24/7 Emergency Services Available 
Back to Top

HVAC Information


One of our goals is to provide HVAC information that helps to educate those around us. We believe if you are informed, you’ll see even more value in our services!

Gas Furnaces

Gas Furnaces burn natural gas or propane to heat the air in your home. 80% efficient gas furnaces are the minimum efficiency available today, with 90%+ efficient furnaces becoming the industry standard. 90%+ furnaces use a different type of heat exchanger (the component that separates the fire from the air stream & allows the heat transfer) and they vent via PVC instead of metal piping. Furnaces have either a multi-speed blower motor or a higher efficiency ECM (Electrically Commutated Motor) motor. ECMs are quieter and more reliable, and they offer more airflow options. ECMs usually run at 60% of full speed when the fan is on when the furnace isn’t heating and cooling. The gas valve in a furnace controls the gas flow to the burners – the valve can either be 100% on/off, 2 stage or modulating. Higher efficiency furnaces use a 2 stage or modulating gas valve for more even temperature control and greater efficiency.

Air Filtration & Indoor Air Quality

Today’s homes are built with very little air leakage and infiltration, often resulting in increased problems with indoor air quality. On average, indoor air is usually 2 to 5 times more polluted than outside air. Air filters are often the most overlooked part of an HVAC system, yet they are the simplest way to keep a system working cleanly and efficiently. Furnaces and air handlers come from the factory with a place for a filter, but this is usually the minimum required to keep the equipment relatively clean. Upgrading the system’s air filter is a must if more than minimum filtration is desired.

Filter efficiency is rated using a Minimum Efficiency Reporting Value…known as a MERV rating. The higher the MERV rating, the better the filtration, with HEPA filters having the highest efficiency. Air filters should also be installed in ducts or equipment so that there is no leakage past the filter – if air can leak, then so can dust!

Air Conditioners & Heat Pumps

Air conditioners use the refrigeration process to move heat from inside a home to the outside. Heat Pumps are like air conditioners, but they can also reverse their operation and move heat from outside into the home. Both A/Cs & H/Ps have an indoor coil (usually located in the ductwork by the furnace) that the indoor air moves through. Heat pumps run a little differently too – they will often build frost on the outdoor coil and go into a defrost cycle. Heat pumps usually need a backup source of heat but are very efficient systems for the weather we get in Oregon.

Heat Recovery Ventilators (HRV)

Heat Recovery Ventilators or HRV’s are units that exhaust stale air from inside, bring in fresh outside air and transfer heat between the exhaust and fresh air. HRV’s are nice because they take the place of bathroom, laundry and kitchen exhaust fans, and in the cool months they save a percentage of the heat from the stale air. They transfer this heat to the incoming fresh air which helps with the home’s indoor air quality.

Radiant Heat

Radiant heat is usually installed in or under the floor, so heat radiates from the floor, heating the room. Hydronic radiant heat is hot water from a boiler or water heater being circulated through pipes in the floor. Radiant heat is very comfortable and efficient, but these systems don’t include a blower or air handler so cooling and air filtration are handled by a different system.

Notes on equipment efficiencies:

  • Gas Furnaces are rated by their AFUE- Annual Fuel Utilization Efficiency. Most standard furnaces are 80% AFUE (80% of the gas being burned is turned into usable heat). Higher end furnaces are 95% to 97% AFUE.
  • Heat Pumps are rated by their HSPF- Heating Season Performance Factor. HSPF can be looked at as the average ratio of heat output to electrical input. The higher the number.,the more efficient the unit is. Most heat pumps range from 7.7 to 9.8 HSPF, and the Oregon Department of Energy recommends at least a 9.0 HSPF.
  • Air Conditioners are rated by their EER (or SEER) – (Seasonal) Energy Efficiency Ratio. (S)EER is the ratio of cooling output to the electrical input. The higher the number- the more efficient the unit is. Most air conditioners are 13 to 18 (S)EER.

HVAC Information: Ductwork

People often don’t know how important their ductwork is, but the ductwork for an HVAC system is vital to the proper operation of the system. Ductwork should be designed properly for the type of system that is installed. Ducting should also be insulated and sealed properly, or the efficiency of your heating or cooling system can be diminished.

Ductless mini splits/heat pumps

Ductless mini-split-system heat pumps (aka mini splits) were developed in Asia over 20 years ago, and are very efficient. In addition to being space-saving in design, they can also provide dehumidification. Some rebates/credits are still available for high-efficiency systems like ductless mini splits. They are usually simpler than standard heat pumps to install, and can mean saved space that would usually be taken up with ductwork. 

Contact Morrison Heating and Cooling today.