Greenhouse Guide

A Guide to Greenhouses

Before any information can be given regarding greenhouses, the term greenhouse must be defined. Most people will be aware of what they are and how they work, but for those who do not know, they are defined as a special structure that is designed for growing plants all year round. Contrary to the name, greenhouses are not literally houses that are green, but instead are clear in appearance as they use glass as the primary material. The glass used magnifies heat, which in turn creates more favourable conditions for the plants inside this structure. A greenhouse is something that anybody who has more than a passing interest in gardening must own.

If you still aren’t convinced, then take a look at some of the advantages that a greenhouse provides:

  • Consistency – the ability to have access to the same weather conditions all year round
  • Protection – from harsh weather conditions, which is especially useful in the UK
  • Easy Customisations – greenhouses can be made to unique specifications
  • Save Money – a great deal of money can be saved because of reduced food bills if you decide to grow your own vegetables
  • Increased Output – having a greenhouse will allow you to take your gardening to the next level

These advantages are just some of many, as there are countless reasons why a greenhouse should be considered. Unfortunately, choosing a greenhouse may not be as easy as it seems. It is a big investment with a number of long term implications, making it a particularly important choice. Here are some points that people often overlook that can cause an issue:

A green house being carefully built

A green house being carefully built

• Size - choosing a greenhouse that is the right size for your garden is essential. If it’s too big, it will dominate your gardens appearance, but if it’s too small, it probably won’t be sufficient for your needs. The type of plants that you intend to grow in there will also affect the size you choose, growing sunflowers in a smaller space is never ideal for a number of reasons.
• Material - although greenhouses are predominantly made of glass, the material that the structure is made of can also have a big impact. As a greenhouse will become a feature of your property, it’s essential to choose one that matches your home.
• Glazing - not all greenhouses are made equal. Different types of glazing will affect your plants, while durability, costs, and maintenance are a few factors that need to be considered for the long term. As a general rule of thumb, plastic glazing is less efficient when it comes to transferring heat, but it is often cheaper and more resistant.
Now that a brief overview has been provided, it’s time to analyse these factors in further detail. The first point you will need to consider is the size and the positioning of your greenhouse.


As already mentioned the size of your greenhouse will have an impact on the appearance of your garden. If it’s too big, it will make your garden seem crammed, but if it’s too small, it will limit what you can grow. The positioning of your greenhouse will also have an effect the size. Positioning it in an area that allows for a reasonable amount of natural light is a priority, and ideally the longest side of the greenhouse should be facing south. If your greenhouse is square shaped, this rule doesn’t have to be enforced so rigidly. However, it is always a good idea to ensure that the entrance is facing north (regardless of the layout), as this will prevent cold air from entering the structure and damaging the plants.

Greenhouses come in all shapes and sizes to suit you.

Greenhouses come in all shapes and sizes to suit you.

If possible, it’s also beneficial to place your greenhouse in an area that is well sheltered. A location that is either surrounded by walls or fencing is ideal, but you should be wary of excessive shading. Greenhouses that are primarily made of glass and not transparent plastics are more susceptible to damage from natural debris. By placing glass greenhouses in protected areas that do not stop light entering, this type of damaged can be prevented.

Frame Material

While the primary material of a greenhouse is usually glass, the frame itself will generally be either wood or aluminium. Wooden frames always compliment gardens, whereas some less common choices (PVC) can actually take away from the appeal of the garden. In terms of practicality and function, wooden framed greenhouses are generally warmer all year round, while further insulating materials such as bubble wrap can easily be stapled to the inside of the structure if you feel this is required.

Aluminium greenhouses, on the other hand, are arguably less attractive, but they offer more in terms of durability and are likely to be cheaper. In addition, the structure of aluminium frames tend to be thinner, which in turn allows more light to enter the greenhouse, which is obviously a big benefit.

Wooden frames will need to be treated with protective lacquer every few years, while aluminium frames typically come with a 10-20 year guarantee. Some will say that wooden frames do not last, but if they are treated properly, then they can actually last longer than 20 years.

A greenhouse can be a great place in which to contemplate life.

A greenhouse can be a great place in which to contemplate life.

Glazing Options

This is another material option that also needs to be considered, and typically, there are two choices; glass or polycarbonate. Glass transmits 90% of the light that hits it, and it will not degrade over time, but it can be quite brittle. Polycarbonate, on the other hand, transmits 83% of light, is tougher, and is better at retaining the heat. However, it is generally considered much harder to clean.

In terms of price, glass is more expensive, but it is a tried and tested option that gardeners have been using for years. If strength is of primary concern, then toughened glass can be used, but this will be more expensive.

As a third glazing option, acrylic plastic can be used, and it transmits 85% of light, which is only 5% less than glass. However, due to its poor levels of durability, polycarbonate is seen as a better option.

Other Considerations

So far, the main factors associated with choosing the right greenhouse have been looked at; the size, the positioning, the frame material, the glazing material and the reasons why a greenhouse should be purchased. However, for optimal greenhouse performance, there are further considerations that need to be explored:

A greenhouse does not necessarily need to be made of glass.

A greenhouse does not necessarily need to be made of glass.

Ventilation - like all living things, a good source of oxygen is vital for growth and survival, and plants are no different. Ideally, roof openings should be diagonal, and there should be at least 15-20% or space available on the floor. For perfect levels of ventilation, automatic opening windows are a good choice, but they are quite expensive.

Heat - different plants require varying levels of heat, but as the UK is generally quite cold insulating materials may be required. To keep a constant gauge of the temperature, a thermometer is a handy purchase, while green house heaters can ensure warmth in even the coldest of conditions.