A greenhouse is a structure that protects plants from the elements. It can be made out of any material, but there are two main types: glass and aluminum. Glass greenhouses are more expensive than aluminum ones, but they also have more benefits. For example, because glass is transparent it will allow in light which helps grow your plants faster. Glass is often preferred because it can provide better insulation than aluminum which means that plants inside a greenhouse need less energy for heating or cooling. It can also be reflective so it doesn't absorb heat from the sun like other types of material may do. The price difference varies depending on size and complexity of your project. Aluminum has several benefits including being durable and lightweight which makes installation easier.