In 2024, the U.S. Department of Energy purchased the RED online building science tools, both the free version (now called Standalone) and the enhanced Pro version. Both versions of the tools are now free and are available on the Building America Solutions Center website, maintained by Pacific Northwest National Laboratory (PNNL): https://basc.pnnl.gov/redcalc. The tools are officially referred to as the “RED Calc” tools at their new location. Once the RED Calc tools were relocated, they were no longer available on the website you are now on, www.redcalc.com.
This article will walk you through most of the details of using the Pro version of the ASHRAE 62.2-2016. The Pro version requires you to create an online account with an email and a password. After you create this account, you may create folders, save all your calculation files, save and print reports, and share your folders and files with colleagues if they log in with the same email and password. Additionally, you are able to enjoy all the enhanced features of the Pro version over the Standalone version of the tool.
The screenshots used below are for an example of an existing two-story house in Denver, Colorado, of 2000 square feet. For general instructions for using the RED Calc Pro tools, find the “Pro Manual” on the website: https://basc.pnnl.gov/redcalc/pro. To view and work with the ASHRAE 62.2-2016 tool, you will need to select it from “Add Tool” at the upper right three-dot menu on the Pro tool or select the button with a plus sign and a wrench.
Although the topics addressed below do not include all the details, they do focus on the major elements.
The Details of the ASHRAE 62.2-2016 Pro Tool
- Always make sure “Use infiltration credit” is enabled, as shown in the screenshot below. However, there is an exception: if you are sizing ventilation for a dwelling in a multifamily building with one dwelling above another (stacked), turn the “Use infiltration credit” toggle switch off. The ASHRAE 62.2 Standard does not allow the use of an infiltration credit in multifamily buildings such as this. Notice that the “Construction type” selected is “Existing”.
2. Select the “Closest Weather Station” to the dwelling location, even if it is in another state. Before using a weather station located in another state, make sure you have approval from your program manager. The weather station used for this example is Denver International Airport. The resulting “weather and shielding factor” impacts the infiltration credit.
3. Remember, at any time, you can click any input or result name label to activate “pop-up help”. This context-sensitive help is likely to answer questions you have about the input or result. The example below is for “Dwelling height” in the “Dwelling-Unit Data” section of the tool.
4. “Dwelling-Unit Data” Section
a. “Floor area” – Include the floor area that is within the pressure boundary of the dwelling. If you have questions about whether to include the basement or parts of it, click the “Floor area” label for more information.
b. “Number of Occupants” – Enter the actual number of occupants or the number of bedrooms in the dwelling, plus one.
c. “Dwelling height” – There are often questions regarding the proper height to enter. Click on the “Dwelling height” label for more information (or see the screenshot above). This value is used for the calculation of the dwelling stack-effect infiltration.
d. “Leakage @ 50Pa” – Enter the post-weatherization blower door test value, actual or estimated. This is often referred to as the CMF50 of the dwelling.
5. There are various reasons to turn on “Use Adv Blower Door Inputs”. Note: If you close this section of the tool, the numbers you enter here will not be used in the calculations, although they will remain in the input boxes. So, make sure you leave this section of the tool open for the adjusted values to be used in your calculated “Dwelling-Unit Ventilation Results”.
a. “Blower door test type” – Most often, a depressurization test is done because it is easier than a pressurization test. If you have a good reason to conduct a pressurization test, you must change the default “depressurization” to “pressurization”. This choice only makes a difference in the “Adjusted leakage @ 50Pa” if the “Indoor temp” and “Outdoor temp” in this section of the tool are different from one another.
b. “Indoor temp” and “Outdoor temp” – It is important to enter these values if the temperatures are extreme. Different temperatures mean differing air densities; entering the temperatures adjusts the true CFM50 flow accordingly.
c. “Pressure exponent” – It is best to allow this value to remain at the default of “0.65” unless you know the actual pressure exponent of the dwelling you are testing with your blower door. Determining this exponent requires a multi-point blower door test.
d. “Weather station altitude” – Again, the density of air is affected by altitude, which in turn impacts the adjusted blower door CFM50 value. This altitude value is automatically entered when you select the “Closest Weather Station” in a previous section of the tool. You may change this value in the input box if you wish.
e. “Adjusted leakage @ 50Pa” – This is the blower door test CFM50 corrected result for the inputs entered in this section of the tool.
6. Always open and fill in the “Use Local Vent Alt Comp” section of the tool. If this section of the tool is not displaying, it is because “New” is selected for “Construction type” in the first section of the tool. Change this selection to “Existing”, unless you are sizing ventilation for a new dwelling. Note: Your entries in this section of the tool should always include the post-weatherization values for the correct dwelling-unit ventilation (DUV) calculation.
a. Always include at least one “Kitchen” from the dropdown menu.
b. Enter a “Fan flow” value for every kitchen and bathroom. If there is no fan, enter zero. This ensures the DUV will be calculated correctly. Note: Some analysts fill in this section of the tool for the airflow rate of existing kitchen and bathroom fans when they initially inspect the dwelling (pre-weatherization), and again for the airflow rates of the fans as they intend to upgrade them (post-weatherization). If you print the “pre” and “post” versions of the tool, you have a record of the ventilation you found at the dwelling and how you upgraded it. Important: If you choose to install a new fan in a kitchen or bathroom, the airflow rate of the new fan must comply with the requirements of the ASHRAE 62.2-2016 Standard.
c. Make sure to set the window toggle switch in the tool properly for each kitchen and bathroom. If the kitchen or bathroom has one or more openable windows, set the toggle to “Yes”. Any deficit for a kitchen or bathroom with one or more openable windows is reduced by 20 CFM.
d. Some analysts use this section of the tool so that a particular DUV rate or ventilation device can be used. For example, the Florida weatherization program often uses a 40 cfm ERV (Energy Recovery Ventilator) for their climate’s high humidity conditions. They try different combinations of bathroom and kitchen fans in this section of the RED Calc tool until the 40 CFM ERV satisfies the requirements.
7. Dwelling-Unit Ventilation Results”. This is what the RED Calc ASHRAE 62.2-2016 tool is intended to calculate: the dwelling-unit ventilation, the last line of this section of the tool screenshot section below, highlighted in green, “Required mech vent, Qfan”.
a “Outdoor air target, Qtot” – As the result states, this is the total amount of outdoor air needed in the dwelling for acceptable indoor air quality, based on ASHRAE 62.2. For the example screenshot shown below, this is 90 CFM. This outdoor air, Qtot, has two basic sources: infiltration, Qinf, and mechanical dwelling-unit ventilation, Qfan.
b.“Alt compliance, Qalt” – This is the CFM value that must be added to Qtot to compensate for the deficit of local exhaust ventilation resulting from the “Use Local Vent Alt Comp” section of the tool. Notice for the screenshot example above shows a “Total deficit” of 110 CFM. The 62.2 Standard requires ¼ of this total deficit be added to the “Dwelling-Unit Ventilation Results”, or 27 CFM.
c.“Infiltration credit, Qinf” – This is the average air leakage through the dwelling envelope. The greater this value, the lower the mechanical DUV, Qfan, requirement.
d.“Required mech vent, Qfan” is the primary result this RED Calc tool is intended to calculate; for this example, 43.5 CFM, highlighted in green. As a reminder, this is the dwelling-unit ventilation required for the finished dwelling; this is the post-weatherization dwelling condition for an existing dwelling or the finished-construction condition for a newly built dwelling.
8. “Use Fan Timer”. There are two methods of tuning in or setting the final dwelling-unit ventilation (DUV) needed after your post-weatherization or finished-construction blower test result is known: 1) you may use a variable-speed timer [for this example, with a Qfan requirement of 43.5 CFM, you would set the DUV fan to operate continuously at 44 or more CFM], or 2) you may use an automatic programmed timer to operate the DUV intermittently. For this second option, you can use the “Use Fan Timer” section of the RED Calc tool as shown below.
a. The “Fan capacity” is the airflow rate of the DUV fan when it is operating. This may be the maximum fan airflow rate or a lower rate while the ventilation device is operating, but it must be at least the “Required mech vent, Qfan” calculated value. For this example, a “Fan capacity” of 80 CFM is used.
b. The calculated “Set fan to run” value is 33 minutes per hour (see green highlight). Thus, in order to achieve the equivalent of operating the DUV at an airflow rate of 44 CFM running continuously, this intermittenly-operating fan running at 80 CFM must operate for 33 minutes each hour.
Example RED Calc 62.2-2016 Tool Used in Article
Report for the RED Calc ASHRAE 62.2-2016 Tool
The corresponding tool report is easy to read and may be downloaded as a PDF for your files or to give to your customer. The breadcrumb links (in blue font just under the top red banner of the report), may be named and structured so that your report is easy to identify.
At the bottom of each RED Calc Pro tool, there are two spaces to fill in “Report Info”. The first space is the “Report header” for your company or agency identification, or the client/customer name and address. In the “Settings” section of any RED Calc tool, you may include a “Default report header” that will automatically appear at the top of all your reports. This is a great place to include your company/agency information. Any information included in the “Report Info” must be entered using “markdown” language or code.
The “Report footer” may include any information you wish. We have often used this space to include a work order for the job or special instructions. Again, markdown language must be used. See the RED Calc Pro manual, https://basc.pnnl.gov/redcalc/pro, for more information about using markdown and including report headers and footers. The screenshot of the tool report below does not include headers or footers.
