Chimney House: Designing with Nature
- Cindel Soo
- 4 days ago
- 8 min read
“We wanted more than just a house — we wanted a sanctuary for our aging parents. A space where they could rest and recover in comfort, without relying on air-conditioning or shutting out the world.”
The design of this house took inspiration from Spanish-style homes, which are traditionally well-suited for hot climates. Inspired by Spanish-style homes known for their thick walls, shaded courtyards, and natural ventilation, we adapted these passive cooling principles for a modern tropical setting.
THE CHALLENGE – BUILDING WITH CONSTRAINTS
Designing for comfort may sound simple — until you face real-world limitations: A tight site, minimal setbacks, and moments of miscommunication during design and coordination with consultants and contractors. These constraints tested not just our ideas, but also our flexibility and problem-solving throughout the process.
THE DESIGN STRATEGY – DESIGNING FOR REAL COMFORT IN THE TROPICS
“In tropical climates, comfort doesn't just come from air-conditioning — it comes from working with the sun, the wind, and the materials. Our goal was to make the house breathe on its own, quietly and efficiently.”
This philosophy mirrors that of Spanish-style architecture, which often uses courtyards, high thermal mass materials, and cross-ventilation to passively cool homes — strategies we adapted and reinterpreted for a modern tropical setting.
We adopted passive design strategies integrated with user-friendly technologies, all shaped by the parents’ routines, comfort, and safety.
1) Chimney Ventilation Fans – Thoughtfully Selected and Timed
i. Early concept (solar fan + daytime use)
At the early design stage, we considered using solar-powered chimney ventilation fans to enhance airflow during the day while saving energy. The idea was to extract warm air passively as the sun heated the home.
ii. Simulation results (night use is better)
However, simulation results revealed that daytime extraction was counterproductive. Running the fans during the day drew in hot outdoor air and undermined the thermal mass benefits of the concrete roof slab, which naturally cools to ~25°C overnight.
iii. Final schedule + effect
Instead, we reversed the strategy:
→ Fans remain off during the day to prevent heat gain and preserve the slab’s stored coolness.
→ Fans operate at night and early morning, extracting warm indoor air through the attic while inviting cooler night air inside.
This mode allows the structure to store “coolth” overnight and retain it into the following day — a passive way to delay indoor heat buildup.
2) Smart Window Use – A Daily Cooling Rhythm
The home was designed for a simple ventilation cycle: open windows at night, close them during the day.
i. During the day, sealed windows and ceiling fans help circulate cooler indoor air.
ii. At night, opening windows allows the structure to release heat and take in fresh air — reducing reliance on mechanical cooling.
3) Suspended Ceiling with Air Pathways
We introduced a suspended ceiling with at least 30% perforation to enable warm air extraction through the attic, enhancing the chimney effect. More importantly, it allows the roof slab to radiate stored coolness back into living spaces below.
4) Material Selection – Flooring that Works with Thermal Mass
We were deliberate about material choices, particularly for interior finishes. In warm, humid climates, thermal mass plays a critical role in regulating indoor temperatures — especially when paired with night cooling.
Therefore, thermally responsive flooring materials like tiles and marble, which absorb coolness during the night and slowly release it throughout the day were preferred. These materials complement the concrete structure and help keep floor-level temperatures comfortable, especially in the morning and early afternoon. While wood feels warmer underfoot, it insulates rather than conducts heat — the opposite of what you want in passive thermal design.
5) Roof Insulation – A Shield Against the Sun
A well-insulated roof with a layer of Onduline roof sheet sandwiched between 2 layers of radiant barriers, bubble foil (top) + aluminium foil (bottom) acts like a thermal barrier, keeping out intense solar heat and helping indoor spaces stay cooler during peak daytime hours.
6) Acoustic Wall Openings – Quiet Crossflow
Discreet wall openings above bedroom doors allow air from the corridor (where chimney fans operate) to flow into bedrooms — without allowing unwanted noise. This supports quiet, continuous air circulation above the ceiling plane.
Watch two videos of the acoustic transfer grill system:
Video showing the installation: https://www.youtube.com/watch?v=4c2bBpHq2xY
Video testing the sound proofing: https://youtube.com/shorts/G5KlueJjAY8?si=2aUoVTtNIeM3C4SZ
7) Secure Window Grilles + Integrated Mosquito Nets – Breezy, Safe Nights
To enable natural night ventilation without compromising safety or comfort, we installed security grilles with integrated mosquito nets on all operable bedroom windows. This detail was essential for older residents who are more sensitive to both heat and insect disturbances.
i. The grilles provide security, making it possible to leave windows open overnight.
ii. The mosquito nets protect against insects, ensuring that ventilation does not come at the cost of sleep quality or health concerns.
8) Landscape Shading – Cooling from the Outside
To provide greenery and trees along east- and west-facing facades to:
i. Shade walls and windows from direct sunlight
ii. Reduce heat gain and glare
iii. Cool the surrounding microclimate
9) High-Performance Glazing – Light Without Heat
Low-E glass with a shading coefficient below 0.45 keeps out unwanted solar heat while admitting natural daylight — reducing the need for cooling and lighting.
Each of the above nine house design elements works not in isolation, but as part of a holistic system that quietly adjusts with the time of day, the weather, and the users' habits.
THE RESULTS – SIMULATION VS. REALITY
“Designing a home is one thing. Seeing how it actually performs — especially when certain ideas aren’t fully realized — is where the real learning begins.”
Pre-Design Baseline (Yellow squares): Indoor temp before any passive strategies.
Planned Design (Simulated) (Green diamonds): Indoor temp based on simulation of full implementation of passive measures.
Reality On-Site (Blue triangles): Actual measured indoor temp post-occupancy.
Outdoor Ambient Temperature (Black dashed line): Environmental reference for comparison.
BASELINE Design
Nighttime (6 PM – 8 AM):
Minimal cooling during the night.
Indoor temperatures remain high (~30.5°C), indicating the structure retains daytime heat.
Daytime (8 AM – 6 PM):
Rapid heat gains due to solar exposure and lack of insulation or ventilation.
Indoor temperatures peak around 35.5°C by mid-afternoon (~2–3 PM).
Result: A hot, stagnant interior with high reliance on mechanical cooling.
PROPOSED Design
Nighttime (8 PM – 8 AM):
Indoor temperatures maintained ~1.5–2.5°C above outdoor levels.
Night flushing + thermal mass allows the house to release stored heat and recharge with cool air.
Daytime (8 AM – 8 PM):
The interior remains consistently cooler than outdoor temperatures, peaking at ~29°C vs. 32°C outside.
Results from synergy of insulation, shading, chimney ventilation, thermal mass (tile/marble floors), and smart window usage.
Peak Benefit:
Indoor peak temperature ~6.5°C lower than the pre-design baseline.
Combined with ceiling fans, it eliminates the need for air-conditioning — even on hot days.
ACTUAL Design
Key Deviations from Design Intent:
a. Windows and doors remained closed, day and night — due to security concerns, personal habits, and alarm system limitations.
b. Ceiling fans were used, but with all windows closed a night, the fans did not help to increase the air change rate with the outdoors.
c. Chimney ventilation fans underperformed — actual measured airflow was 10 times lower than the fan specification, hence, severely lessening the nighttime cooling.
d. Wooden flooring used in bedrooms, which offered minimal thermal mass, reducing the ability to absorb and store the nighttime coolness.
Collectively, the above deviation from the original design intent reduced the overall effectiveness of the passive cooling strategy — especially during the night, when natural ventilation and thermal mass are meant to work together to reset indoor temperatures.
MEASURED Performance
Nighttime (9 PM – 9 AM):
Indoor temperature remained ~2°C higher than outdoors from 12 AM to 7 AM. This indicates ineffective night flushing, primarily due to windows staying closed, underperforming chimney fans, and the use of wooden flooring, which offers low thermal mass.
Peak overnight comfort potential was not achieved due to the building staying sealed when ventilation was needed most.
Daytime (9 AM – 5 PM):
Indoor temperature tracked close to outdoors but stayed ~2°C cooler at peak (~30.5°C vs. 32.5°C).
Indicates some benefit from insulation and thermal mass, even without full ventilation.
Late Afternoon to Early Evening (5 PM – 9 PM):
This period showed a noticeable thermal plateau, where indoor temperatures stayed around 28–29°C. According to the occupants, this is typically when the air conditioning is turned on, due to rising discomfort and the cumulative heat retained from the day.
This reliance on AC during early evening highlights the gap between planned passive comfort and actual user experience, particularly when night cooling strategies aren’t fully used.
versus
While daytime comfort improved compared to pre-design conditions, the absence of night cooling, under-spec fan performance, and choice of low thermal mass materials limited the home's ability to reset and perform as intended. Despite the improvements, key passive strategies were underutilized — limiting the overall impact.
POST-OCCUPANCY – WHAT THE PARENTS SAY
“The home was built to cool naturally, but lived experience revealed where design and daily habits didn’t align.”
The parents appreciated the quiet, shaded quality of the home, especially on hot afternoons. The insulation, ceiling fans, and thoughtful layout made the space feel comfortable without relying heavily on air-conditioning during the day.
However, the design's full potential wasn’t realized due to night ventilation remaining unused — for several understandable reasons:
Comfort and safety concerns: Despite grilles, the parents felt uneasy sleeping with open windows.
Alarm system limitations: The window sensors were not designed to accommodate ajar openings.
Lack of secure openings in common areas: Living room windows lacked grilles or screens, further discouraging night flushing.
As a result, the house remained sealed day and night, blocking one of the most critical passive strategies: cooling the structure overnight.
LESSONS LEARNED – THINGS WE COULD HAVE DONE BETTER
“No design is ever perfect. But every project gives us a clearer sense of what works — and what could be better next time.”
Lesson 1: More Tree Shading in the Courtyard
Limited planting led to increased solar heat gain in the living room. Denser greenery or vertical shading elements would have softened this exposure.
Lesson 2: Stronger Shading for West-Facing Bedrooms
The bedrooms that receive harsh afternoon sun could have benefitted from deeper landscaping or overhangs. This would have reduced the need for air conditioning, especially in the evening.
Lesson 3: Encouraging Night Ventilation Habits
Despite being designed for night flushing, the strategy wasn’t used. Practical enablers — such as secure insect screens, grille-covered openings, or alarm system adjustments — could have made occupants feel more comfortable using this feature.
Lesson 4: Install More Ceiling Fans
Adding fans in the living and kitchen areas would further improve thermal comfort, especially when windows are kept closed for security or weather reasons. Air movement is often just as important as air temperature.
Lesson 5: Adjusting Chimney Fan Schedule
The current 9 PM–9 AM schedule works well: during this period, outdoor temperatures are generally lower than indoor, supporting airflow and temperature balancing.
Lesson 6: Verifying Equipment & Material Choices
Beyond scheduling, fan performance matters. The installed chimney ventilation fans were underpowered, extracting air at only about 1/10 of the intended rate. Although the selected fans met the required airflow on paper, their actual performance did not match the technical specifications during operation. This highlights the importance of verifying actual fan airflow — through commissioning, site testing, or independent performance checks — to ensure design expectations are met and passive strategies function as intended.
As for material choices, wooden floors were used in the bedrooms, which are poor at storing and releasing heat. Opting for materials like tile, stone, or marble would have enhanced the home’s thermal mass, helping to absorb coolness at night and release it during the day for better passive comfort.
CLOSING THOUGHTS – A BALANCE OF DESIGN AND HABIT
“Even when not fully realized, passive strategies offer measurable comfort benefits. But comfort isn’t just built — it’s lived. The way a space performs depends not only on design, but also on how it's used.”
With partial implementation, the house performs better than a typical home in its climate. But this experience highlights a key truth: The success of passive strategies depends not only on the design but also on how people live within them.
Photo gallery
Acknowledgement
The following IEN staff also worked on this project, namely Gregers Reimann, Mathieu Testan and Marine Guinée