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Condensation Index
Condensation Index and
Other Condensation  Ratings     
 
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Condensation Index
ANSI/NFRC 500: Procedure for Determining Fenestration Product Condensation Index Ratings

In 2011, the NFRC Board of Directors made a strategic objective for staff to investigate and develop the Linear Energy Analysis for Fenestration (LEAFF) procedure. The LEAFF technical methodology, using a regression line formula (trendline) to calculate the U-factor whole product ratings, was approved by the NFRC Board in Fall of 2019.

During the development of the LEAFF procedure, NFRC also developed the Condensation Index (CI) rating (ANSI/NFRC 500-2020), using a coldest point temperature methodology based on CSA A440’s Temperature Index (TI) indicating a product's ability to resist the potential for condensation. The goal of CI is to implement a condensation rating that will help guide the design of fenestration systems to minimize the formation of condensation. CI will replace the Condensation Rating (NFRC 500-2017).

This webpage introduces NFRC’s Condensation Index rating and helps the industry understand the differences and similarities of the four current condensation ratings:

  • NFRC's Condensation Index (CI): ANSI/NFRC 500-2020
  • NFRC's Condensation Resistance: NFRC 500-2017
  • FGIA's Condensation Resistance Factor (CRF): AAMA 1503
  • CSA's Temperature Index: A440.2/.3

These different methodologies evaluate condensation, however, each uses the same standardized environmental conditions [exterior: -18ºC (0ºF) and interior: 21ºC (70ºF)] and provide dimensionless ratings between 1 and 100, with the higher values indicating better performance.

It is important to note that the usefulness of such ratings or indexes in assessing and predicting condensation performance is limited for condensation-critical applications. The actual risk of condensation can be influenced by several variables, such as the thermal conductivity of surrounding building construction, interior/exterior trim, humidification control, shading, and the method of heat distribution on the interior plane of the assembly.

To apply the CI rating in real world conditions, the NFRC 501-2020: User Guide to the Procedure for Determining Fenestration Product Condensation Index Rating document can assist you to determine the CI range for consideration due to environmental factors that lead to the possible formation of condensation. The following are three examples in Section 7 of the NFRC 501 which can lead you to determining the CI rating required to minimize the formation of condensation:

  • Find the potential CI rating when you know the temperature and relative humidity of the interior room.
  • You know the room air temperature and CI rating so you can determine the relative humidity threshold to limit the formation of condensation.
  • Demonstrating how the same product with the same CI rating can be used in multiple geographical and climate locations. 

One major benefit found when using the simulation method is the convenience to determine condensation ratings for many products, in comparison a physical test can only determine the condensation resistance rating for only one product option. A simulation methodology can reduce the time and cost to obtain a products’ condensation rating.

One important note regarding the test methods referenced is that no matter the rating or index value, the specifications can only be used as guides to selecting fenestration systems. While these ratings are not directly exchangeable, each of them are a relative indicator of a fenestration product's ability to resist the potential for the formation of condensation at a specific set of environmental conditions and that there is no assurance that a selected system will not experience condensation.

This webpage will help to familiarize you with each of the condensation methods and explain the partnership with each of the association’s involvement and the intent to align the condensation test methods.

Need to contact staff?

Contact: Senior Manager, Programs, Dennis Anderson

Standards and Ratings

Simulation Standards and Ratings

The following are the simulation methodologies to determine whole product condensation ratings.

 

  • NFRC 500-2017: Procedure for Determining Fenestration Product Condensation Resistance Values

    • The Condensation Resistance value for each component (frame, edge-of-glass, and center-of-glass) are calculated using a weighted summation of the positive temperatures below the dew point temperature from the three prescribed condensation reference point temperatures and at relative humidity of 30%, 50%, and 70%.

    • The total fenestration product's Condensation Resistance rating is the lowest calculated Condensation Resistance value from the corresponding component's average wetted values . 

  • ANSI/NFRC 500-2020: Procedure for Determining Fenestration Product Condensation Index Ratings

    • The fenestration product shall have three component CIs calculated based on the coldest temperatures determined from the frame (CIf), edge-of-glass (CIe), and center-of-glass (CIc).

    • The total fenestration product's CI rating is the lowest component CI value of the three calculated between the CIf, CIe, and CIc.

Physical Testing Standards and Ratings

The following are the physical test standards to determine whole product condensation ratings. 

  • NFRC 500-2017: Procedure for Determining Fenestration Product Condensation Resistance Values

    • Only if a product cannot be simulated shall a Condensation Resistance rating be determined via the physical test method. This physical test shall be conducted under the same requirements per an NFRC 102 test and surface thermocouples placed as directed in NFRC 500-2017.

    • The Condensation Resistance ratings is a value that considers the relative area under condensation at three relative humidity of 30%, 50%, and 70%, which are then normalized, and the degree to which the surface temperatures are below the dew point for the frame and for the glazing are considered.

    • The Condensation Resistance rating specified in the NFRC rating is based on the lower of the frame, center-of-glazing, or edge-of-glazing.

  • ANSI/NFRC 500-2020: Procedure for Determining Fenestration Product Condensation Index Ratings

    • The Condensation Index (CI) can only be determined if the product cannot be simulated. This physical test shall be conducted under the same requirements per an NFRC 102 test and surface thermocouples placed as directed in ANSI/NFRC 500-2020.

    • Determine the three component CI values using the lowest temperature for the frame (CIf), edge-of-glazing (CIe), and center-of-glass (CIc).

    • The whole product CI rating is the lowest CI value from the three calculated components (frame, edge, and center) of the product.

  • FGIA - AAMA 1503: Thermal Transmittance and Condensation Resistance of Windows, Doors and Glazed Wall Sections

    • The AAMA 1503 is conducted in a guarded hot box and the result obtained is the Condensation Resistance Factor (CRF). The CRF value is determined by the lower of the CRF of the average glass temperature  or weighted frame temperature. The greater the CRF, the better the condensation resistance.

    • The frame CRF is calculated based on 14 pre-determined interior temperature locations and 10 additional "roving" thermocouples on the frame. Only 4 of those 10 locations are used as the average roving temperature that is used as weighted factor against the 14 pre-determined frame temperatures.

    • The glass CRF is calculated based on the average glass temperature, combining the edge and center-of-glass thermocouples. There is not an average "edge" temperature versus "center-of-glass."

    • The whole product dimensionless CRF is determined by the lower of the glass and frame CRF.

  • CAN/CSA A440.2/.3: Energy Performance of Windows and Other Fenestration Systems/User Guide to CSA A440.2-04

    • The CSA A440.2/.3 condensation test is a physical testing method only with a scale of 1 to 100 that is called the Temperature Index (I). The higher the Temperature Index of the fenestration system, the better the system is at resisting condensation.

    • Based on the product type, this test method uses the placement of thermocouples along pre-determined locations and four "roving" thermocouples on the frame at predicted coldest points.

    • Three glass temperatures are placed horizontally along a line of 50 mm above each glass sightline of the sill/sash. The average of the three glass temperatures is used for the glass temperature.

    •  The whole product temperature index, I, is the lowest recorded temperature of the frame and average of the three glass temperatures..   

Simulation Standards to Determine Surface Temperatures

Fenestration & Glazing Industry Alliance (FGIA): AAMA 501.9: Surface Temperature Assessment for Condensation Evaluation of Exterior Wall Systems.

  • A standard procedure for the measurement of surface's temperatures to be used in the condensation evaluation of exterior walls under laboratory conditions. The assessment can be used to evaluate the potential for interior condensation formation under wintertime conditions only.

  • AAMA 501.9 is used to measure temperatures on the interior surface of the wall at designated exterior and interior ambient air temperatures to evaluate the potential for interior condensation formation under wintertime conditional only. 

  • This standard does not replace AAMA 1503.

Fenestration and Glazing Industry Alliance (FGIA): AAMA 515-19, Voluntary Procedure for Determination of Fenestration Surface Temperatures by THERM Finite Element Modeling

  • This simulation method uses THERM to ascertain interior surface temperatures of fenestration non-residential windows, terrace and patio doors, curtain wall, storefront, and entrances. This voluntary procedure helps designers determine what temperatures to use when running a project-specific condensation analysis.

  • This standard requires the simulator to obtain the temperatures at the interior frame surface and glass surface (25mm [1 in] above the glass-to-frame junction). The temperature locations are equivalent to NFRC's Condensation Index (CI). 

Organizations Collaborating

  • The Fenestration and Glazing Industry Alliance (FGIA) intends to review AAMA 1503 to determine the necessity to include a calculation for Condensation Index and therefore updating the frame and glass thermocouples' placement on the frame and glass to be in alignment with the NFRC Condensation Index locations.

  • The CSA Group (formerly the Canadian Standards Association) intends to re-evaluate the A440.2/.3 test method to change/add the glass surface thermocouple placement to be aligned with the NFRC Condensation Index approach of 25 mm (1 in) above the glass/frame junction. CSA is also working to revise A440.2/.3 to introduce a simulation method for condensation that is similar to the NFRC Condensation Index rating.

 
 
 
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