Benefits of Using IESVE and DesignBuilder for Heat Loss Calculations Compared to BER HLI
- MTS DNC ENERGY CONSULTANTS LIMITED
- Jul 5
- 3 min read
In modern building design, accurate prediction of energy performance is essential. Tools such as IESVE and DesignBuilder allow engineers to carry out advanced thermal modelling and heat loss analysis that go beyond standard compliance methods used in a BER assessment.
This article explains the benefits of using these simulation tools and how their results compare with the BER Heat Loss Indicator (HLI) used in Ireland.
🔍 What Is BER Heat Loss Indicator (HLI)?
In a standard BER assessment, the Heat Loss Indicator (HLI) is used to measure how much heat a building loses per square metre of floor area.
It considers:
Fabric heat losses (walls, roof, floor, windows)
Ventilation heat losses
Thermal bridging (simplified values)
However, BER calculations are standardised and simplified, meaning they are not project-specific and do not allow detailed design optimisation.
💻 What IESVE and DesignBuilder Do Differently
Software such as IESVE and DesignBuilder use dynamic simulation methods to model the building in far greater detail.
They can analyse:
Hourly weather data
Occupancy patterns
Internal heat gains
Solar radiation effects
Airflow and ventilation behaviour
Detailed thermal zoning
This allows engineers to see how a building actually performs in real-world conditions.
📊 Key Benefits of IESVE and DesignBuilder
1️⃣ More Accurate Heat Loss Prediction
Unlike BER, which uses standard assumptions, simulation tools calculate heat loss based on:
Real geometry
Actual material properties
Detailed thermal bridging
Dynamic environmental conditions
This produces a more realistic heat loss profile.
2️⃣ Optimised Heating System Design
The outputs can be directly used for:
Radiator sizing
Underfloor heating design
Heat pump selection
Peak load estimation
This ensures systems are neither oversized nor undersized.
3️⃣ Better Energy Efficiency Decisions
Engineers can test different design options:
Insulation upgrades
Window performance changes
Ventilation strategies
Airtightness improvements
This helps identify the most cost-effective energy improvements.
4️⃣ Supports Low-Energy and NZEB Design
These tools are essential for:
Nearly Zero Energy Buildings (NZEB)
Passive house principles
High-performance commercial buildings
They allow full design optimisation before construction.
⚖️ How Do They Compare to BER HLI?
Although both methods assess heat loss, they serve different purposes:
Feature | BER HLI | IESVE / DesignBuilder |
Purpose | Compliance & certification | Design optimisation |
Detail level | Simplified | Highly detailed |
Weather data | Standard assumptions | Hourly real data |
Occupancy & usage | Fixed assumptions | Dynamic modelling |
Output | BER rating + HLI | Full thermal performance analysis |
🔗 Key Relationship Between Them
While BER HLI provides a standardised compliance metric, results from IESVE and DesignBuilder can be used to:
Validate design assumptions
Improve accuracy of heating load estimates
Inform BER inputs for complex buildings
Optimise performance before certification
In many cases, well-developed simulation models will produce a more refined understanding of heat loss than the standard BER methodology alone.
🧠 Final Thoughts
Using IESVE and DesignBuilder gives engineers and designers a much deeper understanding of building performance compared to traditional BER calculations.
When combined with BER assessments, they provide a powerful workflow:
Early-stage design optimisation
Accurate heat load calculations
Improved energy performance outcomes
Better long-term system efficiency
At MTS DNC Energy Consultants & NEXUS M&E Design, we use both approaches to ensure buildings are compliant, efficient, and optimised for real-world performance.
📍 Disclaimer
The content shared in these posts is intended for informational purposes only and should not be interpreted as design advice, specifications, or a calculation template. For professional guidance or design services, please contact us through our contact form.
