Extension Heating

Seamless warmth, zero thresholds.

Adding a rear or side extension is exciting, but integrating its heating with the original house is notoriously difficult. Underfloor heating raises the floor heights and takes weeks to install. ThermaSkirt provides radiant comfort that bridges the old and the new perfectly.

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Skirting Board Heating for Extensions

ThermaSkirt is a low-temperature (35-45°C) radiant heating system tailored for complex extensions. Unlike wet underfloor heating which requires pouring tonnes of concrete and raising the extension floor level by 15-20mm above the original house, ThermaSkirt installs entirely above ground, keeping your thresholds perfectly flush.

Construction Hurdles

The Problem with Mixing Systems

If your original house is heated by standard radiators, attempting to add underfloor heating exclusively to the new rear extension creates a hydraulic battle. Gas boilers deliver water at 70°C for radiators, but UFH strictly needs 45°C to avoid cracking the screed. You are immediately forced to install expensive blending valves, manifolds, and secondary pumps.

Furthermore, relying on two fundamentally different heating methods causes immense comfort issues. Your radiator-heated living room boils over in 20 minutes while the UFH in the extension takes hours to warm up. ThermaSkirt unifies the system. It connects directly to your existing radiator circuit and operates with the same ultra-fast responsiveness as a steel panel, heating the entire open plan space evenly in 15 minutes.

ThermaSkirt Deco BM3 with Torus Capping installed in a new extension on tiled flooring

ThermaSkirt Deco BM3 in an extension with patio doors, showing external corner detail on tiled floor

Bi-Fold & Patio Doors

Fighting Heat Loss at the Glass

Modern extensions are dominated by massive expanses of glass. Aluminium bi-fold doors are stunning, but they create a wall of intense heat loss with zero physical space to hang a standard radiator underneath them.

ThermaSkirt’s intelligent perimeter design wraps the heat output down the sides of the extension and right up to the window frames. It can even be installed as a low-level threshold grille or integrated into step ups. By producing a highly reactive veil of 40°C radiant warmth exactly where the cold air originates, it prevents drafts sweeping across your newly laid floors.

"Every room is beautifully toasty and the top strip was replaced which makes the skirting look brand new."

Lisa Stevenson•Whole Home•

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Case Study

Extension Meets Existing Home, Seamlessly

Emma and Dan added an entire upper storey to their 1970s bungalow. Rather than battling with underfloor heating on timber joists or running mismatched radiators, they fitted ThermaSkirt throughout the new first-floor extension. It connected directly to the existing gas boiler downstairs, bridging old and new without blending valves or secondary pumps.

Emma & Dan's upper-storey extension - ThermaSkirt integrated with the existing boiler system.

Frequently Asked Questions

Everything you need to know

Do I need to upgrade my boiler for the extension?

Typically, no. Boiler sizing is based on the total kW output required by the house. Most existing UK boilers are drastically oversized (typically 24kW–30kW). Providing your boiler has sufficient remaining capacity, ThermaSkirt simply plumbs straight into the existing 15mm or 10mm pipework like a normal radiator.

How do I transition between the old house and the new extension?

If you have knocked a wall through, ThermaSkirt acts as a physical bridge. The aluminium profiles span across the old brick line seamlessly. We provide dedicated internal and external corner covers to wrap around structural pillars or changes in wall alignment.

Is it suitable for heat-pump ready extensions?

Yes. ThermaSkirt H2O is designed from the ground up for low-flow temperatures (35-45°C). By over-sizing the surface area around the perimeter of the extension, you guarantee your heat pump will achieve maximum COP efficiency.

Will it cope with the heat loss from 5 metres of glass bi-folds?

Yes. ThermaSkirt emits heat very effectively. By surrounding the perimeter of the extension and utilising the kitchen island, you deliver a massive surface area of warm aluminium into the room to counteract the glazing's heat loss. Heated threshold kits are also available for door openings.

Will it heat a large open-plan extension?

ThermaSkirt excels in large spaces. Because it runs along the entire perimeter, it provides an exceptionally even heat distribution that single point-source radiators struggle to achieve. BSRIA thermal imaging shows less than 1°C temperature variance across rooms heated with ThermaSkirt.

How do I go across doorways and openings?

We have a threshold kit that provides all the fittings needed to connect two pipes (not provided) hidden in the floor to a depth of around 50mm. This allows the flow and return to duck under door openings and continue on the other side. An Architrave Kit is also available that routes the pipework up and over the doorway.