As extreme temperatures rise, new home designers may be wise to combine traditional and high-tech methods of passive cooling and ventilation
I recently watched a video about a primary school in sub-Saharan Africa, built under the Aga Khan Architecture Award program, where three “natural” techniques—curved roofs harnessing the Venturi effect, walls with high thermal mass, and strategic ventilation—were used to passively manage extreme heat. That sparked a question in my mind: Could modern homes in Phoenix, Arizona, or other scorching cities be redesigned to employ these same principles at scale, as heatwaves intensify?
1. Venturi-style wind-catching roofs
In the African school, a curved roof creates a Venturi effect—where the narrowing pathway accelerates airflow, pulling cooler air into classrooms and ejecting heat overhead. The same principle can be applied using modern materials.
I found the above example of a structure built as a test study in Malaysia, with a “windcatcher” integrated into its design. If you follow the link, you can download the floorplans and other details. (If you have trouble with the link, the title of the article is “Empirical study of a wind induced ventilation tower under hot and humid climactic conditions.”)
The traditional windcatcher—or “malqaf”—is a direct parallel to this design: a tower-like structure that channels breeze down and through shaded, thermally massive interiors. Modern hybrids add solar chimneys—ventilation stacks heated by sun-warmed air that rises and draws cooler air through the house. These have gained traction in sustainable architecture circles.
Real-World Application
While not yet common in suburban Phoenix, interest is growing. A 2024 Guardianarticle highlighted increasing testing of green roofs and solar chimneys as cost-effective cooling strategies. Passive solar design firms in the U.S. Midwest have incorporated windcatcher-like towers, though precise thermal performance data for Phoenix-region homes is still emerging.
2. Thermal mass walls
As intended, the African school’s thick earthen walls act as thermal batteries—absorbing heat during the day, slowing its release into the interior, and radiating it outward at night. The walls are not flat. They’re crenellated, designed to create more surface area as well, with an uneven pattern.
Thick walls with a broken plane allow for more surface area to absorb and discharge heating. Image source: Aga Khan Architecture Award program
Modern counterpart: insulated thermal mass & phase-change materials
Contemporary homes can replicate this mass effect with insulated concrete forms (ICFs), concrete block, adobe or rammed earth walls, stone veneer, and even special phase-change materials that give and take heat from walls. All of these options store and release heat gradually, leveling interior temperature swings.
Supporting data
A study in Environmental Research and Sustainability found that thick green roof systems and thermal mass walls reduce summer heat by up to 20 °C, cutting cooling needs by 25–80 percent. Another analysis of Chicago’s city-hall green roof showed surface temperatures drop by an average of 30 °C during summer. This isn’t Africa—it’s real-world U.S. data.
3. Secondary roof shading (including solar panels)
We know that tree shading keeps roofs cooler, but they also pose a hazard when high winds strike. Recent studies have found that solar panels perform a similar function, acting not only as clean energy generators, but also as a first line of defense against heat, underneath a secondary roof.
“The results indicated that heat gain and cooling load of the PV roof were attenuated while heating load increased. The daily load of flat and tilted overhead PV roofs were reduced by 77.4% and 69.4%, while integrated energy efficiency were 63.35% and 62.73%, respectively.”
Some caveats should be noted. First, an aluminum frame can re-radiate long-wave heat downward—but overall shading and energy offsets are positive. In addition, if the panels are attached too close to the roof surface, they can slow the natural cooling of the roof during nighttime hours. Thought should be given to allowing greater airspace between the roof and the panels—Editor
A Desert Prototype
So, what might an extreme-heat-ready home look like in a place like Phoenix? Let’s apply our three passive principles.
Curved or towered roof for Venturi ventilation, ideally east–west oriented, with passive solar chimney support for hot air extraction.
Insulated thermal mass walls—e.g., ICF, thick concrete, or adobe—to buffer high daytime heat.
A dual-layer roof: an upper photovoltaic array over a ventilated deck, underlaid by a cool-roof material or radiative-cooling coating. This tiered roof shades and slow-release insulates the home.
And What Else?
These are not the only heat-beating strategies, just three of the most effective ones. It’s important to combine them with the other strategies out there that we know are highly effective at reducing heat gain in homes: radiant foil barriers, adding a layer of rigid foam to roof decks, reflective paints, reflective shingles and extended eave overhangs to keep summer sun out of the home and optimal insulation.
Why This Matters
As global temperatures climb, residential HVAC demand is poised to overwhelm power infrastructure and drive emissions higher. Combining Venturi airflow systems, thermal mass insurance, and PV/shade systems could transform how we build for heat—reshaping homes from reactive to proactive, passive to predictive.
Publisher’s Note: Green Builder's 20th Anniversary celebration is sponsored by: Carrier,Trex, and Mohawk.
Veteran journalist Matt Power has reported on innovation and sustainability in housing for nearly three decades. An award-winning writer, editor, and filmmaker, he has a long history of asking hard questions and adding depth and context as he unfolds complex issues.
Keeping Homes Cool Without Air Conditioning
As extreme temperatures rise, new home designers may be wise to combine traditional and high-tech methods of passive cooling and ventilation
I recently watched a video about a primary school in sub-Saharan Africa, built under the Aga Khan Architecture Award program, where three “natural” techniques—curved roofs harnessing the Venturi effect, walls with high thermal mass, and strategic ventilation—were used to passively manage extreme heat. That sparked a question in my mind: Could modern homes in Phoenix, Arizona, or other scorching cities be redesigned to employ these same principles at scale, as heatwaves intensify?
1. Venturi-style wind-catching roofs
In the African school, a curved roof creates a Venturi effect—where the narrowing pathway accelerates airflow, pulling cooler air into classrooms and ejecting heat overhead. The same principle can be applied using modern materials.
A Real-World Case Study
Image source
I found the above example of a structure built as a test study in Malaysia, with a “windcatcher” integrated into its design. If you follow the link, you can download the floorplans and other details. (If you have trouble with the link, the title of the article is “Empirical study of a wind induced ventilation tower under hot and humid climactic conditions.”)
The traditional windcatcher—or “malqaf”—is a direct parallel to this design: a tower-like structure that channels breeze down and through shaded, thermally massive interiors. Modern hybrids add solar chimneys—ventilation stacks heated by sun-warmed air that rises and draws cooler air through the house. These have gained traction in sustainable architecture circles.
Real-World Application
While not yet common in suburban Phoenix, interest is growing. A 2024 Guardian article highlighted increasing testing of green roofs and solar chimneys as cost-effective cooling strategies. Passive solar design firms in the U.S. Midwest have incorporated windcatcher-like towers, though precise thermal performance data for Phoenix-region homes is still emerging.
2. Thermal mass walls
As intended, the African school’s thick earthen walls act as thermal batteries—absorbing heat during the day, slowing its release into the interior, and radiating it outward at night. The walls are not flat. They’re crenellated, designed to create more surface area as well, with an uneven pattern.
Thick walls with a broken plane allow for more surface area to absorb and discharge heating. Image source: Aga Khan Architecture Award program
Modern counterpart: insulated thermal mass & phase-change materials
Contemporary homes can replicate this mass effect with insulated concrete forms (ICFs), concrete block, adobe or rammed earth walls, stone veneer, and even special phase-change materials that give and take heat from walls. All of these options store and release heat gradually, leveling interior temperature swings.
Supporting data
A study in Environmental Research and Sustainability found that thick green roof systems and thermal mass walls reduce summer heat by up to 20 °C, cutting cooling needs by 25–80 percent. Another analysis of Chicago’s city-hall green roof showed surface temperatures drop by an average of 30 °C during summer. This isn’t Africa—it’s real-world U.S. data.
3. Secondary roof shading (including solar panels)
We know that tree shading keeps roofs cooler, but they also pose a hazard when high winds strike. Recent studies have found that solar panels perform a similar function, acting not only as clean energy generators, but also as a first line of defense against heat, underneath a secondary roof.
Research snapshot
“The results indicated that heat gain and cooling load of the PV roof were attenuated while heating load increased. The daily load of flat and tilted overhead PV roofs were reduced by 77.4% and 69.4%, while integrated energy efficiency were 63.35% and 62.73%, respectively.”
Some caveats should be noted. First, an aluminum frame can re-radiate long-wave heat downward—but overall shading and energy offsets are positive. In addition, if the panels are attached too close to the roof surface, they can slow the natural cooling of the roof during nighttime hours. Thought should be given to allowing greater airspace between the roof and the panels—Editor
A Desert Prototype
So, what might an extreme-heat-ready home look like in a place like Phoenix? Let’s apply our three passive principles.
Curved or towered roof for Venturi ventilation, ideally east–west oriented, with passive solar chimney support for hot air extraction.
Insulated thermal mass walls—e.g., ICF, thick concrete, or adobe—to buffer high daytime heat.
A dual-layer roof: an upper photovoltaic array over a ventilated deck, underlaid by a cool-roof material or radiative-cooling coating. This tiered roof shades and slow-release insulates the home.
And What Else?
These are not the only heat-beating strategies, just three of the most effective ones. It’s important to combine them with the other strategies out there that we know are highly effective at reducing heat gain in homes: radiant foil barriers, adding a layer of rigid foam to roof decks, reflective paints, reflective shingles and extended eave overhangs to keep summer sun out of the home and optimal insulation.
Why This Matters
As global temperatures climb, residential HVAC demand is poised to overwhelm power infrastructure and drive emissions higher. Combining Venturi airflow systems, thermal mass insurance, and PV/shade systems could transform how we build for heat—reshaping homes from reactive to proactive, passive to predictive.
Publisher’s Note: Green Builder's 20th Anniversary celebration is sponsored by: Carrier, Trex, and Mohawk.
By Matt Power, Editor-In-Chief
Veteran journalist Matt Power has reported on innovation and sustainability in housing for nearly three decades. An award-winning writer, editor, and filmmaker, he has a long history of asking hard questions and adding depth and context as he unfolds complex issues.Also Read