lämmitystarve

Lämmitystarve is a Finnish term that describes the heating demand or heating requirement of a building or space. It represents the amount of energy needed to keep indoor temperatures at a defined comfort level under given outdoor temperatures and occupancy patterns. The concept is central to building physics and energy planning, linking weather conditions, building envelope properties, ventilation, and internal heat gains to the required heating energy.

Calculation of lämmitystarve can be expressed in several ways. A common approach is heating degree-days (HDD), which summarises how much outdoor temperature falls below a base temperature needed for comfort, with higher HDD indicating greater heating demand. In more detailed analyses, hourly simulations accumulate the difference between the target indoor temperature and the actual indoor temperature, accounting for heat losses through walls, windows, and ventilation as well as gains from equipment and occupancy. Results are often presented in energy units per area, such as kilowatt-hours per square meter (kWh/m²) over a specified period.

Applications of lämmitystarve include informing energy performance assessments, designing new buildings, planning retrofits, and forecasting loads for district heating systems. It serves as a link between climate, construction quality, and energy consumption, aiding decisions on insulation, airtightness, heating systems, and control strategies.

Limitations include dependence on assumed indoor temperatures, occupancy, and user behavior, making lämmitystarve a modelled demand rather than a direct measurement of actual energy use. It is distinct from social concepts like energy affordability or energy poverty, though related discussions may intersect in policy contexts. See also heating degree days, energy efficiency, building envelope, district heating, and energy poverty.