Seal Fireplace Dampers with Weatherstripping to Conserve Energy
Fireplaces are the largest intentional opening in the home, costing U.S. families over $6,100,000,000 (based on figures as of March 2005) each year in wasted energy costs.
Like a door or window, fireplaces are openings to the outdoors and should be weatherstripped to prevent the loss of heated and/or cooled air. By weatherstripping the fireplace, several benefits are achieved including improved comfort, energy conservation, reduced energy costs, reduced noise, and improved indoor air quality.
Fireplace dampers are not effective at sealing the fireplace. When dampers are closed they do not provide an air tight seal and are quite ineffective at controlling undesired air leakage. Most fireplace dampers are left open. A study showed that 80% of fireplace dampers are inadvertently left in the open position1. Many fireplaces have broken and/or missing dampers.
In a 1990 study designed to measure the leakage area of fireplace with and without the damper closed, Energy Options Northwest had this impressive finding; the effective leakage area (ELA) of the fireplace dampers averaged about 30 square inches when closed. As a frame of reference, the total ELA of typical houses built to moderately tight standards is between 70 and 120 square inches. These results demonstrate that by weatherstripping the fireplace, the total effective leakage area (ELA) of the house can be reduced by 25 – 43%.
Another research study performed in Europe showed similar results. The study showed that an open damper on an unused fireplace in a well-insulated house can raise overall heating and cooling energy consumption by 30%2.
The majority of energy loss in the home is due to air leakage. Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly air sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment.
Building scientists and other experts agree that a significant amount of energy costs are wasted due to air leakage. Warm air leaking into the home during the summer and out of the home during the winter waste a substantial amount of energy dollars. See the collection of web references at the end of this paper.
According to the U.S. Department of Energy (DOE), the typical U.S. family spends approximately $1,300 a year on home utility bills, of which 44% goes for heating and cooling (as of March 2005).
Inadequately sealed fireplaces are noted as being one of the worst air leakage sources in the home. According to the D.O.E.3, by weatherstripping the fireplace, the typical U.S. home can reduce air leaks by 14% or more.
According to 2004 US Census Data4, there are 76,217,000 family households in the U.S. By multiplying the number of family households by the typical savings possible by weatherstripping the fireplace, the total annual energy cost savings that can be achieved by weatherstripping fireplaces is $6,100,000,000.
Of course not every home in the U.S. has a fireplace. However this only serves to increase the energy cost burden for the homes that do have fireplaces.
According to estimates there are 33,000,000 fireplaces in the U.S. By dividing the total annual energy cost savings that can be achieved by weatherstripping fireplaces by the number of homes with fireplaces, the average annual savings that can be achieved by weatherstripping the fireplace would be about $200.00 per fireplace.
Not Just Heating Losses Occur – Consider Air Conditioning Losses
Energy loss through fireplaces is not just heat loss. Fireplaces can also cost wasted air conditioning.
Consider a typical home that is provided with central air conditioning, and a fireplace. Air leaks in and out of ducts at all the connections within a system (e.g. at plenums and behind registers)5.
Of course this leakage means that air that occupants have paid to have heated or cooled escapes from the heating or cooling system and does not heat or cool the house. Air leaks into the heating or cooling system increase the amount of outside air that must be heated or cooled. Outside air is usually cooler (for heating) or warmer and more humid (for cooling) than air inside the house and the heating or cooling capacity of the system is then used to heat or cool this outside air instead of the air in the house. These issues are well documented and well understood.
But these air leaks also force air through the fireplace. How? By the pressure differential created by the duct leakage. Depending on where the duct leak is, it can cause a slight reduction or increase in the pressure inside of the home. Because the fireplace is a wide open hole to the outdoors, this will cause your air conditioning to either push air out of the fireplace, or worse, suck air in through the fireplace bringing odors and toxins in with it.
Other Benefits of Sealing the Fireplace
By weatherstripping the fireplace, several benefits are achieved, including improved comfort, energy conservation, reduced energy costs, reduced noise, and improved indoor air quality.
Un-weatherstripped fireplaces allow annoying and uncomfortable downdrafts. Back drafting brings cold air in winter that must be heated, and warm air in summer that must be cooled. Smoke particles and soot from a fireplace can enter into the living space, contributing to odors, poor indoor air quality, asthma, and other undesired problems.
When the fireplace is not weatherstripped, windows and doors can seem to have a cold breeze coming through them. This is caused by a condition known as the stack effect. Between the higher and lower pressure zones of the home lies a neutral pressure zone. The neutral pressure zone tends to move toward the largest air leak. The chimney’s neutral pressure zone is above the neutral pressure zone of the house. This creates a flow of air out the chimney even when no fire is burning. As the large volume of air is drawn up the chimney, warm air from other areas of your house goes up the chimney, too. This robs heat from the other rooms and pulls cold air into the home through cracks around windows and doors that have not been completely sealed. Sealing the fireplace helps stop the ‘breeze’ coming from your doors and windows.
Energy Codes Require All Openings Be Sealed
Energy Codes in force across North America require that all openings in the building envelope (doors, windows, attic access, etc) be caulked, gasketed, weatherstripped, or otherwise sealed to limit air infiltration and exfiltration. This is because air leakage through cracks can result in higher energy use for home heating and cooling than necessary.
The 2000 International Energy Conservation Code (IECC™) – is the latest version of the Model Energy Codes. It has been adopted either state-wide or in municipalities in 26 states, and specifies that all penetrations in the building envelope between conditioned and unconditioned space that are sources of air leakage must be sealed with durable caulking materials, closed with gasketing systems, weatherstripping or otherwise sealed to limit uncontrolled air movement (see IECC Sections 502.1.4.2 and 602.1.10).
Nearly all of the 50 states (as well as our territories) have adopted an Energy Code either the same as or based on a Model Energy Code. Model Energy Codes commonly used are the 2000 and 1998 IECC, or the 1992, 1993 and/or 1995 Model Energy Codes (MEC).
According to the “Plan Check & Field Inspection Guide for 1992 MEC, 1993 MEC, and 1995 MEC”, as well as the “Plan Check & Field Inspection Guide for 1998 IECC and 2000 IECC”, inspectors are instructed to verify that all doors between conditioned and unconditioned spaces have door boots and weatherstripping.
When inspecting for the Residential Provisions of the IECC/MEC, Building Inspectors are taught that proper air sealing will not only decrease the energy use of the building, but it will also increase the comfort of the homeowner and the durability of the home.
Building Inspectors are also taught that all penetrations in the building envelope between conditioned and unconditioned space must be sealed with durable caulking materials or closed with gasketing materials.
Like a door or window, fireplaces are openings to the outdoors and should be weatherstripped to prevent the loss of heated and/or cooled air. By weatherstripping the fireplace several benefits are achieved, including improved comfort, energy conservation, reduced energy costs, reduced noise, and improved indoor air quality.
Mechanical Codes Require Dampers to Be Permanently Blocked Open With Gas Log Sets
In an apparent violation of the Model Energy Codes, there currently exists a requirement in the 2003 International Residential Code (IRC) that the fireplace damper must be permanently blocked open when a vented gas log set is installed. This is intended to sufficiently prevent the spillage of combustion products into the room when the fireplace is used, and to prevent build up of gas should the pilot flame be inadvertently extinguished.
The unintended consequence of blocking the damper open is, of course, significant energy loss when the fireplace is not being used. This requirement is not in agreement with the Model Energy Codes that require all openings to be caulked, gasketed, weatherstripped, or otherwise sealed to limit air infiltration and exfiltration.
An alternative would be to simply instruct the homeowner to open the damper when using the fireplace. Instead of the IRC requirement that encourages energy loss, a reasonable solution would be to require a CO detector to notify the occupants of a build-up of combustion products into the room if the fireplace is used when the damper is accidentally left closed. At least one state (Massachusetts) currently requires homes to be provided with CO detectors6.
The Uniform Mechanical Code (UMC) requires all gas logs be equipped with a safety pilot control. The safety pilot maintains a pilot light and prevents gas flow to the main burner if the pilot is not lit.
Solutions Exist Today To Weatherstrip Fireplaces
There are several devices available today that are used to seal the fireplace. For example, top mounted chimney dampers. These are relatively expensive and have a poor return on investment (ROI). In addition they do not seal the fireplace at the bottom damper, leaving the chimney with all of its odors, toxins, and pollutants exposed to the home. In addition they do not address the wasted energy required to condition the chimney space.
It is often assumed that glass doors are a solution for sealing leaking dampers. This is not true, as glass doors do not air seal the fireplace opening. They do have decorative benefits, however.
There are other products available at hardware stores, etc. to temporarily seal off the flue and stop air from escaping up the chimney. One type of weatherstripping product is an inflatable plug that you insert into the fireplace beneath the damper. This type of weatherstripping is made of heavy plastic with an attached tube for inflating the device. The tube hangs down into the fireplace to remind you that the stopper is there. It can be removed to use the fireplace, and reinstalled again after. These devices have a very high return on investment (ROI), and can pay for themselves in one mid-winter heating bill.
Conclusions
There are 33,000,000 fireplaces in the U.S. As of March 2005, the total energy cost savings that can be achieved by weatherstripping fireplaces in the U.S. is $6,100,000,000, or about $200 per fireplace, annually.
There are devices available today to weatherstrip the fireplace that can provide a very high return on investment (ROI), and can pay for themselves in as little as one mid-winter heating bill.
Public awareness through education, training, and other methods are required to alert consumers of the amount of wasted energy from fireplaces, and to provide solutions.
The following action items are urged:
Educate the general public about the enormous cost of energy loss through fireplaces, and of the various ways to seal these openings between uses of the fireplace.
Add the requirement to weatherstrip fireplace dampers to the Model Energy Codes.
Allow an alternative to the energy wasteful requirement in the Codes that require the fireplace damper to be blocked open when vented gas logs are installed. As an alternative, the Code should allow the option to not block the fireplace damper in the open position when homes are provided with CO detectors and a safety pilot control.
Conduct further study of energy loss through the fireplace in both heating and cooling climates.
References:
1 Study documented by Joe Pate, Enviro Energy International Inc.
2 Ventilation perturbations due to an open fireplace in a house – P. Dalicieux and C. Nicolas.
3 http://www.ded.mo.gov/
researchandplanning/newsletter/electricity.htm
4 http://www.census.gov/population/
www/socdemo/hh-fam/cps2004.html
