SketchUp · Passive Solar
Modelling Net Zero Concepts in SketchUp: Solar & Massing Basics
You don't need Autodesk Forma to think about sun angles. SketchUp can get you 80% there in 20 minutes — here's exactly how to set up shadow studies, calculate passive solar overhangs, and extract real energy insight from a tool you already own.
Why SketchUp Is Underrated for Net Zero Thinking
Ask most architects where they do solar analysis and the answer is usually EnergyPlus, IDA ICE, or increasingly Autodesk Forma. But SketchUp solar modelling — when set up correctly — gives you a surprisingly robust picture of how a building interacts with the sun at the earliest design stage, when decisions still cost nothing to change. The moment geometry is right, geolocation is pinned, and shadow studies are running, you have an analytical tool powerful enough to guide critical massing choices on any project, in any climate, anywhere in the world.
This article is a practical, step-by-step guide to doing exactly that. We'll cover geo-location setup, solstice shadow studies, passive solar orientation rules, overhang calculation by latitude, and the Sefaira Lite plugin for energy feedback. We'll also be honest about where SketchUp's limits kick in and when you should move to a dedicated climate-analysis platform. The whole workflow, from blank model to first actionable solar insight, takes under 20 minutes.
The 80/20 Case for Early-Stage Solar Analysis
Studies in building energy performance consistently show that 80% of a building's lifetime energy outcome is determined in the first 20% of design time — the concept and schematic stages. The Chartered Institution of Building Services Engineers (CIBSE) in the UK calls this the "frozen decisions" problem: by the time detailed simulation is warranted, fundamental massing choices are locked in. SketchUp lives exactly in that critical early window. It is not a substitute for full dynamic thermal modelling, but it is the right tool for the right stage.
What SketchUp Actually Computes
SketchUp's shadow engine is a true geometric solar calculator. Given a precise latitude, longitude, and time zone, the software computes the sun's altitude and azimuth for any date and time using standard astronomical equations. It then performs real-time ray-casting to project accurate shadow geometries across your model. This is the same fundamental calculation at the heart of every solar analysis tool — the difference is that dedicated energy software layers climate data, thermal properties, and HVAC simulation on top. For massing decisions, you rarely need that extra layer yet.
A Global Tool for a Global Problem
Net zero building targets now exist across virtually every major economy — the EU's Energy Performance of Buildings Directive, India's National Mission on Sustainable Habitat, Australia's NCC energy efficiency provisions, and the International Energy Conservation Code in the United States. Each framing differs, but the underlying physics of passive solar design is universal: the sun rises in the east, sets in the west, peaks in the south in the northern hemisphere (north in the southern hemisphere), and its altitude changes dramatically by season. SketchUp respects all of this regardless of where your project is located.
The International Energy Agency estimates that passive solar design strategies — orientation, shading, and thermal mass — can reduce heating and cooling loads by 25–50% before any mechanical system is even specified. SketchUp lets you test these strategies in minutes at concept stage.
Setting Geo-Location and the Solar North Tool Correctly
Every SketchUp solar analysis lives or dies on geo-location accuracy. A model placed at the wrong latitude can be off by 20° on sun altitude — the difference between a shading device that works and one that doesn't. This section walks through the complete setup, including the Solar North tool that most users ignore.
Pinning Your Project to the Earth
In SketchUp, navigate to File → Geo-location → Add Location. You'll see a satellite map interface. Search for your site by address or coordinates and drag the capture area over the site boundary. When you confirm, SketchUp does two things: it imports a terrain mesh (useful for topographic shadow studies) and stores the latitude, longitude, and UTC offset in the model file. From this point forward, every shadow cast by the sun engine is geographically accurate. For urban sites or complex terrain, zoom in as far as the satellite imagery allows before confirming — the capture point sets the model's true geographic anchor.
The Solar North Tool: Why It Exists
SketchUp's default assumption is that the model's green axis (Y-axis) points to geographic north. This works fine if you draw your building with true north as the reference. But in practice, most projects arrive as DWG site plans rotated to fit a page, or with roads running at angles to the compass. The Solar North tool (found under View → Toolbars → Solar North, or via the Extensions menu) lets you define the true north direction independently of the model's axis. Set it by entering a bearing in degrees or by clicking two points on a known north reference line on your site plan. Without this step, your shadow study is essentially fiction.
Skipping the Solar North tool when working with a rotated site plan. If your building footprint is drawn 23° off true north — which is common in grid cities like Manhattan, Melbourne's CBD, or central Amsterdam — every shadow study will be 23° wrong. This error is invisible in SketchUp's viewport but will dramatically misrepresent which façades receive morning versus afternoon sun.
Time Zone and Daylight Saving
SketchUp stores your UTC offset at the time of geo-location. If your site observes daylight saving time, check that the Shadow Settings panel (Window → Shadows) is using the correct offset for the season you're analysing. A simple verification: set the date to June 21 and the time to solar noon (12:00 UTC+local offset). The shadow should fall directly to the north (southern hemisphere: south). If it's slightly offset, adjust the UTC offset by ±1 hour. This two-minute check prevents a surprisingly common calibration error.
Checking Your Setup: A 90-Second Verification
After setting geo-location and Solar North, open the Shadow Settings panel and set the date to the December solstice and the time to 09:00 local time. Look at which façade receives direct sun. If your building is oriented with its long axis east-west (the recommended passive solar orientation in temperate climates), the south-facing wall (north-facing in Australia or Chile) should be fully sunlit. If a north-facing wall is sunlit on the December solstice morning in, say, London or Chicago, your Solar North setting needs revision.
Running Solstice Shadow Simulations in SketchUp
The two most important dates in any SketchUp shadow study are the solstices. June 21 gives you the sun at its highest annual arc (in the northern hemisphere); December 21 shows it at its lowest. If your design performs well on both extremes, it will perform well on every day in between. This section explains how to run, animate, and interpret solstice shadow simulations in SketchUp.
The Three Critical Shadow Dates
Practising architects typically examine three dates: the summer solstice (June 21 in the northern hemisphere, December 21 in the southern), the winter solstice (December 21 / June 21), and the equinoxes (March 21 and September 21 share the same solar path). The equinox date is particularly useful because it represents the mid-season condition — the point at which neither summer shading nor winter solar gain is extreme. For a residential project in a temperate climate like northwest Europe or the US Pacific Northwest, equinox performance often dictates whether a south-facing window feels comfortable or overheated in shoulder seasons.
Animating the Shadow Study
In the Shadow Settings panel, set your target date, then use the time slider to sweep from sunrise to sunset. Watch the shadow patterns across your model carefully. Note which spaces lose direct sun first (these may need supplementary lighting or thermal mass to buffer temperature swings), and which receive sun for more than six hours (these may need shading devices). For a more systematic review, use SketchUp's built-in animation export: set keyframes at 09:00, 12:00, 15:00, and 17:00 for both solstice dates and render a GIF or MP4 — this becomes a powerful client communication tool and a permanent project record.
A minimum of 4 hours of direct winter sun on south-facing glazing (north-facing in the southern hemisphere) is the general threshold used in German Passivhaus calculations and Australian BASIX assessments for solar gain adequacy. Run your December solstice shadow study first — if the main glazed façade doesn't meet this, the orientation or form needs to change before any other decision is made.
Neighbouring Building Shadows and Urban Overshadowing
In dense urban contexts — central Singapore, inner London, midtown Manhattan, or central Tokyo — neighbouring buildings often impose more shadow than the sun's seasonal arc. Model surrounding buildings to their approximate heights (even as simple extruded footprints) before running shadow studies. In the UK, the Building Research Establishment (BRE) recommends the "25° rule of thumb" for daylight assessment: a window is likely to be adequately daylit if no obstruction subtends an angle greater than 25° above horizontal from the centre of the window. You can check this directly in SketchUp by drawing a reference line at 25° from the sill of any critical glazing unit.
Saving Shadow Scenes as Design References
Use SketchUp's Scenes panel to save named views at each key shadow condition: "Dec Solstice 9am", "Dec Solstice 12pm", "Jun Solstice 9am" and so on. These scenes persist through model changes and allow rapid before-and-after comparison when you modify the massing. They also serve as the starting point for presentation layouts in LayOut.
Massing for Passive Solar: Orientation Rules by Climate
Passive solar massing in SketchUp is not just about rotating a box. It is about understanding that different climate types demand fundamentally different building forms, and that SketchUp's shadow engine lets you test those forms rapidly at zero cost. This section covers the orientation rules that should inform your first massing decisions across four major climate types.
The Universal Orientation Principle and Its Exceptions
The most widely cited passive solar rule is to orient the main glazed façade within 15–20° of true south (or true north in the southern hemisphere). This maximises winter sun exposure and minimises summer overheating on the primary façade. In practice, this holds well for temperate climates (Western Europe, the US Mid-Atlantic, Japan's Pacific coast, southern Australia). However, in hot-arid climates like the Middle East, North Africa, or the Indian subcontinent, minimising all solar gain on opaque walls is equally important — here, a compact inward-looking form with a shaded courtyard often outperforms a south-facing linear plan. In hot-humid tropical climates (Malaysia, coastal West Africa, coastal Queensland), the priority shifts again toward cross-ventilation, and elongating the plan on the east-west axis to catch prevailing breezes becomes as important as sun angle.
Building Form and the Compact Ratio
Passive solar performance is closely linked to the surface-area-to-volume ratio (SA/V). A compact form loses less heat in cold climates (lower SA/V) but gains more heat in hot climates. As a rule of thumb, buildings in climates below 0°C in winter should aim for an SA/V below 0.7 m²/m³ — roughly a cube or a short rectangular bar. In hot-arid climates, compact forms with inward-facing courtyards (effectively the traditional riad in Morocco or the haveli in Rajasthan) achieve low SA/V while directing solar exposure inward to a controlled space. SketchUp can calculate SA/V directly via the Entity Info panel: model your massing, select all faces, and the total surface area is displayed alongside volume.
To calculate SA/V in SketchUp: create your massing as a solid group, right-click → Entity Info. SketchUp displays Volume. For surface area, triple-click inside the group to select all faces, then read the area total in Entity Info. Divide area by volume — if the number is above 1.0 m²/m³ for a building in a cold climate, the form is thermally inefficient and worth reconsidering.
Testing Orientation Options in SketchUp
The fastest SketchUp workflow for testing orientation is to create a simple box massing, group it, and use Rotate (shortcut Q) to test 10°, 20°, and 30° rotations from true south while your shadow study is running live. Watch how the shadow changes in real time as you rotate the form. This direct visual feedback — which takes about two minutes per option — often resolves orientation debates that might otherwise occupy an entire design team meeting. Save each rotation as a separate Scene for comparison.
Calculating Overhang Depth by Latitude in SketchUp
The fixed horizontal overhang is the most versatile passive solar shading device ever devised: correctly sized, it admits low winter sun while blocking high summer sun with zero moving parts and zero energy input. But "correctly sized" is entirely latitude-dependent. Overhang depth calculation is one of the most practical things you can do in SketchUp, and this section gives you the formula and the modelling workflow.
The Solar Altitude Angle — Your Key Variable
The altitude of the sun at solar noon on the summer solstice (the highest it gets all year) determines how much overhang you need to fully shade a vertical window. This angle is calculated as: Summer noon altitude = 90° − latitude + 23.5°. For London (51.5°N): 90 − 51.5 + 23.5 = 62°. For Sydney (33.9°S): 90 − 33.9 + 23.5 = 79.6°. For Dubai (25.2°N): 90 − 25.2 + 23.5 = 88.3°. The higher the summer sun altitude, the shorter the overhang needed to shade a window — because the sun is nearly overhead, even a shallow overhang creates a steep shadow angle. Conversely, in higher latitudes, the summer sun is lower in the sky, and overhangs must project further to intercept it.
The Overhang Projection Formula
The required horizontal overhang projection (P) for a window of height (H), measured from the top of the window to the bottom of the overhang, is given by: P = H / tan(summer noon altitude). Example: A window 1.8m tall at 51.5°N (London): P = 1.8 / tan(62°) = 1.8 / 1.88 ≈ 0.96m. The same window at 33.9°S (Sydney): P = 1.8 / tan(79.6°) = 1.8 / 5.67 ≈ 0.32m. This is why Sydney houses have modest eaves by European standards — the subtropical sun is so high in summer that even a 300–400mm overhang does significant work.
The same overhang that completely shades a window in summer must also allow winter sun in. Check winter performance by running your December solstice shadow at solar noon: if the overhang casts a shadow on the upper portion of the glazing, shorten it or add a louvred rather than solid overhang to maintain winter solar access while preserving summer shading.
Modelling Overhangs Accurately in SketchUp
The most efficient SketchUp workflow is to model your window as a rectangle with a line at the sill and a line at the head. Extrude your overhang from the head line by the calculated projection depth. Then run your shadow study at the summer solstice solar noon and check that the shadow line falls at or below the sill. If the shadow falls above the sill, extend the projection. If the shadow falls well below the sill (indicating an over-sized overhang), trim it back and verify the winter solstice condition. This iterative modelling process takes about five minutes per window type once your solar settings are configured.
Regional Overhang Norms and Vernacular Solutions
Different architectural traditions have arrived at latitude-appropriate shading solutions through centuries of trial and error. The deep loggia of Italian Renaissance architecture (typically 1.5–2m projection at 43°N) provides shade at exactly the summer noon altitude for central Italy. The broad eaves of Queensland vernacular architecture (600–900mm) work for the 27–28°S latitude of Brisbane. Mashrabiya screens in the Gulf States block diffuse sky radiation from multiple angles simultaneously — a more sophisticated solution for latitudes where even a correctly sized overhang can't prevent glare from a sun that is 85–88° high in summer. SketchUp can model all of these — the principle is always the same.
Sefaira Lite for SketchUp — Getting Real Energy Feedback
Sefaira Lite for SketchUp is a free plugin that adds a layer of quantified energy and daylight feedback directly inside SketchUp, bridging the gap between geometric shadow studies and full dynamic energy modelling. This section explains what Sefaira Lite does, how to get meaningful results from it, and where its limits lie.
What Sefaira Lite Actually Calculates
Sefaira Lite performs simplified whole-building energy simulation using EnergyPlus as its calculation engine in the background. The plugin analyses your SketchUp massing alongside user-specified inputs — floor-to-floor height, glazing ratio, construction type, HVAC system type, and occupancy schedule — to estimate annual heating and cooling loads, peak demand, and useful daylight illuminance. Results are returned as simple bar charts and summary metrics directly in the SketchUp viewport. It is not a substitute for a full energy model, but for concept-stage design decisions, its estimates are typically within ±15–20% of a detailed simulation — accurate enough to compare options A, B, and C.
Installing and Configuring Sefaira Lite
Sefaira Lite is available free from the SketchUp Extension Warehouse. Search "Sefaira" and install via the Extension Manager. The plugin requires a free Sefaira account for the cloud-based calculations. After installation, the Sefaira toolbar appears in SketchUp. To begin analysis, you must tag your SketchUp geometry with space types: select floor faces and assign them as "spaces" using the Sefaira Space tool, assign boundary conditions (interior vs exterior walls), and specify your location's climate file. The climate file library covers over 2,100 locations worldwide using EPW (EnergyPlus Weather) data.
Running Sefaira on a model where the geometry is not watertight. Sefaira's space-detection algorithm requires fully enclosed volumes — any gap in the floor, ceiling, or wall geometry will produce missing or zero energy results. Use SketchUp's Solid Inspector extension to verify model integrity before running Sefaira. This is the most common reason for unexpected null results.
Reading Sefaira's Energy Output Intelligently
Sefaira Lite returns three primary metrics: annual energy use intensity (EUI) in kWh/m²/year, peak heating demand (W/m²), and useful daylight illuminance (UDI) as a percentage of floor area. EUI is the most useful comparative metric at concept stage. A well-designed office building in a temperate climate typically achieves an EUI of 80–120 kWh/m²/year; net zero performance typically requires 50 kWh/m²/year or below, depending on the energy source mix. A simple residential detached house in a cold climate might start at 150+ kWh/m²/year before passive solar optimisation and come down to 80–90 kWh/m²/year after orientation, glazing, and overhang adjustments — all changes testable in SketchUp before any detailed design work begins.
Using Sefaira to Test Passive Solar Strategies
The most powerful use of Sefaira Lite is rapid option comparison. Model three massing variants — for instance, a square plan, a rectangular east-west plan with 40% south glazing, and the same with optimised overhangs — run Sefaira on all three, and compare EUI figures. Typical findings: rotating a square plan to the optimal orientation can reduce cooling load by 8–12%; adding correctly sized overhangs can add a further 10–15% reduction; increasing south glazing from 20% to 40% in a cold climate can reduce heating load by 15–20% while increasing cooling load by only 4–6%. These are directional estimates, but they are directional in the right direction, and they cost nothing to test.
Reading Shadow Results and Translating Them Into Design Decisions
Running a SketchUp shadow study is straightforward. Knowing what to do with the results — how to translate a shadow pattern on a screen into a window size, a glazing specification, or a massing revision — is where expertise matters. This section covers how to read and act on what SketchUp shows you.
What Good Looks Like: Benchmarks for Residential and Commercial
For a passive solar residence in a temperate climate, the target is direct winter sun penetrating to at least 50% of the depth of the main living space for a minimum of 4 hours on the winter solstice. This is the threshold used in various European passive solar design guidelines, including German solar architecture standards and the UK's Code for Sustainable Homes solar design criteria. Measure it in SketchUp by drawing a reference plane at 50% of room depth and checking whether the shadow line falls forward of or behind this plane at 12:00 on December 21. If the shadow retreats past the 50% line, the glazing is undersized, the room is too deep, or the building is in the shadow of a neighbour.
Identifying Overheating Risk in Summer Shadow Studies
For summer, the key concern is unshaded east- and west-facing glazing, which catches low-angle morning and afternoon sun that no fixed horizontal overhang can block economically. In your June solstice study at 08:00 and 16:00, check whether east- and west-facing windows receive direct sun for more than two hours. If they do, these windows are overheating risks in warm and Mediterranean climates. Solutions — vertical fins, deep window reveals, external roller shutters, deciduous planting — all need to be modelled in SketchUp to verify their effectiveness. A common finding is that a 600mm vertical fin on the west side of a window reduces summer afternoon direct sun exposure by 60–80% while barely affecting winter solar access.
Add a SketchUp section cut at mid-room height on your winter solstice study to see exactly how deep winter sun penetrates into habitable space. Essential for Passivhaus compliance checks.
Save a shadow scene before any design change, make your revision, then save a new scene. Use SketchUp's two-window layout to compare both simultaneously.
Three time stamps on each solstice date gives a complete picture. Export these six images directly from SketchUp to a presentation folder as your design record.
Terraces, gardens, and courtyards need solar access checks. A south-facing terrace in shadow from the building above it for the whole winter solstice is a design failure — check it early.
Using Shadow Studies to Negotiate With Planning Authorities
In many jurisdictions, shadow impact on neighbouring properties is a planning consideration. Local planning authorities in the UK, Australia, and the Netherlands, for example, require shadow impact assessments for buildings above a certain height or when they are within a specified distance of neighbouring dwellings. SketchUp shadow studies, exported as annotated PDFs via LayOut, are accepted as supporting documentation in many preliminary planning submissions. While they are not a substitute for a formal daylight and sunlight report (which typically uses specialist software conforming to national standards), a SketchUp shadow study often flags problems early enough to avoid them — and that is exactly what it is for.
Thermal Mass, Glazing Ratios, and Early-Stage Rules of Thumb
Solar geometry tells you when and where the sun shines. Building physics tells you what to do with that sun once it enters the building. The three key variables at concept stage are glazing ratio, thermal mass, and the relationship between them. These decisions belong in SketchUp alongside your shadow studies — not later, in a specialist energy model.
Window-to-Wall Ratio: The Numbers That Matter
Window-to-wall ratio (WWR) is the percentage of a façade's gross area occupied by glazing. Most building energy codes set maximum WWRs to control heat loss and solar gain. The range globally is significant: the US International Energy Conservation Code (IECC) 2021 caps WWR at 40% for commercial buildings in most climate zones; the UK's Building Regulations Part L (dwellings) uses a notional building approach that implies roughly 25% WWR for typical houses; the Australian NCC Section J limits window areas based on climate zone and orientation. For passive solar performance, the sweet spot for south-facing glazing (northern hemisphere temperate) is typically 30–50% of the south wall area — enough to capture meaningful solar gain without creating unacceptable heat loss at night.
Increasing south-facing WWR from 20% to 40% in a UK climate typically reduces annual heating demand by 12–18 kWh/m²/year while increasing summer cooling demand by only 3–5 kWh/m²/year — a strongly net positive trade-off when paired with correct overhangs and adequate thermal mass. This is the kind of ratio that Sefaira Lite can confirm or refine at concept stage.
Thermal Mass: How Much and Where
Thermal mass absorbs solar energy during the day and releases it at night, smoothing temperature swings and reducing peak heating demand. The Australian Government's Your Home guidelines recommend a minimum of 0.3 m² of exposed high-density thermal mass (concrete, masonry, or tile over concrete) per m² of net floor area for passive solar effectiveness. Passivhaus standards in Europe are less prescriptive about mass but specify airtightness and insulation so stringent that mass plays a secondary role. In hot-arid climates like the Arabian Peninsula or Rajasthan, heavy mass walls (400–600mm fired brick or rammed earth) moderate the extreme diurnal temperature range — sometimes 20–30°C between day and night — making mass a primary cooling strategy rather than a solar gain strategy.
Modelling Thermal Mass Proxies in SketchUp
SketchUp cannot directly simulate thermal mass performance — that requires dynamic thermal modelling. However, you can use it to check that your floor plan layout allocates thermal mass to the correct zones. For passive solar, mass should be placed where direct winter sun falls: a dark-coloured concrete floor under south-facing windows is the classic arrangement. In your winter solstice shadow study at noon, overlay a floor plan and mark the zones receiving direct sun. If your plan shows carpet over timber subfloor in the sunlit zone, that is a design decision worth flagging long before the interior finishes are specified.
The Glazing-Mass Balance
Every additional square metre of south-facing glass needs to be balanced by approximately 3–6 m² of exposed high-mass floor or wall surface to prevent daytime overheating and ensure effective night-time heat release. This ratio, derived from California's original Passive Solar Design Strategies (PSDS) published by the National Renewable Energy Laboratory and widely referenced internationally, remains a useful concept-stage check. If your Sefaira study shows high peak heating but acceptable annual EUI, insufficient thermal mass is often the culprit. If it shows high cooling load despite correct overhangs, excessive glazing relative to available mass is a common cause.
When to Move from SketchUp to Autodesk Forma for Climate Analysis
There is a point in every project where SketchUp solar modelling has given you everything it can, and the questions that remain require dedicated climate analysis software. Recognising that point — neither too early (wasting money on detailed simulation before the design is stable) nor too late (locking in decisions that a proper model would have revised) — is a professional skill worth developing. This section defines that threshold clearly.
What SketchUp Cannot Do
SketchUp's shadow engine is geometric, not thermal. It does not model heat transfer through walls, air infiltration, internal heat gains from occupants and equipment, or the interaction between the envelope and mechanical systems. It cannot produce a dynamic thermal profile showing hour-by-hour indoor temperatures, which is required for overheating risk assessments in many jurisdictions. In England and Wales, the UK Government's approved method for overheating assessment in new dwellings (as described in TM59, CIBSE's methodology) requires dynamic thermal simulation — a SketchUp shadow study, however thorough, will not satisfy this requirement. Similarly, ASHRAE 90.1 compliance in the US, NABERS ratings in Australia, and GRIHA ratings in India all require validated dynamic energy simulation, not geometric solar analysis.
What Autodesk Forma Adds
Autodesk Forma (formerly Spacemaker, acquired by Autodesk in 2021) is an AI-assisted urban design and early-stage climate analysis platform. Its key capabilities beyond SketchUp include: wind flow simulation using CFD-lite algorithms, solar irradiance mapping (not just shadow geometry, but actual kWh/m²/year falling on each surface), outdoor thermal comfort analysis using PET (physiological equivalent temperature), and noise analysis for urban sites. For a large residential or commercial development, Forma's solar irradiance mapping alone can identify which roofs are viable for photovoltaic installation, which façades have overheating risk, and which outdoor spaces are usable in summer — information that requires a significant step up in analysis rigour.
Move from SketchUp to a dedicated climate analysis tool (Forma, IDA ICE, DesignBuilder, or equivalent) when: (1) the project is above three storeys or 1,000m² GFA; (2) a planning submission requires a formal energy or daylight report; (3) you are targeting a formal certification (Passivhaus, LEED, BREEAM, Green Star, GRIHA); or (4) the Sefaira Lite results show a marginal outcome (EUI within 10% of the compliance threshold) that needs higher-confidence verification.
The Transition Workflow
Autodesk Forma accepts SketchUp models via direct import (SKP format) or via IFC export. The cleanest transition is to prepare a clean solid massing model in SketchUp — groups and components correctly named, no reversed faces, all volumes watertight — and import it into Forma as a starting point. Your SketchUp geo-location and Solar North settings carry over through IFC export, preserving the orientation work you have already done. Forma then layers climate data from its built-in EPW library onto your geometry and performs its more sophisticated analyses. Think of SketchUp as the pencil sketch that Forma then traces in ink.
Free Alternatives to Forma for Early Climate Analysis
If Autodesk Forma's cost is prohibitive (it is a subscription product, typically bundled with AEC Collection or licensed separately), consider these free or low-cost alternatives: Ladybug Tools for Rhino/Grasshopper (the most powerful free parametric climate analysis suite available), OpenStudio with SketchUp plugin (direct EnergyPlus integration, free, requires some technical setup), and NOAA's Sun Angle Calculator for quick latitude-specific sun angle lookups without any modelling at all. Each serves a different user profile, but all are viable paths beyond SketchUp's built-in capabilities.
A Repeatable Net Zero Workflow in SketchUp — Start to First Insight in 20 Minutes
Everything covered in the previous nine sections resolves into a single, repeatable workflow that any architect or technically literate designer can complete in under 20 minutes on any new project. This is the SketchUp net zero concept modelling process — from blank model to first actionable solar insight.
Phase 1: Foundation (Minutes 0–5)
Open a new SketchUp file. Set units to metres. Navigate to File → Geo-location → Add Location and pin your site. Once terrain is imported, open the Shadow Settings panel and activate the Solar North tool. If your site plan is available as a DWG, import it as a reference layer and align it to the model's axis using Solar North. Verify setup by checking the December 21 noon shadow direction. Push-pull a simple box massing to the approximate building height. Tag it "Massing v1." This phase is entirely preparatory — its only output is a geographically and astronomically calibrated model ready for analysis.
Phase 2: Shadow Analysis (Minutes 5–12)
Run the following shadow studies in sequence, saving each as a named Scene: (a) December 21 at 09:00, 12:00, and 15:00 local time; (b) June 21 at 09:00, 12:00, and 15:00 local time; (c) March 21 at 12:00 (equinox reference). At each scene, make a note of: which façades receive direct sun and for how long, whether shadow falls on adjacent properties (important for planning), and whether the main glazed façade receives adequate winter sun. This phase takes about seven minutes once the setup is complete, and it produces six reference screenshots that will be used for the rest of the project.
Name your scenes with a standard convention from day one: "SH_Dec21_0900", "SH_Dec21_1200" and so on. This makes the scene list sortable and legible to anyone else opening the file. On collaborative projects, this small discipline saves significant time when briefing a consultant taking over the solar analysis.
Phase 3: Passive Solar Optimisation (Minutes 12–18)
Based on your shadow study results, make the following rapid tests: (1) Rotate the massing in 10° increments to find the optimal orientation for winter solar access. (2) Model candidate overhangs using the latitude formula from Section 05 and verify them against the summer solstice study. (3) Check SA/V ratio via Entity Info. (4) If Sefaira Lite is installed, run a quick EUI estimate on your preferred massing option. Document the EUI baseline. These four steps define your passive solar concept direction in concrete, quantified terms — not vague principles but actual numbers that will anchor every subsequent energy decision on the project.
Phase 4: Documentation and Next Steps (Minutes 18–20)
Export your six shadow study scenes as images from File → Export → 2D Graphic. Note the EUI baseline from Sefaira Lite if used. Write a brief concept note (one paragraph) stating: site latitude, optimal orientation, overhang projection for main glazing, SA/V ratio, and EUI baseline. This note, alongside the six shadow images, constitutes your passive solar concept report — a document that costs nothing to produce, takes 20 minutes, and ensures that every subsequent design decision is made with clear solar awareness rather than intuition alone.
Pin the site, verify Solar North, check December noon shadow direction. All analysis depends on this step being right.
3 times × 2 solstice dates. Save as named scenes. This is your baseline — screenshot everything before changing anything.
Try ±20° orientations, model overhangs using your latitude formula, verify summer shade and winter access.
Get your EUI baseline. Export 6 images. Write a one-paragraph passive solar concept note. This is your solar record for the project file.
Download the Free SketchUp Passive Solar Template
Pre-configured geo-location, named shadow scenes for 6 key solar dates, Solar North setup guide, and Sefaira Lite configuration notes. Link in footer. No email required.
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