A heavier wool duvet for a cold room

In short: A warm wool duvet from the heavier band, sized to overhang the mattress and kept fresh by airing, that can stay on the bed all year.

The band

	What to look for	Source
GSM	About 600 to 700 grams of wool per square metre	UK duvet tog guide
Tog band	12 to 13.5 tog for a room that gets cold at night with the heating off	Winter tog guide
Construction	Box stitching with corner tabs, so the wool cannot drift or bunch inside the cover	No figure stated
Size	Large enough to overhang the mattress on both sides; published king and queen measurements differ between sellers, so measure first	No figure stated; see how a wool duvet insert fits its cover
Care	Spot clean, air about once a month, machine wash only if the label says washable, and never tumble dry hot	Wool bedding care guide

Why the answers settle on this band

Your answer puts the bedroom below the quiz's cold line on winter nights. Rooms like that are common, and a nationwide survey of Japanese homes found winter bedrooms averaged 12.8°C. A winter tog guide matches a room that cold, with the heating off, to a duvet of 12 to 13.5 tog. Because your summers stay cool, that same duvet can stay on the bed all year without a seasonal swap.

Wool is not the lightest warm fill. The guide that supplies the 600 to 700 gsm figure notes that down is lighter than wool at the same tog, and how wool and down differ from bedtime to morning sets out what wool gives in exchange.

Airing and spot cleaning keep the widest choice open. One care guide states that most wool comforters are not washable. Needing a machine wash would have narrowed the field, for reasons set out in why most wool duvets cannot go in a washing machine.

For anyone who finds wool on the skin bothersome, the fill still sits inside a woven cotton casing, such as the sateen organic cotton shell on one published listing. If it does not, the shell can be chosen for its feel or weave.

What would shift the band

Warm summers change this result most. If your summer nights run warm, a duvet in this band will be too warm for months at a time. The winter tog guide warns that keeping its warmest duvet on year-round is likely to overheat a sleeper in spring and summer, and points to a set that splits into a lighter and a warmer layer. That is why wanting a single duvet and having warm summers pull against each other. If you are open to two, a light summer duvet can cover the warm months and be laid over the heavier one on the coldest nights. Owning a lighter and a heavier duvet walks through that setup.

Treat every wool tog figure as approximate. Makers convert gsm to tog in different ways, and their published conversions do not agree. The GSM to tog conversion shows why the two systems disagree.

Trying the weight on your bed

Put a thermometer beside the bed on a cold night and read it when you usually wake. If it stays warmer than the quiz's cold line, the same winter guide says a slightly lower tog is usually enough in a warmer or well-insulated room. On the label, the figure that matters is grams of wool per square metre rather than the total weight, since a larger size holds more wool at the same gsm. Then measure the mattress against both the duvet and its cover. Published king and queen sizes do not agree with each other, so a cover can end up loose or a duvet short. Last, confirm the care label. Washable wool has been treated so it can go in a machine, and untreated wool should be spot cleaned and aired instead.

Further on wool duvets

Back to finding your tog

Sources

Outside reading behind this wool duvet page, each entry marked with where on the page it is used.

UK duvet tog guide (scooms.com), used under “The band”; “Why the answers settle on this band”.
Winter tog guide (cuddledown.co.uk), used under “The band”; “Why the answers settle on this band”.
Wool bedding care guide (downunderbedding.com), used under “The band”.
a nationwide survey of Japanese homes (pmc.ncbi.nlm.nih.gov), used under “Why the answers settle on this band”.