www.youtube.com/watch?v=g_IxeFxhvhQ

If you find the winter months to be a little to dry inside your house... a bypass humidifier may be the perfect solution!

How to Install a Programmable Thermostat

What Does HVAC Duct Do?

In homes with a central heating or cooling system, the duct can be viewed as the highway the fresh air, or conditioned air takes, as it makes it way into each of the areas of your home, and back to your central HVAC unit.

All Central HVAC Systems use two main duct runs to move that air:

• Supply Duct - which supplies the conditioned air throughout your home. You can identify with the supply line easiest by going to one of the vents in your floor, wall or ceiling. The air got there through one of the supply ducts. If your unit is in the attic or crawl space of your home, you can immediately recognize the supply duct as it will (should) all be wrapped in insulation.
• Return Duct - which takes air from your home, and returns it to the central unit to be conditioned. To understand the business end of the return duct, just go to the filter grill where you change your HVAC filters every month. The air entering through the filter is the return air. In your attic or crawl space, the return duct may be insulated as well, but in most cases, it is just sheet metal or flex duct.

Types of HVAC Duct in Residential Use

In most homes you will only find a few types of duct.

Sheet Metal Duct - which is a smooth wall galvanized sheet metal, either squared or rounded. Sheet metal duct work moves the air most efficiently through your home, since the inside of the duct is smooth and has no ridges or obstructions to disrupt the flow of air. in addition tot he duct itself, sheet metal duct must be wrapped with insulation before or after it is installed, in order to provide a thermal barrier between the unconditioned space and the air moving through the duct.

Insulated Flexible Duct - Likely the most common over the last 20 years or more, flex duct does exactly what it sounds like, it flexes, making it the quickest to install and easiest to use in most installations. Flex duct generally comes in compressed rolls of 25 feet, in many various sizes and varying r-values, or Insulating values.

Insulated Duct Board - This type of duct has become more popular in the past few years. The easiest way to understand duct board, it to think of a 4x8 sheet of insulated board, 1/2 - 1 inch thick. The board is then cut and squared, to form a box through which the air flows. Many new construction homes have gone to this type of duct due to the ease of installation and high performance insulating value.

In a future post, I am going to get into the duct sizing methodology, and help you understand how different sized ducts can effect your home HVAC system.

Additional Reading Resources

• Wikipedia

Gas Furnace Deals

Before you look for a bargain on a new furnace, educate yourself with a bit of information, so you can know what your are talking about when the time comes that you shop for a gas furnace deal.

Know the Basics about your Existing Gas Furnace!

The two major things you need to know about your existing HVAC gas furnace are:

1. Furnace AFUE, or Efficiency
2. Poise, or direction of airflow on your current furnace

Current AFUE - Annual Fuel Utilization Efficiency

Knowing your current efficiency is more important that you know! If you have a naturally vented furnace right now, there may be some limitations on how you vent the new unit! For instance, most older furnaces are 72-80% afue. They vent through a chimney or other metal flue system. If you decide to go higher efficiency and get a condensing furnace, you have to consider how it will get fresh air and vent through the roof or sidewall of your home.

Furnace Poise

Essentially, there are three very popular types of furnace poise.

1. Upflow Furnaces- The most common poise, where the fresh air enters the furnace from the bottom, and the heated air flows in an upward direction, out through the ducts. These are most commonly installed in utility closets, basements, etc. If your furnace is standing up on one end... it is most likely an Upflow furnace.
2. Counter, or Downflow - Where the air enters the furnace from the top of the unit, and travels in a downward motion, where it enters the duct. These are most commonly installed in either a TALL attic or an garage in a warmer climate where heat is not often used. The furnace stands on one end as well.
3. Horizontal Flow- Wher the air enters on one side or the other, and travels through the system horizontally. These are easily identified as the furnace is lying on its side. These are most commonly installed in Attics or crawlspaces.

Quick ID Tip - If you have central air in your house also, just locate the AC evaporator coil. It will have 2 copper lines leading into it. The coil is always on the exit side of your furnace... so if you see it on the bottom, you have a downflow. If its on top, you have an upflow!

Always Ask for a Better Price!

I dont care if you found a Goodman Gas furnace Dealon ebay, or you are talking with a local contractor you found on Angies List. ALWAYS ask for the best price! If you are ready to buy right then and there... just ask one simple question: "If I buy right now - whats your BEST Deal?"

From a sales perspective, your salesperson should be asking you that question... beat them to the punch and ask first! You WILL save additional money just by asking!

Related Reading

To learn more about Gas Furnaces... visit the wikipedia page and start reading!

Gas Furnaces on Wikipedia

Home Inspection of a Gas Furnace unit in an interior closet.