Moisture problems
We've had a couple of condensation related problems related to cold weather and high interior humidity. Sam, your weather is a bit different from ours in Maine, but you may have more consistently high humidity, I don't know if you'll have anything like this or not.
First, our skylight. The plastic dome is double layer with a gap between. The seal on this skylight is bad--frost between the two layers. My contractor says he can see a possible bad spot in the edge seal. The edge of the skylight has a metal cap (aluminum). The outside of the cap is exposed to Maine winter, the inside to lightly heated air--heated with propane fired salamanders, a source of a bunch of humidity. Guess what--the skylight metal condenses water pretty fast. Once enough gathers, it runs down the inside of the skylight. Our plasterer is not going to be happy with this situation.
The plan is to insulate what we can outside, also insulate the metal on the inside. During construction they are going to put a concrete blanket over the top. We're hoping this will get rid of actual dribbles. Another possibility would be to add an interior layer of plastic--sort of a storm window on the bubble.
The second source of condensation are the tubes penetrating the roof. Same deal, the black plastic tubes have outside, cold air on the outside, warmish damp air on the inside, water dribbles. There are pipes running up some of the tubes. Sealing between the black outer tube and any stuff inside with foam seems to work fine (the foam seal is at the bottom of the tube=ceiling level). I didn't see, I think they used a combination of foam insulation board and some spray foam (canned stuff) to fill in the cracks.
So we've got a solution that works on the black tubes, I think our skylight solution is workable (maybe with a tweak or two). The $64,000 question is why didn't Terra Dome guide us so we wouldn't have these problems?
Rust Spots in the Ceiling
The walls are 10" concrete with rebar. Form ties (1" metal strap) run through the wall. The ends of the form ties are broken off flush, leaving a bit of exposed steel. The concrete dome ceiling has some wire ties (maybe tying rebar together?) that come through the inside surface in places. Now that plaster and underlayment has been put on the walls and ceiling, some rust spots show up. The walls are fine--no rust showing anywhere. The ceiling has rust spots wherever there is a wire end. The spots are maybe 1-3mm in size. This isn't horrifying--it isn't like the ceiling has measles. Again, the big question is why didn't Terra Dome warn us about this. They say they've made a bunch of these, they ought to know about it. Our contractor is freaking out, the owners are a little calmer.
Sam, I'd consider toothbrushing any wire ends you can find with a phosphoric acid steel prep solution, then painting them with some kind of good sealer like an oil based primer. The phos will convert any existing red rust to black oxide and leave a paintable surface. You can either use a metal prep product or they also have phos. acid based concrete cleaner (I get it at Home Depot). Wear goggles, the toothbrush will probably spray all over.
Back to the roof pipes: one of the things I'd advise anyone building one of these is to add extra black pipes to the roof. You could cut any extras off flush on the outside and cap it. We had three sun tubes planned, but had to use those tubes for other things, no sun tubes. Someone building these with experience would have put the right number of tubes through the first time--again, why didn't Terra Dome recommend enough tubes?
That's all for now,
Steve
who is helping our contractor figure this thing out in Maine