John Steadfast

Trace Oswald wrote:No input on those products, but forums are notorious for not answering your question, and giving something else entirely, so here is my contribution.  Consider tempered glass.  Strong, great light transmission, and (although I know you said it isn't relevant), free.  Most any glass company will give you tempered glass that was not used because it costs them more to send it back than they get for it.  Tempered glass can't be cut, so if a piece was the wrong size or the customer didn't take it, it's no good to the company.  I have a dozen or more sheets that are at least 4 feet wide and 8 feet long waiting for a greenhouse build.  Just another avenue to consider.

:D Thanks for the "something else entirely" contribution. Yes, I looked into tempered glass, but it is a bitch to work with and requires a higher construction cost, because of it's weight. And I would be paranoid to use on a ceiling... Could have somewhat of a guillotine effect... especially when ISIS starts training suicide birds.

thomas rubino wrote:Hi John;  Just to confuse you more...   Look up Solexx. Not the rigid panels but the roll.
I can't recommend it enough!   Absolutely wonderful to work with and other than some discoloring it is still great in its tenth year.
Search around and you'll find they will ship the roll stuff free.

Hi Javadoc,

Thanks, I have already used Solexx and was mostly happy with it, but I just have much better results with higher LT. Stuff on a roll would surely make my life easier, but it just doesn't hold up compared to panels.

Hi,

Going through my options for a East-West oriented asymmetrical greenhouse. Let's not talk price, since it's not going to be a big greenhouse and I'm willing to pay for the right solution.
I really like Acrylite Alltop 16mm because of it's U-value and high light and UV-transmission. But I'm worried about it not having diffusion. The PC has diffusion, is less prone to breaking and much easier to work with.
The main negative factors are for Acrylite, me worrying about hotspots (please somebody tell me there is no need to worry) and for PC, that it doesn't allow UV-transmission.

Light transmission values are in the 90s for Acrylite and in the 70s for PC. Would light diffusion with an LT in the 70s generate more light that direct light in the 90s?
And again... Will I have hotspots?

I hope someone has had experiences with Acrylite Alltop and can give me some feedback.

James Whitelaw wrote:We’ve been thinking of warming strategies for a planned greenhouse. My sense is with any greenhouse a lot of the heat collects at the top and is wasted. I’ve seen some Chinese designs where there is a secondary layer of plastic deployed above the plants to keep warmth closer to the ground. One strategy is to install low tunnels inside of high tunnels (examples can be seen in this PDF). Warming mats under trays of plants seems a direct, less wasteful method than heating the entire space. Heated water in tubes would be another strategy.

Sadly the double plastic will not work for me. I would be going with Lexan Thermoclear twin wall polycarbonate panels.

Yes, I'm planning a medium sized one 6x20m or approx 20x65ft. Will be using twin wall polycarboante. Would like to go acrylic, but that's a whole other can of worms with contraction and expansion of the material and more expensive. Maybe one day...

Sena Kassim wrote:John, I had no idea those formulas existed. I reviewed with my hubby. We are very impressed. Nice work. You get an apple.

Thanks to you and Skandi for taking this to a whole new place. I really enjoy being a part of this community.
Y'all rock. ⛰️

Hi Sena, you are most welcome. Thanks for the apple!

http://www.ibpsa.org/proceedings/BS1997/BS97_P008.pdf Here is an in depth paper on the expert calculation tool. You can get the tool at the UNiversity Siegen website.

IF you prefer a simpler tool, you can use the climate battery calculator. http://www.ecosystems-design.com/climate-battery-calculator.html

William Bronson wrote:I've only read about smooth pipe used in earth tubes, where they have had issues mold.
Swabbing the insides with rags or pouring cleaners down the holes are some of the remedies.
Theses pipes are not described as being perforated.
In climate batteries, tubing that is corrugated and perforated reportedly avoids mold due to the actions of soil organisms.

I imagine a perforated tube without corrugations are better against mold than  ones with corragations.

Yes, earth tubes used for passive houses are usually smooth and non perforated. It is a different system. Some say a constant air flow, but  mounting a UV light at the intake should deal with most mold issues. A climate battery ideally sits directly below the greenhouse.
Most climate batteries are made with perforated corrugated tube.
The non perforated ones are better at avoiding radiation.

Other than the energy savings I would be interested in the efficiency of a smooth pipe climate battery. I could imagine it to be 30-50% less efficient compared to the corrugated tubes because of the laminar flow and the heavily decreased surface area.

I'm thinking of something like this...

https://www.klimaworld.com/pelletkessel-atmos-p25-24-kw-inkl-a25-schnecke-silo-bafa-forderfahig.html?gclid=CjwKCAiAkan9BRAqEiwAP9X6UXt3VaGbw_jHZVPO4xSL4cnLdWW9zoHHQLfoWRGVeUfZ1WJ5DUo3ChoCufMQAvD_BwE

Still looking at all the options for producing and distributing the electricity.

I'm looking into buying a house in France. Since it will be a watermill, I might have too high of a water table to put a climate battery under the greenhouse.
The greenhouse will have lighting, but they're LEDs, so they produce less heat and while France is sunny and shouldn't be an issue in the daytime most of the time, the night will be a problem.
I will not be using lights at night.

Maybe the water heating pellet stove and fin radiators might solve the problem. The Germans like to use what they call BHKW Blockheizkraftwerk, which in English are called Cogenerators, I believe. But those are around €30k. I can see it as an option in the future...

Skandi Rogers wrote:Wow that took me a while to find, you've made a mistake on the German site, you used the 0.58 U-Value figure which is in imperial you need to convert that to metric the formula works for both metric and imperial but you cannot mix them. the 19kWh figure is correct.


Edit this post has been massacred by the "you cannot use abbreviation" software very hard to write formulas without them
for the bold imperial read British thermal unit per hour foot squared F and for the bold metric read Watts per meter squared Kelvin

Thanks for taking the time!!! I really was hoping for the German result to be right... That would have been much cheaper to heat.

Hi,

I'm totally new at this, so please excuse this maybe stupid question.
While learning about sizing a heater for a greenhouse I encountered some issues:

I first found this site http://www.littlegreenhouse.com/heat-calc.shtml, so I used their calculator using imperial measurements, although I'm European and more used to metric.

The formula states BTU=A*DeltaT*U-Value which weirdly is the same to W=A*DeltaT*U-Value I got from a German site. Anyhow my greenhouse has a total exposed surface area of 2887 sq.ft/ 268.2m2 My lowest are 25°F/-4°C and I would like to keep it around 65°F/18°C the twin wall pc has a U-value of .58.
The result on the littlegreenhouse site was 66978 BTU which I then converted to 19.63 kWh. Going at it with the formula I found on a German website calculating in metric it comes to 3.42kW.

Where is the problem?