Frequently Asked Questions (FAQs)

The term “residential building” includes:

1. detached one-or-two family dwellings having not more than three stories above grade plane;
2. buildings that consist of three or more attached townhouse units and have not more than three stories above grade plane;
3. buildings that are classified in Group R-2, R-3 or R-4 and have not more than three stories above grade plane

Exterior walls in REScheck are defined by the assembly type, gross wall area, cavity/continuous R‑value (U-factor for Other walls) and orientation.  All exterior walls are assumed to be of regular rectangular shape with an average wall height of 9 ft., and the wall width is calculated from the gross area as input by the user. 

REScheck wall materials are assumed to be plywood siding, plywood structural sheathing, and foam insulation sheathing on the framing exterior, batt insulation, wood framing, and 1/2-in. gypboard on the interior.  The entire wall is assumed to have structural sheathing. When continuous foam insulation is specified, 100% of the wall is assumed to be covered at the specified R-value.

The U_o‑factor for all frame walls is based on the R‑value of cavity insulation and the continuous insulation R‑value (if used).  If the user does not enter a continuous insulation (sheathing) R‑value (or enters a value of 0.0), the software assumes a sheathing R‑value of 0.83.  This default value gives credit for some minimal type of sheathing material (such as plywood) under the siding. 

Continuous Insulation

Insulation that runs continuously over structural members and is free of significant thermal bridging; such as rigid foam insulation above the ceiling deck. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.

Cavity Insulation

Insulation installed between structural members such as wood studs, metal framing, and Z-clips.

Cavity insulation is used within the wood- or metal-framed wall, while rigid continuous insulation (c.i.) is placed on the exterior side of the framing.  Alternative combinations of cavity insulation and sheathings in thicker walls can be used, provided the total wall assembly has a U-factor that is less than or equal to the appropriate climate zone construction requirements.

Cavity Insulation Calculation in REScheck

REScheck uses nominal insulation R-values. The program does not calculate for compression. For example, if R-19 is entered as the cavity insulation R-value, it assumes the full R-19 in REScheck. Walls with insulation R-values equal to or less than R-15 are modeled in REScheck as having 2x4 studs at either 16" or 24" O.C. (on center) and cavity wall insulation R-values greater than R-15 are modeled as 2x6 studs at either 16" or 24" O.C. 

Continuous Insulation Calculation/Insulated Sheathing

The assemblies listed in REScheck already have a default value added for standard sheathing (depending on the assembly component). If no sheathing is indicated by the user, the sheathing is assumed to be plywood with an R-value of 0.83. If insulated sheathing is used, only 80% of the net wall is assumed to be covered by the insulated sheathing. The other 20% is assumed to be covered with plywood.

REScheck Quick Tip

Cavity R-Value - Enter the R-value of any insulation to be installed in the cavities between above-grade wall structural members. The insulating values of other parts of the building assembly (e.g., gypsum board and air films) are accounted for by the program and should not be included.

REScheck  wall assemblies assume cavity insulation completely fills the cavity.  Users who have unique wall assemblies where the cavity is not completely filled with insulation must account for the air space within their wall assembly calculation and should use “other” as the wall type and enter their respective overall calculated U-factor.

Continuous R-Value - Enter the R-value of any continuous insulation in the above-grade wall. Continuous insulation is continuous over framing members or furring strips and is free of significant thermal bridging. The R-values of other parts of the building assembly (e.g., gypsum board and air films) are accounted for by the program and should not be entered. Insulated sheathing installed on the exterior of above-grade walls is an example of continuous insulation. For structural insulated panels and insulated concrete forms, enter the manufacturer-reported R-value for the entire assembly.

REScheck uses nominal insulation R-values. The program does not calculate for compression. For example, if R-19 is entered as the cavity insulation R-value, it assumes the full R-19 in REScheck. Walls with insulation R-values equal to or less than R-15 are modeled in REScheck as having 2x4 studs at either 16" or 24" O.C. (on center) and cavity wall insulation R-values greater than R-15 are modeled as 2x6 studs at either 16” or 24” O.C. 

For more detailed information on how the walls are calculated please refer to the REScheck Technical Support Document.

To share a particular project with others on COMcheck-Web or REScheck-Web, you have a couple options:

1. One option is to share the log in credentials with them and save all edits to the project under that account. If you are concerned about others having access to your personal account you can set up an independent account (using a unique email from your own present account) and create or upload the project to that new "shared" account.
2. The other option is to take advantage of the Sharing feature in REScheck-Web (see the Getting Started document for details), or download a COMcheck-Web project from your personal account to your desktop then email or hand off the downloaded project file (e.g., myProjectFile.cxl) to other team members. The other team members would each have to upload that cxl file to their account. To do this:
   • Use the button to the right of the "Project Title" edit box (top center of screen) in the Web app. (The upload features requires you to be logged into your account.)
   • Once logged in, the Upload feature is available by clicking My Projects (upper right area of screen)
   • then at the bottom of the popup window click the "Upload project from my computer..." hyperlink
   • click on "Browse...". Navigate to the file on your PC and when selected click Upload.

   Note: if you have many projects already loaded in your account you might need to click All at the top of the My Projects window to see all the projects. Otherwise, only the more recently used projects are listed.

The IECC addresses mixed occupancies by stating that commercial occupancies must comply with the commercial portion of the code and residential occupancies must comply with the residential portion of the code.  

ASHRAE Standard 90.1 addresses high-rise residential and all other commercial buildings.  Residential spaces are those used primarily for living and sleeping and include dwelling units, hotel/motel guest rooms, dormitories, nursing homes, patient rooms in hospitals, lodging houses, fraternity/sorority houses, hostels, prisons, and fire stations.

REScheck determines compliance for additions in the same manner as new construction. When entering an addition, only the new portions of the building need to be shown in the software. REScheck will perform trade-offs between envelope assemblies when determining compliance.

REScheck determines compliance for alterations in a similar manner as additions and new construction, however, each component that is being altered will need to be identified as either meeting an “exemption” from the drop down list of exemption choices or choose “no exemptions” apply and the proposed insulation and/or fenestration values must be entered.  REScheck will perform trade-offs between envelope assemblies that have been identified as “no exemptions” apply to the assembly when determining overall compliance for alterations for a specific project.

The 2009 IECC requires that a minimum of 50% of the lamps in permanently installed lighting fixtures be high-efficacy lamps (2009 IECC, Section 404.1). The 2012 IECC has increased the minimum percentage from 50% to 75%, along with an exception for low-voltage lighting (2012 IECC, Section R404.1).

REScheck currently does not have a lighting input function; therefore, the lighting requirement should be confirmed under the Requirements Tab in the program.

Walls that do not fit into any of the preset categories in REScheck (preset categories come directly from the applicable code currently selected in the Code menu) may be entered under the "Other" wall type. When "Other" is chosen as the wall type, the software requires an overall U-factor for the assembly. The assembly U-factor is calculated from the spacing of any framing and its R-value, the R-value of installed insulation, and the R-value of the balance of assembly (items such as OSB sheathing, drywall, interior and exterior air films, etc.). Details of how to perform a U-factor calculation can be found in any basic heat transfer text book or handbook.

After selecting a basement wall type, a basement wall illustration will appear with input boxes for the basement wall height, depth below grade, and depth of insulation. The illustration helps identify the dimensions being requested. You may enter basement wall dimensions directly into this illustration and select the OK button to have them transferred to the corresponding row in the table on the Envelope screen. If you prefer to enter the dimensions directly into the table on the Envelope screen, you can select Cancel to remove the illustration without entering dimensions. To view the basement wall illustration and inputs at a later time, click the right-mouse button anywhere on the basement row and select Edit Basement Inputs from the popup menu. 

Both the 2009 and 2012 IECC require duct tightness to be verified. Verification can take place via either a post-construction test or a rough-in test.

For the post-construction test, leakage measurement must be made across the entire system, including the manufacturer’s air handler enclosure, with all register boots taped or sealed at a test pressure of 0.1 inches w.g. (25 Pa). The 2009 IECC limits the leakage to outdoors to less than or equal to 8 cfm per 100 ft² of conditioned floor area or total leakage less than or equal to 12 cfm per 100 ft² of conditioned floor area. The 2012 IECC only contains a requirement for total leakage of less than or equal to 4 cfm per 100 ft² of conditioned floor area.

For the rough-in test, leakage measurement is made across the system, with the manufacturer’s air handler enclosure if it is installed. The test is conducted at 0.1 inches w.g. (25 Pa) with all registers taped or sealed. The 2009 IECC limits leakage to less than or equal to 6 cfm per 100 ft² of conditioned floor area when the air handler is installed and 4 cfm when it is not installed. The 2012 IECC limits the leakage to 4 cfm per 100 ft² of conditioned floor area when the air handler is installed and 3 cfm when it is not installed.