Framing the roof was challenging for us and required a good bit of energy, especially while climbing ladders, holding the lumber into position, manipulating screws and drills to secure the boards into place (image courtesy: John Green).
The week past provided us a hint of autumn temperatures which will be upon us soon. Naturally, the cooler days got me thinking about daytime temperatures and when we might expect more optimal temperatures for gardeners to do what we enjoy most. I reviewed the extended (30 day) forecast, and it suggests temperature patterns will begin shifting lower in the next week (mid to lower 80’s) which this gardener finds attractive. Gardeners, if you are like me, there are numerous gardening chores ‘on hold’ waiting for autumn’s arrival. Cooler daytime temperatures mean we aren’t limited to working a few morning or evening hours (schedule permitting)-mainly on weekends! Continuing the discussion from last week (my journey building a greenhouse), proximity to utilities: water, electricity, and natural gas (or propane) are necessary for extending the growing season through winter months but will depend on how the greenhouse is expected to function, types of plants grown, and resources available.
Greenhouse Size
Determining the size of the greenhouse is the next step after identifying the optimal location. Consider what your gardening goals are and the plants intending to grow. For example: Is your focus to be on plant propagation, seed germination, or year-round cultivation? Knowing and understanding objectives will help determine the size greenhouse required to meet your needs. My recommendation is to build a greenhouse which satisfies minimal functional needs, then add additional square footage (25%) or build a greenhouse which can be easily expanded later.
SETX Climate
We live in an area with extreme temperatures and high winds which means the greenhouse design must account for dramatic swings in temperature between seasons. There are several ways to do this. Consider adding insulation, forced ventilation, reinforced framing, and additional support structures to withstand our weather while maintaining the optimal growing environment for plants. It is extremely difficult to cost-effectively maintain greenhouse temperatures below 90F for several months (end of May through October). Except for cacti and succulents, my preference is to relocate all other plants outside the greenhouse. Note: Aluminet shade cloth (50%) was used for 2 summers but heat continued to be an issue (above 95F) and the shade cloth blocked too much sunlight for the majority of plants during the winter months.
Interior Layout
Planning the interior space, pathways, and accessories- there are many factors to consider for efficient use of space. Factors such as space utilization, adequate airflow, plant access for maintenance or harvesting need careful consideration. This is the time to place pencil to paper and sketch the layout, keeping in mind work ‘flow’ and plant needs which are diverse for different plant varieties.
Essential Features Greenhouses require ventilation and airflow systems such as vents, louvers, fans, and exhaust fans are necessary for natural convection to occur but also needed for forced air flow, which better circulates the air. Fans need strong support, vents and temperature activated louvres require space to install them on the greenhouse wall or roof areas. Installing windows is an inexpensive way to dramatically increase cross-ventilation without added energy cost. Strategically place windows on opposite sides of the greenhouse for optimal air flow.
The greenhouse’s wooden framing is complete, and four (double hung) windows installed strategically to maximize ventilation. Two louvres (temperature activated using paraffin) and two exhaust fans (with temperature controllers) are framed located near the roof’s interior apex. Polycarbonate sheeting installation has begun on the entryway (image: John Green).
Installing an irrigation system isn’t necessary but having access to some type of watering system is needed to make the greenhouse functional. Consider if an irrigation system is right for you (it wasn’t for me) but having a deep sink with faucet having multiple hose connections was necessary to water plants and maintain adequate humidity levels. My preference is to manually water greenhouse plants, it keeps me in touch with everything growing.
Construction Materials
Building a greenhouse requires careful consideration of the materials and tools needed to ensure a sturdy and functional structure. Choosing the right materials is key but might depend on what you expect from the greenhouse.
Framing
Wood- most used (affordable), versatile, and appealing. Cedar, redwood, and pressure-treated lumber are each popular choices due to their durability and resistance to decay.
PVC- is lightweight, affordable, and easy to work with. PVC pipes and connectors are ideal for constructing small to medium-sized greenhouse frames.
Metal- does provide exceptional strength and durability. Aluminum and galvanized steel are common choices due to their resistance to rust and corrosion but cost significantly more than other material types.
Roof
Glass- provides exceptional light transmission, increased longevity, and is aesthetically appealing but does require expert installation at significant cost.
Polycarbonate- is lightweight, shatterproof, and offers good insulation properties. It is available in various thicknesses (single, double, and triple walled construction) and provides excellent light diffusion requiring replacement in 12 to 20 years.
Polyethylene Film– is economical, versatile, and easy to install. It provides good light transmission and is suitable for temporary or budget-friendly greenhouse structures but will require replacement every 3 to 5 years.
Foundation
Concrete– slabs provide a solid, long-lasting foundation and suitable for permanent greenhouse structures.
Treated wood– commonly used, pressure-treated lumber is a good choice for foundation frames and provides resistance from decay and insect damage.
Gravel– is often used as a secondary layer over the top of commercial grade landscape fabric or simply use the fabric placed on top of the soil (secured into place) for improved drainage and stability.
Insulation/ Sealing/ Hardware/ Fasteners
Weather stripping– is used to seal gaps around doors, windows, louvers, and vents to prevent heat loss and drafts.
Sealants– are utilized to seal joints and gaps to maintain airtightness and prevent moisture intrusion.
Screws, nails, bolts- each are required for joining differing material components of the greenhouse frame, roof, and structure.
Brackets (corner connectors)- these materials provide additional support and reinforce critical joints which are necessary.
Hinges (latches)- these materials are essential for doors and windows, to maintain and ensure functionality and security.
So long for now fellow gardeners! Let’s go out and grow ourselves a greener, more sustainable world, one plant at a time! Please continue sending gardening questions to: jongreene57@gmail.com.
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