ANDY THOMSON   architect

Structural Insulated Panel & Finish Systems – (SIPFS)

  • Authorandyro
  • Date 10 November 2009
  • CategoryResearch


INNOVATION #1:. SIPFS: A Structural Insulated Panel and Finish System

consolidating primary structure, thermal envelope and finishing system in a durable, modular system that assembles rapidly and easily on-site


Above: The problem with expensive, conventional construction is the multiple layers of materials that are usually constructed on-site. Each layer of material represents a hidden layer of associated installation labour, shipping and handling costs that when taken together, can add as much as 50% of the project’s total costs. Image Courtesy of Griffner Enterprises.

PROBLEM: Conventional construction is often per- formed on-site where builders are at the mercy of the elements as well as light conditions, dirt and debris and often less than ideal tools and materials. While factories provide the solution to many of these problems by providing a fully equipped, dry and well lit space to perform work while eliminating waste, the problem remains that buildings do not transport well to their end destination. Typically, large modules or what we call ‘empty boxes’ are shipped down the highways at great expense, and because of their relatively large size, require to be craned in place. Eventually, when these modules are placed together, they require to have their seams detailed on the interior and exterior, and usually finish materials applied to both sides. This ‘prefabricated’ approach to construction is only cost-competitive on large, repetitive projects, such as worker housing, or motels. In the residential design sector, on-site construction is still more cost- effective.

We understand the advantages of the factory, from lower labour costs, to better quality control, but we do not believe it is smart or cost effective to transport ‘empty boxes’ or use cranes to assemble components that are ultimately unfinished.

Also, many of these factory methods for creating modular buildings are still using conventional construction technology, which consists of structural components (studs), insulation, air and weather barriers and finally interior and exterior finishes. Each layer of material adds a layer of labour cost, and ultimately, these multi-layered components, whether they ship as panels or complete modular units, are more expensive and complicated than they need to be. There is a technology called SIPS – or Structural Insulated Panels that integrate two of these required layers, namely structure and insulation – which for us is a step in the right direction, but one which must be taken further.

IDEA: Develop a SIPS product that takes advantage of the benefits of factory production, and can be shipped flat per conventional shipping means (shipping containers) to the end-destination for easy assembly, without requiring cranes, or exterior or interior seaming details or even interior or exterior finish applications. This SIPS product must be durable, thermally-efficient and be detailed in such a way that it looks great and assembles easily. These panels should be strong enough to perform as load-bearing roof and wall panels, and be robust enough to not degrade after prolonged exposure to the elements.

SOLUTION: There is a pre-existing SIPS technology used to build refrigerated storage buildings, called ‘Freezer Panel’, which is like a block of solid foam that is sandwiched between two layers of steel that serve as the interior and exterior finishes. However, freezer panels are designed primarily to keep the cold in, or the heat out, and as such they usually require what is called a ‘primary structure’ – which is a kind of structural frame- work or armature that these panels fasten to the exterior of. We propose to develop a type of SIPS that does not require this ‘primary structure’, but that can take all wall and roof loads without an internal framework. This load bearing capacity can be achieved by specifying the pro- file or shape of the steel skins that we use, as well as the gauge (thickness) and strength of the steel. For more extreme climates and greater load bearing requirements, we can respond by simply adjusting the gauge and the thickness of the foam centre. We also propose that this SIPS product have coatings on the steel skins that will serve as the final finishes that are extremely durable, UV-resistant and are covered by warranties. Finally, we propose a fastening and detailing system that can be easily accessed and assembled with mechanical fasteners, such that on-site assembly can be achieved with semi-skilled labor in a short time with no complications.

PROTOTYPE: We have selected for our SIPS steel skins a structural steel profile that has its own, excellent load bearing properties, a baked-on, durable Kynar coating, and an optimal modular size for easy assembly. We have developed a fastening method called ‘splines’ that are fastened from the exterior and interior of the panels such

that we have a continuous layer of insulation that is not interrupted by structural studs. This is a what is called a ‘thermally-broken’ detail, and it means that our energy performance is less subject to conductive heat loss, which means more durable buildings (due to condensate and mold or rot) as well as lower energy bills. Two of these steel skins are placed in a form, and a CFC and HCFC-free, 2lb polyurethane foam is injected into the cavity, which ultimately expands and bonds the two steel skins together, forming a structural ‘web’ that results in a rigid, modular panel assembly that is much stronger than the sum of the two steel skins (by as much as a factor of 4, depending on the thickness of the foam layer).

We call this finished product SIPFS – or Structural Insulated Panel and Finish System, which can be used as complete structural walls, floors and roof panels. , The proprietary nature of this system as a PRIMARY STRUCTURE, together with our exterior and interior SPLINE DETAILING and our wall to roof and wall to floor CONNECTION DETAILING as well as our SIDE/ENDWALL, RIDGE, LEADING EDGE and RAIN GUTTER DETAILING.

We are currently in the beginning of the PATENTS PENDING phase, and are producing sample panels for demonstration and destructive testing, and we have structural engineers engaged to provide engineering verification and approval of the complete system and detailing and national certification for use of this product within specific engineered applications (we are developing load tables to guide correct use). We are confident our patent will be approved as we have spent many years looking for precisely this technology, and while there are many products that come close, there is nothing that we have been able to find that is both a primary structural element and finish system all in one unit.

PERFECTED PRODUCT: A complete set of our detailing systems, together with completed samples and full product engineering, together with a patents pending certificate will be complete by Q2 of 2016. A built application of this technology will be in our CUBIC projects, slated for construction in Q4 of 2016.

Our proprietary SIPFS allow us to consolidate the multiple layers of materials in conventional construction into a single, monolithic assembly (image top).

This integration of structure, insulation as well as interior and exterior finishes in a single component for assembly reduces not only the cost and amount of materials required, but also the cost of construction labour. Assembly of completely finished buildings can take place in less than 1 week.

With dozens of colours and matching trim and accessories, our SIPFS let us create shade-screens (perforated panel image middle left), roofs and wall systems for a wide range of uses.

Building our own steel-skinned SIPFS gives us a high degree of design freedom with exceptional quality control. We use materials and finishes that are impervious to moisture and mold formation that can also be made airtight to exceed the most stringent, energy-efficient envelope standards – resulting in healthy buildings that will outlast conventional construction. Unlike conventional SIPS that are chemically glued to one another and can only be destructively disassembled, our SIPS are designed for deconstruction – which means they can be easily repaired, re-purposed or reassembled anywhere. We use only the finest, Kynar-coated 20 Guage American steel with HeatLok, closed-cell, 2lb, soy-based polyurethane insulation.

Eventually, we plan to produce these panels is curved shapes as well as straight linear segments. Our forms are designed to produce panels as long as 30 feet – which is the longest panel required by the our CUBIC roof design. These panels are designed for an unsupported span as far as 20’ with deflection parameters of L/360 or 2/3” of deflection. Cantilevered loads of 5’ are designed with an allowable deflection of L/240. Roof load bearing capacity is designed for 60 psf using a 24Ga steel skin. Wind-loads on roof and wall panels will be designed for 100mph events and will have sufficient hold-down resistance to such events, and linear wall loads will be on the order of 800 plf in a typical 8’ to 12’ tall wall.

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