Heat Loss Calculator

Interactive calculator for estimating heat loss of a family house and designing heat pump capacity per EN 12831.

Building Parameters

Heated floor area (m²)

Number of floors

Floor height (m)

External perimeter (m)

Location

Indoor design temperature (°C)

External Walls

Load-bearing wall material

Wall thickness (cm)

Wall insulation

Insulation thickness (cm)

Roof / Ceiling

Ceiling / roof structure

Structure thickness (cm)

Roof / ceiling insulation

Insulation thickness (cm)

Ground Floor

Floor structure

Structure thickness (cm)

Floor insulation

Insulation thickness (cm)

Windows by Orientation

Glazing type

Total window area: 16.0 m²

House orientation towards cardinal directions

Enter the window area in m² for each wall

Front wall

Back wall

Left wall

Right wall

Front wall faces: South (S)

Solid doors

Door type

Total area (m²)

Ventilation & Recovery

Air change rate (1/h)

Heat recovery (MVHR)

Domestic Hot Water (DHW)

Number of people

DHW temperature (°C)

DHW usage / person / day (l)

Heat Pump

SCOP (Heating)

COP (DHW)

Bivalent temperature (°C)

Total Building Heat Loss

Required power at design outdoor temperature to maintain the set indoor temperature.

Transmission heat loss

-- kW

Ventilation heat loss

-- kW

Annual Energy Balance

Heat demand (without gains)-- kWh

- Solar gains (deduction)--- kWh

- Internal gains (people & apps)--- kWh

Annual Heat Demand – DHW-- kWh

Total annual heat demand (supplied)-- kWh

Electricity – Heating-- kWh

Electricity – DHW-- kWh

Total Electricity Consumption-- kWh

Heating capacity (bivalent)-- kW

DHW heating capacity+ -- kW

Total recommended HP capacity-- kW

Heat transfer coefficient (HT)-- W/K

Specific space heating demand-- kWh/(m².a)

Building Geometry

Floor footprint: - m² External perimeter: - m External wall area: - m² Roof / ceiling area: - m² Floor area: - m² Heated volume: - m³

Geometry is automatically converted to external building dimensions (including wall thickness and insulation) as required by EN ISO 13789 for accurate calculations.

Detailed Heat Loss Breakdown

Construction Element	Area (m²)	R (m²·K/W)	U (W/m²·K)	Loss (W)	Share (%)
External Walls Load-bearing wall: R=- Wall insulation: R=-	-	-	-	-	-
Roof / Ceiling Ceiling structure: R=- Roof insulation: R=-	-	-	-	-	-
Ground Floor Floor structure: R=- Floor insulation: R=-	-	-	-	-	-
Windows	-	-	-	-	-
Solid doors	-	-	-	-	-
Thermal bridges (15%)	-	-	-	-	-
Ventilation	-	-	-	-	-
Total				-	100%

Heat Loss vs. Outside Temperature

This calculation is an approximate estimate. For an accurate heating system design, we recommend consulting a certified HVAC engineer.

Heat Loss Calculator