick wall or stud wall, then plaster the wall later, SIP boards work out a lot cheaper. SIP’s use less timber than timber frame and are one of the most economical and eco friendly forms of construction. Due to the nature of how they’re created SIP’s are extremely easy to connect together as part of your build, meaning that the average project is completed in a shorter space of time. SIP’s, through their strength and ease of connection, offer the designer more versatility than other construction materials. Building with SIP’s will save you time, money and labour. To put it into perspective, a wall project which would usually take a couple of days can be completed in hours with SIP’s. Buildings built with SIP panels are generally more energy efficient, stronger, quieter and more airtight than older technologies.

SIP DETAIL

SIP boards are usually 4 feet wide and 8 feet long, however they can vary in height. Taller boards can be used for quicker and more seamless installation on higher walls. The thinnest boards are 27mm and the thickest are 183mm. Structural insulated blocks come as a square edge or grooved edge with a jointing element. SIP boards can be used in a wide variety of applications such as garage, museums and galleries, receptions, airports, residential dwellings or commercial buildings. 

TYPES OF SIP PANELS

There are 2 types of SIPs panels. Both use two OSB3 boards or PLYWOOD, but one sandwiches polystyrene board between them while the other has urethane pumped inside. This combination product offers either PIR (PolyIsocyanuRate) core or EPS (Expanded PolyStyrene) core. Depending on the design, you can choose from various types of layer setups. Boards may come as a single sided board (OSB3 or PLYWOOD) or double sided panel (OSB3 or PLYWOOD). SIP panels can also be manufactured using other sheet materials such as Cement Particle Board (CPB). Other sheathing materials include gypsum sheathing, sheet metal, fiber-cement siding, magnesium-oxide board and composite struc­tur­al siding panels. The thickness of SIP panels used will depend on the build-up of the wall and u-value which is being targeted. All of them are available in a variety of  thicknesses: 

SINGLE SIDED EPS CORE SIP's

EPS + 6mm PLYWOOD - 31mm ǀ 36mm ǀ 46mm ǀ 56mm ǀ 81mm ǀ 106mm
EPS + 9mm OSB3 - 34mm ǀ 39mm ǀ 49mm ǀ 59mm ǀ 84mm ǀ 109mm

SINGLE SIDED PIR CORE SIP's

PIR + 6mm PLYWOOD - 21mm ǀ 26mm ǀ 31mm ǀ 36mm ǀ 41mm ǀ 46mm ǀ 51mm ǀ 56mm ǀ 66mm ǀ 71mm ǀ 76mm ǀ 81mm ǀ 86mm ǀ 96mm ǀ 106mm ǀ 116mm ǀ 126mm ǀ 136mm ǀ 146mm ǀ 156mm ǀ 171mm ǀ
PIR + 9mm OSB3 - 24mm ǀ 29mm ǀ 34mm ǀ 38mm ǀ 44mm ǀ 49mm ǀ 54mm ǀ 59mm ǀ 69mm ǀ 74mm ǀ 79mm ǀ 84mm ǀ 89mm ǀ 99mm ǀ 109mm ǀ 119mm ǀ 129mm ǀ 139mm ǀ 149mm ǀ 159mm ǀ 174mm

DOUBLE SIDED EPS CORE SIP's

9mm OSB3 + EPS + 9mm OSB3 - 43mm ǀ 48mm ǀ 58mm ǀ 68mm ǀ 93mm ǀ 118mm
6mm PLYWOOD + EPS + 6mm PLYWOOD - 27mm ǀ 32mm ǀ 42mm ǀ 47mm ǀ 52mm ǀ 57mm ǀ 62mm ǀ 67mm ǀ 72mm ǀ 77mm ǀ 82mm ǀ 87mm ǀ 92mm ǀ 102mm ǀ 112mm ǀ 122mm ǀ 132mm ǀ 142mm ǀ 152mm ǀ 162mm ǀ 177mm 

DOUBLE SIDED PIR CORE SIP's

9mm OSB3 + PIR + 9mm OSB3 - 33mm ǀ 38mm ǀ 43mm ǀ 48mm ǀ 53mm ǀ 58mm ǀ 63mm ǀ 68mm ǀ 73mm ǀ 78mm ǀ 83mm ǀ 88mm ǀ 93mm ǀ 98mm ǀ 108mm ǀ 118mm ǀ 128mm ǀ 138mm ǀ 148mm ǀ 158mm ǀ 168mm ǀ 183mm ǀ
6mm PLYWOOD + PIR + 6mm PLYWOOD - 27mm ǀ 32mm ǀ 37mm ǀ 42mm ǀ 47mm ǀ 52mm ǀ 57mm ǀ 62mm ǀ 67mm ǀ 72mm ǀ 77mm ǀ 82mm ǀ 87mm ǀ 92mm ǀ 102mm ǀ 112mm ǀ 122mm ǀ 132mm ǀ 142mm ǀ 152mm ǀ 162mm ǀ 177mm 

There are 2 main techniques of fixing SIP panels together. First one is the standard ‘butt’ method. This technique requires square edge SIP panels and top and bottom beams. Sheet stays originally flat. Other techniques called 'grooved' require nothing but jointing strips. There are small holes left after this installation between board and jointing strip.

STRUCTURAL INSULATED PANELS COST

The amount of money you spend on SIP boards can vary greatly depending on its core, so it's important to know what you're getting before you buy. For sure, EPS core is a cost-effective building material that will pay for itself over time. However, PIR core SIP boards seem to be a better solution, enabling greater savings and better thermal insulation than standard polystyrene core. For instance, 100mm EPS bonded both sites to 6mm plywood cost  £92.80 per 8' x 4' board, while 100mm PIR core with the same configuration will cost as of 2023 £159.71. On the other hand 100mm EPS bonded to OSB3 cost £96.31 and PIR bonded to OSB3 cost £150.77. To sum all up, the average cost of a SIP panel is £133.45 m2. The ability to install SIP boards quickly as it’s a 3 in 1 solution is a huge advantage. If you are looking to build a wall with a 112mm or 118mm SIP panel, you should be looking for £45.13 per m2 and £129.03 per 2400mm x 1200mm sheet. 

ADVANTAGES AND DISADVANTAGES OF SIP (PROS AND CONS)

ADVANTAGES

• SIPs are made from foam, and, therefore, are not prone to infestation from pests.
• Panels can accommodate greater spans of walls than standard construction.
• Structural Insulated Panels can be manufactured off-site.

DISADVANTAGES

• SIP’s require additional ventilation.
• Finding professional builders with experience can be tricky.
• If boards become wet, they will start to degrade very quickly.
• Panels have a lifetime of around 60 years.

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