Unlike sleeping bags, which can be tested using a European Norm (EN) or ISO test protocol, there is no standard for temperature testing of quilts.
All quilt temperature ‘ratings’ are therefore estimates.
Sea to Summit calculates temperature recommendations for quilts based on the weight of down or synthetic-fill used, compared to a similar Sea to Summit sleeping bags.
The Lowest Comfort Temperature is the lowest temperature at which we believe an average sleeper will still sleep comfortably. The Functional Limit is the lowest temperature at which a quilt could be used – it is below the threshold of what most users would regard as comfortable.
These recommendations assume a sleeping mat with a tested R-Value appropriate for expected ground temperatures – without this, the quilt itself is unlikely to keep the sleeper warm enough.