18ft x 20ft Blue Sun Shade Sail UPF50 Rectangle - Cools Patio

In this review of the 18' x 20' Blue Sun Shade Sail UPF50 Rectangle, the bottom line is simple: it is a practical, heavy duty shade solution for anyone wanting to lower temperatures and block harmful rays without adding a permanent structure. The reviewer found it ideal for patios, carports and poolside areas where breathability and UV protection matter. Most users will appreciate the fabric's UV protection and durable attachment points, and the review focuses on real-world performance rather than marketing claims.

Key Features

• Woven HDPE fabric: provides a breathable canopy that lets air and water pass through while blocking up to 95% of UV rays to reduce surface and air temperature.
• Stainless steel D rings: heavy duty corner rings attached to white webbing give reliable anchor points that resist corrosion and handle tension well.
• Water permeable design: the sail drains and breathes so it does not pool water and reduces wind pressure compared with solid tarps.
• Custom sizing available: the maker offers tailored sizes so you can match unusual spaces when the standard 18' x 20' size does not fit.
• Rectangle styling: a clean geometric shape that integrates with many outdoor designs and can be layered or combined for broader coverage.

Who It's For

This product is best for homeowners and renters who want a semi-permanent shade solution for a patio, carport or pool area and who value breathability and UV blocking over full waterproofing. It works well when anchored to posts, trees or building walls using proper hardware kits.

It is not ideal for those who need a fully waterproof cover or need complete sun blocking with no light transmission; if you require a rainproof shelter or an enclosed structure, consider a different style of canopy or hard top instead.

Pros & Cons

Pros

• Durable woven HDPE material that customers report as long lasting and holding up well in strong winds.
• Effective at reducing temperature and providing substantial shade while remaining breathable.
• Stainless steel D rings and heavy webbing make installation secure when paired with the right hardware.
• Custom sizes available to fit nonstandard outdoor spaces.

Cons

• Not waterproof; water permeability means it will not keep rain out of the covered area.
• Manual sizing and measurement can lead to slight variations, so careful measurement is required before ordering.

Specifications

Brand	ShadeMart
Shape	Rectangle
Size	18' x 20' (can be customized)
Material	Woven HDPE (High Density Polyethylene)
Corner Hardware	Stainless steel D rings on heavy white webbing
Functionality	Water permeable, breathable, blocks up to 95% UV

Our Verdict

The 18' x 20' ShadeMart rectangle sail is a sensible value purchase for anyone needing reliable UV shading and improved comfort outdoors without a permanent build. It combines durable materials and strong anchor points with breathable performance, making it a good choice for patios, carports and pool areas when rainproofing is not required.

Frequently Asked Questions

Is this shade sail waterproof?
No. The fabric is water permeable and designed to allow water and air to pass through rather than provide a waterproof cover.

Can it be installed on my house or trees?
Yes. With the proper hardware kits the sail can be attached to poles, trees, walls, roofs and other structures.

Will it block sun and heat?
Yes. The woven HDPE blocks up to 95% of UV rays and typically lowers temperatures under the sail, depending on placement and airflow.