William writes from Lachine, Quebec: "Our church, built 1952, has concrete block walls, no insulation, stucco outside, no interior wallboard. We proposed to insulate on the inside but were told this could cause frost problems in the block wall. Can this type of wall be insulated on the outside?"

Answer: Placing insulation on the interior side of the wall will change the performance of the wall since it will no longer see the heat from the building it previously absorbed in the winter months. However, these types of walls have been insulated successfully before from the interior. It is important to determine the correct amount of insulation to prevent this from happening based on interior conditions and building location (exterior conditions). A qualified building envelope consultant will be able to do such an analysis to determine the correct type and thickness of insulation to prevent wall from freezing and minimize heat loss and high energy bills.