The advent of improved insulating materials and techniques have also created a major problem; inadequate ventilation.

A tight seal is very desirable in regard to preventing drafts and insulating the house. But the tight seal doesn't allow the house to "breathe."

That is, there is no exchange of fresh air to remove moisture, pollutants and odors. Such conditions target a house for "Sick Home Syndrome."

In winter, it's not practical to throw open a window and run a fan. A practical method for circulating air is necessary. One system of choice is an Energy Recovery Ventilation (ERV) system. An ERV provides moisture control, indoor air quality, and energy recovery.

The ERV is based on a few simple principles:

• An Exchange of Air: The ERV brings fresh, outside air into the house while pumping stale, indoor air outdoors.
• An Exchange of Energy: Warm, stale air (including air condition air in summer) from inside the house gives its energy to incoming cool (warm in summer), fresh air from outside.

The ERV transfers energy by passing both air sources very closely together in separate networks of ducts. The air doesn't mix, but the temperatures do.

High performance ERVs can be about 80% efficient in exchanging heat in winter and about 30% efficient in summer. Some models have a pollution sensor built into the switch to immediately prompt an air exchange.

Old Homes vs. New Homes

Older homes usually have a good deal of outside air infiltration: around inefficient windows, at the foundation, and through underinsulated walls to name a few. Although it is very energy inefficient, a small supply of fresh air enters the home.

This is not the case with recently built homes. Insulating products like house wraps that protect outside sheathing, high quality fiberglass insulation and energy efficient windows all create a tight seal. The house has no fresh air exchange at all.

Signs of Poor Ventilation

Do your allergies get worse in the winter months? Do your windows fog up and bead water frequently? Are there stains or discolored spots on walls? These are all common signs of excessive moisture/mold build up in the home.

These symptoms usually show up within the first five years -- even immediately -- after a new home is built. At the same time, moisture decays building materials.

Decay is hard to spot, because it often takes place inside walls. It can even show up first on the outside causing siding to warp, paint to peel and stains. No amount of house cleaning will solve the problem. Only proper ventilation, in conjunction with a vapor barrier, will correct moisture build up.

Sources of Moisture

Excessive moisture often comes from indoor sources. The clothes dryer, shower, cooking, houseplants, even breathing produce moisture.

The important function of the vapor barrier is to protect the interior of walls and insulation from escaping moisture. However, the moisture is still trapped in the house.