Passive Solar Greenhouse in Texas

[Mark Hall]

greenhouse%20East%20wall%2072413.PDF

This is my greenhouse design for Texas. Breaking ground this week. I actually worked as a consultant for the state of Texas in 1980 and we built some of these "passive" houses in El Paso and Austin. 

I'm leaning away from SHCS, but will run a tube underground and to the outside of the structure to have the option of drawing air into the structure from under some huge oak trees where the temp is always 10 degrees cooler than in the sun.  Don't feel that storing "heat" in the soil would help in Texas. Goals are focused on cooling.

My strong skill is construction. I build high end homes and do rain water and solar systems. But I am new to aquaponics and hope to avoid mistakes in the tank designs and water flow strategies. I'm going to start with a Bell Syphon system in the media beds, which will drain into the rafts.  The deep water raft will drain by gravity to a sump. Goal is to avoid devices like timers and keep the system as simple as possible. Complex systems seem to break down too often. Don't know if I need a swirl filter but feel like I could add one if things get out of balance. 

In order to help cooling in our 100 degree Texas climate, my plan is to build the raft beds out of concrete and CMU (cinderblock) and waterproof it with Throseal FX100 which is labeled for potable water and also good for low pH.  My hope is that all the thermal mass will help temper the climate during the summer. Winter is no problem here. Also, I like the solidity of concrete over wood and durascrim.

Any thoughts on design improvements will be appreciated. I'll take photos as I go. 

[Matt Miskinnis]

Good luck on your new adventure.  Unless you have a lot of fish, I wouldn't worry about a swirl filter just yet, the growbed will be able to filter the fish waste and if you add worms (red wigglers) they can will also help with getting rid of the fish waste, and your plants will love the worms.  Also if you are determined to put in a filter I would recommend a radial filter over a swirl filter - much easier to implement.  Also a caution on using concrete, it will cause your PH to rise.

[Bart]

Looks very nice. One thing, it's hard to get auto siphons to kick in on a large media bed, you may need to split the bed up into three or four smaller beds.

[Mark Hall]

Thanks Matt. I'm thinking that sealing the concrete will prevent leaching. I guess I can install a liner in the concrete tank as a back up plan, but I'm pretty sure I want all the thermal mass from the tank structure.

Matt Miskinnis said:

Good luck on your new adventure.  Unless you have a lot of fish, I wouldn't worry about a swirl filter just yet, the growbed will be able to filter the fish waste and if you add worms (red wigglers) they can will also help with getting rid of the fish waste, and your plants will love the worms.  Also if you are determined to put in a filter I would recommend a radial filter over a swirl filter - much easier to implement.  Also a caution on using concrete, it will cause your PH to rise.

[Mark Hall]

Point taken Bart. Would a 3' wide x 12' bed work ok? For media I'm looking at 3/4" Granite. A local guy suggested screening it and putting the larger aggregate on the bottom and the  smaller stones on the top layer so that it's easier on the hands.

Bart said:

Looks very nice. One thing, it's hard to get auto siphons to kick in on a large media bed, you may need to split the bed up into three or four smaller beds.

[Ned Berndt]

Hi Mark,

Welcome to our world.  Given your construction experience you should do well and have good suggestions for the rest of us.

In looking at your design, I noticed several issues.  The overall square footage of your structure (32X48) is 1,536 sq ft, yet I only see grow beds (raft 200 and media 138) total 338.  You could get much more with a few simple changes.

Also, the max dimension for a duraskrim lined bed is 54" given the width of the product.

Your media beds are 3' wide yet construction materials are 4'...I would consider widening you media beds, the suggestion to split it into several beds is a good one also, because you will change the flow of water out of the media bed so that it doesn't flood your next stop.  Since your media beds are raised, possibly use a long, shallow sump under the media beds to free up more grow space.

We have the sump between our media and DWC beds for just this reason and pump out from the last DWC bed to the fish tank...See Gina at Green Acres design.

Your fish tank is square, would recommend round to control aerobic zones.  Not sure what the papaya tree represents or the beds around it, are they media beds?

I think or media beds as the biofilter for the system.  We also use red wigglers.  You can have a much higher ratio of DWC to media bed.

And last but not least, we grow plants that "fruit above the ground" , tomatos, cukes, zucchini, eggplant etc in our media beds and leafy greens and herbs in the DWC,  The media beds being South in your design may shade the DWC beds.

Just my initial thoughts

Best regards,

Ned

[Mark Hall]

Thanks Ned,

Many good points. 

The thought on the Papaya (or avocado or banana) is to have some trees inside the structure planted in soil. Would probably drip irrigate the soil around the trees the same as fruit trees planted in a garden.

The reason I am looking at a 3' media bed is because a friend did one at 5' against a wall and could not reach across to work the back part. Maybe 4' would be a better design? Good idea.

Agreed that space is not fully utilized. Will add more beds. Probably raft cause I'm going to test the local restaurant market for lettuce on a weekly basis.

Red wigglers a must. Is there a good internet source? 

[Bart]

It will depend on the pump capacity, the issue is the siphon needs enough incoming water flow to kick in, so a balance between pump size and siphon sensitivity. As for the media, make sure you test it - lookup viniger test oin this site there should be lots of examples. In my area a lot of aggregates are called granite most of them would not be suitable for aquaponic media because they will raise the ph.

Mark Hall said:

Point taken Bart. Would a 3' wide x 12' bed work ok? For media I'm looking at 3/4" Granite. A local guy suggested screening it and putting the larger aggregate on the bottom and the  smaller stones on the top layer so that it's easier on the hands.

Bart said:

Looks very nice. One thing, it's hard to get auto siphons to kick in on a large media bed, you may need to split the bed up into three or four smaller beds.