Energy conservation, indoor air quality, and comfort are among the core green building issues encompassed by heating, air-conditioning and ventilation design. These interrelated systems can be complex, expensive to install, and costly to operate but green building also offers many opportunities to simplify and save:
HVAC is more than a few pieces of mechanical equipment. It's a system designed as part of the building.
An HVAC system works best when it takes local climate and building designs into account.
In a green-built building, heating and cooling equipment can be smaller, less costly, and less complicated.
Designing a System
Central to this premise of thinking small are the many passive solar features built into a green building. HVAC design follows other fundamental building steps that can collectively reduce the size of the heating and cooling system by 30-50%. Solar orientation, insulation, window placement and design, even vegetation on the building site all directly affect heating and cooling loads. Designing a system based on real demand, not conventional practice, is essential.
Green HVAC Transition Guide
Incorporate HVAC systems early in the design phase
Makes installation easier and more efficient. Dedicated chases will cut down on labor costs and project complexity.
One or two meetings with the architect or engineer early in the building process.
Systems can often be smaller in green buildings with increased insulation saving money
Size HVAC system to meet actual loads using Manual J
System is sized appropriately for the buildings needs. Reduced heating bills and protects air quality.
Careful calculations based on room and home size. The home’s orientation, insulation and window placement affect the heating and cooling load.
Manual J is software from ASHRAE
Specify high efficiency furnaces and air conditioning units
Save clients energy and money. Increases comfort and reduces pollution. Reduced peak grid load.
Research which manufactures sell the highest efficiency units in your area.
Energy Star models furnaces or air-conditioners with a SEER of 14 or higher.
Seal around electrical outlets and all wall penetrations
Small penetrations can mean a lot of heat loss over the life of a building.
Squirt a small amount of foam to seal each penetration
One can of expansion foam. Look for products that use HFC rather than HCFC or CFC as propellants.
Size ducts appropriately using Manual D heat loss calculations
Ducts are sized appropriately for actual room by room needs. Heat or cooling is efficiently blown to all rooms of the house effectively.
Ducts are installed and sized for maximum performance
Manual D is software from ASHRAE
Seal all ductwork with mastic
Leaky ductwork looses pressure and wastes as much as 20% of conditioned air as it travels.
Brush mastic over any joints or bends
Low VOC mastic is a paste available in home stores. Do not use duct tape as it dries out all falls off.
Insulate all ducts in the crawl space
When warm air ducts pass through unheated areas, they looses efficiency. Insulation will help lessen the energy loss.
Carefully wrap ductwork with duct insulation and seal.
Specific duct insulation is available-use as high R-value as possible
Design adequate returns to keep the house pressure balanced
Negative pressure can draw carbon monoxide from gas water heaters and furnaces due to inadequate returns.
Use Manual D and S software from ASHRAE
Make sure that each room has adequate return ducts or doors are undercut sufficiently to allow air flow
Install a heat recovery ventilation system
Recovers heat from exhausted indoor air and transfers it to the incoming fresh air stream
Necessary if the building has less than 0.35 natural air changes per hour.
System installed in conjunction with the furnace or A/C unit.