DIY Geothermal Greenhouse Pt 10: POLY FILM INFLATION

This #119 In this video we look at the poly film inflation on our DIY geothermal greenhouse and discuss some initial data on the earth battery system.
*We readily admit we are not experts at this (we are not engineers, greenhouse experts, or thermodynamic scientists), but a family doing our best to do it all ourselves and install based on all that we have read or watched on KZbin (Don't believe everything you see on the internet) to date and in line with our limited budget. Based on comments on previous videos, we already know some things should be done differently. Hopefully, it still works well enough, even if not optimally. We plan to share the results regardless.
Background on the project: Our farm homestead came with metal pipes in the ground from a former 16' x 50' hoop house. It also had water lines run from the farm well (which also needed to be restored) and a 60 amp electric service. In the first video we installed the 1.25" EMT conduit that serves as the structure.
Each rib or section of the greenhouse consists of three 10' pipes, no cutting. They are joined by stock EMT connectors. The two outer angles are 117.3. The ridge angle is 125.4. Sides are 6' tall. Just over 10' to the ridge. 16' wide.
We installed an geothermal earth battery under the greenhouse using 4' perforated drain pipe and use high efficiency fans to pull hot air from the top down into the earth, storing that heat, and returning cool air during the day. At night, we reverse the process.
Ultimately, this will be a double wall plastic film greenhouse.
+AMDG
Music
Jason Shaw: "Landra's Dream" goo.gl/pi68XB
#greenhouse
#passivesolargreenhouse
#emtgreenhouse
#earthbattery

[@acornaction1938]

My answer to your question, you are looking for F^3PM, so velocity (FPM) * the area of the pipe (Ft^2) gives feet cube per min (F^3PM) INTAKE: Convert MPH to FPM, 17 mph = 1496fpm Find area of pipe, Pi*R^2, 3.14159*3^2 = 28.3in^2 Convert square inches to square feet, 28.3in^2/144 (in^2/ft^2) = .2ft^2 multiply out to find CFM, 1496fpm * .2ft^2 = 299 CFM DISCHARGE: 12 mph = 1056fpm pipe = .2ft^2 1056fpm* .2ft^2 = 211 CFM Total air changes: Two fans in CFM converted to Combined cubic feet per hour, 211*2*60 = 25320 CFH Combined volume of fans divided by volume of green house gives total Air Changes per Hour, 25320/6144 = 4.12ACH I rounded numbers to make the math easier, For What It's Worth

[@StIsidoresFarm]

WOW! Seriously, thank you for taking the time to do these calculations and share them! Unfortunately, the final number is much lower than we had hoped. Not terrible, but definitely not what we were aiming for. We'll use this in a Q & A about the greenhouse in the near future!

[@acornaction1938]

You are welcome, The fan housings look like they are designed for an inline application. Opening up the intake side may give a volume increase at the expense of slowing down the fan, the higher volume would create more drag. Again just my opinion.

[@krimmer66]

@@acornaction1938 just curious but would a fan at the return/exhaust end, to create a pull, help at all?

[@acornaction1938]

@@krimmer66 In my experience fans are much better at pushing air than pulling. Also I would be concerned with the fans fighting each other, because of the length of the series. Lowering the intake velocity by increasing the intake diameter may allow for a higher pressure on the discharge side. I am not an aeronautical engineer by any measure. FWIW.

[@krimmer66]

@@acornaction1938 I did some digging around and it seems cannabis growers have been the most active exploring this LOL. Nothing concrete but a few people did say it was completely safe to put these fans inline, that said it will not double the air moved however an increase could be possible.. none of them were aeronautical engineers either as far as I know haha.

[@keng528]

I once was part of a research project using a third layer of poly. In short, it worked fantastic. Reduction in lighting was way less than expected. This allowed the owner to relocate to a colder climate and still pay the same but usually less than before. It really was worth the extra expenses.

[@sevensurvival]

Thanks for all of Your work, and research. Excellent project. Respect, and blessings.

[@SimpleTek]

Great video thank you

[@gregkahle9046]

Learning a ton watching your videos, cool stuff! It's awesome seeing your seeds popping; sure your boy is happy and proud. Really like your comment section and subs, lots of good ideas and info. It's going to be so nice when you get everything up and running and all dialed in with systems running like clockwork. Won't be long now, keep up the good work thanks for sharing.

[@StIsidoresFarm]

Thanks! Positive comments like yours are really encouraging, so please know how grateful we are. Yes, it's getting exciting to see it coming together now!

[@toddhower8215]

thanks for sharing your experiences! Great video!

[@teleguy8722]

Awesome video. Late or not, really appreciate the consistency and quality of this series. Can’t wait to see how this performs in our NC winter and hopefully build my own in the next few years.

[@StIsidoresFarm]

Thank you!

[@yankey4]

Love it brother. The place is looking so good. One thing I would say is this. Growing up I worked as a helper foing HVAC work. Putting in duck work. I was told the more air moving over a coil would not mean colder air. It would like your saying just be more air moving faster. So I would think with you trying to store that heat it would be best not to have the air moving to fast. Thanks so much for letting us be a small part in this. God Bless.

[@StIsidoresFarm]

That makes a lot of sense to me. Still, we're getting a lot of conflicting advice about this system. Hard to sift through it all, honestly. But honestly, my thinking has always been what you said. Blessings to you as well - you guys remain in my prayers!

[@mattoja8857]

Very cool project. I binge watched the whole series! Great job with the videos - you got the gift of the gab man.

[@StIsidoresFarm]

Funny, I'm actually an introvert.

[@jenkinssthomson8879]

Good job. Thx for sharing.

[@sammunjanat]

Hello Sir, Absolutely you are fantastic... I'm your Canadian online student ... for my upcoming project, Thank you so much, and great appreciation for sharing the bright ideas through creativity....

[@williamrbuchanan4153]

Very good , well explained and thoughts for better from what you have divulged, for free, Thank You very much, is I’m just doing a small garden type tunnel. But your detail has lots of aid to me, a first timer too. In Uk winters it could be very handy knowledge.

[@theprepperfrog167]

Dang sir, i love this project! Thank you !

[@StIsidoresFarm]

Thanks for watching and taking the time to comment!

[@Izaugsme.TipuTapu]

Hello from Latvia! Keep up the good work guys! Of course, you know what we all are waiting for! The wintertime! I hope the system works! Its real benefit that you guys are spending money, going through the ups and downs and we can just sit back and learn! Thank you very much!

[@code3racing]

I've enjoyed watching the progress on this and congratulations to Isaac for a great start to his project. As a small beginning homesteader in Arizona, my thoughts as you were showing the french trench and plans for the drain made me automatically think about harvesting the rainwater. I know it isn't necessary in North Carolina like it is here, but have you thought about harvesting the rain water instead? 1. It saves on the city water bill and is more organic. 2. It's better for plants because it is more organic and, if you're on a well, better because it hasn't picked up excess salts and other minerals as it goes through the soil into the aquifer you're tapped into. Just some things I have been learning while reading Brad Lancaster. :-) Again, really enjoying the videos. I'm trying to figure out what I'm going to do for my greenhouse I'm designing.

[@oilspeculatorhater]

Great video, thank you. So much great stuff in it that we need to know.

[@StIsidoresFarm]

You're welcome!

[@WCharles9272]

In some locations newly installed fire suppression systems like in a computer center usually requires a test of the leakage in the area to find out how long the fire suppression gas will remain in the room. This is done by measuring over say 30 minutes the air leakage. Your local fire department or building inspector could tell you if they have the apparatus and maybe bring it out and make a test of the air leakage in your system. In Dayton, Ohio the test is known as Fan-Door Test - called that I suppose because they put their fan in a doorway to pressurize the room. This might work and be of no or low cost

[@litebkt]

I love the detail an tests!

[@StIsidoresFarm]

Thanks!

[@justsomeguy934]

If I had done this, I would want temperature sensors in the underground pipes at specific intervals. This would tell you at what length of buried pipe the building's heat is dissipated. It's a nerdy thing to want to do but it would help planning other ground batteries like this one. What a fabulous job you've done!

[@StIsidoresFarm]

Thanks!

[@audioalt]

Its Working thanks!

[@LifeinFarmland]

Check out that shirt! (stihl) Really a great series you have been putting together!

[@oby-1607]

We want to put in an earth battery before our next high tunnel and it seems to be beneficial according to your video. Thanks, as I think you have tipped the scale towards doing this.

[@StIsidoresFarm]

We hope to continue to follow-up and share more data - hopefully, it will help others in deciding whether to install a system like this. What we can say now is that we would design and build the system differently, based on what others have commented and initial results.

[@mickdrew1968]

Good job and I enjoy your videos. One suggestion however, by pulling the air from the inside of the greenhouse you are putting mosture between the plastic and creating condensation. Thus reducing the light to your plants. If you pull from the outside you could reduce the condesation

[@diabolicalgenious]

I'm intrigued by this convection cooling for a greenhouse, and a good job DIY. My question, when watching your son building those tables was, why not go aquaponics?

[@guttormurthorfinnsson8758]

this is uesefull. thanks.

[@TimClymer]

Great to continue to see these updates! Keep them coming. We've used a compost thermometer to monitor ground temps (in addition to our digital sensor). Gives you a great idea of how "charged" the greenhouse is and we use one with a 36" stem so we can get down pretty far in the soil. Would love to see how your ground temps are rising! One suggestion on the inflation fan. You may not have a problem with condensation forming between layers now, but when the greenhouse is in "heating" mode going into the fall, you may have a problem in taking warm, moist air from the greenhouse and putting it between the film layers. We've even had the condensation freeze on cold mornings. We opted to have an external air intake for our fan using something similar to your jumper hoses and haven't had a condensation issue since. You might even be able to incorporate an inline damper to help with the pressure issue. I'm impressed, our second layer must not be tight or air-sealed because we don't get that kind of pressure buildup in our film. In terms of a thermostat they do sell two-stage thermostats with one heating stage and one cooling stage. We didn't use them because I was afraid of the amperage limits with our larger fans, but they'd likely work well for you with just two fans: www.greenhousemegastore.com/product/moisture-proof-digital-two-stage-thermostat/thermostats

[@JohnGuest45]

An STC-1000 would perform the same task for a fraction of the price. Its best to incorporate a differential thermostat to control the system. Standard thermostats can miss out on useful heat that could be stored (cooling mode) and in heating mode they will happily turn on the fan even when there`s no useful heat available from the mass.

[@TimClymer]

We use something like the STC-1000 in our high tunnel (actually two of them). Unfortunately it just has a single set point, meaning that it's trying to maintain a single temperature (single setpoint). You can set a differential, but it's always trying to get back to that single setpoint temp. In a greenhouse like this one you usually want a "dead zone", meaning when it's between a range of temperatures (say, 50F to 80F, maybe different if you're growing seedlings), you don't want anything to kick on. I haven't found a way to do that with the STC-1000 or one of the similarly designed thermostats that are available, unless they've added a different operating mode. We compensated for this by having two thermostats, one for heating, and one for cooling, which gives us the dead zone and both of which simply work to kick on our fans. That gives us both a heating setpoint and a cooling setpoint. Ours kick on for heating at 50F and cooling at 80F (we try to keep the cooling set to about 20F above ground temps in order to effectively bank heat, otherwise we aren't really "storing" heat) with around a 2F differential and the fans are off in between 50F to 80F. However, the thermostats we purchased aren't truly for greenhouse use and I'd feel far more comfortable going with one with a NEMA-rated enclosure. We bought these for our house: www.amazon.com/dp/B01KMA6EAM with higher amperage rating due to the larger fans we're kicking on. In retrospect, by the time we bought two thermostats, we likely could have just purchased the other one in the link above for a little more and had the piece-of-mind of a moisture-proof solution, if they would have a 15 amp version (our fans pull about 10-11amps when running full-on). I don't have any experience with the above thermostat but it has an adjustable differential and has the concept of a "dead zone" built in, which would seem to be what's needed. I've seen other folks with these types of houses simply have two greenhouse thermostats both triggering the fans to come on.

[@JohnGuest45]

Aye, you are right single setpoint but even two would be $100 cheaper than the stat in the link. STC`s can be run on 12v dc so theres no reason to use mains voltage if you prefer not to. Contactors mounted in an IP68 rated box will switch high current items safely. The issue with standard thermostats is they only use the greenhouse air temperature to decide when to turn the fan on and off ;) I use a standard and a differential thermostat (and fan speed controller) to control the fan. The standard stat provides a heating/cooling temperature crossover setpoint, the differential thermostat senses and compares the difference between the air and soil mass temperature. When the standard stat is above the setpoint, cooling mode is enabled but the fan wont run unless the air/soil temperature differential is met. No sense running the fan if the mass is too warm to efficiently store the heat. Heating mode is similar, if the air/soil differential is too small to deliver useful heat to the greenhouse, the fan wont run. If the heat in the mass is depleted while the system is running, the fan turns off. Standard thermostats dont care what the soil mass temperature is, they`ll happily run the fan all day and night ($$$) as long as the air temperature switching conditions are met ;)

[@TimClymer]

I'm curious about your differential thermostat. Is this a product that exists, or a solution you've engineered? I'd like to design a solution via raspberry pi that could take into consideration different factors (greenhouse temp, ground temp, etc) and switch different loads based on that. It'd also be nice to "ramp up" temps depending on season, so the low setpoint would gradually rise as we came into warmer weather. I've been manually adjusting setpoints based on my monitored ground temps but an automated system would be great. Do you have any documentation or videos on your setup? Would be interested to see it.

[@JohnGuest45]

Hi Tim I had to make it as i couldnt find anything to fit the bill off the shelf. I`m sure it would be very easy to do with todays tech but dont ask me how, i was around when b/w tv`s with valves and crt`s were considered cutting edge ;)

[@tuddsmithers7101]

Interesting thanks for the video.

[@StIsidoresFarm]

Our pleasure!

[@cai876]

Very inspiring video series, using a pressure switch is a great idea. As a mechanical engineer trained in fluid and thermodynamics, my main concern is that by blowing warm air from the inside of the greenhouse into the cooler polyfilm will result in condensation inside the cavity which could result in problems such as your timber rotting prematurely and the humidity in the air will also increase the conductivity of the air in the cavity. Improvement suggestions If you blow cooler air from the outside into the warmer cavity, the moisture holding capacity of the air will increase meaning you are much less likely to experience condensation. Putting in a small bleed hole would enable moisture which builds up in the cavity to escape. I would also suggest that you might be better off putting both circulating fans in series as opposed to parallel because they will develop much more pressure to overcome the high losses to resistance you will experience because of your long pipes.

[@livingsoilharvest]

Love this build. How has the unit performed over the last 3 years?

[@edbenedicto]

Hi, TheRealMartian on KZbin is a leader on automation of greenhouses. Cheers.

[@StIsidoresFarm]

Agreed - thanks!

[@Christian-bc2es]

It's coming together! I would make a record of outside temperature and inside greenhouse temperature. Record it each day at the same time. It maybe possible to automate it. You can then see the long term performance of the thermal battery and if improvements make a difference. I am planning a greenhouse and may take the time to do a thermal battery as well based on your experience.

[@StIsidoresFarm]

Once we get some decent instruments to measure, we plan to do that. Tim Clymer is using an app from Accurite that seems to give decent data at a reasonable price. If you build one of these, read the comments and really pay attention to what @johnguest45 says, as he really seems to know a LOT about these systems. We'll do another video at some point where we talk about what we should have done differently to get even better results.

[@revelae]

i love to see a benchmade that's torn up from actual use haha

[@handymanspecial7209]

What made you go with a geothermal vs intake/exhaust fans on a temp switch. Thsnks

[@danceufo9256]

From my experience, but please run a test, having slightly stronger pull on the exhaust end will reduce drag (producing less strain on your fans) and increase the amount of air coming out the exhaust. Also you may not even need a fan for pushing as the exhaust fan is doing most of the work anyway. Btw love this series. I'm learning a lot

[@stockaventureavecsly518]

Great settup , i use in mine to inflate it a 4 inch hydroponic fans with dryer docks and dryrer hook ups for the jumpers, with a knob to turn up or down the flow of pressure 70$ CAD less noise too, before i used a hair dryer till it blew up lol. since then no more problems with my 20x28x 15 high greenhouse. and for the hot days i have windows that opens up and close with bee wax cylinder that expands and retracts with no electricity and added a limit switch to turn the fans on/off without any intervention. so is my roll up sides.

[@johnboy7819]

I am near Charlotte and about to put a 40 ft greenhouse in the backyard. I was curious with the double layers in the winter how high does the temp get inside the greenhouse?

[@dannyacevedo5709]

I know Its almost a year later but did you get a thermostatic switch for the fans? I use Inkbirds from my projects, you can set them to turn on and off (hot,cold) with one device for around $30 each.

[@rroyiitzhak]

Awesome project, looks very useful. I have question about the underground pipes, is it closed pipe so water and moist can't enter the pipes or it is pipes with holes?

[@trebled99]

Love the channel. DID THE PRESS SWITCH WORK FOR YOU THANKS

[@miroslavnovotny5025]

Can you compare a winter temperature in geothermal and standard greenhouse? Your green house looks great. Thank you

[@db4027]

That pressure switch is cool. I was thinking a cycle timer or a fan speed controller/dimmer switch.

[@johnbrown7148]

Just use a cycle timer from a hydroponic store. I had same issue of to big of fan. My GH is 30x60x12. I cycled my fan on for 2.5 minutes and then off for 5 minutes.

[@siggyincr7447]

I know this is long after this project has been finished. But for those interested, the reduction in temperature at the outlet would probably explain a lot of the reduction in CFM at the outlet because as air cools it contracts in volume. So if your blowing 400 CFM of hot air in, that same air, without any leaks or other loses, would come out with less volume, i.e. less speed. If my memory serves the volume changes in proportion to the change in temperature in Kelvins. So a 30 degree drop is approximately a 10% drop in absolute temperature which should correspond to a 10% drop in volume and speed coming out of the exhaust.

[@michaelcarey1040]

It sounds like you could also use a regular outlet timer and run the fan 15 mins every 3.5 hours

[@jasone9]

Ok I'm seeing this way after the fact, but was just wondering if it would have been better to use a smooth inner wall pipe to reduce friction, loss of velocity, and increase in temp from the friction. Again, I'm asking not telling just wondered what y'all thought.

[@navang2844]

Great video. How do you install the Dwyer Pressure switch?

[@theageoftheawakening4806]

Pressure activated luvers and fan,and a variable speed control for the fan

[@audioalt]

Its working!

[@dreamboxx]

where did you buy al the stuf you used like the double greenhouse wall plastic film etcand what did it cost can you break it down ?

[@kaylynn3583]

DO I need additional wiggle wire for the install, or can I use the same wire for the first layer of plastic?

[@davidmastel5652]

Frictional loss is what slow air flow in the pipe. Smaller diameter loses more flow than larger. As diameter doubles volume goes to four times. You also get more heat transfer based on surface volume. Low flow and large volume is the most functional in both ways. Like a 10" diameter will slow flow with increasing volume...helps both ways... Blessing, Dave

[@maryquitecontrary5126]

I believe that when you measure flow rates, you need a length of straight pipe. The inlet side was adequate, but your outlet side had an elbow immediately behind where you took your measurement. So, that may effect the accuracy of the latter measurement.

[@nickguthrie9309]

Re the double poly wall. For 10 years or more I've used a 120 volt computer fan --solar GH of 250 sq ft glazing. No need to blow so hard into the gap. In fact the bigger the gap between poly layers, the greater will be convection looping hence heat loss. Where you have EMP or other connector touching the poly, use a bit of smooth-surfaced tape to reduce friction. Finally if you ever get wet snow you'd save your roof if there are horizontal members across the arches to fight the snow load

[@billgrubbs1]

If you turn the poly inflating fan off and on based on pressure do you lose pressure back through the fan or is there a one way valve on the fan

[@TFTWood]

I wonder if the loss in your volume of air is actually from the air condensing because it is getting colder. maybe check at night when the air going in is colder than the air coming out??

[@paulharrison5875]

It looks like it's been a few years since this project was completed. Is the greenhouse still in operation?

[@MrFlyTWA]

Wonder if a dual blower system would help with earth battery savings. One blower to push air into earth battery for night heating and other blower to draw air thru earth battery for cooling & recharging battery or vise versa? Have you taken any temp readings between pushing air and pulling air thru battery?

[@dannyfletcher6912]

I would use the same metal piping you use to build the greenhouse it might be cheaper than 2/4'S

[@IggyDalrymple]

Instead of the connector tube or dryer outlet hose, why not make few 6 inch gaps in the wiggle-wire? You could insert some sort of spacer to hold the 2 sheets of film apart. A course plastic mesh might work.

[@jcurt3161]

Air velocity (distance traveled per unit of time) is usually expressed in Linear Feet per Minute (LFM). By multiplying air velocity by the cross section area of a duct, you can determine the air volume flowing past a point in the duct per unit of time. Volume flow is usually measured in Cubic Feet per Minute (CFM).

[@michaelvaughn2287]

You would need stronger fans one more like the one used to inflate the house but depending how much tubing under ground it may blow to fast and not warm up enough.

[@richardcooney7789]

Just wondering ,what is the height at the center of the greenhouse . I,m building one that looks the same . Thanks Richard Castlegar B.C Canada .

[@wildfire53575]

hmm not a science geek but; feet of pipe per system "cubic ft" total, anyway you would convert cfm to psi to volume. you need to now your pipe rating tho for the flow rating

[@williesimpson8411]

Great series: It might be already tried, but I suppose the thought of adding exhaust fans on the return pipes to help pull the air that the intake air is pushing, would help??

[@StIsidoresFarm]

We actually tried it on one. It didn't seem to make a dramatic difference.

[@LivStream-TV]

@@StIsidoresFarm It is always easier to pull air, rather than pushing it. Have you placed the fans on the exhaust pipes?

[@StIsidoresFarm]

@@LivStream-TV Yes, we tried that. Definitely not as good.

[@mustafapolat2540]

I've discovered your amazing videos a bit late but I would like to ask a question to all, why this amazing method not being used commercially at larger scales by professional greenhouse operators? Whats the downside? Some unwanted/harmful gasses, temperature, humidity or cost of digging and installation for example?

[@gtrmanagement292]

Dude!!! I run inflation skins by the acre. All you need to do is plumb in an escape hose on the opposite side of the greenhouse and either just put a rubber flap over the pipe, or use a wife ball on a upward turned elbow, or the even just a laundry vent escape louver from home depot and it'll stay well inflated. You DO NOT WANT TO BLOW YOUR HUMID EXHAUST BACK INTO THE GREENY OR... RIG SOME OVERLY COMPLEX ELECTRIC PRESSURE SENSOR TO START STOP THAT CHEAP MOTOR. You can even just put plastic sheeting over an exhaust pipe, let it inflate and then poke holes in it until you get it tuned. If you need to get a proper inflation fan, or want a few tips, let me know. Also, had I seen all this before you started, I would have told you the "Earth Battery" you went with only works with tiny greenies, next time go with coils of poly pipe and circulate the water inside and you make it run through a heat exchanger in front of a fan, which for a greenhouse you can build out of pvc, or lazy guys will use more poly coiled up in front of the fan. I hope you have your exhaust fans ready, it gets humid in the winter, and hot in the summer. Looks good though.

[@JohnGuest45]

The fan in front of the heat exchanger will waste a lot of electrical power. I guess the water will circulate itself without needing a pump and more power ;) Consider the surface area of the heat exchanger and amount of greenhouse air being blown through it by the fan, it wont be very efficient for heating or cooling the greenhouse ;) Also, consider the temperature of the water will be same as the ground the pipes are buried in (the same as the buried ADS tubes) and the surface area of the buried coils will be far less than the ADS. Your idea will involve both air-to-water heat exchange AND water-to-ground heat exchange which is almost entirely by conduction (slow). You will need to insulate the pipe from the H.E to the coils so it cannt pick up heat (when cooling) or lose any heat (when heating) on the way. The SHCS only has one step, direct air to ground heat exchange which is both cheaper and infinitely more effective. Run the numbers for both systems and it`ll be clear which one will work ;) A differential pressure switch is no more complex than a basic inline on/off switch.

[@StIsidoresFarm]

Thanks for the taking the time to write. The pressure switch really isn't super complicated and it's not expensive. We'll see how it works and put it in a future video. And if doesn't we'll probably do a variation of several of the comments. We will have exhaust fans in there soon, as well as the shade cloth, and roll up sides (eventually).

[@1982MCI]

It sounds like the differential pressure switch should work but before you got to that part of the video it popped into my head that an easy fix would be to install a dimmer switch so you could lower the speed of the fan which theoretically should cut the cfm’s and keep from over inflating the house. You can also install flapper valves in your jumper lines so you can increase or decrease the amount of airflow to the end walls and anyplace you have jumper lines Take care guys, keep me updated on the plants so I can come get some

[@zachpw]

Don Pfeiffer Changing fan speeds can be sort of complicated, so you’d need to look at what the manufacturer suggests. I think it’d be easier just to divert some waste air.

[@karlInSanDiego]

Fan speed rheostats are something that is very tricky to acquire via mail order and be happy with. Some fans are built to work with some tiny digital units, but many fans will hum and the life of the fan will be shortened. Eventually, we moved to using big heavy variac units. They are a giant variable AC transformer with a big dial. They provide lower amplitude sine wave without clipping that you get from the small compact digital fan controllers. We bought one 40 year old one on ebay, and one brand new one from another online supplier. Watch the current rating on them, to make sure they will handle big things like your main exhaust fan. I believe you will eventually invest in circulation fans, and if you do, you can size your variac rating to run two circ fans. We bought Schaefer industrial grade Versa-Kool VK-12 fans and they have been our greatest heat dissipation asset as well as a necessary thing to keep the stale air off your stoma.

[@realwolfcry]

Did you install the Dwyer differential pressure switch and if you did, how did you install it and did it work as planned? I'm looking to use your automatic shutoff switch idea with my greenhouse inflation system as well.

[@davidneville456]

We installed Dwyer pressure switch but couldn't get it to read pressure

[@ktf585]

Ah you're using inflation! I thought you would go a more passive power saving way. Would be interested in how much power you spent per month. Now that you have this up and running, would be such a great study to build another one right next to it, going a more passive way.

[@bryceslazyporchgarden2521]

Another concept I like is digging out a trench or like a pond three to four feet deep on the Southside and then taking the dirt and putting on the outside north of the greenhouse building a dirt wall that way on the North you have a dirt wall that absorbs heat and then you have the greenhouse which has plants and then also a fish hatchery. The water Hatchery will help retain the temperature and the 8 to 10 ft dirt wall will retain the temperature

[@RickWright722]

Bryce's Lazy Porch Garden yes I am Kuwait ... just starting the green House way and the heat is killing. Looking into thermal batteries as we have a farm pond . If we run a line through the pond it should help with our 120-150 degree reduction. I have not run across anyone doing this in desert climates yet?

[@danielanac5093]

what type of plastic foil do you use it for a greenhouse cover?

[@waltsilva6515]

Hello, after watching part 10 - I was remembering some of what I learned on the subject of hydraulics and aerodynamics - when the blower fan is working it has to defeat 1-the atmospheric pressure of all the air present in the pipe system, and 2-the air drag resistance of the 4" pipes given their ribbed structure. Have you done a quick test and tried, momentarily, putting one of the blower fans on the exhaust pipe? (pulling air) - This would create a drop in pressure at the output and the atmospheric pressure would rush air into the inlet pipe and air flow resistance in the 4" pipes would drop.

[@StIsidoresFarm]

We have not tried putting a fan on the exhaust pipe. Certainly willing to give it a try to compare. Thanks - we've learned a lot from the comments on these videos!

[@waltsilva6515]

When you get a chance to try this, use your anemometer on the air inlet to get a reading of the air speed. By comparing the, input/output, drops in air speed when the fan is "pushing" to when the fan is "pulling" - you can see which configuration is giving you the best performance. Thank you.

[@JoshWeaverRC]

@@waltsilva6515 Fans always do better to push. This is for both air and water.

[@MyLevelheaded]

If temperature drop at night is a real issue, I've been seeing water barrels lining the perimeter of the green houses painted black they charge during the day and as soon as the sun goes down and the temperature drops they yield the heat for hours. They are sealed so no extra humidity unless you want that and at season closure simply drain them...

[@Z71Ranger]

Where did you get the track and wire to hold the double layer of plastic...

[@StIsidoresFarm]

Greenhouse Megastore

[@royormonde3682]

Have you considered moving your inline fan down into the corner closer to your grow beds and continue that intake pipe all the way down the ridge, drill large holes on both sides or maybe a few intake holes scattered down the length into the pipe so as to draw the hot air across the whole greenhouse at the same time instead of drawing it from one place like you have here. Drawing from one place not only sucks the hot air there at the ridge but will also draw air from lower down in that location, in effect leaving some of that hot air in farther reaches in the greenhouse. Just a thought, I'm not sure about that system but working in home construction all my life I've learned that many return air vents scattered throughout the house is far more efficient than just one.

[@StIsidoresFarm]

I certainly understand what you are saying, and I think that in a house it's exactly what you want. In this case, we're actually trying to capture the hottest air in fall/winter/spring and pull it down into the earth where it is diffused across as much ground as possible.

[@royormonde3682]

​@@StIsidoresFarm I know what your doing with the air to moderate the temperature all year long and extend your growing season. My point was that your collection of that hot air was not as efficient as it could be if your still hitting temperature in the 90's, that's all. It may help others also, thanks for the video.

[@Itsallmeagain]

Maybe just the change of air density due to the drop in temperature explain the low air speed returning into the greenhouse.

[@nguyenpham-uh1qu]

where did you get the door for the greenhouse from? thank you

[@441rider]

It would be interesting to bury a septic tank or square shipping tub as a heat retaining void to reduce back pressure and increase vol surface area to dirt as well.

[@jaredanderson7494]

Almost over engineered, really nice

[@oldsmagnet]

A few comments scattered around about the speed differences being due to temperature change - I'd add that you're probably also losing some airflow efficiency due to the perforated pipe bleeding air into the dirt. Another comment posed a question of push vs pull for best results - from a physics standpoint I don't know if it'd make any difference, apart from the earth battery cooling the hot air from the pusher fan (it's going to produce it's own heat too) vs the puller fan heating the already cooled air - there's probably some variables relating to distance of piping, etc, to base whether that's an apples-to-apples concern or not - but relating it to my first point, a pulling fan will run the risk of sucking in dirt through that perforated pipe - my gut tells me you'd want to maintain a positive pressure in that underground pipe to prevent contamination.

[@StIsidoresFarm]

Spot on. We plan to show it in a future video, but because it has become so dry in the greenhouse the ground below has opened up cracks out of which air blows (probably from the 2' course of pipes). They're tiny spots, but spots of airflow just the same. So yes, the positive pressure must prevent dirt from falling back into the pipes (at least while it is running).

[@luckeychuckey70]

Can you do a video more in-depth on 5:47 dwyer pressureess switch

[@bryceslazyporchgarden2521]

I like the concept of forcing air down underground 4 to 6 feet and then across to the other end of the greenhouse and then having another tube that's independent that's a couple feet from the ground level that way the air that you put in from the 6 ft or 4 ft level will act as a battery and gradually creep up to the 2-foot level which would be your exhaust at night so you'd have two different structures hoses one is the lower is six to eight foot deep . heats up and as the heat rises and, At night you cut the bottom one off and you use the top one , The one that's two foot below and under extreme conditions you can use both of them you'll be taking the temperature 45 to 50 degrees from the ground underneath the lowest pipe and then you'll be taking the battery the heated up air from the top part hose so that would work great . In effect you'll have two batteries. I know that's too late now for this greenhouse but on the next ones that is a concept to consider

[@JohnGuest45]

Heat moves downwards in the ground as well as upwards so the 45-50F may not stay that temperature for long. Make a box out of rigid insulation board, 2ft high and1 foot square internally. Fill it half full with oven dried soil taken from the greenhouse site. Place a heatmat on top and put another 12" of dry soil on top. Install temperature sensors every 2" above and below the heatmat. Turn it on and monitor the sensors to see how the heat moves and how long it takes to move. The test results will reflect your unique soil type, ie; clay, loam, sand, high organic content etc, different types will not give the same result. Using bone dry soil provides the slowest heat movement (the worst case scenario). Very few folks do practical experiments to find the answer but imho its the only way you can be sure its correct.

[@liamarmstrong1836]

The wind speed would of course go down. The volume of air going in is less than the volume coming out because the air is now cooler and more dense. Bernoulli works.

[@StIsidoresFarm]

We probably should remember this from high school physics class 😂 - thanks!

[@BuhlerAir]

Just watching this now... but when measuring air speed in a pipe either for FPM or CFM, especially right by an elbow you need to measure center, top and both sides and find the average. an elbow throws more air up against the opposite wall of the pipe until about 3x the diameter of the pipe itself. Just thinking that might change some numbers for Ya! LoL

[@michaelvangundy226]

HGI sells a tape that is the 6 mil greenhouse plastic. Lasts for ever. They have all of the controls and lots of friendly customer service.

[@StIsidoresFarm]

Thank you very much for this tip - we really are grateful for all these little bits of information people share with us.

[@rustycrumpet]

I think air volume and speed is reduced because of the hot green house air condensing when it goes into the battery.

[@niallwildwoode7373]

How did you gauge the amount of slack in the poly to allow for inflation? Or did it stretch itself to accommodate once you started the air flow? Cheers

[@StIsidoresFarm]

We pulled it as tight as we could when installing. The endwalls seemed as tight as a drum, but amazingly inflated out like huge pillows. Seems the film has a LOT of stretch in it. The website that sells the film put a square yard of it in spring lock base and the loaded weights on top of it to see what it took to rip. Ended up being over 400 pounds!

[@niallwildwoode7373]

St. Isidore's Farm That's perfect! Thanks for the info 😊

[@SuperCanada89]

taping a garbage bag and timing how long it takes to fill will give you an idea how many cubic feet the fan is pushing.

[@jerryperdun4833]

Can you share the wiring of the switch to fan?

[@evil3gamer]

So, I think the reduction in F, that y'all are seeking to get, is impressive! So tell me this. Is it actually cheaper running those fans year around than running heating and ac like you would in a house? If so, makes me wonder why everyone doesn't do this for their home AC

[@buikhai1]

You can use the Ideal Gas Law PV=nRT to solve your calculation problems. Your Velocity is reduced due to the air getting colder (temperature is reduced) at the output. Ignore the n and R for simplicity. Since they are pretty much constants. Your Equation PV=CT, C=constant. If Temperature goes down (Right side of the equation), PV will also go down directly (RIght side of the equation). The Air is denser so the flow is slower in speed. Remember, Air is compressible. In your case, the air volumetric is less on the output due to the effect of Temperature difference. The total amount of air is the same for input and output: This is the law of Physics. PV=nRT P = pressure V = volume n = amount of substance R = ideal gas constant T = temperature

[@moganfritz]

i live in Canada and I have a small 8' by 8' greenhouse and have installed a heat sink / climate battery that runs into a 2' by 2' by 4' pit. it seems to work pretty good although I have not ran any numbers. I just wondered if there was any way to hook the output into the double wall of the greenhouse???

[@StIsidoresFarm]

Funny you ask this - we wondered the exact same thing. One of the challenges, as we understand it, is that condensation will build up between the layers if you use air from inside the greenhouse. That seems like a real possibility.

[@moganfritz]

St. Isidore's Farm I am just spitballing here but aren’t you using the air from your greenhouse to fill the double wall. And my understanding of my climate battery is that it should take the condensation out. So if my output runs into the wall and I have a valve or even an output that comes out of the double wall and back into my greenhouse. Circulating the air throughout. Anyways thanks for responding.

[@StIsidoresFarm]

Yes, we are for now, but we're also not running it in really cold weather when condensation between layers of film might be more significant. We really did think about a splitter off the the return pipes to inflate the film. Still might try it just to see if it would work.

[@henrinaths1]

Imho air flow has to be factored with/ include thermal expansion and contraction. The air at 90+degrees will be a larger volume than the volume of the exhaust at 35 degrees. Thank you for your vid. You obviously like thinking things thru and figuring out every aspect of the physics behind the environment. Having said that I have a couple of question you might be able to answer for me. (Let me back up the truck for a second.. I’ve been wanting to do an earth battery ever since I saw how the Romans heated their enormous stone structures with similar installations. Aka thermal heat sinks. What peaked my interest is that you mentioned you built primarily on a clay bed, which is exactly what I have; no topsoil just clay.lol and river rocks. ) Q1, What I need to factor in for the efficiency equation is your latitude. I’m at the 55 degrees latitude. The depth of the pipes will make a huge difference for the efficiency. Q2, what is the depth of frost for your average winter? Our average here is close to 4ft. I’m thinking with a trencher install a perimeter thermal barrier say 2” styrofoam. Thanks again and thank also anyone that wants to comment. And or that has maybe a chart of latitude / soil mean temperature. ( google was no help )!

[@StIsidoresFarm]

Yes, all clay here. Piedmont North Carolina frost line is 12".

[@henrinaths1]

@@StIsidoresFarm Wow thanks for the reply. After I wrote all that I noticed your vid was 2 yrs old One more question if I may How do you rate your green house efficiency wise and what if anything would you do different? I hope you enjoyed 2 yrs of fresh vegs.

[@rogerharrison7619]

Effectiveness of system ! I respect and admire not only you but also the family members and their efforts, so if the effective scale was based on efforts you all get 110% A +... unfortunately not so. Air and water flow share some principles - both travel in direction of least resistance. That being said - consider/experiment (fan moving air the range/area fan is actually moving air from) hmm ponder that thought. Instead of open free range only one specify area - would it be more effective to have duct work for intake to 4 or more locations for each fan forcing hot air being sucked into intake? Another discussion is the air from outlets is restricted to corners only and heigth. Wouldn't it be more effective if the cold air was released at a higher level and distributed thru duct work and released at several locations? Just thinking the cool air only in corner has little if any affect on temperature in center. Once cool air is released it drops not being pushed around evenly throughout. Theory. Certainly the temp reading at outlet substantial 30 degrees difference but just right there one tiny location site - need many more - in principle you wouldn't expect an AC system to be effective to cool such a large area with only 4 little outlets. Awesome job - great attitudes, loving kids and family!!!

[@timyeager3812]

You need a vent in ceiling on both ends to let heat escape, heat rises.

[@IggyDalrymple]

Just food for thought, but instead of burying all that air pipe, why not have a welldriller install vertical double wall pipes filled with water with pumps circulating the water through a radiator/heat-exchanger? If the welldriller is cost prohibitive, consider hiring a deep trencher to bury pex pipe as deep as possible over a wide area (not necessary to stay within confines of the greenhouse to pipe closed loop water through radiator.

[@karynlee9632]

I think its your 6" pipe manifold. Thats why i asked if it was a clos3d system. Think of how water flows in the place of air. Do you have a bunch of turns & bends for the air/water to travel? 😮

[@easoregon270]

Mind linking where u got your film?

[@StIsidoresFarm]

www.greenhousemegastore.com/product/4-year-greenhouse-film/6-mil-polyethylene-film

[@jaredanderson7494]

The pressure guage is genius

[@katherinemcallister5310]

What size is this greenhouse? Thanks