FAQ
These answers describe the current model and wizard scope. When an input or entitlement is not available in the current release, the answer says so directly.
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84 questions across 11 topics
Not in this release. You describe your house by hand, floor by floor: dimensions, construction year, glazing on each outside face, orientation and shading. The construction year gives starting U-values (how well each surface keeps heat in), and you can review and change them.
How building inputs workPlan upload is not available in this release. Enter floor geometry and envelope properties in the manual house description. A drawing may show dimensions or window locations, but it does not establish the insulation build-up or measured U-value of a wall.
Building input methodThe wizard does not read values from a certificate or from plans, so every number is one you entered or accepted. Check each floor dimension, orientation, glazing area, construction year and any U-value you replaced against your own documents. The result depends on the values that are saved, so an unchecked estimate should stay an estimate.
Review the inputsThis release does not build the envelope from a document. In manual entry, the construction year and house type give starting U-values and airtightness, which you can review and replace. Other fields use a default where one exists. The saved configuration shows the value that ran, and an empty field does not mean the physical effect is zero.
See the input workflowYes. Describe the proposed envelope and equipment as a scenario. For a renovation, save or reproduce the existing condition and compare it with the proposed condition using the same weather and comfort assumptions. The product does not automatically infer a before-state from a renovation plan.
Example comparison setupsThe production model groups similar spaces at floor level. A room with materially different conditions, such as an unheated garage or indoor pool hall, needs a separate modeled zone when the supported configuration provides one. Interior rooms and partitions within one zone are not individually resolved, so a floor-average temperature is not a room-by-room forecast.
Thermal model assumptionsThe wizard supports a synthesized typical weather year and a selected ERA5 historical year. The run uses the location and weather basis shown in its saved inputs and recap. ERA5 is reanalysis data, not a sensor installed at your house, and a typical year is not a forecast.
Weather and model methodChoose the typical-year option for a synthesized reference year or ERA5 for a historical weather year. Neither predicts next year's weather. A historical year preserves a particular sequence of conditions; a typical year represents an averaged reference profile. Compare the same basis across scenarios.
Weather basisWeather files use the location's standard-time offset; daylight saving is excluded from the simulation clock. Dynamic prices are aligned by month, day and hour to that weather clock. On 29 February, the model uses 28 February prices if the selected price year is not a leap year. The first local hour may use the nearest available price from the adjacent UTC date.
Tariff and timeline detailsEnergyPlus version 25.2.0 calculates the thermal behavior in steps of 15 minutes, four steps inside each hour. A house with a ground-source heat pump, or with a hot water cylinder heated by the heat pump or boiler, runs in steps of 5 minutes, twelve an hour. Everything we keep is hourly: the saved series, the CSV file and the energy management simulation, which works in whole hours. Results charts show hourly values or daily averages, depending on the range you select.
Energy units and resultsSome schedules are preset and some are yours. You choose the number of residents, one of three daily presence patterns, the yearly household electricity, and the day and night temperatures for heating and cooling. Hot water use follows the number of people. If you change nothing, the model assumes four residents on a typical weekday pattern, 4,500 kWh of household electricity a year (heating, cooling and hot water are counted separately), heating at 21 °C by day and 19 °C at night, and cooling at 24 °C. Holidays and absences are not modeled, and you cannot enter your own hourly profile. The saved run records the schedules it used, including the filled defaults.
Schedules and defaultsThe envelope uses absolute areas and thermal properties, with one U-value per element type across the house. Thermal bridges are not modeled as separate elements in the simulation. The sizing step adds an allowance for them when it works out each floor's design heat load. Internal partitions and furniture are not drawn: an aggregate internal mass represents their combined heat storage. Construction-year U-values are starting averages, not a survey of your actual wall build-up.
Envelope simplificationsGlazing area on each outside face, the house orientation and the glass specification set the solar gains. External blinds are the only shading, and a blind closes when the sun on its window is above 300 W/m² and the outdoor air is above 10 °C. Trees, neighboring buildings, overhangs and balconies do not shade the house. Window opening follows a fixed rule rather than your habits: a steady background flow of fresh air, plus extra airing on summer nights in a house with no cooling. The floor-level geometry does not place each window or predict local drafts.
Heating and cooling inputsCurrent results show the mean temperature and hourly temperature series for each modeled zone. They do not report an overheating-hours total. You can count hours above a threshold from the series, but state that threshold and do not treat a floor-level zone as a bedroom reading.
Summer comfort comparisonsThe wizard proposes a size from your house. It adds up the heat each storey loses on the design day (the very cold day heating is sized for), adds an allowance for hot water, and picks the smallest heat pump whose published capacity at the design outdoor temperature covers that load within 5 percent. The electric backup heater, 8 kW by default, carries any shortfall. Peak capacity and annual electricity use are different results: the first depends on the design day, the second sums operation over the whole weather year. A larger size uses little extra electricity with the manufacturers' declared data but starts its compressor more often; a smaller one leans on the backup heater. Treat the proposal as a starting point and confirm the final size with an installer.
Heating system comparisonsHeating performance comes from the published tables of one current, typical range of air-source and ground-source heat pumps. The model reads capacity and COP at the water temperature the loop actually delivers, between the published 35, 45, 55 and 65 °C columns. Cooling efficiency comes from one manufacturer datasheet at a single point, 35 °C outdoor air and 18 °C water. The other outdoor temperatures are estimates. A curve is therefore a representative profile for a type and size, not the measured performance of your unit at every temperature.
Heating and cooling optionsThe emitter sets the design supply temperature: 35 °C for underfloor heating, 50 °C for low-temperature radiators and 65 °C for high-temperature ones. On mild days the loops run cooler, following a heating curve, and the heat pump's published performance is read at the water temperature each hour needs, so cooler water means a better COP. The model sizes floors and radiators from the house's design heat load. It does not know the radiators you already have, so an installer still has to check those and the hydraulics.
Supported heating optionsYes for the backup heater: an electric element in the heating circuit, 8 kW by default, takes whatever load the heat pump cannot cover in each time step. Cycling has no efficiency loss in the model, because the manufacturers' product sheets for these units declare none (a degradation coefficient Cdh of 1). Standby is counted: 16 W per unit in every hour the unit does not run, from the same sheets. The model also estimates how often the compressor starts, from the water in the heating system and the control band, and saves it with each run without adding it to the energy. A separate defrost cycle is not modeled, because datasheet COPs at low outdoor temperatures normally include its effect. Real controllers add rules the model lacks, such as an outdoor temperature lock-out or a switch-on delay.
Heating optionsThe equipment model includes multi-zone heating and supported cooling combinations, but not every mix of emitter, zone and heat source is valid. A configuration must pass the product's equipment checks. The model does not establish that an installed heat pump can switch or balance the real zones as assumed.
Heating and coolingOnly the four-pipe heat pump recovers heat. While it cools the house, the heat it removes goes into the hot circuit, which also feeds the pool and preheats the hot water, instead of being rejected outdoors. A single reversible heat pump does not recover heat from cooling in the model. Recovered heat is not free: compressor, pump and fan electricity still count, and the results show it.
Pool and heat recoveryYes, with a simple rule. At every time step the model compares the floor surface temperature with the dew point of the room air plus a 1 K margin, and shuts the floor circuit off for that step if the surface would drop below it. The margin and the 18 °C chilled-water supply are fixed, not wizard settings. With air conditioning as a backup, the air conditioning takes the load meanwhile. With floor cooling alone, the room can rise above the cooling setpoint. Floor cooling needs underfloor heating, because it runs through the same floor circuit. None of this certifies condensation safety for an installed floor: real humidity sensors, controls and surfaces need checking on site.
Cooling model limitsLeakage and ventilation are separate effects. Airtightness starts from the construction year and you can replace it with a measured value. The leakage rate is constant, with no wind effect. A heat-recovery unit runs at a constant flow, recovers part of the exhaust heat and uses fan electricity, which is counted in the results. Its flow is sized from the house, and its recovery efficiency is a default. In summer the unit opens a bypass when the room is warm and the outdoor air is above 12 °C and cooler than the room, so cool night air comes in without passing the exchanger. The model does not certify indoor air quality or duct performance.
Ventilation assumptionsVery little, with the manufacturers' declared data. On a 2025 new build of 182 m² with underfloor heating, a 16 kW heat pump used about 70 kWh a year more than the 10 kW size the wizard proposed, about 18 EUR. What grows is the number of compressor starts, about 40 % more, because a bigger unit has a higher minimum output and switches on and off more on mild days. The water in the heating system matters too: radiators without a buffer tank hold less water than underfloor heating, so the same unit starts more often on them. Undersizing is what costs energy, since the backup heater covers the shortfall at a COP of 1.
Heating system comparisonsYou enter capacity in kWp and a panel tilt for each roof direction. For every hour the model takes the sunlight from the same weather file as the thermal simulation, works out how much lands on each tilted face, scales it to your capacity, takes off output for panel temperature (0.29 percent per degree above 25 °C, with the panel temperature from the sun, air temperature and wind), removes a system-loss allowance of 18 percent and applies an inverter efficiency of 96 percent. These are defaults, and the wizard does not change them. The result is a modeled yield for your site, not a roof survey or an installer guarantee.
PV and battery methodNot as separate effects. Shadows from trees, neighboring buildings and chimneys are not calculated, and the 18 percent system-loss allowance, which also covers dirt and wiring, is the only stand-in for them. Inverter clipping is not modeled either: the wizard does not ask for an inverter size, so a large array on a small inverter is not capped. Weather arrives in hourly values, so short peaks from passing clouds are averaged out.
PV model scopeYou enter the usable capacity, the energy you can actually draw. Datasheets often list a larger total figure as well. The model keeps the battery between a 10 percent floor and a 100 percent ceiling of the figure you enter, so with the defaults 90 percent of it can be cycled. If your datasheet's usable figure already excludes the maker's reserve, the floor takes a second slice and the simulated window is a little smaller than the datasheet suggests. The floor and ceiling are defaults the wizard does not change. Power limits and efficiency also constrain each hour.
Battery scenariosPower and losses are modeled, standby consumption is not. The battery charges and discharges at up to 0.5C (a 10 kWh battery at up to 5 kW) with a round-trip efficiency of 92 percent, split equally between charging and discharging. These are defaults the wizard does not change, so capacity is the one battery limit you vary. There is no separate standby term. EV charging has its own configured power and efficiency.
PV and battery scopeThe standard scenario result does not calculate battery aging, replacement schedules or replacement cost. It applies the configured efficiency, SOC range and power limits. A financial comparison that includes degradation or replacement needs a separate sourced assumption.
Battery cost limitsCompare several supported capacities against the same PV profile, household demand, EV schedule and tariff. Inspect self-consumption, imports, exports, dispatch cost and unused capacity. The best size depends on those inputs; the result does not promise a universal optimum or include battery replacement economics.
Compare PV and batteriesThe optimizer plans one day at a time against that day's 24 hourly prices and picks the cheapest plan for the battery and the car, inside their power, charge and reserve limits. What it minimizes is electricity cost. It does not minimize carbon, equipment wear or total installed cost. It runs only with a dynamic tariff and a home battery. Without both, simple rules run instead.
Energy management methodOne calendar day. It sees that day's solar production, demand and 24 hourly prices, which mimics a day-ahead market where tomorrow's prices are published the day before. Battery charge carries over to the next day, and the battery starts the year half full. The optimizer puts no value on charge left at midnight, so it does not hold energy back for tomorrow's prices. That is different from a full-year optimum with perfect foresight.
Tariff and optimizer scopeWithin the day it plans, yes, and exactly. It is given that day's solar production, demand and prices, where a real controller would work from forecasts. Demand covers heating, cooling, ventilation and hot water from the thermal simulation, and it is fixed. A run is therefore a scenario with supplied data, not a deployed controller facing uncertain forecasts, and a real saving would be smaller.
How dispatch worksThe battery, the car (charging, and sending power back to the house when vehicle-to-home is on), and the grid import and export. Solar production and demand are inputs. Heating, hot water and pool demand are fixed: the optimizer never moves a heat pump, a floor slab or a pool to a cheaper hour.
Supported dispatch decisionsYou do not pick a mode. It follows from your setup: the optimizer runs with a dynamic tariff and a home battery, and simple rules run otherwise. The rules know nothing about prices. When solar production is above demand they charge the battery from the surplus, then the car if it is home and short of its next trip, then export the rest. When demand is above production they discharge the battery, then the car if vehicle-to-home is on, then import. The rules never charge the battery from the grid; the optimizer can, when prices are low. A comparison between the two mixes the price structure with the control, so read it with that in mind.
Rules and optimizerThe run keeps the rule-based result and records the reason, so a fallback is not an optimized outcome. If the car's week leaves too little time at home to charge, the run stops with an error and reports no result.
Dispatch and fallbackWith a dynamic tariff the import price is the spot price (floored at zero when the spot price is negative), plus a network fee, plus VAT, and never below a minimum import price. Export is a share of the spot price and never below zero, so a negative spot price earns nothing and costs nothing. A fixed tariff uses the import and export prices you enter. Every run also adds a fixed annual grid charge, 432 EUR by default. The wizard shows each figure and lets you change it. At the moment the defaults come from a Luxembourg dynamic tariff dated January 2026, so enter your own contract values if yours differ. These are model assumptions, not a guarantee that every supplier bill is represented.
Tariff assumptionsThe model enforces the power and state-of-charge limits of the battery and the car. It applies no cap to what you import from or export to the grid, and it does not model peak-power fees or supplier restrictions. It also does not certify your contracted grid capacity, the distribution connection, protection devices or export permission. Those need a check with the network operator and installer.
Dispatch constraintsAn ERA5 run uses EPEX prices from the same calendar year as its weather. A typical-year run uses the 2024 reference price year. The price series is matched to the simulated calendar position and converted from UTC to the weather file's local standard-time offset. 29 February maps to 28 February when the price year is not a leap year.
Dynamic tariff availabilityNot automatically. The optimizer works with exact knowledge of each day's production, demand and prices, and with ideal control of the battery and the car. A real energy management system works from forecasts, needs compatible hardware, device permissions and communication, and has its own settings. The modeled saving probably overstates what a real product achieves, and it says nothing about any particular product.
What the optimizer representsIn a simplified way, yes. Run the same house twice with the same weather year. In the first run use a fixed tariff and a home battery, so the simple rules run, like a plain inverter and battery. In the second run use a dynamic tariff and the same battery, so the optimizer runs. Compare the annual electricity cost, the grid import and export, and the self-consumption. The difference estimates what price-aware control could be worth to your house under that tariff. It mixes the price structure with the control, it probably overstates what a real product achieves, and it says nothing about any particular product.
Energy management and tariffsYou enter the car's outings for each day of the week: departure hour, return hour and distance. The same week repeats all year, and the car charges, or sends power to the house, only while it is home. The wizard has no connection to vehicle data and no schedule-upload format. The run uses the week you saved.
EV and V2H modelingDriving energy is taken out of the modeled car battery. Before each outing the car must hold that trip's energy plus a reserve, 30 percent of the battery by default. If the week leaves too little time at home to charge, the run stops with an error instead of reporting a result. Check the saved week and the EV results rather than assuming that a real vehicle meets every morning target.
EV charging assumptionsThe model can represent a bidirectional vehicle and charger configuration, but it does not query or verify vehicle compatibility. V2H requires a compatible vehicle, charger, firmware, installation and local permissions. Confirm the exact combination with the manufacturers before purchase.
V2H model scopeThe optimizer holds vehicle-to-home energy to about 2,000 kWh a year. That is a modeling assumption to stop the simulated car from being cycled for small price gains, not a manufacturer or warranty figure, and we have no published source for it. The simple rules have no yearly limit, only the car's reserve. Power limits and charge and discharge efficiency are modeled. Battery aging and warranty impact are not calculated.
V2H assumptionsThe model does not make every V2H result a paired baseline comparison automatically. Create two scenarios with the same building, weather, driving schedule, tariff and equipment, changing only V2H. Then compare grid flows and operating cost while keeping the assumptions visible.
Compare EV scenariosAn indoor pool has a separate basement pool zone, dedicated pool heating and a pool-hall air system. An outdoor pool is exposed to weather and uses different heat-loss and heating assumptions. Compare indoor and outdoor cases separately because their boundaries differ.
Pool modelingYes, unless the house has a polyvalent 4-pipe heat pump. On that plant the pool hangs on the same hot loop as the house, so one machine serves both. With any other heating system the model gives the pool a second, separate air-source heat pump, sized for the pool, and counts its electricity in the result. The wizard says so on the equipment step and does not offer a gas pool boiler.
Pool heatingPool water losses depend on whether the surface is covered, exposed hours, water temperature and weather. The indoor pool uses a preset cover schedule. Outdoor-pool inputs include cover type and season. These choices affect modeled heat loss; the current result does not establish a universal cover saving.
Pool inputs and limitsThe indoor-pool system includes a modeled pool-hall air system and dehumidifier electrical load in supported configurations. It does not establish the actual hall's moisture migration, mold risk, condensation safety or ventilation design. Those need project-specific building and mechanical checks.
Indoor pool scopeIn the production indoor-pool case, the basement pool zone is thermally coupled to the floor above through the modeled surfaces. Heat from the pool zone can therefore change the adjacent house zone's heating demand. The model does not resolve every local temperature gradient or door-opening event.
Pool and house interactionRecovered heat can reduce another modeled heat demand, but producing and moving that heat still uses equipment. Include compressor, pumps, fans, backup heat and transfer losses in the chosen system. A heat-recovery benefit is not zero-cost energy.
Pool heat recoveryHot water has its own 200-liter tank, separate from the heating loop, and the tank is held at 55 °C. Both are defaults the wizard does not change. Daily demand follows the household size you enter: roughly 200 liters a day for four people, on a fixed morning, midday and evening pattern. The heat source (a small heat pump water heater with an electric element behind it, the element alone, or the boiler) and the household size change consumption. The tank loses heat at a fixed rate, and the default profile is not a measurement of your taps.
Inputs and schedulesBackup water heating is modeled: the tank has an electric element that covers what the heat pump cannot. No periodic disinfection cycle is simulated. The tank is held at its setpoint, so the small amount of electricity a weekly hygiene cycle would use is not in the result. Whether your installation needs one, and at what temperature, follows the tank and heat-pump manufacturer's instructions and local requirements.
Hot-water modelingEach run is calculated by EnergyPlus version 25.2.0, a building energy simulation engine developed with funding from the U.S. Department of Energy. EnergyFlow is independent of the EnergyPlus developers and the Department, and neither endorses it. The engine works from your inputs and from modeling choices that we list openly: floor-level zones, representative equipment instead of named products, a typical or reconstructed weather year, and electricity flows worked out in whole hours. A run compares options for your house under identical conditions. It is an estimate, not a forecast of your next bill.
Model assumptions and limitsNot exactly. A run compares options for your house under identical conditions. It is not a forecast of your next bill, and we do not present it as one. Real bills depend on weather, tariffs, installation quality, controls and how your household uses the house. Use the difference between two runs rather than a single absolute figure, and treat a small gap as a tie.
Model assumptionsWeather and schedules change heat demand, cooling, PV yield and costs. The product supports comparisons across weather or schedule inputs, but this page does not publish a measured sensitivity range. Create paired scenarios that vary one input and report the complete setup; do not label the difference as a statistical confidence interval.
Comparison setup examplesThe inputs most likely to change a comparison are those that directly change the energy balance: envelope areas and U-values, glazing and shading, weather, setpoints, schedules, equipment performance and tariffs. Their relative effect depends on the house. There is no published universal percentage ranking for missing inputs.
Model assumptionsElectrical kWh measure electricity consumed by equipment or imported from the grid. Delivered heat is thermal energy supplied to a space or water system. COP is the ratio of useful heat delivered to electricity used over the stated boundary. PV production, battery discharge and grid imports are flows; do not add them as if they were the same end use.
How to read resultsNo. EnergyFlow compares modeled scenarios. It is not an energy performance certificate, a building permit check or a subsidy decision, and it does not size a final installation, inspect existing emitters or approve electrical and hydraulic connections. Use a qualified designer or installer for those decisions.
Model assumptions and limitsEnergyFlow is for houses in France, Belgium, the Netherlands, Luxembourg, Germany, Austria and Switzerland. The United Kingdom is the next country after those. Every other country, Italy, Spain and Portugal included, can join the waitlist. The wizard asks for your country and postal code first, because weather, electricity prices and typical construction differ from one country to the next.
How the model worksFor one house, Free includes three lifetime previews with at least ten minutes between starts. A preview shows estimated annual energy cost rounded to EUR/year and annual space-heating demand rounded to kWh/year. The latest successful result stays visible; history shows dates, weather year and status. Comfort appears only when the saved temperature data supports a categorical assessment. Free does not include charts, reports or PDF downloads, CSV exports or comparisons.
Free preview detailsSingle House covers one house, five simulations and one chosen saved-run PDF, which you can download again at no extra charge. Full Project covers one house with unlimited simulations, comparison of up to four scenarios, all reports and hourly CSV export. Both plans cover all the equipment, pool and EV/V2H included. The pricing page loads current prices from the same catalog used by checkout.
Compare plans and current pricesThere is no access deadline. You pay once and keep using your house within your plan: five simulations and one PDF with Single House, unlimited simulations with Full Project, subject to fair use. Your house, results and reports stay while your account exists. If we ever close EnergyFlow, we give at least 3 months' notice by email and keep your PDFs downloadable until then. These are one-time purchases without automatic renewal. The terms page has the purchase, withdrawal and refund conditions.
Pricing and termsThis release has no document upload, so there are no certificates or plans to process. Your house description, results and reports are stored against your account, with application data hosted in the EU. Some services, such as sign-in and payment, can involve processing outside the EU, and the privacy notice lists them with the safeguards used. A paid house is kept while your account exists, and a free account with no purchase keeps saved data for 12 months of inactivity. Deleting your account removes your house and run data and your private report files, and you can ask for earlier deletion by email. Accounting records are kept separately where the law requires it.
Privacy noticeA saved run retains its scenario inputs and results for display. That does not by itself preserve the exact software, equipment database, weather file and tariff artifacts needed to reproduce it byte for byte. The public service does not promise a historical rerun against the original model version.
Model and run inputsInsulation slows heat transfer in both directions. Solar gains through glass, people and appliances can add heat faster than shading, ventilation or cooling removes it. The energy rating and the home's summer response answer different questions.
Summer comfort in efficient homesAn energy label is produced under its own national calculation method. It is not a room-by-room prediction of temperature during a chosen heatwave. EnergyFlow's dynamic temperature scenario is a separate estimate with its own weather, geometry and schedule assumptions. Check your own country's certificate method for the exact label scope.
Energy rating and summer comfortYes, compare supported external-shading and ventilation assumptions before adding active cooling. Keep weather, occupancy and comfort targets fixed. The model does not establish window security, noise constraints, indoor air quality or whether a specific ventilation retrofit is practical.
Compare summer measuresThe operating-cost estimate needs your building inputs, cooling setpoint and schedule, selected cooling system, weather basis and dated electricity tariff. Installation cost is a separate quote. EnergyFlow does not publish a universal AC cost or include installation, maintenance or subsidy figures without sourced inputs.
Cooling cost methodThrough a floor, yes, if the house has underfloor heating. Floor cooling uses the same floor circuit, so the wizard offers it only with underfloor heating and refuses it with radiators. With radiators, choose split air conditioning or no cooling. The model cannot confirm that your existing floor, pipes and controls are suitable for cooling, and its dew-point guard is not a site safety certification. Have the installed system checked by a qualified professional.
Cooling options and limitsNo. Ventilation replaces air and can recover heat from the exhaust. Air conditioning actively removes heat from the building. The model does simulate a summer bypass on a heat-recovery unit: when the room is warm and the outdoor air is above 12 °C and cooler than the room, the exchanger is bypassed so cool night air comes in unwarmed. That helps, but it does not make a ventilation unit an air conditioner.
Heating, cooling and ventilationThat depends on the building's useful heat demand, existing boiler efficiency, heat-pump performance, backup heat and the two energy prices. Compare both systems at the same weather, setpoints and hot-water demand, then vary dated fuel and electricity tariffs. The model cannot promise a universal winner.
See a worked exampleThe simulation can compare a radiator distribution and selected flow temperature, but it cannot inspect radiator size or condition. A room-by-room heat-loss and emitter-output check is needed to decide whether the real radiators can meet demand at the proposed water temperature.
Radiators and heat pumpsThe run follows its selected typical or historical weather file. It does not forecast future extremes or guarantee behavior in a weather event outside that file. Compare another available weather year or design condition when extreme performance matters, and state exactly which file was used.
Weather assumptionsNot from the standard floor-level model. It reports temperatures for modeled zones, which may represent a whole floor rather than an individual bedroom. Indoor humidity and local airflow are not enough to certify bedroom comfort. Use a room-level design or measurement for that question.
Zone resolutionA blind closes when the sun on its window is above 300 W/m² and the outdoor air is warmer than 10 °C. There is no calendar, so a bright day in April closes the blinds and a bright day in January does not. The temperature lock keeps the free solar heat of winter: closing the blinds on sunshine alone all year would raise the heating demand of a well-insulated house by more than a third and save much less cooling. The cost is that a small house with a lot of glass can still overheat on a bright cold day in March, because its blinds stay up. The model does not look at indoor temperature, wind or rain, and the threshold and the lock are fixed in the model, not wizard fields. Roller shutters use the same sun threshold but close only when the outdoor air is above 20 °C, so the rooms keep their daylight on cooler days.
Heating and cooling inputsOnly in a house with no cooling. Where there is floor cooling or split units, the windows stay shut in the model, because the cooling already holds the setpoint. Without cooling, the rooms are aired from 23:00 to 06:00 whenever the room is above 23 °C and the outdoor air is above 12 °C and cooler than the room. The air in the room is then exchanged 2 times an hour in total, leaks included. That is the night-window figure of the German standard DIN 4108-2, which we read through a software vendor's manual and a research paper, not in the standard itself. On a 1975 house with no cooling it lowered the peak from 33.0 to 32.5 °C and the hours above 26 °C from 817 to 614. On a 2010 house it went from 30.6 to 28.4 °C and from 1803 to 462 hours. A house with 50 m² of glass and no cooling still overheats. The model airs every occupied floor, the ground floor too, and it ignores rain, wind, noise and security. If you keep the windows shut at night, your house will be warmer than the run says.
Summer comfort comparisonsNo. Describe each floor's outside geometry and construction. Interior partitions within one modeled zone are represented through aggregate thermal mass rather than drawn individually. Use a separate zone for a space with different conditions, such as an unheated garage or pool hall, when the supported configuration allows it.
Floor-level modelThe current simplified envelope uses glazing area by exterior face and floor, with orientation, glazing properties and supported shading. Exact window coordinates within a wall are not a separate input. Local shadows and detailed solar distribution can still matter in the actual building.
Window and solar assumptionsAn opening between connected floors represents air exchange between those zones. The model uses the opening and its airflow assumptions; the staircase's exact plan position is not resolved. It does not simulate local currents, stratification or door-by-door use.
Inter-floor airflowNo furniture layout is required. The model uses an aggregate internal-mass assumption to represent heat stored in interior surfaces and contents. That simplification can affect temperature swings and peak loads, so it should be treated as an assumption rather than a furniture inventory.
Thermal massPeople, lighting and appliances are represented through household electricity, internal gains and schedule assumptions. The wizard lets users choose supported schedule inputs; missing schedule values are filled from defaults and the values used are saved with the run. The model does not track occupant movements room by room.
Schedules and household demandNo. The model uses a representative machine of each type and size, built from manufacturer data for one typical range and shown without a brand, for example air-source heat pump, 10 kW class. A selected profile is not a promise that a specific installed unit will match every modeled point, and two units of the same size from different makers can differ in how fast their efficiency falls as it gets colder outside. A broader catalogue of named products is only a possible future addition, with no delivery date or current entitlement.
Supported equipmentSeveral values have no input field in this release, and the model uses its default: the backup heater (8 kW), the hot water temperature (55 °C) and tank size (200 liters), the battery charge and discharge power and its efficiency, the PV system losses and inverter efficiency, and the settings of the ventilation unit.
Supported equipment