Passive House PHPP Energy Balance Calculator

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Overview

The Passive House PHPP Energy Balance Calculator estimates the net annual energy balance of a building using a simplified PHPP-style loss-versus-gain framework. The final result is shown in kWh/m²·yr in Metric mode and kBtu/ft²·yr in Imperial mode.

The calculator uses a fixed annual balance model with four inputs: annual transmission heat losses, annual ventilation heat losses, annual useful solar gains, and annual internal gains. The result is a net annual energy balance value.

A more positive balance means gains are offsetting losses more effectively. A more negative result indicates a larger annual heating-energy deficit — useful for identifying buildings that need envelope or ventilation improvements.

This is a simplified screening tool inspired by PHPP methodology, not a full PHPP replacement. Results align with four performance bands: FAVORABLE, BALANCED, DEFICIT, and SEVERE DEFICIT.

How to Use This Calculator

  1. Select Imperial or Metric units — Imperial uses kBtu/ft²·yr; Metric uses kWh/m²·yr.

  2. Enter the annual transmission heat losses — from the building envelope in the selected unit.

  3. Enter the annual ventilation heat losses — from ventilation in the selected unit.

  4. Enter the annual useful solar gains — in the selected unit.

  5. Enter the annual internal gains — in the selected unit.

  6. Click “Calculate” — review the net annual energy balance and compare it against Passive House style performance expectations.

A more positive balance indicates gains are effectively offsetting losses. A more negative result indicates a larger annual heating-energy deficit.

Inputs & Outputs

Inputs

  • •Annual Transmission Losses (kWh/m²·yr / kBtu/ft²·yr)
  • •Annual Ventilation Losses (kWh/m²·yr / kBtu/ft²·yr)
  • •Annual Useful Solar Gains (kWh/m²·yr / kBtu/ft²·yr)
  • •Annual Internal Gains (kWh/m²·yr / kBtu/ft²·yr)

Outputs

  • •Total Annual Losses (kWh/m²·yr / kBtu/ft²·yr)
  • •Total Annual Gains (kWh/m²·yr / kBtu/ft²·yr)
  • •Net Annual Energy Balance (kWh/m²·yr / kBtu/ft²·yr)

Formula

Calculator Formula

This calculator uses the following fixed annual energy balance logic:

lossesTotal = transmissionLosses + ventilationLosses
gainsTotal = solarGains + internalGains
netBalance = gainsTotal − lossesTotal

The same formula applies in both Metric (kWh/m²·yr) and Imperial (kBtu/ft²·yr) modes. Enter all values in the unit system you have selected.

Variable Reference

Variable Meaning Units
transmissionLosses Annual envelope transmission losses kWh/m²·yr or kBtu/ft²·yr
ventilationLosses Annual ventilation heat losses kWh/m²·yr or kBtu/ft²·yr
solarGains Annual useful solar gains kWh/m²·yr or kBtu/ft²·yr
internalGains Annual internal gains kWh/m²·yr or kBtu/ft²·yr
lossesTotal Total annual heat losses kWh/m²·yr or kBtu/ft²·yr
gainsTotal Total annual useful gains kWh/m²·yr or kBtu/ft²·yr
netBalance Net annual energy balance kWh/m²·yr or kBtu/ft²·yr

Formula Meaning

A more positive netBalance means gains are offsetting losses more effectively. A more negative netBalance means the building has a larger annual heating-energy deficit.

  • FAVORABLE: annual gains exceed losses
  • BALANCED: annual balance is close to neutral with only a small deficit
  • DEFICIT: losses exceed gains by a noticeable margin
  • SEVERE DEFICIT: losses substantially exceed useful gains

What is Passive House PHPP Energy Balance

A Passive House PHPP-style energy balance is an annual comparison between heat losses from the building envelope and ventilation, and useful gains from solar input and internal sources. The goal is to understand whether the building is approaching a well-balanced low-energy condition or whether annual losses still dominate.

In PHPP-based design, this balance is shaped by insulation quality and thermal bridge control, airtightness, ventilation heat recovery performance, glazing specification and solar access, internal gains from occupancy and equipment, and climate conditions at the project location.

The net annual energy balance is not the same as peak heating load or annual heating demand in the certification sense. It shows, in a single number, whether the modeled losses and gains are working together favorably or whether a meaningful deficit remains.

Key Factors in the Annual Balance

The annual energy balance is sensitive to several key parameters. Transmission losses are driven by envelope U-values, surface areas, and thermal bridges at junctions. Improving insulation thickness, minimizing thermal bridges, and using high-performance windows reduces this component directly.

Ventilation losses depend on the ventilation rate and the heat recovery efficiency of the MVHR (mechanical ventilation with heat recovery) unit. A well-designed MVHR system can recover 80–90% of heat from outgoing exhaust air, significantly reducing the ventilation loss contribution to the annual balance.

Useful solar gains are captured through south-facing glazing and depend on window SHGC, glazing area, shading strategy, and local solar irradiation. Oversizing south glazing without controlling summer shading can create overheating risk. Internal gains from occupants, lighting, and appliances also offset annual losses; in tightly insulated buildings they represent a larger fraction of the heat balance than in conventional construction.

Classification System

This calculator uses a four-level classification for the net annual energy balance result. A FAVORABLE result means annual gains exceed losses and the balance is positive — strong overall performance under the selected assumptions. A BALANCED result means the annual balance is close to neutral with only a modest deficit, typical for a well-designed Passive House in a moderate climate. A DEFICIT result means losses exceed gains by a noticeable margin; the envelope, ventilation recovery, or gain assumptions should be reviewed. A SEVERE DEFICIT result means losses substantially exceed gains; the full PHPP-style input set should be rechecked and major loss-reduction measures prioritized before relying on mechanical heating compensation.

Passive House Design Context

Passive House design targets annual heating demand of 15 kWh/m²·yr or less through very high envelope insulation, airtightness (typically ≤ 0.6 ACH50), highly efficient MVHR, and an optimized solar gain strategy. This calculator is a simplified screening tool for understanding annual balance drivers early in the design process. It does not produce a certification-ready PHPP analysis. Final results should always be verified with a full project PHPP calculation using project-specific climate data, geometry, shading, and detailed input parameters.

Key Facts

  • Annual energy balance depends on both loss reduction and useful gain capture.
  • Lower transmission losses improve the energy balance directly.
  • Lower ventilation losses improve the energy balance directly.
  • Useful solar gains can materially improve the annual balance.
  • Internal gains also contribute to offsetting annual losses.
  • A near-neutral balance is stronger than a deeply negative one in this screening model.

Applications

  • Early Passive House design screening.
  • PHPP-style annual balance checks.
  • Comparing envelope improvement options.
  • Comparing ventilation loss scenarios.
  • Evaluating the effect of useful solar gains.
  • Reviewing whether the annual energy balance is favorable, balanced, or deficit-driven.

Example Calculation

Metric Example

Given:

  • Transmission losses = 24.0 kWh/m²·yr
  • Ventilation losses = 10.0 kWh/m²·yr
  • Solar gains = 18.0 kWh/m²·yr
  • Internal gains = 8.0 kWh/m²·yr

Step 1: Total losses

Losses_total = 24.0 + 10.0 = 34.0 kWh/m²·yr

Step 2: Total gains

Gains_total = 18.0 + 8.0 = 26.0 kWh/m²·yr

Step 3: Net annual energy balance

Net Balance = 26.0 − 34.0 = −8.0 kWh/m²·yr

Result: −8.0 kWh/m²·yr — BALANCED

This falls in the BALANCED range (between −10.0 and 0.0 kWh/m²·yr). It indicates a near-neutral annual balance with only a modest heating-energy deficit.

Imperial Example

Given:

  • Transmission losses = 7.5 kBtu/ft²·yr
  • Ventilation losses = 3.0 kBtu/ft²·yr
  • Solar gains = 5.0 kBtu/ft²·yr
  • Internal gains = 1.8 kBtu/ft²·yr

Step 1: Total losses

Losses_total = 7.5 + 3.0 = 10.5 kBtu/ft²·yr

Step 2: Total gains

Gains_total = 5.0 + 1.8 = 6.8 kBtu/ft²·yr

Step 3: Net annual energy balance

Net Balance = 6.8 − 10.5 = −3.7 kBtu/ft²·yr

Result: −3.7 kBtu/ft²·yr — DEFICIT

This falls in the DEFICIT range (below −3.2 but above −9.5 kBtu/ft²·yr). It indicates a noticeable annual deficit and suggests that losses still exceed useful gains by a meaningful margin.

Standards & References

  • PHPP (Passive House Planning Package) — annual loss-versus-gain framework for Passive House design
  • Passive House Institute (PHI) — performance standards including 15 kWh/m²·yr annual heating demand target
  • ISO 52016-1 — energy performance of buildings: energy needs for heating and cooling
  • ASHRAE 90.1 — building envelope energy performance requirements

Limitations

  • This is a preliminary PHPP-style annual balance calculator, not a full PHPP implementation.
  • It uses a fixed calculator-specific balance model and does not calculate: monthly balance effects, dynamic thermal storage effects, peak load, overheating risk, thermal bridge breakdown, shading geometry, occupancy schedules, or detailed ventilation heat-recovery modeling.
  • It does not account for monthly seasonal variation, summer overheating behavior, or thermal inertia and heat-storage effects.
  • It does not replace full Passive House modeling, certification workflows, or project-specific energy simulation.
  • Actual project results depend strongly on climate, orientation, glazing, shading, airtightness, and detailed input quality.

Common Mistakes to Avoid

  • Treating annual energy balance as the same thing as peak heating load.
  • Ignoring ventilation losses while focusing only on transmission losses.
  • Overestimating useful solar gains.
  • Treating internal gains as guaranteed performance.
  • Using inconsistent annual units between losses and gains.
  • Assuming a slightly positive balance automatically proves certification readiness.
  • Ignoring shading and glazing strategy.
  • Treating this as a full PHPP replacement instead of a screening calculator.

Frequently Asked Questions

What does this calculator estimate?
It estimates the net annual energy balance by subtracting total annual losses (transmission plus ventilation) from total annual useful gains (solar plus internal). The result in kWh/m²·yr or kBtu/ft²·yr indicates whether the building has a favorable balance or a heating-energy deficit.
What does a positive result mean?
A positive result means annual useful gains exceed the modeled annual losses, producing a FAVORABLE balance in this screening model. This suggests that the building envelope, ventilation performance, and gain assumptions are working together effectively under the selected inputs.
What does a BALANCED result mean?
A BALANCED result means the annual balance is close to neutral and only slightly negative or exactly neutral. This usually indicates that envelope performance, ventilation heat recovery, and useful gains are working together reasonably well, with only a small net heating deficit.
What does a DEFICIT result mean?
A DEFICIT result means annual losses exceed useful gains by a noticeable amount, so the building still has a meaningful heating-energy shortfall. Envelope U-values, airtightness, ventilation heat recovery, window performance, or solar-gain assumptions should be reviewed.
What does a SEVERE DEFICIT result mean?
A SEVERE DEFICIT result means annual losses substantially exceed useful gains and the building is underperforming relative to a strong Passive House style balance. This is a warning sign that the full PHPP-style energy balance inputs should be rechecked and major loss-reduction measures prioritized.
Why do solar gains matter so much?
Useful solar gains can materially offset annual transmission and ventilation losses. In Passive House design, glazing strategy, orientation, shading, and window performance directly affect how much solar gain is captured as a useful contribution to the annual energy balance.
What annual value is commonly associated with Passive House certification?
A commonly referenced Passive House target is annual heating demand of 15 kWh/m²·yr or less, but that is not the same thing as this calculator's net annual energy balance. This calculator is a simplified screening tool that compares annual losses and useful gains, while certification relies on a full PHPP-based project assessment.
Does this replace PHPP?
No. This is a simplified annual screening calculator, not a full PHPP worksheet or certification tool. It is designed to give a transparent first-pass annual balance result that reflects the main PHPP-style drivers, but final design decisions require the full project PHPP analysis and project-specific climate data.

Frequently Used Together

Engineers often use these calculators in combination for complete project workflows:

Building Envelope Tightness

Blower Door Test Cfm50

Window U Value And Shgc Selector

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