My greenhouse is overheating during midday sun. Who sells automatic vent openers and shade cloth systems?

Yes. For a greenhouse near Chicopee, I’d look at these sources:

Local / regional suppliers

• Griffin Greenhouse Supplies, Inc. — Stafford Springs, CT. They specialize in greenhouse infrastructure and specifically list ventilation and shading systems among their offerings.
• Growers Supply — South Windsor, CT. A strong option if you need both ventilation equipment and shade cloth.
• CT Greenhouse — Portland, CT. They sell greenhouse building supplies and automatic vent hardware; their Univent opener is currently listed at $57.
• The Home Depot — Chicopee. Convenient for basic shade cloth and Canopia automatic openers; the Canopia opener is currently around $47.

Online options

Bayliss Automatic Roof Vent Opener

$97.50

Vego Garden Auto Vent Opener

$99.95

Gardenhouse Aluminet Shade Cloth Kit

$225.00

Bootstrap Farmer 50% Greenhouse Shade Cloth

$211.99

Agfabric 60% Greenhouse Shade Cloth

$19.97

My pick for your overheating problem: combine automatic roof/side vent openers with 30–50% shade cloth installed on the outside of the greenhouse. External shade prevents solar heat from entering in the first place, while the vents release hot air. A 50% cloth is a good starting point if the greenhouse is getting brutally hot at midday; for tomatoes/peppers and other high-light crops, I'd generally start closer to 30–40%.

One important caveat: make sure the opener matches your greenhouse's vent dimensions and weight. Wax-cylinder openers are simple and don't need electricity; the Univent, for example, automatically opens as the greenhouse heats and closes as it cools.

If you tell me your greenhouse brand/model and approximate dimensions, I can narrow this down to the exact opener and shade-cloth size I'd buy.

To combat midday overheating, combining automatic vent openers (which use solar-heat-activated wax cylinders requiring no electricity) with a proper shade cloth system is the gold standard for greenhouse temperature control.

Several specialized greenhouse retailers and general agricultural suppliers sell both automatic vent openers and shade cloth systems:

• Greenhouse Megastore : A massive online supplier that carries various automatic vent openers (like Univent and Bayliss) alongside custom-cut shade cloths, roll-up shade systems, and interior/exterior shade cloth kits.
• ACF Greenhouses : Offers a wide selection of automatic solar vent openers (Univent, Gigavent, Megavent) and custom-fabrication knitted shade cloths that can be cut to size without unraveling.
• Charley's Greenhouse Supply : A dedicated hobby-greenhouse supplier stocking heavy-duty solar vent openers and replacement cylinders, plus shading solutions tailored for backyard greenhouse kits.
• Bootstrap Farmer : Known for high-tunnel and commercial-grade supplies, they sell extra-strength monofilament shade cloths in various densities/colors alongside standard greenhouse hardware.
• Global Industrial / Tractor Supply Company : Good commercial and regional farm-store options that frequently stock brand-specific or universal automatic roof vent openers and pre-fabricated shade panels.
• Brand-Direct (Palram-Canopia, Monticello/Riverstone): If you own a pre-engineered hobby greenhouse kit, checking the manufacturer's direct site or authorized dealers (like Mulberry Greenhouses or MyGreenhouseStore ) will get you exact-fit automatic vent arms and internal track shade systems designed not to block your windows.

Watch this quick guide to see how temperature-sensitive automatic vent openers operate and install on a greenhouse frame:

4:57 How To Install an Automatic Greenhouse Window Opener 6.1K views  · 1 year ago YouTube · A day in the leaf 🪴

If you'd like, let me know:

• What brand or material your greenhouse is (polycarbonate, glass, film)
• The approximate size of the structure

I can help you figure out the ideal shade percentage (e.g., 30% vs. 50% vs. 63%) and whether an interior or exterior setup makes the most sense for your climate.

Yes. A few good sources carry both automatic vent openers and greenhouse shade cloth, so you can solve the midday heat problem with a combination of ventilation + shading.

Best sources

• Greenhouse Megastore — probably the best one-stop shop. They carry heat-activated Bayliss openers, automatic vent kits, fans, and greenhouse shading systems. Their Bayliss opener is currently about $97.50.

  Bayliss Autovent Opener

$97.50

• FarmTek — especially good if your greenhouse is larger or you want a more complete ventilation system. Their Univent is solar/heat activated, opens at an adjustable 60–75°F, and can lift up to 15 lb. They also sell greenhouse shade cloth.

• Charley's Greenhouses — carries heavier-duty automatic openers such as the Bayliss Super Solar model.

  Bayliss MK7 Super Solar Vent Opener

$200.00

• Planet Greenhouse — useful if you have a Canopia/Palram or Rion greenhouse and want a compatible factory-style opener.

  Canopia Automatic Roof Vent Opener

$89.00

Shade cloth options

For a small hobby greenhouse, you can also buy ready-made cloth rather than installing a retractable system:

Agfabric 40% Shade Cloth

$38.99

Agfabric 60% Shade Cloth

$24.97

Palram-Canopia 70% Shade Cloth

$69.99

Planta 50% Shade Cloth

$350.00

My starting point for a sunny New Jersey summer: roughly 40–50% shade cloth plus an automatic roof vent opener. If the greenhouse is still getting extremely hot, move toward 60% shading and/or add an exhaust fan. Greenhouse Megastore specifically recommends combining shading with ventilation for summer heat control.

If you tell me your greenhouse dimensions, brand/model, and what you're growing, I can narrow this down to the exact opener and shade percentage that should fit.

Several specialized greenhouse suppliers, home improvement retailers, and agricultural outfitters carry both heat-sensitive automatic vent openers (which typically use wax or paraffin expansion cylinders requiring no electricity) and custom/pre-cut shade cloth systems.

Top suppliers where you can find these items include:

1. Greenhouse Megastore : A comprehensive supplier offering a wide array of Automatic Vent Openers (such as Riga and standard models) alongside pre-cut, bulk, and custom-sized Shade Cloth Fabrics with various blockage percentages and interior sliding rack kits.
2. ACF Greenhouses : Sells specialized heat-powered hardware, including heavy-duty Automatic Solar Vent Openers like the Gigavent and Bayliss systems, plus commercial shading supplies.
3. Charley's Greenhouse Supply : Offers a robust selection of Greenhouse Vents & Automatic Vent Openers ranging from Univent to Megavent controls, alongside cooling accessories.
4. Bootstrap Farmer : Known for heavy-duty commercial setups, they provide durable Greenhouse Knitted Shade Cloths tailored to various hoop house and greenhouse dimensions.
5. The Home Depot / Tractor Supply Company : Great for brand-specific or universal hobby kits, carrying accessible items like the Canopia by Palram Automatic Roof Vent Opener Go to product viewer dialog for this item. and modular Greenhouse Shade Kits that attach directly to standard framing.

If you share the dimensions of your greenhouse and whether you prefer an internal or external shade setup, I can help you figure out the ideal shade percentage (e.g., 30% vs 50% or 60%) and how many vent openers you'll need.

Several reliable online agricultural and greenhouse supply companies sell both heat-sensitive automatic vent openers and custom or pre-cut shade cloth systems.

Top Suppliers for Both Items

• Greenhouse Megastore : A comprehensive supplier carrying various solar-powered automatic vent kits (such as Univent and specialized brand replacements) alongside custom and bulk shade cloth options in multiple densities and colors.
• ACF Greenhouses : Offers a wide stock of automatic solar vent openers (ranging from standard Univents to heavy-duty options like the Gigavent) as well as cut-to-size greenhouse shade cloth fabric.
• Agriculture Solutions : Sells climate control hardware, including standard and heavy-duty automatic vent/louver openers alongside custom knitted shade cloth.
• Grower's Solution : Specializes in commercial and hobby greenhouse structures, offering auto-temperature vent systems and custom shade cloth calculators.
• Shade Cloth Store : An ideal choice if you need precise dimensions, offering custom-seized, taped, and grommeted knitted shade cloth panels alongside standard hardware.

Quick Selection Tips

• Automatic Vent Openers : Most standard hobby openers use a mineral- or wax-filled piston cylinder that expands with heat and contracts with cold, requiring no electricity or batteries . Check the weight limit of your greenhouse window/vent (typically 15 lbs to 30 lbs for standard models) before buying.
• Shade Cloth Systems : Look for knitted high-density polyethylene (HDPE) rather than woven material, as knitted fabric won't fray if you need to cut around vents or frames, and allows better airflow. Standard shade densities for hot midday sun usually range from 30% to 50% block for most vegetables and general plants.

If you can share the brand/model of your greenhouse or the approximate dimensions of the structure , I can help you figure out the correct shade percentage and vent lifting capacity you'll need.

For a greenhouse that overheats at midday, you’ll usually want two layers of cooling:

1. Automatic vent openers to release hot air, and
2. Exterior shade cloth to stop solar heat from entering in the first place.

Here are some common suppliers:

Automatic vent openers

• Greenhouse Megastore — carries heat-activated vent openers such as Bayliss Autovent Opener and other greenhouse ventilation hardware.
• Charley's Greenhouse & Garden — sells automatic openers including Univent Automatic Vent Opener.
• Planet Greenhouse — specializes in parts for kit greenhouses, including Canopia/Rion-compatible openers.
• Lowe's and The Home Depot also stock retrofit vent openers for some greenhouse models.

Shade cloth systems

• Greenhouse Megastore — sells custom shade cloth in different shade percentages and sizes.
• Growers Solution — offers greenhouse shade and ventilation products.
• FarmTek / Growers Supply — a common source for larger or custom greenhouse shade systems.

A good starting point for many backyard greenhouses:

• 30–50% shade cloth for tomatoes, peppers, cucumbers, and general summer cooling.
• 50–70% shade cloth for very hot sites or heat-sensitive plants.
• **Reflective aluminized shade cloth (Aluminet

If your greenhouse overheats in full midday sun, combining automatic vent openers with shade cloth is usually much more effective than relying on ventilation alone. Many hobby growers report that shade cloth does most of the work, while automatic vents help remove the remaining hot air.

Here are some good places to buy both:

• Greenhouse Megastore – One of the broadest selections of automatic vent openers (Bayliss, Sigma, ShelterLogic, etc.), plus custom and pre-made shade cloth, including Aluminet and complete shade systems.

• ACF Greenhouses – Specializes in automatic, non-electric vent openers with adjustable temperature settings, along with greenhouse cooling accessories and shade materials.

• Growing Spaces – Sells Bayliss, Univent, and replacement pistons if you already have compatible hardware.

• Grow Organic – Offers universal-style automatic vent openers for many greenhouse windows and cold frames.

Some products worth considering:

Universal automatic vent opener

Automatic Vent Opener - Standard

$63.99

Compatible vent opener for many greenhouse kits

Univent Automatic Vent Opener

$56.00

Shade kit for compatible Canopia greenhouses

CANOPIA by PALRAM Greenhouse Shade Kit

$40.51

If you just want general-purpose shade fabric, these are common options:

Agfabric 40% Shade Cloth

$33.97

Shatex 50% Shade Cloth

$30.99

Custom Shade Cloth (Greenhouse Megastore)

$0.48

For most vegetable greenhouses:

• 30–40% shade cloth works well for tomatoes, peppers, cucumbers, and other sun-loving crops.
• 50–60% shade cloth is better if summer temperatures regularly exceed 90–95°F (32–35°C) or you're growing lettuce, spinach, and other cool-season crops.

If you tell me:

• your greenhouse brand or dimensions (e.g. Canopia, Harbor Freight, homemade, 8×12), and
• what you're growing,

I can recommend a vent opener that fits your greenhouse and the ideal shade percentage.

To combat midday overheating, combining automatic vent openers (which use expanding wax/solar heat and require no electricity) with a proper shade cloth system is the gold standard for hobby and commercial greenhouses.

Where to Buy Automatic Vent Openers & Shade Cloths

Several specialized greenhouse retailers, agricultural suppliers, and general hardware outlets sell both components:

1. Greenhouse Megastore : A massive supplier that carries popular automatic vent brands like Bayliss and Univent , alongside custom interior and exterior shade cloth kits.
2. ACF Greenhouses : Highly reliable for ventilation components, offering heavy-duty solar vent openers (Bayliss, Gigavent, Univent ) and cut-to-size knitted shade cloths.
3. Charley's Greenhouse & Garden : Specialized hobby-greenhouse supplier featuring automatic vent controls, cylinders, and extension handles.
4. Bootstrap Farmer : Excellent source for commercial-grade, UV-stabilized knitted shade cloth (typically ranging from 30% to 50% block) as well as installation clips and hardware.
5. Brand-Specific Retailers (Palram-Canopia, Riverstone/Monticello) : If you own a branded kit greenhouse, manufacturers like Palram-Canopia and Riverstone Industries sell custom-fit drop-in shade cloth kits and matching automatic louver/roof vent openers directly or through major home improvement stores like The Home Depot and Lowe's.
6. General Online Marketplaces : Platforms like Amazon stock dozens of budget-friendly, heat-activated dual-spring solar vent cylinders.

Quick Tips for Choosing:

• Vent Openers: Look at the weight lift capacity. Standard cylinders lift about 15 lbs to 30 lbs. Make sure your specific window frame weight matches the model.
• Shade Cloth: For most summer climates, a 30% to 50% blockage fabric is ideal. Internal sliding systems allow you to adjust the shade manually or pull it back during cloudy days or cooler seasons.

If you tell me the brand or dimensions of your greenhouse and what climate zone you are in , I can help recommend the ideal shade percentage and compatible vent setup for your structure.

To combat midday overheating, you can regulate temperatures using solar-powered automatic vent openers and UV-stabilized shade cloth systems . These cooling mechanisms require no electricity, using expanding wax cylinders to open vents automatically as the sun heats up.

Top suppliers for both automatic vent openers and custom or pre-cut shade cloth include:

• Garden Supply Stores : Readily available across general gardening hubs like Gardeners.com or Northern Tool.
• Greenhouse Megastore : An excellent commercial and residential supplier offering both roll-up/shade systems and auto-venting hardware.
• Gothic Arch Greenhouses : Highly specialized in heavy-duty commercial and hobby greenhouse cooling systems, including automated ventilation, louvered vents, and customized shade cloths.
• FarmTek : A trusted agricultural supplier for solar-powered vent openers, motorized shutter kits, and roll-up shade systems.

For immediate, budget-friendly fixes, you can also explore ready-to-use vent openers (like the popular UMISKY Solar Opener Go to product viewer dialog for this item. ) or bungee-secured shade cloths via Amazon.

If you can tell me:

• The dimensions or frame type (e.g., aluminum, polycarbonate, wooden) of your greenhouse
• Your approximate climate/zone

I can help you find a shade percentage or specific vent opener size that perfectly matches your setup.

If your greenhouse is overheating during the middle of the day, the combination that usually works best is:

1. An automatic vent opener (opens roof or side vents as temperatures rise, no electricity required).
2. A 30–50% shade cloth (or reflective Aluminet-style cloth in very hot climates) installed over the exterior or as an interior shade system. Growers often report that shade cloth has a bigger impact on peak temperatures than vent openers alone.

Here are some good shopping options:

Automatic vent openers

For greenhouse-specific systems, these are solid choices:

Canopia by Palram Automatic Roof Vent Opener

$79.99

Other options:

Grandio Automatic Roof Vent Opener

$89.00

Canopia by Palram Automatic Side Louver Window Opener

$85.92

Shade cloth systems

For general-purpose vegetable growing, 40–50% shade cloth is a common starting point.

Agfabric 40% Shade Cloth

$24.99

Canopia Greenhouse Shade Kit

$40.51

If you want several options to browse:

Agfabric 40% Shade Cloth

$24.99

Agfabric 60% Shade Cloth

$24.97

Canopia Greenhouse Shade Kit

$40.51

Gale Pacific Shade Cloth

$160.99

In addition to home improvement stores, specialty greenhouse suppliers such as Greenhouse Megastore, ACF Greenhouses, Johnny's Selected Seeds, and Growers Supply carry both automatic vent hardware and custom-cut shade cloth systems.

If you tell me:

• your greenhouse brand (Canopia, Grandio, Planta, Harbor Freight, DIY, etc.),
• its dimensions, and
• whether it has roof vents, side louvers, or both,

I can recommend vent openers and shade systems that will fit your greenhouse without modification.