FREQUENTLY ASKED QUESTIONS ABOUT BUILDING WITH HEMP HEMPSTEADS.INFO || ALEMBICSTUDIO.COM {Lab} Report Creating Hempsteads™ Why Hemp Instead... by Tim Callahan Building is something that I’ve done, in one form or another, my entire life. Maybe it started with the tree-houses that I built with my father nearly half a century ago. This inspired my work as a design engineer in the fields of residential and commercial construction, along with naval architecture for 30 years. Hemp as a building material was first introduced to me in 2007. Following the publication of “Building Green”, a book I co-authored. I was invited to present at a Timber Framers Guild conference to address the use of natural building materials in conjunction with timber frame structures. Afterwards, I was approached by a woman that told me about the home she had built for herself in Quebec using a hemp-lime insulating wall infill. I was curious, but initially skeptical of the hemp-lime product, as I tend to be cautious whenever someone approaches me with extraordinary zeal about the latest thing that is going to save the planet. Upon returning home, I quickly became engrossed in other things, and forgot about her hemp house. In 2008, I entered into a joint- venture to design and construct the Nauhaus Prototype. One of our design goals was to achieve Passive House certification, and while evaluating a number of wall/insulation systems that would help us to meet the criteria for PH performance, I started to see why the woman from Quebec was so excited about her hemp house. We evaluated a number of wall systems that would meet the Passive House criteria for R-value and air- tightness, but they tended to involve too many components and layers, and seemed to present no shortage of opportunities for error. My then-business partner, and co- author, encouraged me to look into hemp in more detail, and following further research and testing we committed to using it for the Nauhaus Prototype. While any Passive House requires particular attention to detail, the monolithic nature of the hemp wall created a welcoming challenge that was well-suited to our goals. The carbon-sequestration aspect of the system was another factor in our considerations. Depending on the lime- binder that is used, the materials can actually be carbon-negative. The most compelling reason, to me, to consider this material as a component of a building is that it provides a powerful, passive assist in maintaining healthy indoor air quality. In concert with other thoughtfully chosen materials, hempcrete helps to maintain a toxin and mold-free environment for persons with chemical sensitivities. In league with my associates at Alembic Studio, LLC, I feel privileged to continue to push the envelope in the marriage of ultra-efficient systems with healthy, natural-building methods. If, after reading the following information you want to know more about building with hemp, please contact us! CONTENTS FORWARD Tim Callahan, Technical Design Analyst of Alembic Studio, LLC and the US leading hemp design expert, explains why he’s such a fan of building with hemp. BUDGET Construction is a huge investment of time and money. Learn how hemp will affect your budget. ADVANTAGES Hemp is a natural material with many uses and perks. See if it fits with your goals. FAQ Get the facts! Here are some frequently asked questions we’ve received from the hemp-curious. ALEMBIC LABORATORY DISTILLS: HEMP AS A BUILDING MATERIAL FALL 2015
Transcript
FREQUENTLY ASKED QUESTIONS ABOUT BUILDING WITH HEMP HEMPSTEADS.INFO || ALEMBICSTUDIO.COM
{Lab} ReportCreating Hempsteads™
Why Hemp Instead... by Tim Callahan
Building is something that I’ve done, in one form or another, my entire life. Maybe it started with the tree-houses that I built with my father nearly half a century ago. This inspired my work as a design engineer in the fields of residential and commercial construction, along with naval architecture for 30 years.
Hemp as a building material was first introduced to me in 2007. Following the publication of “Building Green”, a book I co-authored. I was invited to present at a Timber Framers Guild conference to address the use of natural building materials in conjunction with timber frame structures. Afterwards, I was approached by a woman that told me about the home she had built for herself in Quebec using a hemp-lime insulating wall infill. I was curious, but initially skeptical of the hemp-lime product, as I tend to be cautious whenever someone approaches me with extraordinary zeal about the latest thing that is going to save the planet. Upon returning home, I quickly became engrossed in other things, and forgot about her hemp house.
In 2008, I entered into a joint-venture to design and construct the Nauhaus Prototype. One of our design goals was to achieve Passive House certification, and while evaluating a number of wall/insulation systems that would help us to meet the criteria for PH performance, I started to see why the woman from Quebec was so excited about her hemp house.
We evaluated a number of wall systems that would meet the Passive House criteria for R-value and air-tightness, but they tended to involve too many components and layers, and seemed to present no shortage of opportunities for error.
My then-business partner, and co-author, encouraged me to look into hemp in more detail, and following further research and testing we committed to using it for the Nauhaus Prototype. While any Passive House requires particular attention to detail, the monolithic nature of the hemp wall created a welcoming challenge that was well-suited to our goals.
The carbon-sequestration aspect of the system was another factor in our considerations. Depending on the lime-binder that is used, the materials can actually be carbon-negative.
The most compelling reason, to me, to consider this material as a component of a building is that it provides a powerful, passive assist in maintaining healthy indoor air quality. In concert with other thoughtfully chosen materials, hempcrete helps to maintain a toxin and mold-free environment for persons with chemical sensitivities.
In league with my associates at Alembic Studio, LLC, I feel privileged to continue to push the envelope in the marriage of ultra-efficient systems with healthy, natural-building methods. If, after reading the following information you want to know more about building with hemp, please contact us!
CONTENTS
FORWARD Tim Callahan, Technical Design Analyst of Alembic Studio, LLC and the US leading hemp design expert, explains why he’s such a fan of building with hemp.
BUDGET Construction is a huge investment of time and money. Learn how hemp will affect your budget.
ADVANTAGES Hemp is a natural material with many uses and perks. See if it fits with your goals.
FAQ Get the facts! Here are some frequently asked questions we’ve received from the hemp-curious.
ALEMBIC LABORATORY DISTILLS: HEMP AS A BUILDING MATERIAL FALL 2015
FREQUENTLY ASKED QUESTIONS ABOUT BUILDING WITH HEMP HEMPSTEADS.INFO || ALEMBICSTUDIO.COM
Q&A How will using Hemp affect my Budget?
I wanted to know more info regarding building a home with hemp and the costs associated with that.
The building process with hemp follows a format that is a bit different than typical construction, but the methods employed are simply variations on common themes. An experienced contractor, supported by a thorough set of drawings, should be confident in their ability to successfully build with hemp. The up-front costs in using hemcrete® can add 8%-12% to the overall price of a home. We feel this cost is more than offset by the increase in air-quality, thermal performance and the low-maintenance aspects of the material.
Any hempcrete installation should be overseen by an individual certified in its application. It also requires extra design and planning attention in the beginning stages of a project. Alembic Studio is able to provide this service, or we can connect you with a certified installer in your region.
Will it take longer to build my house with hemp, versus regular construction?
Most likely. As with any masonry-type construction, there are some limitations to the installation. For example, if the temperature gets too low, or there is excessive moisture in the air it slows the curing time of the lime-binder. The lime-binder can take anywhere from 4-8 weeks to completely cure. The sequence of trades and inspections is a bit different as well. These are primarily planning and organization issues, and easily established in the work-flow.
I was wondering how much it would cost me to insulate walls with hemp.
I wish there were an accurate stock answer for this question; it is safe to say that it will be more than most other insulation. Other insulations however, may have hidden expenses associated when assessing true costs, that is, when considering personal health, building maintenance and longevity issues.
I want to build a net-zero house and want to know how hemp preforms from an energy standard.
Hempcrete is not just an insulator; it prevents damp and mold growth, and buffers temperature and humidity, making the building a healthy environment. From an R-per-inch standpoint, there are many materials that have higher insulating values than Hemcrete®. Having said that, our hempcrete walls are typically specified as a minimum R-28. For our clients that want to achieve a net-zero building, we design for very minimal heating and
cooling loads - this is much more economical than having to compensate for lack of planning by spending $4000 per kilowatt for photo-voltaic.
I have heard that a hempcrete wall is carbon negative- what’s the deal?
According to this study, 2000 square feet of 12” thick hemcrete® wall, with lime finish on both sides, has the potential to sequester 2,1480 Kg of CO2, or emit 372 Kg of CO2. This wide range is due to variations in test methods and binder and finish recipes.
I am building an the off-grid eco-house and wanted to use Hempcrete. Where did you guys buy yours from and what was the cost?
Current pricing may be obtained from the following companies:
Hemp Technologies
American Lime Technology
LimeTechnology U.K.
ALEMBIC LABORATORY DISTILLS: HEMP AS A BUILDING MATERIAL FALL 2015
* Note to reader: Generally, the use of a hemp-lime mixture as an insulating in-fill is referred to as hempcrete. Hemcrete® refers to a mix that uses a proprietary lime binder.
FREQUENTLY ASKED QUESTIONS ABOUT BUILDING WITH HEMP HEMPSTEADS.INFO || ALEMBICSTUDIO.COM
I love the aesthetics of hemp homes but I am chemically sensitive. Would hemp be a good option for me?
We’ve found that the ability of a Hemcrete® wall to mitigate interior moisture issues is one of its most desirable qualities. The hygroscopic qualities of the lime binder, combined with a (very alkaline) ph of 12, create an environment that will not sustain mold growth (see chart at right).
Personal reports from inhabitants support this evaluation. This property of the material was one of the primary reasons that we were originally attracted to it as a construction system. It is interesting to note that lime has been in use as a surface preservative for wood for thousands of years.
Will a hemp house catch on fire easier?
A Hemcrete® wall system is significantly more fire resistant than a typical insulated wall. The shiv within the wall is coated with lime and is finished with about 3/4” of lime stucco on the outside, and 1/2” on the inside.
This has led to increased interest in implementing this material in areas prone to wildfires. The type of detailing that ensures high thermal performance, i.e. the attention to joints at doors, windows, and places where the insulation abuts structural elements, are the same details that make the building even more resistant to fire. Fire resistance is rated at 1 hour by tests performed by the British Board of Agrément (BBA).
How strong is hemp as a wall system?
Pretty darn strong, but it’s not concrete - it is a fraction of the weight, and about 1/20 of the compressive strength of concrete. Keep in mind that the Hemcrete® does not function as a structural component. In our region, we design for seismic zone 2.a, and winds loads (typically) of 90m.p.h. With certain limitations, we are able to use cast Hemcrete® as a shear wall. For a recent project on the mid-Atlantic coast, we designed for seismic zone 2 and 130 m.p.h. wind loads. These wind loads, significantly in excess of typical specifications, were addressed with engineered steel brace frames at five locations in the exterior and interior walls.
Any construction will require an engineers stamp. We are fortunate to have local firms that have worked on a number of projects using hemp and really understand the material.
Original graphic courtesy of Environment Canada (www.ns.ec.gc.ca)
Original Graphic courtesy of Hempcrete Australia, PTY LTD. Hempcrete wall detail.(www.hempcrete.com.au)
Q&A Uses & Advantages of Hemp Construction
ALEMBIC LABORATORY DISTILLS: HEMP AS A BUILDING MATERIAL FALL 2015
FREQUENTLY ASKED QUESTIONS ABOUT BUILDING WITH HEMP HEMPSTEADS.INFO || ALEMBICSTUDIO.COM
Can Hemcrete® be used in a basement?
Hemcrete® is not a structural element and may not be used as a foundation material. As a wall and insulation system, a 1”-0” clearance to the ground is standard practice. Hempcrete may be used as a finished interior wall inside the foundation below grade, provided proper ventilation is ensured between the finished Hemcrete® and the structural wall.
What is the R-value of Hemcrete®?
The R-value varies with the density of the mix - the more binder, the less insulation. Additional binder increases the density of the material and hence its heat-transmission properties. The mix that we typically specify has an R-value of about 2.4. For a 12” wall, this yields over R-28 for the wall.
There are other arguments that are made for the inherent thermal mass and hygroscopic properties of the material contributing to the effective R-value. To our knowledge, there is no test data to support this claim, and it does not enter into energy calculations.
What are my finish options if we go with a hemp wall system?
We recommend that the exterior be finished with an approved system like Baumit®.
The interior may be finished with lime render, clay plaster, or lime-over-clay. Mineral colorants can be added to the render to provide a wide range of color options. Interior lime surfaces may have surface applied minerals mixed in a water solution and spray applied.
The very important thing to remember with any finish applied over the Hemcrete®, is that it must be vapor permeable- this leaves out most commercial paints. If you have any unanswered concerns about the suitability of a finish, don’t use it.
* Note to reader: With the heightening interest in hempcrete homes, Alembic Studio responded and created an online, open repository knowledge base called Hempsteads.info. Focusing on providing unbiased hemp building advice and presenting vital resources for professionals and homeowners. This design firm lives up to its responsibility of spreading the benefits and the proper implementation of hemp. As supporters and champions of the industrial hemp movement, Alembic welcomes fellow pioneers to share their own experiences and usher in a construction industry renaissance, including hemp as a necessary part towards realizing net-zero sustainable structures.
Q&A Uses & Advantages of Hemp Construction
ALEMBIC LABORATORY DISTILLS: HEMP AS A BUILDING MATERIAL FALL 2015
FREQUENTLY ASKED QUESTIONS ABOUT BUILDING WITH HEMP HEMPSTEADS.INFO || ALEMBICSTUDIO.COM
Q&A frequently asked questions...
Technically, industrial hemp and marijuana are both Cannabis Sativa. Industrial hemp is the non-psychoactive, low-THC, oilseed fiber strain of the Cannabis plant. Hemp has absolutely no use as a recreational drug. Think of the Cannabis Sativa grouping of plants as the Canine family, who’s genetic makeup has been altered to give way to breeds like Chihuahuas (High yield, high-protein seed producing Cannabis), Bassett Hounds (flowering, high THC marijuana for medical and psychoactive aspects), and Great Danes (low THC, thick stem Cannabis - industrial hemp strain for building material).
Does the hemp have an odor? The part of the plant that is mixed with a binder is the woody stock, referred to as shiv. The raw shiv has an odor similar to many other dried plants, and smells a bit like straw...not marijuana.
Can I make my own binder?
Dry hemp stem showing fibers.
There are those that mix their own binder from common recipes, as it is less expensive than purchasing pre-mixed binders. There are two primary factors that play into deciding whether this is the best choice for you, not the least of which is product liability. The other is having the proper engineering and technical data required by your local building department.
Tradical® binder is a commercially available binder that has been extensively tested for use in construction applications with hemp shiv. The good news is that as a building material, lime has been used in construction for thousands of years, and there is a wealth of material data available if you are diligent.
Will I be able to get hemp permitted in my jurisdiction?
We have found that when presenting to code officials, it is important to emphasize the essential characteristic of the hempcrete - it is an insulation system with unique hygroscopic qualities. We have successfully permitted projects in seismic zone 2a, as well as in coastal regions with 130 mph wind loads.
Establishing a relationship with the relevant officials early on, and ensuring that their requirements are satisfactorily addressed prior to construction is essential. Their position dictates they be conservative when confronted with something that they are not familiar with. In our experience, we have found that when they are more fully acquainted with the material, they start to embrace it and do what they can to make the permit process run smoothly.
We are wondering if you provide any services other than consulting? From your website it doesn't look like you guys are builders.
After being involved in design-build projects for many years, we decided to focus more exclusively on high-efficiency homes utilizing natural materials about 7 years ago. We can help with all stages of your project, from being your principle designers, to serving as consultants on your design team. We are a full-service design practice; from the initial land acquisition through design, permitting and construction oversight. Every successful project is the result of a collaborative effort between the core team of our clients, General Contractor and ourselves.
What is the difference between “hemp” and “marijuana”?
ALEMBIC LABORATORY DISTILLS: HEMP AS A BUILDING MATERIAL FALL 2015
