Food Making a 3-season room warm enough for greens

[WisconsinGardener]

I don’t know if this is the right spot for this. Let me know if there is a better forum area to pose this question.

I have a 3-season room that is unheated, no AC, nothing except those vinyl (not glass) windows. Had I known ahead of time how it gets really hot in the summer and really cold in the winter, I would have done some things differently. Now, I’m trying to find ways to make it at least warmer in the winter, preferably passively.

The first winter, I put window plastic up on the inside, you know, that 3M stuff that you use a hairdryer to make taut. Turned out to be a huge mistake. I don’t really understand the physics of what happened with it, but it iced over and then when it did get above freezing in there, it all melted and pooled water on the floor. I wound up pulling it all down after a couple of weeks.

I have photos, but they are too large, and my tech abilities are pretty nil for making them small enough. I tried putting them on Facebook and then copying them over, but that didn’t work, either.

Anyway, my current idea is to make wooden frames with 2x2 boards (is there such a thing?) the size of the windows and stretch clear plastic over them - then attach them on the outside instead of the inside. That would make an air space, and maybe being outside, it wouldn’t make the windows just frost over???

My goal is a place warm enough to grow winter greens. Right now, it is 33 degrees outside and 36 degrees inside the room. As it gets colder outside, the difference gets greater, maybe because it steals heat from the house. If it’s -20 outside, I think the coldest it ever got inside was just below zero, but that’s still too cold for greens. I would also just like to use the room more myself in the winter. It’s really more of a two-season room. In the summer, it gets very hot, and maybe I can be out there in the evening if I have the fan going full blast. Lots of things I would have done differently when I had this built had I been smarter.

 

[Toosh]

Two years ago I did a similar project. What will work for you will depend on several factors:

1. What is the roof of the area (metal flashing, greenhouse vinyl or insulated)?
2. What is the foundation of the area? (concrete slab, etc) and the floor (tile, vinyl, etc)?
3. How tall are the ceilings and what is the square foot? (else, what is the cubic foot?)
4. Are walls insulated?
5. Is your room southern-facing?
6. What is your budget?
7. What differential do you need? (Assuming winter greens requires about 55-degrees for growth and based on your average outside winter temp, how many degrees do we need to raise the room to get to 55?)

But real quick, I would not recommend wood frames of stretched plastic. Just as your experience with plastic wrap, I found it created condensation.

Instead of frames with plastic, consider bubble wrap on the inside. Go for the large bubbles if you can find it but small bubbles will work OK. (Moving department at Lowes - Home Depot did not have large bubbles) Cut to size, use a spraybottle to spray a thin layer of water and the bubble wrap will stick. It will stay there until you take it down. It's reusable if you take it down. The bubbles create more surface area for sun reflection so the room will be brighter and the air inside the bubbles create the insulation. Works great. Does not create condensation. It will also change the acoustics which is lovely if traffic noise and barking dogs are a problem. Highly recommend. A great value for my money/time spent. There are YouTube videos.

I suspect that like me, you'll need several layers of insulation.

In addition to bubble wrap, on Amazon, you can purchase grow tents. I have those shelf units on wheels. I DIY-ed a greenhouse around my shelf-units using 3/4" PVC, 4mm clear plastic and a large doorway zipper from Home Depot (in paint department). This creates a room within a room and gets warm enough to grow tomatoes, carrots, radishes and cucumbers. I need a small fan to circulate the air inside the greenhouse. I will one day upgrade to a real grow tent. I recommend a room in a room for controlling a more consistent temperature.

I laid terra-cotta tiles on the floor - they absorb heat. The back of my room is the brick of my house so I put the grow shelves along that wall for additional radiant heat near the plants. Heat rises and I found the plants on upper shelves did better than those on lower shelves. I added many hanging baskets. Not sure I would do this floor if I were to do it again.

I still needed a source of heat. The first year, I made a soda-can heater (YouTube videos). It worked well enough but last year I spent $700 at Home Depot for a ductless, mini split HVAC (heat + a/c). Installed it myself, it was easy. It's efficient and does a terrific job. Highly recommend if it's in your budget. If I had it to do over I would start with this. You won't regret it. Even with it, I still use my greenhouse tent - it allows me to reduce the time the mini-split runs.

When I added fruiting vegetables, I found the winter sun did not provide enough light and had to add 4' shop lights of good lumins/kelvins. ($15 at Mennards) They link together and are on a timer to turn on and off automatically.

Lastly, I made heavy, insulated drapes of washable, outdoor fabric and close them at night to add another barrier. The drapes are on rings that slide easily on a rod. I covered all 3 walls - this makes a big difference when it's windy. If you have access to a seamstress, this is a good value for the money spent.

Then, once the room was functioning, I found that hydroponics was far, far more productive and easier for indoor growing than in-dirt. I use the Kratky method. No pumps needed. No worries about a watering schedule. YouTube it. Only money spent was for the nutrients. I used recycled plastics.

This is also my seed starting area for spring planting. This year I transplanted my peppers and indeterminate cherry tomatoes from the garden to my room and they are still productive. I also added two dwarf orange trees. They smell heavenly. Once you have a functioning space you'll find many good uses for it. A worthwhile project, IMHO.

 

[Bps1691]

Consider making an indoor cold frame hoop frame. Make sure it’s in the sun through the day and use a small electric heater blowing into the hoop row during cold evenings.

Use plastic sheeting on the outside and inside leaving an air gap between. Attach the plastic to the frame and rails. Make it/them the size you need. You can make more than one.

Spinach, lettuce, collards and green onions do ok.

You can use plastic pipe for the hoops and a 2x4 for the rails. Drill holes in the 2x4’s to fit the pipe. Use plastic trays or tubs with soil to grow plants.

We used to cover ours up in the sun room at night with a wool blanket we got a harbor freight.

 

[packyderms_wife]

Check out the green house threads in the gardening forum here. On my phone otherwise I’d post links.

 

[Illini Warrior]

I'd be checking on the ceiling, floor and wall insulation before worrying about the windows - those 3 season add-on additions can get damn skimpy on insulating ....

I'd go ahead with adding window covering on the outside - but make it more durable for years & years of use without any real maintenance >>> use translucent poly panels to cover several windows or a llong sheet to cover a complete section of windows ....

you increase the window insulation factor by filling the void between the window and outside cover with bubble wrap or dropping in styrofoam peanuts ....

I'd be planning on adding some heat - seriously doubt you can passively keep the temperature up at night >> look at tapping into your heating system for the house and doing an extension into the 3 season - if not run piped in gas or heavy electric for a room heater .....

 

[WisconsinGardener]

Thank you for all the advice! The roof is well insulated with two layers of fiberglass insulation. The floor has 12 inches of expanding foam insulation under it. The back wall, which is my house, is well insulated. The other walls have no insulation in the window parts, because the whole thing is window. There is a small area above the windows that is solid wall, and that has fiberglass insulation. The corners are 6” squares, but not solid, and they are filled with insulation. The windows are just the vinyl film, though. Well, I guess in the long run and immediate future, I’m better off finding places to grow greens in the house.

 

[mecoastie]

Look up Eliot Coleman and how he grows green thru the winter in a hoophouse. He basically makes a greenhouse with in a greenhouse and grows specific cold hardy greens.

 

[momma_soapmaker]

I cut styrofoam board for the windows on my "storage" building (comes in big panels with foil on one side). Just pushed them into place and it holds. No light gets through however. Helps tremendously with insulation.

 

[Illini Warrior]

Thank you for all the advice! The roof is well insulated with two layers of fiberglass insulation. The floor has 12 inches of expanding foam insulation under it. The back wall, which is my house, is well insulated. The other walls have no insulation in the window parts, because the whole thing is window. There is a small area above the windows that is solid wall, and that has fiberglass insulation. The corners are 6” squares, but not solid, and they are filled with insulation. The windows are just the vinyl film, though. Well, I guess in the long run and immediate future, I’m better off finding places to grow greens in the house.

knowing well the Upper Midwest winters - don't see that add-on working well enough for a greenhouse without a regular heating source >>> addition sounds solid for adding heat for occasional wintertime use - I'd work on those windows for just that purpose .....

 

[summerthyme]

Look up Eliot Coleman and how he grows green thru the winter in a hoophouse. He basically makes a greenhouse with in a greenhouse and grows specific cold hardy greens.

Yes, except even he doesn't try to actually GROW anything in the 3 coldest months... he harvests very cold tolerant plants he grew in the late fall, then starts planting again in early spring.

Summerthyme

 

[Southside]

I have to agree with the split air. If you use the house heat, it will only run when heating the house. the 3 season room would surely not get enough heat, and the system would not turn on often enough to keep it warm.