Natural ventilation is one of the most energy efficient, natural ways to maintain healthy indoor air quality in a home and reduce energy costs.
Natural ventilation moves indoor air pollutants out and keeps the temperatures more comfortable, by relying simple things like buoyancy to move air around a home.
Air flow through the attic space is key to natural ventilation. The general rule to achieve the air flow is 50% intake under the eaves and 50% exhaust near the peak of the roof. Ideally, the system should allow greater intake than exhaust.
Many historic homes still have classic signs of natural ventilation – wide eave overhangs, narrow rooms, and a roof ridge that was built to work with the prevailing winds. At the same time, many new homes fail to meet minimum building standards for natural ventilation.
Homes that fail the natural ventilation test often result from one of these 5 modern home building problems:
1. Odd or Complicated Roof Lines
Roof lines have become more complicated on modern homes, resulting in the need for careful calculation of intake and exhaust. Not everyone gets it right.
Typical vinyl soffit with inadequate airflow.
2. Wimpy Soffit
Technical improvements have been made in exhaust technology, but the same cannot be said about intake technology. Most full vent soffit products do not give you enough air intake or NFA (net free area) to work with the exhaust defeating the whole purpose of a balanced system.
3. Tiny Overhangs
Modern design standards want smaller overhangs, it can be difficult with most intake products to provide enough ventilation for the exhaust at the ridge vent.
Modern homes often have overhangs that are less than 1′ wide.
It’s challenging to get enough airflow when using only center vented soffit.
4. Inadequate Center Vent Soffit
For aesthetic reasons, center vent soffit is often selected to handle intake. Many center vent soffit products decrease intake, so intake becomes insufficient to balance exhaust.
5. Complicated Building Codes
In many cases, builders do not necessarily follow the minimum building codes through lack of understanding or awareness of proper ventilation, and inspectors may not verify compliance with the codes.