Ventilation is achieved with a combination of roof vents, louvre vents, doors and fans. Excellent ventilation is essential if your plants are to thrive and your room is to be comfortable for you. Ventilation controls both the temperature and humidity of the air in a room - both of which are essential factors when it comes to healthy plant growth. Basically you need cool air to be drawn into the conservatory and hot air to be driven out. This can be achieved by the installation of sufficient vents - such as louvre vents and roof vents - ideally fitted with automatic openers, together with the use of greenhouse fans. If you intend to grow in your room all year round then consider fitting an extractor fan in the wall. Extractor fans are designed to completely replace the air in a room every few minutes even on the hottest days. Attached to a thermostat, the fan will run automatically. Remember that it is always better to over ventilate your room than under ventilate it.