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Architecture2030.org and the Carbon Smart Materials Palette - HEMPCRETE

from architecture2030.org Architecture 2030’s mission is to rapidly transform the global built environment from the major contributor of greenhouse gas (GHG) emissions to a central part of the solution to the climate crisis.

Architecture 2030 pursues two primary objectives:

  • to achieve a dramatic reduction in the energy consumption and greenhouse gas (GHG) emissions of the built environment; and,

  • to advance the development of sustainable, resilient, equitable, and carbon-neutral buildings and communities.

Architecture2030.org has been creating a 2030 Palette, a free online platform providing a database of sustainable design principles, strategies, tools and resources at your fingertips.



Why the 2030 Palette?

Over the next 15 years, an area equal to the entire building stock of the Western Hemisphere will be redesigned, reshaped, and rebuilt. How we plan and design this new construction will determine whether climate change is manageable or catastrophic. With the 2030 Palette, designers will have the tools they need to design adaptive, resilient, and Zero Net Carbon built environments.


Carbon Smart Materials Palette, a project of Architecture 2030, is an immediately applicable, high-impact pathway to embodied carbon reductions in the built environment .


WHY EMBODIED CARBON?

Annually, embodied carbon is responsible for 11% of global GHG emissions and 28% of global building sector emissions. However, as we trend toward zero operational emissions, the impact of embodied emissions becomes increasingly significant. It is therefore crucial to address embodied emissions now to disrupt our current emissions trend, and because the embodied emissions of a building are locked in once the building is constructed and cannot be taken back or reduced.


This week, let's take a look at one Carbon-Smart Material HEMPCRETE



CARBON IMPACT OF HEMPCRETE

Hempcrete is a monolithic wall system that consists of hemp hurd, lime, and a hydraulic additive over a structural support. Hemp hurds of processed quality are currently available to US markets from the Netherlands, China, and possibly a few small scale processors in the US and Canada.


Lime, in this application uses about 80% less energy to calcine than when used in concrete.  As an “air set” material, the lime in hempcrete reabsorbs the CO2 that is driven off in calcining [CaCO3 -> CaO + H2O -> Ca(OH)2 -> CaCO3 with evaporation of water and sorption of CO2].


Metrics

  • hemp based composite sequesters and stores an estimated 325 kg carbon per metric ton of hemp based composite1




CARBON SMART ATTRIBUTES

Hemp is fast-growing

Hemp is a very efficient and fast-growing plant, growing as tall as 15 feet in a season.

Hemp utilizes an agriculture by-product

Hemp is typically grown for fiber, seed, medicinal CBD’s, animal feed and other uses. Hempcrete uses the woody core (hurd) of the hemp plant that is often considered a waste or byproduct.  

Thermal Performance

Hempcrete wall systems are highly insulative and act as thermal mass. Walls that are typically 12” thick provide requisite R-Value (~2.5/in.)  

Durability: moisture, fire, and insect Resistance

The hempcrete wall system transmits humidity, is fireproof, deters insects and rodents, resists mold, (can recover from water penetration without molding), has excellent acoustic performance, is recyclable, has no VOC or other toxins, and can endure for centuries.

Hempcrete can create an air-tight wall assembly

Finished with lime render, there is no opportunity for air flow when the finish is properly wrapped to windows and door openings.  

Hempcrete can be used in multiple applications

Hempcrete could be used in new construction or retrofitted over existing framing.  With proper equipment, hempcrete can be sprayed, including onto masonry walls, or as pre-cast panels.  There is some speculation that a hemp/lime slurry could be 3-d printed.


ACKNOWLEDGED CHALLENGES, QUESTIONS & UNKNOWNS

Hemp hurd processing is currently available to US markets from the Netherlands, China, and a few small scale processors in the US and Canada. The embodied carbon of hempcrete could be greatly reduced if hurd processing and binder formulation were made locally or regionally available.


The various growth habits and varieties of hemp present different processing challenges.  Tall plants that are harvested for fiber are the easiest to process for hurd. Bushy varieties grown for seed require a different processing method; these stems may be more suitable for paper and other products


Natural Hydraulic Limes (NHLs) are not typically mined in North America, as there have been few uses for them before.Sources of naturally occurring hydraulic limes are not well studied or documented in the US, though they may exist wherever ancient sea beds were exposed to volcanic activity. Alternatively, correct proportions of silicates and other mineral additives may be formulated to mimic the NHLs of European usage.  (Additives are currently available in Europe.) The contents include commonly occurring minerals in the form of clay, silicates/alumina, and ashes.


Proprietary blends of hempcrete binder are available in the US.  Price and quality need to be evaluated for practical use.


Hempcrete properties vary depending upon method used to build. Though hand packing can create inconsistent densities, it hasn’t been shown to affect performance.  


Studies indicate insignificant performance gain between 9”(22cm) and 12”(30cm) walls in the UK.  


Studies need to be conducted to validate properties of hempcrete, and building codes adapted, so that municipalities can permit these buildings. Criteria needs to be adjusted towards performance objectives rather than other industry prescribed conveniences.

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