Nothing beats the coziness of your own home especially during those cold, winter nights. But when you're freezing in it despite having a furnace then there's a problem. A good way to check if poor air flow is the concern is to use the garbage bag airflow test.

One of the most common issues with heating and cooling equipment is poor air flow. This problem makes your heating and cooling equipment work like inefficient outdated models and this can waste a lot of your money. The two most common reasons for poor air flow: inadequate duct sizing and a dirty return air filter.

Inadequate Duct Sizing

Inadequate duct sizing is usually the result of a poor installation by a contractor who might possibly not have the qualifications to perform proper sizing. This is a very common problem that a homeowner may battle for years to come and could cost thousands of dollars over the life of the equipment. It is extremely crucial that you get references before choosing a contractor.

A Dirty Return Air Filter

A dirty return air filter is the easiest problem to fix. Simply change your return air conditioning filter more frequently or utilize a filter that does not restrict air flow. This simple change can lead to huge savings.

How You Can Perform the Garbage Bag Air flow Test

Garbage bag airflow test is one of the easiest and cheapest methods to determine the air flow of your furnace registers, bathroom exhaust fan or clothes dryer exhaust. It's a vital test to pinpoint the reason why your furnace isn't providing sufficient warm air in your room. This is also important in order to determine whether your newly purchased exhaust is working at its best. The same goes when you're having major renovations in your home that call for a change in your heating or cooling systems. It's the cheapest way to check your furnace register and exhaust fans performance as it only requires a garbage bag. This test isn't a precise measurement of the airflow but it is better than not conducting any test at all.

Here's how to do the garbage bag airflow test:

1. Secure the mouth of the garbage bag using a tape right into a bent coat hanger or to a cardboard in order to keep it open.

2. Be sure to deflate the bag by crushing it flat.

3. Position the open part of the bag (mouth) over the furnace register or exhaust hood.

4. Using a stopwatch or any gadget track the number of seconds it takes for the bag to fully inflate.

If you're using a small garbage bag that measures 66 x 91 cm, you should use the information below to determine the airflow:

Inflation time = Airflow

*2 seconds = 35L/s (75 cfm)

*4 seconds = 20 L/s (40 cfm)

*10 seconds = 10 L/s (20 cfm)

However, if you're using a bigger garbage bag that measures 79 x 119 cm, use this data:

Inflation time = Airlfow

*2 seconds = 100 L/s (210 cfm)

*4 seconds = 50 L/s (105 cfm)

*6 seconds = 35 L/s (75 cfm)

*10 seconds = 20 L/s (40 cfm)

If you have measured an airflow that's less than 10 L/s, then your furnace is providing you with just a small amount of heat. If this is the situation you may need to do further investigation to find out why the heat is not going through.

Garbage bag airflow test can also be used to determine the amount of air going out. This is called the deflation test. This test though isn't as good as the inflation test in determining low air flow. In doing the test, you simply hold the inflated bag over the exhaust grill and count the number of seconds it takes for the bag to be fully deflated. The amount of air that goes out can be determined by adding a second on the inflation time. Thus, 35 L/s would take 3 seconds, 20 L/s for 5 seconds, and so on.