Contractor Tom Silva installs PVC exterior trim that looks like wood in the Concord, Mass., barn and joins carpenter Norm Abram and host Kevin O'Connor to install sunroom windows that resemble the traditional windows in the main house. Silva also shows O'Connor how to mix concrete and O'Connor also tours a facility in Menomonie, Wis., where residential window glass is manufactured. On “Ask This Old House,” projects include replacing a rusty bathroom-sink stopper and installing a prefinished hardwood floor. Also: Silva discusses the pros and cons of various types of flooring.