I live in the Mid-Atlantic USA, where the indoor humidity ranges from 20% in the coldest part of winter to up to 70% in the summer. I have an ebony grand piano with a Dampp-Chaser. I am thinking of creating micro-climates both under and over the soundboard. Regarding the over-the-board climate, I understand the goal is to achieve a uniform moisture level in the soundboard rather than having a moisture gradient across the soundboard that would occur when the top and bottom of the soundboard reach equilibrium with the different air humidity levels to which they are subjected.
Based on previous pianoworld posts, it seems that many technicians recommend installing an undercover. Where can I purchase an undercover? Can I make my own? Is installing an undercover a specialized task requiring a technician's skill?
The more difficult issue appears to be creating an effective micro-climate over the soundboard. When I had the lid down but folded back, the humidity over the soundboard was exactly the same as the room humidity. I now have the lid closed completely. This appears to help a little (32% room humidity vs. 35% humidity over the soundboard), but there is still a ~1/8 in. gap between the closed lid and rim. Some recommend adding a fabric cover over the piano, but unless the cover fit tightly, I suspect that air gaps would persist. Has anyone measured the effectiveness of such coverings?
I thought it might be more effective to add 1/8 in. thick black foam weatherstripping on top of the rim. Does anyone have experience or thoughts about this?