greenhouse north wall insulation

[brian]

Today I insulated the north wall of my greenhouse using some double-thick bubble-foil. This product is similar to Reflectix which is rightly ridiculed because of its deceptive advertising. However, this is double-wall and twice as thick so it offers a bit of R-value itself, plus I actually created an air gap of a few inches between the insulation and the exterior polycarbonate which should provide advertised "installed" R-values.

Even more importantly to me, this foil is bright white on one side - perfect for reflecting light inside greenhouse, and silver on the outside which makes it not stand out too much visibly.

I'm thinking of painting the inside of the shutters white also. Not sure if paint will stick well to raw aluminum in a humid environment, even with a primer coat.

I am a bit worried that moisture & algae will accumulate in the gap. I cleaned the inside of the polycarbonate and dried it as much as possible as there was already some algae growing. We'll see.

[millet]

Insulating the north wall is a wise decision.  I insulated  my greenhouse north wall with 3/4 inch silver sided polyurethane insulation (PUI) board.  I then painted the silver siding white, because white reflects light better than silver surfaces.   I also cut PUI to fit snuggly into the inset of the shutters. and insert them every night.   I also put insulation inserts up on the south wall at night and remove in the morning.  

[brian]

I'm really happy with the way it came out. I care most about keeping high light levels in winter and the white floor and wall seem to make a big difference.

With so many plants inside my greenhouse in winter, I do not have easy access to the walls to move insulation twice daily. I keep thinking of some way to roll a sheet of insulation over the whole roof overnight, but my heating costs are so low I just can't justify something so extreme.

I am thinking I will put a piece of polycarbonate panel or insulation board on a hinge hanging over the inside of the shutter vent, so that gravity holds them over the vents... unless the exhaust fans activate on a very sunny winter day the vacuum should pull the board out so air can come in. Even tightly closed the shutters leak quite a bit of air.

[zap]

In the past I painted some interior surfaces fluorescent Blue, or fluorescent pink. ( I could not find fl.red ) with the idea being; some of the UV and other reflected light would be converted into wavelengths useful for Photosynthesis.

And glazing on the north wall just bleeds energy away, on clear days. (sorry Aussies I got that re-worsed)
?Maybe some light might enter through the north, on cloudy days? -But is it worth losing Infra-red heat out the north glazing at nights? I suppose you just have to balance the two - or use a rollup system?

Very clean looking structure Brian!

[kumin]

Looks well constructed, with lots of headroom. Was this a DIY project?

[brian]

It was a kit, Conley Hobby House steel frame. I did the foundation, assembly, heating/wiring myself along with my brother and friends for the big stuff.

Im really happy with it, highly recommend Conley’s frames

[brian]

I added lights today, and painted the inside of the shutters white.

[kelley]

Beautiful greenhouse, Brian! What are the dimensions? 40’L by ?

[brian]

Thanks. Its 18x36 ft. I was originally going to do 42ft long but once over a certain size it becomes subject to more extensive building code & inspections. The kit allows it to be as long or short as you want simply by adding segments like a centipede

[brian]

My gas bill just came, and it shows that I used 11% less gas this November compared to November last year, with the same average temperature. That's a pretty significant improvement from sealing air gaps and adding the north wall insulation. Even better, the already laughably cheap natural gas rate is going *down* 15% because world commodity prices for natural gas are tanking.

Piped natural gas is fantastic. I used to pay $400+/mo for heating oil just to heat my old house. Now I'm paying half that to heat a larger house and a (relatively) poorly insulated greenhouse.

[citrange]

A couple of years ago I used reflective foil-covered bubble sheet to insulate the lower third of my polytunnel.
It has by now completely disintegrated, presumably due to the action of sunlight.
I cannot complain as it was sold to provide added insulation to the inside of house roofs, and was not claiming any uv stabilisation.
I hope your lining is better quality in this respect!

[brian]

My greenhouse covering is polycarbonate panels which are supposed to filter 100% of UV light, so I expect the foil will be okay. We will see!

[poncirusguy]

Use of house south wall to insulate north wall of greenhouse


Use of leaf filled bags to insulate greenhouse north wall and other walls where the sun doesn't shine

[brian]

Leaf filled bags is a great idea for free insulation, good thinking.

My worry about condensation & mold/algae forming in the gap between the bubble insulation and the polycarbonate turned out to be a non-issue. Even though it is always humid in the greenhouse I haven’t seen any moisture in the air gap