Floor design is passive solar

[EcoHeliGuy]

So I have been trying to decide what I would like to do for a floor in my passive solar home.

I was intrigued by this article
http://www.motherearthnews.com/Green-Homes/1982-09-01/The-Floor-Storage-Thermal-Loop-Home.aspx

And mostly by this photo
http://www.motherearthnews.com/uploadedImages/articles/issues/1982-09-01/77-144-i2_01.jpg

I Plan to use this design for a floor in my house, but I have been trying to decide the best way around it over the past couple months.

I have come up with two options.

Option A:
Before pouring slab, I would run PVC pipe from north wall of the house to south wall, In the north rooms there would be a regular floor vent that you would use in an Hvac system. under this would be two PVC pipes running together side by side to the south rooms, with a vent directly below the windows (aka PVC ducts). At the ceiling between the south room and north room would be a passthrough vent in the top of the wall. The PVC ducts in the floor would be spaced about 3ft apart from east to west in the house.   Down the center of the house I would tie all pipes into a common PVC pipe that ran east to west. this pipe would be tied into my Earth tube. (follow my link in signature to get an idea of the house layout)

So in this set up the air in the south rooms would heat up from the sun or fire place. Then rise to the ceiling. This would cause a low pressure and draw cool dense air from the north rooms through the floor. Which in turn pulls the warm air from the south room at the ceiling through the vents in the top of the wall. This cycles the air through the house warming the house evenly. At night the large windows in the south room will cool the air, causing it to fall, reversing this flow. With the PVC pipe in the middle tying all the ducts together, to help the master bedroom maintain a similar temperature to the rest of the house.  When air leaves the house (ie bathroom fan, woodstove, dryer ect) the earth tube that is connected to this center PVC pipe will supply fresh air to the system and mix with the air in the ducts before entering the room.

Option B

in this option I would pure the slap, but then raise the floor on 2X4's, and just allow the air to drop down through floor vents and travel between the subfloor and the slab. still having with the same paths of air travel, just above the slab and not below.

I would love in put from others as to which method  you would choose   

(ListerP managed to post while i was editing, before it made any sense)

[ListerD]

OK.

 

[EcoHeliGuy]

Ha ha ListerP you found my mistake  

Hope it makes more sense now

[bayview]

   I think that earth tubes, PVC pipes, raised floors could be potential problems.  Seems like good places for dust/dirt to collect.  If it is humid, I would be concerned about mold . . .

   Proper condensation drainage and installation are critical . . . Seems larger diameter pipes work better for heat transfer. 

   Here is a link that may be of interest . . . ( Sizing pipes, drainage, proper installation grade )

http://en.wikipedia.org/wiki/Earth_cooling_tubes#Safety

   You may want to consider a thermal mass system (trombe wall).  Instead of buried PVC or a raised floor, you could put vents in the bedroom wall near the floor and the ceiling. 

   Trombe Wall Link . . . http://en.wikipedia.org/wiki/Trombe_wall

   I would install the wall on the south side. . . Limiting windows and doors to the east and west.

/

[Virginia Gent]

I have a question that I think I will post here instead of creating a new topic. So, I'm sorry if I seem to derail your thread, mcbane666, but it is not my intention. My question is this: in these Passive Solar Homes I have been reading so much about lately, do they work the same in the summer time to help keep the house cool, or do you have to rely on A/C units and such to do that bit of work?

I would really love to have a house that stayed a nice temperature all-year round using nothing electric; so far the best I can find is this, which was posted in the "Earth Tubes" thread http://thenaturalhome.com/passivesolar.html

Is this the same thing, in general, that you are building? And if so, does the design work to cool the house in the summer as it does to heat the house in the winter?

[EcoHeliGuy]

Virginia Gent: No problem, Solar passive design will not cool your house, unless you design it to, but i'll cover that in a moment. If you put a high insulation value in the roof and walls, you will not gain heat through these systems, and the roof is where a house in the summer receives most of its heat. Second with a passive solar house you place over hang above the windows that block the direct sun light when its high in the sky during summer. this is also a huge source of heat. If the place your living in right now has sun hitting the floor in a room during the day, I'm sure you have noticed that room is warmer then the rest. Just like sitting under a shaded tree is cool, the over hangs keep your rooms cool. Remember in your house the room is closed so the heat has no where to escape when the floor heats up.

This brings me to designing a solar passive home to cool, And there are two things you can do, both do not need to be done together. If off you can use the earths mass, If you have ever gone into an unfinished basement have you noticed how cool the air is? the earth is keeping this room cooler. Second open high windows on south, east or west sides of the house. and open low windows on the north or shaded sides of the house. as your house heats up in the day warm air rises, it will be drawn out the higher windows, and draw fresh cool air in from the lower windows. This can be done in any house, but helps if the house is designed to move the air quickly from low to high. for the best effect. use shaded south windows as close to the roof as possible, and the lowest north windows that open onto a pool, or trees. not not use a north window that has a mass that warms in direct sunlight like a blacktop parking lot.


bayviewps: I'm leaning toward the PVC ducts as they are easyer to clean, the whole system would also be drained through my earth tube set up.
I would install that Wall system only if I was trying to add a heating system to a already built house, as my method is to naturally move already heated air.

Also I was thinking how nice it would be to be able to place filters on the vents, but with no mechanical fan to move the air, I figured there would be way to much restriction for the system to work. and then my girlfriend had mentioned just placing cheese cloth under the floor vents. It wouldn't trap the micron stuff, but it would be better then nothing, for hair and dust balls. 

[John Raabe]

One of the most important determinates of success (or not) with Passive Solar is the climate of the site and the house exposure and microclimate.

I wrote the Sunkit several years ago to allow folks to easily determine the solar potential of their site and the types of heating and cooling strategies that will work in their climate. If you are in a cold winter Northern climate you cannot do the same techniques that have proven successful in the desert SW. Build earth tubes in the wrong soil or climate and they will disappoint as well. Latitude and winter sunlight patterns make a huge difference, not to mention the trees and buildings to the south of your house.

The Sunkit booklet is now a free bonus on any plans order over $100.

[Don_P]

I designed our house with some passive solar features, one of which was low north windows and high south clerestory windows that were going to be horizontal sliders. They are at the top of a 4/12 pitched south facing room with south glass. there is a second floor area lit by the clerestory glass and I had hoped to exhaust through those operable windows on hot days. As soon as I had the roof framed the folly of that plan hit me. Hot air rises on top of the roof and came pouring IN the windows, they were not interior hot air exhausts they were inlets for superheated air. I switched them to fixed panes.

One more thing to think about and solve if needed. During humid periods here a basement can be below dew point. Any hot humid air that meets the cool concrete sweats on contact and often leads to mold.

[EcoHeliGuy]

Thanks for that don_p, that does make sense. especially as I have a patio roof right below my south facing windows. Maybe i'll only place one or two non-fixed windows up there for releasing hot air from the house after the sun goes down.

Don_p or john Raabe, do either of you have any ideas for my floor system?

[John Raabe]

McBane:

To give you any specific advice about passive solar options I need to know the following at a minimum:
• location or latitude
• climate - what is it like in the winter (how cold, how cloudy)? If cooling is an issue, how hot in summer?
• what is the soil like and how much water does it hold?
• what is the yearly average soil temperature or what is the temp of the well water?
• when you face true South (not compass S.) what is the angle above the horizon of the highest thing that will block your sun.