Is a less quilted (fluffy) quilt warmer than one that is heavily quilted?
 

Given the same weight and type of batting is used in each quilt, for example, polyester, medium loft, does the fat, fluffy quilt trap more heat?

Does anyone know?

The fluffier one should be warmer. The more dead air space there is, the more insulation is provided.

Exactly as Neesie said. That's why layers of clothing are warmer than one single heavy weight item.

but the more densly quilted quilt is heavier....that's for sure. If I do any over 80x90" and do densing quilting I can hardly lift them!!!!! but then, it could be cuz I'm a weakling!!! :)

When fibers are compressed they loose some of the insulating properties.

The thing I think about is if its "fluffy" when washed its gonna lump up isn't it? I have a fluffy comforter that the fluff is all clumped. but my feather comforter is closely quilted and its fine. Hmmmm. I need to have info too.Please

I go with Neesie - it is the dead air space that makes it warm.

It's the nature of the filler, that makes it clump or not. One thing you can try, is putting three new tennis balls into the dryer, with a comforter. That MIGHT help but unfortunately, the older polyester filling usually does clump. I always use the tennis balls, when I wash/dry my down coats (loosely quilted), to keep them fluffy.

Each different batt has specific maximum quilting distances. Going further apart than is recommended might result in the batt breaking down and thus the clumping.