Frequently Asked Questions (FAQs)

Topics - Commercial - Federal - Manufactured Housing - Multi-Family - Municipal - Residential
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 ...
Topics - air leakage - mechanical - ducts - Residential - duct testing - testing
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,...
Topics - building envelope - basement - walls - Residential
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...
Topics - building envelope - windows - windows - fenestration - Commercial - sprandel systems - u-factor
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...
Topics - building envelope - walls - Residential
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,...
Topics - lighting - Residential
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...
Topics - Commercial - Residential - status of state energy codes
Code adoption takes place at the state, and in some cases municipal, level. To determine the code in a particular state, visit the Status of State Energy Code Adoption page.
Topics - addition - alteration - building envelope - Residential
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...
Topics - Commercial - Residential - code
The IECC addresses mixed occupancies by stating that commercial occupancies must comply with the commercial portion of the code and...
Topics - building envelope - Commercial - software
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...
Topics - lighting - lighting - exterior - lighting - interior - Commercial
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...
Topics - addition - alteration - Commercial
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...
Topics - Residential - building
The term “residential building” includes: detached one-or-two family dwellings having not more than three stories above grade plane; buildings that consist of three or more attached townhouse units and have not more than three stories above grade...
Topics - building
A commercial building is defined as all other buildings that are not considered a residential building.
Topics - building envelope - Commercial
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...
Topics - walls - Residential
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...
Topics - building envelope - Commercial
Louvers are best treated as un-insulated portions of the wall. You can add them as a separate wall type (for example, if they are metal, metal building would probably be most appropriate) with no insulation but a wall area. COMcheck will do the...
Topics - windows - Commercial
When entering your fenestration in COMcheck the pop up window has three options to enter your fenestration.  Choose the second option called Product Performance in accordance with NFRC.  If you do not have a pending product number, enter NA and...
Topics - city not found
Choose a city that is the closest with the most similar weather.  Check with the building official where the project is located to confirm the city selected will be acceptable or if choosing “county” as the designation would be more appropriate. ...
Topics - envelope calculation
The COMcheck trade-off alternative used for enforcing the IECC is permitted under a clause in Section 101 (referencing 2012 IECC). That clause is a fairly common code element that gives the jurisdiction and, more explicitly, the building official...
Topics - envelope assembly calculations - thermal bridging
COMcheck does account for thermal bridging of framing members, furring, etc. (depending upon the assembly). U-factor assembly calculations are taken from ASHRAE Appendix A and ASHRAE Fundamentals. The methodology used to calculate compliance is...
Topics - simulation failed - weather data
When using the ASHRAE 90.1-2013 energy code, COMcheck needs to have two EnergyPlus weather files in this folder C:\ProgramData\COMcheck\eplus\weather. The most common reasons for a compliance simulation failure are:  the files are not located at...
Topics - building envelope - Commercial - 40% WWR glazing limitations
The Scope and Application sections of the 2009 IECC address use of ASHRAE 90.1 (2007) as an alternative.  See below for the text.  It is appropriate to use ASHRAE 90.1 as an alternative when your building exceeds 40% glazing, although it does not...
Topics - building envelope - walls - windows - fenestration - windows - glazing - Commercial - calculating above-grade wall area
COMcheck implements the calculation based on the definition of above and below-grade walls in the applicable code.  The calculation for percentage of glazing in ASHRAE Standard 90.1 and the IECC are different as the IECC only looks at above grade...
Topics - gbXML
There are a couple things to note about the current import process implementation: Currently we only focus on importing envelope components. This means you will still be required to manually specify your space types, lighting fixtures, and...
Topics - printing issues - desktop versions
There are a couple of things to try: Completely remove REScheck or COMcheck Use the Windows operating system “Programs and Features” uninstaller Open Windows Explorer and navigate to C:\Users\<your username>\AppData\Roaming\<REScheck or...
Topics - basement - walls - performance alternative errors
The problem most likely relates to the basement walls you have specified. The DOE-2 simulation program used in REScheck for performance alternative calculations sometimes generates this error even though the entries appear valid.  As a workaround,...
Topics - Commercial - space conditioning - ASHRAE
ASHRAE’s space conditioning types include: conditioned space, unconditioned or semi-heated space. ASHRAE’s definitions for these types: space: an enclosed space within a building. The classifications of spaces are as follows for the purpose of...
Topics - Commercial - warehouse
Warehouses must be considered carefully. The first consideration is whether it is going to be conditioned, cooled and/or heated, or semi heated. Next is the applicable energy code. Older codes did not require the building envelope to meet the...
Topics - Commercial - low-energy - non-conditioned
In the 2015 IECC, Section C402.1.1 Low-energy buildings – low energy buildings or portions separated from the remainder of the building by a building thermal envelope complying with the code, can be exempt from the building thermal envelope...
Topics - Commercial - Residential - historic
Note:  The key point is not the age of the building, but whether it is registered or eligible to be registered and listed.  In the following cases, historic buildings are considered exempt from provisions of the energy code (however, we recommend...
Topics - VRF systems
In COMcheck 4.0.0.3 and newer, you can now break up your VRF into two systems.  One can be defined as the VRF Outdoor/Central unit and is selected as heating equipment→heat pump list-→"VRF xxxx". This type of system will enforce the system...
Topics - building envelope - doors - calculated U-factor
“Standard 90.1 requires that U-factors (and air leakage) for doors be determined in accordance with the NFRC rating procedures.  All NFRC ratings are based on the whole product, including the frame.” Consequently, for compliance with Standard 90.1...
Topics - high-efficiency HVAC option - electric furnace
Electric central furnace does not qualify for the High Performance HVAC efficiency package. ALL systems in a project must meet the criteria of C406.2 and if your system(s) cannot be found in C406.2 then by default it does not qualify. In these...
Topics - sharing data - loading data
To share a particular project with others on COMcheck-Web or REScheck-Web, you have a couple options: One 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...
Topics - merging files
Unfortunately, there is not a way to merge files.  The web tool is definitely the way to go when you have multiple contractors involved as you can create a generic log in and each contractor can work on the same project file to enter their...
Topics - Commercial - registered design professional
The commercial energy code requires that a registered professional submit compliance documentation (construction documents and compliance verification).    In the IECC, Section C103.1 Construction Documents, General, the wording states that...
Topics - lighting - fixture library
Yes. Locate the lighting fixture library in this location defaulted by COMcheck:    C:\Users\<your user name>\AppData\Roaming\COMcheck\fixtureLibrary.xml. Copy fixtureLibrary.xml from this location to the same directory on the other computer...
Topics - air leakage - Commercial
Yes, in Section 402.4 of the 2012 IECC, testing is now required instead of an option between testing or visual inspection such as in the 2009 IECC.  Also, the air leakage rates changed. Air Leakage Rates 2009 IECC 2012 IECC Climate zones 1-2...