Run a room-by-room heat-load calculation

The room-by-room heat-load calculation is Reonic's most accurate heat-pump sizing path. You either capture the building with a LiDAR scan on iPad, import a photogrammetry scan, or enter the rooms manually, then validate per-room geometry, materials, windows, doors, and heating systems in the Portal. Reonic runs the calculation and produces a DIN-compliant report with normative heat loads, hydraulic-balancing values, and radiator-swap recommendations. This is the residential heat-pump planning path.

Residential only. Heat pumps are a residential product, so this flow applies to residential projects.

Before you start

• Your account needs heat-pump planning enabled, which turns on the Roomwise Building tab in the Portal and the room-capture steps in the Mobile App. If the Roomwise Building tab is not visible, contact your Reonic account manager.
• For the LiDAR scan path: a LiDAR-equipped iPad Pro or iPhone Pro with the Mobile App installed. Android and non-LiDAR Apple devices use manual entry instead.
• For manual entry: room measurements (length, width, height) for every heated room, plus material and built-year information for walls, windows, and the roof.
• The project must already exist, and the heat pump must already be a component on it.
• For German projects, DIN-EN-12831 is the default calculation mode. UK projects use a parallel UK calculator. Italy has country-specific material options. France and Spain use the shared materials.

Choose the right heat-load path

Reonic offers three paths to size a heat pump. Pick the right one before you start capturing data.

1. Simple simulation — estimates the heat load from base building data (heat transfer, built year, area, occupants), or uses a manual external heat-load override if you have one. The least accurate of the three.
2. Heat-load indication via the building envelope — typological U-values per built year. A real sizing basis without per-room detail.
3. Room-by-room heat load / Hydraulic balancing — the full DIN-EN-12831 calculation per room. The only path that produces the hydraulic-balancing report, radiator-swap recommendations, and the documentation needed for KfW or BAFA funding.

Use the room-by-room path when accuracy matters, when you need a normative report, or when the customer asks for hydraulic balancing.

Capture the building with a LiDAR scan on iPad

The fastest field-capture path. Hand the iPad to a field worker on-site. They walk every room and capture geometry, walls, windows, doors, and existing radiators.

1. Open the Mobile App, tap Projects, and open the customer's project.
2. Go to Heatload. The Overview shows setup tiles: Existing heating, Building properties, Basic materials, and Scan.
3. Fill Building properties: built year, inhabitants, airtightness, n50 / volume flow, soil depth, shielding, heat-bridge factor, target temperature.
4. Fill Basic materials: pick the standard material per element. Set a default valve here so every radiator gets an end-of-flow setting value without setting it per radiator.
5. Add stories. Tap Add story and pick a story type (Cellar, Ground floor without cellar, Ground floor, Intermediary floor, Attic). Only one Cellar and one Attic (the top story) are allowed per building. Intermediary floors are arbitrary and auto-named "Upper floor 1, 2, 3…".
6. From a story, tap Start scan. You're asked whether to continue from an adjacent already-scanned room or start an independent scan. Pick Start new scan for the first room. The scanning view opens with the live LiDAR feed, an occluder UI, and a Take photo affordance.
7. Walk around the room slowly. Watch for tracking-state warnings: Excessive motion (slow down), Insufficient features (move to a textured corner, especially in white-walled rooms), Relocalizing (don't move), Initializing (wait), Device too hot (cool down), and Scene size limit exceeded (you've scanned too large an area).
8. Tap Stop when the room is captured. The app combines the captured rooms into one story scan.
9. For the next room in the same story, choose Continue from adjacent. The new scan aligns with the rooms you already captured, so the whole floor stays in one coordinate frame.
10. Repeat for every room. When the story is complete, tap Finalize on the Finalize scan view. The scan uploads and lands in the Portal's Roomwise Building editor.
11. Adjust per-room fields on-site from the rooms list if you want (segmented control: Walls / Floors / Roof / Heating / Room). The detailed review happens in the Portal.

Pro tip: LiDAR scanning is battery-intensive. Start the visit with a fully-charged iPad and bring a power bank for larger homes. Scan data is held on the device, so the app resumes mid-walk if it's interrupted.

Note: You can capture and edit a whole building fully offline. Stories, building base values, basic and existing-heating data, and location reference values are available on the device, and your edits (create or update a story or room, change building data or materials, finalize a story scan) apply to your local copy right away. When you regain a connection, your edits sync to the server automatically. A field worker can scan a basement or a remote site with no signal, then sync once back online.

Note: The Mobile App captures the scan. To see the calculated kW result and the report, tap Data review & results on the Overview. It opens the Portal in a new tab on the results view, where the detailed review and editing happen.

Capture the building without LiDAR

Use this path on Android, on iPads without LiDAR (older models), or when the site can't be scanned (heavy furniture, low light, customer preference).

1. On Mobile or Portal, open the project and fill Building properties and Basic materials as above.
2. Go to Roomwise Building (Mobile: Heatload tab; Portal: Roomwise Building tab on the project detail).
3. Tap Add story for each floor, picking the story type. The same uniqueness rule applies: one Attic, one Cellar, multiple intermediary floors.
4. From a story, tap Add room (or +). The empty room editor opens with no scan data backing it.
5. Fill the room data manually:
   • Identity — name, room type (Normal, Bath, Kitchen, Storage, …).
   • Geometry — tick Rectangular if it applies, then enter length, width, area, and height.
   • Thermal — target temperature, air-exchange rate.
   • Walls — one entry per wall: length, height, and what the wall faces (Outside air, Heated room, Unheated room, Other building, Outside ground), material, U-value, insulation thickness, and percentage to ground where relevant. Internal adjacency to another heated room is set by linking the wall to that room (shown as Adjacent), not by a separate facing type.
   • Windows & doors per wall — the editable window fields are width, height, and material (the material carries the U-value). Orientation follows the wall the window sits on. Frame type and g-value are not editable per-window fields; the window entry accepts width, height, and material only.
   • Roof, ceiling, floor — see Validate roofs, ceilings, and floors below.
   • Heating system per room — radiator or underfloor heating (the only two options), radiator count, and valve presence. Flow and return temperatures are not per-room: they're set building-wide in the radiator-swap / Results step (see Set flow and return temperature below).
6. Save and repeat for every room in every story.

Pro tip: Manual entry is always available. For new builds where no walls exist yet, it's often faster than waiting on a site visit. You can also save a room with just a name and story as an in-progress placeholder. The calculation warns until you fill its geometry.

Note: If Add room does not appear on the Mobile App, do the manual entry in the Portal's Roomwise Building tab instead, or contact your Reonic account manager.

The U-value lookup is the same whether you scanned or typed. Reonic resolves it from the material and built-year against its standard library (or the UK library in UK mode), and you can override an explicit U-value per element.

Validate the captured data in the Portal

After the scan or manual entry, the detail work happens in the Portal, the desktop review surface for heat-load results.

1. In the offer, open Building and heat load and start the planning.
2. Choose Room-by-room heat load / Hydraulic balancing.
3. Reonic shows the imported scan with all stories. The story list shows each story's name, built year, and room count. Click into a room to open its editor.

Adjust building properties and base materials

At the top you see the building properties from the field visit, along with the base materials. Both are editable:

• Correct the target temperature, building type, or other key data if anything changed on-site.
• Confirm or change the default valve for radiators. This is the value used wherever you don't set a valve per radiator.
• Choose custom materials defined in your simulation settings, or stay with the standard values. The standard library covers DE and UK, Italy has country-specific options, and custom materials let you define your own U-values when your catalogue differs from the norm tables.

Walk through every room

For each story, click every room one by one. Reonic jumps into the selected room and shows:

• Length, width, ceiling height, and area.
• Room type with a preset temperature: bathroom 24 °C, storage room 16 °C, normal rooms 20 °C. Mark unheated rooms (e.g. utility, garage) as such. They don't need to be scanned or fully described.
• An optional custom temperature per room if the preset doesn't fit (e.g. a workshop at 18 °C).
• Radiators with type and dimensions, optionally with a photo from the scan.
• The valve per radiator, if you didn't set one centrally.

Note: Unheated rooms with radiators count as boundary conditions, not as separate heat-loss surfaces. Mark the wall that faces the unheated room as Unheated room in the heated-room editor, and you're done.

Fix wall anomalies

The scan detects walls automatically. Reonic flags anomalies as yellow exclamation marks and real errors as red.

Classic anomaly: model end detected. The Portal marks walls where the model ends despite the wall being set as a heated room. Common causes:

• Semi-detached house — switch the wall to another building.
• Adjacent room not scanned (stairwell, utility room) — switch the wall to unheated room.
• An actually-heated but unscanned room — mark the wall accordingly.

For larger adjustments, split sub-walls so one wall can go partly to another building and partly to an unheated stairwell.

Doors in heated walls. Doors in walls between heated rooms aren't relevant for the heat load. Doors to unheated rooms also aren't counted per the standard. You enter only doors that face the outside.

Balcony doors marked as doors. The scan often labels balcony doors as doors, but their U-value belongs to a window. Reonic warns when there are multiple exterior doors on one floor. Click the wall, open the element, and switch from door to window. The area stays the same.

Photogrammetry-sourced walls. If the rooms came from a photogrammetry import, you edit them exactly like scan-sourced rooms. Flip a wall's facing type (Outside air, Heated room, Unheated room, Other building, Outside ground), and for an internal wall, link it to the adjacent room (shown as Adjacent) rather than picking a facing value. Rooms are edited the same way regardless of how they were captured.

Validate roofs, ceilings, and floors

Pitched roof. Reonic takes the length and slope length from the scan and multiplies them for the roof area. For heavily angled roofs the system combines several slopes into mixed values. Check the values. This is the most common scan weakness.

Note: Sloped roofs are calculated from the slope length and slope width.

Roof windows and dormers. The scan doesn't detect these automatically. Per roof slope, enter the total area of roof windows and the dormer width plus slope length manually. Keep the summed dormer widths on a slope within that slope's length: if the dormers add up to wider than the roof is long, the calculation stops with a dormer-length error. Check the widths against the sloped-roof length before you run the calculation.

Ceiling properties. Above the topmost heated room, set the ceiling to unheated room (loft) or no room (flat roof). For a very small loft the impact is minor, and unheated room is still the clean default.

Floor properties. Unheated basements don't need scanning. In the ground floor, set the floor to adjacent unheated room with the corresponding area. For ground-touching walls (typical in German basements with partial earth contact), set the percentage to ground on the wall.

Add rooms manually if the scan missed one

If a room is missing from the scan, add it manually. Enter just the heated room volume plus the walls and components that cause heat loss. More work than a re-scan, but always possible.

Pro tip: Manual rooms are best as a last resort. If multiple rooms are missing or the scan is patchy, re-scanning the affected story is usually faster than rebuilding the geometry manually.

Split or copy work between rooms and stories

• Split a scanned room — open the room and use the room editor's split affordance to break one captured volume into two heated rooms. Useful when the scan fused a kitchen and dining area into one polygon.
• Build each story directly — each story is built on its own. For repeating layouts across floors, re-enter the rooms per story.
• Name a story — every story carries an editable name. Override the auto-generated "Upper floor 1, 2, 3" with "Erdgeschoss", "Dachgeschoss", or a custom label if your offer documentation needs it.

Run validation and the heat-load calculation

After the walkthrough, click Validation. Reonic splits the messages into two classes:

• Errors — missing values, empty stories. Correct these before the calculation runs.
• Anomalies — warnings that can sometimes be ignored. Reonic links each one directly to the affected room.

Common anomalies: no valve set (preventable via the default valve in base materials), exterior doors that should be windows, loft warnings, and the "At least one exterior wall in a heated room must exist when there are multiple exterior walls in the room" check. The last one fires when a room has multiple outward-facing walls but none is structurally an exterior wall, usually a wall-type misclassification you fix in the wall editor.

Once errors are clear, Reonic moves you to Heat load and radiator swap.

Set flow and return temperature

Set the flow and return temperature separately for radiators and underfloor heating. The dropdown shows how many radiators are undersized, marginal, or adequate at the chosen spread.

Walk the radiator-swap recommendations

1. For each radiator, Reonic shows the target room temperature, the room heat load, and the current heating capacity with a colour indicator: green (adequate), amber (marginal), or red (undersized).
2. For radiators marked red, choose a replacement. Reonic suggests radiators of similar dimensions from its catalogue.
3. Alternatively, create a custom radiator with your own name, capacity, and radiator exponent.

Pro tip: Prefer catalogue suggestions over custom entries. The catalogue values are calibrated, and you avoid typos in the radiator-exponent figure that propagate into the hydraulic-balancing math.

How chosen radiators land in the offer

The radiators you confirm in the swap step, both kept originals and catalogue replacements, appear on the offer as per-room line items. Reonic writes one entry per heating system (e.g. "Room 1 radiator + TRV valve", "Room 2 underfloor-heating loop"), visible on the offer's heating-layout view once the calculation is signed off.

You don't drag radiators into the bill of materials manually. Confirming the swap recommendations and signing off the checklist is the action that adds them. If you change the radiator selection later, re-open the room-by-room editor, adjust the radiator choice, and re-sign the checklist. The offer's line items update to match.

Note: Custom radiators (entered with your own name, capacity, and radiator exponent) flow into the offer the same way as catalogue picks. They appear as line items with the name you typed. If the customer needs an article number on the offer PDF for procurement, prefer catalogue radiators where possible.

Generate the heat-load report

In the last step, Reonic generates a DIN-compliant report with:

• Normative heat loads per room.
• Total building heat load (excluding hot water).
• Hydraulic balancing including setting values and flow rates per radiator.
• A summary of the radiators swapped.
• A list of components with high heat losses you can give the customer as a renovation recommendation.

After saving, the report lands in the project files and can be reused for KfW funding applications or any other subsidy that requires a hydraulic-balancing certificate.

If you only need the heat-load summary (without the hydraulic-balancing per-radiator detail), the calculation result is also available from the heat-load indication step, but it won't include the radiator-swap values. For most KfW-relevant cases you want the full room-by-room report.

Set the bivalence point

The bivalence point is set on the heat-pump component itself, not in the heat-load editor. Open the heat-pump component, find the Bivalence temperature field, and either:

• Leave it at Reonic's default of −6 °C — below that outside temperature the backup heating rod takes over (a bivalent setup).
• Set a different bivalence temperature to move that handover point (raise it for an undersized pump; lower it for a pump sized for very cold days). A fully monovalent setup — the heat pump covering the entire load with no rod — depends on the pump and rod configuration, not this field alone.

The standard heat load (including hot water) is always larger than the heat load at the bivalence point. The standard value is the design load for the coldest day of the heating season, while the bivalence-point value is the load at the higher outside temperature where the backup heater kicks in. Both are visible in the report.

Things to know

• The room-by-room calculation is the most accurate of the three methods. It captures each room's geometry, materials, and heating system individually. The building-envelope indication is next, and the simple simulation is for indicative cases. A heat-load report with the per-room and per-radiator detail for KfW or BAFA comes only from the full room-by-room calculation.
• Walls and windows are required inputs. For the room-by-room calculation, walls and windows are what drive the per-room heat load. Add extra insulation values only when the building was retrofitted with insulation that isn't reflected in the built-year U-values: click the wall, window, or roof element and enter the additional thickness, and the U-value adjusts. For a WDVS on a brick wall, pick the brick wall material and set the additional insulation to the WDVS thickness and material, or enter the U-value directly.
• Valve setting values are mandatory for funding. The hydraulic-balancing certificate that KfW and BAFA accept needs a valve with a setting value on every radiator. Set the default valve in basic materials so every radiator inherits it, and override per radiator where you've installed a different model.
• Reonic supports air-water, water-water, and soil-water heat pumps, with modulating, single-stage, and multi-stage modulation. Air-to-air units are recognised for German BAFA subsidy purposes but are planned outside the room-by-room editor: for multi-split air-to-air retrofits, capture the equipment as an additional component.
• Hydraulics are designed outside Reonic. Pipe sizing, buffer-tank sizing, and mixing-valve configuration happen externally. Enter the chosen specs (buffer-tank size, additional components) as line items on the offer. The room-by-room editor produces the hydraulic-balancing values (valve settings, flow rates per radiator). The report uses litres per hour (l/h) in line with DIN-EN-12831. Reonic models the heating side of the heat pump; reverse-cycle cooling capability is captured separately.
• Hot water is part of the building total. Reonic estimates it from the number of occupants. The per-room loads are space-heating only, and the bivalence-point load excludes hot water, which is why it sits below the standard load.
• Each building is one project. One project equals one building. For a Mehrfamilienhaus with one shared heat pump, model the envelope as one project and approximate the per-flat loads as rooms, and allocate per flat in the energy layout. For multi-building offers, create separate projects per building and bundle the offers on the customer side.
• Edit on one device at a time. To avoid a mobile edit overwriting a Portal save, edit the room-by-room data in one place at a time.
• Edit before signature. Once a variant is signed, the offer and the heat-load calculation that backed it are locked. Fork to a new variant and re-run the calculation if the customer changes scope, then send the new variant for re-signature.
• The heat-pump electricity consumption is calculated for you. Annual heat-pump electricity is roughly the annual heat demand (heating plus hot water) divided by the chosen heat pump's SCOP. The figure appears in the simulation results panel and on the offer PDF.

Pro tip: If the offer shows the heat pump never paying back, it's almost always an input issue. The profitability page reads the annual heat demand from the room-by-room editor, so if room sizes or U-values are off, the demand is mis-sized and the payback collapses. Cross-check the computed annual kWh against the customer's current gas or oil bill. The other lever is the Economics page horizon: the offer PDF caps the breakeven page at a set number of years (the Customise pages modal). If the true breakeven is beyond that horizon, extend the limit.

Need help?

• Step-by-step questions about this flow → contact your Reonic account manager.
• Feature requests or something missing → send a note to your Reonic account manager.
• Bug reports → include a screenshot and the URL where it happened in your support email.

Last updated on August 4, 2026