I'm a new to using a greenhouse and put up our Palram 8 x 12 greenhouse early this year. So far so good. My goal is to grow some fresh greens over the winter. thinking about a couple of things.

The first is heating. I have a gravel floor and am considering setting up a above ground compost bin for heat. Can I keep it narrow 24-30" by 4-5 ft long by 24-30" high, and still get sufficient heat out of it? I used an electric heater this spring and could run my extension cord again, but would prefer to not see how much I can spend but may again if needed

Another idea under consideration is removing the north wall lower panels and putting them on the south wall or maybe in the inside of the roof to create a double pane situation. I was planning on putting insulation panels on the north side anyway so I would just need to add an exterior protection layer. I could use bubble wrap on the lower wall or plastic for a double layer.

Since we are in the Pacific NW and sunlight is also an issue does anyone run grow lights in their greenhouse? Is it worth it? If I did put in LED grow lights I don't think that would break the bank, but it needs to be worthwhile.

Anyone else making plans?

Real rough calculation here. Let's use $0.10 per kilowatt-hour, fairly typical in the U.S. That's ten cents to run a 1,000-watt device for one hour. Easier for our purposes to call it one cent per hundred watts per hour.

Typical use of LED grow lighting is around 40 watts per running foot. So 0.4 cents per foot per hour. If on for 16 hours a day, 1.84 cents per day per running foot. So a growing bench ten feet long of one row of containers costs about 18.4 cents a day. $5.52 for 30 days.

For example, I have two shelves in Kratky hydro, each shelf four feet wide, or eight feet total. Each shelf has two 100-watt LED F3 spectrum strips, making the rack 400 watts in all. So, four cents per hour, 25 cents a day, about $7.50 a month. I find that acceptable.

(Folks, feel free to check my math.)

There is, of course, the initial cost of the lamps. I was fortunate to get at no cost six Illumitex strips, 600 watts worth of professional LED that sold for around $2,400. I don't have enough knowledge to comment on the merits of cheap grow lights compared to these, but I have to think there is a genuine difference.

But from my casual impression about your sky cover a lot of the year, it sounds like lights would be worthwhile.

As to heat, I understand your winters aren't terribly hard, but what I have in mind may or may not be useful, depending on how well your greenhouse accumulates daytime heat in winter. Large water tanks can store a lot of heat during a warm day and release it at night. You paint the tanks black and put them under the growing benches. The tanks can even be the grow bench supports. The cheap 55 gallon drums often offered on Craigslist would work.

A masonry floor also helps. Concrete pavers, etc. About $1 to $1.50 per square foot plus sweat equity. And bubble wrap is also commonly recommended as winter insulation.

And I'm sure that on cold nights, the greenhouse loses a lot of heat by radiation through the usual inefficient and large clear cover. If it's not too much of a chore, perhaps. And if you have louvers, they're probably leaky and could use foam core or foil coated double bubble over the openings. And the usual things we do for homes, door weather strips, etc.

I figure every bit helps, and anything is better than the electric heater. Of course, it doesn't have to be toasty warm, just not so cold that it retards growth, and choice of varieties has something to do with that.

I'm not the best authority. I have pretty much the opposite problem. Summers at or over 100 for many weeks and hardly any winter most years, but a few below freezing nights to make it interesting. But ground heat retention and my high water table take care of keeping it from being a disaster.

And I almost forgot, it is recommended that if you depend on a masonry floor for part of the solution, it helps to insulate it from the ground. And it doesn't have to be the actual floor. Bricks or stones stacked on pallets can be a heat sink, as can brick surfaces on grow benches.

How do you insulate bricks from the ground?

Planning update -

Compost idea dropped - not enough benefit for amount of space. Might consider a hotbed.

I got a copy of "the Year-Round Solar Greenhouse" by Lindsey Schiller & Marc Plinke from the library. Lot of good information. well worth the time to read.

Insulation panels for north wall planned - 2 - 4 x 8 sheets Approx $40 -

Thinking strongly about using some thermal mass. Best would be 50 gallon water tanks, considering stacking up 5 gallon buckets painted black with lids or a home built frame with a pond liner. After reading the book, it might help moderate the temps in summer.

Looking at a secondary glazing layer using clear plastic sheet. Also considered using the shrink film window kits.

I also plan on reinforcing the roof to better handle snow load.

If you haven't looked, around here, there are many people offering used plastic 55 gallon barrels on Craigslist, usually the blue ones. But there are also lined metal. The going rate here is $20 to $25.

Bricks or stones can be insulated from the ground. Effective insulation is just dead air. So a rather thick bed of sand between garden cloth layers is a reasonable space. And it passed water, which is a useful thing. Commercial radiant barrier can be used, but it's usually not able to pass moisture, so odd water spillage is an issue.

For an impermeable floor, there are insulating concrete mixes, one simple one being vermiculite/concrete. It is claimed that, "Three inches of vermiculite concrete is equivalent to 1 1/2" of rigid board insulation layed over steel decks. One inch of vermiculite concrete is equal in insulating value to 20 inches of regular concrete."

If you want the look of brick, it can be laid over a vermiculite/concrete floor and get the insulating advantages of the underfloor.