Elsewhere there are threads on Thermal Mass. Someone posted something like, "If you have a heater running at night and you have vents open and fans running during the day for cooling then you have the potential for some creative ways of saving energy."

Are you doing anything (heat sinks) to capture this daytime heat?

Heat Sinks

Thermal Mass

Nell

This is the 1st week we have used the greenhouse. My husband put in 3 black barrels full off water today to save the heat for the night.

I love the idea of free heat. However, I don't like my seedling temp reaching soil temps past 75. So my question is do I need to take down the blankets? I'm thinking they are the main reason for the heat surge. How can I use the blankets to my advantage without getting it to hot? Do I need to adjust the fans,vents,ect?

I will check out those links though. I definately want to save the heat. It would be nice to save all the propane I can:)
Thanks!

I am psychic,

I have a feeling you have snow on the ground there.....

If you have then trust me things will get better.

If by a slight chance you don't, then you still have a solution to your problem.

Don't remove your reflective insulation. You need it at night. What you built was a solar oven. The cheapest way (and I am cheap) is to hang white old bed sheets up against the north wall. (or any light color) Someone on here painted their reflective silver insulation white and it helped a lot.

The reason for the snow comment is that when there is snow on the ground you get a lot more heat energy in your greenhouse. My best temp was 140F, damn snow!

Leave the insulation on but stop the sun shining on it.

Oh and add more water...

:)

Hiddengarden,

What kind of plants are you trying to grow? The reason I ask is that you mention not wanting temps of 75 for your seedlings. Most seedlings I know of are very happy with that kind of soil temperature!

MollyD

Bells are ringing! Yes! Your right it's the snow. Why didn't I think of that. Okay I told my husband about painting the silver. He thinks I'm nuts. What will it do-burn up my plants leaves I imagine? Create to much light? Am I on the right track here? How can I explain this to him.

Also, I can get the temp down some but not the humidity. I have two large fans on each end which I can adjust thier movement,a large vent with an exhaust that opens it on the other side. But I don't have a roof vent. Could that be my problem? Also I don't have any ground level vents. I just thought of a dehumidifer. I'm going to take that out soon and try it. Any advice on the best ways to adjust the humidity without lowering the heat to much? Oh and yes I had to water like crazy before everything dried up.

Molly D your right 75 is pretty optimal. I'm growing assorted perennials. I should have said 85. It was up to 89 at one point and climbing. Right now I have cool weather perennials like poppies and columbines. If I'm right they prefer 55-60 degrees. Won't it hurt them if the temp gets too hot? Or should that not matter? Is one worse than they other..such as too hot or too cold? I'm still learning here.
Thanks!

Columbines should be okay. I'm not sure about the poppies since I've always just sown those outside.
You should check out the forum on Propagation from Seed. There should be folks there with experience on what you want to grow. I grow daylilies and those seeds like 78 best for germination. The seedlings don't mind temps up to 100 though they prefer around 80 tops.

MollyD

Molly,
Thanks, that's some relife off my mind:) I won't worry about all my plants dying before they even sprout now. lol That is one of my nightmare I hope won't come true.

Also I was sitting in the greenhouse and It finally came to me about the humidity problem. Yesterday I had a problem w/heat to high and humidity too low. It came to me it was due to the fact the heaters(propane)were off. This morning the humidity was real high and it took me till 10:00am to get it lower. I figured that out too. It was due to the fact the heaters were running all night with the fans off.

I read about everything in books,however it didn't kick in untill I'm actually working out there!

Propane heaters should remove humidty. I know it does in my home at least. Sounds like you need a roof vent so you don't haft to work so hard. If you had a floor ven also the hot air would rise out the roof while 'sucking" in cool from the floor vent.

amazon: Are you suggesting running a propane heater whilst all the vents are open? Are you being deliberately malicious? Burning hydrocarbons increases humidity, and heating with all the vents open is like burning money.

I don't see that a roof vent will make much difference if you've already got some fans running. Is the humidity really a problem? What is your dewpoint and air temperature?

If it is getting too hot put some shade cloth on.

If u cover your greenhouse with Mylar do u have lights running all day to keep plants happy? I sure would love to have free heat that way but I need the light for my orchids. I have to make changes before next winter so am checking all possiblities.
Oh yea. I grow orchids for pleasure so that is why i need the light year around.

Amazon-Propane increases the humidity. At least it does here:) I have had propane in our home for 5 years now and always run the dehumidifer when it gets real humid.

Nathan Hurst- Well my gauge only shows it up to 80% then it just says max after that. That when I start to worry:) The air did get up to 100 at one point before we got it down. However, I think I got it all figured out now. If you see what I had posted above I belive that is what my main problem was. I'm just new at all this and just want to have it perfect from the start! However everyday I'm starting to figure something more out I didn't know before. It is exciting and sometimes frustrating. I'm enjoying taking notes like I'm some scientist. Like-if I move this fan so many degrees and open the vent so far.....

But I'm loving every minute of it too. It like my own little dream world:) I could live out there!

Puffysmom-I didn't cover the outside of my greenhouse with mylar. Just 2 inside walls where the light doesn't come in. I need the light too and can't afford to run lights. We are having a nice warm week here now. Feels like spring!
I don't know to much advice to give you since I'm new to this. However you might want to read the posts about heat sinks and such, if you haven't already. Good luck with your orchids they are one of my favorite flowers, however I don't have much luck growing them.
Thanks

80% sounds low. You're aiming for a VPD of about 1kPa. Personally I wouldn't worry about it unless things are actually rotting.

NathanHurst-What is a VPD of about 1kPa? I not very technical. I had read I need 50% humidity and the higher it goes from there is bad except for tropicals. So do I really not need to worry at all then?

The only gauge I have right now is one from lowes that tells the temp an humidity. Oh,and a soil thermo and ph meter. Do you think I really need a light meter or anything else? I'm trying to get by with what little I can:)

Thanks

hiddengarden, I would concentrate on just getting the temps down to about 80 or so during the day and not sweating about the humidity. I think if you have a fan and shutters running and set to a thermostat ( where the fan automatically comes on at a certain temp) you will be fine. Having the temps at 85 or 80 is not going to raise your soil temps to that temp-which is the air temp. Soil temps take longer to rise.
You didn't say how long your grhouse is or what size fan and shutters you have-I would be curious to know those things.
Even in the winter with cold temps outside-if the sun is out, then your grhouse is going to warm up! My fans start coming on around 10 am right now, and as the weather gets warmer, they will come on sooner and run longer during the day.
A lot of humidity is not a good thing in a grhouse unless you are growing certain plants like tropicals. Humidity can easily lead to a fungus. I grow for a living and I never measure the humidity-As long as the fans are running, I know that I am fine, and sometimes on a cloudy day, I will lower the thermostat to get rid of some of the humidity. You don't have to wash down the floors to create humidity-exchanging the air in your grhouse is more important.

Terryster-thank you for your post. I feel like an idiot for asking dumb questions. However you all have been so nice and helpful. I too am growing for a living so I guess that's why I have been nervous. My plants are looking really good right now. So I'm feeling pretty positive about it all.

I was worried about spreading fungus and growing disease. However the humidity has been low during the days now. My greenhouse is 16x36. My exhaust fan is about 48" and the same with the vent. It's a rainbow gutter connect greenhouse. I'm only using half of it for the greenhouse and the other 16x36 for a shade house. I have two good sized(not sure of size)fans mounted up high for circulating. We bought everything except the heaters used. So all the fans were less than 200 dollars.

I think I was too dumb not to realize how fast it would warm up in the winter. I guess because the first few days I was struggling to get the temps past 50. However,it was only 8 outside then. So when I didn't have to use the heaters I was like wow! lol

I have roses,clematis and several other perennials in large pots on benches. Then I have one long bench with my trials on starting seeds(hoping I can do fine,but ordered plants so I would know I have some to sell if not).

The other day my soil temp were 89 was when the temp rose over 100. Now I see what your saying,because when it's 80 inside the soil temps are about 50-60 now. I now have the exhaust hooked up to kick on with the thermostat. It has made a big difference.

Here is a question: when you exhaust are you pulling air in through the shutters into the greenhouse and then out through your vent or are you just opening up one vent and letting air leave through there?
I am asking this because I need to start shading/venting as the temp is warming up this spring however we still have temps around 20-30 and I am afraid of shocking my plants with cold air if I draw new air in through the shutters. I think I may try opening a vent only and letting air go out the vent but I wasn't sure how the plants would like this also. I have orchids right now and they are LOVING the greenhouse. Everyone of my phals has 2-3 spikes right now.
I never had that happen under my light stands!

-renee