Morning light that’s kind on foliage, or warm afternoon beams that push color but flirt with heat? In small apartments, east vs west isn’t a vibe—it’s a PPFD choice at the leaf. Most guides talk direction; this piece shares measurable, real-world bands and what they mean for your shelves and sills. (Why now?) Because collectors need numbers, not guesswork, to avoid scorch or stretch.
“I used to call my room ‘bright’—until a meter showed my west shelf spiking at noon.”
“Switching to sheer + distance gave me compact leaves without crispy tips.”
In typical US/UK apartments, east windows often read ~60–120 PPFD at 30–60 cm from glass late morning; west windows can match intensity (~70–130 PPFD) but run warmer. Start foliage aroids 60–90 PPFD for 10–12 h, then adjust by ±10 PPFD every 2 weeks based on leaf edges and temperature (keep leaf ≤ 28 °C / 82 °F).
Background & Definitions
PPFD = photosynthetic photon flux density at the leaf surface (µmol·m⁻²·s⁻¹). DLI = daily light integral (mol·m⁻²·day⁻¹) = PPFD × hours × 0.0036. Indoors, distance and diffusion strongly shape leaf-level intensity; PPFD drops as you move away from the source.
Direction reality: East offers cooler morning sun; west can feel hotter in the afternoon, especially in summer. Both can deliver “bright, indirect” with sheer + setback, but west needs more heat awareness.
Settings & Scenarios — Real Apartment Presets
East Window — Gentle Morning Build
At 30–60 cm (12–24 in) behind a sheer, many apartments see ~60–120 PPFD late morning with modest leaf heating. For foliage aroids (philodendron, anthurium foliage types), this is a forgiving baseline; extend photoperiod to 12 h in winter rather than chasing high peaks.
West Window — Similar PPFD, Higher Heat Risk
Mid–late afternoon, west can hit ~70–130 PPFD at 30–60 cm with higher leaf temperature. Use sheer + 50–100 cm setback or slide plants off-axis from the beam. Prioritise spread and cooling (airflow) over raw intensity.
Real Readings Table (Indicative, Apartment Shelves)
(Confirm with your meter; numbers vary by season, latitude, glazing, and room depth.)
| Window | Distance from glass | Midday PPFD | Leaf temp tendency | Notes |
|---|---|---|---|---|
| East | 10 cm (4 in) | 120–160 | low–moderate | Use sheer if over 120 on velvet leaves |
| East | 50 cm (20 in) | 70–110 | low | Sweet spot for foliage aroids |
| East | 1 m (39 in) | 40–70 | low | Extend hours to reach DLI |
| West | 10 cm (4 in) | 130–180 | higher | Diffuse or step back to manage heat |
| West | 50 cm (20 in) | 80–120 | moderate | Watch afternoon spikes in summer |
| West | 1 m (39 in) | 45–80 | moderate | Add airflow; avoid direct beam |
(UMN explains PPFD basics and the effect of distance/diffusion on intensity.)
How to Measure & Adjust
- Measure: Use a PPFD meter (or a cautious lux→PPFD estimate). Sample center and edges at leaf height.
- Decide: Start aroids at 60–90 PPFD for 10–12 h.
- Nudge: If newest leaf is smaller/paler → +10 PPFD and re-check in 2 weeks.
- Protect: Edge crisping or bronze sheen → –10 PPFD or increase distance +5–10 cm, keep leaf ≤ 28 °C / 82 °F.
- Seasonal tweak: In winter, favour longer hours over chasing high peaks.
(General direction & seasonal rationale from RHS guidance on fluctuating light and filtering strong sun.)
Two Practical Rules
Afternoon Heat Penalty (West): If leaf temp rises > 2 °C above room during the peak hour, treat PPFD as +10 for stress risk. Buffer with sheer + setback or airflow.
Window-Depth Loss (Both): Expect roughly –30–50 PPFD going from 50 cm → 1 m behind sheer in many flats; offset with longer hours rather than raw intensity.
Third-party experiences
Common pattern: Even when PPFD is similar, west setups scorch more often—heat + angle are the culprits.
Frequent pitfall: Calling a west sill “indirect” in summer; leaf edges crisp within a week.
What works for many growers: Sheer + 50–100 cm setback on west; east stays closer with fewer issues.
Anonymised statement (paraphrased): “Moving 60 cm back from a west pane stopped crispy margins while growth stayed compact.”
Anonymised statement (paraphrased): “East-with-sheer matched my cabinet’s 70–80 PPFD without heat spikes.”
Transparency: Experiences above were compiled from public forums/Reddit/public FB groups; these are not this site’s own hands-on trials.
Science in one line: PPFD at the leaf depends on intensity and geometry (distance/angle); afternoon beams add thermal load, so diffusion + setback moderates stress. See UMN Extension’s lighting primer for PPFD fundamentals.
FAQs
Is east always safer than west for foliage aroids?
Usually yes—cooler mornings mean less heat stress at similar PPFD. You can still use west with sheer + distance and airflow.
What PPFD should I aim for by a window?
For foliage aroids, ~60–90 PPFD for 10–12 h is a strong baseline; increase in +10 steps based on healthy new growth.
Do I need grow lights if I have a bright west window?
Maybe in winter or deep rooms; you’ll hit intensity but not an even spread. See our Aroid Light & PPFD Hub for window + bar combos.
On my east shelf, I keep foliage aroids ~40 cm behind a sheer for ~70–80 PPFD at midday. On my west shelf, I set sheer + 80 cm setback, a tiny fan across the canopy, and only then try +10 PPFD nudges.
“PPFD is what reaches the leaf surface, and it drops with distance from the light.” — University of Minnesota Extension (lighting primer).
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