Breathe easy: The importance of free airflow in your home
Posted January 20, 2011
Winter is officially here, and with it people are spending more time indoors, sealing out the cold and damp weather with closed windows and doors.
If you’re finding that your home suddenly feels stuffy or clammy, or if common colds now seem like a chronic condition for your family members, it might be time to check the airflow in your home.
Think of your home as a system (and look for the same thought process in any contractors you work with). In this system, the airflow of your heating and air conditioning system represents the breathing mechanism for your home, with the HVAC unit serving as the lungs of the house.
Whether it’s you or your home, to have healthy lungs you want clean, fresh air to be circulated frequently and easily through the system, while eliminating stagnant, moist, or contaminated air.
Aside from the obvious health benefits that comes from breathing clean fresh air more often, ensuring free airflow in your home reduces utility bills and saves energy. The HVAC unit uses the most energy in almost every home. Whether you use electrical heat or some type of flammable fuel, one of the most important things you can do to maximize efficiency of the unit is to provide good airflow through it.
Properly sealed ductwork
I cannot the stress the importance of properly sealed duct work. It’s sad but true that most duct systems installed to current building codes still leak almost 30 percent of the air that flows through them. Not only does this affect proper air flow, but it can cause other issues, as well.
First, leaky ducts are inefficient. You are paying to heat and cool air that is supposed to come out of the vents in your house, not leak into the attic or crawl space. Leaky ducts can cost you an extra 10 to 20 percent on your heating or cooling bill.
Second, leaky ducts can cause create unhealthy air in your home. Most of you don’t like to venture in your attic and crawl space for obvious reasons, so why would you want that air flowing freely inside your home. This is especially important for small children, elderly and anyone with respiratory sensitivities.
Lastly, leaky ducts can cause your house to under negative or positive pressure (depending on where the leaks are); which can cause your house to leak conditioned air to the outside, or suck unconditioned air into your home. Either of these conditions put undue stress on your HVAC system, costs you money and can lead, again, to unhealthy air inside the home.
A sufficient sized air return
Every central heating and air system should have an air return that is large enough for the same volume of air to return that the system puts out. A rule of thumb on the size of this opening is 1-square-foot per one ton of your system's size. The system itself works best when the air flows freely from the furthest part of the house.
Many homes aren't designed to allow proper airflow, even when the return opening is large enough to accept the necessary volume. Every interior door in the home should have sufficient space beneath it to allow the return of any volume of air that is dumped into the enclosed room from the HVAC unit.
In some homes, I’ve seen high pile plush carpet on the floor that sits so high that the air gap beneath the door is almost eliminated. There should be a minimum of one inch of clear air space under each interior door unit.
Draft stoppers that lie across the bottom of your door may seem like a good idea, but they create capsules of stagnant air in rooms, reducing the efficiency of your HVAC system and in fact contributing to a cooler home overall as the air can’t circulate properly. If your home is drafty, solve the problem at the source with proper insulation techniques, rather than playing running back with airflow.
Air return shaft accessibility
Wherever the return shaft is located for the HVAC system, you should take care to keep it accessible. Many homeowners place furniture in front of air returns located in walls, forcing the unit to work harder to obtain air, and thus reducing how much air is pumped through the unit. As a rule of thumb, use the width of the air return vent as the measure for how far from the wall your furniture should be placed to allow proper airflow.
If the sight of the air return shaft offends your interior design sensibilities, most home improvement stores carry a wide selection of cosmetically appealing options for vents.
The importance of the lowly air filter
The "lowly" air filter is one of the most neglected parts of a central heat and/or air conditioning system, and yet it is so vitally important. Depending on the type of filter you have, you may be able to clean it rather than throwing it away, but the important concept is to keep it clean to allow your heating or cooling unit to work the way it was designed. A cleaner filter means higher efficiency performance.
Clean or replace your filter every two or three weeks religiously, and you will be doing yourself a big favor. This one small task can add years to the life of your HVAC appliance. Not sure if you’re cleaning your filter often enough? Remove any floor register in your home and turn it over – if there’s a large accumulation of dust and debris on the bottom side of the register, you may want to change your filter more often.
With all the talk of ensuring free airflow through you home, it may sound like a good idea to completely remove the air filter. It’s not. The filter serves the important purposes of providing clean air, and stopping allergens and germs from being continuously re-circulated through the home. It also ensures that small objects pulled into a vent or dropped into a register aren’t sucked into the HVAC unit where it could cause thousands of dollars of damage.
The exception to the rule: Closed crawl space sealing
Your crawl space is the only thing that stands between your living space and the earth - and the earth is damp. Crawl spaces are a primary source of excessive moisture in our region, and moisture is a leading cause of structural and air quality issues. Over 60 percent of the air in your ground floor living area comes through the crawl space.
Unhealthy, moist air leaking into your home means your heating and cooling systems need to work harder too. By properly closing the crawl space you will see energy reductions of between 5 to 20 percent.
Experts used to recommend ventilating crawl spaces well – but things have moved on. Most research now shows that properly closing and sealing a crawl space is best practice for green, efficient and healthy buildings. (It’s standard practice for Energy Star homes.) Luckily, even old fashioned ventilated crawl spaces in most existing houses can be upgraded to a state-of-the-art closed crawl space - adding value and improving the performance of your home.
Cleaner air means a healthier environment
Think of the airflow to your unit as you do your own breathing. If you can't get enough air, your life will be shortened, but having an abundance of clean air will help to keep you healthier and for a longer duration.
Bobby Ferrel is co-founder of Green Horizon – a Durham based company with offices in Charlotte, offering home owners and builders a one-stop shop for energy efficiency and green building. Services include energy audits, weatherization, insulation, HVAC installation and maintenance, rainwater harvesting and geothermal heating and cooling. NEW! Now in Charlotte! Reach Bobby directly at firstname.lastname@example.org or visit him online at www.greenhorizon.com