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Greenhouse/home Combo Orientation  RSS feed

 
Blaine Allen
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Location: Central Oklahoma
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Hey all,
Currently I am designing a straw bale (with possibly some earth bag walls for thermal mass - another question for another post) passive solar home that will include a South facing greenhouse. Or that was my plan. I was watching a video by Verge Permaculture and he mentioned building a greenhouse with more Easterly orientation to reduce overheating. He is located in Calgary in Canada - I'm in Oklahoma, obviously a much warmer climate! I haven't seen much else to back up the idea, so I was just curious - does anyone else have experience with an South-east facing greenhouse situation (only one side with glazing since it would be butted into the house)? He recommended up to 40 degrees East of due South.
Will extensive ventilation be enough with Southern orientation?
I have a little bit of experience with a hoophouse, but the application is quite a bit different (and it has roll up sides for good ventilation).
Would appreciate some feedback!
 
Hans Quistorff
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Yes I recommend the south east orientation.  Or plan on heavy summer shading of the west end of the greenhouse.
Intense late afternoon sun can make the house too warm to sleep. I have cultivated a row of plum trees on the west side of my house and it greatly reduces the summer overheating in the afternoon.
I think the reason for the 40 degrees is that the low early setting winter sun will still enter the greenhouse but the high late setting summer sun will be behind the greenhouse.
Usually the early morning sun is welcome to take the night chill off and that is maximised.
Also consider the prevailing wind direction during rainstorms so that your straw bale and plaster wall is not eroded by horizontal rain. That comes from the south west here and I wish I had a conifer hedge to break it up before it hits the house.
 
Blaine Allen
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Location: Central Oklahoma
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Thank you, Hans! I really appreciate the input! Definitely some great thoughts there.
And the prevailing storm winds are from the Southwest here as well. Having a greenhouse along the Southern length of the house should help with the erosion of the plaster... thanks for the extra tip!
 
Hans Quistorff
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the prevailing storm winds are from the Southwest here as well. Having a greenhouse along the Southern length of the house should help with the erosion of the plaster..

If you are going to turn the orientation to the southeast and that exposes a wall to the southwest it could be made into a trombe wall  perhaps by applying a layer of clear plastic roofing over a plastered earth bag wall.  That serves to protect the wall from the rain and at the same time slows the heat don so that it arrives when desireable. I have stacked black barrels on the west end of my greenhouse to serve this function.
 
Blaine Allen
Posts: 7
Location: Central Oklahoma
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Hans Quistorff wrote:
the prevailing storm winds are from the Southwest here as well. Having a greenhouse along the Southern length of the house should help with the erosion of the plaster..


Hm, good thought! Thanks!
I think I might just try to shade out the West end of the greenhouse. My reasoning being that then I can retain the due South on my wall to make it easier to shade the house's windows with the roof overhang during the summer... does that make sense, or would it be easier to change the orientation and have a different method for shading the windows (something as simple as shutters or collapsible shades over each window)? I've never designed a passive solar building before, so I can use any tips from those who are experienced as I can get.  :razz:
 
Blaine Allen
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Oops, I'm new to this forum, so not sure how to use the interface yet. I messed up the quotation there.
 
Hans Quistorff
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Yes unless you are familiar with HTML formatting it may not be obvious. To make what you write be outside the quote  you have to move the cursor outside the end quote .  You can break the quote up into parts by inserting {
...
}between each segment.

Yes trees on the west side and overhang over the glass wall are to excellent and compatible strategies to prevent summer overheating.  I am far enough north that having the glass tilted back from vertical is not of much benefit, the low angle of the winter sun comes in fine and the higher spring and fall sun is partially reflected in front to moderate the heat gain then.

Another consideration for your hot humid summer is cooling and drying the air by using french drain tubes in the ground under your house as long as the water table is low enough.  The tubes would draw air from outside the south side of the house which would be cooled by the earth which causes the humidity to condense and drain into the earth thus the air coming out inside the north wall will be cooler and dryer. Jus as wit the earthships this is powered by ventilating the greenhouse. You can basicly achieve all the earthship advantages without all the earthworks by using the straw bale outer walls and earth bag and timber framing for the interior walls

Do you need to do water collection from the roof or is water abundant on your property?
 
Blaine Allen
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Location: Central Oklahoma
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Hans Quistorff wrote:Yes unless you are familiar with HTML formatting it may not be obvious. To make what you write be outside the quote  you have to move the cursor outside the end quote
.  You can break the quote up into parts by inserting {
...
}between each segment.

Yes trees on the west side and overhang over the glass wall are to excellent and compatible strategies to prevent summer overheating.  I am far enough north that having the glass tilted back from vertical is not of much benefit, the low angle of the winter sun comes in fine and the higher spring and fall sun is partially reflected in front to moderate the heat gain then.

Another consideration for your hot humid summer is cooling and drying the air by using french drain tubes in the ground under your house as long as the water table is low enough.  The tubes would draw air from outside the south side of the house which would be cooled by the earth which causes the humidity to condense and drain into the earth thus the air coming out inside the north wall will be cooler and dryer. Jus as wit the earthships this is powered by ventilating the greenhouse. You can basicly achieve all the earthship advantages without all the earthworks by using the straw bale outer walls and earth bag and timber framing for the interior walls

Do you need to do water collection from the roof or is water abundant on your property?
I've done a little bit of HTML in highschool, but haven't done it lately! :P Thanks!

I'll probably plan for that, then. Sounds like it'll work well.

Hm, that is interesting. I hadn't thought of that. I might have to incorporate it into my design!
Speaking of earth bags and timber framing... is the earth bag building stable in straight runs if it's incorporated into a timber frame structure? I know many people say that the earth bag needs to be curved or buttressed if it's in a straight line, but I wasn't sure if it would be strong enough with the timber frame support. Does that make sense?

Water is far from abundant here (except for the 5" rain we just got last weekend!), but we have 9 swales and 8 ponds/catchment systems on the property, so it's improving. However, I plan on collecting my roof water. I have a small wash out just South of my homesite that I'm planning on turning into a terrace system for arrowroot, water chestnut, and other aquatic species. This will be kept full with either/or grey water and roof run-off. I might have a couple of terraces that are just for filtering the grey water until it runs into the pond that will be at the end of the terracing.

Thanks again so much for answering my questions and giving me some new ideas! It is very appreciated!
 
Blaine Allen
Posts: 7
Location: Central Oklahoma
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Hm. I left all of my message after the end quote code, but I obviously didn't do it right. XD
 
Hans Quistorff
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Speaking of earth bags and timber framing... is the earth bag building stable in straight runs if it's incorporated into a timber frame structure? I know many people say that the earth bag needs to be curved or buttressed if it's in a straight line, but I wasn't sure if it would be strong enough with the timber frame support. Does that make sense? 

I am not qualified to give you design criteria but I understand the physics enough to explain why. Earth bag and straw bale have compression strength, you can press down on them but they don't have tension strength, you should not push sideways on them.  If they are not perfectly vertical then their own weight that is off vertical will try to pull them apart. Rafters pressing sideways can tip them over and earth piled against them can cause them to burst inward.
Timber has both compressive and tensile strength therefore incorporated into construction to resist these forces. The longer or higher any wall is the more leverage is created to tear it apart.
Keep these principles in mind so that you don't submit a design that is impossible to build safely.
 
Blaine Allen
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Location: Central Oklahoma
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Hans Quistorff wrote:
I am not qualified to give you design criteria but I understand the physics enough to explain why. Earth bag and straw bale have compression strength, you can press down on them but they don't have tension strength, you should not push sideways on them.  If they are not perfectly vertical then their own weight that is off vertical will try to pull them apart. Rafters pressing sideways can tip them over and earth piled against them can cause them to burst inward.
Timber has both compressive and tensile strength therefore incorporated into construction to resist these forces. The longer or higher any wall is the more leverage is created to tear it apart.
Keep these principles in mind so that you don't submit a design that is impossible to build safely.


I do construction and remodel for a living, so I understand the basic physics of it. I will keep that in mind! Thank you!
 
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