Passive solar floor plan contradiction

I am new to this site so please forgive my ignorance. However, I am confused by the contradictory information I come across in my research. I live in a northern climate (Michigan) and heat is one of the primary reasons I am considering building a passive solar home.

I have read numerous books regarding designing a passive solar home. They suggest that you locate closets, hallways, laundry room, bathrooms on the north wall. They also suggest that you locate the most used rooms such as great room, dining area, kitchen, bedrooms, on the south wall to take advantage of the heat and direct light. This all makes sense. The contradiction comes in when they then state to make sure not to locate these rooms on the south because there will be too much glare because they become sun drenched. So what make the most sense?

Should I locate the foyer/entryway, stairs, bathrooms, hallways, etc. on the south wall or does it make more sense to locate the kitchen, great room, bedroom on the south wall? Is direct light that big of an issue or can sheers on the windows solve the problem when needed? Please advise.

hey bill,

welcome to the forums. it s a good thing that you are researching into this.

i m totally no expert. but my experience from our sunny flat is, that direct sunlight in summer is pretty harsh. we ve big windows facing southeast to southwest. we have quite mild summers, but on sunny days it gets very uncomfortably hot very soon.

if we use shades on the windows, it gets too dark to comfortably work/live in these rooms.

the contradiction is:

direct sun in winter = good
direct sun in summer = bad

the degree of that depends on your climate zone and your houses exposure to sun.

window shades are a good idea but i dont think, they work well alone.
other options to add to that are:

- growing trees to shade in summer. in winter they loose leaves and let light pass
- a porch covered with vines that loose leaves in winter
- large roof overhangs that block the sunlight in summer (sun coming from high angle) but let it pass in winter (sun coming from low angle). there should be websites to calculate that for your region

consider these things and then plan how you want to use your house and the specific rooms. consider light and temperature in summer and winter.

good luck and blessings
tobias

Bill,

Also a hearty welcome to permies!

I agree with what Tobias posted above, but especially the parts I'm quoting below:

Tobias Ber wrote:
- growing trees to shade in summer. in winter they loose leaves and let light pass
- a porch covered with vines that loose leaves in winter
- large roof overhangs that block the sunlight in summer (sun coming from high angle) but let it pass in winter (sun coming from low angle). there should be websites to calculate that for your region

consider these things and then plan how you want to use your house and the specific rooms. consider light and temperature in summer and winter.

For the northern climes, having that exposure shaded in the summer time definitely lowers your heat gain then and aims to collect that in the winter time when it is most valuable for you. Mr. Googlepants is your friend when it comes to finding sites to help you not only with roof overhang, but also the optimum glazing angle, the angle you have your windows located. I'm speaking of the vertical angle there. If instead of having them angled truly vertical (perpendicular to the ground), you add an inward pitch to them from the top to the bottom, this enhances your windows rejection of the heat in the summer month.

Good luck on your project and please keep us informed on your choices and what you find.

My father built two solar heated houses for himself. The first house had the bathrooms on the north side of the house. The second had them on the south side. In our northern cold climate, I much prefer having the bathrooms being on the south side of the house, and thus warmer.

Perfectly south-facing windows have much less of these glare and summer overheating problems than do windows that are SE or SW. The west side is especially annoying for overheating and glare, as sun comes in for a long time on hot summer afternoons. With the appropriate overhang over exactly-south windows, summer sun-drenching should not happen much. Add translucent white shades or drapes that you can pull when the glare annoys you, and I don't think there's much problem left.

I've lived in houses in a cold climate, heated only by passive solar, for the past 20 winters. We don't get overheating in summer from the windows, and in fact the sun barely shines in the windows in summer. I've noticed that houseplants on the windowsill don't get any direct sun for a couple of months. Granted, we're only 34* North, whereas you're probably above 40*N, so for us the sun is higher in summer and thus comes in the windows very little in summer. The summer sun will be lower at your latitude, but you can design for that with an overhang over the windows. Most of our houses are exactly south facing (that's solar south, not magnetic south, which is as much as 6* off in my region of northern India).

I'm very happy with the solar heating on my residential quarters, done by a greenhouse made of plastic, that we roll down and fix in November, and roll up out of the way from May through October. This means that all summer my south wall is just a normal wall with less than 50% of it as windows. In winter, I open the door and windows between the house and greenhouse all day to let hot air in, and then close them in the evening to keep the heat in the house.

We always design so that the rooms we spend time in are on the south, and keep the north of the building for entrance, storerooms, corridors, stairs, etc. Those northern parts often get very chilly in winter, though not down to freezing, but they make a very effective buffer so that the southern rooms have less exposure to extreme cold outdoors.

Our school has one small building with a trombe wall and no greenhouse. It is exactly south-facing. It seems hotter than my quarters, especially in autumn and early winter, and in fact overheats a bit in November and early December when everyone is wearing sweaters and doesn't want it so warm. It doesn't seem to overheat in summer though, as it's got a nice little overhang so that very little sun hits the glass in summer.

We also have some rooms that are called "glassrooms," a local modern tradition. At our school, these have 100% of the south wall glass, with no trombe wall inside, and then the glass wraps around a bit of the east and west wall as well. These are thermally uncomfortable! They overheat on any sunny or warm day, and get cold quickly on winter evenings. Big mistake, and we are gradually tearing them down and rebuilding them as trombe walls. They are very beautiful rooms but you can only really sit in them when it's cloudy, or in the mornings. Sometimes our volunteers from tropical places go in there and bask when nobody else can stand the heat.

I'm not so sure about deciduous trees and vines to make seasonal shade. I've noticed that deciduous trees still cast shade that makes a thermal difference. Snow that falls in the shadow of deciduous trees can last for days or weeks at our school, whereas it melts or evaporates in the first day, if in direct sun. So I'm reluctant to plant deciduous trees south of our buildings. I think they would significantly reduce the solar gain when you most need it in winter. But they'd probably be welcome on the west side, which is where the most uncomfortable overheating is likely to come from.

we're only 34* North

we too

The roof overhang can also be movable, supported by beams that cantilever out of the main structure.  

I had an idea to possibly with my own house build some home made detachable shading roof overhangs which were also wide removable gutters, since in winter the gutters tend to ice up or get broken and pushed off the roof from snow or ice sliding down the roof's slope.

Curtains that suit the purpose: The kitchen in our present home has very bright light coming in when doing lunch dishes; this also happens when taking a break with a book in a chair in the living room.  My mother created some nice curtains which do not block all the light, but reduce the glare significantly.  This allows the work or leisure space to receive light when you want it, while at the same time reducing glare so that it's tolerable.

There are lots of options in the curtain department, including multiple curtain rods with different curtains for different purposes.  For instance, a very thick insulating curtain could be drawn near the window after dark to keep the heat in and cold out and be right against the window, whereas a lighter set of curtains which block the glare (as in the kitchen or living room example above) could be on another rod projected by hangers a bit further into the room.

Glare is a fact of life in a passive solar home, at least it is in mine that I'm on my 3rd winter in.  Trombe walls could work but I can't share any personal experience there since I don't have one.  Summer sun is mentioned in the comments here but with good design that can be minimized or almost eliminated.  You probably already know to try to keep it fairly long and narrow East to West and of course the proper overhangs are critical.

Some of the finer design details:  Pay attention to finishes on floors, window sills, and furnishings.  My wife put a clear vinyl table cloth on the dining table and it bounces a bright glare into the kitchen.  Floors can be tricky since smooth and shiney is easiest to clean but relatively matte finishes help out.  We have a tall counter halfway through the house separating the dining from kitchen and this does deflect most of the glare from the floor.  Colors are important too.  As we know, dark colors absorb more and convert to heat while lighter bounces more light off.

Most passive solar architects now know not to over-glaze.  Just having a 5-6 ft wall section not glazed creates a nice pocket to place a reading chair or something in.  Of course the shaded areas farther from the wall shift throughout the day.  We have a living area with a ceiling that goes to the upstairs with the window up high.  This keeps the sun from that window mostly on a dark painted wall halfway through the house or upstairs.

Hopefully by next winter I'll be able to report back how an attached solar greenhouse impacts the performance.  We have section 12 or more feet long with no windows that will be inside the greenhouse, there's a doorway to one side and a double-hung window to the other that can let extra heat into the house if we choose to open them.  I imagine that the greenhouse will reduce the glare we currently get through the door since it will be diffused through the greenhouse glass first.

I see that someone mentioned various curtain arrangements but I can't report on that either since I don't have any yet!  Getting insulating window drapes to close at night should help out a lot though!

Nothing's perfect but I will say that I'm extremely happy with the performance of passive solar in my climate.  Over Christmas I was gone for 8 days and with no supplemental heat in MN I came home to 55 F downstairs and 60F upstairs!
Good luck!  Hope this helped!

As with most contradictions, neither is wrong for its particular application,but is wrong for another application. If the north wall is earth bermed is vastly different than a free standing wall. Planing the room layout is site and strategy specific. For your site and strategy what rooms can tolerate the heat/cool cycle and direct/reflected or ambient light.
So you asked a good pree design question. Now you want to apply the permaculture answer; make the problems solutions by design.

As part of my research for our house build this year, I am reading Anthony Denzer's The Solar House. Although a thick book of small print with technical stuff that usually makes my eyes glaze over, it is proving to be a fast and fascinating read. I'm glad we didn't design the house before reading it.

I grew up in sunny cold climate in a long E-W axis house with floor to ceiling windows. It is a hot box in the summer and too cool on cloudy winter days. The main rooms off the south side are too bright to read in even with honeycomb shades. Living here made me realize that I don't want to live IN the solar collector. I still live in that sunny cold climate, and my additional comments only apply to sunny places.

I am only halfway through Denzer's book, and as such may find more great info in later chapters, but right now, I wish we had found a piece of property with a great view to the north so we could put a Trombe wall on the south (with appropriate vents), and the main wall of glass to the north, protected by an enclosed porch of similar window design. (See the work of Arthur T. Brown for Trombe wall design.)

Northern light is fantastic for almost everything except getting out splinters. Some of the windows can be insulated with foam boards or curtains when it is really cold during the day while others are left open, and of course, all should be covered at night. A masonry heater or efficient woodstove can add much of the rest of the heat. I was frankly shocked at the thermal stability provided by the Trombe wall. I had discounted it long ago.

Good luck to us all!

Mostly you are trying to make it too complicated.  Passive solar has a set of keys.  1.  South facing glazing in proportion to square footage.  2.  Enough mass locate where the sun shines directly on it in winter.  3.  Home well sealed and well insulated.  4.  Some way to keep the sun out in summer.  Beyond those most of the other rules of thumb other people publish are trying to hard.

I have lived in an earth berm passive solar home with the sun coming in through clearstory windows for 30 years.  I will admit it is bright inside in winter.  For the most part though glare isn't a problem and you a quickly get used to it being bright.(so much so that you miss it when you go to other peoples homes)  This house does use auxiliary heat but in a zone 4 borderline zone 3 climate it burns less than 500 gallons of propane a year for a family of 4.  That runs the cook stove, clothes drier, water heater and all auxiliary heat.  Running without heat the house drifts down to about 50 degrees for the cold side of the cycle at which point the small amount of geothermal coming up out of the basement stabilizes it and it doesn't get any colder.  I have run clear through christmas without lighting the heater even when it was running 20 below most nights during Dec.  On bright sunny days it was still making the 70's for daytime highs.  With the heat running the house climbs into the 80's(heater stops at 72) on bright sunny days.  For the most part it takes 3 gray days in a row before the heater starts working much because the thermal mass lets the house coast that long.

As for glare at certain times of day in the winter computer monitors and tvs are hard to see and some chairs are hard to read a book in.  Otherwise it isn't really a problem.  Color choices help with this issue too.  High gloss bright white isn't the color of choice for your sun rooms.  Darker colors absorb better and have less glare.  The light green living room wall vs the brown bedroom wall with equivalent sun the wall in the sunlight pattern is 5 to 10 degrees warmer where brown.

As for putting certain rooms on certain sides of the home, I wouldn't worry about that as long as you can get the sun to shine on your mass.  The real advantage of a high mass passive solar is that the temperature is roughly the same everywhere in the house.  And if the house is tight there are no drafts.  If there is a draft here it means something is open.  Disadvantage is no place to warm or dry winter clothes.