Down volume (calculated loft)
The amount, or volume, of down in any given area is one of the critical elements of insulation, and the foundation for assessing performance. This section measures the total area of each system and then uses total fill weight and fill power to convert to a useful per-area down volume (calculated loft). Total fill weight is multiplied with fill power to find total down volume, which is divided by total area. If the measured total item weight is near the advertised weight, we trust that the advertised total fill weight is accurate for this conversion. If this weight is off from the advertised amount, we open one or two chambers to measure down volume per chamber and convert to per-area down volume. Select different sleep systems to compare side by side, or use the "Your system" columns to measure and compare your own. You will need to physically have the system you wish to measure and find its advertised total fill weight and fill power, then follow the tutorial to measure the rest.
Practical and accurate performance assessment of down-filled systems
The outdoor industry typically gauges insulation performance using total fill weight and fill power to calculate total down volume. Being a measure of quantity, it is a partial view of performance aspects and it fails to view that part accurately, given that the total area that amount is being spread over remains undefined and known to be highly variable. This project seeks to obtain systems, define their total area, convert specifications to a useful per area down volume (calculated loft), measure the remaining performance aspects, and outline a practical procedure that others can use in the future.
The Elements of Insulation Performance
Data Collection
There are three tabs for the three elements. This is an overview of the data in each tab.
In the Down volume (calculated loft) tab, you will find lots of information about each system, some of which is from advertised specs and some of which is measured by us. While this page contains a range of information that we will use in other places, the main objective of this page is to define the total area of various systems so that we can convert total amounts into per area down volume (calculated loft).
In the measured loft tab, you will find physical measurements of chambers and structures. The main objective of this page is to define the dimensions of baffle height, peak measured loft, and chamber width for each system so that an average measured loft can be roughly defined.
In the system losses tab you will find a 1 - 5 rating scale applied to various design aspects that might contribute to extra heat loss.
These measurements are intended to improve consumer's ability to compare and assess warmth. Current methods can be extremely inaccurate and misleading. The methods outlined here remove very large errors and fill in a lot of absent information, but it should be known that they aren't likely to always perfectly define performance. There are many, many elements involved with insulation and a few numbers cannot possibly tell the whole story. This project is intended to tell as much of the story as possible so that there is significantly less guesswork involved.
Measure your own
Add your own quilt to the comparison and carry the project forward.
In the Down volume (calculated loft) tab, you will find an interactive option to measure your own system for comparison. A tutorial will outline how to measure the area and baffle height of your system and the page provides a calculator for you to enter those dimensions. If you enter the total fill weight and fill power of your system, it will provide your per area down volume, overstuff percentage, and more.
FAQ
Measured loft
Down volume (calculated loft) indicates how much down there is. Measured loft indicates how much loft height it is allowed to reach. Low baffles and narrow chambers can hold a set down volume low and dense. High baffles and wide chambers can allow that same amount to expand to higher loft and lower density. Higher loft and lower density from a set amount is warmer, but low density can lead to a lack of fill control. Lower loft and higher density is not as warm but provides more control. A balance, catered to the use, is ideal.
Where each quilt lands
Each chart plots per-area down volume (calculated loft) against another number systems get judged by. The point is to see where those numbers agree with per-area down volume and where they pull apart.
System losses
This page looks at design aspects that can lead to extra heat loss, on top of the general insulation. Down quantity and measured loft give you a picture of the R-value for any given section of a system. From there, assessing the end performance is a matter of looking at design elements and how they help or hinder that insulation. For instance, you could have an R-value that is off the charts, but the system will still be very cold if the heat held by that insulation is lost through drafts or other inefficiencies. Assessing elements like this is inherently subjective and should be treated as educated opinion, based on experience and trends.
Scores
This page gathers the data from the three main elements in one place. Down volume (calculated loft) indicates how much down. Average measured loft indicates how high that amount lofts. System losses indicate how well the design elements hold heat in. Grouped by temperature rating.