Last summer in Astoria, Queens, I hit a breaking point.

My living room had everything going for it. Big windows, great light, a nice cross breeze in the mornings. But by 1 PM, it turned into something else entirely. The kind of heat that doesn’t just sit in the air, it radiates from the walls, the floor, even the couch.

I kept lowering the AC temperature. It helped, but not enough. And honestly, the bill at the end of the month made it clear I was solving the wrong problem.

So I tried something simple.

I placed a thermometer one foot away from my south-facing window and tracked the temperature for a week. Then I switched curtains and repeated the same process.

No lab setup. No controlled environment. Just real conditions, real sunlight, and real results.

If you’ve been searching for the best curtains to keep heat out, this is not a list based on guesses. It is based on what actually worked.

Why Curtains Matter More Than You Think

Before we get into the list, let’s understand what’s happening.

When sunlight enters your room, it carries heat energy. Glass doesn’t block it effectively. So your room heats up from the inside.

This is why your AC struggles. It is constantly fighting incoming heat.

Good heat reducing curtains don’t cool your room. They reduce how much heat enters in the first place.

That shift changes everything.

The Testing Method (Simple but Honest)

Here’s how I tested each type:

• Location: South-facing window in Astoria, Queens
• Weather: Peak summer (82 to 91°F / 28 to 33°C)
• Thermometer placement: 1 foot from glass
• Time recorded: 1 PM (peak heat)
• Duration: 2 days per curtain type

The goal was not perfection. It was consistency.

What You Should Look for in Heat Blocking Curtains

Before we get into the list, here are the factors that made the biggest difference:

• Fabric density
• Number of layers
• Curtain coverage (floor-length vs short)
• Fit (gaps vs full seal)

Keep these in mind as you read.

The 9 Best Curtains to Keep Heat Out

1. Triple-Layer Thermal Curtains (Best Overall)

These performed the best across all tests.

They typically include:

• Decorative outer layer
• Insulating core
• Backing layer

Result:
Reduced window-side temperature by 7 to 9°F

This was the only option that made the space feel immediately more comfortable.

If you are serious about finding the best heat blocking curtains, this is where you start.

2. Blackout Curtains with Thermal Backing

Blackout curtains alone are great for light. But when combined with thermal backing, they become powerful heat blockers.

Result:
Reduced temperature by 6 to 8°F

Slightly less effective than triple-layer thermal, but still strong.

Also ideal for bedrooms.

3. Dense Polyester Curtains with Lining

This is the most practical everyday option.

High-quality polyester with proper lining performed surprisingly well.

Result:
Reduced temperature by 5 to 7°F

These are some of the most accessible curtains to keep heat out without going fully blackout.

4. Linen Blend Curtains (With Lining)

Linen alone is breathable, not insulating. But when paired with lining, it becomes functional.

Result:
Reduced temperature by 3 to 5°F

Not the strongest, but good for spaces where aesthetics matter.

5. Cotton Curtains (Heavy Weave)

Thick cotton performed better than expected, especially when tightly woven.

Result:
Reduced temperature by 3 to 4°F

Still limited compared to layered curtains.

6. Patterned Custom Curtains with Thermal Add-On

This is where style meets function.

Curtains like Ester – Pool Blue or Blooming Spring – Red Apple can be customized with thermal lining.

Result:
Reduced temperature by 5 to 7°F

You don’t have to compromise on design to get performance.

7. Room Darkening Curtains

These sit between regular and blackout curtains.

Result:
Reduced temperature by 4 to 6°F

Good balance between light and heat control.

8. Roller Shades + Curtains Combo

Layering made a noticeable difference.

A simple roller shade behind a curtain improved insulation.

Result:
Reduced temperature by 5 to 8°F

Not a curtain alone, but worth mentioning.

9. Sheer Curtains (Least Effective)

Let’s be honest.

Sheer curtains look beautiful, but they don’t do much for heat.

Result:
Reduced temperature by 1 to 2°F

They diffuse light, not heat.

What Surprised Me the Most

A few things stood out during testing:

Thickness Matters More Than Color

A thick light-colored curtain performed better than a thin dark one.

Gaps Ruin Everything

Even the best curtain failed if sunlight leaked from the sides.

Layering Changes the Game

Two moderate layers often outperformed one heavy layer.

Best Curtains to Keep Heat Out (Quick Summary)

If you don’t want to read everything again, here’s the simple version:

• Best overall → Triple-layer thermal curtains
• Best for bedrooms → Blackout with thermal backing
• Best balance → Polyester with lining
• Best design + function → Custom curtains with thermal add-on

What Works Best in New York Homes

Based on real apartment setups:

South-Facing Windows

Go for:

Full coverage

Thermal curtains

Living Rooms

• Light-filtering with thermal backing
• Avoid blackout unless needed

Bedrooms

• Blackout + thermal

Curtain Avenue Picks That Make Sense

If you want options that actually align with these results:

Thermal Curtains Collection

Blackout Curtains

Custom Curtains (Add Thermal Lining)

Final Thoughts

After testing all of these, one thing became clear.

There is no single “best” curtain for everyone.

The best curtains to keep heat out depend on your room, your sunlight exposure, and how you use the space.

But if your room heats up every afternoon, doing nothing is not neutral. It is a choice.

And once you fix it, you will feel the difference every single day.

Ready to Upgrade Your Space

If your room feels warmer than it should, start with your windows.

Shop our custom heat blocking curtains — free swatches ship today.

Because sometimes, the smartest way to cool your home is not by adding more air.

It is by stopping the heat from getting in.