I was out on a call yesterday 03/30/09. A beautiful house overlooking a golf course.Had to be worth somewhere around $1.5-$1.75 million.The cost was important to me because they had the same problems with their heating system as the rest of us do.Doesn't matter if you live in a 1300 sq ft house or 5000 sq ft house.Doesn't matter if your house is 60 yrs old or 6 yrs old.They had never had their ducts cleaned,no one had ever told them it could done.I pulled out 6 yrs of dust bunnies,food and debris from outdoors not to mention the construction materials that had been dumped into the duct system when the house was finished 6 yrs ago.They both suffered allergies while at home.It seemed to improve when they weren't home.That was an easy fix.They had NO filter in the furnace.And their system was never sealed properly.Most of their heat was heating their crawl space.Cold rooms all over the house.They thought it was because the rooms were so big but I showed them what the problem was and how easy it was to fix it.That was one of my biggest tips to date.