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MackGideon</a> yup <a contenteditable="false" data-ipshover="" data-ipshover-target="<___base_url___>/index.php?/profile/551-azemocram/&do=hovercard" data-mentionid="551" href="<___base_url___>/index.php?/profile/551-azemocram/">@
AzemOcram</a> is right, it seems that partial transparency like the green house doesn't work. I tried making a panel of glass which was a faded white 'reflection' on a transparent back ground. The back ground was transparent in game, but the faded reflection just came out as a solid white block. So it either has to be all or nothing when it comes to transparency.
That being said, I did have an idea for a greenhouse. In blender, not sure about sketchup, you can model a scene then render it, save it as a png, and use it as a texture. This is how I did the trees, I made a few complex trees using partical systems and the like, really realistic looking trees, set up a camera and lighting, then rendered it, and saved the resulting picture as a png which I used as the texture for the branches of the actual game trees. So you can get a lot of detail in just a texture, and each branch is just 1 face.
So my idea was to set up a green house scene with plants and things, put a partial transparent glass around it, render it in the same way as the trees, then use this as a texture for the greenhouse window. The issue would be that you'd have to do either all four sides and a roof, so set up the whole scene and render if from different angles, or you could make the greenhouse with only one side glass. There is a cool barn near me that has the south facing side all windows, and the north, east and west a normal barn. They grow tropical plants in there and made a nice little oasis, great for 50cm snow storms.