Insulating the Greenhouse

DSC03994Last spring, I was sadly disappointed in my new hobby greenhouse’s ability to hold heat.  It’s shown above on the day construction was complete, bereft of benches, shelving, pots, and other clutter that later accumulated.  It warms up greatly on a sunny day, but on cloudy days and at night the difference between the outdoor temperature and the indoor temperature, even with a small portable electric heater running was only  1 degree!  One degree!  That’s pitiful!  And certainly not efficient enough to protect my precious seedlings.  Luckily, 2016 turned warm and stayed warm, so it wasn’t a problem.  Having the greenhouse was still a blessing, because it saved young plants from damaging winds and freak hail.  It also quickened growth on all the heat-lovers, so it’s worth having, but my plants need protection from COLD, and I really want to start utilizing the greenhouse space earlier in the season.  Researching methods to improve the situation was required.

After much on-line reading, horticultural bubble wrap insulation seemed to be an answer, so I ordered the 4 1/2′ wide rolls from ACF Greenhouses ( ).  I also ordered the plastic plugs that anchor the wrap to the metal framework.  The shipment arrived only two days after I place the order, which was amazing.  Excitedly, I carried the boxes to the greenhouse, and paused for a moment, wishing there wasn’t as much stuff already in there.  After moving a shelf, a wagon, a stack of pots, and the heater, I had access to the first wall, unrolled the wrap, lined it up, pushed in the first plastic plug and tried to get it in far enough to turn it to lock the wrap in place…and tried….and tried.  Finally, I abandoned the wrap, and just tried to put the plug into the empty metal track.  It wouldn’t fit!  Here’s the metal track the plugs are supposed to go into…

GH frame compressed  My metal framework is obviously thicker metal (it’s steel, not aluminum like most…we get 60 mph winds and heavy snow loads some years so I opted for strength) than the plugs were made for.  An attempt to fix the problem followed. Plugs compressed  Focus on the far left plug.  See how small the opening between the part that turns in the framework and the base is?   The top plug is one I filed slightly to make a larger opening.  Notice I did not weaken or reduce the post that holds the turn-in part. Filing a couple of the plastic plugs was not easy (I worked while I watched basketball so it was not a total waste of time!)  but it was do-able. However, I wasn’t looking forward to filing 100!  I bundled back up and went out to try again.  The plug would fit into the slot with the insulation, but when I turned it to lock it, the base snapped off the plug.  Obviously, this wasn’t a solution.  I tried everything I could think of including clothespins, bent wire paper clips, flat-headed bolts, wiggle wire, etc.  It must be something that is easy to install yet just as easy to remove.  After all, the insulation will only be in place until mid-May and then it comes down.  Plastic melts inside my greenhouse even with two roof vents and an automated fan vent.  Believe me, I learned that one last summer and won’t leave anything plastic in there again.  Finally, I remembered some metal clips in my husband’s desk and I “borrowed” them.  They come in assorted sizes.  The small 1/2″ ones fit in the track, but didn’t have enough strength and popped off.  Happily, the larger ones (1-1/4 “) also fit and for the most part Gh clips compressed   work  well!  (Happy dance here!)  They aren’t cheap ($4.79 for 15 at Staples and it took 9 pkg.) but I figure they will last the rest of my lifetime easily, and they are easy to use.   It still wasn’t easy though.  Climbing a ladder and holding the wrap over my head while trying to clip the clips wasn’t fun.  Neither was Gh bubble compressed  working the insulation around and behind my benching (which is WAY to heavy for me to move again… putting it in was hard enough and I’m a year older!)  but by crawling underneath and carefully pulling, climbing on top and carefully feeding it downward, I was finally able to get the wrap installed.  It would have been a lot easier if the greenhouse were empty, so I wouldn’t have to move everything a dozen times, but that will never be the case now or in the future, so it’s a just-do-it situation.  Once the wrap was all clipped up, I used inexpensive clear packing tape on the seams (overlapping the wrap a bit) to secure it and also around the vents.  (Another happy dance would have been appropriate, but I was too stiff by then to move!)  I did reset the thermometer, so I could compare the outdoor and indoor low temps.  GH bench March compressed  The next morning, I hurried to the greenhouse, eager to see how much difference the bubble insulation wrap had made.  Unfortunately, the sheets were hanging loose wherever there were seams.   See it sagging open just left above the potting bench? The packing tape had not held.  How can that be when anything that arrives wrapped in bubble wrap and fastened with tape is nearly impossible to open without a sharp blade?   Somewhat deflated, I ordered a roll of  4″greenhouse tape $15 (as suggested by ACF, but I was trying to save a few pennies, which were now spent on additional shipping costs of $16)  and re-taped all the seams.  I also ran a bead of silicone sealant on the outside, wherever there were little gaps between the greenhouse framework and the wood foundation, because when I was crawling around on the floor, I noticed cold air coming in here and there.  It was finally finished!

Gh insulation complete compressed  After 3 nights of temperatures in the teens, there is a 6 degree difference.  Still not great, but better than 1 degree WITH the heater.  Tonight it will be mid-twenties, so I’ll monitor the temperature with the heater running.  I’m hoping to see enough difference in heat retention to make it worth  A: the expense…$36.95 per 4.5 x 25′ roll, $55 shipping….it took 4 rolls for my 10 x 12′ house, plus the clips and tape,  and  B: the effort installing the wrap.  I’m already not looking forward to putting it back up for next season, but if it really, really helps I can grin and bear it.  Crossing my fingers that this works, because there are over 1,200 plants that need to come out of the basement… over twice that many more seedlings still to be transplanted, and winter seems to be hanging on stubbornly with bony fingers.

About carolee

A former professional herb and lavender grower, now just growing for joy in my new potager. When I'm not in the garden, I'm in the kitchen, writing, or traveling to great gardens.
This entry was posted in gardening, hobby greenhouses, Potager, Uncategorized and tagged , , , , . Bookmark the permalink.

11 Responses to Insulating the Greenhouse

  1. cavershamjj says:

    The bubble wrap will make a difference but greenhouses are leaky things, I fear you will mainly be heating the universe outside. Its also a bit of a pain, as youve discovered. As an alternative, you might consider a heated bench, even a simple arrangement with heat pads or a more fancy one with soil warming cables, that just heats the area under the pots/trays to stop them freezing. Then you’re only heating the bit that really needs it rather than the whole volume. It’s revolutionised my propagating this year. Good luck with the temperatures. We’re out of winter now, might get a light frost from time to time between now and end of April but it’s generally well above freezing at night.

    Liked by 1 person

    • Carolee says:

      I’ve thought about moving a heat mat or two to the greenhouse, and that may be another trial. I’ve had 6 different types/sizes of greenhouses over the years. I know the smaller the house, the wider and faster the temp fluctuations, and this is the smallest I’ve had. Thanks for the input.


  2. Patricia Quier says:

    Insulate the floor, cardboard covered with straw? or dig out like hot bed? Pat

    [image: Inline image 1]

    On Thu, Mar 16, 2017 at 8:10 AM, herbalblessingsblog wrote:

    > carolee posted: “Last spring, I was sadly disappointed in my new hobby > greenhouse’s ability to hold heat. It’s shown above on the day > construction was complete, bereft of benches, shelving, pots, and other > clutter that later accumulated. It warms up greatly on a sunny d” >


  3. Great looking greenhouse. I am jealous. I will be interested to hear what your final solution is.


  4. I envy your space and the ability to have a greenhouse. I will be planting containers only so I can move them around in my perennial gardens which are the only areas that get enough sun. Will have to watch the bunnies, squirrels and woodchucks though, very brazen.


    • carolee says:

      Those bunnies can be tricky. Last year, I placed a row of flats on a 3′ tall bench to begin to harden off, inside a fenced area with 18″ of chicken wire along the bottom. The first night 3 entire flats were eaten to the soil. I set up the Critter camera (a Christmas present from hubby) and moved all but 1 flat back into the greenhouse for protection. The camera showed a small rabbit who not only hopped over the 18″ fence, but jumped up on the bench and merrily munched an entire flat of parsley! The next day, I added another 30″ of chicken wire around the entire fence. So far, no bunnies have been back. Do have an occasional squirrel visit and move tulip bulbs around, plant walnuts, etc. but I can live with that. Best of luck!


  5. usillyrabbit says:

    Did the wrap end up being worth the cost and hassle? I have a portable poly tunnel and bought a solar pool cover to put over it. I live in a very mild climate, but hoping to grow tomatoes and peppers through winter with grow lights. The solar cover seems to not help at all. Have now put a later of plastic over that, and I’ve put reflective bubble wrap over door flaps and on north side in the tunnel to help reflect the grow lights and insulate. I swear at night it’s colder INSIDE than out!! Tonight it’s 46F and inside with a small heater it’s barely maintaining 50F. I am thinking of getting same wrap you used, but after reading your post, not sure it’s worth it.


    • carolee says:

      My bubble wrap is disintegrating now and I doubt I’ll replace it. My greenhouse is useful in spring to protect tender seedlings from the wind, light frosts, and hungry critters, but not as a place for winter growing. And, it’s a lovely place to spend a few hours reading on a sunny day in mid-winter, with my electric kettle and tin of teas!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s