Upgrading the SubT

We have a 'daylight basement'.  I put quotes around that because I think saying it was a stretch on the builder's part.  What they did to create the 'daylight' part of the basement was extend the basement out a few feet, surround it by a brick wall and put stairs that lead below grade to a door and two windows.  

A few years back, I decided that this would be the perfect place to build a greenhouse.  The well is 6' across and the area from the end of the well to the side of the chimney is 9' long, so the greenhouse is 6' x 9'.   It's perfect because I didn't really have to build much.  I had to come up with a way to create a roof that was insulated and still let sun in.  The roof had to be slanted so it didn't collect leaves so that meant that there is a triangle at one end that had to be dealt with and the open end.  Because there is a chimney sticking out of the wall, the other end was half walled which just left a doorway.

So, in October of 2007 my nephew came for a visit and I put him to work.  We bought some PVC pipes, some corrugated vinyl roofing panels and some poly sheeting and we built me a greenhouse.  We built a sqare frame of PVC and laid it across the well where the stairs go down below grade from the top of the wall (which has a railing on it that conveniently holds the frame in place) to the wall of the house.  Then we covered that with the poly sheeting and put the roof tiles on top of that.  I used bubble wrap to drape over the doorway and the open end where the railing is - inside the poly which was also draped down below grade on all sides.

In October of 2009, I needed to replace the poly sheeting as it becomes brittle with time.  I had learned that water will accumulate on it and cause it to droop, so I added a brace to the center of the rectangular pvc frame.  I also lifted the bottom so that the poly sheeting was above ground level and the water could flow to the ground more easily.

This year, I again had to replace the sheeting and this year I am making a few more improvements.

First, the outside edge is all the framing this thing had the first year.  In 2009, I added the third top to bottom piece (the one under my daughter's feet).  This year, we (I had help again - this time from DH and DD) added two side to side braces which I hope will help keep the roofing panels from sagging.

These are the corrugated roofing panels and they are no longer flat.  Gravity combined with the heat of the sun here in Georgia to cause them to sort of melt in the middle.  I'm hoping they will flatten out a bit in the sun today and tomorrow morning but if not, I'll just use them with the humps up so gravity can flatten them back down.

Here is the framing in place.  Tomorrow it will be covered with a sheet of poly which will drape below grade on the end with the wrought iron railing and to the ground on the other end.  Then we will lay the corrugated roofing panels on top of that - I think I may tie some to the top of the pvc frame to keep them from sliding down since we have a steeper grade this year than ever before.  Lastly, we will lay another layer of poly sheeting over the whole thing again.  The corrugated roofing panels will create an air space between the two layers of sheeting that will help insulate the roof.

There is a pvc framed doorway that gets wedged between where the chimney sticks out and the outside wall.  Both the door and the end near the railing will also get a draping of bubble wrap for added insulation.

This has worked very well for the last four years.  I lose a few plants every year, but a lot less than when I tried to keep them alive in the garage.  And last year, I had tomatoes in December, January and even February (tho those didn't taste as good).

Tomorrow, we dress the frame and maybe move the plants.