Cooling in a passive solar house?

levsmith

Hey everyone, new guy here. So, somewhat of an introduction. I am 23, graduated college 2 years ago and now have a decent paying job. I lived on a farm all my life before college so I am sick of this apartment living. I am currently looking for land and I want to build an off-grid house.

Anyways, I have been researching solar for a year or so now and feel I have a pretty good understanding. So now I am thinking about house plans but have a few questions. I have read that passive solar houses have lots of windows on the south side and very few if any on the north. I would like to have passive solar heating because most of the land around here is farmland, so not many trees for a wood burning stove.

I also see that one good thing about passive solar houses is that the sun provides most of the light for the house. But my question, wouldn't it be pretty warm in the summer time? My parents usually shut the south windows and curtains in the summer and open up the north windows since the air on the north side of the house is shaded and cooler.

I guess I am just trying to figure out how these passive solar houses stay cool in the summer time. I realize that there are vents of some sort in the roof so there is good ventilation but around here, if you open up the south windows during the summer time, it feels like a blast furnace in the house. Sorry it has to be so long, just couldn't figure out an easier way to explain it

Cariboocoot

Re: Cooling in a passive solar house?

Welcome to the forum.

You have a decent paying job? How do you get one of those? Come on; tell us!

As for cooling a passive solar house ... can I let you know next year when I seriously start attacking the problem? My "new" house has passive solar and there is some serious interior temperature rise in Summer, despite the severe change in sun angle. There are "blinds" which are supposed to exclude the heat, but mostly they exclude light and heat up themselves. I don't think the system was well-thought out.

It might be preferable to use solar heaters rather than windows. That way they can be blocked as needed. Also some chimney cooling could be incorporated. You can get a ton of ideas like this at one of my favourite sites, Build-It Solar: http://www.builditsolar.com/

Me, I'm thinking about pergolas, exterior blinds, awnings ... something. The greenhouse is another disaster: +50C in the day, -5C at night. Oh the joys of Cariboo temperature extremes! Be glad you don't have -40 Winters. At least I do have a wood stove to keep the chill off.

levsmith

Re: Cooling in a passive solar house?

Cariboocoot wrote: »

Welcome to the forum.

You have a decent paying job? How do you get one of those? Come on; tell us!

As for cooling a passive solar house ... can I let you know next year when I seriously start attacking the problem? My "new" house has passive solar and there is some serious interior temperature rise in Summer, despite the severe change in sun angle. There are "blinds" which are supposed to exclude the heat, but mostly they exclude light and heat up themselves. I don't think the system was well-thought out.

It might be preferable to use solar heaters rather than windows. That way they can be blocked as needed. Also some chimney cooling could be incorporated. You can get a ton of ideas like this at one of my favourite sites, Build-It Solar: http://www.builditsolar.com/

Me, I'm thinking about pergolas, exterior blinds, awnings ... something. The greenhouse is another disaster: +50C in the day, -5C at night. Oh the joys of Cariboo temperature extremes! Be glad you don't have -40 Winters. At least I do have a wood stove to keep the chill off.

As far as the job, I really got lucky! Happened to get an internship in college and got full time after college.

I'll take you up on the offer of telling me next year, as long as I dont have to remind you

I LOVE builditsolar. It has been in my bookmarks longer than anything else! Sooo many ideas. I could stay up all night just browsing that site!

Thanks for the response. Hope to hear more about your new house once the right weather comes around.

niel

Re: Cooling in a passive solar house?

welcome to the forum.

that's an easy answer for it's all in the angles. in the summer the sun is overhead and in the winter it is lower to the horizon. an awning or overhang type of arrangement, be it permanent or adjustable, would allow the lower winter angles to pass while blocking higher summer angles. if the summer sun in the early morning or late evening bother you as the angles are lower to the horizon, then shutters or even an awning type arrangement turned sideways on the sides of the house works to block the solar radiation. this is, of course, on south facing windows for the sideways awnings, but shutters are great to have as it can block undesired light and add insulation to the windows if need be. do not have any infrared coatings that blocks the infrared radiation on south facing windows or you won't have any solar gains in the winter, but you can do this for windows that face east, west, or north. east and west will only receive strong sun during warmer months and it should be blocked. during the winter the sun doesn't reach these windows with very much intensity to make any real solar gains, but losses through them from the interior to the exterior should be blocked making the infrared coating good to have on these and the north facing windows.

the light is another story as solar light will allow some infrared radiation into the house even if it is only diffuse sky radiation. how much infrared will be acceptable to you to be allowed in is a good question and may depend on how much light you'll need too. the infrared coatings will help on windows that face east, west, and north, but are not 100% efficient on blocking it. it depends on many factors, but most of all what is acceptable to you after detailed calculations are done from the appropriate engineers, architects, etc. leaving you with the final decision that must be weighed against all scenarios even with electric lighting as one of them.

stephendv

Re: Cooling in a passive solar house?

Apart from shading, another technique is to build using thermally massive materials on the inside and then allow enough natural ventilation at night. This only works if there are big enough differences in temperature between day and night.

There is currently a german building standard called "passivhaus" which quantifies and sets some standards for building a passive house which you might find interesting: http://passipedia.passiv.de/passipedia_en/

waynefromnscanada

Re: Cooling in a passive solar house?

Not sure where you live levsmith, but where I live in North-Eastern Nova Scotia, summer heating is not a problem from my South facing windows, as the sun rises and sets to the North of my passive solar house, and during the day, is high overhead and does not enter those windows at all. During late Summer and Fall however, as the sun starts it's Southward journey, daytime heating was a problem. Was. I've now installed two sets of venetian blinds on each South window. One set is sun (and thus heat) reflective white, which I lower and adjust to let in enough light, but block direct sun/heat, while the other set is very dark, almost black, which can be lowered and adjusted to control the brightness entering the room, and at the same time, they get hot in the sun and when adjusted to an inward, upward slant, pour that heat into the house without fading all the photos on the walls.
There is a lack of solar hear come Spring however, as the sun's travels are always ahead of the season, so is high up overhead once more and no longer coming in the windows. I have NO openings or windows on the North end, and no Summer afternoon heat gaining windows on the West side. I can also tell you that come Winter, no matter how cold and windy the day, the inside temperature, with no other heat source, easily hits 90*F. Often even on those days, a window will have to be opened to make it livable, but if I can stand the heat, it's a great fuel saver as even though the sun may be long gone and the outside world dark before 4 PM, it's 10 PM before I even have to think about lighting the wood fire. This Winter will be a learning experience for me as I'm adding 3 inches of Enerfoil , insulation to the outside of the house, adding another R18.6 to the walls, bringing them up to R40. Last year the attic insulation was doubled to R80 and that definitely made a difference. I expect that by the time it's all finished, my winter fuel consumption will have been halved. And it wasn't a lot to begin with. We have to be prepared for the worst and I totally applaud your way of thinking and wish you all the best with your projects!
www.iko.com/products/commercial/commercial.asp?task=BuildingEnvelopeProductDetails&commercial_product_family_id=&commercial_product_id=519&commercial_region_id=3
Oh, I see late that you live in Kansas, so my info re the sun's Summer location won't apply to you and you'll have to use shading of your South facing windows.

levsmith

Re: Cooling in a passive solar house?

Thanks everyone for the replies. Now I understand a little better how they work. I'll have to do a little more research and see what other questions I can come up with now

icarus

Re: Cooling in a passive solar house?

One very simple design element is roof angle. By calculating roof over hang you can incorporate an eave that shades the house, particularly the glass in the summer, but allows full sun in the winter. Augment this with seasonal plantings that provide seasonal shade and. You go a long way to reducing heat gain in the summer.

Also, partial earth sheltered designs take advantage of temperate earth temperatures to keep the building cooler int he summer, warmer in the winter. In the real world, do some home work, and see where your biggest energy use is,, heating or cooling, and design to maximize efficiency with this balance in mind.

Also keep in mind thermal mass will help hold heat in the winter, but it can also, if well designed hold "cool" in the summer.

Tony

Cariboocoot

Re: Cooling in a passive solar house?

The overhead shading is where the mistake was made with my house; the end wall faces South-West and has nothing to shade it. Consequently it gets too much afternoon sun in Summer, and drives the temps up in that end of the house. Otherwise it was sensibly done: a rancher on the compass diagonal. Long front wall faces South-East and picks up sun from morning on (big windows). Long back wall faces North-West and is always shaded, small windows. For the most part, a thermally controlled fan in the kitchen drafts air through from the cool side and keeps the place comfortable - save that South-West facing room. If I were to close that off it would heat up like an oven!

Just a few minor adjustments needed. :roll:

mikeo

Re: Cooling in a passive solar house?

The overhead shading is where the mistake was made with my house; the end wall faces South-West and has nothing to shade it. Consequently it gets too much afternoon sun in Summer, and drives the temps up in that end of the house.

This is where some strategically placed deciduous trees placed to shade the west side in the summer and allow sun in the winter when the leaves drop. A passive solar house in not necessarily compatible with solar PV production unfortunately. In the South central area where I live humidity is the big problem. With out AC, it would not be bearable because everything grows mold and mildew in the summer. Even so my electric usage is less then 65 dollars a month on average for an all electric home, which includes pumping and treating well water. It has been hitting over 100 F up to 115 F until the last couple of days for over a month now. It will be interesting to see what my next months electric bill will be. I keep my earth berm-ed 1200 sq/ft house between 78 and 80F which is enough to keep the humidity around 50%.