# How do you calculate the volume of a greenhouse to be evacuated by a vent fan?

## How do you calculate the volume of a greenhouse to be evacuated by a vent fan?

The exhaust fan should change the air in the greenhouse in 1-1/2 minutes. Fan capacity is rated in Cubic Feet per Minute (CFM). For your correct fan size in CFM, calculate your greenhouse Volume: Length x Width x Average Height = Volume.

## What is a HAF fan?

Horizontal Air Flow (HAF) fans and their sisters (HVF) High Velocity Fans are essential parts of a greenhouse heating and cooling system. HAF Fans and HVF Fans are also known as circulating fans. Circulating fans increase airflow throughout the greenhouse.

Do greenhouses need air flow?

Yes, greenhouses need ventilation. Ventilation is actually one of the most important parts of a greenhouse. Here are the main things a ventilation system does to keep plants healthy. Now that you know greenhouse ventilation is important for healthy plant growth.

Where should a greenhouse fan be placed?

The fans should be located near the center of the air mass to which they are adding energy. For greenhouses with floor or bench crops, a location 7′ or 8′ above the floor is good. In many greenhouses there is a truss or collar tie that can be used for support.

### Where should a circulation fan be placed?

Place your fan so that it faces the opposite wall from where most of the activity takes place in your space. This approach will drive the air to the surface, where it will bounce off, mingling with the rest of the air and cooling the space.

### Is it better to point a fan in or out?

From a purely temperature point of view, not human perceived level of hotness, it is better to point the fan outward. This is because the fan motor will dissipate some heat, and when the air is blown outwards, this heat goes outside. If the point is to make you in the room feel cooler, blow the air in.

Should fan face the window?

Real Simple notes that a fan blowing air out of your room is better than one blowing in. When your fan is facing out the window, it blows hot air out of the room, which his replaced by cold air from outside. It’s best if you have another window to open elsewhere so you can get a cross draft going too.

Why is only my room so hot?

First, check for these common problems: Dirty air filter—A dirty filter restricts airflow, not letting your home get enough cool air. Closed vents—Closed vents in rooms can cause them to be hotter than other rooms. Air duct issues—If you have any kinked or crushed supply ducts, certain rooms won’t get enough air.

## How is greenhouse ventilation calculated?

CFMs are the total cubic feet of air that should be exchanged every minute with mechanical ventilation. If you have a 15′ Catamount style greenhouse, take the length and width (15′) and multiply by 5 to get your total CFMs. Ex: A 15′ × 96′ greenhouse will be 15 × 96 × 5 = 7,200 CFMs per minute of air flow.