I beg to differ - when at anchor there is always a breeze and that keeps conditions acceptable aboard. Only in marinas, where there's no wind, or during rainshowers when hatches are closed, is it uncomfortable aboard. All boats will have 12VDC fans that move air around sufficiently. W hat is certain is that a 30-ish foot long monohull won't have a genset or A/C. My problem in the summer when the winds die down is with mosquitos. When the typical trades are blowing there's no need for flyscreens or a bed mosquito net aboard; but when the wind stops the mozzies arrive... and they are hungry...