These days we are bombarded with more options than we care to have to review when it comes to selecting what we wrap our window and door frames with, bump the vacuum into, or hide the sheetrock joint at the ceiling line. These items fall into the category of interior trim. When selecting trim, keeping the basic design of these three elements in the same family is key to keeping the hodgepodge to a minimum. If a period style, such as Federal is being built, it would be architecturally incorrect to put anything other than moulding profiles that were common to that period of history. Consistency in design selections plays a key role in the enhancement of spaces.
In recent years, I have been pleased to see MDF (Medium Density Fiberboard) being used for some of the trim components. When this product first hit the market, may years ago, trim carpenters didn't care for it because when cut, it would chip and flake. Since then, the products have become far superior and trim carpenters tend to prefer to use this product for crown. Its most redeeming features are that it does not expand or contract like wood, and it takes paint really well. With wood, when winter sets in, the low humidity often causes cracks to form along the caulk joints of trim because of the amount of shrinking that takes place. What we have found that works best is to use MDF for the crown, and keep the casing and base as wood, most commonly Poplar. This minimizes the cracking problem and puts easily repairable wood in places than can get damaged. Not only is MDF more stable at varied moisture content, it also is less expensive than solid poplar, and some manufacturers produce it as "green". What more you could you ask for of a product?
MDF used as crown moulding has become a great asset to residential architecture, combining workability, longevity, and cost savings into a single product. I highly recommend its use.