Wall products in optimization are based on a common wall assembly with varying configurations of insulation. This article is an overview of what assumptions are included, how the effective R-value (or U-value) is calculated, and what is included for the costs for each wall product.

R value = 1/U value

Overview

The wall options are named according to the specific assembly to achieve a particular effective U-value (or R-value for US). Some materials, like mineral wool, have high heat resistance causing heat to travel slower through them. Other materials, like steel, have very low resistance and heat conducts and travels quickly through it. The result of adding the properties of each layer in the wall together is the effective R-value (or U-value) of the assembly.

The wall options within cove.tool will all assume the same exterior and interior layer conditions but will interchange combinations of insulation type, frame type, and frame spacing to maintain an apples-to-apples comparison. Costs for wall assemblies in the platform are for the insulation only since this is the part affecting the energy simulation most. All possible parameters are presented in the diagram below as the assembly layers. Exterior finish, sheathing, and interior sheathing are held constant for ease of comparison. Continuous insulation and cavity insulation represent the various options for each wall.

Understanding Product Names

Baseline product options are automatically assigned based on the R-value (or U-value) input for the Energy Code. All assemblies that meet a baseline code minimum are named with the code specified and include the following information which can be searched in the product text field on the optimization page.

  1. Code Type & Year
  2. Insulation R-Value (or U-value) & Type
  3. Framing Type & Spacing

Example:
ASHRAE 07,10,13, NCC 2019 - R19 Fiberglass Batt - Steel stud 16 OC

Manufacturer product options are named similarly and include the following information.

  1. Manufacturer Name & Product Name
  2. Insulation R-Value (or U-value) & Type
  3. Framing Type & Spacing

Example:
Rockwool COMFORTBOARD 80 R6 ci - Rigid Mineral Board - Steel studs 16 OC

Effective R-Value (or U-value) Method

We simulated a simplified commercial wall assembly using an online calculator like ekotrope to calculate the effective R-value (or U-value) for walls. Always use the effective R-value (or U-value) of an assembly for energy modeling. Different materials change the real-world performance of a wall and can reduce the rated R-value (or U-value) of insulation by as much as 2/3 in steel-framed walls. Only the effective R-value (or U-value) is used from this method, and the product name will include the assembly information used for each simulation.

The default framing size is 5.5 in. x 1.5 (2 x 6 nominal) for Wood studs and 6 in. x 1.5 in. (6 in nominal) for Steel studs. The insulation type, thickness, and R-value (or U-value) are then assigned according to the chosen insulation product. The framing depth is adjusted up to the next typical stud depth for insulation thicknesses that exceed the default framing depth, as with some higher rated products.

Costs

Retail pricing is collected from readily available sources including Insulation4us.com, Home Depot, Lowes, and similar platforms. Common product manufacturers include Owens Corning, Rockwool, Knauff, and other commercial-grade building materials. We always recommend inviting a cost estimator to your project as early as possible for additional accuracy. Other manufacturers who wish to list products in cove.tool should reach out via chat and share retail pricing per unit and any regional differences.

Costs are broken down to cost per square foot (or square meter) for all assemblies. It is multiplied by the total surface area of the exterior walls, to be included in the whole building cost. In the example above, we are referencing a Rockwool Comfortbatt R23 fiberglass batt insulation product. Calculating the cost per square foot requires the bundle cost divided by the number of bags divided by the total square feet per bag. For example, the cost per square foot is shown below:

$701.61 / 12 bags / 39.8 s.f. = $1.4690 / s.f.

Happy Modeling!

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