Kristi Cook has been a voracious student of nature’s methods for growing healthy, organic food for nearly 20 years. When she’s not digging in the dirt, you’ll find her sharing her discoveries with anyone within hearing distance. You may contact her at

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Do It Yourself Cold Frames
by Kristi Cook       #How to   #Sustainability and Self-Sufficiency   #Winter

Due to drainage issues in this particular area, I chose to place this cold frame on top of a raised bed rather than flat on the ground. Once spring planting season arrived, the frame was lifted off and stored until the next winter.

Winter gardening is the busy gardener’s dream come true – bountiful harvests with little to no weeding, watering, or other tiresome work. However, you do need to provide a bit of protection for winter veggies. DIY cold frames can be both inexpensive and highly functional, and constructed using materials you may already have on hand.

How Cold Frames Work
Just like children, winter gardens need protection when the mercury plunges. However, the goal is not to create summer-like conditions. Instead, cold frames limit the freeze/thaw cycles by collecting solar heat, blocking chilling winds, and deflecting soaking rains. These traits tend to keep temps inside approximately 10-20 F above outside temps, depending on materials used.

Construction Basics
Cold frames are simple to build. The goal is to create a bottomless box no higher than 12-18 inches in back, no lower than 8 inches in front, and as deep/wide as you need. While there’s no hard and fast rule on height and length, try to keep it on the lower side to best retain heat. And while many construction plans recommend slanted tops to provide optimal solar heat acquisition, it is not entirely necessary as long as placement is in full sun. Use what’s on hand to keep costs down, such as scrap untreated lumber, bricks, masonry blocks, or hay bales, and don’t worry about slanting the top unless you want to do so.

To create the light (or lid) you need some type of translucent material to allow the sun’s rays to enter the box. Recycle old storm doors or windows, shower doors, salvaged greenhouse panels, Lexan, or other clear material to further increase savings. If none of these materials are available, use heavy-duty plastic sheeting. You can build a frame for the sheeting or simply drape it across the box and secure with blocks, water jugs, or other heavy items to prevent heat escaping.

While cold frames with solid lights and wooden sides are nice, straw bale frames work just as well. Place bales in a rectangle to the desired width, or leave the front open for easy access. If leaving the front open, be sure the light you choose touches the ground to hold heat in. Create a light out of heavy-duty plastic sheeting or an old transparent door. If using sheeting, drape across the entire bale to best facilitate heat retention. To keep the plastic in place, fill old jugs with water or sand and lay on top of the edges. Simply roll one side up to gain access to the goodies inside and replace when finished.

Site Selection
Choosing a site couldn’t be easier. Walk your garden and select the sunniest spot available. Check to ensure it’s not in a low place that collects rainwater, as cold winter rain pooling under the frame will end your winter garden. It is also beneficial to place the frame in an area with some protection from winter wind, such as near shrubs or other tall plantings, provided they do not block valuable sunlight. However, stacking hay bales or other large items along the windward side of the frame days can provide temporary wind protection in the event of especially cold and windy.

Additional Considerations
While you want to keep heat in, there will be times when you have to ventilate excess heat. Keep a thermometer in the center and monitor throughout the day until you it’s time to vent. In most cases, outside temperatures of 20 F and higher require venting for at least part of the day. At the cooler end, you may need to lift the light only a few inches. Warmer weather will call for wider openings.

However, you may also need to occasionally provide additional insulation. When temps drop into the single digits, add extra insulation by placing a heavy blanket or several inches of hay across the top and sides. Just be sure to remove during the day when temps rise to avoid overheating.

Constructing a cold frame with readily available materials provides inexpensive protection for the winter garden. And with a little creativity, you can build a frame that costs you nothing more than time.


Build Your Own!
By Michelle Byrne Walsh

Here are steps to build your own cold frame

1. Assemble materials. Our list included: one double-pane window, two large sheets plywood, two small door hinges, 1 inch pipe foam insulation, door and window insulation tape, stainless steel wood screws, wood glue (or other weather-resistant glue, we used Gorilla Glue) and exterior paint. The tools you will need are a saw, saw horses, drill, screwdriver, measuring tape, pencil and eye and ear protection for the power tools.

2. Decide the dimensions of the box. Because our window measured 29 by 33 inches, we made the box those dimensions. And because the window should slope southward to take advantage of the low angled sunlight, we made the front of the box 6 inches tall and the rear wall 18 inches tall.

3. Measure and trace the shape of your pieces on the plywood. Templates or patterns might be helpful. And do the math for the sloped sides! Because your window will rest on the top of all four walls, be sure the sloped sides are the same length of the window (the bottom of the side walls’ measurements will be different).

4. Cut the wood walls.

5. Glue and screw the walls together. We chose butt joints, but if you are a skilled woodworker and are using solid wood boards (versus plywood), other types of joints might be desirable.

6. Remove the window’s existing hardware, if needed. Attach the window to the frame using door hinges. Here we reused the existing hardware holes drilled into the window’s frame.

7. Paint the box. You can choose a color to match your house, as done here, but be sure to paint the interior of the box white for maximum light diffusion.

8. Attach pipe insulation to bottom of frame– this will protect the wood from the soil and help “seal” the frame to the ground. If needed, attach peel-and-stick door/window insulation to areas where window doesn’t seal tightly.

9. Fashion a sturdy prop stick. I used scrap wood and covered the top with left over insulation foam.


A version of this article appeared in a November/December 2017 print edition of State-by-State Gardening.
Photography courtesy of Kristi Cook and Michelle Walsh.


Posted: 11/28/17   RSS | Print


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