Energy Modeling: A building as a system

A building functions as a system, each component contributes/affects the whole which only an Energy Model simulation can quantify their effect on energy consumption and indoor comfort. With each of the Energy Model inputs the designer will get instant feedback of the predicted effects on energy consumption and comfort which the designer will iterate until the desired performance targets are reached. 

Three Performance Targets

Thermal Energy Demand

Passive House certification requires buildings to use very little energy for heating or cooling while meeting specific Thermal Comfort criteria. A lower Heating/Cooling energy consumption and peak load allow for smaller equipment which in turn reduces operational carbon emissions.

Total Energy Demand

Passive House certification requires buildings to use very little total energy for an overall building; heating, cooling, plug loads, lighting, appliances, domestic hot water, etc. Again, Lower energy consumption and peak load of the overall reduce operational carbon emissions.


To ensure building durability, verify construction quality, and boost energy performance, Passive House buildings must have high levels of airtightness, as measured by blower door testing (≤ 0.6 Air changes per hour @ 50 Pascals pressure). This airtightness, combined with high-quality HRV/ERV ventilation, delivers superior indoor air quality and energy efficiency.

Passive House Energy Modeling tool: PHPP

The principal energy modeling tool for Passive House is the Passive House Planning Package (PHPP) and is one of the most powerful design tools for designing low energy buildings. The PHPP forms the basis for quality assurance and certification of a building as a Passive House or an EnerPHit retrofit. Like Building Science, all calculations in the PHPP are based strictly on the laws of physics. But a degree in physics is not necessary to harness the power of Passive House design. Instead, digital tools do the heavy lifting on physics calculations and energy modeling, empowering designers to optimize for performance and cost.

The Passive House Planning Package (PHPP) is a design tool which enables architects and designers to professionally plan and optimise their Passive House design. The PHPP contains dimensioning tools for windows (with regard to optimal thermal comfort), home ventilation (with regard to optimal air quality with adequate air humidity) and building technology. The PHPP treats the entire building as one unit including the ventilation system and other mechanical systems.

The Passive House Planning Package (PHPP) contains everything necessary for designing a properly functioning Passive House or any Low Energy Building. The PHPP prepares an energy balance and calculates the annual energy demand of the building based on the user input relating to the building’s characteristics.
The main results provided by this software programme include:

  • The annual heating demand [kWh/(m²a)] and maximum heating load [W/m²].
  • Summer thermal comfort with active cooling: cooling demand [kWh/(m²a)] and maximum cooling load [W/m²]
  • Summer thermal comfort with passive cooling: frequency of overheating events [%] (see passive cooling tool )
  • Annual primary energy demand for the whole building [kWh/(m²a)]

More info:  PHPP – Passive House Planning Package

Energy modeling as an Economics tool

The Energy model simulation is also a tool that guide’s the design process by supplying data to aid in justifying the cost of components and assembly types. The cost of the energy efficiency measures can be evaluated while considering interest rates, amortization periods, inflation, residual value and maintenance.

In addition, it can be used to quantify the rate of diminishing returns per component, some examples are:

  • How much each extra inch of insulation contributes to lowering energy demand.
  • Justify the added cost of a higher quality component vs another by energy saving comparison.

But some parameters can hardly be assessed financially:

  • Aesthetic aspects
  • Better living comfort; Thermal & Acoustic
  • Better indoor air quality
  • Aspects of safety
  • Environmental Responsibility
  • Social effects

More info: Economic feasibility of Passive House design