Quick Answer:
Quick Answer:
BC Greenhouse Builders recommends installing a UV-stabilized shade cloth over your greenhouse in late spring to manage summer heat:
- Choose 60% shade cloth for polycarbonate greenhouses and 70% for glass structures
- Apply the cloth seasonally once daytime temperatures are consistently hot (typically May or June)
- Cover the roof lengthwise, pulling about two-thirds over the south side and one-third to the north
- Select a cloth with grommets every two feet for secure tie-downs that resist wind
- Remove the shade cloth in fall (around mid-September) to maximize low-light growing season
- Use UV-stabilized fabric so the cloth lasts several years without degrading
- What Are the Benefits of Shade Cloth for Your Greenhouse?
- What Shade Percentage Should You Choose for Your Greenhouse Type?
- When Should You Install and Remove Shade Cloth?
- How Do You Apply Shade Cloth to a Greenhouse?
- What Size and Features Should You Look For in Shade Cloth?
- Can Shade Cloth Be Left On Year-Round?
- Can Tree Cover Replace Shade Cloth?
If you have ever walked into your greenhouse on a hot summer afternoon only to find scorched leaves, wilted lettuce, and bone-dry soil, you are not alone. BC Greenhouse Builders hears from customers who struggle with overheating every summer, especially those growing in polycarbonate or glass structures. The good news is that a simple shade cloth installation can transform your greenhouse from a sweltering box into the coolest, most comfortable spot in your garden.
What Are the Benefits of Shade Cloth for Your Greenhouse?
Shade cloth reduces heat buildup inside your greenhouse, which leads to healthier plants, lower pest populations, and a more enjoyable space for you to spend time in. BC Greenhouse Builders customers report that adding shade cloth to their greenhouse dramatically changed the growing environment, turning a space plagued by scorched leaves and bolting lettuce into a cool retreat, even during heatwaves.
Beyond temperature control, shade cloth delivers several practical benefits:
- Reduced watering frequency: Less direct sun means soil stays moist longer, saving you from watering morning and night during peak summer
- Lower pest pressure: Cooler temperatures inside the greenhouse keep pest populations down naturally
- Healthier plant growth: Plants avoid heat stress, sunburn, and premature bolting
- Energy savings: Less need for cooling fans and electricity to manage temperatures
- Personal comfort: Your greenhouse becomes a pleasant sitting area instead of an oven
What Shade Percentage Should You Choose for Your Greenhouse Type?
The right shade percentage depends on your greenhouse glazing material. BC Greenhouse Builders recommends 70% shade cloth for glass greenhouses and 60% for polycarbonate structures, because glass tends to trap more heat than polycarbonate panels.
| Greenhouse Type | Recommended Shade Percentage | Reason |
|---|---|---|
| Glass greenhouse | 70% | Glass traps more heat and overheats faster than other materials |
| Polycarbonate greenhouse | 60% | Polycarbonate diffuses light naturally, so less shading is needed |
Choosing the correct percentage matters. Too much shade can slow plant growth during cooler stretches, while too little defeats the purpose of temperature management.
When Should You Install and Remove Shade Cloth?
Install shade cloth seasonally as soon as daytime temperatures are consistently hot, and remove it once days cool in the fall. BC Greenhouse Builders experts recommend watching the weather rather than committing to a fixed date, since timing varies year to year. One year, the cloth might go up in May, another year in early June.
The key principle is to maximize light exposure during the cooler months (mid-September through spring), when plants need every bit of sunlight to grow as quickly as possible. Seasonal installation gives you the flexibility to respond to your specific climate rather than leaving the cloth up and sacrificing valuable growing light.
How Do You Apply Shade Cloth to a Greenhouse?
The simplest and most effective method is to drape the shade cloth lengthwise over the roof of your greenhouse. According to BC Greenhouse Builders, orienting your greenhouse east to west gives the long side a south-facing exposure, which provides the most direct light in winter and the most heat exposure in summer.
For roof-mounted installation, pull about two-thirds of the cover over the ridgeline and onto the south side, with the remaining one-third covering the north side. You do not need to cover the entire surface, including the sides, as that provides more shade than necessary. At high northern latitudes, the summer sun beats almost straight down at midday, so covering the roof is enough.
A practical tip: fold the cover carefully each fall and keep ropes tied to the end grommets. This way, the folded cover is easy to pull open one side at a time when spring arrives. Installation takes about 30 minutes once you have a system in place.
Commercial greenhouses often use an alternative approach, running shade cloth along interior wires from end to end. This allows the cover to be pulled open or shut over specific sections, such as a sitting area or a lettuce patch. Interior mounting also lets you quickly retract the shade during a long rainy or cloudy spell when the soil stays too wet.
What Size and Features Should You Look For in Shade Cloth?
BC Greenhouse Builders recommends choosing a shade cloth with grommets installed every two feet along the edges, as this gives you the most tie-down options and prevents the fabric from catching wind like a sail. UV-stabilized fabric is also essential, since it allows the cloth to last several years without breaking down in the sun.
Sizing can be tricky for home greenhouses. Many standard covers sold online are either too small for larger structures (like a 16 x 20 greenhouse) or too large for compact models (like an 8 x 12). Our sister company Charley's Greenhouse and Garden Supply, carries a variety of shade covers sized for home growers, making it easy to find the right fit without the minimum order requirements that come with commercial suppliers. For a 16 x 20 greenhouse, a green 60% shade cloth in a 12-foot width by 20-foot length works well.
Look for covers that come pre-sewn on the edges with grommets already installed, which saves significant time compared to adding your own. Knitted shade fabrics are easy to sew if you do need to adjust sizing, and some growers even add custom grommets, though most people prefer the convenience of a ready-made product.
Can Shade Cloth Be Left On Year-Round?
In most cases, no. BC Greenhouse Builders' designs show that removing shade cloth from mid-September through spring allows plants to grow as fast as possible during the low-light months. During the summer, you want less light and heat, but the rest of the year, you want every bit of sun available.
The one exception is interior-mounted shade cloth suspended on wires inside the greenhouse. This setup can stay in place year-round because you simply pull the cloth back and forth as needed. For exterior-mounted cloth, seasonal installation and removal is the better approach for your climate.
Can Tree Cover Replace Shade Cloth?
A mature deciduous tree can serve as natural shade if the timing works out perfectly. If a nearby tree leafs out in late May and drops its leaves by early September, it provides shade exactly when you need it and full sun when you do not. However, this kind of perfect alignment is rare, and most growers will still benefit from the precise control that shade cloth provides.
Ready to Create a Cooler, Healthier Greenhouse?
Adding shade cloth is one of the simplest upgrades you can make to your greenhouse, and the results are immediate. The moment the cloth goes on, temperatures drop, fans quiet down, and your plants can finally take a deep breath.
Here is a simple action plan to get started:
- Determine your greenhouse glazing type (glass or polycarbonate) and choose the right shade percentage
- Measure your roof to find the correct cloth size
- Select a UV-stabilized cloth with pre-installed grommets every two feet
- Install the cloth over the roof once summer heat arrives, pulling two-thirds to the south side
- Remove the cloth in mid-September to maximize fall and winter light
BC Greenhouse Builders offers shade cloth and accessories to help you get set up quickly. Browse the BC Greenhouse shade cloth tool for sizing options, or request a free catalog for more greenhouse gardening tips and product details.
Contact BC Greenhouse Builders to talk through your growing goals with an expert.
