Energy Performance Certificate Glossary
German-context glossary around the Energieausweis (Germany’s Energy Performance Certificate, EPC) and the regulations governing it (GEG, GModG, EPBD, EnEV). Some German legal terms are kept in their original form with an English explanation.
A
Above-ground construction (Hochbau): Building works that extend above the ground surface.
Additional insulation: Supplementary thermal insulation that improves the existing building envelope.
Aerated concrete: Lightweight masonry block with high thermal insulation properties (e.g. Ytong).
Air-source heat pump: Heating system that extracts ambient heat from outdoor air.
Air conditioning: Building services for treating room air, in particular cooling.
Air exchange rate: Number of complete air changes per hour inside a building.
Air-tightness: Measure of how impermeable the building envelope is to uncontrolled air exchange.
Air-tightness test: Verification of a building’s air-tightness, typically via the Blower Door Test.
Ambient heat (Umweltwärme): Thermal energy extracted from ambient air, ground or groundwater (used by heat pumps).
Ancillary costs (Nebenkosten): Energy-related operating costs charged on top of the basic rent.
Annex (Anbau): Additional building part that often differs in construction year and energy performance.
Annual balance: Yearly comparison of energy generation and consumption for a building.
Annual consumption: Energy actually metered over a year.
Annual coefficient of performance (JAZ): Ratio of useful heat to driving energy of a heat pump averaged over a full year.
Annual energy demand: Energy a building needs in one year, expressed in kWh/a.
Annual heating demand: Total heating energy a building needs per year, in kWh/a.
Annual mean temperature: Average outdoor temperature of a year, relevant for energy demand calculations.
Annual primary energy demand: Total primary energy a building requires per year.
Annual useful energy: Energy effectively available inside the building over one year.
Annual utilisation rate: Ratio of energy actually used to energy supplied over a year.
Ashlar masonry: Masonry of regularly shaped stones, which influences thermal performance.
Auxiliary energy: Electrical energy used to operate building services (pumps, fans, controls) but not directly for heat generation.
Avoidable heat losses: Energy losses that can be reduced by renovation measures.
B
Balancing method (Bilanzierungsmethode): Procedure for determining the energy demand in the certificate – since 2024 the GEG prescribes DIN V 18599.
Balancing period (Bilanzierungszeitraum): Period over which energy demand or consumption is recorded.
Basement (Untergeschoss): Underground storey of a building, e.g. cellar or underground garage.
Basement ceiling (Kellerdecke): Slab between heated living space and an unheated cellar.
Biomass: Renewable energy sources such as wood.
Biotreppe (Bio-stairway): Stepped requirement of the GModG obliging new gas, oil and LPG boilers to use a rising share of climate-friendly fuels (biomethane, hydrogen, bio-oil): 10 % from 2029, 15 % from 2030, 30 % from 2035 and 60 % from 2040.
Blinds (Jalousie): Sun-shading device that also reduces heat losses through windows.
Blower Door Test: Standardised procedure to verify the air-tightness of a building.
Boiler (Heizkessel): Core of a heating system in which heat is generated by combustion and transferred to a heat carrier.
Buffer tank: Storage tank that buffers surplus heat in a heating system.
Building: Structure with at least one dwelling and its own entrance.
Building class: Classification of buildings by use and size.
Building component (Bauteil): Single construction element such as walls, windows or roofs.
Building envelope (Gebäudehülle): All external elements that enclose the building.
Building location: Address or geo-coordinates indicating the exact site of the building.
Building parts (Gebäudeteile): Split into residential and non-residential parts for mixed-use buildings – usually two certificates are required.
Building Renovation Passport (Digitales Gebäudelogbuch): Digital document foreseen in the EPBD bundling the EPC, renovation steps, maintenance and construction documents (not yet mandatory in Germany).
Building services (Anlagentechnik / Haustechnik): Technical systems supplying and controlling a building’s energy demand (heating, ventilation, AC, etc.).
Building standard: Requirements for the energy quality of a building.
Building type: Distinction by use, e.g. residential vs. non-residential.
Building useful area (AN): Reference area for energy indicators under the German Buildings Energy Act, also called energy reference area; measured in m².
Building volume (Ve): Heated volume enclosed by the building envelope, measured in m³.
Buildings Energy Act (Gebäudeenergiegesetz, GEG): German federal law setting the energy requirements for buildings (replaced the EnEV in 2020; to be replaced by the GModG).
Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG): Planned successor to the GEG (in force before 1 July 2026), replacing the flat 65 % renewable-energy rule with technology-open heating choice plus the Biotreppe, and transposing the new EU Buildings Directive (EPBD).
C
Calorific value (Heizwert): Measure of the usable energy content of a fuel.
Ceiling heating (Deckenheizung): Heating system installed in or on the ceiling.
Ceiling insulation (Deckendämmung): Thermal insulation on or above a building’s ceiling.
Central heating (Zentralheizung): Heating system that generates heat centrally and distributes it through pipework.
Certificate / Ausweis: Short form for the energy performance certificate (Energieausweis), including the demand-based and consumption-based variants.
Certificate creation: Process of issuing an Energieausweis documenting the building’s energy performance.
Certificate type (Art des Energieausweises): Differentiates the Bedarfsausweis, Verbrauchsausweis and Energyausweis Smart™ (a combination of both).
Checklist: Overview to verify all data needed for an EPC.
Chimney (Schornstein): Component for discharging flue gases from heating systems.
Chimney damage (Versottung): Deterioration of a chimney caused by flue-gas condensation.
Circulation pipe (Zirkulationsleitung): Pipe that keeps hot water circulating in the system to avoid waiting times at taps.
Circulation pump (Zirkulationspumpe): Heating pump that continuously supplies hot water.
Cladding shell (Vorsatzschale): Extra insulation layer in front of a wall, e.g. timber or plasterboard.
Climate zone: Region with comparable climatic conditions affecting energy demand.
CO₂ emissions: Amount of carbon dioxide caused by a building’s energy use.
CO₂ price (nEHS): Surcharge on fossil fuels (oil, gas, LPG) under Germany’s national emissions trading scheme, transitioning into EU-ETS 2 from 2027 – does not apply to the bio-share of the Biotreppe.
Coefficient of performance (COP): Efficiency ratio for heat pumps comparing useful heat output to electrical input.
Collector (Kollektor): Component capturing and converting solar energy, e.g. in solar thermal systems.
Combined heat and power (KWK): Simultaneous generation of electricity and heat using a single generator.
Computer simulation: Calculation method for the energy demand of a building, considering multiple influencing factors.
Condensation point: Temperature at which water vapour condenses on building components.
Condensation water: Water formed when humid air cools at cold surfaces.
Condensing boiler (Brennwertkessel): Heating system that achieves high efficiency by recovering flue-gas waste heat.
Construction year (Baujahr): Year a building, part of a building or component was erected.
Consumption certificate (Verbrauchsausweis): EPC based on metered consumption from the last three years (short for Energieverbrauchsausweis).
Consumption indicator (Verbrauchskennwert): Metric expressing actual energy consumption per square metre.
Cooling demand: Energy needed to cool a building.
Cost-benefit analysis: Evaluation of the economic viability of energy measures.
CPC vacuum-tube collector: Solar collector for hot water built from evacuated double tubes.
Cross-section calculation: Dimensioning of pipes or ducts in heating and ventilation systems.
Cross ventilation: Natural ventilation through opposite windows or openings.
Cross-ventilation capacity: A building’s ability to exchange air efficiently via cross ventilation.
D
Date of issue (Ausstellungsdatum): Day on which the EPC was officially issued and signed.
Decentralised ventilation: Ventilation system serving individual rooms independently.
Demand certificate (Bedarfsausweis): EPC based on the calculated energy demand (short for Energiebedarfsausweis).
DIN V 18599: Standard prescribed by the GEG since 2024 for calculating a building’s energy performance.
Direct electric heating (Stromdirektheizung): Electrical generation of room heat, often combined with solid-state heat storage.
Direct heating: Heating system that warms rooms directly, e.g. electric heater.
Displacement ventilation (Quellüftung): Ventilation introducing fresh air at floor level and exhausting stale air near the ceiling.
Distribution network: Pipework or ducts for heating, water or ventilation.
District heating (Fernwärme): Supply of heat via a central network, typically operated by municipal utilities.
Domestic hot water preparation: Generation of warm tap water for households.
Domestic hot water heating (Trinkwassererwärmung): Heating of drinking water for household use.
Double glazing: Window with two panes for improved thermal insulation.
Drinking water installation (Trinkwasserinstallation): Pipework and fittings supplying drinking water.
Dwellings / Apartments: Number of separate housing units in the building, listed on the EPC.
E
Efficiency class: Classification of a building’s energy performance from A+ to H.
Electricity consumption: Metered electrical energy used by the building.
Emissions: Pollutants released by a building’s energy use, in particular CO₂.
Final energy demand (Endenergiebedarf): Energy needed for heating, hot water and ventilation at the building’s system boundary.
Energy consumption: Climate-corrected energy used in the building over three consumption years.
Energy consumption certificate (Energieverbrauchsausweis): EPC based on metered consumption of the last three years.
Energy demand: Calculated energy a building needs for heating, hot water and ventilation.
Energy demand certificate (Energiebedarfsausweis): EPC based on the calculated energy demand.
Energy efficiency: Ratio of energy input to benefit in a building.
Energy efficiency class: Classification of the building’s energy efficiency on the A+ to H scale.
Energy indicator (Energiekennwert): Metric expressing energy consumption or demand per square metre.
Energy Performance Certificate (Energieausweis): Official document rating a building’s energy quality.
Energy reference area (Energetische Nutzfläche): Sum of all heated areas (residential plus utility areas) used for energy calculations.
Energy Saving Ordinance (EnEV): Former German regulation on energy use in buildings, now replaced by the GEG.
Envelope surface (Hüllfläche): Total area of heat-transmitting components of a building.
Environmental compatibility: Assessment of a building’s ecological impact.
Environmental energy (Umweltenergie): Energy from natural sources like sun, air or ground.
EPBD (Energy Performance of Buildings Directive): EU Buildings Directive 2024/1275 to be transposed into national law by 29 May 2026 – implemented in Germany via the GModG; key topics are the A–G scale, Zero-Emission Buildings, MEPS for non-residential buildings, renovation duties for the worst-performing buildings and the Smart Readiness Indicator.
Energyausweis Smart™: Hybrid EPC by energyausweis.de combining the benefits of demand- and consumption-based certificates.
Existing building (Bestandsgebäude): Building that is no longer considered new (after roughly three years).
External thermal insulation composite system (ETICS, WDVS): Layered system of insulation plus rendered finish on exterior walls.
F
Façade insulation (Fassadendämmung): Thermal insulation of a building’s outer walls.
Fan / Ventilator: Device for moving air in ventilation systems.
Federal funding (Bundesförderung): State subsidies for energy refurbishments or new builds, including the BEG framework.
Final energy demand (Endenergiebedarf): Energy required at the building boundary for heating, hot water and ventilation.
Flat roof: Roof with very low pitch.
Floor plan (Grundriss): Drawing showing the room layout of a building.
Flow temperature (Vorlauftemperatur): Temperature of heating water leaving the boiler towards the radiators.
Flush-mounted installation: Heating or electrical lines installed beneath plaster.
Fossil fuels: Energy carriers from organic origin such as oil, gas or coal.
Full thermal protection (Vollwärmeschutz): Comprehensive insulation of the exterior walls.
Funding programmes (Fördermittel): Financial support schemes for energy measures.
G
Gas heating: Heating system fuelled by natural gas.
Geothermal energy (Geothermie): Heat extracted from the ground.
GEG: Abbreviation for the Gebäudeenergiegesetz (Buildings Energy Act).
Glazing (Verglasung): Type and quality of window panes, affecting heat transmission.
GModG: Abbreviation for the Gebäudemodernisierungsgesetz, the planned successor of the GEG from 2026.
Green electricity (Ökostrom): Electricity from renewable sources used in the building.
Green gas quota (Grüngasquote): Mandatory quota foreseen in the GModG draft, obliging gas suppliers to feed in a rising share of climate-friendly gases (biomethane, hydrogen) from 2028 (starting at ~1 %).
Gross volume (Bruttorauminhalt): Volume of a building including all enclosed spaces.
H
Heat demand (Wärmebedarf): Energy required to heat a building.
Heat generator (Wärmeerzeuger): Device or system that produces heat, e.g. a boiler.
Heat load (Heizlast): Maximum amount of heat required to heat a building.
Heat loss (Wärmeverlust): Energy unintentionally lost from a building.
Heat pump (Wärmepumpe): Heating system that uses ambient heat together with electrical energy.
Heat recovery: Recovery of heat from exhaust air or waste water to save energy.
Heat transfer station: Equipment that hands over heat from district heating to the building.
Heated area (Beheizte Fläche): Area inside the building heated directly or indirectly for residential use.
Heating costs: Costs incurred for heating and hot-water energy.
Heating energy demand (Heizenergiebedarf): Energy needed for space heating.
Heating period (Heizperiode): Part of the year when heating is required.
Heating system (Heizungsanlage): System for producing and distributing heat in the building.
Heating systems: General category covering heat pumps, solar thermal and similar systems.
Heritage protection (Denkmalschutz): Legal protection of historic buildings, often providing exemptions from GEG obligations.
Hybrid heating (Hybridheizung): Heating system combining multiple energy sources (e.g. heat pump with gas peak-load boiler), explicitly allowed in the technology-open catalogue of the GModG.
Hydraulic balancing (Hydraulischer Abgleich): Optimisation of heat distribution within a heating system.
I
Implementation control: Verification of correct execution of energy renovation works.
Indirectly heated rooms: Rooms thermally connected to other heated spaces by air exchange.
Indoor temperature: Average set-point temperature inside the heated volume; under DIN V 18599 fixed at 20 °C mean zone temperature.
Indoor air temperature: Temperature maintained inside the building.
Individual renovation roadmap (iSFP): Standardised consulting report for the step-by-step energy renovation of a property.
Infiltration: Uncontrolled air exchange through leaks in the building envelope.
Infrared heating: Heating system that emits warmth via infrared radiation.
Inspection opening: Access for maintenance and inspection of technical installations.
Inspection report: Documentation of analyses on a building’s energy quality.
Installation room: Area for technical installations and pipework.
Instantaneous water heater (Durchlauferhitzer): Device that heats water as it flows through.
Insulated glazing: Multi-pane glazing for improved thermal insulation.
Insulation (Dämmung): Thermal isolation of the building envelope including walls, roof and floor.
Insulation materials (Dämmstoffe): Materials reducing heat losses (e.g. mineral wool, ETICS).
Integral planning: Holistic planning considering all energy-related aspects.
Interior insulation: Insulation applied to the inside of exterior walls.
Invoice (Rechnung): Billing for issuing the EPC, sent after the original certificate.
Invoice payment (Rechnungskauf): Pay after receipt – up to 7 days payment grace when ordering via energyausweis.de.
Issuer (Aussteller): Companies or experts authorised under the GEG to issue EPCs; see online providers comparison.
J
JAZ – Annual coefficient of performance: See Annual COP.
K
KfW: German federal development bank (Kreditanstalt für Wiederaufbau) providing funding for energy-efficient construction and renovation.
KfW Efficiency House (KfW-Effizienzhaus): Building standard with defined energy requirements; the KfW Efficiency House 55 needs only 55 % of a reference building’s energy and has been mandatory for new builds since 2024.
KfW funding: KfW programmes supporting energy-efficient new builds or renovations.
Kilowatt-hour (kWh): Unit of energy or heat.
L
Life cycle assessment (Ökobilanz): Evaluation of a building’s environmental impact across its life cycle.
Light transmittance: Share of incoming light that passes through a window.
Living area (Wohnfläche): Floor area used for living purposes; for EPCs determined according to the Wohnflächenverordnung.
Local heating: Decentralised heat generation for single rooms or areas.
Long-life insulation: Insulation materials with particularly long service life and stability.
Low-energy building (Niedrigenergiegebäude): Building standard with very low energy demand – mandatory under EU Directive 2010/31/EU for all new builds since 2021.
Low-temperature heating (Niedertemperaturheizung): Heating system operating with low flow temperatures.
M
Maintenance (Instandhaltung): Measures to preserve the building fabric and services.
Masonry (Mauerwerk): Construction of stones or concrete relevant for insulation strategy.
Material parameter: Specific property of building materials such as thermal conductivity.
Maximum allowed U-value: Highest permitted U-value for components under statutory requirements.
Measurement devices: Instruments for recording energy consumption or demand.
MEPS (Minimum Energy Performance Standards): Mandatory minimum energy standards for non-residential buildings under the EPBD, limiting primary energy demand to 3.5× the reference building from 2030 and 2.95× from 2033.
Micro-CHP: Small combined heat-and-power unit producing electricity and heat simultaneously.
Minimum air exchange: Required air exchange rate to safeguard indoor air quality.
Minimum thermal protection (Mindestwärmeschutz): Statutory minimum requirements for thermal insulation of components.
Mixed heating (Mischheizung): Combination of several heating systems in one building.
Mixed-use building (Mischgebäude): Building combining residential and commercial use.
Modernisation: Energy renovation aimed at improving the building’s energy efficiency.
Modernisation recommendations: Suggestions inside the EPC to improve the building’s energy efficiency.
Moisture protection (Feuchteschutz): Measures protecting the building from moisture damage.
Monthly balance: Comparison of energy generation and consumption over a month.
N
Net floor area: Total floor area excluding walls and non-usable spaces.
New build (Neubau): Building completed no more than three years ago.
Night setback (Nachtabsenkung): Automatic reduction of heating temperature at night.
Night-storage heating (Nachtstromheizung): Heating that uses off-peak electricity to charge thermal storage.
O
Oil heating (Ölheizung): Heating system running on heating oil.
Old building (Altbau): Building constructed before November 1978.
Online Energy Certificate: EPC issued digitally and efficiently via energyausweis.de.
P
Passive house (Passivhaus): Building standard with extremely low energy demand thanks to optimised insulation and ventilation.
Pellet heating (Pelletheizung): Heating system running on pressed wood pellets.
Perimeter insulation: Insulation of below-ground building parts such as basement walls.
Photovoltaics (PV): Technology generating electricity from solar energy.
Pipe insulation: Insulation of heating or hot-water pipes.
Plinth insulation (Sockeldämmung): Insulation of the lower exterior wall area to avoid thermal bridging.
Primary energy demand: Total energy required including the energy conversion chain – stated in the EPC to document sustainability.
Primary energy factor: Energy expenditure of the upstream process chain of a given energy carrier.
Project planning (Projektierung): Planning and calculation of energy measures for a building.
Property data (Objektdaten): Information about the building documented in the EPC.
Property valuation: Determination of a property’s market value, where the EPC can play a role.
Public building: Building accessible to the public with special EPC requirements.
Pump power: Energy consumption of the heating circulation pump.
Q
Qualified energy consulting: Expert advice on optimising a building’s energy performance.
Quality assurance: Measures ensuring the proper preparation of the EPC.
Quality control: Verification of compliance with energy standards during construction or renovation.
Quartz heating: Heating emitting infrared radiation from quartz elements.
R
Radiant heating: Heating that emits warmth via infrared radiation.
Radiator (Heizkörper): Component releasing heat to the room.
Rainwater: Precipitation water that can be used for irrigation or technical purposes.
Rated output (Nennleistung): Maximum output of a heating system under defined conditions.
Reason for issuance (Anlass der Ausstellung): Why the EPC is created (sale, letting, renovation, etc.).
Recirculating air heating (Umluftheizung): Heating system circulating and warming room air.
Reference building (Referenzgebäude): Fictional building defined by the GEG with identical geometry, useful area, orientation and use as the real building.
Reference value (Richtwert): Orientation figure for energy parameters in building assessment.
Renewable energy (Erneuerbare Energien): Energy sources such as sun, wind or biomass usable in buildings.
Renovation (Sanierung): Comprehensive construction measures to improve a building’s energy efficiency.
Renovation roadmap (Sanierungsfahrplan): Step-by-step plan for energy modernisation works.
Rental contract: Contract in which the EPC must be presented when letting the property.
Residential building (Wohngebäude): Building used for living purposes; EPCs are issued either for residential or non-residential buildings.
Residual energy demand: Remaining energy demand after renovation measures.
Return flow temperature (Rücklauftemperatur): Temperature of the heating water returning to the boiler.
Room air conditioning (Raumlufttechnik): Technical systems controlling indoor temperature and air quality.
Room heating: Heating system that warms single rooms or zones individually.
Roof area: Total area of a building’s roof.
S
Service life (Nutzungsdauer): Assumed useful life of a building or component – relevant for tax purposes.
Shading (Verschattung): Shadowing of windows or collectors that increases energy demand.
Shell construction (Rohbau): Building structure before insulation and services are installed.
Shutter box (Rollladenkasten): Insulation of the housing for roller shutters to reduce heat losses.
Skylight (Oberlicht): Window in a ceiling or roof for natural daylighting.
Small buildings: Buildings with less than 50 m² of usable area do not require an EPC under the GEG.
Smart Readiness Indicator (SRI): EU indicator from the EPBD rating how well a building adapts to occupants and the electricity grid and optimises its energy use (voluntary in Germany for now).
Solar obligation / Solarpflicht: Alternative to the Biotreppe foreseen in the GModG draft (2029–2034) with minimum aperture areas of 0.04 m² per m² useful area for single/two-family homes and 0.03 m² for multi-family homes; several federal states already require PV on new builds and roof renovations.
Solar thermal (Solarthermie): Use of solar energy for hot water or space heating support.
Solar thermal system: System using solar heat for heating or hot water.
Spring-water heating (Quellwasserheizung): Heating that extracts heat from natural water sources, e.g. groundwater.
Square metre: Unit for measuring area.
Stairwell (Treppenhaus): Not part of the living area but may count as energy reference area.
Standard house (Typenhaus): Standardised building with predefined floor plan and construction.
Standard heating load: Standardised calculation of the heat demand of a building.
Storage heating (Speicherheizung): Heating that buffers heat in dedicated materials.
Subsidy (Zuschuss): Financial support for energy renovation measures.
Summer thermal protection (Sommerlicher Wärmeschutz): Measures to prevent overheating during warm months.
Supply air (Zuluft): Fresh air introduced into a room or building.
Surface heating (Flächenheizung): Heating system distributing heat over large surfaces (e.g. underfloor heating).
Surface temperature: Temperature of wall, ceiling or floor surfaces.
Sustainability: Consideration of ecological and economic aspects in energy measures.
System boundary (Systemgrenze): Outer surface of the heated zone separating it from the surroundings.
T
Technical building equipment: All technical installations in a building, e.g. heating, ventilation, sanitary.
Temperature: Measure of warmth of a room or component.
Temperature setback: Reduction of room temperature, e.g. at night, to save energy.
Temperature zone: Relevant for non-residential buildings split into zones; a deviation of more than 4 °C from neighbouring rooms justifies a zone boundary.
Thermal bridge (Wärmebrücke): Spot in the envelope with increased heat loss.
Thermal insulation (Wärmedämmung): Measures to reduce heat losses through the building envelope.
Thermal Insulation Ordinance (Wärmeschutzverordnung): Historical regulation on thermal protection, now integrated into the GEG.
Thermography: Imaging method showing temperature distribution on buildings.
Thermostatic valve (Thermostatventil): Valve regulating the temperature of a radiator.
Top-floor ceiling (Oberste Geschossdecke): Accessible ceiling between heated rooms and unheated attic space.
Total energy demand: Sum of all energy required by a building.
Transmission heat loss: Heat losses through the building envelope.
Two-side attached residential building: Building whose vertical surfaces are attached to at least 80 % to another residential or non-residential building on two different cardinal directions.
U
U-value: Heat transfer coefficient of a building component indicating heat loss, in W/(m²·K).
Underfloor heating (Fußbodenheizung): Heating distributing warmth via the floor.
Upper floor (Obergeschoss): Storey above the ground floor.
Useful area (Nutzfläche): Area definition per DIN 277 including ancillary use (WCs, balconies) and main use (living, office, storage).
V
Validity period (Gültigkeitsdauer): An EPC is valid for 10 years.
Ventilation (Lüftung): Air exchange via windows, technical systems or infiltration.
Ventilation heat loss: Heat losses caused by air exchange between inside and outside.
Ventilation system (Lüftungsanlage): System for controlled supply and exhaust air.
W
Wet insulation (Nassdämmung): Insulation method processed in a moist state.
Window area: Total area of all windows in a building.
Window replacement (Fenstertausch): Replacement of old windows to improve energy efficiency.
Window ventilation: Ventilation by manually opening windows or doors.
Wood pellets: Pressed wood residues used as fuel for pellet heaters.
Worst-performing buildings (WPB): Term from the EPBD for the energetically poorest buildings (16 % of non-residential and 26 % of residential buildings) facing priority renovation duties or MEPS; in Germany implemented via the GModG and the national building renovation plan.
X
XPS insulation: Extruded polystyrene, an insulation material with high compressive strength.
Xylene (Xylol): Solvent used in paints and adhesives (indirectly relevant for indoor air quality).
Xylolite: Historic building material made of wood meal and binder, occasionally found in old buildings.
Y
Year of construction: See Construction year.
Ytong: Brand name for aerated concrete blocks offering good thermal insulation.
Z
Zero-Emission Building (ZEB, Nullemissionsgebäude): New-build standard from the EPBD with no on-site fossil CO₂ emissions – mandatory in the GModG for public non-residential new builds from 2028 and all new builds from 2030.
Zone heating: Heating system warming individual areas or zones separately.
Zones: Rooms that differ substantially in use, technical equipment, internal loads or supply.