Green Building HVAC

greenbuildingBuilding Professionals

Green HVAC Resource

 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 house.
  • An HVAC system works best when it takes local climate and building designs into account.
  • In a green-built home, heating and cooling equipment can be smaller, less costly, and less complicated.

See Chapter 9 on HVAC in the Green from the Ground Up book for more details or contact us about training.

Designing a System

Central to this premise of thinking small are the many passive solar features built into a green house. 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 homes with increased insulation saving money

Size HVAC system to meet actual loads using Manual J
  • System is sized appropriately for actual home 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

Green from the Ground Up Best Practices

  • Make sure the HVAC contractor designs heating and cooling equipment according to established industry procedures
  • Design the HVAC system in conjunction with other building components, including insulation, windows, solar mass, and orientation.
  • Reduce the size, expense, and complexity of mechanical systems as much as possible.
  • Install properly sized fans in all bathrooms and in the kitchen.
  • In a larger, whole-house ventilation system, consider a heat recovery ventilator to capture latent heat that would otherwise be lost.
  • Specify high-efficiency heating equipment and air conditioners with a high SEER.
  • In forced-air systems, run ducts through conditioned space where possible and seal all duct connections with mastic.
  • Avoid electrical resistance heating unless it’s used only on an intermittent spot basis.

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 attic or 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 whole house fan

A fan will help circulate air and reduce the need for air-conditioning by sucking the hot air out of the house quickly. It can also be used for nighttime cooling

An insulated, airtight seal is necessary to prevent air leakage. A whole house fan is usually installed in the attic.

Find and energy star rated product. Install a fan that has more than one power setting.

Install a heat recovery ventilation system

Recovers heat from exhausted indoor air and transfers it to the incoming fresh air stream

Necessary if the house has less than 0.35 natural air changes per hour.

System installed in conjunction with the furnace or A/C unit.

Green Building Training & Certification

Find out when the next Green Building Training is and learn more about Green Building Practices.

Read more on the Federal Tax Credits for HVAC
Central A/C Split Systems:
  • EER >=13
  • SEER >= 16

Package systems:

  • EER >= 12
  • SEER >= 14
  • 30% of cost, up to $1,500

Air Source Heat Pumps Split Systems:

  • HSPF >= 8.5
  • EER >= 12.5
  • SEER >= 15

Package systems:

  • HSPF >= 8
  • EER >= 12
  • SEER >= 14
  • 30% of cost, up to $1,500

For a list of qualified products, go to the Consortium for Energy Efficiency product directory , click on the Air Conditioners and in the “CEE Tier” enter “Residential Advanced Tier 3” for CAC Split Systems, and “Residential Tier 2” for CAC package systems and ASHPs.

Note — not all ENERGY STAR products will qualify for the tax credit.

ENERGY STAR Spec (same for CAC and ASHP):

Split Systems:

  • HSPF >= 8.2
  • EER >= 12
  • SEER >= 14.5

Package systems:

  • HSPF >= 8
  • EER >= 11
  • SEER >= 14

Natural Gas or Propane Furnace

  • AFUE >= 95
  • 30% of cost, up to $1,500

Oil Furnace

  • AFUE >= 90
  • 30% of cost, up to $1,500

Gas, Propane, or Oil Hot Water Boiler

  • AFUE >= 90
  • 30% of cost, up to $1,500

For a list of qualifying products go to the Gas Appliance Manufacturing Association

Not all ENERGY STAR products will qualify for the tax credit.


  • Gas Furnaces: AFUE >= 90
  • Oil Furnaces: AFUE >= 85
  • Boilers: AFUE >= 85

Advanced Main Air Circulating

  • Fan No more than 2% of furnace total energy use
  • 30% of cost, up to $1,500

For a partial list of qualifying products go to the Gas Appliance Manufacturing Association

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