Innovator Spotlight: Dr. Greenhouse, Inc. – Engineering Energy Efficiency for Indoor Agriculture

February 20, 2020

Nadia Sabeh, PhD, is the president and founder of Dr. Greenhouse, Inc. an engineering firm that specializes in the planning and design of HVAC systems for indoor plant environments, including controlled environment agriculture (CEA).  We visited Nadia in her Sacramento office to learn about her journey from undergraduate at UC Davis to running her own firm. 

How did you first become interested in agriculture? 

As a child, I loved insects and assumed that this would lead to a career in medicine. In high school, given the choice between a two-hour AP biology class and a one-hour physics class, I went with physics for the sole reason that I could get out of school earlier. But, after the first few classes, I was so excited about physics that, for the first time, I looked forward to coming home and reporting what I had learned that day. 

My physics teacher told me about a new program at UC Davis in biosystems engineering, where I could combine my interests in biology and physics. I applied and got in. But, since I still wasn’t convinced that I wanted to be an engineer, I also took all of the advanced biology classes required for med school. 

I did internships in physical therapy, entomology and then with Prof. Jean VanderGeynst, assisting a grad student who was doing research on growing shiitake mushrooms. In the summer before my senior year, I interned with a mushroom grower in Idaho who needed help with operations, where I fell in love with mushroom farming. The operation was growing shiitake and oyster mushrooms in a greenhouses in the dry southern Idaho climate, and we could not keep it humid enough. We tried all kinds of ways to add moisture. I came back excited about agriculture and knew how I wanted to help farmers: I wanted to help them control their environment! 

Another factor was my best friend in college who grew up on stone fruit farm in the Central Valley. I spent several school breaks at her farm and this also spurred my interest in the industry. 

Where did you do your PhD work? 

Jean encouraged me to go to Penn State, where in 2003 I got a masters in Agriculture Engineering.  I studied air distribution in mushroom farms, which are essentially vertical farms, so I was actually doing some of the earliest vertical farm research in this area. 

I finished right after 9/11. No one was hiring, and I could not find a job. Jean invited me back to her lab, and I spent the year managing students in her lab. Then I learned about a new program at the University of Arizona in Controlled Environment Agriculture. I reached out to them and applied for a fellowship. My soon-to-be best friend in grad school, Jenn Frymark (Nelkin) Jen was a big factor in convincing me to  go. I earned my PhD in Agricultural and Biosystems Engineering there in 2007.

My dissertation project was on cooling and water use efficiency for greenhouse production of tomato. Water obviously is a big issue in Arizona. I realized that, although everyone was touting hydroponics as water efficient, nobody was looking at how much water was needed to evaporatively cool a greenhouse. This was my biggest contribution – determining the full water balance of growing tomatoes in a greenhouse. I looked at different strategies for cooling, including natural ventilation. My dissertation work included air flow circulation studies in a wind tunnel using a greenhouse scale model at the National Institute for Rural Engineering in Tsukuba Science City, Japan. 

What work did you do after your PhD? 

I was interested in integrating indoor crop production with building climate control and felt stuck with the current technology. I remember discussing with my fellow PhD students how a lot of old ideas were being recycled for improving CEA. CEA usually had good access to water, but I felt this was insufficient. I thought to myself – there is this whole HVAC industry for residential and commercial buildings. Can’t we apply this technology to indoor agriculture? This was my vision  and I realized to make a reality, I needed experience in HVAC. 

So I looked for an HVAC mechanical engineering position. At Penn State, I took classes in HVAC so I had a good background.  I was hired as a junior level designer in Tucson and then moved to a job in Santa Rosa, California, which I found through a friend on LinkedIn. I did energy performance modeling there for six years and then transferred to their Sacramento office. 

I got my LEED accreditation in 2008. At that time, I was doing energy modeling, engineering design and LEED certification of projects. 

When did you decide to branch off on your own? 

Around 2014, cannabis began to gain traction. I got the opportunity to do energy modeling, design, and LEED certification with two applicants for licenses in NY State. I was instrumental to those growers competing for one of the five coveted licenses.  

I approached my employer with a business plan to form a CEA division. They sent me to Indoor Ag Con and cannabis conferences to explore the idea. Ultimately, although they appreciated my pitching this new direction, they were not able to set aside the resources to allow me to respond quickly to opportunities that were coming my way because of my expertise. 

I realized that I had the skills, credentials and potential customer base for my own business. So, with the encouragement from friends and family, I launched Dr. Greenhouse in 2017.

Tell us about the origin of your firm’s name. 

‘Dr. Greenhouse’ came out of a public workshop I held on CEA in Tucson. To promote it, the local ag extension service arranged for the local news station to interview me. The weatherman who did the interview said, “I hope you don’t mind, but around the studio we’ve nicknamed you Dr. Greenhouse.” After that, the name kind of stuck.  

What is your value proposition and how do you approach your custom consulting? 

With my three professional credentials – PhD, PE and LEED AP –  I pride myself on having the respect of and being a bridge among engineers, academia and growers. I love playing the role of interpreter between the science and its applications in engineering.

I also love to teach, and consulting is my avenue for teaching. When I consult, I try to elevate the conversation to get everyone on the same page using common terminology and best practices. 

The added value is my broad and specific expertise. I’ve dealt with a lot of different crops and facilities, so I am agnostic for both. People appreciate my no-nonsense honesty approach. I do not endorse or sell products, but I will help my clients navigate the ‘snake oil’ to find the exact solution for their unique situation. 

You’ve said it’s hard to get HVAC right for CEA. Why is that? 

Growers understand the importance of lighting because it’s visible, but it’s easy to take for granted the importance of climate control, even though HVAC accounts for half the costs of CEA.  Terms like evapotranspiration and vapor pressure deficit are just not obvious or well understood. 

In the early days of CEA, growers would buy off-the-shelf residential AC systems and install them, only to realize that relative humidity was out of control. Then they would buy stand-alone dehumidifiers, only to find that they had created more inefficiencies. 

Further, horticulture control and HVAC systems use different sensors and controllers, and so don’t interface well. For example, it was and still is common in cannabis, that when the lights go on, relative humidity tends to spike before HVAC systems can catch up. 

Four years ago, on my first indoor cannabis project, the grower told me he did not care about efficiency if I could not provide an 18-month payback, which made my jaw drop. But, this kind of made sense at the time, when the appetite for risk was low because cannabis was not fully legal. Now, the conversation is changing, especially as cannabis prices have dropped. Eventually, cannabis will be like all other commodities, that is, with razor thin margins. Rumor is that, at least in some states, growers who designed for energy efficiency will be the only ones left standing. 

Do the major HVAC companies now offer climate control systems specifically for CEA? 

The industry has come a long way in the last few years. I recently attended MJBizCon, and I saw ten times more HVAC firms there than just three years ago.   

Customization for CEA is still limited, but the major HVAC companies are starting to look at this industry and see that, instead of taking a conventional HVAC unit and putting it on a greenhouse or indoor farm, hoping it will work, we can (and need) to modify the equipment specific to plants, including using certain filters and providing good dehumidification. Some are investing research and development dollars into equipment to respond to CEA industry needs. 

How will automation of CEA change the way you approach consulting? 

Automation is basically moving plants to workers, and vertical farms are adopting this technology quickly. Labor is the number one cost, so the fewer motions a worker has to make, the better.  But it poses an interesting challenge for HVAC. As plants move through the vertical farm as they grow, it is obvious that their needs for lighting, water and nutrient requirements change. Well, it’s also true that their temperature, relative humidity and carbon dioxide requirements change. In cannabis, growers move plants from room to room, where it’s easier to control climate. But most vertical farms are basically one big room, so how will we vary climate within that space?  

What about the interface between automated horticultural systems and automated HVAC systems? 

Automated climate control systems for buildings are improving, and are good at communicating with sophisticated equipment like HVAC and occupancy sensors. But, trying to put this system on an automated greenhouse – well, that’s a whole different story. 

We need to be able to build a common interface between horticultural automation systems and automated HVAC systems, because right now they don’t communicate well with each other. HVAC manufacturers are aware of the need for ‘interpreter’ components to accomplish this.

For example, I recently had a discussion with an HVAC manufacturer that is developing an interface for monitoring and controlling HVAC systems for CEA, so that growers can see climate data and convert it to horticulturally important data. I asked why the HVAC manufacturer was not putting sensors in the grow room as well as in the equipment return. They responded that the return data was all that was relevant, even though it seems pretty obvious that the grower needs to read temperature and relative humidity in the grow room. 

What is your advice for entrepreneurs in the CEA space or who want to get in the CEA space?

It’s not easy. I saved up money and paid off a student loan and a credit card before I started my firm. I was lucky to have colleagues and friends in the industry who told me what the industry was really like. I appreciated that – the pros and cons of running a business and having employees. Good mentors are invaluable. 

When I was getting ready to launch, one of my friends who runs a non-profit for entrepreneurs asked me if my business were to fail in 5 years, would I regret more trying or not trying? I think that was motivational for me. I realized I would still be employable even if Dr. Greenhouse failed and that I would have learned an incredible amount. 

The growth in controlled environment agriculture combined with concerns over energy efficiency and reliability in California means we will likely be seeing a lot more of Dr. Greenhouse’s work in the future. 

About the author: Leanna Sweha is an attorney with an agtech background and is Program Director for AgStart. She is passionate about promoting new sustainable agriculture and food companies.


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