Equinox is here, and things hang in the
balance.
This week is a great time to re-orient yourself to the cardinal directions and priorities.
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Amazing print done with a pinhole camera in Tijeras,
showing sun angles from summer solstice (high arc)
to winter solstice (bottom arc). From NOAA, 3/22/2015:
http://www.srh.noaa.gov/abq/?n=clifeatures_summersolstice |
For us, most projects are on hold due to Ernie being laid up with a cellulitis
infection in his bum leg. Instead of chopping firewood, he gets twice-daily IV antibiotics. We hope for improvement in
the next few days, but nothing's certain.
This sort of setback always makes me
reflective. Am I staying tuned to what's important,
or just reacting to what feels most urgent? (More on that below).
I wanted to put out this update today, somewhat urgently, because I think passive solar is very cool, and it's important, and it's easy to neglect planning for it until it's too late. This (the week of spring equinox) is is a good week to take some relevant observations.
You can do a lot of fancy math to figure out the optimal sun angles and thermal mass to match your heat loads. This site has a pretty great library of resources:
http://www.builditsolar.com.
However, nothing beats direct observation, and now is one of the key times to observe.
A solid equinox sun-path, and a second one (sun and moon) from close to the solstice, can let you skip a lot of the maths and work directly from your site data.
You don't want to stare at the sun directly, but watch how the shadows or sunny patch moves along the ground and floor and other objects. A vertical stick, or an angle wedge like the dial on a sundial, will make a shadow you can trace. If you already have a building, just watch the sunny patch from a window as it moves across the walls and floor.
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I made this papercut to watch its shadow trace the sun's path. |
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If you are modifying a building, adding a sunroom or whatever, you might rough in a frame and hang up some cardboard to represent the future walls and roof, so you can trace the patch from the future windows.
(The full moon is roughly opposite the sun, so a summer-solstice full moon traces a similar path through the sky as the winter sun.
You can double-check it six months later if time allows. Since most people only get a few solstices to observe while planning a building, and some of them might be cloudy, it pays to double up at each opportunity. The Stonehenge builders sank dozens of log post markers before placing the permanent stones. )
At equinox, March 21/Sept. 21, the sun rises due east and sets due west. If you are not 100% sure of the N/S axis of your property, this is one way to find it (not counting nearby hills).
Equinox also marks the average day length and
sun angles for every place on the planet. Winter days will be shorter, summer days
longer.
Summer sun
rises higher in the sky and traces a longer path. The winter sun
takes a shortcut, low across the sky. Shadows are longer in winter,
and sunbeams slant almost horizontally.
In the northern hemisphere, the summer
sun rises north of true East, circles clockwise across the southern
sky, and sets north of true west. The winter sun makes a shorter
arc, from southeast to southwest, staying lower in the sky.
(In the Southern hemisphere, it's almost the same but swap the north and south directions: the sun still moves east to west, but counter-clockwise. Australian winter days are all north-oriented, summer days have a long SE to SW arc with a northern noon.)
In the equatorial regions, "summer" and "winter" may not mean much. Your temperatures stay closer to optimal year-round; tropical conditions warrant a separate discussion.
So in the temperate climates, where most people need heat:
We can orient windows and sunrooms to admit
more light in winter, less in summer, which is exactly what we want
in a temperate climate to offset our seasonal extremes.
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Sunroom: vertical windows let in more winter sun, less in summer |
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Skylight: lets in the most light, but more in summer and less in winter. |
If you are setting up a greenhouse or attached sunroom, it really pays to think about your goals.
Good insulation, thermal mass, and passive-solar sun angles can help you create a more moderate environment (protected from overheating and from frost).
Too much glass (not enough walls) can cause overheating in summer and heat loss in winter, but it does let in more light for plants.
Different plant species have different light requirements and tolerances for extreme temperatures, as do fish, poultry, and other common indoor-outdoor livestock.
The Bucket Test:
This week is a great time to get out in
your sunroom with a bucket or chalk and see where the sun actually
hits throughout the day. I like using a 5-gallon bucket because it's
about the right height for a seating bench. You want the winter
sun to hit that vertical face for best heat collection. So you want
to get the sides as well as the top of the bench into the sunny
spot.
If you place thermal mass along the
shady side of the sun/shade line, it will get some sun in winter, but
none in spring or summer.
If you place it a few degrees to the
sunny side of that line, it will get sun through about 3 seasons but
not too much in summer.
You can also do this test with a camera
– set up a tripod or put the camera on a ledge, and take a picture
every 2 hours or so from sunrise to sunset. Makes a good record that
won't get messed up as you build things.
Our clients in Chehalis are doing this
in preparation for adding a rocket bench to an indoor/outdoor patio
space.
Speaking of Chehalis, please check our
schedule for upcoming workshops. We have two in Canada and three in the USA between now and June. As a change of pace, we're
throwing in some natural building and plasters as well as rocketry at
the
Ecological Living Summit in Montana.
Please keep your fingers crossed that
Ernie's infection will resolve quickly and he'll be released to fully
enjoy these workshops. Since his 2008 injury, we pretty much
consider Ernie as a special volunteer, and any work he is able to do as a bonus.
We have delayed the Kickstarter launch
for the Rocket Mass Heater Builder's Guide because of this situation and
other reasons. Hoping the fallow time will turn out to serve its purpose, and there will be some benefits from it. For example more and better connections to help us, and I can keep working on more rewards to offer as incentives once we do go live.
So if you'd like to help, and have good resources to spread
the word, please remind me that you're interested. questions@ErnieAndErica.info
Yours,
Erica and Ernie