Frank wrote:
> Thanks for the reply...I think I understand it better now:)
> However I am a bit confused. I'm not clear on the shading part.
>
> The eaves are fixed , and the glass vertical in my application. So what
> happens happens or are you saying you should try as best you can to
arrive at
> a suitable compromise depending on your climate ?
It looks like something is missing in the second part, so I'll have too
wing it a bit. I assumed that your eaves were fixed and the glass
vertical, that makes it easier. I assume you are talking about eaves on
the south side of the building; it gets A LOT more complicated when you try
to do it for the east or west sides.
As for how the shading works, let me try it this way. As the sun gets
higher in the sky, toward summer, the sun doesn't shine into the house as
much, also the eave is shading more and more of the window. (You can
picture the large spot of sunlight shining deeply into the room in winter
and slowly over the next few months the sun spot narrows and moves closer
and closer to the window.) You want the sun to stop coming through the
window at approximately the date you have chosen based on heating needs in
your area and for your house. This eliminates solar gain through those
south facing windows during the warmer months.
The compromise you need to make to choose that date is on how to balance
the date you want to have the sun stop coming in at a certain time in the
spring (because you no longer want the solar heat) and the date you want to
have the sun start coming in at a certain time in the fall (because you
want the solar heat). In most areas the heating season (say October to
April) doesn't exactly match the solar seasons (remember that the sun is at
the same angle in the sky about March 20 and Sep 21 (and therefore also the
ends of Apr/Aug and May/July). In April (or March as in our area) you may
still want the heat, but in August (or Sep, or even Oct in our area) you
may not want it yet. You'll have to compromise on the pair of dates that
work best for your heating needs.
Once you choose your dates (a pair of dates, spring and fall, when the sun
is at the same angle and therefore the dates are the same number of days
from the summer solstice) you need to figure the sun's angle (only one) for
those dates. If the angle from the bottom of your eave to the bottom of
your window is the same as the sun's angle for the dates you picked, then
the eave will shade the window completely during the non-heating season you
chose, preventing the house from getting unwanted solar gain.
> I was hoping for a real simple answer like make the eaves a minimum of two
> feet etc.
If only things were always that simple : ) There are many variables,
different for each situation, as seems to always be the case.
> Further if I elect to go with a very steep roof pitch to get more space
in the
> loft area won't that effect that angle. I don't have to match everything up
> perfectly...just get as close as I can.
You have brought up some of the variables. Given a fixed eave overhang
distance, a steeper roof pitch will change the angle that the sun will or
won't come into the house. The trick is to pick your roof pitch first,
then make the eave work with the windows. More or less overhang in your
eave, raising and lowering the bottom of the eave (with a different width
facsia board, or actually building the wall roof intersection differently,
differnent wall height, etc.), and raising or lowering the window will
allow you to get the angles you want. Remember that BOTH the winter
solstice angle AND the angle you chose for spring/fall must work with your
design. You may need to fudge a bit in the end, just do the best you can.
> Since we are building from scratch and trying to design a low
maintenance, eco
> friendly home I'd appreciate hearing more about systems like radiant
heating,
> insulated concrete etc.
I like the way our radiant heating has worked this winter, but if I ever
built again I would keep things very simple, even primitive, because I'd
like to be able to make all of it and fix any of it myself and not rely on
factory made parts. To me this means passive, perhaps simple active (I
think thermosyphoning has great potential) , solar design with wood back
up. I know you aren't too interested in the work required with wood,
although I like the idea of an efficient masonry mass stove that burns
stick wood (from fruit prunnings and copiced fuel wood trees, not logs)
which would be a lot easier to work with. [Has anyone out there heard much
or done much with these kinds of stoves?]
> Timber frame was my first preference..but it seems too
> costly. And adobe or strawbale in the humid southeast doesn't excite me.
Where does that leave you?
I've been in your shoes, so I know how much there is to figure out if you
want to do as good a design as possible. Remember one of the rules in
Permaculture is to make many small trials and learn from your mistakes. I
would recommend that you build something small and not so critical in a
method you think has potential and learn on that project before you build
you main house. Good Luck.
Eric:
