This time of year, many homeowners are calling on insulation companies as they have in years past to install insulation when there is a perceived need. Additionally, homeowners now have the choice of air-sealing due to increasing recognition of its cost-effectiveness as a way to start saving on heating costs. Most insulation companies (including those that air-seal) do not provide air-safety combustion information or associated testing services that are in the best interest of the homeowner's safety.
When certain types of insulation are applied or when your home is air-sealed with spray foam and caulking, the number of air leaks in the home is decreased. This lowers the natural air exchange rate (rate that indoor air needs to be exchanged with fresh, outdoor air for health of the home's occupants) and may affect the natural draft needed for the safe operation of furnaces and boilers that use indoor atmospheric air for combustion. Reduced air exchange rate combined with certain conditions such as extremely cold outdoor temperatures, leaky duct returns and exhaust fans could cause strong enough negative pressures inside your house to suck potentially deadly combustion gases back down a chimney.
There are tests that should be conducted every time insulation is added or air-sealing is performed, both of which cause the natural air exchange rate to be lowered. The first test is called a worst-case depressurization test and the second is a combustion safety test. The depressurization test is conducted by an energy auditor or technician who turns on all exhaust fans, the clothes dryer and air blower (when forced hot air exists) in an attempt to create the worst-case negative pressure in the house under which backdrafting of the furnace or boiler may occur. A manometer is used to measure the degree of negative pressure created in the house, and the measurement indicates the potential for backdrafting. If the negative pressure is severe, flame roll-out could occur, representing a more dangerous threat.
While the test is being conducted, any backdrafting combustion gases, such as carbon monoxide, can be monitored with a meter in the area around the heating system. The flue gas may also be measured directly with an electronic combustion gas analyzer to indicate that it either is working properly or is a potential source of problems.
In summary, every insulation company that applies spray foam insulation, installs rigid foam board, hydraulically blows in cellulose insulation or performs caulking and weather-stripping that is likely to reduce air leakage should provide you, the homeowner, with the basic services described above when open or atmospheric combustion appliances exist in a home. Given that currently companies can insulate or air-seal without safety testing, it is your responsibility as an educated consumer to ask for this safety testing or to find a company that provides it.
If after insulation is added or air sealing is done, and safety tests show that a backdrafting is likely or a strong possibility, there are steps that can be taken to fix the problem and provide you with assurance that your home is safe. The energy auditor or technician can describe these steps and implement them until testing shows a safe condition.
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Tim Gould is director of Energy Egghead (www.EnergyEgghead.com), an Amesbury-based home improvement company that provides thorough energy audit and energy conservation services.
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