These sweaters can be knitted with any yarn that is the correct thickness. Wool, cotton, silk, acrylic, hemp or any other fiber yarns can be used. The top down sweaters look best knitted at a slightly loose gauge. If the pattern calls for 4 stitches to the inch, look for a yarn that has a recommended gauge of 4 or 4 1/2 stitches to the inch. This information should be on the ball label. If it is not, ask the person in your shop, who can look up this information.
You can also combine yarns to get the gauge. A strand of fingering weight yarn combined with a sport or dk weight yarn often knits great at 4 to the inch. Just make sure that you do a swatch and that it is loose and drapey. Please don’t use a bulky yarn, and knit it on a smaller needle to get 4 to the inch. It makes a stiff sweater!