What’s the R Value of a Duck?
AdamT
| Posted in General Questions on
I’m serious.
I see these ducks and geese on our pond in the winter. They seem to do fine when the temperatures drop below zero. The same for deer in our area.
They don’t have a lot of insulation (their coats and down aren’t that thick). If they were wrapped in polyiso, they would be R3 or so? Is their down/fat/fur better than Rockwool or rigid foam?
Maybe ducks are witches?
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This seems like the perfect question for ChatGBT to answer.
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It is all about the surface area to R value ratio. Small surface area, you need very little insulation to stay comfortable.
For example a human is about 20sqft area and puts out 600BTU walking. Say you want inside your coat to be 85F when 0F outside you only need:
(20 sqft * 85F )/ 600BTU=R2.8
So not that much.
A duck maybe a bit more R value, a deer a bit less but not far off.
The reason out houses need so much insulation is because of the large surface area. This is the one benefit of tiny homes, the smaller exterior envelope means even reasonable insulation can get you to near zero heating load.
This answer, by itself, is worth the full yearly cost of a GBA subscription.
Akos is on fire, even if he can't be assured that EVERYONE will agree that a spray-foam sweater would be dumb (ref #9). I hesitate to Google for such an image, fearing what I might find.
Agree, this is a thought provoking reply.
However, the volume-to-surface area ratio goes way down with these smaller animals. In cold climates, animals tend to get larger, which makes them more efficient at retaining heat.
I've often thought about this in terms of architecture-- how a cube, or better yet a sphere (probably a half sphere, i.e. dome, to meet with the ground) would be most efficient. And the larger it is the better the SA to V ratio.
However the SA to V ratio does not govern *heat* flow--ONLY area does. What the volume does (for an animal for instance) is provide thermal capacity. So it's definitely true that larger animals with low SA to V ratios will not cool off as quickly, because it takes more heat loss to lower that mass a degree.
But in architecture, do we gain the same benefit by decreasing the ratio? We may incidentally increase heat capacity (but not necessarily) and therefore the temp of the structure may not drop as quickly for a given heat loss, but because absolute surface area will have increased (assuming scaling up of an identical shape) we will have increased heat loss.
One metric that may matter more than heat capacity in this case is occupant capacity. An apartment will have more total surface area than most houses, but with far more occupants and therefore a greater occupant to surface area ratio.
Less heat loss per capita.
There's a guy named Buckminster Fuller you should read about.
Heat capacity is one of those things that intuitively seems like it should effect energy consumption. And that intuition is wrong. (And usually when people act on that wrong intuition they call heat capacity "thermal mass," but that's another story.)
Buildings are actively heated (at least in climates where we care about heating) and the rate of temperature loss doesn't matter, what matters is the amount of heat needed, the amount of fuel burned.
Perhaps another (over simplified) lens in which to view the benefit of a low SA to V ratio in an animal is that the larger animal has a larger heating system (more cells with mitochondria doing their thing). So they have both a greater thermal capacity and a larger heating system.
When applied to a house, this doesn't sound so good! We want smaller heating systems.
Part of my point is that if we are in any way to mimic the biological world in this regard, it should not be to seek lower SA to V ratios but to seek lower SA to occupant ratios. Or in the case of single family homes, simply minimize SA.
The key differentiation between large and small mammals (as far as climate goes anyway) is the ratio of surface area vs mass/volume. A mouse cannot survive any bit of time at -25 C outside, so they hang out at the ground/snow interface (or below) where temps are pretty much 0 C or warmer all winter. Bergmann’s rule I believe makes an attempt to summarise this. Polar bears have a much smaller ratio of surface area to volume, part of their toolbox for dealing with cold. My bio profs back in the day were all over this stuff...
Birds with the circulatory adaptions in their feet is a pretty fascinating topic all by itself. My other favourite is the glucose/blood adaptations of frogs that allow them to partially freeze.
What amazes me is that their feet are essentially uninsulated and sit in water that is near or at freezing all day long.
Ducks and other waterfowl don't lose much heat through their legs and feet because they keep them cold, just barely above freezing.
If they keep their feet in water, I think they would not freeze. They'd still be cold though.
Ducks have a unique circulatory system that helps prevent their feet from getting cold even when they are in cold water or on icy surfaces. The arteries and veins in a duck's legs are located close to each other, which allows for a heat exchange between them. When warm blood flows down from the body into the feet, the blood vessels in the feet absorb the heat from the warm blood before it is cooled down by the cold environment. The cooled blood then flows back up to the body where it is warmed up again.
This system is known as a counter-current heat exchange, and it helps to keep a duck's feet warm and prevent heat loss to the environment. In addition, ducks have a network of tiny blood vessels in their feet called "rete mirabile" which further help to regulate the temperature of their feet. This network of vessels acts as a heat exchanger, allowing the duck's blood to pick up heat from warm arterial blood before it reaches the feet, and transfer it to the cooler venous blood returning from the feet.
So in general, a duck's feet do not get cold because of these specialized adaptations that help them regulate their body temperature in cold environments.
Having said that, we had a very cold snap weeks back where the wind chill reached around 20 below. The neighbor lost a Guinea hen and two chickens have lost part of their feet. Of course, we're talking about ducks, not chickens or african swallows.
So do they also refer to this phenomena as "shrinkage" or is that just reserved for us Seinfeld fans of the male persuasion?
Don't forget -- for hundreds of years, duck farmers and goose farmers have saved duck down and goose down to make the warmest possible jackets and quilts.
So Green Building Advisor should really be renamed to 'Green Sweater Advisor.'
Just don't forger to be a a proper green sweater, it needs to be low embodied carbon, real hard core sweater should be made from a natural fiber.
A sweater, although it would be very effective, is also the one thing I think we can all agree on as a bad application for spray foam.
You might be surprised how warm that water under the ice can sometimes be. I have a spring fed lake on my land, and a number of small streams that feed into it too. Sometimes in near the end of winter, I have gone out in the marsh to work on some stuff and I have, on ocassion, fallen through the ice (I'm always careful to only ever be in the shallow spots). I've often been surprised how NOT cold that water can be! My guess is that the springs are feeding in 50ish degree water, which keeps the water under the ice a little warmer than you'd otherwise expect.
The swans that nest on our little lake returned this past week, and are currently frustrated that the lake is still mostly frozen over. They are scooting on the ice with their feet looking for little thawed spots to swim in. My guess is they are not real happy about that state of things at the moment :-)
Regarding those ducks, keep in mind that they have their own internal temperature control system. As the temperature drops, they'll use more energy to stay warm, compensating for the increased DTU (Duck Thermal Units) they lose through their outer body layers. Human bodies do the same thing, and you will burn more calories working in the cold than you will when it's warm outside.
Bill
Bill,
What is this "ice" of which you speak?
We had two days of ice skating this year - northern CT. It's the warmest winter on record per Bradley Airport's weather data going back to the 1950's.
Adam,
Yes, strange times!
Yet in Rhode Island we had the coldest day ever recorded, -10F.
Ha! It has been an unusually warm winter. Last year was much colder, and the year before I think came very close to record lows. This year I actually had to wait quite a while before things were frozen enough that I could walk on the ice in the shallows, and even then it make crunching noises. The interesting thing is I could hear gurgling under the ice in the area where some of the streams feed into the marshy part of the lake, which I've not noticed before when things are frozen, so I suspect it was just barely thick enough ice.
On a side note, there have been a number of beefy solar storms this winter, so maybe that's contributing to the unusual weather? A few of the solar storms have been quite intense, and there is a known link between energy released by those storms and weather patterns here.
Bill
I'm going to look for ways to use "Duck Thermal Unit" in a conversation.