Keeping Your Extension Warm This Winter

When you invest in an extension from Whalley Home Improvements, you’re not only adding valuable living space, you’re also creating an opportunity to enhance comfort, efficiency and home-life all year round. But come winter, the very extra space you’ve added can feel cold and under-used unless it’s built and treated with warmth in mind. Here are key practical steps to ensure your extension stays cosy, efficient and welcoming, even on the chilliest Lancashire days.

1. Get the insulation right

First and foremost: good insulation is the foundation of warmth. In your extension’s walls, floor and roof, make sure you use high‐quality materials with a good thermal rating. Cold air in Lancashire easily creeps in where insulation is inadequate. For example:

  • Walls: Use cavity wall insulation or fully filled stud walls with insulation board or batts.

  • Floors: If your extension has a new floor slab or suspended timber floor, ensure insulation under the slab (e.g., rigid foam boards) or between the joists.

  • Roof/ceiling: Especially if you have a pitched roof or flat roof extension, ensure you have sufficient insulation above the ceiling and/or underneath the roof deck.

Proper insulation minimises heat loss and keeps your energy bills in check — something any homeowner in Blackburn, Clitheroe or surrounding areas will appreciate on winter evenings.

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2. Choose high performance glazing and doors

As part of the extension design, the glazing and doors play a big role. Large windows and floor-to-ceiling glass look fantastic and bring in light, but if they’re low quality they’ll bring in cold too. At Whalley Home Improvements you have access to windows and doors from market leading suppliers — great—but here are things to check:

  • Double or triple glazing with a low U-value (the lower the U-value, the better the insulation).

  • Frames with good thermal break and sealing to prevent drafts.

  • Doors that seal tightly and have insulated cores.

  • If you have large glazed sections (glass extension or house extension style) consider thermal panes with inert gas fill (e.g., argon) and warm edge spacer bars.

By combining superior glazing and properly sealed doors, your extension will retain heat much better, and you’ll avoid the “glass room which feels cold in winter” syndrome.

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3. Underfloor heating or efficient heating distribution

When it comes to actually keeping the space warm, how and where the heat is delivered makes a difference. For extensions, especially where you might have open plans or large floor areas, underfloor heating is an excellent choice:

  • Underfloor heating spreads warmth evenly across the floor, warms people and objects (not just the air) and works well with lower-temperature heat sources (which tend to cost less).

  • If you already have radiators or plan to use them, choose high-efficiency models and make sure they’re placed under windows (where heat loss is largest) so their effect is maximised.

  • Use a thermostat zone for your extension so you’re not heating the rest of the house unnecessarily when it’s mostly used independently.

In Lancashire’s winters – when outside temperatures drop and you want your new extension to feel as comfortable as the rest of your home – efficient and effective heating is key.

4. Ensure airtightness & good ventilation

A warm extension is not just about putting heat in — it’s also about keeping unwanted cold air out, and controlling moisture/ventilation.

  • Airtightness: Ensure joints, connections between new and existing structure, frames, door thresholds, and the floor-wall junction are sealed properly. A wind-driven draft in an extension can dramatically increase heat loss.

  • Ventilation: While airtightness improves warmth and reduces energy waste, you also need to ventilate properly to avoid condensation and dampness — particularly if your extension will be used as a living space, kitchen-diner, or family room. Mechanical ventilation with heat recovery (MVHR) systems or simple trickle vents with proper humidity control can help.

  • Thermal bridging: Pay attention to places where materials meet (wall-floor, floor-glass, roof-wall). These can become thermal bridges and allow cold transfer through structural elements unless they’re broken or insulated properly.

By making sure your extension is well sealed yet ventilated, you’ll enjoy a warm, healthy space that works in winter and summer.

5. Choose the right finishes and smart usage

Finally, some of the lower-cost but still effective steps:

  • Floor coverings: Choose carpets or rugs in living areas which add insulation (versus bare cold tile or stone floors).

  • Window treatments: Even with high performance glazing, consider heavy curtains, blinds or insulated shutters to add another barrier when the sun has set or the temperature drops.

  • Smart controls: Use programmable thermostats or smart heating controls so the extension is warmed just when you use it — no need to heat when it’s empty.

  • Use the space: The best way to keep an extension warm is to use it — every time heat is used, it stays warmer for longer. So plan your usage (family room, dining, workspace) and ensure the layout supports everyday use in winter months.

6. Work with trusted installers and suppliers

Since extensions are a significant investment, it’s vital you work with experienced professionals who understand both structural and thermal aspects. At Whalley Home Improvements we specialise in bespoke extensions across the Lancashire area—Clitheroe, Whalley, Burnley, Blackburn and beyond. Our team ensures correct insulation detail, high-quality windows/doors, and full project management so your extension performs well in winter as much as summer. Whalley Home Improvements

In summary

A well-designed and built extension should feel as warm and inviting in December as it does bright in July. By focusing on insulation, high-performance glazing, efficient heating, airtight construction plus smart finishes and usage, you’ll get the full benefit of your new space throughout the year.


Ready to transform your home in Lancashire into a comfortable and energy-efficient space? Contact Whalley Home Improvements today to discuss how your extension can be built with winter warmth in mind.

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