Unveiling the Standards of Building Energy Performance: EDGE and Beyond

In the realm of green buildings, assessing energy performance is crucial. Two key methods, the Simplified Hourly Dynamic Calculation Method based on ISO 13790 and European CEN standards (used in EDGE), and the Degree-Day Method, help analyze energy consumption in buildings.

The EDGE Method: ISO 13790 and Thermal Network Models

EDGE, a green building certification program, utilizes a monthly quasi-steady-state calculation method based on the ISO 13790 and European CEN standards. This method estimates the annual energy use for space heating and cooling of a building.Assessing the energy performance of buildings is crucial for sustainability and efficient resource utilization. Leading certification systems like EDGE (Excellence in Design for Greater Efficiencies) play a vital role in this domain. But what standards underpin the calculations used by EDGE and other systems? This article delves into the intricacies of the ISO 13790 standard and its role in calculating heating and cooling demand, exploring 5R1C and 4R1C thermal network models, and comparing it with the degree-day method.

EDGE and the Path to Efficient Buildings

EDGE is a globally recognized green building certification system focused on emerging markets. It provides a framework for designing and constructing resource-efficient buildings, promoting sustainable practices and reducing environmental impact. At the core of EDGE lies its rigorous performance evaluation process, which relies on internationally recognized standards like ISO 13790.

ISO 13790: The Backbone of Building Energy Calculations

At the heart of EDGE's calculations lies the ISO 13790 standard. This standard provides methods for assessing the annual energy use for space heating and cooling of buildings. It introduces a simplified building model called the 5R1C thermal network model.

ISO 13790:2008 establishes calculation methods for assessing the annual energy use for space heating and cooling of residential and non-residential buildings. It presents a simplified building model called the 5R1C thermal network model, utilizing five thermal resistances and one thermal capacity to analyze transient thermal behavior.

Beyond Annual Energy Use: Capabilities of ISO 13790

The standard encompasses calculations for various aspects beyond annual energy use:

• Heat Loss Calculations: Estimating the heat losses of a building maintained at a constant internal temperature.
• Annual Heat Requirements: Determining the annual heat required to maintain specific set-point temperatures inside.
• Heating System Energy Consumption: Evaluating the annual energy consumption of the building's heating system for space heating.

5R1C Thermal Network Model: Simplicity Meets Efficiency

The 5R1C model offers several advantages:

• Simplicity: It requires minimal data and calculations, making it user-friendly and accessible.
• Low computational resources: It can be implemented using basic programming languages, reducing computational strain.
• Accuracy: Despite its simplicity, the model provides accurate results for annual energy consumption calculations.

4R1C Model: Enhanced Accuracy for Specific Cases

The ISO 13790 standard also introduces the 4R1C thermal network model, a modified version of the 5R1C model. This variant incorporates an additional ventilation heat flux, making it particularly suitable for situations where ventilation plays a significant role in energy consumption.

Beyond 5R1C and 4R1C: A Comprehensive Standard

ISO 13790 encompasses a comprehensive set of calculations, including:

• Heat loss determination: Calculating the heat lost by a building when maintained at a constant internal temperature.
• Annual heating requirement estimation: Estimating the annual energy needed to maintain desired set-point temperatures.
• Space heating energy consumption evaluation: Analyzing the annual energy consumption of the building's heating system.

The Degree-Day Method: An Alternative Approach

The degree-day method is another prevalent technique for analyzing building energy consumption. This method estimates daily heat consumption by summing the differences between the outdoor temperature and a base temperature over a specific period.

The Degree-Day Method offers a different perspective on energy consumption. This method estimates the daily heat consumption by summing the differences between the outdoor temperature and a base temperature (typically the temperature at which heating begins) over a defined period.

Choosing the Right Tool for the Job

The choice between ISO 13790 and the degree-day method depends on several factors:

• Project complexity: For detailed analysis of complex buildings, ISO 13790 offers superior accuracy.
• Data availability: If limited data is available, the degree-day method might be a simpler option.
• Project scope: If the focus is solely on space heating and a quick estimate is sufficient, the degree-day method could be adequate.

The choice between these methods depends on specific needs and project requirements.

• EDGE: Ideal for projects seeking a standardized, globally recognized approach with a focus on simplicity and efficiency.
• Degree-Day Method: Suitable for preliminary assessments and estimations, particularly in regions with well-defined base temperatures.

Delving Deep into the Calculation Method:

The EDGE standard's calculation method employs the degree-day method to estimate the daily heat consumption. This method works by summing the differences between the outdoor temperature and a base temperature over a defined period of time. The base temperature represents the indoor temperature at which no heating or cooling is necessary.

For example, if the base temperature is 20°C, and the average daily temperature for a specific month is 15°C, then the degree-days for that month would be 5 (20°C - 15°C). The higher the degree-day value, the more heat required to maintain a comfortable indoor temperature.

Simplifying Building Model: 5R1C and 4R1C Thermal Network Models

The ISO 13790 standard, which serves as the foundation for the EDGE calculation method, introduces a simplified building model called the 5R1C thermal network model. This model utilizes five thermal resistances (R) and one thermal capacity (C) to represent the transient thermal behavior of buildings. It is a relatively straightforward model that doesn't require extensive computational resources and can be implemented using common programming languages.

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5R1C Thermal Network Model

The 5R1C model represents the building envelope as a series of resistances to heat flow, with the indoor air mass represented by the single thermal capacity. Heat transfer between the indoor and outdoor environments occurs through the thermal resistances.

However, the ISO 13790 standard also offers a modified version of this model known as the 4R1C thermal network model. In this variation, an extra ventilation heat flux is included in the model's structure. This allows for a more accurate representation of the impact of ventilation on the building's energy consumption.

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4R1C Thermal Network Model

Calculations for Comprehensive Analysis:

The ISO 13790 standard goes beyond the basic 5R1C and 4R1C models by providing calculations for various aspects of building energy performance, including:

• Determining the heat losses of a building when heated to a constant internal temperature.
• Estimating the annual heat required to maintain specific set-point temperatures inside the building.
• Evaluating the annual energy consumption of the building's heating system for space heating purposes.

Benefits of the EDGE Standard:

The EDGE standard offers several advantages over other building energy performance standards, including:

• Simplicity:?The EDGE method is relatively easy to understand and implement, even for those with limited technical expertise.
• Transparency:?The standard provides clear and concise documentation of the calculation method, allowing for easy verification of results.
• Accuracy:?The quasi-steady-state approach used in the EDGE method provides accurate results for most buildings, especially in regions with moderate climates.
• Cost-effectiveness:?The EDGE standard is free to use, making it accessible to a wide range of stakeholders in the building industry.

Additional Insights:

• The 5R1C model is widely used due to its ease of implementation and computational efficiency.
• The 4R1C model is increasingly being adopted for projects requiring higher accuracy, especially those with significant ventilation rates.
• Integrating both methods can provide a comprehensive understanding of energy consumption and inform more effective energy management strategies.?

Conclusion: Building a Sustainable Future One Calculation at a Time

Understanding the standards and methods behind building energy performance calculations is crucial for designing and constructing truly sustainable buildings. The ISO 13790 standard serves as a valuable tool, providing accurate and reliable results for assessing energy consumption. By utilizing such standards and methods, we can collectively contribute to a future where energy-efficient buildings become the norm, paving the way for a more sustainable future.

Sharing this information can help promote more sustainable and energy-efficient buildings. Let's continue the conversation about building performance and create a greener future together!