Pick a 100% polyester hi-vis t-shirt rated to EN ISO 20471. That's the short answer. For summer site work, aim for 140–160gsm fabric with a moisture-wicking weave. Get those right and you'll stay cooler all shift. This guide is part of our Complete Guide to Summer Workwear.
What makes a hi-vis t-shirt breathable?
It starts with the fabric. Breathable hi-vis t-shirts use 100% polyester. Not cotton. Not a blend. Pure polyester.
Cotton fibres don't hold fluorescent dye well. Wash it a few times and the colour fades. A faded t-shirt typically fails EN ISO 20471 wash and colour-retention testing. That's not a compliant t-shirt anymore.
The weave matters just as much. Look for a bird-eye knit. That's a fabric with tiny open holes throughout. Air passes through those holes. Your skin breathes. You stay cooler. A thick, tight-knit polyester traps heat like any other fabric would.
Then there's fabric weight — measured in grams per square metre (gsm). Lower gsm means lighter fabric. For summer work, 140–160gsm is the sweet spot. Under 130gsm and the shirt feels flimsy and tears easily. Over 180gsm and it starts trapping heat.
Moisture-wicking is the other term to know. It means the fabric pulls sweat away from your skin. It spreads it across a wider area. Then it evaporates. You feel drier and cool down faster. A non-wicking polyester just holds sweat against you.
Class 1 or Class 2 — which do you need?
EN ISO 20471 is the UK standard for hi-vis clothing. It sets three classes based on how much fluorescent fabric and reflective tape a garment has. Class 3 is the highest. Class 1 is the lowest.
Most t-shirt-cut garments are rated Class 1. A t-shirt doesn't have enough fluorescent area to hit Class 2 on its own. Some two-tone designs — bright panels combined with dark contrast panels — do achieve Class 2. Don't assume yours does. Check the label.
Here's a quick guide to who needs what:
- Class 1 — warehouses, car parks, and low-traffic sites with slow-moving vehicles
- Class 2 — construction sites, roadside work, and sites with forklift traffic
- Class 3 — motorway work, high-speed roads, and rail environments
Most UK construction sites require Class 2 as a minimum. Check your site rules before buying. A Class 1 t-shirt worn alone won't meet that requirement.
Rail workers: RIS-3279-TOM requires Class 2 as a minimum. It also specifies an orange colourway. A Class 1 t-shirt won't get you onto a rail corridor on its own. You'll need a confirmed Class 2 garment or a compliant combination.
One more thing worth knowing: UK PPE sold from January 2023 should carry the UKCA mark. The CE mark is still recognised during the transition period. Look for one or the other on the garment label.
UV protection — why UPF matters in summer
Outdoor workers in the UK get real sun exposure across a full summer shift. Standard hi-vis polyester blocks some UV. But most garments aren't rated for it.
Some hi-vis t-shirts carry a UPF 40+ rating. That means the fabric blocks around 98% of UV radiation. For someone working outdoors every day, that adds up to meaningful skin protection over a season.
Look for garments with a confirmed UPF rating on the product page or care label. Browse our UV Workwear collection for rated options. For a deeper look at what UPF means on site, read our guide: UV Protection Workwear Explained.
Long sleeves give your forearms full coverage too. Browse our Hi-Vis Long Sleeve T-Shirts & Polos for options that protect without overheating you.
The best breathable hi-vis t-shirts we sell
Here are four options worth considering. Each covers a different use case.
1. Leo Workwear EcoViz Hi-Vis T-Shirt — best eco pick
Best for: warehouses, depots, lower-risk sites, and buyers who want a sustainable option.
The Leo EcoViz is made from GRS-certified recycled polyester with a bird-eye knit weave. Light, breathable, and moisture-wicking. The two-tone orange and navy design gives it a clean look. Rated to EN ISO 20471 Class 1. If your site rules allow Class 1, start here.
Leo Forda Hi-Vis T-Shirt EcoViz Class 1 Orange or Yellow Navy
2. Portwest PW311 Hi-Vis Cotton Comfort T-Shirt — best for feel against skin
Best for: workers who find standard polyester uncomfortable and want a softer short-sleeve option.
The PW311 uses Portwest's Cotton Comfort fabric — a polyester that feels softer against bare skin than standard technical fabrics. Short-sleeve cut, lightweight, and rated to EN ISO 20471 Class 1. Good choice for warehouse and depot workers who wear hi-vis all day and want something more comfortable against the skin.
Portwest PW311 Hi Vis T-Shirt Cotton Comfort Class 1 Workwear
3. Supertouch CottonCool Long Sleeve Hi-Vis T-Shirt Orange — best for UV arm coverage
Best for: outdoor workers who want full arm protection without the bulk of a jacket.
The CottonCool fabric feels soft against skin and holds its fluorescent colour through washing. Long sleeves protect your forearms from UV exposure all day. Good pick for landscapers, groundsworkers, and utilities teams on outdoor sites. Check the product page for EN ISO 20471 class details.
Supertouch Hi Vis Long Sleeve T-Shirt Orange CottonCool
4. Supertouch CottonCool Long Sleeve Hi-Vis T-Shirt Yellow — best yellow long-sleeve option
Best for: sites where yellow is required, or workers who prefer yellow hi-vis with full arm coverage.
The same CottonCool construction as the orange version — soft feel, holds fluorescent colour through washing, long sleeves for UV arm coverage. Saturn yellow colourway for sites where that's the required colour. Check the product page for EN ISO 20471 class details.
Supertouch Hi-Vis Long Sleeve T-Shirt Yellow CottonCool
Browse our full Hi-Vis T-Shirts collection for more options.
How to make your hi-vis t-shirt last
A hi-vis t-shirt is PPE. Treat it like one.
EN ISO 20471 tests wash durability as part of certification. But repeated washing still degrades fluorescence and reflectivity. The brighter it looks on day one, the more margin you have before it needs replacing.
Follow the care label. Most quality polyester hi-vis tees wash at 40°C. No bleach — it destroys the fluorescent dye. No tumble drying — heat breaks down the retroreflective tape's adhesion.
Check the reflective tape regularly. Run your finger along the edge. Lifting, peeling, or cracking means it needs replacing. A tape that doesn't reflect isn't protecting anyone.
Cared for correctly, a good polyester hi-vis t-shirt should last 50 or more washes before meaningful degradation. But check it. Don't assume. Replace it when it looks worn.
Frequently asked questions
Does a hi-vis t-shirt need to be EN ISO 20471 certified?
Yes — if the garment is worn as PPE on a site that requires hi-vis, it must meet EN ISO 20471. A branded fluorescent t-shirt without the standard mark is not compliant PPE. Look for the EN ISO 20471 class label on the garment or product listing before buying for site use.
Can I wear a hi-vis t-shirt on a construction site?
It depends on what class your site requires. Most UK construction sites need Class 2 as a minimum. Many hi-vis t-shirts are rated Class 1 only. A Class 1 t-shirt worn alone won't meet a Class 2 site rule. Check the garment label and your site induction paperwork before assuming it's compliant.
Why can't I use a cotton hi-vis t-shirt?
Cotton fibres don't hold fluorescent dye well enough to pass EN ISO 20471 wash and colour-retention tests. After a handful of washes, the fluorescence fades. The garment is no longer compliant. For certified hi-vis, stick to 100% polyester.
What gsm should I look for in a summer hi-vis t-shirt?
For summer work, 140–160gsm is the right range. Under 130gsm and the shirt feels too thin and can tear easily. Over 180gsm and it starts to trap heat. The sweet spot gives you a durable, breathable garment that holds up through a full working week.
Are recycled polyester hi-vis t-shirts as good as standard polyester?
Yes — when they're certified. GRS-certified recycled polyester meets the same EN ISO 20471 testing requirements as virgin polyester. The fluorescent dye bonds the same way. Performance is the same. The environmental footprint is lower. Check the garment carries a valid EN ISO 20471 class mark regardless of the fibre source.
Need to complete your summer kit? See our guides on Best Summer Work Trousers and Women's Summer Workwear. Or browse our Hi-Vis T-Shirts collection to shop the full range.