Should you add a retail greenhouse?

Consider providing a comfortable and safe shopping facility that meets local building codes and regulations.

By Amy Rigazio

Greenhouses have become popular structures for displaying and selling plant material to consumers. In the past, many growers sold plant material to the public from roadside stands and farmer’s markets. Today, more growers are bringing customers either directly into their production facilities or into separate retail greenhouses. This transition into retail sales is often advantageous for growers in terms of returns, but some consideration must be made to the new function of the structure.

Classification
Once a greenhouse building is used for more than plant production, its legal classification changes from an agricultural to a commercial building. While some existing greenhouses may be grandfathered, most new greenhouses constructed for retail plant sales require mercantile occupancy permits, which greatly changes the structural, fire and accessibility requirements of the building.

As an agricultural building, a greenhouse has an unlimited allowable area as long as it is surrounded by public ways at least 60 feet wide. This allows growers to build gutter-connected ranges that have been specifically designed to provide large, single-environment enclosures.

A mercantile building has a limited allowable area based on the type of construction. The allowable area is usually more than sufficient for a separate retail-only building, but may not be sufficient for a multi-use building -- a grower who wishes to use the building for both production and retail sales. As the rules for retail sales are more stringent than for commercial growing, the entire facility would need to meet the more rigorous codes.
Growers who choose to enter into the retail market should learn as much about their potential customer base as possible. This will help ensure that the house is designed to promote a comfortable shopping environment.

Considerations
Take many factors into consideration before purchasing a greenhouse for retail sales use. Contact building officials of the town in which the structure will be constructed to determine the governing building codes and type of permits required. This information will be vital in allowing the greenhouse manufacturer to design and fabricate the facility to meet all required specifications.

Building size. As with all non-agricultural buildings, the number of people allowed into a facility is determined by square footage. This occupancy load is then used in the building design. The number of, size of and location of exits, as well as aisle widths and lengths are all designed based upon the occupancy load. Exit and aisle design will also be influenced by wheelchair accessibility regulations. Bench heights and widths may also need to comply with accessibility rules in towns that view them as sales and service counters.

Fire prevention. Fire prevention systems, such as alarms and sprinkler systems, are often required in retail greenhouses. A structure’s glazing material often falls under the jurisdiction of fire codes as well. Although codes differ on the specific rules concerning the use of light-transmitting plastics on retail houses, most do discuss the subject.
Some codes limit the amount of material allowed on the roof and walls as a percentage of the total area. Others only allow for the material to be used in conjunction with an overhead sprinkler system. It is vital that the local fire codes be obtained before purchasing a greenhouse for retail use. Burn rates and flammability data of agricultural plastics are offered by many plastics manufacturers. This information is often required by the local building or fire inspector for review.

Opening a retail greenhouse business is as involved as starting any business. The operator must either be willing to do the required research into local zoning laws and permitting regulations or else hire an architectural or engineering firm. Most greenhouse manufacturers are more than willing to help potential clients determine what will be required, but they usually rely on the customer to make the final decision.

Designs
Once all of the local codes have been determined and the applicable permits obtained, personal preferences can take over. The greenhouse manufacturer works with clients to design a layout to meet specific needs and desires within the legal confines of the prevailing code body. For example, while aisle widths are influenced by occupancy load and accessibility rules as stated above, there are many different ways in which the interior can be laid out to meet all of the regulations. Each layout will give a different appearance and feel to the facility.

There are many different philosophies about how to best display and sell plant products. Garden centers often combine finished plant material with plant accessories, such as decorative pots, baskets and potting mixes. When consumers are encouraged to purchase these additional products, wider aisles are needed for shopping carts.
Wider aisles also make display space look more open and clean, which appeals to many higher-end retailers. If plants and accessories are easily accessible, customers are more likely to pick them up than if they had to maneuver down narrow aisles that look cluttered.

The reverse thinking is to keep aisles as narrow as possible so that the maximum number of plants can be displayed. The idea here is to fill the house with plants and offer a wide variety. A greenhouse full of plants makes a spectacular display, as long as it is not difficult for customers to find what they are looking for.

Some owners believe that if customers have to walk through a few aisles to find what they initially want, they are more likely to pick something else up during their search. Narrow aisles that are difficult to maneuver or make handling and carrying plants too cumbersome may be counterproductive. Customers may walk away without buying anything if they become frustrated.

Ventilation
An important aspect of any greenhouse project is the design of the ventilation system. When a facility is used for retail sales, design of the ventilation system is critical. As with all greenhouses, temperature control is vital to the health of the plants. In retail greenhouses one must also take the customers’ comfort into consideration.
Passive ventilation through roof and wall vents is often considered ideal for retail houses. The lack of exhaust fans reduces the noise within the shopping environment and prevents the strong wind currents associated with fans. Many retailers are starting to use open-roof greenhouses as well for passive ventilation systems.

It is vital that a weather monitoring system be used with open-roof houses so that the roof sections can be closed during strong winds and rain. Without a monitoring system, fast-moving storms can blow in and rain on customers before an employee has time to manually close the roof vents.

Growers constructing multi-use buildings for both retail sales and production may choose to use forced ventilation systems with exhaust fans. In this scenario it is important that the fans be properly sized for the application. The grower may wish to consider installing more fans and larger inlets to move more air through the facility than would be typical for a production-only greenhouse. The additional airflow will help maintain lower temperatures and keep customers comfortable.

A series of roof vents as an additional stage of ventilation would be beneficial on days when the inside temperature is only slightly higher than the set point. These vents can be used with the existing inlets and allow a certain amount of heat to be exhausted before exhaust fans are required. Not only does this reduce noise within the facility, but saves electricity on days when the fans are constantly cycling on and off.