ventilation

[pecker88]

Starting in late Nov. I used wiggle wire / c channel to secure the roll up sides to the bottom boards on either side of the high tunnel. I also insulated around the inside perimeter using 1.5" rigid Styrofoam, spray foam, ect... It's pretty air tight and I've noticed the humidity lately; most of the time it's around 100%

I also added power and a 55K BTU non-vented propane heater.

Nothing is planted yet, but I'm wanting to start my first tomatoes around 15 March. Daily temps with everything closed are commonly 80-110 degrees on a sunny 20 deg. F day.

My question is ventilation. I'd like to invest in either:
1. automatic roll up sides (I wrote an app that I could control them with my phone)
2. Ventilation fan with motor powered intake vents

Which would be the better bet? It seems like either option would fight/contend with the heater. Meaning, when the heater is on, the ventilation would draw the heat out?
Heater is mounted just above the door in below pic.

thanks.

[Ricky Shaw]

Finely detailed art right there.

[Cole_Robbie]

1. automatic roll up sides (I wrote an app that I could control them with my phone)
2. Ventilation fan with motor powered intake vents

#1 gets my vote. It is a lot easier to let the wind do your venting for you.

And I agree with Ricky, it's beautiful. My only suggestion would be more end wall openings. On a lot of days, you can just open those vents and not have to use the roll-up sides. You definitely want at least peak vents on the ends, so that the very hottest air does not get trapped under your plastic, which will weaken the life of it, as well as make your roll-up sides less effective.

[FourOaks]

I vote for both, if possible. Or if possible, when the season really warms up take the door and panels off. Depending how warm your location gets, you want as much ventilation as possible.

Also, you might set a temperature differential for your heat and fan. Something like 10-15 degrees. A small fan or 2, to just circulate the heat will help as well.

[whoose]

I would spend the money on whole house attic fans, they come with thermostat. Mount oppsite the door put in a screen door and forget moving the side up and down. You will need to fence the side to keep out insects, mammals, reptiles and what ever else wants to get into you GH.

[pecker88]

thanks guys. I'm going to start with auto-roll up sides. I just ordered the motor driver and DC power supply. I plan on using the gear motors intended for semi's and dump truck tarps; should have plenty of torque.

Once I get it wired up I'll post some pics. Most of the easy part (software/app) is already done; I struggle with hardware.

[AKmark]

I use vents, and this year it will be bug screened vents, insects suck in GH's. I can turn my air over in just a couple of minutes, and usually can keep the temps in the 80's too. Everything is automated, takes a bit of wiring knowledge, but is pretty simple too.

I do know others use roll up sides, and it may be necessary in hotter climates.

[greenthumbomaha]

Pecker, that is a super neat structure. I have a few temperature questions since you're local to me, hope you don't mind my curiosity living thru your experience. I can't believe how warm your high tunnel is when its this cold. Did you add the heater to start growing inground tomatoes or transplants on March 15? That sealing up the cracks should take care of the nasty herbicide drift we both had last year.

Do you already have a propane tank for your home, or do you rent one for the tunnel? Without the heater on, what would be the min/max temperature on a 20 degree cloudy and sunny day. Are you keeping the heater 24/7 on to maintain the 80 degree temp? Was that 110 degree reading when our winter suddenly turned into sunny 50 degree days last month?

What are the soil temps like? Are you going to put plastic down to warm up the soil before planting? Any cold weather crops like broccoli in your plan?

Hope you have a great growing season!

- Lisa

[PureHarvest]

Correct me if I'm wrong mark, but I think you want to exchange all the air one time per hour, even at night. This would be for early in your season when the sides are down and you are running your heater. This is why you need the end vents at a minimum. It would be overkill doing the auto sides for this and would be too much wear. They would be good for summer with the gable vents like cole mentioned.
I agree with the insect netting. I will be outfitting both of my tunnels with it this year. Look specifically for greenhouse insect mesh that excludes thrips to get the micron size small enough to keep them out along with whiteflies.

[AKmark]

Originally Posted by PureHarvest

Correct me if I'm wrong mark, but I think you want to exchange all the air one time per hour, even at night. This would be for early in your season when the sides are down and you are running your heater. This is why you need the end vents at a minimum. It would be overkill doing the auto sides for this and would be too much wear. They would be good for summer with the gable vents like cole mentioned.
I agree with the insect netting. I will be outfitting both of my tunnels with it this year. Look specifically for greenhouse insect mesh that excludes thrips to get the micron size small enough to keep them out along with whiteflies.

Thanks for the thoughtful points.

In AK temps are below freezing much of the time up through May. Venting the cold air in, as you can probably imagine, is not good when its freezing outside, it can be -10 in April. Rare but it happens. What I will do is exchange it very briefly during the day before things warm up and everything goes auto. When its summer up here we have really long days, I will vent until about 10:00-11:00PM, but thought I needed to vent a couple of times at night too. I also now have tiny vent fans that always run, they keep some fresh air coming in, 5 inch.
I have heard that some up in Fairbanks actually have lung rooms to temper the cold vented air, I have not seen these though.

Our nights are rarely over 60, usually 55 average, which is cool air, I want 63-64 night time temps. What I did was compromise, and just have an over ride that auto vents regardless of temp that the shutter is set to go off at. I am starting at 4.00am, 5, and 6 for a minute, this leaves about 5 hours no venting besides the tiny vent and the poof fan. Many mornings my humidity was higher than I like to see, hopefully it is better this year, that's my guide.

I have been chasing the cure rather than doing 100 percent to stop the cause, when it comes to insects. We do really well with parasitic Wasps for aphids, but I am sick of buying bugs to kill bugs. Just another expense. I have cut all trees back as far as possible, aphids live in birch trees, and it's just not enough, so here comes the screens.
Aphids are so bad up here roll up sides are just out of the question for me. I have found though, if my pepper plants grown in the greenhouse gets aphids, I throw them outside and other insects wipe out the aphids. I can't quite figure that one out?

[pecker88]

Originally Posted by greenthumbomaha

Pecker, that is a super neat structure. I have a few temperature questions since you're local to me, hope you don't mind my curiosity living thru your experience. I can't believe how warm your high tunnel is when its this cold. Did you add the heater to start growing inground tomatoes or transplants on March 15? That sealing up the cracks should take care of the nasty herbicide drift we both had last year.

Do you already have a propane tank for your home, or do you rent one for the tunnel? Without the heater on, what would be the min/max temperature on a 20 degree cloudy and sunny day. Are you keeping the heater 24/7 on to maintain the 80 degree temp? Was that 110 degree reading when our winter suddenly turned into sunny 50 degree days last month?

What are the soil temps like? Are you going to put plastic down to warm up the soil before planting? Any cold weather crops like broccoli in your plan?

Hope you have a great growing season!

- Lisa

No prob, I'll do my best to answer q's.

I added the heater last aug. in preparation to extend the season. in mid October I planted potatoes (never grew, soil too cold) and lettuce. I set the t-stat to 40 and it would only run at night.

I'm thinking my transplants (basement) will grow better in containers on March 15. Based on last fall's potato experiment the ground will be too cold.

We live outside Lincoln on 1 acre so we already had a 1K gallon propane tank for our house. No heater, 20 deg cloudy day = 25-30 in greenhouse. No heater, 20 deg sunny day = 60-80 in greenhouse. I actually have a temp logger records a temp every 10 minutes to a database. I just crunched the data for Jan a few days ago, it's amazing how warm it is, no heater either. I'll post the graph later today.

Yes, the 110 deg reading was the 50 deg day last week.

I would bet the soil is pretty cold, I've never measured though. No, Im not going to put down plastic. I will try a few early toms in containers and in the ground and see what I get.

[Cole_Robbie]

You might watch the night temps to see if it ever dips below the outside temperature. That happens in some weather conditions, usually clear nights, due to radiative cooling.

[whoose]

Peck

What is your source for your temp logger? I am very interested in using one for my greenhouse.

[pecker88]

Originally Posted by whoose

Peck

What is your source for your temp logger? I am very interested in using one for my greenhouse.

I made it using an Arduino Uno microcontroller. Then when I trenched electric and gas lines I also ran a Cat6 out there. So now instead of relying on wifi and solar panels, I have hardwired connections.

Best part is that the Arduino has plenty of digital pins remaining for my 4 limit switches and motor controls I'll use for the sides.

Looks like the project will cost around $400 for both sides, just ordered all the electrical components today, can't wait to start soldering, wiring and writing code!

[pecker88]

Here's the greenhouse temp. graph from January. I crunched the data a few days ago so I'm missing the 25th and 26th.

I have 144 temp. readings for each day (10 minute intervals). I then extract the high and low out of the 144 readings and plot.

Wish I had a sensor on the outside of the GH so I could add a 3rd set of data on the graph to compare inside vs. outside...maybe after the auto. sides project.





Just for fun, here are the 10-minute averages for January. I took all readings from the same time in Jan and produced an average then plotted. Plotting 12 lines on this graph would be cool to track the sunrise/set over the course of the year...



And yes, my wife says I officially lost it; but she just doesn't understand
Its fun when education, hobbies and work all collide.