How to Insulate a Garden Dome
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Quick answer
Insulate around the clear shell rather than over it, so you keep the light. Start with the floor: insulation under the floor finish, a sealed edge and thick rugs. Then draw thermal curtains or blankets over the lower panels at night, keep draughts out, heat on demand with an electric heater kept well clear of the panels, and ventilate regularly to control condensation.
Start with the base: the biggest win without losing light
A dome loses heat through its clear panels, its floor and any draughts. You can't insulate the panels without losing the light, but the floor is the one surface you can insulate fully without touching the view, and it's the one you feel first. This is the highest-impact step:
- Insulate under the floor finish. When you prepare the base or lay decking, add insulation beneath the floor build-up so warmth isn't lost into the ground. Our guide to garden dome flooring options covers the choices.
- Seal the perimeter. A well-fitted base with no draughty gaps around the edge keeps cold air out and warm air in.
- Add a quality floor finish. Insulated flooring, then a thick rug or two, makes an immediate, felt difference underfoot and to the whole space.
Get the floor right and you've solved a large part of the comfort equation before you've spent a penny on heating.
Be realistic about the shell
It's tempting to think a thicker shell is the answer, so here's the honest picture:
- Polycarbonate isn't an insulator. A clear polycarbonate shell lets heat out readily on cold nights. That's the trade-off for a room made of daylight, and it's why the floor, curtains and heating do the work of keeping a dome warm.
- Thicker panels are about strength, not warmth. Ultra (panels 30% thicker than Original) and Extreme (panels twice as thick as Original) add strength and weather margin for windy, coastal, exposed or high sites, but they won't turn a dome into an insulated room. Choose your specification for your site (see Original vs Ultra vs Extreme) and plan for warmth separately.
Retain warmth with furnishings and habits
You keep the light and the warmth by managing the space rather than boxing it in:
- Soft furnishings. Rugs, throws and cushions take the edge off cooler surfaces and make the dome feel instantly cosier.
- Thermal curtains or blankets on the lower panels. Drawn at night, they reduce heat loss through the panels when there's no view to lose; pull them back in the morning to let the daylight in.
- Control draughts. Keep the door and windows closed while you're heating, and check the base edge and the door for gaps.
- Heat on demand. A thermostatic electric heater, the simplest choice, warms the space quickly, so you don't need to heat it constantly (see how to heat a garden dome). Keep any heater well clear of the panels, curtains and soft furnishings. A fuel-burning heater needs ventilation and a carbon monoxide alarm, and a wood burner needs a HETAS-registered installer, a proper flue and the clearances the installer specifies.
- Balance ventilation. With electric heat, keep the roof vents closed while you warm the space and open them periodically to clear moisture (our condensation guide explains why); with a fuel-burning heater, keep ventilation open throughout.
What not to do
Resist the urge to line the whole shell with opaque insulation. You'd lose the daylight and the view that make a dome special, turning it into an awkward box. The dome is designed to be enjoyed bright: the right strategy is an insulated floor, curtains on the lower panels at night, draught control and sensible heating, not covering the shell.
Frequently asked questions
How do you insulate a garden dome?
Insulate under the floor finish, seal the base edge and add thick rugs, then draw thermal curtains or blankets over the lower panels at night, control draughts and heat on demand with an electric heater kept well clear of the panels. Ventilate regularly to keep condensation down.
Where does a dome lose its heat?
Through the clear panels, because polycarbonate isn't an insulator, and through the floor and any draughts. You can't insulate the panels without losing the light, so insulate the floor, keep draughts out and draw curtains over the lower panels at night.
Do thicker panels insulate better?
Choose a specification for your site, not for warmth. Ultra and Extreme panels are thicker for strength and weather margin, which is why they suit windy and exposed sites, but neither turns a dome into an insulated room. For warmth, rely on the floor, curtains, draught control and heating.
Can I insulate the panels themselves?
Not without losing the light and the view. Thermal curtains or blankets on the lower panels, drawn at night and pulled back by day, are the sensible compromise; keep them well clear of any heater.
Will curtains help keep a dome warm?
Yes. Curtains and blinds reduce heat loss through the panels at night, while rugs and soft furnishings make the space feel warmer underfoot and cosier overall.