Are there any general non-trivial methods for solving the following problem?
Suppose one has a collection of subsets $\mathcal{C} \subseteq \mathcal{P}\mathcal{P}\{1,\dots,n\}$. They may be viewed as generating a sub boolean algebra $\langle\mathcal{C}\rangle \subseteq \mathsf{2}^{2^n}$ of the free boolean algebra on $n$ generators.
Let $G \subseteq \langle\mathcal{C}\rangle$ be a subset whose closure under unions contains $\mathcal{C}$. I would like to compute the minimum cardinality over all such sets $G$.
For example:
If $\mathcal{C}$ consists of the $2^n$ atoms then the answer is $2^n$.
If $\mathcal{C}$ consists of the $2^n$ co-atoms then the answer is $\leq 2n$ by choosing $p_1,\neg p_1,\dots,p_n,\neg p_n$.