Energy use of buildings

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Question

How to model the use of energy of buildings based on either annual consumption per floor area, or energy efficiency per floor area per indoor-outdoor temperature difference?

Answer

Example of consumer energy demand calculations: energy need in Helsinki from the assessment Helsinki energy decision 2015.

An example code for fetching and using the variables.

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Rationale

Input

Variables needed to calculate the EnergyConsumerDemand. Note that there are several different methods available, and temperature data is not needed in an annual energy version.
Dependencies Measure Indices Missing data
buildings (from the model). Floor area of the building stock to be heated Typical indices: Building, Heating, Efficiency, Renovation You can use value 1 to calculate energy need per 1 m2 floor area.
temperene (fairly generic data for a given cultural and climatic area, e.g. from Energy use of buildings) Energy need per floor area and indoor-outdoor temperature difference (W /m2 /K) Required indices: Consumable, Fuel (Commodity). Typical indices: Building, Heating. if this data is missing, you can only calculate building stock but nothing further.
nontemperene (fairly generic data for a given cultural and climatic area, e.g. from Energy use of buildings) Energy need for hot water and other non-temperature-dependent activities Required indices: Consumable, Fuel (Commodity). Use 0 to calculate energy demand excluding non-heating energy use.
temperatures (location-specific data) Average outdoor temperatures for particular temperature bins. Reuired indices: Temperature. If missing, use the annual energy version.
temperdays (location-specific data) Number of days per year for particular temperature bins. Required indices: Temperature. If missing, use the annual energy version.
efficiencyRatio (fairly generic data for a cultural and climatic area, e.g. from Energy use of buildings) Relative energy consumption compared with the efficiency group Old. Required indices: Efficiency. Typical indices: Time, Building. If no data, use 1 as default.
renovationRatio (fairly generic data for a cultural and climatic area, e.g. from Energy use of buildings) Relative energy consumption compared with the Renovation location None. Required indices: Renovation. Typical indices: Building. If no data, use 1 as default.


Annual calculations

The code below assumes annual energy consumption factors per floor area (kWh /m2 /a). No temperature data is needed.

Q_{e,r} = \sum_b B_{b,e,r} F_b E_e R_r,

where

  • Q = Energy used for heating and cooling (kWh /a)
  • B = floor area of a building stock indexed by renovation and efficiency (m2)
  • F = energy consumption factor (kWh / m2 /a)
  • E = relative efficiency of a building stock based on energy class when built (no unit)
  • R = relative efficiency of a building stock based on energy class after renovated (no unit)
  • indices used:
    • b = building type
    • e = efficiency class of building
    • r = renovation class of building

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Temperature-dependent calculations

The code below assumes energy consumption factors relative to floor area (W /m2 /K). Local temperature data must be given in either individual or aggregated way. Individual way has temperature data for all timepoints (e.g. days or hours) of the given year, and heatingTime = 1. Aggregated way has a specific Temperature index (e.g. very cold, cold, cool etc) in both ovariables temperature and heatingTime. The ovariable temperature tells what is the actual temperature when it is "very cold", and heatingTime tells how many hours it is "very cold" during the year.

Q_{e,r,t} = \sum_b (B_{b,e,r} U_b (17 - T_t) E_e R_r + W_b) t_t,

where

  • Q = Energy used for heating and cooling (kWh /a)
  • B = floor area of a building stock indexed by renovation and efficiency (m2)
  • U = energy consumption factor per floor area for a building type (W /m2 /K)
  • T = temperature outside (assumes that no heating is needed if outside temperature is 17 degrees Celsius)
  • E = relative efficiency of a building stock based on energy class when built (no unit)
  • R = relative efficiency of a building stock based on energy class after renovated (no unit)
  • W = heating need of hot water (W)
  • t = time spent in a particular outdoor temperature (h /a)
  • indices used:
    • b = building type
    • e = efficiency class of building
    • r = renovation class of building
    • t = ambient temperature class


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Baseline energy consumption

Heat reflects the energy need for heating in situations where the outdoor temperature is below 17 °C. Cooling reflects the cooling need (measured as thermal energy, not electricity!) in situations where the outdoor temperature is above 24 °C. This is not a U value, because it is about energy use per floor area, not about heat loss through building structures per m2. For estimating temperene, we take the total energy consumption in Helsinki and divide that with the total floor area and average temperature difference, see Helsinki energy consumption#U values based on overall data.

Energy use per area and temperature difference(W /K /m2)
ObsConsumableFuelEnergy flowDescription
1HeatingHeat1.66See Helsinki energy consumption: 6921.65/24/365/38990000/(17-4.8)*1E+9
2District coolingCooling0.3Guesswork. This uses centralised system.
3Electric coolingElectricity0.3Guesswork. This uses apartment-specific appliances.

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Temperature-independent energy consumption per floor area.

Temperature-independent energy use per area(W /m2)
ObsConsumableFuelEnergy intensityDescription
1Consumer electricityElectricity5Assumes 50 kWh /m2 /a (see below)
2Hot waterHeat4Assumes that hot water is ca. 20 % of energy need of heating: 6921.65/24/365/38990000*1E+9*0.2

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Baseline energy consumption per area unit(kWh/m2/a)
ObsBuildingHeatingHeatUser electricityTotal electricityYearDescription
1Detached housesDistrict134.7450184.742010Calculated from energy company´s data; Pöyry
2Detached housesElectricity130501802010Energiapolar; Pöyry
3Detached housesOil134.7450502010Pöyry. Efficiency 90-95% (energiatehokaskoti.fi).
4Detached housesWood134.7450502010Assumption. Efficiency of good kettles 80%(energiatehokaskoti.fi).
5Detached housesGeothermal4050902010Assumption
6Row houses168.8873.573.52010Calculated from energy company´s data. Based on district
7Apartment houses172.3141.741.72010Calculated from energy company´s data. Based on district
8Commercial161.82229.6229.62010Calculated from energy company´s data. Based on district
9Offices161.0793.193.12010Calculated from energy company´s data. Based on district
10Health and social sector214.97122.81122.812010Calculated from energy company´s data. Based on district
11Public165.47110.4110.42010Calculated from energy company´s data. Based on district
12Sports121.3885.985.92010Calculated from energy company´s data. Based on district
13Educational170116.4116.42010Calculated from energy company´s data. Based on district
14Industrial168.44212.4212.42010Calculated from energy company´s data. Based on district
15Leisure houses2.413.42010Calculated from energy company´s data. Based on electricity
16Other138.14170.3170.32010Calculated from energy company´s data
17Non-residential buildingsNo energy source113Urgenche data for Basel
18Non-residential buildingsHeating oil113Urgenche data for Basel
19Non-residential buildingsCoal113Urgenche data for Basel
20Non-residential buildingsGas113Urgenche data for Basel
21Non-residential buildingsElectricity113Urgenche data for Basel
22Non-residential buildingsWood113Urgenche data for Basel
23Non-residential buildingsCentrifuge, hydro-extractor113Urgenche data for Basel
24Non-residential buildingsSolar heater/ collector113Urgenche data for Basel
25Non-residential buildingsLong-distance heating113Urgenche data for Basel
26Non-residential buildingsOther sources113Urgenche data for Basel
27Special constructions86-106Urgenche data for Basel (Mixed use)
28Single-family houses69Urgenche data for Basel
29Multiple-family houses54-106Urgenche data for Basel
30Residential buildings with subsidiary use86-106Urgenche data for Basel
31Buildings with partial residential use86-106Urgenche data for Basel


  • Pöyry 2011. [1]
  • Energiapolar. [2]
  • Energiatehokaskoti.fi/Öljylämmitys [3]

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Energy efficiency in heating

What is the relative energy consumption of different efficiency classes compared with Old? This table tells that with some background information about heat (in kWh/m2/a), electricity, and water consumption.

Energy use by energy class of building(ratio)
ObsEfficiencyRatioHeatUser electricityWaterDescription
1Traditional1.2-1.4200Guesstimate
2Old115030Pöyry 2011 s.28
3New0.4-0.5705040Pöyry 2011 s.32 (2010 SRMK)
4Low-energy0.2-0.25355040Personal communication
5Passive0.1-0.1617.5 - 255040Pöyry 2011 s.33; Personal communication

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Energy efficiency of buildings when they are built(%)
ObsEfficiencyConstructedFractionDescription
1Traditional1800-1944100
2Old1945-1994100
3New1995-2019100
4New2020-202910-20
5Low-energy2020-2029The rest of energy class
6Passive2020-202925-35
7New2030-20395-10
8Low-energy2030-203920-50
9Passive2030-2039The rest of energy class
10New2040-20700-5
11Low-energy2040-207010-30
12Passive2040-2070The rest of energy class
  • Old: old buildings to be renovated (or in need of renovation)
  • New: normal new buildings (no current need of renovation)
  • Low-energy: buildings consuming about half of the energy of a new building
  • Passive: buildings consuming a quarter or less of the energy of a new building
  • Chinese green building system: [3] [4]

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Impact of renovations

Energy saving potential of different renovations(ratio,kWh/m2/a)
ObsRenovationRelativeAbsoluteRenovation detailsDescription
1Windows0.8525New windows and doorsPöyry 2011
2Technical systems0.5075New windows, sealing of building's sheath, improvement of building's technical systemsPöyry 2011
3Sheath reform0.35100New windows, sealing of building's sheath, improvement of building's technical systems, significant reform of building's sheathPöyry 2011
4General0.85-General renovationPöyry 2011
5None10Renovation not done

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Data not used

This section contains data that are relevant for the topic but are not used in the actual method calculations.

----#: . Note that below numbers are very preliminary (esp. electricity)! (type: truth, paradigm: science view) --Marjo 16:49, 13 March 2013 (EET)

Baseline energy consumption per volume unit(kWh/m3/a)
ObsBuildingHeatingHeatUser electricityYearDescription
1Detached housesDistrict42.1515.672010Calculated from energy company´s data; Energiapolar
2Detached housesElectricity40.6615.672010Energiapolar
3Detached housesOil42.1515.672010Energiapolar
4Detached housesWood42.1515.672010Assumption
5Detached housesGeothermal18.5615.672010Assumption
6Row housesDistrict53.2523.162010From energy company
7Apartment housesDistrict49.211.92010From energy company
8CommercialDistrict28.6540.642010From energy company
9OfficesDistrict36.3220.992010From energy company
10Health and social sectorDistrict55.231.532010From energy company
11PublicDistrict32.2121.492010From energy company
12SportsDistrict18.37132010From energy company; Electricity value comes from city´s renovation data
13EducationalDistrict40.2327.542010From energy company
14IndustrialDistrict30.5738.552010From energy company
15Leisure housesElectricity0.680.292010From energy company
16OtherDistrict29.8836.832010From energy company

Regulations regarding energy consumption of buildings

Maximum allowed energy consumption per unit (= E-value)(kWh/m2/a)
ObsBuildingYearE-valueDescription
1Detached houses2012 forward204Heated net area <120 m2; Finland´s Environmental Administration
2Row houses2012 forward150Finland´s Environmental Administration
3Apartment houses2012 forward130Finland´s Environmental Administration
4Shops and other commercial buildings2012 forward240Finland´s Environmental Administration
5Offices2012 forward170Finland´s Environmental Administration
6Health and social sector: Hospitals2012 forward450Finland´s Environmental Administration
7Health and social sector: Health care centers etc.2012 forward170Finland´s Environmental Administration
8Public2012 forward240Finland´s Environmental Administration
9Sports2012 forward170Does not apply to swimming- and ice halls; Finland´s Environmental Administration
10Educational2012 forward170Finland´s Environmental Administration
11Industrial2012 forward-E-value must be calculated but there´s no limit for it; Finland´s Environmental Administration
12Leisure buildings2012 forward-E-value must be calculated but there´s no limit for it; Finland´s Environmental Administration
13Other2012 forward-E-value must be calculated but there´s no limit for it; Finland´s Environmental Administration

See also

  • Juhani Heljo, Hannele Laine. Sähkölämmitys ja lämpöpumput sähkönkäyttäjinä ja päästöjen aiheuttajina Suomessa] TTY 2/2005. [5] ←--#: . Contains emission factors etc. May also be used in Emission factors for burning processes. (type: truth, paradigm: science view) --Jouni (talk) 07:38, 18 June 2015 (UTC)
  • Juhani Heljo, Eero Nippala, Harri Nuuttila. Rakennusten energiankulutus ja CO2-ekv päästöt Suomessa. TTY 4/2005. [6]

Keywords

References

  1. Pöyry 2011: Kuopion kasvihuonekaasupäästöjen vähentämismahdollisuudet v 2020 mennessä.
  2. Energiapolar/Arvioi sähkönkulutus[1]
  3. Energiatehokaskoti.fi/Öljylämmitys[2]

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