The greenhouse I'm building will have framed & insulated north,east and west walls plus most of the roof. The only glazing will be the south wall at a 65º angle. I'm also insulating the ground with foam board to below the frost line.

This form of construction is typical of solar greenhouse construction and yes, it is a good idea.

solid north wall is a good idea if you want to maximize your heat absorbtion. Its a good idea if you are in a cold climate like you get in the north. The darker the better, and the more mass the better to help normalize (regulate) the temps from day to night and day again. Good luck.

Hmmm, and I specifically chose foil-faced foam insulation to reflect light back into the greenhouse. Did I choose wrong? Anyone have any comparative data on this?

Maybe I should get another little GH and test this out. :-)

Diane

It just depends on what your north wall is made of.

An ideal north wall for a solar greenhouse should be, going from the inside out.

Brick/poured concrete/concrete blocks with the spaces filled with concrete or ideally a trombe wall then, a layer of insulation, your framing, then the outside covering.

However, if your brick/concrete/concrete block part is greater than 4 inches deep then you are wasting money. Thermal conductivity comes into play. Any useful heat you retain in the mass past the 4 inch mark during the day is slow to work its way back into the wall and at night it also is slow being released.

My North wall is solid and one day it will be insulated. It is painted white on the inside because I need the reflected light in spring. However it was cheaper to cover and it has an higher R value than twinwall.

Here is a link that might be useful: {{gwi:309365}}

Wow, Chris..that's a nice big greenhouse!

Susan

I put a layer of 1 inch foil on both sides polyurthane fom on the north wall and north 1/3 ceiling of my HF greenhouse. I used foil tape to join the sections and painted the edges with white paint. I thought that leaving the foil exposed would be great for the reflected light but what it did was turn my greenhouse into a great reflector oven. The plastic bedding plant trays melted. After I painted over the foil with white paint it worked much better. I put additional captive bolts in during construction and then put 1 inch spacers on the bolts a large washer then my shelves another washer and a nut to attach the foam and shelves to the greenhouse.

Hi clw1, welcome to the forum. There are many here who have HFGHs and I'm sure that they would appreciate some pictures of your modifications if you can post them. SB

Chris, if you insulate with rockwool you could grow epiphytes in the wool too :) This will reduce the R-value of the rockwool a little, but I think it will be fairly self regulating - if a plant's root grow too close to the outside then they will be burnt off by the cold.

Rockwool is quite cheap. (sissilation - foil backed paper - is even cheaper)