Thermal Performance in Concealed Track System

Thermal Performance of Minima Sliding Doors

When you’re investing in large-format glazing for an extension, garden room, or new build, thermal performance is one of the most important factors to get right. Poorly insulated doors can lead to significant heat loss in winter, uncomfortable overheating in summer, and energy bills that reflect both problems. At Minima Sliding, our Ultraline sliding door system is engineered to deliver exceptional thermal efficiency without compromising on the minimal aesthetics that define our product.

Ultraline 4 panel sliding doors with glass to glass corners installation Watford

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Reduce your utility bills with high performance glazing

Our high-performance double glazed argon-filled units feature low-e glass with black warm edge spacer bars.

Benefit from a thicker glazed unit

Our glazed units have an overall unit thickness of 36mm, made up of 6mm, 8mm or 10mm glass panes. Other systems are 28mm as standard.

Leave a smaller carbon footprint

Our sliding doors achieve an overall u-value of 1.2 with double glazing and 0.7 with triple glazing. The minimum u-value required for building regulations compliance is 1.2.
With u-values, the lower the number, the better the u-value. Our door system goes above and beyond the requirements.

Add laminated glazing as necessary

Laminated glazing upgrade is available for compliance with Part Q (Security) of building regulations if required.

Upgrade glass options

Opting for triple glazing will improve the overall u-value to 0.7. This upgrade is available if needed but is restricted to panel sizes of up to 7.5m².
A solar control glazing upgrade which improves the g-value is available if needed.

Glass Specs

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What U-value do Minima sliding doors achieve?

Our Ultraline sliding doors achieve an overall U-value of 1.2 W/m²K with standard double glazing, which meets the current Building Regulations minimum. With triple glazing, the U-value improves to 0.7, and with triple glazing combined with solar control glass, it reaches 0.6. These figures represent the overall performance of the complete door system, including both the glazed unit and the aluminium frame.

Do I need triple glazing to comply with UK Building Regulations?

No. Our standard double glazing meets the current Approved Document L requirement of 1.2 W/m²K. However, triple glazing can be beneficial if your SAP assessment requires enhanced thermal performance to compensate for other parts of the building envelope, or if you simply want to future-proof your home against tightening energy regulations. It’s also a popular choice for properties in exposed locations or for homeowners who prioritise energy efficiency.

Will choosing the concealed track system affect thermal performance?

No. Both our concealed track system and our flush track system use the same glazing units, thermal break technology, and frame profiles. The U-values are identical regardless of which track configuration you choose — 1.2 for double glazed and 0.7 for triple glazed. Your decision between concealed and flush track is an aesthetic and installation preference, not a thermal one.

How do Minima sliding doors help prevent overheating in summer?

We offer solar control glass as an upgrade on both our double and triple glazed options. Solar control glass significantly reduces the solar factor — the amount of solar heat energy passing through the glass — without noticeably reducing natural light. For south-facing or heavily glazed rooms, we can also supply recessed blind boxes that fit flush with your ceiling line, providing additional solar shading when needed. Our team can advise on the best combination of glazing and shading for your specific orientation and room layout.

Do the doors require any additional thermal upgrades to comply with Part L of the Building Regulations?

No — the standard double-glazed Ultraline system already meets the 1.2 U-value requirement set by Part L as standard. If your project targets a higher specification — for example, Passivhaus or Future Homes Standard compliance — the triple glazing and solar control options can be used to achieve lower U-values.

Related Features

Modern living room with large windows and sofa showcasing 3 panes sliding doors

Visual Advantages

Modern living room with large skylight and plants.

Functional Benefits