Energy consumption calculations of buildings

Group 4B:Bergold, Kajander, Leppä,

Niemeläinen, Pesonen

1. Background2. Purpose & Origin3. Scope & Methods4. Energy consumption calculations method and factors5. Calculation process6. Calculations and factors7. Tools8. Examples9. International comparison10.Comments

Agenda

Background• Energy consumption of a building in life cycle scale:

• 10-20% embodied energy• 80-90% operational energy

• Main focus in lowering operational energy by e.g.• better thermal insulation• energy efficient HVAC machinery• utilization of naturally occurring heat and light• installation of solar panels, wind turbines

• On average, heating energy requirement for an old building 5x higher than for a new building

• Recent EU directives require:• Energy certificate for new buildings since 2002• All new buildings must be nearly self-sufficient by 2020

• Legislation, such as EU directive from 2002, EU 20-20-20 etc.

• Ability to make better decisions in the design phase of project

• Reduced costs in the life cycle of building

• Possibility to compare and evaluate different solutions

Purpose and origin(for calculating energy consumption)

• Key focus is on the Finnish official method

• We cover just factors that are bound with the actual energy need: building’s size, materials, structure and technical systems (e.g. no ecology-political multipliers for energy sources )

• As the given task was about calculating energy consumption, e.g. not costs, the economical calculations or comparisons, or energy consumption of materials/building phase are not covered

• For new buildings, the official document is E statement, not E certificate.

As factors impacting the energy consumption calculations are similar, the report doesn’t include a study about E statement.

Scope & Methods

Energy consumption calculations method and factors

Purchased energy

Solar radiation (windows)Users’ warming impact

Thermal losses (inc. also leaks and cold bridges)

Heating energy

Cooling energy electricity

Renewable in-house energy sources

Technical systems- system losses - conversion factors

Building’s energy need for -heating -cooling - ventilation-(warm) water -lightning - users’

equipment

• When planning a new building, the design program provides most of the base values for the calculations, like heated net area of building and the area of the building shell, and the U-values of different structures.

• In case of an old building, the determination of the base values would need not just old design documents but also an inspection of the building.

• The efficiency values of technical systems (heating, cooling, ventilation etc) are determined by technical documents; for older systems, of an old building, default values are used if documents are not available

• Calculations are easily done by tools after the base values are determined

Calculations process

• Consumption is told as annual energy need e.g. purchased energy (kWh) per building’s heated net area (square meters).

• Buildings net area is impacting also into the assumptions of the amount of users: and thus how much they consume electricity and warm water, and how much users provide energy. Non-heated areas are not calculated

• Net area is calculated corner to corner inside of outer walls(or the gross area minus the area of external walls)

Calculations & factors / size and shape

• The bigger the building’s shell area is, the more probable are thermal losses because of cold bridges and air leaks

• Thermal transmittance is bound with the shell’s area and structures

• Building’s outer shell’s materials and dimensions are impacting thermal conductivity of the structure (U-value)

Calculations & factors: size and shape and structure of the shell

• Relatively easy way to improve the energy efficiency of the shell is to add insulation

• Solar radiation trough windows is taken account• The type of windows has impact• The direction of windows would be impacting too• Renewable energy sources are taken account as decreasing

the need of the purchased energy– Solar panels– Heat pumps

Calculations & factors

• Ventilation (note: the typical standard use of building):– Usage times– Air quantities– Efficiency values– Vs Demand controlled ventilation

• Heating net need for heating air• Heat recovery, if relevant

• Supply air heating is calculated as part of heating energy consumption

Calculations & factors

• Heating systems- All examined and calculated separately

• Heated water

• Electricity- Auxiliary equipment- Consumers’ devices and lightning

Calculations & factors

• Cooling systems- Only if building have cooling- If is limited only a few areas, can be left out

• Specific cases- Floor heating in wet rooms- Heat-storing fireplace

Calculations & factors

• Choice of tools relies on the task of calculation• Four categories of tools:

• Screening tools• Architectural design tools• Engineering design tools• Economic assessment tools

• IDA ICE, SBEM, EnerCalC, Modelica

1. Divide Building in different

zones

2. Calculate Each Zone

3. Select HVAC Systems

4. Calculate Energy

Consumption

5. Information of Electric Utility and Fuel Rate

6. Calculate Energy Costs

Energy consumption calculation tools

• The Finnish authoritieshave published an Excel-template for energy consumption calculations and for providing the energy certificate

• The template is available free at website:http://www.ymparisto.fi/fi-FI/Rakentaminen/Rakennuksen_energia_ja_ekotehokkuus/Rakennuksen_energiatodistus/Energiatodistuslomakkeet

Calculation tools

• Rakennustieto Oy is selling a commercial tool MX6 Energia that is In practise used with excel.

• Includes features to compare and visualize different scenarios

• Might help early phase of design work in case of having alternative ideas for renovating of an older building with an existing energy consumption level.

• However, in case of planning a new building, or during later phase of planning work, values could be calculated by the actual design tool

Calculation tools

Further calculation examples presented in the theses of

• Tolonen (2012)• Holmi (2013)

Examples

• ISO standards – an international standard for energy calculation. ISO 12655:2013

• Variation in base values for variants.• Sweden: four different climate zones for

energy regulations.• Norway: calculation method varies between

different building types

International comparison

• If calculating alternative investments, the building’s location and weather conditions are to be considered too. (Ministry guideline is assuming a building to locate in Vantaa.)

• In practise the consumption is not constant but bound with users too. In case of being property owner, possibilities to impact the energy consumption of users might be useful to consider, and consumption bound incentives.

• How can the influence of user be taken into account in the energy consumption calculations?

Notes and comments