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viracocha

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Posts: 7
Reply with quote  #1 
Hello,

I am going to build a house on my 1 acre of land. I want to design my entire house around the sun. My lot slopes south-west but have great southern exposure. I am going to be off-grid and I would like to do rainwater collection since the well would cost me a small fortune.

I want to build out of concrete.
I want a flat roof to hang out on.
I want a garage.
I want 2 story.
I need to afford it within a small budget.
I want to do as much of the work myself as possible.
I am trying to think of ways to incorporate water tanks inside of my house to store up water in the winter for use all summer long and use as a thermal mass.
I am located in a region that can get up to 8 feet of snow for 2-3 months out of the year.

I like this.
http://tinyhousetalk.com/tiny-surf-house/

I know that's not a lot to go on, but I was wondering what the best simple house designs based around solar that members have seen to give me ideas?

sundug

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Posts: 117
Reply with quote  #2 
Mine is a basic rectangle. I have built several concrete water tanks, and poured a flat roof over my root cellar. My home is based on a MEN "Sun Cottage" design- 
https://www.motherearthnews.com/green-homes/site-selection-passive-solar-home-zmaz83mjzraw

https://www.motherearthnews.com/green-homes/natural-building/passive-solar-house-zm0z14jjzsor

https://www.builditsolar.com/Projects/SolarHomes/Doug/DougsSolarHome.htm

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viracocha

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Posts: 7
Reply with quote  #3 
Thank you,

Any tips on figuring out the calculations?

1. At some point I want to sit down and calculate how much heat I can put into water via collectors and then how much volume of water I need to use as a thermal mass for space heating. I'd love to have enough water stored in tanks inside that is heated to keep the house warm for up a few days of clouds. Maybe with some sort of controlled radiant foil insulated vent so I can control the rate at which the heat exits my tank.

2. It would be nice to know how much window area that hits a thermal mass I would need per square footage of living space.

3. I am going to be putting hydronic heating tubes in all cement slab floors, even if they are just the garage because I figure I can run my solar heated water through them at any time in the future. And trying to keep my building small and simple to afford to build it but flexible for the future. Which is one reason I want post and beam construction so any interior walls are non-load bearing.

4. I am not looking to go subterranean that much. I have a gentle sloping lot but it's very rocky and I might even have to bring in dirt for the required by law septic system. Plus I like being up high.

unfortunately the south side where I need to have all my windows can get extreme and cold wind events so I will need to figure out shutters or some way of insulating them at night.

Do you use the concrete tanks for potable water? I still need to learn about how to keep my potable water clean and filters if I am storing it. I also have a lot of design things to consider such as an antifreeze loop for external collectors.
sundug

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Reply with quote  #4 
As you are in a cold climate south window area should be about 12% of floor area. There are a lot of variables figuring how much heat you need, can gain and store. As you want water stored heat for space heating, any temps above 80*F are useful. A lot depends on how well you seal and insulate the building enevelope. If you really want to start figuring collector and tank size, you need to start with heat loss, which depends on airtightness and insulation levels. There is no point in running heat into a slab that is poorly insulated, especially in your climate. You should have at least 4" of closed cell extruded foamboard under and around the slab. More is better.  I am using a concrete tank I built for my potable water tank. I poured the floor and walls, and used dri-lok http://www.drylok.com/products/drylok-extreme-masonry-waterproofer.php -on the interior to seal. It's been fine for 32 years. I made a roof from 1/2" foamboard held up by a light rebar frame and coated with -
https://www.quikrete.com/productlines/quikwallsurfacebondingcement.asp
It's very strong, I can stand my 190lbs on it.
Check around this site-
https://www.builditsolar.com/Experimental/PEXColDHW/TankConstruction.htm
 


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viracocha

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Posts: 7
Reply with quote  #5 
Thank you for all the information!

I completely agree that one must prevent the loss of heat as much as possible while still having adequate ventilation. I am going to aim at having as low of VOC products as possible to prevent indoor pollution and a tight building envelope. I haven't looked into prices or products but I want to have a solid concrete house with the exterior insulated with foamboard, hempcrete or whatever else I can figure out to be local and good to use. I need to look into insulating under the slab as you said because heat loss can be through the earth during winter too.

So for a 1000 square foot home that would be 120 square feet of window as a rule of thumb? And if 500 square feet downstairs that would be 60 square feet per floor?

Is it possible to have too much window area on the south side? Is there a point where heat loss at night through the windows will be too large or can window coverings make up for that? One thought I had was building a glass wall over the whole south side of the building about 2 feet or whatever away from the building. Then that can act as a greenhouse to bring heat in during the winter and in the summer it can be partially covered to block heat away from the building and allow for an air flow to cool that wall at the same time by venting the greenhouse to the outside.
sundug

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Reply with quote  #6 
As heated air rises, you could have more glass on the lower floor, this would also allow moresun to hit the slab-I'm assuming a framed second story floor. You can have too much glass, as sitting in the direct sun can be uncomfortably warm and provide too much glare. Check out my poured concrete and stone walls-  https://www.builditsolar.com/Projects/SolarHomes/Doug/SlipForm.htm I used foamboard on the exterior and my version of stucco over that.
and my thermal shades- https://www.builditsolar.com/Projects/Conservation/ThermalShades/ReflectexShade.htm
 Your idea of the glass wall 2' away from the building is basically a Trombe wall or sunspace sort of idea. But why not kick it out some more and get a useful space? See mine-  https://www.builditsolar.com/Projects/Sunspace/DougSolarGreenhouse.htm 
Sun directly hitting thermal mass is more efficient than hitting low mass or reflective surfaces, heating the air, then heating mass. This can lead to overheating. 

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sundug

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Reply with quote  #7 
Part 1 of my solar tour-   

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