Hi Frances, very dry air is likely to mean your starter and bread dough will require more hydration, so it sounds like you're taking the correct approach, although 200% hydration seems a bit extreme unless you're feeding your starter with entirely whole grain flours. Of course, there's nothing wrong with maintaining a stiffer dough-like starter either, which is generally the type of starter I prefer to work with. Be sure to cover your starter well so it doesn't dry out on the surface, and when you're maintaining your starter at room temperature try to feed your starter when it's ripe (at it's peak of rising, or just beginning to fall), which will help to keep the yeast vigorous. 

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