Concrete Blocks -- Concrete blocks are used in foundations and are often found in full basements. Insulating the spaces in the blocks is not the way to insulate them as the heat energy will travel along the concrete itself. The best way to insulate with concrete blocks is to use insulated concrete blocks, which have polystyrene incorporated into them.
Heaters exist for various types of fuel, including solid fuels, liquids, and gases. Another type of heat source is electricity, normally heating ribbons composed of high resistance wire (see Nichrome). This principle is also used for baseboard heaters and portable heaters. Electrical heaters are often used as backup or supplemental heat for heat pump systems.
HRV/ERV Ventilators: These whole-house ventilators exchange air. They are ideal for homes with what is called a “tight envelope,” homes where house wrap has been applied and airgaps in the attic, around windows, doors and outlets have been sealed. Air in these homes becomes stale and polluted, so exchanging the air is important to IAQ. Heat recovery ventilators (HRV) are designed for cold climates. Energy recovery ventilators (ERV) are best for warm climates. Your cost for an installed HRV or ERV will range from about $2,000 to more than $5,000 based on its capacity and features.
In addition to the information below, see these two articles for the general care and maintenance of your air conditioner: Preparing Your Air Conditioner for Summer and How to Replace Furnace & AC Filters. Most noteworthy, you should replace the filters at least twice a year, before the heating and cooling seasons. For information on furnace problems, please see Furnace Not Working.