This article refers to overfill in quilts and sleeping bags, however only the word quilt is used.
What is it?
In most cases overfill is an optional feature presented to buyers during an online purchase of a semi-custom quilt. For some custom quilts the overfill amount and the precise placement can also be individually selected.
Other makers include overfill as a standard, non-optional feature. In this scenario yet additional overfill is typically not available.
The notion ‘overfill’ refers to a base quantity of down receiving a request for extra fill. This base value, prior to overfill, is the minimum down amount a cottage manufacturer deemed necessary to ensure comfort or survival at the stated temperature rating. The consumers trust in this rating can influence decisions about overfill.
When researching a quilt purchase one should be able to determine the fill weight in addition to size representations. Comparing these numbers between brands will help interpreting whether a manufacturers rating is towards the ‘comfort’ or ‘survival’ end of the scale. This info is helpful when considering either custom or non-optional overfill. (It is assumed US cottage companies do not test to the EN/ISO standard)
Since overfill is added without otherwise altering the quilt, the down volume becomes denser; as opposed to a warmer rated quilt which will have design changes to accommodate increased fill.
Why do it?
Overfill added to quilts perceived as ‘survival’ rated can increase the performance incrementally. It is questionable if a ‘comfort’ rating can be reached without reworking the baffle (loft) size.
If choosing a quilt that is trending towards a ‘comfort’ rating, adding overfill can still be beneficial by:
Boosting the temperature rating a couple of degrees with minimal weight gain
Further locking the down in place, thus limiting bald spots. Helpful for persons with an active sleep pattern.
Maintaining long term loft by anticipating down degradation. Back to back thruhikes?
Maintaining short term loft by resisting compression and moisture impacts
Why not do it?
What if too much overfill is added; wouldn’t it just make things heavier, costlier and actually lower the insulation value? Theoretically yes. But to reach this point a large quantity of down must be added; an experienced down worker would see numerous red flags before arriving there.
For a ‘comfort’ rated quilt an overfill of 5% over the base is a common custom feature. Focusing this in the foot section could benefit many users. 10-15% overfill would represent a practical and economical maximum. More can be added for certain effects, but a better strategy would be a move to a warmer rated quilt.
The cost of overfill is sometimes high. Here’s why: Certain quilt designs can have 20-30 closed baffle chambers of varying sizes and body mapped insulation priority. The quilt may be available in 60 size combinations in four temperature ratings with two types of down for each. To add two ounces (57g) of overfill effectively and in the right places will take time and care.
Overfill for Nunatak products
Our quilts are rated for 'comfort', a condition that describe the feeling a user should experience at the stated rating if the criteria outlined in this article is met.
Still, a quilt can benefit from a bit more down, as mentioned above. In our selection menus under each down product is a tab with several levels of overfill available. The choices can look like this:
In each case we determine the correct amount to add based on quilt size, rating, down type and potential customer input via email, phone etc. The increase in fill weight should not exceed 10-15%, and only reach this level if the last option is selected.
A medium size Arc UL in the 20°F rating contains 434g of down at base level.
In the selection menu a customer can choose between HyperDry (treated) and regular down.
Then overfill in the foot section is selected. This part of the quilt has 85g of down. The customer has communicated via email a strong tendency for cold feet, so we add the full 15% (12g) in a pattern that focus the bulk where the toes will end up.
This will keep the down better locked in place, thus minimizing the risk of cold spots. Additionally the foot section will have received a slight boost in warmth.
Now the total down volume has increased to 446g.
Such are the levels of customization when every product is built to order!