A whole house filter is part of a mechanical heating and cooling system with air ducts. The filter is located just before the return air enters the AC air handler for cooling, or enters the furnace for cooling. The filter protects the mechanical equipment and keeps dust out of the air ducts. A fine enough filter also improves the health of interior air by removing tiny particles such as pollen and bacteria.
A filter’s MERV rating from 1 to 20 indicates how small a particle can be removed from the air. The larger the MERV rating, the smaller the particle which can be removed.
Lowest rated MERV 1 to 4 are filters are used to protect the HVAC equipment from the buildup of dust on the surfaces of fan motors and heating or cooling coils. These are not used for air quality purposes. By contract, ultra-fine MERV 16 filters are used in hospital operating rooms to filter microscopic bacteria from the air.
MERV 7-13 filters are recommended for homes. For example, a MERV 8 filter can trap particles as small as 3 microns – like dust & pollen, mold spores, and dust mite body parts and droppings. The smaller holes in a MERV 11 filter can trap particles as small as 1 micron – like smoke & bacteria. A MERV 7-13 filter can improve the quality of life for those with asthma and allergies. It is a very practical way to improve the health of your home.
If you ever experienced carbon monoxide poisoning, you would know how important it is to safely vent all your combustion appliances to outside. These include hot water heater, gas clothes dryer, furnace, space heaters, and stoves.
In order to appliances to vent properly to the outside, there needs to be sufficient combustion air and a properly configured vent or chimney system. If there is too little combustion air, for example in a tight well-insulated house or in a utility closet, the combustion gases will not be efficiently drawn up the vent and chimney. As a result, the appliance will not burn its fuel efficiently and combustion pollutants will back-draft into the home’s living spaces.
The remedies to cure back-drafting include: supplying outside combustion air to the appliance; opening up the appliance to more interior air; or, installing an outside air vent to allow more air into a home’s interior. Of these alternatives, supplying outside combustion air is the most efficient.
An electric clothes dryer “breathes” in lots of interior air, uses it to dry clothes, and vents it outside. A gas dryer also breathes in and vents combustion air. For energy efficiency, it may make sense to bring outside air to the laundry room. This would prevent the infiltration of cold air in winter, and hot air in summer, to make up the air vented by the clothes dryer. This would be especially important in a tightly air sealed house.
The ancient open hearth fireplace is a much loved symbol of home. However, for millennia it has puffed toxic wood smoke into a home’s interior, and heated it inefficiently.
Open hearth fireplaces draw in pre-heated combustion air from your home’s interior and wastefully sends it out the chimney. Even when the fireplace is cold, it can still leak warm interior air. (This can be minimized by means of a fireplace balloon damper.)
Sealed combustion fireplaces remedy these traditional problems. A sealed glass window isolates the combustion chamber from the room interior. No smoke gets into the home interior.
Combustion gases (e.g. dangerous carbon monoxide) are directly vented to the outside and never enter the room. Combustion air is piped in from outside, keeping your pre-heated interior air inside, where it belongs. A heat exchange device, located around the combustion chamber, blows hot air into the home’s interior.
The principle of sealed combustion can also be used in efficiently running furnaces and wood stoves. This is especially important in super-insulated homes. These homes are tightly air sealed which limits the supply of internal air for combustion. Thus, back-drafting of heating appliances would be a danger. Also the tight air sealing means that there is less exchange of outside air to disperse indoor air pollutants like wood smoke and carbon monoxide. This is why any furnaces, stoves, or fireplaces used in super-insulated homes are specified for sealed combustion.
Can your garage be an indoor air pollution culprit? It does have some suspects: car exhaust; gasoline fumes from lawnmowers and chainsaws; pesticide and herbicide vapors; and, paint solvent fumes.
Even driving a car into the garage, turning off the engine and closing the door, results in emissions of various chemicals that can linger for hours as the engine and its fluids cool down. Over time, pollutants in the garage air can be drawn into the house.
There are several strategies to protect living quarters from garage pollution. The best is to simply site the garage away from the house. If the garage is adjacent to the house, it is important is to air seal the entire garage/interior boundary. This includes house entry doors, and the top of the basement wall, if exposed in the garage. This basement header space can be notoriously leaky.
Another strategy is to minimize pollution sources in the garage. It is essential to keep mechanical systems, such as furnaces and water heaters, out of the garage. Also, to minimize the storage of gasoline and other toxic chemicals.
Another strategy is to install a garage exhaust fan. According to LEED (Leadership in Energy and Environmental Design) standards the garage ventilator, should be ducted outside of the home. The air flow should be a 70 cubic feet per minute (cfm) if it exhausts directly through the garage wall. If the exhaust runs through duct before leaving the garage, the flow rate should be 100 cfm. The exhaust fan must either run continuously or have an automatic timer control. The timer should be linked to an occupant sensor, light switch, garage door opening/closing mechanism, carbon monoxide detector or equivalent. The timer must be set to provide at least 3 air changes each time the fan turns on.
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