Energy Efficient HVAC Design in Residential Buildings
Anna
1,2
Chang,
1Boise
Stephen
1
Thomas,
State University,
2University
and Dr. Yang
of Notre Dame
Introduction
Methodology
Energy efficiency has become a growing concern due to the negative effects
associated with burning fossil fuels and wasting natural resources. Building design,
including Heating, Ventilation, and Air-Conditioning (HVAC) systems, is essential to
manipulating heat exchange and promoting energy efficiency. As of 2014, about 40%
of global energy was consumed by buildings, with up to 60% of this dedicated to
space heating and air conditioning, so it is becoming increasingly important to control
and responsibly design the systems that require this energy (Huang et al., 2014). This
project reviews some of the currently available methods of building heating and
cooling, focusing on the overall systems and implementation. OpenStudio, SketchUp,
and EnergyPlus are used in this project to simulate certain HVAC systems in
standardized mid-rise apartments in Boise, Idaho, in order to determine the relative
efficiency of each system and the amount of energy needed to maintain the set points.
The various heating and cooling methods were reviewed and selected systems were
simulated in OpenStudio with EnergyPlus. OpenStudio supports the creation of building
models and translation to EnergyPlus and allows user interfaces for simulation engines.
The standard apartments were first designed in SketchUp using default conditions and
material constructions for a 4-floor, 33,744 ft2, Mid-rise Apartment with weather
conditions in Boise, Idaho. There were 8 units on each floor with a corridor, and basic
shading with a Window-to-Wall ratio of 40%. The HVAC systems were set up for each
Thermal Zone, or each unit, and simulated over a year to measure energy consumption.
and how well a median thermal zone was able to maintain set levels. Thermal Zone 10,
an apartment unit with similar results to the other units, was randomly picked to
measure how well it maintained set levels. The set levels in the apartments were about
75℉ for cooling and 70℉ for heating, for an average of 72.5℉.
Results
Thermal Zones of Mid-rise Apartment
HVAC Systems
A
B
C
D
E
F
G
H
I
Review of Main HVAC Systems Considered for Simulations
Type
Description
Advantages
Disadvantages
Direct Expansion Unit (DX)
[also applied to other HVAC
types for cooling]
Evaporator in the refrigerant cycle
directly contacts the air stream to
absorb heat
Less maintenance than Chilled
Water systems; lower installation
costs, simple operation controls
Split System Air Source Heat
Pump (ASHP)
Evaporator absorbs heat inside,
refrigerant flows to condenser to
release heat outside
Provide both heating and cooling;
Limited to mild climate for
requires less maintenance and
maximum efficiency
space
Ground Source Heat Pump
(GSHP)
Heat pump that accesses the relatively
Less noise; little maintenance;
stable temperature of the earth for heat
both heating and cooling
transfer
Water Source Heat Pump
(WSHP)
Condenser water absorbs heat from
cycling refrigerant; water coils transfer
heat elsewhere
Packaged Terminal Air
Conditioner (PTAC)
Through-the-wall heating/cooling units
that use a compressor system and
electric heating
Packaged Terminal Heat Pump Similar to PTAC, but heat pump is
(PTHP)
primary heating source
Furnaces
Uses fuel/electricity to heat air and
distribute it through ducts
Requires ductwork in central AC
High initial installation cost;
needs body of water nearby if
Surface Water Heat Pump
Both heating and cooling; more
Efficiency decreases with colder
efficient than air-source; can heat
temperatures
water
Easy installation; durable; no
ductwork; good for zoning
Larger, more expensive than
window units; need bigger hole
than mini-splits; noisy
Easy installation; no ductwork;
good for zoning
Weaker performance in very cold
conditions; noisy; large hole
needed
Inexpensive; little maintenance
Fan noise; fuel emissions;
require filters for allergens
1
Lu
Cycling PTAC DX
Clg Elec Htg
Cycling PTAC DX
Clg Gas Htg
Natural Ventilation
Packaged Rooftop
Heat Pump
PTHP
Water-source HP,
Gas Backup
Electric Furnace,
Cooling Coil DX
Gas Furnace,
Cooling Coil DX
GSHP
Discussion
According to the results, gas heating generally requires more energy than electric, and heat
pumps with backup heating have the advantage of consuming less energy while still
maintaining the same temperature as other HVAC systems. In future studies, price and
other factors could be considered through OpenStudio’s cost analysis and utility bills
function, because PTHPs seem to use the least energy for the set temperature but can be
expensive, noisy, and large. While all heat pumps may be more efficient in this scenario,
variations of them, such as ductless mini-split AC and heat pumps, would be beneficial to
consider in an apartment setting, since they could take up less space and be quieter. The
orientations of heat exchanging loops in GSHPs could also impact their consumption and
ranking. The energy efficiency of all HVAC systems could also increase by combining them
with renewable energy technologies, so the application of solar heating and electricity from
solar panels to power the systems would be important to consider in the future. This could
significantly decrease buildings’ energy consumption and their contribution to climate
change.
References and Acknowledgment
Huang, J., Lv, H., Gao, T., Feng, W., Chen, Y., & Zhou, T. (2014). Thermal properties
optimization of envelope in energy-saving renovation of existing public buildings. Energy
and Buildings, 75, 504–510. http://doi.org/10.1016/j.enbuild.2014.02.040
Department of Energy, http://energy.gov/energysaver/heat-and-cool
This research was supported by the National Science Foundation through the Division of
Materials Research under Award No. 1359344 and Boise State University.