Modeling Guidelines for TStud in Ekotrope

Modified on Fri, 30 Sep, 2022 at 9:11 AM

What is a TStud?

BareNaked TStud

A BareNaked TStud is an engineered building product that uses two wood lumber members with an internal wood truss system made from dowels and a poured-in-place insulation (closed cell foam). It is made to replace standard framing lumber with an increased amount of thermal insulation. TStuds are less thermally conductive (and therefore more energy efficient) than traditional studs if insulation is added in the gaps between the flange and spline. It is designed to replace a traditional 2x6 stud.

Figure (1) shows the top and side view of a BareNaked TStud.

R-19 TStud

An R-19 TStud is similar to a BareNaked TStud but has a wider 2.5 inch gap and the gap comes pre-filled with closed cell spray foam so that the stud has an R-value of 19.

Figure (2) shows the top and side view of an R-19 TStud.

Modeling a wall with TStuds in Ekotrope’s R Value Calculator

The calculation described below assumes that the gap between the TStud is filled with insulation. If it is not, our guidance is to model the wall as if regular 2x6 studs are used.

If it is insulated, please follow the steps below to model a wall with TStuds in Ekotrope RATER’s R Value Calculator:

Determine Fold : In the Stud/Cavity layer, enter the dimensions of the TStud (the stud width should be 2.5 inches) and spacing of the framing. Note down the calculated framing fraction.
Determine fTStud : Estimate or calculate the fraction of TStuds being used in the framing. Fraction of TStud is the ratio of area covered by TStuds to the total area of wall covered by the framing. For example, if half of the framing is TStuds, this would be 0.5.
Use the attached spreadsheet to calculate Feffective. In the R Value Calculator, override the framing fraction and enter the value calculated in the spreadsheet.

Explanation of the methodology

Below is a description of the equation used in the spreadsheet.

Type of TStud	Insulation between Flange and Spline
5-½” BareNaked TStud	Blown-in Cellulose, Mineral Wool, or Spray In Open Cell Foam, R-value per inch = 3.7	0.0835
	Blown-in Fiberglass, R-value per inch = 4.18	0.0777
	Spray in Closed Cell Foam, R-value per inch = 6.7	0.0579
R19 TStud	N/A (Spray Foam pre-installed)	0.0518

If the R-value of insulation between flange and spline of TStud is different, use the following equation to calculate the U-factor for 5-½” BareNaked TStud:

where,

Rins= R-value of cavity insulation per inch

Equation (2) assumes the following dimensions of a 5-½” BareNaked TStud:

Spline width = 1.5”

Spline depth = 2.5”

Flange width = 2.5”

Flange depth = 1.5”

Total depth = 5.5”

Diameter of a dowel pin = 1”

Attachments (1)

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Modeling a w....xlsx
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