Finding Your Comfort Zone

While doing the research to size the heating/cooling units in our remodel, I have found that the heating and cooling load software programs available to the residential owner are mostly unsuitable for a customized home. They can also be expensive and for a one time user rather limited in their format for calculations. In green or sustainable construction, it becomes a bit more obvious that standard equations based on builder construction systems do not allow for improvements such as thermal conduction slabs, solar green houses, or energy recovery ventilation just to name a few items. The only options available to the home owner involve a lot of techinical research and computing. Imagine your local heating, ventilation, air conditioning person going through all of the effort required when it is easier to make a sale based on rules-of- thumb, which by the way typically overheat and overcool your home.

Looking at the software programs available on-line that are based on Manual J, I discovered that the built-in thermal values cannot be changed and there are set system standards in order to keep the price for a one time user low (unless you want to spend over $1,000.00 and spend time learning to manage the calculations.) So if a homeowner wants to figure the size of the heating and cooling unit so that it is not oversized, the options are really limited. You might try using one of these programs or hire an engineer (since few of the HVAC guys actually know how to figure the perfect balance). Usually, what happens is a unit is installed that is oversized (and, therefore, inefficient or does not remove enough humidity from the air making you uncomfortable).

While trying to get an accurate figure with a passive solar or highly insulated home, your best bet is to purchase the Residential Manual J latest edition (It can cost around $140.00) and self-study or take a course at a local community college. Your other option may be to pay a professional HVAC engineer or a HERS (Home Energy Rating Sytem) engineer capable of expanding on those Manual J calculations.