Overview

The Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs, know as the ASHRAE 140 standard, was developed to introduce a specific standard for simulation software to be tested against. 

In order to achieve compliance, building energy simulation software has to prove that with a given set of inputs, which include geometry, location, weather conditions, building construction(s), internal conditions, operating schedules, etc., the software is capable of producing a set of required outputs in the expected and reasonable range compared to other energy simulation programs. It is very important to note, results are not compared to a benchmark (baseline) of energy simulation software results, as such a thing does not exist. Instead the results are compared to the results of other software packages tested under the same conditions. 

The full documentation of the ASHRAE 140 standard can be purchased from the ASHRAE website. 

The purpose of this article is to describe the testing procedures and the requirements needed for the Sefaira product to fully comply with this standard.

Testing Procedure(s)

There are two types of testing procedures in the standard, Class I and Class II testing procedure. Software vendors are left to choose a testing procedure they think is more applicable for their software. Like Sefaira, most software vendors have chosen Class I testing procedure.

Class I testing procedure

Class I testing procedure includes the following group of tests and cases:

 BASE Case (Case 600, Section 5.2.1 of Standard)

• BASIC Tests (Section 5.2.2 of Standard)
• Low mass tests (Cases 610 to 650),
• High mass tests (Cases 900 to 960)
• Free float tests (Cases 600FF, 650FF, 900FF and 950FF)
• IN-DEPTH tests (Section 5.2.3 of Standard)
• Cases 195 to 320
• Cases 395 to 440
• Cases 800 and 810

Note: Total number of cases for testing in Class I testing procedure is 39, so when we say in the example above “Cases 610 to 650” this doesn’t mean there are 40 cases between 610 and 650. In this particular situation, cases in this range are 610, 620, 630, 640 and 650.

Testing cases are performed on a very simple model with an area of 48m2, one zone (in most cases), single story building (room) in Denver Colorado. There are a total of five variations of the building geometry and they are all defined in cases 600, 610, 620, 630 and 960. All other test cases are using one of the five geometries as a base.

As we can see, the first four geometry cases have varying glazing orientation and exterior shading in one zone, but case 960 is set up to have two zones (a back-zone and a sunzone) separated by a common interior wall.

Each testing case has a specific set of inputs and requirements the simulation software is expected to be able to provide. As an example, let’s look at the full descriptions of inputs required for the Case 600 test.

Envelope:

Infiltration: 0.5 air change/hour

Internal Load: 200 W continuous, 60% radiative, 40% convective, 100% sensible

Mechanical System: 100% convective air system, 100% efficient with no duct losses and no capacity limitation, no latent heat extraction, non-proportional-type dual setpoint thermostat with deadband, heating <20°C, cooling >27°C 

Soil Temperature: 10°C continuous

Important:

Most of the inputs are very detailed and specific. Sefaira has some limitations around the description of inputs, which means the test cannot be mimic exactly. 

The following table outlines the majority of input requirements for all testing cases, as well as the capability of Sefaira providing those inputs and settings. 

Notes:

1. Standards requires that constructions are formed by following a very specific list of material layers include specific thermal and physical properties. In addition, in depth analysis cases also require very specific setting for finishing layers, i.e. Exterior shortwave absorbance, Combined Radiative and Convective Surface Coefficients, Infrared emittance, etc. Sefaira currently forms material layers based on the required U-value and the type of construction varying their thickness and conductivity of each layer to meet both U-value and the construction thermal mass (low mass, high mass, etc.) requirements.
2. Standards requires the use of windows with a very specific thermal and optical properties. Sefaira is using a simplified version that requires three inputs: U-value, SHGC and Visual Transmittance
3. Tests require Ideal Convective HVAC System (Ideal Loads in E+) which Sefaira currently does not support.

Testing Results

As mentioned above, energy simulation software will comply with the ASHRAE 140 standard if the software is capable of producing results in the reasonable range compared other energy simulation programs. The types of results being assed for software compliance are:

• Annual Heating and Cooling Loads
• Annual Heating and Cooling Peak Capacities
• Heating and Cooling Loads on a specific day (January 4th)
• Hourly Solar Incident on the Exterior Wall on a specific day (March 5th & July 27th)
• Minimum and Maximum Annual Hourly Zone Temperature for test cases without HVAC system
• Minimum and Maximum Annual Hourly Zone Temperature for test cases without HVAC system on a specific day (January 4th and July 27th)

The following software packages have already been tested: ESP, BLAST, DOE2.1D, SRES/SUN, SERIRES, S3PAS, TRNSYS, TASE & ENERGY PLUS.

Testing

Despite the previously mentioned limitations Sefaira has matching the exact required input data, we still perform a series of Case I tests to compare our results with the acceptable range. The main focus of testing is 600 and 900 case tests with the exception of the tests which include night mechanical ventilation and zone free floating temperature tests.

600 Series of Tests

A 600 series of tests is referred to as “low mass building” tests. The following table reviews Sefaira inputs vs Required Inputs: 

Inputs

The following table shows the results generated by Sefaira are extremely close when compared to other software results.

Annual Heating Loads (MWh)

Annual Cooling Loads (MWh)

Annual Peak Heating Load (kW)

Annual Peak Cooling Load (kW)

Case 900 Test

A 900 series test is identical to the 600 series, except the floor and wall construction is of a heavy weight.

Unlike the 600 series, 900 series tests using Sefaira are slightly higher when compared to other software. This is due to the exterior walls and floors having a higher mass value (the Sefaira wall value is 225 kg/m² vs required 165 kg/m²)

Annual Heating Loads (MWh)

Annual Cooling Loads (MWh)

Annual Peak Heating Load (kW)

Annual Peak Cooling Load (kW)

If you have any comments or questions, please check out the SketchUp + Sefaira Forum or contact support@sefaira.com