New Greenhouse Cooling System in Development for Hot-Climate Regions

NVAC Greenhouse design concept
A schematic section of the greenhouse showing the concept behind the NVAC greenhouse design. The added roof on the inside combined with a misting system use natural ventilation to provide cooling and air movement throughout the greenhouse with cool air movement at the plant level.

High greenhouse temperatures can be a problem in regions with hot climates. Recently, developments in protected agriculture practices for tropical and arid climates have allowed some nations to expand their food production. However, many existing greenhouse operations lack proper adaptation to their respective environments.

To address this issue, Lucas McCartney and Dr. Mark Lefsrud from McGill University’s Department of Bioresource Engineering in Quebec, Canada, have developed and patented a new greenhouse cooling system specifically designed for hot and/or humid climates.

“Our technology is an improved natural ventilation greenhouse based on structurally supported airflow and evaporative cooling-dependent temperature and humidity control,” McCartney says. “The NVAC greenhouse relies on an alternative roof and misting system design to provide cooling and air movement. The misting line functions at relatively low pressures and uses water sourced through rainwater harvesting.

With an increase in relative humidity within optimal limits, increased airflow is possible in the tropics, all the while preventing water droplets from reaching the plants.”

This cooling effect in the NVAC greenhouse is accomplished without the need for active ventilation solutions such as the use of fans or cooling pads.


The NVAC greenhouse design can be constructed as a stand-alone structure, or it can be retrofitted to the walls and roof of an existing greenhouse structure. In both cases, the combination of the roof structure and the misting system create a cooling air flow without involving additional equipment. The design is applicable year-round in hot climate regions, or during warm months of temperate and continental climates.

In numerous regions, including tropical areas such as the Caribbean, passive ventilation and cooling measures are recommended over active methods as they are simple and economically viable. The NVAC greenhouse design remains accessible to growers in all regions due to its low cost, ease of access, and low energy use.

According to McCartney and Lefsrud, advantages include:
• The alternative-design misting system cools the air and provides air movement.
• Humidity remains within optimal range; water droplets never reach the crop.
• Increased yields and access to crop varieties otherwise not suited for hot climates.
• Ease of use, installation, and maintenance with minimal energy needs.
• Can be used with existing greenhouse structures through retrofitting.

Seeking Commercial Collaboration

Since 2012, the technology has been rigorously tested and developed in several prototypes in both temperate and tropical climates. Currently, McCartney and Lefsrud are actively seeking collaboration to commercially develop the NVAC greenhouse design.

In the eventuality of a collaboration, McGill offers a license to a greenhouse cooling and air movement system, which is inherent to the roof structure of the greenhouse itself. It is an improvement to currently used natural ventilation and evaporative cooling systems. While originally conceptualized for tropical regions, this cooling and ventilation system offers benefits for greenhouses in tropical, arid, continental, and temperate climates.

For more information, go to

Topics: , ,

Leave a Reply

3 comments on “New Greenhouse Cooling System in Development for Hot-Climate Regions

  1. I am an agricultural engineer and hav a 800 ha farm in north of Sudan at 18:30N,32:35E. Iam growing vegetables and interested in your new techynologies in structure and ventilation of nethouse. How can I benifit of your techolohies. Please note that there is very high potentials to merchandise your innovation as final product system or we can work together to build and sellm it all over Sudan and other African tropicval and sub tropical areas.

  2. It looks like an interesting system but it upsets be that researchers who have received public (taxpayers) money to devise and test a system that could help people in the developing world achieve food security look to cash in on their development by patents and licenses, Essentially making it available to bigger business and creating a barrier to adoption by the smaller, poorer growers who would most benefit from the tech.

  3. I am in India and have been involved in horticulture. The biggest issue with India is its varied climate and on top of it it’s a price sensitive place. May be due to price barrier or something, there is little innovation in greenhouse design and [poor farmers are being taken for a ride by the greenhouse suppliers. We need an affordable technology for greenhouse’ cooling. The process are low but volumes are quite high so it will make business sense to introduce technology that is affordable and elongate the production time for greenhouse owners. I would be pleased if this technology is tested in India and made available to farmers. if you have reasonable expectations then it won’t be a problem to sell this concept in India or anywhere provided, of course, that it succeeds in cooling down the greenhouse air. Good Luck to the team!

More From Heating/Cooling/Ventilation...

May 15, 2018

Gotham Greens Expanding Greenhouse Production Into Baltimore

Scheduled to open in early 2019, Gotham Greens’ Baltimore facility will bring a reliable, year-round, local supply of fresh produce to serve retail, restaurant, and foodservice customers throughout the mid-Atlantic region.

Read More
Growing Innovations conference and tradeshow logo

May 14, 2018

Growing Innovations Geared to Connect Specialty Ag With Solutions

Innovation abounds in agriculture, yet it can feel sometimes as if the gap between exciting new developments and what growers actually need in their operations can be awfully wide. We at Meister Media Worldwide intend to help narrow this gap. Which is why we’re pleased to introduce Growing Innovations – an altogether new type of event that will debut Nov. 7-8 at the Las Vegas Convention Center in Las Vegas, NV. Unlike most agricultural events and trade shows, Growing Innovations is not about technology per se, nor is it about everyday issues that growers face. Instead, this new conference and tradeshow is very acutely solutions oriented. It takes as its starting point specialty crop growers’ most pressing real-world challenges – production efficiency, labor and water shortages, logistics, and data management to name just a few – and showcases advances, both current and up-and-coming, that have the greatest potential to bring […]

Read More
VYPRxPLUS (Fluence Bioengineering)

May 7, 2018

Lighting Innovator Fluence Bioengineering Acquired by Osram

Fluence specializes in LED-based horticultural systems, using Osram LED chips, for a wide variety of applications, including vertical farming and greenhouses.

Read More
Latest Stories

November 23, 2017

Climate Screens Offer Both Form and Functional Benefits

Svensson’s new line of Deco Harmony screens is designed to create better growing conditions for plants on display at retail, while enhancing the customer experience.

Read More

September 29, 2017

Vertical Farming Looks to Go Mainstream

The University of the District of Columbia is the nation’s only urban land-grant university, so it was a particularly appropriate setting for the Association of Vertical Farming (AVF) to host the AVF Summit 2017 on September 22. The summit was a mix of education, advocacy, and policy discussion about urban agriculture — vertical farming in particular — targeted at finding ways to broaden its adoption in cities around the country and around the world. You’ve probably heard quite a bit in recent months about vertical farming — systems for growing food in stacked layers in completely controlled environments, applying inputs such as light, water, and fertilizer in precise amounts. While there’s some use of these systems in greenhouse settings, in many cases, urban farmers are repurposing abandoned buildings or even shipping containers. Match the availability of these facilities in most large urban areas with big cities’ limited access to fresh, […]

Read More
Svensson Luxous 1147 FR Climate Screen

July 31, 2017

Suppliers Seek to Help Greenhouse Growers Save on Energ…

New developments in heating/cooling technology and greenhouse screening can provide long-term efficiency in your greenhouse environment.

Read More
Direct Fired Heater feature image

March 14, 2017

Researchers Examine Efficacy of Direct-Fired Greenhouse…

A team of researchers at The Ohio State University is examining the efficiency of direct-fired heating systems in comparison to ventilation costs.

Read More
NVAC Greenhouse prototype

February 15, 2017

New Greenhouse Cooling System in Development for Hot-Cl…

Researchers at McGill University in Quebec have developed an alternative evaporative cooling solution for greenhouses in warm climates, and are now seeking commercial partners.

Read More
Silver Bullet Heaters (Heat Star By Enerco) Feature

November 28, 2016

The Latest In Greenhouse Heating And Cooling Products

New developments in heating, cooling, ventilation, and humidity control technology are designed to help you manage your greenhouse environment more efficiently. Check out some of the latest offerings from leading manufacturers.

Read More
Delta T Floor Mounted Pump

August 4, 2016

How Suppliers Are Helping Greenhouse Growers Deal With …

Many growers say they are looking for more direct heating to the plant, along with better boiler and system efficiencies. Here's what two companies are doing in response.

Read More
Geranium Injured By Ethylene

July 20, 2016

How To Prevent Greenhouse Heating Leaks

Ethylene from malfunctioning greenhouse heaters can lead to crop injury, while carbon monoxide can lead to worker illness. Know the symptoms and how to check greenhouse heaters to avoid these concerns.

Read More
Schaefer Exhaust Fan

June 26, 2016

What’s New In Greenhouse Cooling

Cooling and ventilation companies, as well as structures suppliers, are working to help growers manage efficiencies. Here are some of their latest innovations.

Read More
Natural Ventilation In A Venlo type greenhouse

April 9, 2016

How To Fine-Tune Your Greenhouse Cooling And Ventilatio…

Like most equipment, greenhouse components and machinery must be serviced regularly to keep them in good working order.

Read More
Metrolina Greenhouses keeps a 4-acre barn filled with wood chips, sourced locally from forestry waste and old pallets. The barn can hold a three- to four-week supply of wood chips

February 18, 2016

Metrolina Greenhouses Has Improved Heating Efficiency W…

Sustainability started to become a keyword in the horticulture industry in the late 2000s, when growers began converting their heating systems to greener options to save on energy costs and reduce their impact on the environment. However, there haven’t been many operations that have invested in sustainable solutions on as large of a scale as Metrolina Greenhouses at its Huntersville, NC, headquarters. Six years later, the operation is still fully committed to its biomass heating system and everything it entails.     Metrolina first fired up its Vynke biomass system from Belgium in 2010. The four wood boilers cover 95% of the operation’s heating needs at its 201-acre main location in Huntersville, NC, and Metrolina still maintains its traditional heating systems for back up and to provide flexibility of resources. Wood chips are sourced locally, with the majority from local forestry activities like wood harvesting companies and developers. The other […]

Read More
Stuppy Greenhouse Manufacturing's Rainbow Super Structure

December 21, 2015

Three Strategies For Overcoming Greenhouse Heating Conc…

Lost heat, maintaining an ideal greenhouse temperature, and inefficiency in heating systems are three of the most common problems growers face when it comes to heating. Here’s a look at some ways to overcome these challenges.

Read More
Heating Roundup Feature Image

August 1, 2015

5 New Heating Options For The Greenhouse

Five heating systems manufacturers share their latest and greatest products. Tubing And Aluminum Heat Pipes (BioTherm) From Megatube and MicroClimate tubing to DuoFin and StarFin aluminum heat pipe, BioTherm is dedicated to providing heat solutions that can withstand the toughest greenhouse environments. The MegaTube and MicroClimate tubing options are easy to install and ideal for bench or floor heating. The tubing has a conductive heating surface that allows for maximum root-zone heating. The DuoFin and StarFin aluminum pipe options are great for perimeter heating and melting snow trapped in the greenhouse gutter. It can also be useful for bench heating. Both pipe options provide gentle, radiant heat for plants and don’t require welding. Infinite Energy 2 Condensing Boiler (Delta T Solutions) With up to 98 percent efficiency, the IE2 condensing boiler boasts a stainless steel heat exchanger with larger waterways to ensure maximum heat transfer. The product’s design ensures flexibility while […]

Read More
Heating Feature image

July 27, 2015

In Hot Pursuit Of Heating Trends For The Greenhouse

From biomass boilers to hydronic-heating systems, growers have a range of options to fit their operation’s unique needs. Here’s what five manufacturers had to say about the latest trends.

Read More

June 23, 2015

Schaefer Ventilation Opens Distribution Center In Atlan…

Schaefer Ventilation Equipment, a manufacturer of ventilation and thermal comfort products, has opened a new distribution center in Atlanta, Ga., to increase efficiency and provide faster services to dealers. Additionally, the company has added a new staff member to its agricultural and horticultural division to help expand markets in Latin America.

Read More
Michigan State University Extension

February 24, 2015

Ethylene From Defective Greenhouse Heaters Damages Crop…

Malfunctioning greenhouse heaters can lead to crop damage from ethylene and carbon monoxide induced illness for workers. Michigan State University's Extension educators Tom Dudek and Randy Beaudry teach you how to recognize the symptoms and check greenhouse heaters to avoid the concern.

Read More

June 27, 2014

4 New Products For Cooling, Shading And Ventilation

The Vertex by Poly-Tex The Vertex is the newest member of the Greenhouse Megastore’s shade structure family. Make a statement and show your colors with this simple, stylish shade house.The easy-snap button frame and bungee-shade attachments will provide  shade in no time. With  more than 7 feet of sidewall clearance and 13 feet to the peak, the Vertex will give shade while keeping that open-air feeling.  

Read More

June 5, 2013

Natural Ventilation And Fog Increase Cooling Efficiency

For greenhouse ventilation, two main methods are used — mechanical and natural. Mechanical ventilation includes fan-and-pad systems, which are a type of evaporative cooling system. Fan-and-pad systems cool air by passing outside air through a wet pad, lowering the temperature and humidifying the greenhouse. This type of system works best in hotter, drier climates, because the capacity for cooling with a fan-and-pad system is very limited in humid climates. University of Arizona associate professor Murat Kacira says a drawback of using a fan-and-pad type system is that it requires a lot of energy and water. “Water is needed for the pad system, and energy is needed to run the pump for water circulation over the pad as well as the energy to run the exhaust fans,” Kacira says. “Water is a precious resource with limited availability, especially in arid and semi-arid regions. “Another issue is there can be a temperature […]

Read More