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In its most traditional applications, stucco façades are created by laying two or three coats of plaster directly onto the face of masonry or wood. As a result of this age-old building technique, stucco is sometimes criticized as lacking adaptability, since it is not traditionally manipulated to include insulation. However, as sustainable design takes hold and asserts itself as a central component to all successful constructions today, many architects are experimenting with the possibility of achieving an exterior stucco finish, while also adding the benefits of rigorous insulation. This way, aesthetics and functionality can be merged into one.
In this article, we investigate the opportunities that stucco can provide, specifically under passive house principles. Leveraging the brilliant products of manufacturers like Sto, is it possible to create a highly energy-efficient passive house that is enclosed in a stucco façade?
Located in Brooklyn, Knickerbocker Commons by Chris Benedict R.A. harnesses Sto insulation with a stucco finish to conform to passive house building standards
What is a passive house?
“Passive house” is a building philosophy that first emerged in Germany. Spearheaded by an independent research institute called The Passive House Institute (PHI), today, the concept is internationally recognized as a performance-based energy standard in construction. In the US, the Passive House Institute US (PHIUS) has flourished as a non-profit committed to making high-performance passive buildings the mainstream market standard.
According to the PHI, passive houses are energy efficient, comfortable and affordable building that uses less than a quarter of the energy of a traditionally powered building. Passive buildings are capable of maintaining a comfortable interior climate without active heating and cooling systems.
Via PHIUS
To achieve this, the standards place a strong emphasis on creating a high-performing, air-tight thermal enclosure. The resulting building membrane will trap a desirable interior temperature and reduce heat loss, regardless of the exterior climate conditions. Therefore, passive house building principles are highly relevant to this investigation include:
- Continuous insulation throughout its entire envelope without thermal bridging.
- Airtight building envelope that prevents infiltration of outside air and loss of conditioned air.
- Solar gain is managed to exploit the sun’s energy for heating and cooling purposes.
Karuna House by Hammer & Hand is an award winning passive house that features a stucco and cedar-clad façade; via Thermocromex
Are there precedents?
If you intend on designing a passive house with a stucco façade, it is useful to have successful precedents to look towards that may inspire your process. Fortunately, in Brooklyn and Manhattan, dozens of townhouses and small apartment buildings are undergoing retrofits based on passive-house principles. Many maintain their turn of the century brownstone façades and existing footprint while gut renovating the interior to create a continuous air barrier.
Pictured above, Tighthouse Passive House by ZeroEnergy Design was the first official Certified Passive House in New York City. While maintaining historical architectural elements, the building went from “no insulation to super-insulated”. The enclosure was created using EPS foam and a stucco finish. The designers estimate that at Tighthouse, heating will cost a mere $260 per year and cooling $52 per year.
Sto’s products offer excellent insulation, which reduce thermal bridging; via Sto
How can I achieve similar results?
Sto is one manufacturer that is simultaneously committed to sustainability and superior technical performance. Focused on everything to do with the wall element of architecture, they create various insulated façade systems that are designed to be easily paired with a stucco finish. With these products, Sto seeks to enhance curb appeal, extend building life and advance interior comfort, all while maintaining a driving commitment towards reducing fossil fuel consumption and cutting heating and cooling costs.
StoPowerwall Systems; via Sto
While many of their products comply, StoPowerwall Stucco Systems offer one approach to tackling these challenges. According to Sto, “these products can be installed faster than conventional stucco, with coatings and finishes that are integrally colored and bridge hairline cracks, enhancing the weather resistant and long term appearance of your cladding.” Typically, they consist of six key components: a substrate, air and moisture barrier, continuous insulation, drainage mat and cavity, Powerwall stucco and finally, a textured finish.
With all building materials today, it is essential to think about how they can be leveraged for greater-energy efficiency so that they may remain relevant in today’s ever-changing world of greener, better architecture. By pairing age-old practices like stucco with the technical capacities of leading manufacturers like Sto, this is now a tangible possibility.
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