How Design and Layout Play a Part.
The system that heats and cools your home didn’t just happen by chance. Much thought and effort went into the design and installation of each component that makes up the total HVAC system.
There are 3 primary steps that are taken during the design phase.
1. How much heating and cooling is really needed for my home?
The first step involves a multitude of calculations to determine the Heating and Cooling Load of the home. The book Manual J, produced by ACCA, is the standard used to calculate heating and cooling loads. Every building component used to construct your home is meticulously accounted for. Some of these components include the types of walls, insulation values, windows, doors, ceiling, attic, floors and more. This process is very time consuming if performed correctly. There are now software programs to help speed up this laborious process, but it still requires a lot of knowledge and effort to get the right results. After this data is input to calculate the total heating and cooling needed for the house at predetermined outdoor temperatures, the next step is performed.
2. Equipment sizing and Selection, “Bigger is Better…Right?” Well, not really…
During this phase of the process, various furnaces and air conditioners are evaluated to find a good match for each home. It is imperative that the equipment have enough capacity to condition the home without being oversized. “Rules of Thumb” used in the past have no business in modern HVAC designs. Oversized furnaces can reduce the life of the heat exchanger (which is it’s primary component) by causing the furnace to start and stop too often. This prevents the furnace from cooling down properly and the heat exchanger experiences heat stress and may develop cracks. The air conditioner also suffers stress if cycled on and off too often (verses running longer each cooling cycle). This costs homeowners more in the long run by having to replace parts and equipment prematurely.
With that in mind, the guidelines in ACCA’s Manual S must be followed! This book explains how to find the correct sized furnace and air conditioner based on manufacturers specifications. Not all furnaces are created equal and not all manufacturers size equipment the same. Therefore, following proper procedures will prevent undersized or oversized furnaces and air conditioners. Your house will be comfortable and efficient, and your equipment will last longer.
When it comes to properly designing an HVAC system, “Rules of Thumb” can take a hike!
3. The last step is designing the Air Duct system.
So we now know how much heating and cooling is needed for our new home, and have selected a furnace and air conditioner based on proper calculations and methods. We need to get the air from the furnace blower to each area of our home that requires conditioning. That’s where Air Ducting comes in to play. For years many Air Duct systems were installed using more “Rules of Thumb”! During this critical step, we can’t fail now by just installing ducts “the way it’s always been done”. There are actual procedures written out in ACCA’s Manual D. This book provides everything needed to figure out what size of air ducting is needed to get the proper air to each room. This step, like the previous two, takes time to complete properly.
As you can see, the HVAC Design process is a lot of work! But, the benefits far out-way all the time taken and expense incurred by creating a far more comfortable and energy efficient home. Your entire Heating and Cooling comfort system will last longer. And, less energy is consumed which helps conserve our natural resources.