If you have tightened up your house by making energy efficient upgrades such as adding insulation and/or draftproofing, etc., you may need to compensate by using a good ventilation system. A heating or ventilation contractor can do a fan pressurization test to determine the extent of air leakage and infiltration in your home.
If your windows show signs of condensation, chances are you need more ventilation. Heat Recovery Ventilation Systems (HRV's) not only help with energy efficiency, they also make your home healthier and more comfortable. An HRV's job is to provide continous air changes within your home, exhaust moisture and do it in a way that is energy efficient. The old, stale, moist air is passed through a heat exchanger that preheats the new fresh air that is brought into your home.
Much like the installation of any heating equipment, the quality of installation usually determines how well your new HRV system will operate. It is extremely important to hire someone that knows how to size and design the duct work as well as install the HRV unit itself.
For more information about HRV systems, visit www.lifebreath.com