Determining the heating and cooling “load” is accomplished by performing a calculation often referred to as a “Manual J” This is where a HVAC contractor takes the physical measurements of the home to include doors and windows, insulation values, and other home construction details.
With this information, he or she is able to “calculate” the necessary British Thermal Units (BTU’s) necessary to properly size the equipment needed to heat and cool the structure.
With new construction, Contractors will often use the square footage to “estimate” sizing for pricing purposes. This is fine, but the contractor should always confirm the load by performing a calculation on a room by room basis.
With retrofit installations (replacing existing systems), many contractors will replace the system with an equally sized system. A load calculation often reveals oversized equipment that has a direct relationship to energy costs.
Less is more
One might think that a larger furnace or air conditioner will heat or cool more quickly. This is what I call the “Tim Allen” approach. Ar Ar Ar..
The truth is that “Goldie Locks” was on to something. You want a system that is not too big, not too small, one that is just right.
A common complaint among home owners is that it’s comfortable on the first floor, but too hot or cold on the second level.
A properly installed system must deliver air as to maintain a minimal temperature drift throughout the home. One can do this by installing separate systems, or by installing a Zone System. There are many manufacturers out there, but I recommend EWC for its superior quality. Visit them at http://www.ewccontrols.com
Buyer beware, several Counties in Maryland (Carroll included) have no inspection process for Heating and Air Conditioning. With that said, it’s important that you choose a reputable company. We recommend obtaining references, and checking with your Better Business Bureau.
Three costs of a system: The initial purchase cost, the operational costs, maintenance/repair costs.
Where maintenance or repair costs are often relative to the quality of the equipment selected, any reputable HVAC contractor can provide a projection of utility or fuel costs based on your geographical area and average “degree days”.
In the quest for higher efficiencies, heating and air conditioning products have changed considerably. Gas furnaces have become more efficient by using secondary heat exchangers, variable speed blower motors, and 2 stage, or modulating gas valves. Air conditioners have become noticeably larger; they may also be equipped with two stage compressors, and whisper quiet fans. Indoor air handlers also employ variable speed blowers, and thermostatic expansion valves (TXV’s) which adjust refrigerant flow automatically.
Metal prices have “gone crazy”! Air conditioners are made of Copper, Aluminum, Steel, and Brass. So it’s no surprise that equipment costs have risen an average of 18% per year. It’s not sticker shock, its reality.