Monitoring devices: top-outside, middle-inside, bottom-wall
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Location Arcata, California

This is the Operation and Maintenance (O&M) manual for CCAT greenhouse and CCAT Beach Grass Clay Slip Wall. Please refer to it and keep it up to date with any O&M changes.

Operation[edit | edit source]

The beach grass wall has little in the way of operation. It passively absorbs solar radiation during the day and emits heat during the night, helping to modulate the temperature in the greenhouse. The rest of the greenhouse requires monitoring and active support. The following guidelines should be followed to operate it successfully:

  • Monitor humidity and temperature.
    • Desirable temperature and humidity vary depending on the desired plants to grow. The temperature should be kept high enough to be above the dew point, which prevents water from condensing on the plants and thereby preventing fungal growth.[1]
  • Open vents to increase airflow.
    • Roof vents should open automatically with increased temperature in the greenhouse
    • During the day, when the roof vents are open, the ground vents should be open to allow air to flow through the greenhouse.
    • Side vents can also be opened to increase air flow and to provide humidity control when it is not hot enough to operate the roof vents.

Maintenance[edit | edit source]

The greenhouse has two main components: the Sturdi-Built prefabricated greenhouse structure and the beach grass clay slip wall. The greenhouse structure has a variety of small issues that can be checked on a regular basis to ensure the proper operation of the greenhouse. The beach grass clay slip wall is an experimental wall that requires monitoring for its continued success. As a wall built of earthen components, the moisture content of the wall is important. Straw is generally thought to degrade at 20% moisture content and 14% moisture content is considered safe.[2] It is therefore important to check the humidity level inside the wall on a regular basis to predict whether the wall is suffering internal degradation. The wall humidity sensor is indicated on the bottom monitor.

Schedule[edit | edit source]

  • Monitor humidity and temperature
  • Wash the greenhouse glass inside and out to allow maximum sunlight into the greenhouse.
  • Check solar vent openers are operating when temperatures are warm.
  • Check wooden frame for damage, fungus, or decay
  • Check glass panes for cracking
  • Check beach grass wall for plaster cracking or structural damage.
  • Sand and apply a new coat of linseed oil to the frame.
  • Replace any window nails that appear to be corroded by rust
  • Examine the entire structure for decay, damage, broken or rusting parts, mold, broken plaster, color fading on beach grass wall and other problems that need to be fixed.

Instructions[edit | edit source]

This section includes details on some of the procedures required to maintain the CCAT greenhouse and beach grass clay slip wall.

Dirty glass is not effective at letting light in.

Spraying water across the glass, inside and out, using a hose can get most of the dirt off.


Water alone can leave streaky and uncleaned glass. If water is insufficient, apply a natural glass cleaner and remove with newspaper. An example cleaner contains: 1/4c vinegar, 1/4c rubbing alcohol, 1 Tbs cornstarch, 2c water.[3]

Baylis MK7 Solar Opener

Examine the silver lever arm that opens the roof vent.

Indoor temperature is on the middle monitor, circled here in yellow

Determine the temperature in the greenhouse. If the temperature is above 65 F, the vent can be opened.


The opener lever arms have an adjustable pin at the bend in the arm. It can be rotated to change the temperature at which the arms operate. If the arm is not extending, turn the adjustment pin clockwise and wait to see if opens the vent. If not, turn the pin counterclockwise.

Lime slaking.jpeg

Slaking lime is similar to the process of slaking clay as described above. Lime needs to be slaked for a substantial amount of time in order to ensure quality. While this amount of time depends on the location, temperature and other factors, start slaking the lime about one month before intended use. There should be about one inch of water left on top of the slaked lime when it is ready.


Use a paint mixer to mix the slaked lime until it has about the consistency of yogurt.

Plaster in a bucket.JPG

Combine the plaster ingredients. Previously used 1 part slaked lime, 3 parts river sand, and horse manure "to taste", which was about 4 handfuls in a 5 gallon bucket. Combine these slowly while blending with a paint mixer. The final plaster should hold its shape and have noticeable fibers when broken apart.


Plaster can be applied using hands and cement applicators/scrapers. Pressing the plaster into the crack and then smoothing with a scraper works well.


Paint the repair.

Troubleshooting[edit | edit source]

Problem Suggestion
Inside humidity it too low. Spray the crushed rock floor with water to allow the water to be added to the air in the greenhouse.
Inside humidity is too high. Open manual vents to allow airflow. If humidity does not decrease, open doors as well.
Monitoring device has no display Change batteries in the display unit.
Baylis MK7 roof vent lever arm no longer opens when warm after adjusting the pin in both directions It is possible that the piston that opens the vent has lost too much wax and cannot operate anymore. Replacements can be ordered by contacting:
Sturdi-built Greenhouses/Superior AutoVents
11304 SW Boones Ferry Rd.
Portland, OR 97219
1-800-334-4115 or 503-245-5650 Monday – Friday 8am to 5pm pacific time
By email: Fill out Order form PDF and email to
By FAX 503-293-9266 Fill out the order form PDF and fax to us
More information on pricing for the vent openers and vent openers in general.

Suggestions for future changes[edit | edit source]

Current glazing support system
  • Replace support nails with a more permanent glazing support system.
  • Set up data logging of inside, outside and wall humidity and temperature.

References[edit | edit source]

  2. Steve Goodhew, Richard Griffiths, Tom Woolley, An investigation of the moisture content in the walls of a straw-bale building, Building and Environment, Volume 39, Issue 12, December 2004, Pages 1443-1451, ISSN 0360-1323,

FA info icon.svg Angle down icon.svg Page data
Part of Engr535 Development Technology
Keywords ccat, ccat active project, greenhouses
Authors Matthew Collins
License CC-BY-SA-3.0
Organizations Cal Poly Humboldt
Derivative of CCAT greenhouse
Language English (en)
Related subpages, pages link here
Impact 248 page views
Created April 24, 2014 by Matthew Collins
Modified January 29, 2024 by Felipe Schenone
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