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About energy calculations |
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There is some generic methods that is often used to calculate a buildings energy consumption.
Key values or square meter method
The method builds on using key values often based on energy use per square meter floor area. This method can work if you have a homogeneous set of buildings. The method is simple but can't predict any accuracy. The result is often that focus is concentrated on the building with highest square meter consumptions. Not where the potential is. Older buildings often have high square meter consumption but they are expensive to fix. Newer building often consume more energy than they should and they are also often cheap and easy to fix.
The square meter method is acceptable only IF there is thorough analysis about a specific set of homogeneous buildings and the way they operate. Never use this method in any other way.
Degree day method
The method consist of a energy transmission calculation done with a suitable interval along a degree day curve. The accuracy is often better than the square meter method but it doesn't take into account heat accumulation and infiltration. The result is therefore not satisfactory because of the lack of accuracy and needs often to be complemented with other methods.
Reactor and corrections factor.
You use different types of reductions or multiplication factors instead of real models to calculate the energy utilization. This method can result in various threshold effects and you should be very cautions how this is implemented. For some statical functions this method can be fruitful. CEN-832 uses utilization factor instead of mathematical models because of this CEN can never be accurate.
Calculation of a physical model.
The most exact generic way to calculate energy consumption if internal heat loads, solar radiation, wind velocity, internal thermals and external climate from real weather data etc are considered. The result is determined on how well the program handles all components. It is hard to find good software for modern or old buildings. It is typically common with a calculation error between 20-50% especially in modern buildings with large windows. VIP+ has a expected accuracy that is normally within 3-5%.
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EnergyCalculations 