Double vs triple glazing
By Lydia Tobin | 9th January 2026 | 5 min read
If you’re thinking about upgrading your windows, you may be weighing up the pros and cons of going for double or triple glazed windows. We’ll break down the differences so you can plan your upgrade with confidence.
What's the difference between double and triple glazing?
The main difference you need to know is that double glazing is two panes of glass separated by a spacer and filled with a gas (usually argon as this is a denser, inert gas). Whereas triple glazing follows the same principle but uses another spacer and glass pane to create an extra barrier between your home and the outdoors.
Insulation and energy efficiency
When it comes to measuring the insulation and efficiency of your windows, a U-value is used. This determines how well a window keeps heat in your home. The lower number means the less heat escaping and lower energy bills.
Double glazing has an average U-value of around 1.2–1.6 W/m²K
Triple glazing has an average U-value of around 0.8–1.0 W/m²K
This means triple glazing can reduce heat loss by up to 30% compared to double glazing, but double glazing still offers excellent insulation for most UK homes.
Noise reduction
Both double and triple glazing reduce outside noise. Triple glazing offers a slight improvement, but if soundproofing is your priority, glass thickness matters more than the number of layers.
Maintenance and lifespan
Double and triple glazed windows should both last at least 20 years. Even though they have similar lifespans, triple glazed windows may not last as long because they are heavier and can put extra stress on the frames.
By taking care of your windows, you could increase their lifespan. Make sure to clean your windows at least twice a year, avoiding abrasive chemicals and checking seals for damage.
What’s the price difference between double and triple glazing?
Costs will vary between size and style of the windows. But on average, triple glazed windows are 10-30% more expensive than double glazed windows.
Is triple glazing better than double glazing?
Triple glazing is arguably performs better as it provides better insulation and energy efficiency, which is ideal for homes in very cold regions. However, because the UK has a relatively mild climate, the difference in performance may not be significant enough to outweigh the extra cost for most homes. Whereas, double glazing remains a fantastic option for most, it’s lighter, more affordable, and still delivers excellent insulation.
How to make the upgrade
Replacing your windows is a complex job that’s best left to the professionals. For seasoned DIYers, we have a guide you can read, here, but for most, using a trusted installer is the easiest route.
Using our fitted windows and doors service
Our fitted windows and doors service currently offers double glazing only, which is a great choice for most UK homes. Here’s how it works:
1. Book an online appointment
Click here to book an appointment with one of our helpful colleagues who will provide a free pre-survey estimate and help visualise your project.
2. Arrange your survey
After your estimate, we’ll book a technical home survey to give you a full quotation.
3. Agree your quotation
Your surveyor will confirm all details. Once you agree, we’ll process your order.
4. Installation
Your windows and doors will be delivered on the day of installation. Once fitted, your installer will register with FENSA and issue your certificate and manufacturer guarantee.
Looking for a triple glazing installer?
1. Check for certification
Look for FENSA or CERTASS accreditation to ensure the work meets UK building regulations.
2. Ask about frame suitability
Triple glazing is heavier, so confirm your frames can handle the extra weight or if replacements are needed.
3. Get a detailed quote
Make sure it includes any extra work for frames and hardware so there are no surprises.
FAQs
Is it worth upgrading from double to triple glazing?
If your current double glazing is old or underperforming, replacing it with modern double-glazed windows can significantly improve insulation and comfort. Triple glazing offers extra efficiency, but because it’s designed for colder climates, the added cost may not deliver major benefits for most UK homes.
Does triple glazing increase house value?
Good glazing can make a home more appealing to buyers. This is because windows with strong energy ratings, whether double or triple glazed, can help improve comfort and running costs. Though value is perceptive and it will all depend on your local market.
Is 6mm glass better than 4mm?
Is it worth upgrading from double to triple glazing?
If your current double glazing is old or underperforming, replacing it with modern double-glazed windows can significantly improve insulation and comfort. Triple glazing offers extra efficiency, but because it’s designed for colder climates, the added cost may not deliver major benefits for most UK homes.
Does triple glazing increase house value?
Good glazing can make a home more appealing to buyers. This is because windows with strong energy ratings, whether double or triple glazed, can help improve comfort and running costs. Though value is perceptive and it will all depend on your local market.