We had some reservations that it might add warmth to the bed while sleeping but we haven't found that to be the case. If there is the slightest warmth it is totally overcome by the comfort of the featherbed.

Yes, most fitted sheets for deep mattresses fit over the featherbeds. FEATHERBED CARE & CLEANING: I recommend a featherbed cover with a high thread count and tight weave, to keep it clean. I use an anti-dustmite polyurethane-backed mattress cover, made like a fitted sheet, that goes over the featherbed & mattress. The fitted sheet goes on top of that. Nothing gets through polyurethane, even liquid, so the featherbed doesn't get dirty. The polyurethane-backed mattress cover is machine wash/dry. It doesn't diminish the featherbed feel, because the polyurethane is super thin, bonded to a thin cotton terrycloth top. To kill dustmites & freshen, put the featherbed outside in the sun, or, run it on a high-heat dryer cycle (I do this with my pillows). Spot clean stains. I use Febreeze Anti-Microbial spray on both sides of the featherbed, when I wash the sheets. Give it a good shake to refluff and rotate it for more even wear. Using these techniques, I haven't had to launder a featherbed. If I did, I would wash & dry it in commercial machines. I would not subject it to dry-cleaning chemicals. Check the label for manufacturer's cleaning instructions. Hope that helps!