Thermal Insulating Strut

The main function of a thermal break system is to separate an aluminum profile into two parts to reduce thermal conductivity in a window. The two ways of doing this are by using polyamide insulating strips or poured polyurethane.

Aluminum is a highly thermal conductive material that will rapidly transfer exterior climatic temperature unless something is done to stop the thermal conduction. A thermal barrier system will improve thermal performance while maintaining the structural and long-term durability of the fenestration unit. According to the thermal strut manufacturer, Technoform, aluminum is 533 times more conductive than polyamide insulating strips.

Thermal Insulating Strut

Thermal Strut involves two separate extrusions and joins them through the use of engineered structural plastic strut. Both the inside and outside aluminum profiles are extruded independently with a cavity that will ultimately receive the strut.

With Technoform thermal strut, products can be manufactured with two-tone finishes; because interior and exterior components can be coated before assembly. Architects and designers can choose to apply the interior and exterior finishes that best match their cost, performance and design requirements.
Assembly Process
Knurling - step 1 in Thermal Strut process

Knurling.  Knurling is the first step in the production process.

It is performed to produce teeth in the aluminum pocket that will “bite” into the Strut during the crimping process. Proper knurling is required to insure adequate shear strength of the composite profile.

Quality check for knurling: Proper knurling generates teeth that are between 0.15 mm and 0.30 mm long. The distance between teeth center-lines should be no greater that 0.78 mm. To generate adequate size and spacing of the teeth, the Linetec operator must (a) properly align the knurling wheels in the aluminum recess, (b) provide adequate pressure upon the knurling wheels during the process, and (c) use a knurling wheel capable of providing teeth of ample size and spacing.
Insertion - step 2 of Thermal Strut process

Insertion.  Prior to struts being inserted they are properly selected and verified against the production paperwork. Care must also be taken to assure the struts are oriented per the order requirements - not all struts are symmetric.

The strut is aligned with the cavity, and held by small automatic clamps on the back side of the first knurler. As material is run through the first knurler, the strut slides into the extrusion cavity. This extrusion with the strut in it, then gets transferred to the second knurler, and slid into place by an automated push plate. Little finger like slides guide the strut to the proper alignment with the other extrusion half of the assembly. Once the strut is in place, sensor is reached, the second knurler will turn on and slide the second extrusion over the first. The assembly is connected by two knurled extrusions held together with thermal strut. This loose assembly gets transferred to the crimp or rolling machine.
Crimping - Step 3 in Thermal Strut process

Crimping.  The crimping process uses three sets of wheels which rotate the aluminum on to the strut to mechanically lock it into place, forming the bond between the two extrusions and the strut.

The assembled aluminum and Strut profiles then act as a composite to transfer loads. Over 1300 pounds of pressure is applied in stages to crimp the aluminum. The first set of wheels applies 50 percent of the pressure while the second set applies 100 percent. The third set of wheels help to straighten the extrusion and completes the crimping process.

The crimping machine is set-up and adjusted for each new individual assembly. Adequate support must be provided to the assembly during the crimping process and sufficient pressure must be supplied to close the aluminum pocket tightly against the strut. Machine setups are determined the first time a particular assembly is run. Provided adequate shear values are attained, the machine settings are then recorded and used as a general guideline each time a particular assembly is required.
Sustainability & LEED
Aluminum is a highly thermal conductive material that will rapidly transfer exterior climatic temperature unless something is done to stop the thermal conduction. A thermal barrier system will improve thermal performance while maintaining the structural and long-term durability of the fenestration unit. Customers that choose Linetec, can rely on our thermal barrier service to ensure optimal performance of the thermal barrier.

Thermal insulating strut can contribute to earning performance points toward LEED® Certification, the Green Building Rating System.

Energy & Atmosphere            Optimize Energy Performance

Achieving increasing levels of energy performance above the prerequisite standard to reduce environmental impacts associated with excessive energy use.

Indoor Environmental Quality          Thermal Comfort, Design

Provide for a comfortable thermal environment that supports the productivity and well-being of the building occupants.

















Benefits of Thermal Strut
Thermal Insulating Strut

Structural insulating strut made of polyamide have been the chosen method of thermally breaking aluminum fenestration products for more than thirty years overseas, in Germany, where the product originated.

Technoform strut is made of fiberglass reinforced polyamide with glass fibers oriented in 3 directions for optimal structural performance.

Strut offers increased energy savings with varying thermal separation widths including those greater than any other thermal break system.

Structural performance and mechanical response are exceptional with the multidirectional glass fibers oriented in 3D to give improved load transfer.
Thermal Insulating Strut - Two-Tone

Design and aesthetic flexibility and versatility with two tone finishes, since interior and exterior components can be finished before assembly. Architects and designers can choose to apply the interior and exterior finishes that best match their cost, performance, and design requirements.

    Technoform's glass filled polyamide strut provides a positive mechanical bond, with no thermal break slippage

    Technoform offers its customer design and prototyping capabilities to make any customer design required presenting virtually endless design possibilities.

    Material Guidelines

    Thermal Insulating Strut

    The first bar of each assembled profile to receive thermal strut must have a 9" overage and every tenth bar thereafter must have a 5" overage for testing purposes.

    Material must be at least 6 feet in length.

90-Degree Thermal Strip
Thermal Insulating Strut

90-degree thermal strip with a single pass using Technoform Bautec’s polyamide insulating strips and Müller Technologies AG’s knurling equipment to install the strip simultaneously on two planes of material.

The need for direct access from both sides has always been a design limitation of strip systems. This new capability frees up window and curtainwall designers to detail changes in place more efficiently, using a single assembly, rather than multiple pieces – without compromising energy efficiency or condensation resistance.

Traditional 90-degree thermal strip installation was time-consuming where each piece is knurled up to three times before crimping and shear testing. This amount of handling increases the potential for marring and damage to the finished material. Linetec’s 90-degree thermal strip process reduces the knurling to one step. This not only saves time and labor, but also minimizes inconsistencies and waste, holds customer-specified tolerances for U-Factor and shear testing, and delivers a high-quality finished product.”

Structural performance and mechanical response are exceptional with the multidirectional glass fibers oriented in 3D to give improved load transfer.



Impact of Thermal Break (IR Image)

Aluminum has many tremendous advantages including structural integrity, sustainability, design flexibility etc. however aluminum has high thermal conductivity. Adding insulating thermal Polyamide strips to the framing members to separate the inside and outside metal greatly enhances the product thermal performance and reduces the amount of heat transfer, therefore saving energy while increasing occupant comfort.

                    

With lighter colors indicating higher surface temperatures, the above diagrams show heat transfer through a non-thermal aluminum product, vs. an aluminum product with a thermal barrier using polyamide strips.



Visit Technoform's website to learn more about thermal insulating strut

Window condensation

How Thermal Barrier Systems Can Improve Aluminum Windows

Energy costs rank among the top concerns for building owners and managers, while comfort and indoor temperature control head occupants' top concerns.

Read Linetec's article on improving the thermal performance and influencing long-term savings on the life of your building.