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Impact of a natural gas fireplace on home heating energy consumption
Armstrong, M. M.; Burrows, J.
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Home Builder, 23, 5, pp. 1-2, 2010-09-01
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I m pa c t of a na t ura l ga s fire pla c e on hom e he a t ing e ne rgy
c onsum pt ion
NRCC-53608
Armstrong, M.M.; Burrows, J.
September 2010
A version of this document is published in / Une version de ce document se trouve dans:
Home Builder, 23, (5), pp. 1-2, September 01, 2010
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Impact of a Natural Gas Fireplace on Home Heating Energy Consumption By Marianne Armstrong and John Burrows
This article summarizes the results of a study designed to assess the impact of operating a
natural gas fireplace on the heating energy consumption of an R-2000 house.
It is estimated that about one quarter of Canadian households have a gas fireplace, many of
which are used daily during the heating season (2007 Survey of Household Energy Use,
NRCan). When a fireplace is located in close proximity to the house’s central thermostat, the
heat introduced by the fireplace can cause the heating system to delay its normal cycle of
operation – affecting energy consumption and temperatures in the home. Over two winters (2008
to 2010), researchers at the Canadian Centre for Housing Technology (CCHT) assessed the
impact of operating a natural gas fireplace in an R-2000 house. The interaction of the fireplace
with the central heating system was explored, including impact on the furnace’s gas and
electrical consumption, and room and surface temperature effects.
The study examined three modes of fireplace operation: continuous evening fireplace operation
from 18:00 to 24:00 with the furnace providing continuous air circulation; continuous evening
fireplace operation from 18:00 to 24:00 with no continuous air circulation provided by the
furnace; and fireplace operation by dedicated thermostat. In addition, the impact of pilot light
operation was also investigated. The experiments were conducted in the CCHT twin house
facility and compared conditions in a house with and without a gas fireplace.
Evening operation of the fireplace heated the main floor family room, the location of the gas
fireplace, well above the 22°C set-point of the furnace thermostat. During this time, furnace gas
consumption and furnace fan electrical consumption decreased. Overall, however, evening
fireplace operation resulted in an increase in total energy consumption (natural gas and
electricity for fan operation), 12.5% for continuous furnace fan operation and 11.6% without
continuous fan operation. When furnace and fireplace efficiencies were taken into account (76%
measured fireplace efficiency, and 94% measured furnace efficiency), the net energy supplied to
the house by the fireplace and the furnace was higher by an average of 2.8% than a house with
no fireplace, and up to 12% greater on the warmest days. This is likely an indication of
overheating from the fireplace on warm days.
Operation of the fireplace by dedicated thermostat control resulted in a large reduction in furnace
operation, owing to the close proximity of the fireplace to the central thermostat of the house. On
average, this mode of operation resulted in an overall increase of 9.8% in total heating energy
consumption. Despite this increase in consumption, the total heat output was 2.3% lower. This
was reflected in the cooler temperatures on the second floor (1 to 2°C cooler), evidence that the
furnace did not cycle frequently enough to sufficiently heat that part of the house.
Only one fireplace thermostat setting was examined. A lower setting would likely reduce
fireplace operation, increasing furnace cycling and circulating heat more readily to other rooms
(with high speed air circulation during heating). During warmer weather, the effect of thermostat
operation on furnace operation could be even more pronounced – the fireplace may be able to
satisfy the requirements of the house thermostat, eliminating furnace cycling. Higher furnace fan
air circulation speeds at standby (when not supplying heat) could be explored to determine if
increased air movement would improve the distribution of heat to the second floor.
Pilot light operation also had an impact on energy use. Keeping the fireplace pilot light burning
consumed an average of 38 MJ of natural gas per day. Pilot light operation decreased furnace gas
consumption by 5.6%, and furnace fan electrical consumption by 1.7%, but increased overall
energy consumption by 5.0%. It resulted in a ~ temperature increase of about 0.3°C in the family
room and a small decrease on the second floor (about 0.2°C).
The fireplace efficiency testing showed that the operation of the circulation fan built into the
fireplace did not affect steady-state efficiency – this model of fireplace showed the same
efficiency with and without the circulation fan operating. This means the fireplace could be
operated during a power outage and still provide the same heat output. Without electricity, the
furnace fan would not operate to circulate the fireplace heat to other areas of the house. A future
experiment could examine the impact of such operation on room temperatures, to determine
under what conditions and for what duration a fireplace could be used as a backup heat source
during a power outage.
___________________________
For more information, see the full report at http://www.ccht-cctr.gc.ca/eng/projects/fireplace.html
or contact Marianne Armstrong at [email protected] The Canadian Centre for Housing Technology is jointly operated by the National Research
Council, Natural Resources Canada, and Canada Mortgage and Housing Corporation.
Marianne Armstrong is a research council officer in the Building Envelope and Structure
program of the NRC Institute for Research in Construction. John Burrows is an engineer and
technical writer.