Insulated Studs - What They Are and How to Use Them

What Is An Insulated Stud?

An Insulated stud is a replacement for the standard 2x6 stud with a sandwich of two boards separated by a 2.5-inch space. Angled dowel trusses hold the studs together. The studs come pre-insulated with closed-cell foam, or contractors can add their own during installation. Contractors can apply insulated stubs as studs, headers, or plates. 

Are There Any Other Products Similar to Insulated Studs?

Other options have inherent sustainable features, such as oriented strand board, the ZIP System R Sheathing, laminated sheer, and laminated strand lumber. The ZIP System comes the closest to incorporating insulation into the product line. InsoFast offers a system where metal studs hold insulated panels in place for basement wall and exterior projects. 

Who Makes Insulated Studs?

Brian Iverson invented insulated studs and formed the company Tstud to manufacture and sell them. Tstud also sells "Barenaked Tstud" which is the stud without the foam core installed, enabling homeowners and contractors to pick their insulation. The company's website offers average "R" and "U" values for different insulation types to help you choose the right insulation material. The "Tstud R. 19" comes with closed-cell foam already installed. 

What Are the Standard Insulated Stud Sizes?

Insulated studs replace 2x6 and 2x8. The 2x6 is more widely available. The width for the Tstud measures 5.5" and 7.5." Two 2x3s compose the sides of the sandwich.  

Are Insulated Studs Code Compliant?

Insulated studs comply with building codes in the United States and Canada and have met all ASTM (American Society for Testing and Materials) standards. The studs also meet hurricane and seismic criteria up to 24" on center framing in the US and Canada. Tstud achieved EPA compliance for 2020.

Are Insulated Studs Energy-Efficient?

Insulated studs are energy-efficient and carry an R-value of 20, compared to traditional framing's R-value of roughly 4.38 and 6.88 for 2x4 and 2x6, respectively. They create a 99.23% complete thermal break with the stud, meaning nothing gets through. Studies found the thermally broken wall assembly, like those made with Tstuds, is 150% to 280% more efficient than standard 2 x 6 framing.

What is a Thermally Broken Wall Assembly?

Wall assemblies are generally broken by studs every 16 inches. Studs lose energy - they typically have an R-value of 4.38 to 6.88, depending on size, when placed between the insulation and insulated spaces.

The "thermally broken" wall assembly means the framing members have the same R-value as the insulation. The studs are R-19, but when next to the insulation, it goes up to R-22.

What Types of Insulation Can You Use With Insulated Studs?

Closed-cell foam works best using an HFO (hydrofluoroolefin) blowing agent. Insulated studs offer studs already pre-filled with Polyiso foam. Contractors can install standard batt insulation between the studs, including fiberglass batt (R-13, R-19), cellulose, mineral wool, continuous blown in and rigid fiberglass, and closed cell spray foam. Rigid insulation on the exterior makes the thermal shell even stronger.

Are Insulated Studs Load Bearing?

The double studs carry much more weight than typical lumber. Thermally broken wall assemblies are three times stronger than 2x6s. When used as top plates, thermal broken wall assembly offers 1.5 times more strength than 2x2s. Contractors can use insulated studs for walls up to 16 feet high and buildings up to 5 stories.

Can Insulated Studs Reduce the Amount of Lumber Required?

Using insulated studs and significantly reduce the amount of lumber used for framing. The strength of insulated lumber allows 24" on center framing instead of 16" on center in typical projects. On average home projects, insulated studs eliminate as many as 58 wall studs that would require 2,000 fasteners and 200 lineal feet of top plate. 

Are Insulated Studs Soundproof?

That loud neighbor, those kids having a good time in another room? You will have to listen close to hear them because they have an extra dose of insulation that significantly dampens sound. Thermally broken wall assemblies reduce sound by 22% compared to a well-built party wall. The United States Gypsum found broken wall assembly offers a "sound transmission class" rating of a +6, equal to a wall being constructed with a "resilient channel" on both sides of a wall to absorb noise.

Are Insulated Studs Fire Resistant?

Yes, the studs rate Class A on the Y-axis fire rating compared to Class C for 2x6s. In an E84 flame spread test, the insulated studs retained 90% of their original structural strength. UL extensively tested Tstud's products.

Are Insulated Studs Resistant to Mold and Mildew?

Tstuds will be adding a coating to its R. 19 model to protect from fungal decay, mold, and wood-eating insects such as termites.

How Do Insulated Studs Compare to Laminated Strand Lumber (LSL)?

Both products have supporters and test well against competitors. LSL, made from a mixture of aspen and maple hardwoods harvested from sustainably managed sources, finds use as floor joists, wall plates, stair stringers, columns, rim board, wall frames, and window headers. Insulated studs replace only studs in structures.

How Do Insulated Studs Compare to Laminated Veneer Lumber (LVL)?

Composed of dried and graded wood veneer and usually coated with a waterproof phenol-formaldehyde resin adhesive bonded together with high heat, LVL differs from LSL. But it functions in buildings the same way. It serves as an alternative to solid lumber and works well in situations requiring load-bearing wood. Again, insulated studs have one primary use; LVL has several.

What Are the Pros of Insulated Studs?

Insulated studs offer a 6 in 1 solution. 

1. The product's strength allows for more generous spacing between studs, to 24 inches, saving as much as 24% of studs.
2. The thermal core has three times the insulation of traditional studs, keeping the heat in during the winter and out in the summer. 
3. Insulated studs minimize noise. 
4. The studs handle heavy wind loads. 
5. They char rather than spread or melt during a fire. Tests show 90% of insulated studs remain intact after a 3,500 degree 10-minute long fire.  
6. The product resists mold, termites, and rot, as tests will soon show.

What Are the Cons of Insulated Studs?

Insulated studs lack a long track record because they are a relatively new product that contractors have just discovered. Although the market responded positively to a video that Tstud launched last year, there hasn't been much installation information. The video attracted nearly 1 million viewers. The company has not released a 2x8 version yet. Electric boxes on exterior walls could pose problems, and plumbers must pay attention when installing near pipes to avoid cutting into dowels. Insulated studs cost more than everyday studs, but the total cost of projects makes them competitive.

How Much Do Insulated Studs Cost?

Insulated Studs cost between $2.00 to $3.00 per board foot. But being able to space studs at 24 inches and no need for deep headers around doors and windows saves on the amount of wood needed for products. One contractor put the cost at $1,800 to $2,000 extra per house compared to wood studs. "More than worth the cost," he told Green Building Advisor.