Composite doors are praised for their energy efficiency, strength, and style. However, if yours is letting in cold air, it can be disappointing—especially after investing in a high-quality door. Cold draughts are more common than many expect, even in well-fitted composite or patio doors. Often, the issue lies in poor installation, worn seals, or frame misalignment. Identifying problem areas like gaps around the edges or faulty hinges is key. Whether you're dealing with a new composite door or upgrading patio doors, quick fixes such as adjusting the hinges or replacing seals can restore comfort and keep the chill out.

What Are Composite Doors?

Composite doors are made from a combination of materials. Typically, they include a solid timber core, layers of insulating foam, a uPVC or aluminium outer frame, and a durable glass-reinforced plastic (GRP) skin. This blend of materials is designed to provide excellent thermal insulation, security, and weather resistance.

Unlike standard timber doors, composite doors don’t swell or warp easily. They also require very little maintenance. Their multi-layered structure is ideal for British weather – in theory. But like any product, their performance depends heavily on quality installation and long-term care.

Why Do Composite Doors Let in Cold Air?

Despite their strong insulating qualities, composite doors can still let in cold air for a few common reasons. Here’s a breakdown of the most likely culprits:

If you're noticing any of the above symptoms with your composite doors Cardiff, it's important to act fast before the issue worsens. Even small gaps can lead to noticeable heat loss and higher energy bills.

Composite Doors vs Patio Doors: Which Offers Better Insulation?

When it comes to energy efficiency, both composite and patio doors offer strong benefits – but in different ways.

Composite doors are best suited for front or back entrances where insulation and security are a priority. Their solid core and layered construction naturally limit cold air intrusion.

Patio doors, on the other hand, often feature large glass panels that can be a weak point if not properly insulated. However, modern patio doorscome with double or triple glazing, thermal breaks in the frames, and improved sealing systems that significantly boost their efficiency.

If your patio doors are older or made from poor materials, they might be more prone to draughts than a well-installed composite door. That said, both types can fail if the seals degrade or the doors aren’t aligned properly.

How to Spot the Source of the Cold Air

Before reaching for a toolbox or calling in professionals, try to identify exactly where the draught is coming from. Here are a few easy methods:

• Candle test: Light a candle and slowly move it around the edge of the door. If the flame flickers, you've found a draught.
• Daylight check: Look around the frame in daylight. Can you see slivers of light coming through? That’s a sign of gaps.
• Feel for airflow: Run your hand along the edges of the door during a windy day. You’ll quickly feel where the cold air is entering.
• Sound test: Listen for a whistle or rattle during gusty weather. It may indicate loose fittings or a warped frame.

Diagnosing the source helps you choose the most effective fix.

Fast Fixes You Can Do Today

Once you’ve found the problem, here are some quick and effective solutions to stop cold air from entering through your composite door:

1. Replace Weather Stripping

Worn or flattened rubber seals are one of the most common reasons for draughts. Replace them with new weather stripping from a DIY shop. Many products come in peel-and-stick form, making installation easy.

2. Install a Door Sweep or Draught Excluder

A door sweep at the bottom of your door can block cold air from creeping underneath. Alternatively, a brush or rubber strip can also serve the purpose without affecting how the door opens and closes.

3. Tighten Loose Hinges

Over time, hinges can loosen due to repeated use. If your door seems slightly out of line, use a screwdriver to tighten the screws. This can help reposition the door and create a tighter seal.

4. Use Expanding Foam Around the Frame

If there are gaps between the wall and the door frame, expanding foam can fill them easily. Be careful not to overdo it – foam expands rapidly and can distort the frame if applied excessively.

5. Adjust the Strike Plate

If your door doesn’t latch firmly, adjusting the strike plate may help. Loosen the screws slightly, shift the plate, and retighten until the door fits snugly when closed.

6. Hang a Heavy Curtain

As a temporary or additional measure, a thick curtain across the inside of your door can block draughts and retain heat.

These fixes are low-cost and can make an immediate difference in comfort and energy efficiency.

When to Call in the Professionals

While many draught issues can be fixed with basic tools and DIY kits, some situations call for professional help:

• Your door frame is warped or damaged
• The door has dropped significantly and no longer sits correctly in the frame
• You suspect poor installation
• You’ve tried several fixes with no improvement

In these cases, a qualified fitter can assess whether the door needs to be refitted, adjusted, or replaced. In Cardiff, many homeowners turn to local experts who specialise in composite doors and patio doors Cardiff to ensure proper installation from the start.

Final Thoughts: Keep the Cold Out for Good

Composite doors are designed to be energy-efficient, but they must be well-fitted and maintained to perform as expected. If cold air is sneaking in, don’t ignore it – a few small fixes can protect your home from unnecessary heat loss and rising energy bills.

Maintenance tips:

• Check seals and hardware annually
• Clean the threshold and frame to avoid debris interfering with the seal
• Don’t slam the door – it can misalign the frame over time
• Lubricate locks and hinges every few months

If your current door is beyond a quick fix, it may be time to consider a new installation done professionally.

At AO Builders Cardiff, we offer expert door fitting services, including top-quality composite doors and bespoke patio doors. Whether you're replacing a draughty entrance or upgrading your home’s insulation, we’re here to help you make the right choice for year-round comfort.