High Performance HVAC

 


There are several terms that describe the efficiency of heating and cooling equipment. The Annual Fuel Utilization Efficiency [AFUE] describes the performance of a furnace. The Heating Seasonal Performance Factor [HSPF] describes the performance of a heat pump. The Seasonal Energy Efficiency Ratio [SEER] describes the performance of an air conditioner.

Minimum
Better
Best
SEER
10
12
16+
AFUE
80
85
92
HSPF
6.8
7.2
8+

 



Heating and cooling system sizing was previously done by “rules of thumb” for example square feet per ton of cooling or Btus of heating per square feet. This typically results in HVAC systems that are oversized.


This graph shows the result of an interesting survey that found 100% of the systems examined oversized. The yellow line designates sizing using ACCA Manual J which is 115% of the design cooling load. Such oversizing can cause comfort problems related to high humidity due to short cycling of the system. It also wastes energy resulting in higher energy bills.
Chapter 14 of the IRC requires heating and cooling loads to be performed to size equipment.Manual J or an approved equal are required.
The Outdoor Design Temperatures are based on the ASHRAE/IESNA 90.1-1999 Standard and represent 99% for heating and 1% for cooling.

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