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.


Services linetec Thermal Strut 2 toneThermal Strut involves two separate extrusions and joins them through the use of engineered structural polyamide plastic strut. Both the inside and outside aluminum profiles are extruded independently with a cavity that will ultimately receive the strut.

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.

Design and aesthetic flexibility

Thermal strut offers design and aesthetic flexibility and versatility with two tone finishes. First, the inside and outside aluminum profiles are finished in anodize, liquid paint or powder coating. Different colors and finishes may be used on each profile as the aluminum is extruded independently with a cavity that will receive the strip.

better performance and efficiency

Linetec has the ability to assemble profiles using polyamide insulating strips (thermal strip) widths ranging from 10mm to 96mm widths. Strip offers increased energy savings with varying thermal separation widths. Greater widths mean greater separation between the aluminum profiles, which means better thermal performance and efficiency.


Linetec can provide 90-degree thermal strip with a single pass to install the strip simultaneously on two planes of material. 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. This single pass process 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.


  • When less than 30 parts, the first and tenth bar of each assembled profile must be tested for angularity and shear strength.  When over 30 parts, the first and every 30th bar is tested.  The pieces to be tested must have a 5” overage for testing purposes.
  • Material must be at least 6 feet in length.
  • Max extrusion length is 30′ (please inquire for longer lengths).



Step One

Insertion – Step 1 of Thermal Strut 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 ensure 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.


Step Two

Insertion – Step 2 in Thermal Strut Process

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 and the 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.


Step Three

Crimping – Step 3 in Thermal Strut Process

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.


In most cases, our estimators will produce your quote within 24 hours. Requesting a quote can be made on-line on our website, by e-mail to sales@linetec.com, or also by faxing Linetec at 1-800-236-2589.


Beyond high-performance fluoropolymer paint, architectural anodize, and powder coating Linetec offers several unique finishing solutions that can be a distinctive design solution for your project.


Linetec has earned a long-standing reputation as a leader in environmentally-conscious practices and finishing options. For more than a decade, environmental responsibility has been written into our core values.


Our technical experts at Linetec provide valuable industry education of high-performance architectural finishes to architects, engineers, specifiers and manufacturers.

Photo credits: Linetec
linetec architectural finishing