So this is going to be a long post, fair warning!
I spent the better part of a weekend a few weeks ago applying landscape fabric and pea gravel to the gap areas between sections of our circumn-housal (I totally just made that word up) raised beds. Due to their shape and location they are notoriously hard to mow/trim, and as a result these areas annually became a nightmare tangle of odd and menacing volunteer plants (with a common itchy thread of poison ivy woven throughout). So this year, while everything was still "down and brown" from winter, I decided to get proactive about it.
The results look pretty darn good, and will hopefully cut down on the amount of poison ivy we find trying to grow up the side of the house this fall (those would be the dark places along the house wall).
We spent a goodly amount of time last weekend working on the barn wreckage and putting up some more insulation panels in the greenhouse. We are approaching the time of year when it's really only comfortable in the greenhouse in the morning before the sun really gets going, and in the evening after it's gone down. So we'll be working in there on mornings and rainy days, and picking up whatever didn't get done in the fall. Hopefully we can get it 100% shored up inside for this winter, where we can do a real test of what will and won't grow in there during the icy months.
This weekend found us working to install the "earth tubes" passive ventilation system on the greenhouse. I had the idea for this while sealing up some small air leaks around the interior of the greenhouse, near the floor. I noticed that the greenhouse was pulling cool air in through these small airspaces, presumably as a result of the heated air being pushed out the two gable vents near the top of the side walls.
So I began planning for a system that would take better advantage of this tendency, in a way that would passively provide some measure of cool air flowing through the greenhouse during periods of warmer weather. It is essentially a set of two tubes that are buried beneath the entire earth mass of the raised bed along the shady north-facing side, and enter the greenhouse through the floor.
As convection pushes the hot air out the gable vents at the ends of the greenhouse, it should pull air through the tubes, cooling it as it passes beneath all the shaded soil (we may add a small solar-powered inline fan to increase draw through the tubes if needed).
In the winter we could limit or stop the air flow from within the greenhouse, to prevent pulling too much cold air in (buried no deeper than it is, the soil will be much less likely to provide any appreciable warming action on the cold air in winter).
I had never heard of Earth Tubes before, but in researching my newfound idea I learned that a similar system is frequently put into use in Earthships and other more holistically-designed homes.
In those circumstances, the systems are buried deep enough to provide cooling in the summer AND warming in the winter, but for our purposes we've got warming pretty much covered from the passive solar angle.
I'm still not sure to what extent it will work or how much air it will pull, but I'm pretty sure that it will provide some benefit, and it was relatively inexpensive to install (needing just a big-ass roll of HDPE drainage tubing, pictured above) and requires no major modifications to the greenhouse itself.
So I started digging! First, one of two holes that burrows just under the north wall of the greenhouse.
Here's the tube sticking up inside. Once we finish putting up the second layer of insulation and the radiant heat barrier, we'll trim the pipe off closer to the floor and affix it to the wall somehow.
Some creative stone work to fill in some gaps and some retaining wall re-assembly, and we had ourselves an installed tube! I need to find or fabricate some form of grate cap for the end to keep my new air tube from becoming a high-traffic tunnel for critters (especially in the colder months when a warm building is oh-so enticing).
I am encouraged thus far, as the building is sucking air in through the hole around the tube at a noticeable rate. I'm hoping it will do the same through the tubes once I get that hole back-filled and sealed.
I also thought it would be a good time to dig the post-holes on either end of the west-facing door that will serve as the structural supports for our forthcoming trellis/pergola/awning thing (I didn't want to have to dig the dirt back out of the beds once I'd filled it in).
The trellis/pergola/awning thing will not only look neat and provide some shade over the west doorway, but will also provide a venue for climbing vining plants like grapes or wisteria. It will also give me something solid to latch the door to when it's open so it's not blowing shut all the cussing time.
Spent the rest of the day preparing to extend our annual raised bed area, chopping back quack grass from around (and unfortunately, within) some of our beds who have a side that touches lawn. Important lesson here when it comes to raised beds.... always make sure you have a border of grass-suppressant (lanscape fabric, gravel, something) all the way around your beds... otherwise the grass will just hop under the bed walls and go to town in the soil inside. If I had a dollar for every worming little white root I fished out of the dirt today... ugh.
This did mean that I got to make some good use of my new hand sickle today... old but practically brand new, I picked it up at the local flea market for $2.50. Sharp enough to dig deep into the wood of the raised bed when I miscalculated my swing. Vanquished a lot of grass out today with that thing....