The audits, which take about two - and - a-half hours, are designed to identify major energy leaks in a house. (realtormag.realtor.org)
Whatever energy leaks out into space is replenished by the Sun, which is why this leaky system seems to run on a perpetual internal, not external, engine that throttles up and then back in a somewhat unpredictable but nonetheless oscillating fashion. (wattsupwiththat.com)