Skip to main content

NetZero Energy Architects "Hybrid" Home Energy Design

Solutions that Reduce Home Energy Use While Increasing Quality and Comfort.
About Us
The Old Yellow House Orin
Artist Recognition Award
Annapolis Passive House
Passive House
Annapolis Basement Energy
Marin Home & Garden Expo
West Coast Green 2010
Earth Day 2010
Home Performance Test
Fresh Air Ventilation
MechanicallyVentilated CS
Geo-Solar Thermal Energy
Crawl Space Case Studies
Design Build Partnership
FreeWatt - Cogeneration
Geo Thermal
Danville 2010
Alamo Remodel 2010
Alamo Residence 2010
Carmel 2009
Vert Ramp 2008
Lafayette 2007
Potrero Hill S.F. 2006
Lafayette 2006
Lafayette 2005
Caith Tree House 2005
Lafayette 2005
Lake Almanor 2004
Los Altos Hills 2003
Buddhist Spiritual Center
Los Altos Hills 2001
Wright Studio 2001
Bell Canyon LA 1999
Santa Monica Canyon1998
Oakland Hills 1997
Brentwood L.A. 1997
Japan 1996
Oakland Hills 1993
Beverly Hills 1995
Peter Falk B.H. 1995
Venice 1990
Solar Mansion B.H. 1989
Jellyfish UCLA 1985
Jellyfish Malibu 1985
Laser Jellyfish B.H. 1983
Solar Greenhouse Md. 1981
Private Study Gaudi 1980
U of MD. Daylighting 1980
Tree House 1965
Site Map
Contact Us
Member Login
Crawl Space Facts
Fresh Air Ventilation
“Air Flow Design”
Ventilation-distribution is the key in the overall energy efficiency, thermal comfort, and health needs.

For an excellent understanding see video link @

Due to the energy concerns of today, people are sealing their homes tightly to save energy on heating and air conditioning. Unfortunately, these tightly sealed homes are developing very unhealthy indoor air quality.

Consequently, a new mechanical code is being adopted as of January of 2011 that will require fresh air changes in new residences to combat this unhealthy indoor air quality. In conjunction to this, a new energy code also requires new furnaces to have a “constant fan” feature, which saves heating and cooling energy by mixing the indoor air of the home. This clean air requirement and the necessity to circulate air within the homes have opened up an opportunity providing fresh air and cut energy consumption using a “Energy Recovery Ventilator” (ERV), conditioning fresh air in conjunction with a crawl space.

This simple device is cost effective, uses little energy, and transfers the energy of the incoming “clean air” to the exiting “stale air” maintaining the temperature within the home. An ERV provides fresh air with minimal loss of indoor temperature.

Air Displacement

Mixed polluted fluid


The unique solution to your ventilation needs! Air Displacement works with natural principles to provide a reduction of ventilation air while increasing air quaulity. Like the clean water on the bottom of the illustration, breathing air is kept clean while hot, dirty air is displaced to the ceiling where it is exhausted. Conventional systems, like the water below, mix dirt and fresh air creating an unhealthy environment.

Conventional Dilution Air Systems cannot compete with the air quality Air Displacement systems because conventional systems try to clean air by mixing it. Yet, just as warm, dirty, water cannot become clean mixing by mixing it with cool, clean water, so dirty breathing air cannot be cleaned by mixing in fresh air. Air Displacement eliminates this problem by using the difference in air densities to thermally seperate the hot dirty air and the cool, clean air.

Since the air being placed on the ground by the Air Displacement system is several degrees cooler than the existing air, it is denser and stays on the ground. The warm, humid air, which contains the dirt, is displaced to the ceiling because it is lighter, or at a lower density. Warm air, dirty air is generated by a whole range of things, including people and the machinery they use. The thermal stratification is similar to placing oil and water in a glass. They do not mix because they are different densities. What the process means is clean, fresh air stays where people want to breathe while dirty air is exhausted at the ceiling. Ventilation air comes through a large duct near the ground at extremely low velocity. Air can also be delivered through fabric duct work.

Ventilation air for heating and cooling before the invention of powered fans encouraged natural, vertical air displacement arrangements. The Teepee of Native American Indians with a hole at the peak is a natural draught chimney where heavy cold air is slowly drawn in through the perimeter opening formed by the rolled-up covering to be heated by the wood fire blazing in the center on the ground and radiating heat. The Egyptian Pyramids were built with internal ducts formed by the layered stone to encourage natural ventilation by placing the openings low and in the coolest air to allow the hot, low pressure on the sun exposed top to pull the air through. This has been a no- maintenance/no-energy reliable ventilation system for nearly 4000 years! Many homes in steamy hot tropical regions are multi-story open structures are cooled with natural air displacement. Built into a high river bank with large louvered openings at ground level facing on a moist riverbed with the outlet high on the opposite top side above the bank for the prevalent breeze to induce the pressurized cool air up through the house. Also known as Natural Convection for re-circulated air, this type of air movement is caused by differences in the relative weight or pressure of a given volume of air.

Conventional and Air Displacement Comparison

Conventional "Mixed/Diluted-Air" systems typically filter polluted air. Filter units re-circulate the cleaned air.

Natural Air Displacement Ventilation systems by contrast use "Separated/Displacement Air" to provide exceptionally clean breathing air at much lower operating costs. Nature's way of moving heated air to the ceiling by natural

convection without blowing air around is used. This natural or vertical air displacement system distinguishes itself from forced, horizontal air displacement systems because 1) air movement is by gravity and 2) clean air below is separated from polluted air above. Thermal layers of air from floor to roof keep the clean air near the floor and the dirty, contaminated warm air moving to the roof peak.

Air Displacement Vents

This vertical air displacement ventilation system relies primarily on the unique operation of floor mounted air displacement ventilation outlets (air displacement vents). (Insert "Air Displacement Vent" diagram} These unique metal air displacement vents distribute ventilation air near the floor at a very low exit air velocity. As the fresh air is controlled to a lower air temperature than the room, this clean air is discharged slowly from the air displacement vent and remains low in the breathing area above the floor without mixing with hot, polluted air at the ceiling. Outdoor ventilation CFM required is calculated to maintain desired air quality in the breathing zone only since no ventilation air is required to dilute the polluted air at the ceiling. Fuel costs are slashed owing to significantly improved 1) air displacement vent exit temperature and 2) reduced quantities of ventilation air.

Ventilation Projects

Vertical Natural Air Displacement systems have provided industrial fresh air since the mid 1960s. Installed first in Scandinavian countries, air distribution vents have been installed in thousands of European industrial facilities, schools, hospitals, concert halls, shopping malls, foyers, banks, offices, industrial complexes and every kind of public building.