October 16, 2022

Greenhouse: Planning

A greenhouse is something we've talked about from time to time, but as with so many potential projects, we couldn't settle on the details. Location was the biggest question because so much of our property is shaded with big trees. When Dan took down the pecan tree that shaded that side of the house, the front corner of the house was opened up to a good eight hours of sun. After observing it for the past year or so, it seemed like a good spot for a greenhouse.

The plan is to build a lean-to structure off of the sun room

We had this in mind when Dan finished the siding on that exterior wall. For every other side of the house, we upgraded all of the windows. This time, we were thinking that if we added a greenhouse, we wouldn't necessarily need to replace those windows (a costly endeavor). The greenhouse itself would add good insulation, plus hopefully benefit from the heat of the house.

The first step was to dig out those bushes to analyze the slope of the ground.

The ground is relatively level, with a gentle slope away from the house. The lowest spot is by the fence. So some leveling is in order. One option for that is pouring a concrete slab, but it's a greenhouse, so a dirt or gravel floor is the more economical option. 

Then we discussed size. The length and height are set by those five windows. The idea we settled on is to replace one of the windows with a door, to be able to enter the greenhouse from the house. An exit from the greenhouse to outdoors will be in the back, where the fence is now. A solar battery box is behind the fence next to the chimney, so that's a factor for where we can put a door. That also sets a greenhouse width of about eight feet.

For greenhouse walls, we've saved all of the original house windows we've replaced over the years. 

Old windows from living room, dining room, studio, and bedrooms.

Old windows from kitchen, bathroom, and pantry.

The casings on most of them are shot, but Dan can mill out whatever lumber he needs. What we'll have to buy is a roof. Also, we'll have to buy the doors and a fan for summer ventilation; something solar powered like our attic fan.

While Dan works on building plans, I've been looking at greenhouse ideas online and working on a list for the interior. So far I have:

  • potting bench
  • storage for potting tools and supplies
  • bin for potting soil
  • bin for mulch
  • worm bin for vermiculture
  • shelves for starter trays and pots
  • pot hangers
  • rain catchment tank for water and thermal mass
  • what am I forgetting?

The catchment tank brings up the possibility of at least some passive heating of the greenhouse, because water retains heat and acts as a thermal mass. Other non-electric heating ideas include rock or brick surfaces (also for thermal mass), or a rocket stove, heat sinks, compost, resident rabbits or chickens, and hot beds. One good thing is that our winters are relatively mild. On the flip side, our summers are very hot, which means a greenhouse would likely be too hot for plants in summer (and that brings up another concern, i.e. the probable transfer of that captured summer heat to the house.) 

Obviously, we still have lots to research and think about. But it looks like this project will definitely be happening this winter! And I'm happy about that. 

Do you have a greenhouse? I'd be very interested to hear your experience, especially what you grow, and how it impacts your growing season. What are it's benefits and it's limitations? What have you experimented with? What's worked and what hasn't? What would you do differently if you were to build another one?

Dan's not one to sit around after a decision has been made, so I'll have first steps to show you soon.


Judy said...

Summer heat - have you looked into shade cloth like they use in the South-West? I'm sure it is pricey but you can be up against the windows and don't feel much heat gain. You can even get them as retractable screens so you pull them down in the summer and roll them back up in the fall.

Leigh said...

Judy, shade cloth is definitely something to consider. At least for the walls. Maybe I could make curtains with it. The roof will be the biggest challenge, since a greenhouse roof is usually glass (or plexiglass) to let maximum sun in).

Rosalea said...

Really looking forward to seeing this come to fruition!

Leigh said...

Rosalea, me too! :p

daisy g said...

How exciting! What a great way to recycle all of those fabulous windows! So smart!

Looking forward to watching the progress.

Leigh said...

Thanks Daisy!

Jenn Jilks said...

What a project! Good luck with that!

Leigh said...

Thanks Jenn!

Nina said...

We have a greenhouse which was here when we bought the place. It's quite difficult to keep above freezing in the spring, although I managed one year with massive amounts of buckets of water. Usually I've been bringing plants in at night and setting them out in the morning. Although there is no hydro (electrical) hookup any longer, there is a remaining old fixture for a couple of light bulbs, which, when you could get incandescent bulbs, would have produced enough heat to warm that immediate area. A friend though has had success with several 45 gallon drums of water, plus a brick floor to use as a heat sink.

We have a gravel floor and even with just the plants, the humidity in the spring is quite high. I'm happy enough with it in the back garden because of that. Make sure you have some variable venting higher up in the greenhouse to help with that and for air flow to keep those plants healthy.

Toirdhealbheach Beucail said...

Leigh - For reference, I do not have a greenhouse. Just thinking about your proposal and its location, I wonder about:

1) Water/Sink (if convenient an existing line)
2) More shelves (this seems to always come up with any building: "I wish I had more storage space")
3) Power (again, if a plug line is conveniently place)
4) The potential for heat is there. I wonder if in the process of building you could "overbuild" the insulation if you are added a wall adjacent to the house?

Leigh said...

Nina, excellent feedback. I'm encouraged by your friend's experience with the drums of water. Right now, we're planning on three 55-gallon drums, so maybe that will do it(?) It will be a huge experiment the first winter we're up and running.

And what you say about the incandescent bulbs is so very true. We once had a next door neighbor who had a large wooden box for his tomato seedlings. The only heat source was one incandescent bulb. Now, those appear to be extinct.

TB, thank you! Good ideas.

Several sources agree with you about insulation. I'm puzzled about how to do this, because the walls and roof will be glass. Curtains at night, maybe? Or insulated shutters? I suspect I'll lose a few things before I figure it all out.

Anonymous said...

Goatldi here. This is exciting I’m really making notes in that window bit is just sideways from being brilliant!

Unfortunately I don’t have any old stored windows because the original windows to this house with the exception of two still being used. Apparently when the previous owner replaced the one in the dining area and the one in the master bathroom so to speak even though it isn’t an actual en suite I have no idea what happened to.

I will however go scrounging through my old photos and send you a private message with the pictures and some explanation to how that worked out for me.
which is if you remember correctly entirely different than what you’re doing but it worked really well.

There are two remaining things on my list one is a greenhouse and I have my own thoughts about what I’m doing I’ll share with you at some point. The Spinners flock. Both are works in progress for next year.

Leigh said...

Goatldi, all pictures and ideas welcome! Greenhouses are challenging, I think. The roof is a big question mark for us right now. Glass seems out and the translucent roofing panels are flimsy. I've been trying to research options, but search engines veer off into all kinds of non-related topics, making it harder to find relevant information.

I love the idea of a spinners flock! I follow a youtube channel of a gal who has one and makes all kinds of interesting videos - https://www.youtube.com/c/CrowingHen.

I once thought I'd have sheep, but ended up with goats!

Ed said...

I've always wanted a greenhouse attached to my house or some sort of solarium anyway. But it has never been in the cards for me. Perhaps someday.

Only two things come to mind that you really didn't mention. One is humidity. Greenhouses as you know, produce an unbelievable amount of humidity which might be pretty tough on the wood siding of your house and also you with the windows open between you and your hourse. In my small greenhouse, we have water running down the ceiling panels nearly everyday from the condensation. But I used treated wood as a sill plate and much of the other wood can be replace over time as it rots out. My parents rebuilt their greenhouse three times that I can remember because the humidity rotted it out with time.

Water is another thing to mention. I know my wife's fondest desire is to have a working sink in our greenhouse. I'm not yet convinced though because with four definite seasons, I just can't plumb water to it. Any plumbing we could install would have to be seasonal and easily drained. You don't have any of those problems though. Right now, I have a 30 gallon barrel inside the greenhouse to store water and act as a heat sink. It works pretty well but the easiest way to fill it up is to carry it by bucket from a spigot on the house 80 feet away. I'm hoping perhaps next year to install some gutters and rain catching barrels to help supplement the hand carrying of water. Ideally, it would be nice to just have a frost free hydrant nearby but I don't think that is in the cards for me either.

We use our greenhouse to mostly extend spring and that was the original design intent. However, my MIL has taken a great liking to it and uses it all summer and fall to resuscitate orchids from our church that would otherwise end up in the dumpster. Not sure how they will do this winter inside our house with way too low of humidity. We've also been starting some trees from seed in the greenhouse as well since it is protected from the rabbits, deer and other animals.

Pioneer Woman at Heart said...

We have been talking about building one for years now, but we have so many projects. I do have windows saved though.

Anonymous said...

Well I’ll be honest if the goats hadn’t gotten here first there probably wouldn’t be goats now would be a jersey cow and sheep. I love my goats to bits and I always wanted to do my own dairy and we started small right and we just never moved past that. Thanks for the link I’ll look her up for sure. You might want to do a search on dome hot houses.I’ll see if I can find it I used to be on a dome hot house site really cool stuff.
And again not quite what you’re looking for probably as far as the type but I have sure learned a lot on that site and it’s on my Facebook .I’ll take a look cause I haven’t been on there for ages.

Dropped below was 50 today we can have freezes in October .I think the first earliest one is October 16 obviously that’s done but we still have about 10 days left to smash it.

PlantLady said...

Before you go any further, study Eliot Coleman's "Winter Harvest Handbook"...you will not find better info anywhere on growing under cover, whether heated or unheated. Absolutely the best reference on what to do, how to do it...and why. Anything else you can find by him or his wife (Gail Damerow "Garden Primer") will definitely benefit your growing.
And a wonderful idea I saw decades ago in a Mother Earth News was to make your walkways in the greenhouse from simple, hinged cover wooden boxes, set at ground level. Some can be worm bins, some can be compost bins, some can be soil compononet storage.
I have a multi-use "Transformer" greenhouse, simply made from cattle panels. In spring its covered with plastic as an unheated greenhouse. As it warms, the plastic comes off and shadecloth put on, for hardening off plants, starting more seedlings and as a shady area for buidling bouquets, etc. As harvest season nears, the shadecloth is replaced with a tarp to become a processing/drying/curing shed. When that work is done, its used for garden storage over winter...pots, flats, soil components, wheel hoes, etc.
So useful, and best of all? Less than $200...before recent price hikes.

Leigh said...

Ed, humidity is definitely a consideration. What kind of ventilation did your folks use in their greenhouse? I'm curious.

Thank you for the insight! Sounds like yours is still a work in progress, which I suspect ours will be as well. So much of it needs to be based on experience.

Kristina, that's how it's been for us too! So many projects. But eventually we got to it, and you will too. :)

Leigh said...

Goatldi, well, you can't beat goats for milk for a small family!

We're looking at our first freeze warnings for tomorrow and the next day. I'm not ready for it! After I'm done here, I need to go finish harvesting the sweet potatoes.

PlantLady, I have that book! It's been awhile since I read it, but I recall it had lots of good ideas. It's timely to get it out again and re-read it.

I love how you put your greenhouse to so many functions. That's great!

Alissa said...

I have a small 8x10 standalone greenhouse built from a kit from harbor freight. The walls are twinwall polycarbonate. Two roof vents, one door. Over several seasons I'm getting the hang of when to open the vents and door and close them for best airflow and to keep temps steady, but early in spring I still need supplemental heat (I use an electric oil-filled radiator powered by an extension cord run from the house) to keep it above freezing on the coldest nights...I can usually keep it about 20-25 degrees above the outdoor temps. I use the greenhouse for seed starting in the spring.

I've also found that it's WAY too hot inside for any sort of growing, even with all the vents and doors open and a fan blowing, once the outside temps reach the 70's and above consistently. It's also too warm for my worm bins--I learned this the hard way.

PioneerPreppy said...

No don't have a green house although I do have a building I been using like one but it would need a bit more glass to count. Problem I have is there is no where to build one that would not be constantly exposed to wind although like you I almost put an attached one on the South side of the house until I decided the house was too old to gamble on. Wish I had one though.

Leigh said...

Alissa, interesting, thank you for that. That's especially good to know about the worm bins. I'm already assuming it will be too hot in summer to grow anything. The electric radiator is a good idea. We use one in the bathroom when it's really, really cold. The other option for us might be a small mass rocket heater.

PP, placement is tricky, not only for sun, but I think for temperature regulation. I suspect our first year will be one of much experimentation.

Malatrope said...

Like Alissa, we have a small twinwall polycarbonate kit greenhouse. I put an electric car radiator fan powered by a solar panel in it to keep it cool during the hottest days (100F here). I found that to be inadequate on many days, so I added a cooling mister ring to the fan (making it a swamp cooler). This keeps the temps down in the 80s when it's in the upper 90s outside, just for the cost of a small amount of water.

Leigh said...

Malatrope, what a great idea! We're planning to install a vent fan, but the mister would be a fantastic addition. Definitely something to look into.

Malatrope said...

Leigh, be aware that we have really low humidity in the summer when those temperatures are high (20% or less) so swamp cooling might not work as well for you there. But the cost of a mister ring with five jets is on the order of $20, so it might be worth the experiment. It does tend to keep all your plants drenched, though! Mold might be an issue for you.

Retired Knitter said...

How exciting. A new building project - and a green house to enjoy all year round. I am looking forward to the pictures.

Mary, Windy Meadows Farm said...

I'm completely jealous...I've dreamed of a greenhouse made from windows for ages! Can't wait to see what you create...maybe a little more inspiration for me to see what I can come up with! I think at last count I only had 16 windows, but, even a small greenhouse would be a start! Mary

Leigh said...

Malatrope, yes, good point. We have variable humidity which leans toward high rather than low. Right now, we're collecting ideas! So I appreciate your taking the time to comment.

RT, nice to know others are interested!

Mary, this is a long time coming for us. And sometimes it seemed like it would never happen! I'm sure yours will materialize one of these days too. :)

Ed said...

Sorry for the delay. I got busy and forgot to come back here to see your comment until now. For ventilation, I installed four windows that can open on the corners of each side. We pretty much left then all open all summer long and have now shut them with the cooler temps. It isn't self regulating though but for our needs it worked okay.

My parents though used there greenhouse a bit more intensively and had a fan and a small electric heater hooked up to a thermometer installed. Both would kick on when appropriate. But theirs had access to power while we don't have power in our greenhouse besides the solar light I installed. I have thought that if we ever get to the point where some power would be nice, I can install some solar panels on the lawnmower storage side of the roof where the greenhouse roof isn't really necessary.

Ed said...

Well my previous comment to your question didn't take evidently. When I built the greenhouse, I installed double hung windows with screens in the corners and we open those up pretty much all summer long for ventilation. Perhaps if we get more serious about pushing the growing envelope, I might someday install a solar powered ventilation fan but for now, we mainly use our greenhouse to start plants in the spring and as a playground for my MIL during the summer. She likes to rehabilitate nearly dead orchids from our church and they like the heat and humidity.

Leigh said...

Ed, your comments went to moderation; something which blogger often fails to let me know about! I remember when you installed those windows. It's nice that your greenhouse is meeting your needs. I'm guessing the possibility of expansion is something we all think about. Thanks for coming back to answer my questions!

Anonymous said...

Check out the blog Frank and Fern. They built a greenhouse onto there house.

Leigh said...

Anonymous, Frank and Fern! I miss them. I'm familiar with their greenhouse project, but will have to have another look.