Frequently Asked Questions (FAQs)

COMcheck computes an envelope index that is a reflection of the difference between a 'design' building energy performance factor (EPF) and a 'code' or budget building EPF.  The total building load (made up of cooling, heating, lighting, and miscellaneous plug load) is determined by the location you are in, the specific assembly and building types you specify, and internal gains from lighting and miscellaneous plug loads, and of course the thermal properties and orientation of the envelope assemblies. The methodology used to determine EPF is provided in ASHRAE 90.1 Normative Appendix C: Methodology for Building Envelope Trade-off Option.

COMcheck 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. COMcheck will perform trade-offs between envelope assemblies when determining compliance.

COMcheck determines compliance for alterations on a component-by-component basis. Each component is checked to verify it meets or exceeds the minimum prescriptive requirements of the selected code. No trade-offs are available for alterations and no compliance percentage will be generated–the software shows a pass/fail for compliance.

Exemptions and allowances for lighting are an option that must be activated in COMcheck. To activate the exemptions and allowances, take the following steps:

• Select either the Interior Lighting or Exterior Lighting Tab
• Go to the Options menu and select Interior Lighting Exemptions and Allowances for Interior Lighting or Exterior Lighting Exemptions for Exterior Lighting.

Note that activation of the exemptions and allowances will add an extra column to the applicable worksheet–it may be necessary to enlarge the window in order to see the new column.

If multiple users are putting information into COMcheck, each may fill out the appropriate section independently. However, all sections of the building must show compliance to the same code or standard (e.g., cannot show envelope compliance to IECC and lighting compliance to ASHRAE Standard 90.1). COMcheck does not require that all sections be completed to perform compliance checks.

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.

Fenestration is considered anything that transmits light, however, COMcheck cannot calculate fenestration without having a wall associated with it. In this case the wall is entirely fenestration therefore, the square footage would be the same for both the wall and window area and the software will calculate the wall area as net zero since the fenestration is the entire wall.

For the spandrel glass or translucent wall systems the way to enter that into COMcheck would be to first define a wall by choosing wall as "other" from the drop down list of wall assembly types, enter the square footage of the wall system (e.g. 100 sq. ft), enter the U-factor for the wall system (e.g. 0.23) and also you will need to enter the heat capacity of the wall. For information on heat capacity and how to calculate it, in COMcheck, go to the help menu, help topics and wall software inputs.

After defining the wall, define the window area by choosing window as "other" from the drop down list of window assembly types, enter the square footage of the wall system (e.g. 100 sq. ft.) and choose option two under Fenestration details "Product performance tested in accordance with NFRC", if you do not have a product ID, enter "NA", then enter your U-factor and SHGC values from the product manufacture specifications.

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.

• Copies of the International Energy Conservation Code (IECC) can be purchased from the International Code Council website.
• Copies of ASHRAE standards can be purchased from the ASHRAE website.
• For codes specific to a state or municipality, contact the authority having jurisdiction.