What is the HAF principle?
How many CFm is a greenhouse fan?
What size blades are available for HAF fans?
Why is HAF important in greenhouses?
How much does a 30x100 greenhouse weigh?
How far apart should a fan be from the endwall?
When did HAF start?
See 4 more
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Grower 101: Horizontal Air Flow - Greenhouse Product News
Since 1967 when Jay Koths, University of Connecticut floriculture specialist emeritus, introduced horizontal air flow (HAF), the concept has become the standard method for air circulation in greenhouses. Over the years improvements to fan design, installation techniques and efficiency have made the system a valuable tool that helps growers produce better quality plants. HAF is […]
Greenhouse Air Flow - vCalc
The Greenhouse Airflow Calculator computes common airflow metrics for a greenhouse (see below).
What is the goal of air distribution in greenhouses?
The true goal of any air distribution system in the greenhouse, Becker says, should be to homogenize the air, as plants can transpire more evenly and efficiently when the microclimate around the plant is removed. Here, Becker outlines four strategies for proper air flow.
Why is momentum important in greenhouse air flow?
Because of this, momentum is replacing velocity as the desired result in greenhouse air flow systems. The aim is to generate a stable mass of air that slowly builds momentum as it travels through the greenhouse. “The momentum of air may take a while to get established, but it doesn’t stop moving for a while,” Becker says.
What is the goal of momentum in greenhouses?
The goal of a momentum-based system is to create a stable mass of air that slowly builds momentum as it travels through the greenhouse. Photo from The Dramm Corporation.
What is a dramm whitepaper?
Dramm has produced a number of whitepapers discussing topics related to its primary businesses, including one on momentum-based air flow for optimal plant growth. The whitepapers are available for free download and offer information to growers to help them make informed decisions. Learn more at Dramm.com/whitepapers.
Why are vertical fans important?
These fans can homogenize the air vertically, removing temperature stratification from top to bottom. Vertical fans can also create movement at the crop level, helping with transpiration and the elimination of microclimates near the plants.
What is the problem with parallel layout?
The problem with the parallel layout, Becker notes, is that it is based on the greenhouse structures all being the same size, and on flat land. “Here in the U.S., we have more hills than they do in Holland, where the parallel system was developed,” he says.
How do shroud fans work?
Shrouded fans in a series work together to carry the air in a forward direction, reducing the energy required, and creating a more even, stable air flow. Additionally, the use of shrouds creates an intake, as well as an exhaust, something that unshrouded fans don’t have, Becker says.
How long does it take to grow a greenhouse?
It can take a year or two of gardening through the seasons to perfect your greenhouse air, light, and climate management skills. However, once you do, you’ll truly understand William Cowper’s quote “Who loves a garden loves a greenhouse too.”.
What plants grow well in greenhouse light?
For example, vanilla, black pepper, cardamom, galangal, ginger, coffee, tea, and turmeric all grow well in greenhouse light on both the north and south sides of the space. I also grow a few citrus plants like Meyer Lemon, Kaffir lime, Calamondin Orange, Key Lime, and others that prefer full sun.
How cold should a greenhouse be?
At night and on shady days, depending on materials used, a greenhouse will only offer you about 5-10°F of cold protection compared to outside temperatures. That means if it’s 8°F outside, your greenhouse will still be well below the 24°F threshold considered detrimental to many plants.
What fuels do heat pumps run on?
Heaters that run on a fuel source such as propane, natural gas, kerosene, or paraffin are more economical to operate. Still, they require a constant turnover of fresh air to prevent toxic gas accumulations. Otherwise, plants may not flower and will likely grow slower.
Why do we grow in greenhouses?
Now let’s talk about the climate inside of a greenhouse. One of the main reasons to grow in a greenhouse rather than in a garden is to provide more warmth in winter. However, gardening in a greenhouse doesn’t automatically guarantee the right climate.
How much light does a greenhouse lose?
The exact amount of light lost as it passes through the coverings varies by material. In general, though, the loss of light rays is somewhere between 20-50%.
What do plants need to survive in a greenhouse?
3. Plants Need “Air”. People often say that plants take in carbon dioxide and release oxygen when talking about photosynthesis.
Why hang ceiling fans?
Hanging ceiling fans will help circulate warm air above with the cooler air below and provide consistent air movement inside the dome. If you have regular fans, we encourage you to point them perpendicular to the intake fans, to create a circular air movement around the dome.
How to maintain humidity in dome?
Regular ventilation and moving air is the best way to stabilize humidity levels and support plant health. Ventilating and air movement whenever possible, even through the winter, will be the key to healthy year-round gardening in your dome.
What is the immune system dependent on?
Air Movement and Circulation. Our immune function is dependent on a kind of experience in fighting off invaders, our muscles are dependent upon exercise to increase their strength, and so forth. Plants are the same.
Why does photosynthesis occur during the day?
While during the day, photosynthesis causes plants to absorb carbon dioxide and produce oxygen. In general, there will be less photosynthesis happening in the winter and less respiration happening in the summer.
Why do my plants' leaves get leggy?
If the air ruffles your plants’ leaves, the plants are forced to develop a sturdy structure, therefore reinforcing them against disease and weakness. Often plants who don’t experience adversity get leggy and spindly in greenhouse environments as they reach for the light in darker winter months or stormy summer months.
Why do greenhouses need ventilation?
Greenhouse ventilation helps prevent fungal infections and provides plants with the fresh air they need to respirate, photosynthesize and grow strong. It also aids in regulating temperature and humidity levels.
How do fungi spread?
They spread through spores in the air. These spores are usually concentrated in tiny quantities and proliferate quickly when given the optimal growing conditions of wet, warm, protected spaces like your greenhouse. Funguses are essentially nature’s air-born decomposers.
What is the HAF principle?
The HAF concept utilizes the principle that air that moves in a coherent horizontal pattern in a building like a greenhouse needs only enough energy to overcome turbulence and friction loss to keep it moving. In other words, you just have to “kick it along.”. Air is heavy.
Why do tomato greenhouses have air flow fans?
Horizontal air flow fans in a tomato greenhouse are mounted above the cross braces so they can still move air once the crop has attained its full height. Photo: Vern Grubinger, University of Vermont Extension
What are the common errors in greenhouse fans?
However, common installation errors include too little fan capacity, poor spacing and location of the fans and poor maintenance. Many systems could be improved with just a little work.
How far apart should a fan be from a greenhouse?
The first fan should be placed about 10′ to 15′ from one end wall to pick up the air that is coming around the corner from the other side. Subsequent fans should be located 40′ to 50′ apart to keep the air mass moving. Photo: Vern Grubinger, University of Vermont Extension
What size blades are available for HAF fans?
HAF fans are available with 12″, 16″, 18″ and 20″ diameter blades. Fan output and efficiency increase with increase in blade diameter. Guard design also affects output.
How much difference in temperature between greenhouses?
Before Horizontal Air Flow (HAF) systems were developed, it was common to find 10°F to 15°F difference in nighttime temperature between the opposite ends of a greenhouse. Plant growth and quality often reflected this unevenness. Today with a properly installed HAF system, there should be no more than 2°F difference anywhere in the greenhouse.
How much air does a greenhouse hold?
Air is heavy. The air over every square foot of floor area in a greenhouse weighs about one pound. A 30′ x 100′ greenhouse contains about 1-1/2 tons of air. Once the air is moving, it will coast along like a car on a level road. This is why HAF is so efficient. It takes only four small fans to keep the air moving at 50 to 100 feet per minute in the above greenhouse.
What Tools Do You Need to Start a Vegetable Garden?
Any beginner gardener can get easily overwhelmed by the variety of gardening tools available. Don’t let this confusion keep you from growing a thriving edible garden of your own, especially when there are a lot of references online that can help you out.
Can I Build a Man Cave In My Garden?
Given that you have enough space in your garden or don’ t mind altering the said space to suit your relaxation needs, then the only answer to this is a resounding yes. Among the fresh ideas for relaxing and hanging out at home is to do it in your very own man cave.
Why Should You Invest in Steel Doors?
As soon as we hear steel doors, we think of prisons or a cage though that may not be the case. Today we will learn about the essential elements of steel doors in everyday living. You would be surprised how far their use has come along.
How Much Does Tree Removal Cost?
Trees are essential assets to properties, adding beauty and shade while stopping soil erosion. However, when a tree becomes a liability, it must be removed. When a tree is damaged, dead, leaning, or too near to your house, a tree removal service can dispose of it for you.
Why Do We Need Outdoor Furniture?
Why do we need outdoor furniture? There are many reasons, and the great news is that there are some attractive and affordable furniture options for your yard, garden or even a balcony! You don’t have to have a large space to enjoy your outdoors, and as we will show you it’s good for you ! Where to start looking at outdoor furniture?
Does Landscaping Increase Property Value?
If you have been wondering, does landscaping increase property value, then you will find this article to be extremely insightful. The truth of the matter is that landscaping that is done in the right manner does indeed increase the value of your property. That is why we share in-depth some amazing ways that landscaping can increase the value of your property. We’ve written this article with the help of a landscaping company called RocDog, which says a lot of clients are property developers wishing to increase the price of their property.
What Are Some of the Best Eco-Friendly Apps that can Help You Go Green?
However, it can be difficult to make some of the major changes that come with going green and focusing on sustainability , even if you believe in the cause.
The Importance of Greenhouse Ventilation
Learning to use a greenhouse is a process of trial and error. It helps to understand the reasoning behind why ventilation is so crucial to success with growing inside a greenhouse.
Does a Small Greenhouse Need Ventilation?
It is easy to assume that only big greenhouses need ventilation – is it really necessary to put a fan into your cupboard-sized greenhouse? The answer is always yes.
Manual versus Electric Ventilation
Manual ventilation refers to vents at the top and the base of the greenhouse walls that you have to open in the morning and close in the evening. The vents create a cross-breeze due to natural convection.
Types of Greenhouse Fans
There is a wide range of fans on the market, ranging from low-tech to high-tech. The basic types are:
Ventilating a Greenhouse Without a Fan
It is perfectly okay to choose the natural, low-tech way to ventilate your greenhouse. You may be looking to minimize the cost of setting up your greenhouse or are put off by the idea of adding to your electrical bill.
Advantages & Disadvantages of Using a Fan in the Greenhouse
If you are still in two minds about whether or not to use a fan in your greenhouse, let us look at some of the advantages and disadvantages:
Conclusion
Ventilation is one of the fundamental factors to consider when building a greenhouse. Regardless of the size of the greenhouse, adequate ventilation is always necessary.
What is the HAF principle?
The HAF concept utilizes the principle that air that moves in a coherent horizontal pattern in a building like a greenhouse needs only enough energy to overcome turbulence and friction loss to keep it moving. In other words, you just have to "kick it along.". Air is heavy.
How many CFm is a greenhouse fan?
For an efficient system, the total fan capacity should be about two times the floor area. For example, in a 30' x 100' greenhouse, the fan capacity should be 30' x 100' x 2 = 6000 cfm. If a tall crop such as tomatoes are grown or if there are hanging baskets, a slightly greater capacity is needed to overcome the additional turbulence created.
What size blades are available for HAF fans?
HAF fans are available with 12", 16", 18" and 20" diameter blades. Fan output and efficiency increase with increase in blade diameter. Guard design also affects output.
Why is HAF important in greenhouses?
Besides the obvious advantage of more uniform temperature within the greenhouse, HAF systems can reduce the incidence of foliar diseases. The moving air removes moisture from the plant canopy resulting in a drier microclimate. When leaf temperatures are allowed to cool much below the air temperature, the dew point is reached ...
How much does a 30x100 greenhouse weigh?
Air is heavy. The air over every square foot of floor area in a greenhouse weighs about one pound. A 30' x 100' greenhouse contains about 1-1/2 tons. Once the air is moving, it will coast along like a car on a level road. This is why HAF is so efficient.
How far apart should a fan be from the endwall?
Fan location is also important. The first fan should be placed about 10' to 15' from one endwall to pickup the air that is coming around the corner from the other side. Subsequent fans should be located 40' to 50' apart to keep the air mass moving.
When did HAF start?
In the early 1970's when Dr. Jay Koths, Emeritus Professor of Floriculture at the University of Connecticut introduced the HAF system to the greenhouse industry, it was difficult to find a good circulating fan. Most fans had to be assembled selecting a motor, fan blade and guard from a catalog.
Series Layout vs. Parallel Layout
Shrouded Fans vs. Basket Fans
- The livestock producer Becker observed was using basket fans, which throw air in a much wider pattern, often impacting the crop below with varying direction and speed, and reducing uniformity. These wider patterns minimize forward momentum, as the air from the first fan in a series often conflicts with the air from the second fan, as the direction is non-linear. This results in uneven ai…
Speed-Based Air Flow vs. Momentum-Based Air Flow
- As recently as a few years ago, horizontal air flow (HAF) was thought of solely in terms of velocity. However, when the air in a greenhouse is being moved internally, velocity can be very hard to measure. In fact, bursts of erratic speed can cause instability in temperature and climate that can affect plant growth. “A common misconception is that p...
Horizontal vs. Vertical Air Flow
- Interest in vertical fans has increased a great deal in recent years. These fans can homogenize the air vertically, removing temperature stratification from top to bottom. Vertical fans can also create movement at the crop level, helping with transpiration and the elimination of microclimates near the plants. However, the main problem with vertical fans in plant growth is the same as wit…
A Chance to Learn More
- Dramm has produced a number of whitepapers discussing topics related to its primary businesses, including one on momentum-based air flow for optimal plant growth. The whitepapers are available for free download and offer information to growers to help them make informed decisions. Learn more at Dramm.com/whitepapers.