{"id":131002,"date":"2025-08-25T13:20:19","date_gmt":"2025-08-25T11:20:19","guid":{"rendered":"https:\/\/www.velasolaris.com\/?post_type=handbuch&p=131002"},"modified":"2025-10-02T14:03:28","modified_gmt":"2025-10-02T12:03:28","slug":"space-heating-demand","status":"publish","type":"handbuch","link":"https:\/\/www.velasolaris.com\/en\/handbuch\/polysun-designer\/energy-demand-circuit\/thermal-consumers\/building\/space-heating-demand\/","title":{"rendered":"Dynamic Model: Heating"},"content":{"rendered":"\n

Calculating Space Heating Demand for Optimal HVAC Design<\/h1>\n\n\n\n

The Dynamic Model is used to estimate the space heating or cooling demand of buildings, particularly when the actual heating demand of the building is unknown and must therefore be determined based on the building’s physical parameters. It accounts for all essential aspects of a building’s thermal behavior by incorporating both heat losses (e.g., through transmission, ventilation, and infiltration) and heat gains (e.g., from solar radiation, internal sources such as people, lighting, and equipment).<\/p>\n\n\n\n

The building icon represents either heated or cooled spaces (the living area to be heated, including the walls), unheated spaces (such as garages, basements, or technical rooms where the heating system can be installed), or both. The heated\/cooled spaces can be simulated using various building models. This allows for a more accurate approximation of the actual space heating demand. <\/p>\n\n\n\n

The Dynamic Model enables the definition of the building using adjustable standard dimensions and a wide selection of building types from a catalog (which in turn represent numerous international standard building types).<\/p>\n\n\n\n

\"Context<\/figure>\n\n\n\n

The building properties can be modified in the catalog. When doing so, ensure the U-value is adjusted accordingly. The U-value applies to the entire building, including doors and windows.<\/p>\n\n\n\n

Dynamic Model: Simplified Space Heating Demand Calculation<\/h2>\n\n\n\n

Integrated into the simulation algorithm of Polysun is a dynamic calculation of the building\u2019s thermal space heating demand, based on the heating\/cooling energy balance equation, presented here in a simplified form:<\/p>\n\n\n\n

\\(HG – HL = MCp \\cdot \\frac{\\Delta T}{\\Delta t}\\)<\/p>\n\n\n\n

\\(HG\\) = Heat gain [W]<\/p>\n\n\n\n

\\(HL\\) = Heat loss [W]<\/p>\n\n\n\n

\\(MCp\\) = Heat capacity [J\/K]<\/p>\n\n\n\n

\\(\\Delta T\\) = Temperature change per time step in the building [K]<\/p>\n\n\n\n

\\(\\Delta t\\) = Time step [s]<\/p>\n\n\n\n

This equation accounts for passive heat gains from the sun, body heat from occupants living in the building, air exchange rates, the type of lighting, and the presence of electrical appliances. The window-to-wall ratio (WWR) allows for consideration of the impact of the glazing type used. Depending on the windows selected, this is reflected in the SHGC value (Solar Heat Gain Coefficient).<\/p>\n\n\n\n

Dynamic Model: Primary and Secondary Parameters<\/h2>\n\n\n\n

The entered building parameters are divided into primary and secondary parameters:<\/p>\n\n\n\n

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Primary Parameters for Heating Load Calculation<\/h4>
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Geometry:<\/strong>\u00a0Building length (\\(l \\)), width (\\(w \\)), number of floors (\\(N_{f} \\)), and floor height (\\(H_{f} \\)) define the size and shape of the building.<\/p>\n

Orientation:<\/strong> The building orientation (\\(O \\)) relative to north influences the solar gains.<\/p>\n

Building Properties:<\/strong><\/p>\n