Glazing is important for a greenhouse as it helps to retain heat – the main principle of growing inside a greenhouse – and also helps allow sufficient light to pass through for photosynethesis and photomorphogensis. Greenhouses use different materials for glazing and some of them have double glazing.
Now if you’re wondering whether double glazing has any benefits, and can you use double glazing for your greenhouse without any adverse effect, the answer is pretty simple.
Yes, you can definitely use double glazing for your greenhouse. It offers the most important benefit of better heat retention and compared to single glazing, much more preferable in colder climates.
Why you Should Use Double Glazing for your Greenhouse
See the main purpose of growing inside a greenhouse is that you can grow stuff throughout the year. A greenhouse is built in such a way that it maintains appropriate growing conditions even in extreme climatic conditions. So you can grow plants that grow in warmer temperatures even in winter.
While the temperature inside the greenhouse can be increased with the help of heaters, in may cases you don’t require heaters if you have used the right glazing. Single glazing is good enough when temperatures do not fall drastically. However, in severe cold conditions, double glazing helps to retain more heat inside the structure.
The cost of heating the greenhouse is significantly reduced when the greenhouse is double glazed. For example, for glass double glazing, the cost of heating is reduced by as much as 40%. This is because the glass double glazing significantly reduces heat loss in winter.
As double glazing helps the greenhouse retain more heat received during the day, it helps to prevent moisture condensation on the walls of the greenhouse. As a result, there is not much effect on the light transmission within the greenhouse during the day.
Now if you feel that double glazing can be detrimental in hotter climates, I don’t blame you. We have discussed how double glazing can help prevent heat loss during the winter. However, during the summer months, it helps to reduce the heat entering the greenhouse.
For example, if you have a glass glazing, during the summer when the sun is pretty harsh, the light received is direct and can even burn some fragile plants, which normally do not grow in summer. However, double glazing will help reduce the heat transmitted and can thus protect the heat-sensitive plants.
Types of Double Glazing
Double Glass Glazing
Most of the greenhouses even today use glass glazing. It is more prevalent as it is easily available and has been used for a long time. Double glass glazing has an equally good light transmission and retains heat well during the winter months.
However, you need to ensure that moisture and air do not get accumulated in between two welded glass panes, as it can impair the transmission of light during the day. Also, you need to be more careful because glass is easily breakable and hence must make extra arrangements to ensure that the greenhouse is in a safe location.
Double-pane glass with interior coatings, a plastic interlayer, or gas filling — although fine for a sunspace where glare, heat gain, and furniture fading are concerns — usually reduce light transmittance to levels too low to get good plant growth in the winter. So avoid coating the inner glass pane with any material.
Double Polycarbonate Glazing
Polycarbonate glazing has started being used more recently. It is lighter and hence double glazing requires less structural support as compared to double glass glazing. It is also stronger than glass and retains heat better than glass. As it transmits diffused light, it greatly reduces the risk of burning the plants and damaging them during the hotter summer days.
However, though single layer – corrugated – polycarbonate glazing is nearly perfect, double layer polycarbonate glazing reduces the transmission of light to some extent – it is definitely less than that of double pane glass. Polycarbonate material is also more prone to condensation, as with other forms of plastics.
Double Plastic Film Glazing
There have been recent improvements in flexible film plastic glazing such as clarity, strength, and heat retention. However, even though they are cheaper than rigid plastic glazing, they are not used to that extent in most home greenhouses, mainly because of their shorter life span.
Only when the greenhouse is really small, more of a mini structure to test the greenhouse growing principle, to grow 1 or 2 plants, it is a better idea to use plastic film glazing. Or in the case of commercial greenhouses where the cost of glass or rigid plastic can be a lot.
Some Steps to be Taken to Ensure Effective Double Glazing
If you’re using glass double glazing, it can significantly increase the weight load on the frame of the greenhouse. Most greenhouse frames are designed to hold a single glass glazing. Their holding capacity is ideally suited for single glazing.
Hence, ensure that you make some necessary modifications in the framing structure to enable the greenhouse to carry the weight of the double glazing. One way is to have partial brick walls. You can add bricks as reinforcements to the already existing structure.
If you’re still in the planning phase, you can have brick walls halfway followed up with glass or any other material you choose.
Another thing you must keep in mind is that though the double glazing reflects some of the extra heat during the hotter months, because of the high temperature outside, you need to have adequate ventilation within. You can have open windows, however a better option is to install exhaust fans which will help to eliminate the excess heat from within the greenhouse.
Look, a double glazing can definitely help the greenhouse retain heat in severe cold weather. However in some cases, you don’t really need the double glazing. If you live in a place with moderate temperature, and winters are not very harsh, you don’t really require double glazing. A single glazing will be enough to give you all the benefits of growing in a greenhouse.