Interesting! I met a man named Richard Nelson, who invented a system where you insert very thin (dry-cleaning type poly)tunnels between the layers at each end of these ducts there was a fan, on which was adjusted a screen, drippping with dishwashing soap & water was dripping . The result was to fill the ducts with gazillions of tiny bulles. Once done with the insulation need, just blow the bubles up against the creen at the other end, recouperating the solution in a closed circuit. But what was truly mind blowing in his project was that he had placed the greenhouse structure over a surface made of a water retention bassin filled with large rocks opn the inside of the external layer, he had water slowly dripping from the apex. Water was thus heated, and stored underneath the structure. At night, in the desert, very cold temperature is the rule. Richard's soap ducts system insured a superior insulation against heat loss, thus conserving and slowly consuming energy stored under the greenhouse. I don't know what happenned to Richard or his designs. At the time the Canadian based company he owned with his wife was called Thermagrow.
you all probably dont care but does any of you know of a way to log back into an Instagram account? I was dumb forgot the password. I appreciate any help you can offer me!
@Lennox Hunter thanks so much for your reply. I got to the site on google and I'm waiting for the hacking stuff now. Looks like it's gonna take quite some time so I will get back to you later when my account password hopefully is recovered.
Thank you for the information. There sure are a lot of inventive folks commenting and overthinking answers for problems that do not occur. I appreciate the simplicity.
Hello, great job! I have a question about the exhaust. Are you just pushing back the air between the layers and what vent are you using? Thank you, sir and once again, amazing!
Curtis, do you use different types of poly for the two layers? If so, how did you determine what types to use? I'm looking at buying poly for my hoophouse soon. Thanks!
I would appreciate a video of the actual installation of the blower into the greenhouse plastic walls. Actually, if you erect another such greenhouse, a video of its erection and covering would be appreciated by me and I dare say, everyone with an interest in such an activity.
Thank you so much! I am building a passive solar green house in an area of South Africa that has regular frost in winter during the night. Now I was looking for some type of fabric I could use to roll down the plastic cover during the night as insulation. Found nothing so far. Then i revisited your video on the double layer plastic which seems exactly what I need. One concern I had was the fact that it's a curved area - until you moved to speak about your second green house you planned on covering, because that has a curved area too. You didn't seem concerned about that fact. Is it not necessary to put any spacers between the two layers? you just cut the sheet a bit longer then the first one and the blower does it all?
On my GH I have 2 layers of poly separated by 1x2 boards on each rafter and stud. The poly is tight so I have a 3/4" gap between the layers. Does this give the same effect as the blower system?
The blower compresses the air, somewhat, so gas laws say it warms the air, somewhat. Also pressurized air prob'ly has a higher R-value. But you could build the inner layer farther from the outer layer, and achieve whatever you wanted.
Sorry I'm late to the party, but I would mount the blower 90 degrees to how you have it mounted. The way you've mounted it now forces the bearings on the fan and motor shaft to ride on the side of the bearing races. This will shorten the life of the bearings, and you'll need to replace the worn bearings or the whole fan earlier, whereas mounting the motor shaft horizontally allows the bearings of the shaft to run in the center of the races. Otherwise, beautiful greenhouse!
Very very EXCELLENT! Does the plastic have UV protection, and if so how many years is it rated for? I purchased some greenhouse plastic end pieces (at a big discount from Grower's Supply) for my low tunnels that had a coating that allowed sunlight to enter but reflected back into the greenhouse the long-wave heat radiation. Do you buy special greenhouse plastic or just inexpensive local stuff? Your Northern location does not have the intense sun radiation like the South. What is the longest you have had plastic up without it falling apart.
that’s an awesome idea ..i’m thinking of this with a solar panel to run the fan….silly question but don’t you need the sun light to get through the poly?? or is the diffused light enough ??
came across your channel today and was viewing this video. a lot of things got clarified for me Sir. One question , may I know the thickness of the poly I must use .Is 200 micron a good quality ? Please clarify.
If the inlet to the blower was being taken from outside. Would that solve the moisture between the plastic . which I assume if you have air and moisture you will have some type of mold growing. Working an indoor garden is important to have fresh air 2 cycle and control the humidity in the growing area. I assume that's the same with a greenhouse. Thinking about putting my own hoop style greenhouse in.
great video! more details on how you fix the hoses to the poly in such a way as to support the hose/blower. The question that would be helpful to answer for us is how many CFM does the blower provide? Rather than current draw, what the Cubic Feet per Minute rating is the key variable... Again, thanks for sharing this!
Great video! I work in the greenhouse business and we have installed blower using inside and outside air. Not much difference with condensation but drain holes are helpful. There are pressure relief valves you could use instead of a open pipe. The wiggle wire - great invention!
I have done it -- because i could not finance as formal of a greenhouse yet: I have two caterpillar tunnels and when we took one down for the season we doubled up the poly on the one we left up for winter... went from holding around 40-50 throughout a 30 degree day to between 70 and 80 degrees farenheit. no fans except the couple we have inside tunnel simply for air circulation.
Curtis I have a question about the benefits of using this in the summer. Does it have a benefit in decreasing solar heat gain or does it actually increase solar heat by trapping? I can’t find an answer anywhere and hope you can help.
The concept is sound but true R-value is achieved by 'trapping' air. With the air flowing wouldn't this just act as a heat exchanger? I want to build a small greenhouse and all your videos are great. Thx👍🏼
Yeah, it's a heat exchanger. He's heating up the space in the winter between the poly walls. Blow the air in from just above the ground in the greenhouse, let the sun heat it between the walls, exhaust the now hotter air into room. It's using the sun's radiant heat to heat the space between the two. Since you're using greenhouse air as the supply air, it being already warmer, you get a little better performance between the walls than you would just with one layer and allowing whatever radiant heating would occur. There is a bit of a blanket insulation effect because the air of the greenhouse and walls is mostly static; it's the same air.
I agree with your concern here. I am not convinced that it is a good idea to blow air in between the two layers of plastic : he might as well have just installed 1 layer to begin with. It would have been a better solution to install some kind of spacer in between the two plastic layers during construction. I imagine peices of styrofoam would work well
He's just blowing the air because otherwise a small tear means that the whole thing deflates slowly and surely. He says as much in the video (4:14), and it's correct that it is unnecessary for just producing a sufficient thermal resistance. If he/the guy who came up with the system knew his film would never have small tears in it, then they would not circulate air at all and just leave the walls as big inflatable mattresses. The air flowing goes inside of the greenhouse too, so we aren't really worried with exchanging heat from a hot place to a hot place. None of the circulating air is from outside
@@thehealthpolicychannel1229 Since he's using wood-frame construction, he could just staple/attach one layer outside and one layer inside of the framing, and it's an instant R3 or R4 (the space between the layers is how R-values are measured for air at standard temp and press, I think). i'm not sure where he's getting the R5 from, assuming the plastic layers are only being kept apart by air pressure. Pressurizing the air warms it a bit, and the compressed air has higher R-value than ambient. My idea was to build a Russian-doll sort of greenhouse, with one inside the other. The R-value achieved would be the thickness of the dead air space between the inner and the outer. No blower running all the time. Why do DIYers always love to hear things clanking and whirring? You know. Like the guy with the wood-gas truck and the wood-gas tractor. Neither have decent mufflers. They just really like the rattle-bang. Probably grew up providing sound effects for their Tonka trucks. I'd use a small blower connected to underground pipes, to use passive geothermal to regulate the temp beyond that.
@@harrymills2770 It could be that he is concerned about the thermal bridge effect; in your example, the wood framing would transfer heat, whereas if the outer layer of plastic is inflated, there is no thermal bridge. But he should have addressed that in his video.
... best of luck with your new greenhouse... hope you have an easy to get to place right by the driveway...easy to get in to and haul stuff too ... I like the heavy weed barrier plastic for flooring...but really a dirt floor works ... figure out how to save and transfer rain water for use in the greenhouse ...going on year 24 with my hobby house ... 10 X 20 Polly hooper ...
MrFarmer1997 it's about relative humidity warm air holds more moisture then cold warm moist inside air when it comes in contact with cold, the moisture drops out. happens to ships that load in the tropics , thousands of gallons have to be pumped out. Curtis is in high desert, or semi arid. he only has a small problem with moist air.
What happens to the greenhouse when it snows a lot outside? I can see that the snow would help with insulating however does it put stress on the greenhouse? And how do you deal with that? Also how do you deal with the inside of the greenhouse if it drops a certain temperature? Does that R factor stop the ground from not freezing?
Can the fan be on the outside? do you loose heat by pumping the warm air into the void? Or would it cool the greenhouse down too much during the winter f you blew the cold air into the void?
double poly has a k-value of 4 Dynamic modeling and simulation of greenhouse environments under several scenarios: A web-based application Efrén Fitz-Rodrígueza,∗, Chieri Kubotab, Gene A. Giacomellia, Milton E. Tignorc,Sandra B. Wilsond, Margaret McMahoneaDepartment of Agricultural and Biosystems Engineering, University of Arizona, 1177 E. Fourth Street, Shantz Bldg #38, Room 403, Tucson, AZ 85721-0038, USAbSchool of Plant Sciences, University of Arizona, 1140 E. South Campus Drive, Forbes Building, Room 303, Tucson, AZ 85721-0038, USAcNatural Resources Department, Haywood Community College, 185 Freedlander Drive, Clyde, NC 28721, USAdDepartment of Environmental Horticulture, University of Florida, 2199 South Rock Road, Fort Pierce, FL 34945-3138, USAeDepartment of Horticulture and Crop Science, The Ohio State University, 248B Howlett Hall, 2001 Fyfee Court, Columbus, OH 43210, USA
Curtis, if you put the fan on a variable switch, you can control the pressure and get the inch column of water needed. This way you won't stretch your plastic over time.
Thanks Curtis for the run down. I’m in Jakarta urban area and how about 500 sqm of yard. I havre read your books and now prepared to grow hear. With hot topical weather climate whats the best way to start.
Jakarta? Put a stick in the ground and it'll sprout. I doubt a Canadian veggie farmer in a dry climate can recommend how you start in a humid tropical climate. I think you need to learn from what's growable in your area. Start looking at seed catalogues and checking out more local farmers and markets.
... there’s a damper lid on mine to reduce the pressure if needed ...right on the fan ... ready to change my Polly this week myself ... have a great spring here in zone 6 ...
On my greenhouse, I've given up on those little fans. They have crummy little sleeve bearings and just do not handle the long hours of running. But this fan is optimized for producing high static pressure and you won't find a small fan with better bearings that will replace them. I went with a larger fan that replaces the 6 small ones that my double bay greenhouse used to need. (it has poly walls). I have a whole box of little junk fans (that had to be replaced in the middle of the night etc) if you want them.
Very simple yet very effective...thanks for uploading...need to build a largish (6' x 10') unit for the front of my house for winter flower and shrub protection here in Alabama...great insight now.
Hi Curtis, thanks for the videos and the tips about double layer inflated. I have set a second Poly layer in my greenhouse. The system works but I have some points where the gap between the two layer is really big up to 20 cm and other parts is really narrowed. Moreover, I have still condensation in the inside poly sheet. What can be the cause of these issues? Thanks for your support.
Awesome stuff. Do you have a video about how your "channel locks" are designed ?? Would help me understand how you sealed it and connects the poly to it
So it is basically blowing air from inside the greenhouse to the space between the 2 polys to get rid of the condensation and to insulate? If so, does the greenhouse have inlets to let air in?
@@JohnGuest45 Naw, then it'll be too cold in the winter. You want to gain heat. The air in the greenhouse, and in the walls is a mostly "static" volume. It's just with the additional layer of poly, his greenhouse air is not adjacent to cold outside air acting like a perpetual heat sink in the winter.
@@d-rot If the cover is well sealed it will only need filling once, the rest of the time the blower is simply maintaining pressure. A still air situation is hard to acheive when it involves a flexible wall, every time the wind hits the cover the air inside wont be still. Still air will not prevent convective currents being set up inside the cavity as they are driven by temperature difference. A vertical cavity is worse than a horizontal cavity in this respect. Convective currents act like a conveyor. transporting heat from the inner wall (warm) to the outer wall (cold). I use air inflated poly with 2 seperate cavities (triple glazing) made up of individual compartments rather than a single large cavity.
hello and thanks for sharing do you have another video on the actual construction thanks i live in the middle east where temp can get to low 50c during peak of summer and it would really help if you can share how its done..thanks..so much
I like your houses! I am a struggling person who is trying to supplement income by growing some things 3 or 4 seasons long,(not make it a business)i would be happy to add 200 to 400 dollars a month to my income.so you can see, i want to put up something small and cheap. i live in southern IL. January and February are our coldest months. i want to do a double wall system, on a full arch house about 8 to 10ft long.(small) so my biggest concern is construction costs. i will do all the work myself. but i will likely need to cabbage a blower from a clothes dryer or something. what i don't know how to do is put the plastic on an arch. do i use a channel lock? is that something i have to make? How? or is that something one can buy? what about the ends? i dont want to hard wall the end if i dont have to. unless its best. (added material costs) i plan to pick up a blue plastic drum monday or tuesday for $10 (was used for vegetable glycerine)for my water resevoir. i was planning to lay the plastic out on the flat ribs first. then attach it somehow. then pull the sides together with some load tie ratchet straps. if you see problems in my plan let me know. i dont know how to attach the plastic on the ends.
is the blower really necessary? wouldn't you get the same effect by stapling one layer of the poly on the inside of the beams and posts and wrapping the other on the outside?
You made a wise choice with the double-walled polyethylene. The pricey Palram Thermaglas 8mm twin-wall polycarbonate is rated at R-1.72, whereas your setup is in the neighbourhood of R-5.00 It's difficult to argue with that!
Hi Curtis, thanks for all your great information! Regarding inflator blowers if you draw your air from outdoors you will not get the condensation between layers! Thanks for being such an inspiration, keep up the outstanding work!
This is not true from every other grower I've seen. If that works for you, send me a picture of your greenhouse. Nobody I know in a cold climate does that.
Ok, will do. I'm in NH using a Harnois oval tech with blower mounted outside under a small metal hood. Second Harnois has rigid poly roof with inflated side roll up walls. Again, blower mounted outside. Never had condensation between poly film regardless of temps.
is it a better idea to install two layers with a bigger gap between them like 4 inches or more and without using a blower? are you losing BTUS BY pumping warm air from the inside between the two layers?
Good question. Yes, heat is being lost but a smaller gap is better. It takes less energy to maintain it but expanding it will not increase the R value. The air layer at near the inlet is being cooled by conduction with the exterior. At some point, several feet from the inlet (farther from the inlet for a 4" layer than a 1" layer), the air is so cold it is being warmed by conduction with the interior layer. There is turbulent mixing through the entire closed volume so it doesn't matter how thick the layer is. The rate of conduction is directly related to the difference between the two temperatures. By providing two conduction layers between the interior and exterior, the total conduction is lower. Putting in 2 layers of air would require another layer of poly but that begins the diminishing returns on investment. It would entail a complicated bit of construction every 4 or 5 years. To work for the entire greenhouse, the assumption is that total heat gain from sunlight is greater than total loss by conduction.
@@briansmith6824 why is a smaller gap better? If you have a wider gap you don't need a blower to keep up the gap. Only reason for the blower is to keep the plastic separated as it might fall/stick together with a small gap.
Fantastic! THANK YOU for sharing! I too have been struggling to budget for the clear corrugated roof panels, so this will be my more affordable solution!
I used to have a huge greenhouse but I am working on a new one and would love to have a business like you. I have 3 acres but maybe 1 acre is usable because of the giant trees and a pond. Anyways I picked up a great blower like this at a yard sale this past weekend for $2......I think I paid $70 for my one before.
So nothing physical like purlins or swiss-cheesed 2-by's or spacer blocks? What happens when you get moderate to heavy snow accumulation? That little blower can huff & puff & never blow those films apart.
look at steel garage designs and substitute polycarbonate rather than steel cladding. Had a 30x55 garage in Louisiana that stood up to Rita without any damage.
If you take air from outside instead of in the greenhouse for the fan you will get less condensation between the layers. Greenhouse air is usually pretty humid
It's a good practice but the air have to be taken from the outside. As you can see, there is a lot of condensation between the two plastic layers. this is due to the condensation of moisture in the warm air that comes into contact with the outer layer.
these " How I do things " vids are great
they have answered a lot of techy questions I have had
Interesting! I met a man named Richard Nelson, who invented a system where you insert very thin (dry-cleaning type poly)tunnels between the layers at each end of these ducts there was a fan, on which was adjusted a screen, drippping with dishwashing soap & water was dripping . The result was to fill the ducts with gazillions of tiny bulles. Once done with the insulation need, just blow the bubles up against the creen at the other end, recouperating the solution in a closed circuit.
But what was truly mind blowing in his project was that he had placed the greenhouse structure over a surface made of a water retention bassin filled with large rocks opn the inside of the external layer, he had water slowly dripping from the apex. Water was thus heated, and stored underneath the structure.
At night, in the desert, very cold temperature is the rule. Richard's soap ducts system insured a superior insulation against heat loss, thus conserving and slowly consuming energy stored under the greenhouse. I don't know what happenned to Richard or his designs. At the time the Canadian based company he owned with his wife was called Thermagrow.
you all probably dont care but does any of you know of a way to log back into an Instagram account?
I was dumb forgot the password. I appreciate any help you can offer me!
@Moses Ivan instablaster =)
@Lennox Hunter thanks so much for your reply. I got to the site on google and I'm waiting for the hacking stuff now.
Looks like it's gonna take quite some time so I will get back to you later when my account password hopefully is recovered.
@Lennox Hunter it did the trick and I actually got access to my account again. Im so happy!
Thank you so much you saved my account :D
@Moses Ivan You are welcome :D
Does the fan say anything about how many cubic feet per minute/ CFM or the revolutions per minute RPM? Thanks
Thank you for the information. There sure are a lot of inventive folks commenting and overthinking answers for problems that do not occur. I appreciate the simplicity.
Does the double layer have any benefits during the summer?
Hello, great job! I have a question about the exhaust. Are you just pushing back the air between the layers and what vent are you using? Thank you, sir and once again, amazing!
You rock Curtis, simple and quick
Where did you get those galvanized 45,s you used for your hoops?
I wanna try something like this in Quebec. You think it'll be too cold? I want to buy your book too, is it still available? Thanks for all you do!
Thanks for all the great information
Curtis, do you use different types of poly for the two layers? If so, how did you determine what types to use? I'm looking at buying poly for my hoophouse soon. Thanks!
What is the CFM of the blower you are using?
Does this work for hot climate areas?
Do you have to rack the snow off the top layer to keep that bubble up?
No. It melts on contact.
How's your mold ,is this the first year you have done this ?
Great idea! Congrats Curtin, and thanks for sharing! What difference of temperature can you reach with this system?
where did you get the fan from? thank you
I would appreciate a video of the actual installation of the blower into the greenhouse plastic walls. Actually, if you erect another such greenhouse, a video of its erection and covering would be appreciated by me and I dare say, everyone with an interest in such an activity.
Thank you so much! I am building a passive solar green house in an area of South Africa that has regular frost in winter during the night. Now I was looking for some type of fabric I could use to roll down the plastic cover during the night as insulation. Found nothing so far. Then i revisited your video on the double layer plastic which seems exactly what I need. One concern I had was the fact that it's a curved area - until you moved to speak about your second green house you planned on covering, because that has a curved area too. You didn't seem concerned about that fact. Is it not necessary to put any spacers between the two layers? you just cut the sheet a bit longer then the first one and the blower does it all?
What was that little thingy hanging there?
On my GH I have 2 layers of poly separated by 1x2 boards on each rafter and stud. The poly is tight so I have a 3/4" gap between the layers. Does this give the same effect as the blower system?
yes as long as the 2 layers don't touch each other.
The blower compresses the air, somewhat, so gas laws say it warms the air, somewhat. Also pressurized air prob'ly has a higher R-value. But you could build the inner layer farther from the outer layer, and achieve whatever you wanted.
whats the temperature difference between the outside and the inside of the greenhouse during the winter?
What do you do with it summer? how do you deal with heat?
What poly did you buy in that quantity for less than $100? Is it not UV treated or 6 mil?
Sorry I'm late to the party, but I would mount the blower 90 degrees to how you have it mounted. The way you've mounted it now forces the bearings on the fan and motor shaft to ride on the side of the bearing races. This will shorten the life of the bearings, and you'll need to replace the worn bearings or the whole fan earlier, whereas mounting the motor shaft horizontally allows the bearings of the shaft to run in the center of the races. Otherwise, beautiful greenhouse!
what if you drive that exhaust pipe (3:27) into an underground pipe and then back into the greenhouse? will it work better? what do you think?
Very very EXCELLENT! Does the plastic have UV protection, and if so how many years is it rated for? I purchased some greenhouse plastic end pieces (at a big discount from Grower's Supply) for my low tunnels that had a coating that allowed sunlight to enter but reflected back into the greenhouse the long-wave heat radiation. Do you buy special greenhouse plastic or just inexpensive local stuff? Your Northern location does not have the intense sun radiation like the South. What is the longest you have had plastic up without it falling apart.
I'd like to see what kind of chanel Lock you used to hold the poly and how you hold the poly up
Could you achieve the same effect as bridging the tubing across panels by doing a couple of bore holes in the wood frame for airflow
that’s an awesome idea ..i’m thinking of this with a solar panel to run the fan….silly question but don’t you need the sun light to get through the poly?? or is the diffused light enough ??
Hello. Awesome information. Thank you. Where do you purchased the poly? How long will it last?
@5:05 that 115V AC fan at 0.65A is then 75W, which is 657kW/h per year of 24/7 nonstop running
came across your channel today and was viewing this video. a lot of things got clarified for me Sir. One question , may I know the thickness of the poly I must use .Is 200 micron a good quality ? Please clarify.
This totally make sense! Thanks, Curtis :)
If the inlet to the blower was being taken from outside. Would that solve the moisture between the plastic . which I assume if you have air and moisture you will have some type of mold growing. Working an indoor garden is important to have fresh air 2 cycle and control the humidity in the growing area. I assume that's the same with a greenhouse. Thinking about putting my own hoop style greenhouse in.
I'm building a SSG off-grid, so will try a fully sealed double skin with a tapped condensation draw-off and a pressure switched on/off for the blower.
great video! more details on how you fix the hoses to the poly in such a way as to support the hose/blower. The question that would be helpful to answer for us is how many CFM does the blower provide? Rather than current draw, what the Cubic Feet per Minute rating is the key variable... Again, thanks for sharing this!
How thick is the poly, that you are using, and where did you buy it?
Where did you buy the poly plastic?
Great video! I work in the greenhouse business and we have installed blower using inside and outside air. Not much difference with condensation but drain holes are helpful. There are pressure relief valves you could use instead of a open pipe. The wiggle wire - great invention!
Have you tried or heard of anyone doing a similar design but without active air-pressurization? Just two layers of laminate with an air gap?
No. I've never heard of anyone doing that.
I have done it -- because i could not finance as formal of a greenhouse yet: I have two caterpillar tunnels and when we took one down for the season we doubled up the poly on the one we left up for winter... went from holding around 40-50 throughout a 30 degree day to between 70 and 80 degrees farenheit. no fans except the couple we have inside tunnel simply for air circulation.
As long as you are sealed up wel dead air is a good insulator
Very informative, thanks buddy.
So is this only a winter thing or good for summer as well?
Do you get bad winds in your area? if so, how do your poly do in high winds? What about your little ones over the garden beds?
hello thanks for video. Can this greenhouse resist hail ?or it will be broken?
Curtis I have a question about the benefits of using this in the summer. Does it have a benefit in decreasing solar heat gain or does it actually increase solar heat by trapping?
I can’t find an answer anywhere and hope you can help.
Merci from Montreal, Canada.
Would this allow me to have a greenhouse in the AZ desert when it’s 120*?
The concept is sound but true R-value is achieved by 'trapping' air. With the air flowing wouldn't this just act as a heat exchanger? I want to build a small greenhouse and all your videos are great. Thx👍🏼
Yeah, it's a heat exchanger. He's heating up the space in the winter between the poly walls. Blow the air in from just above the ground in the greenhouse, let the sun heat it between the walls, exhaust the now hotter air into room. It's using the sun's radiant heat to heat the space between the two. Since you're using greenhouse air as the supply air, it being already warmer, you get a little better performance between the walls than you would just with one layer and allowing whatever radiant heating would occur. There is a bit of a blanket insulation effect because the air of the greenhouse and walls is mostly static; it's the same air.
I agree with your concern here. I am not convinced that it is a good idea to blow air in between the two layers of plastic : he might as well have just installed 1 layer to begin with. It would have been a better solution to install some kind of spacer in between the two plastic layers during construction. I imagine peices of styrofoam would work well
He's just blowing the air because otherwise a small tear means that the whole thing deflates slowly and surely. He says as much in the video (4:14), and it's correct that it is unnecessary for just producing a sufficient thermal resistance. If he/the guy who came up with the system knew his film would never have small tears in it, then they would not circulate air at all and just leave the walls as big inflatable mattresses.
The air flowing goes inside of the greenhouse too, so we aren't really worried with exchanging heat from a hot place to a hot place. None of the circulating air is from outside
@@thehealthpolicychannel1229 Since he's using wood-frame construction, he could just staple/attach one layer outside and one layer inside of the framing, and it's an instant R3 or R4 (the space between the layers is how R-values are measured for air at standard temp and press, I think). i'm not sure where he's getting the R5 from, assuming the plastic layers are only being kept apart by air pressure. Pressurizing the air warms it a bit, and the compressed air has higher R-value than ambient.
My idea was to build a Russian-doll sort of greenhouse, with one inside the other. The R-value achieved would be the thickness of the dead air space between the inner and the outer. No blower running all the time.
Why do DIYers always love to hear things clanking and whirring? You know. Like the guy with the wood-gas truck and the wood-gas tractor. Neither have decent mufflers. They just really like the rattle-bang. Probably grew up providing sound effects for their Tonka trucks.
I'd use a small blower connected to underground pipes, to use passive geothermal to regulate the temp beyond that.
@@harrymills2770 It could be that he is concerned about the thermal bridge effect; in your example, the wood framing would transfer heat, whereas if the outer layer of plastic is inflated, there is no thermal bridge. But he should have addressed that in his video.
Great information and build. Thank you for sharing.
... best of luck with your new greenhouse... hope you have an easy to get to place right by the driveway...easy to get in to and haul stuff too ... I like the heavy weed barrier plastic for flooring...but really a dirt floor works ... figure out how to save and transfer rain water for use in the greenhouse ...going on year 24 with my hobby house ... 10 X 20 Polly hooper ...
drawing the air from outside will help with condensation
another benifit is it acts like a pillow, absorbing energy frim wind gusts.
I could be wrong but I would think filling it with warm air from inside would be better insulation than cold air from outside.
MrFarmer1997 it's about relative humidity
warm air holds more moisture then cold
warm moist inside air when it comes in contact with cold, the moisture drops out.
happens to ships that load in the tropics , thousands of gallons have to be pumped out.
Curtis is in high desert, or semi arid.
he only has a small problem with moist air.
not practical, do you know how much that much double glazing would cost, and you only need it for the winter.
@Robert Slackware You're not achieving any measurable vacuum for 300 bucks with plastic poly sheeting.
Where did you get the hoses to run the air from one air pocket to the next? Im having trouble finding something similar, that is also cheap.
check out laundry dryer vent flex hose
Awesome tips, how would you in your opinion setup a 4×10 green house in 120 degree weather during summer and 30 to 70 degrees in winter?
Where can I get one of the blowers?
Did you pull both layers at the same time or different wiggle wire channels for each layer
What happens to the greenhouse when it snows a lot outside? I can see that the snow would help with insulating however does it put stress on the greenhouse? And how do you deal with that? Also how do you deal with the inside of the greenhouse if it drops a certain temperature? Does that R factor stop the ground from not freezing?
Can the fan be on the outside? do you loose heat by pumping the warm air into the void? Or would it cool the greenhouse down too much during the winter f you blew the cold air into the void?
Can you have the blower with roll up sides?
If you have holes in the plastic for drainage, how does the air stay between the layers?
Excellent info. Lot's of practical ideas fot not a lot of money.
R=5 insolation factor ? Are you guys sure about it ? Do you have a technical documentation about it ? Can't find anywhere.
double poly has a k-value of 4
Dynamic modeling and simulation of greenhouse environments under several scenarios: A web-based application
Efrén Fitz-Rodrígueza,∗, Chieri Kubotab, Gene A. Giacomellia, Milton E. Tignorc,Sandra B. Wilsond, Margaret McMahoneaDepartment of Agricultural and Biosystems Engineering, University of Arizona, 1177 E. Fourth Street, Shantz Bldg #38, Room 403, Tucson, AZ 85721-0038, USAbSchool of Plant Sciences, University of Arizona, 1140 E. South Campus Drive, Forbes Building, Room 303, Tucson, AZ 85721-0038, USAcNatural Resources Department, Haywood Community College, 185 Freedlander Drive, Clyde, NC 28721, USAdDepartment of Environmental Horticulture, University of Florida, 2199 South Rock Road, Fort Pierce, FL 34945-3138, USAeDepartment of Horticulture and Crop Science, The Ohio State University, 248B Howlett Hall, 2001 Fyfee Court, Columbus, OH 43210, USA
Curtis, if you put the fan on a variable switch, you can control the pressure and get the inch column of water needed. This way you won't stretch your plastic over time.
Better to let the blower run as intended and release excess air with a valve
Do you happen to have a link to the place where you bought the blower?
No sorry. I didn't buy it online.
@@offgridcurtisstone Can you tell me where you got that fan. I live in the OK.
Thanks Curtis for the run down. I’m in Jakarta urban area and how about 500 sqm of yard. I havre read your books and now prepared to grow hear.
With hot topical weather climate whats the best way to start.
Jakarta? Put a stick in the ground and it'll sprout. I doubt a Canadian veggie farmer in a dry climate can recommend how you start in a humid tropical climate. I think you need to learn from what's growable in your area. Start looking at seed catalogues and checking out more local farmers and markets.
what's the spacing between film sheets? is it feasible to stuff or drape industrial air pillows instead of fan?
This is a great system. They sometimes add pressure switch on it to stop the motor when the pressure builds up between layers.
... there’s a damper lid on mine to reduce the pressure if needed ...right on the fan ... ready to change my Polly this week myself ... have a great spring here in zone 6 ...
Curtis, from my research, the max R value I can find is R2. Can you point me to the documentation showing the possibilities of getting R5 ??
There is none that I know of. You're probably right.
so are both layers laid flat together before air insertion
With the double layer poly what does your house temp run during summer,winter fall spring?
On my greenhouse, I've given up on those little fans. They have crummy little sleeve bearings and just do not handle the long hours of running. But this fan is optimized for producing high static pressure and you won't find a small fan with better bearings that will replace them. I went with a larger fan that replaces the 6 small ones that my double bay greenhouse used to need. (it has poly walls). I have a whole box of little junk fans (that had to be replaced in the middle of the night etc) if you want them.
Another great video. You answered a lot of questions I had on double poly. Thanks!
Very simple yet very effective...thanks for uploading...need to build a largish (6' x 10') unit for the front of my house for winter flower and shrub protection here in Alabama...great insight now.
Hi Curtis, thanks for the videos and the tips about double layer inflated. I have set a second Poly layer in my greenhouse. The system works but I have some points where the gap between the two layer is really big up to 20 cm and other parts is really narrowed. Moreover, I have still condensation in the inside poly sheet. What can be the cause of these issues? Thanks for your support.
condensation on inside is normal in greenhouse. plants transpire
Anyone know what fan that is and where to get it?
Awesome stuff. Do you have a video about how your "channel locks" are designed ?? Would help me understand how you sealed it and connects the poly to it
Search 'Wiggle Wire'.
How long do the two layers of poly last? Or how often does it need to be replaced?
So it is basically blowing air from inside the greenhouse to the space between the 2 polys to get rid of the condensation and to insulate? If so, does the greenhouse have inlets to let air in?
Use outside air for the blower or you`ll have issues with condensation inside the cavity. .
@@JohnGuest45 Naw, then it'll be too cold in the winter. You want to gain heat. The air in the greenhouse, and in the walls is a mostly "static" volume. It's just with the additional layer of poly, his greenhouse air is not adjacent to cold outside air acting like a perpetual heat sink in the winter.
@@d-rot
If the cover is well sealed it will only need filling once, the rest of the time the blower is simply maintaining pressure. A still air situation is hard to acheive when it involves a flexible wall, every time the wind hits the cover the air inside wont be still. Still air will not prevent convective currents being set up inside the cavity as they are driven by temperature difference. A vertical cavity is worse than a horizontal cavity in this respect. Convective currents act like a conveyor. transporting heat from the inner wall (warm) to the outer wall (cold). I use air inflated poly with 2 seperate cavities (triple glazing) made up of individual compartments rather than a single large cavity.
hello and thanks for sharing do you have another video on the actual construction thanks i live in the middle east where temp can get to low 50c during peak of summer and it would really help if you can share how its done..thanks..so much
I like your houses! I am a struggling person who is trying to supplement income by growing some things 3 or 4 seasons long,(not make it a business)i would be happy to add 200 to 400 dollars a month to my income.so you can see, i want to put up something small and cheap. i live in southern IL. January and February are our coldest months. i want to do a double wall system, on a full arch house about 8 to 10ft long.(small)
so my biggest concern is construction costs. i will do all the work myself. but i will likely need to cabbage a blower from a clothes dryer or something.
what i don't know how to do is put the plastic on an arch. do i use a channel lock? is that something i have to make? How? or is that something one can buy? what about the ends? i dont want to hard wall the end if i dont have to. unless its best. (added material costs)
i plan to pick up a blue plastic drum monday or tuesday for $10 (was used for vegetable glycerine)for my water resevoir.
i was planning to lay the plastic out on the flat ribs first. then attach it somehow. then pull the sides together with some load tie ratchet straps. if you see problems in my plan let me know. i dont know how to attach the plastic on the ends.
Is it possible to do that over poly carbonate?
Thanks Curtis I have learned a lot from you. What do you do in summertime do you still run blower?
is the blower really necessary? wouldn't you get the same effect by stapling one layer of the poly on the inside of the beams and posts and wrapping the other on the outside?
Try it.
@@offgridcurtisstone I will! 😊
What is the problem if I do it without this fan or without air system
Would be great to show the temps outside verses inside. Looks great & gives me some ideas for winterization
You made a wise choice with the double-walled polyethylene. The pricey Palram Thermaglas 8mm twin-wall polycarbonate is rated at R-1.72, whereas your setup is in the neighbourhood of R-5.00 It's difficult to argue with that!
I am considering this on my greenhouse
Why not apply the second layer on the inside with the beams acting as spacer?
Hi Curtis, thanks for all your great information! Regarding inflator blowers if you draw your air from outdoors you will not get the condensation between layers! Thanks for being such an inspiration, keep up the outstanding work!
This is not true from every other grower I've seen. If that works for you, send me a picture of your greenhouse. Nobody I know in a cold climate does that.
Ok, will do. I'm in NH using a Harnois oval tech with blower mounted outside under a small metal hood. Second Harnois has rigid poly roof with inflated side roll up walls. Again, blower mounted outside. Never had condensation between poly film regardless of temps.
Ok, I would love to see how that is played out.
is it a better idea to install two layers with a bigger gap between them like 4 inches or more and without using a blower? are you losing BTUS BY pumping warm air from the inside between the two layers?
Good question.
Yes, heat is being lost but a smaller gap is better. It takes less energy to maintain it but expanding it will not increase the R value.
The air layer at near the inlet is being cooled by conduction with the exterior. At some point, several feet from the inlet (farther from the inlet for a 4" layer than a 1" layer), the air is so cold it is being warmed by conduction with the interior layer. There is turbulent mixing through the entire closed volume so it doesn't matter how thick the layer is. The rate of conduction is directly related to the difference between the two temperatures. By providing two conduction layers between the interior and exterior, the total conduction is lower.
Putting in 2 layers of air would require another layer of poly but that begins the diminishing returns on investment. It would entail a complicated bit of construction every 4 or 5 years.
To work for the entire greenhouse, the assumption is that total heat gain from sunlight is greater than total loss by conduction.
Yeh, this makes absolutely no sense at all. I was thinking the very same thing right from the get go.
It makes a lot of sense when you factor in building the structure to create a 4" gap.
@@briansmith6824 why is a smaller gap better? If you have a wider gap you don't need a blower to keep up the gap. Only reason for the blower is to keep the plastic separated as it might fall/stick together with a small gap.
Fantastic! THANK YOU for sharing! I too have been struggling to budget for the clear corrugated roof panels, so this will be my more affordable solution!
Thanks for your comments! Appreciated. All the best with your gardening/farming. Sincerly, Sunita - From The Field Support Team
I used to have a huge greenhouse but I am working on a new one and would love to have a business like you. I have 3 acres but maybe 1 acre is usable because of the giant trees and a pond. Anyways I picked up a great blower like this at a yard sale this past weekend for $2......I think I paid $70 for my one before.
hii Curtis,
what is the spec of the blower ? what is the power and Revolution per minute ? and the brand. where did you purchase it ?
thanks
I don't know. They're all the same. Search greenhouse supply stores for a blower.
How do you physically separate the 2 layers, and about how many inches separation between the 2 layers? Thanks.
Forced air.
So nothing physical like purlins or swiss-cheesed 2-by's or spacer blocks? What happens when you get moderate to heavy snow accumulation? That little blower can huff & puff & never blow those films apart.
The snow melts on contact.
Hey, do you know of any good plans for wood framed greenhouses resistant to high winds?
look at steel garage designs and substitute polycarbonate rather than steel cladding. Had a 30x55 garage in Louisiana that stood up to Rita without any damage.
Great video. What kind of greenhouse do you have?
If you take air from outside instead of in the greenhouse for the fan you will get less condensation between the layers.
Greenhouse air is usually pretty humid
Very interesting concept….
It's a good practice but the air have to be taken from the outside. As you can see, there is a lot of condensation between the two plastic layers. this is due to the condensation of moisture in the warm air that comes into contact with the outer layer.
Curious about the fan. Details or link would be appreciated. Thank-you.
...google jumper hoses .... or blowers ...
hi, whats the winter temperatures there?