Monthly Energy Balance Building Model

Building heating/cooling demand calculation with the standardised monthly energy balance.

Overview

Origin

German norm DIN V 18599: Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting - Part2: Net energy demand for heating and cooling of bulding zones.

Similar international norm: ISO 13790. Energy performance of buildings – Calculation of energy use for space heating and cooling

Short description

This is a statical thermal model, calculating the overall energy balance of buildings with a monthly resolution. The energy balance includes all heat sources (intern gains, solar gains...) and sinks (transmission, ventilation...) within the building zone, its results are the monthly space heating and cooling demand.

The described algorithm is applicable to the calculation of energy balances for:

• residential buildings and non-residential buildings;
• planned or new building construction and existing buildings.
• multi-zone and mono-zone building model (in Jan. 2016, SimStadt only uses it for monozone model)

In case of building presenting a unique usage (for instance: residential or office building), a representation of the building as monozone model will be particularly adapted to this algorithm. In case of building with multi-usage (for instance: retail in ground floor and residential in upper floors), the building must be splitted in specific zones corresponding to each usage.

Required inputs and their preparation

Building Parameters

Parameter	Description	Unit/Type	Source
Per building
BuildingUnitID	KeyID of the building	[Num/String]	in CityGML file
vBrutto	Brutto heated volume of the building	[m3]	BuildingPhysicsPreprocessing
heatedArea	Energy reference area of the building	[m2]	BuildingPhysicsPreprocessing
cp_m2	effective thermal capacity of the building	[J/K.m2]	BuildingPhysicsPreprocessing
atb	Ratio of indirectly heated areas to the total area	[0-0.5]	BuildingPhysicsPreprocessing
StoreysAboveGround	Number of full-storeys above ground	Integer	BuildingPhysicsPreprocessing
BasementHeating	Configuration of the lower part (basement) of the building	CodeList{NO_ROOM; NOT_HEATED; HEATED}	BuildingPhysicsPreprocessing
AtticHeating	Configuration of the upper part (attic) of the building	CodeList{NO_ROOM; NOT_HEATED; HEATED}	BuildingPhysicsPreprocessing
Uwb	Thermal bridge additional Uvalue	[W/m2.K]	BuildingPhysicsPreprocessing
Per Usage Zone of the building
Nair	Air change rate per hour	[vol/h]	BuildingUsagePreprocessing
qi	Mean intern gains	[W/m2]	BuildingUsagePreprocessing
TsetHeat	Set-point temperature for heating	[°C]	BuildingUsagePreprocessing
TsetbackHeat	Set-back temperature for heating	[°C]	BuildingUsagePreprocessing
TsetCool	Set-point temperature for cooling	[°C]	BuildingUsagePreprocessing
h_use	Daily operating hours of heating systems	[0-24]	BuildingUsagePreprocessing
d_use	Annual operating days of heating systems	[0-365]	BuildingUsagePreprocessing
Per outside surface of the building
SurfaceType	Type of the building surface	['floor','wall,'roof']	for LOD2: in CityGML file, for LOD1: CityDoctor
surfaceArea	Thermal boundary area above ground	[m2]	BuildingPhysicsPreprocessing
UValue	heat transmission coefficient	[W/m2.K]	BuildingPhysicsPreprocessing
shortWaveReflectance	short-wave reflectance	[0-1]	BuildingPhysicsPreprocessing
WindowAreaRatio	Window Area inclusive frame	[0-1]	BuildingPhysicsPreprocessing
Uwindow	mean U-Value of transparent area	[W/m2.K]	BuildingPhysicsPreprocessing
Gwindow	mean G-Value of transparent area	]0-1]	BuildingPhysicsPreprocessing
WindowFrameRatio	Proportion of window frame area (opaque) / window total area	]0-1]	BuildingPhysicsPreprocessing

Note:

• All outputs of the BuildingPhysicsPreprocessor are used as inputs of the Monthly Energy Balance.
• All outputs of the BuildingUsagePreprocessor, excepted the OccupantNumber, the domestic hot water and electrical appliances consumption ratio, are used as inputs of the Monthly Energy Balance.
• In the Energy ADE, excepted the occupantNumber and dhwDemand of the UsageZone (used for the Domestic hot water calculation), the EnergyGenerationSystem and Fuel objects (used for the CO2 emission and primary energy calculation), and the windowOpenableRatio and shadingTypeId of the shellproperties (to be used for cooling demand calculation), all other parameters are used to calculate the building heating demand.
• The relative influences of different inputs are studied in the paper "The influence of data quality on urban heating demand analyses based on 3D city models" for the case study Ludwigsburg. Among the most influential building parameters: the refurbishment status (considered by the window and construction UValues, through the BuildingPhysicsPreprocessor) and the usage properties air change rate and set-point temperatures.

Weather monthly data

Mean Monthly Inputs	Description	Unit	Source
Per site
Tout	Outside Temperature	[°C]	Input database (e.g. Insel, PVGIS, Meteonorm) in WeatherProcessor
Tsky	Sky Temperature	[°C]	WeatherProcessor
Per surface
Irr	Incoming monthly radiation per surface	[W/m²]	RadiationProcessor

Simulation parameters

ConsumerBehaviourType [Code list]

• Standard: the sapce heating demand correspond exactly to the results of the DIN V 18599-2
• IWU_Fnutzung: The space heating demand is corrected, through the introduction of an empirical user-factor (Fnutzung) developed by the Institut für Umwelt (IWU, 2003). This user-factor takes into account the fact that high energy bills often induce the tenant to only partially heat, to reduce temperature set-points and thus save energy. It depends directly on the thermal state of the building envelope. It readjusts the heating set-point temperature, in the same way as the partial heating reduction factor, varying between 0.85 for old unrefurbished buildings, to 1.1 for Passive house.

DIN V 18599-2 Algorithm

Pre-calculations

• In the case of a mixed usage building (building or building part with several usage zones), the usage zone properties are averaged previously to the energy balance calculation, weighted respectively with their zone area.
• The precalculation of the mean Uvalue (i.e. heat transmission coefficient) is realized previously in the function void calculateMeanUValue() of the class eu.simstadt.buildingphysics.preproc/BuildingPhysicsPreprocessor.java
  

Core algorithm

The Monthly energy balance algorithm is implemented in the class eu.simstadt.monthlyEnergyBalance/MonthlyBalanceDIN18599.java.
Summary of the equations of this monthly energy balance calculation: Details_DIN_18599-2.
It is fully described in the German norm DIN V 18599: Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting - Part2: Net energy demand for heating and cooling of bulding zones.