The Number Crunch

Well, I have finished my first round of Residential Manual J calculations for Heat Gain and Heat loss. It really isn't too difficult of a task if you are willing to learn and read between the lines. One good thing is that once you have all of your data together (areas, volumes, infiltration factors, thermal values, thermal coefficients, shading coefficients, etc, etc.) it is easier to perform several calculations for different design scenarios expeditiously. What I discovered is that the scenarios I thought would work better did not provide the better results. Small changes to the construction systems could yield improved performance for the HVAC (Heating Venting Air Conditioning) system.

The HVAC system we are planning to use is a two stage high performance heat pump with an ERV (energy recovery ventilator) and a HEPA filter. The house will be broken into two zones one for the grade level and the other for the lower level which yields side hill exposures. The attic will be insulated at the roof deck and unvented. We are in a moderate hot humid location. This means that the heating and cooling requirements are about equal. In our current home, which is much larger, we used a geothermal system for heating and cooling and the performance has been phenomenal. The renovation is located on a smaller site and the floor plan is about 1/2 the size. The return on investment for geothermal would be much longer and an overkill on our renovation.

So far, our work is paying off. We recycled the existing 3 ton single stage heat pump and based on the calculations installing no more then a high performance 2 ton heat pump. This calculation includes adding about twice as much glass as the old house had to increase daylight conditions and improvements to the thermal envelope through out.

The photograph is a picture of David Williamson and Jonathon (?) . David and Jonathon were two HVAC students at Asheville Buncombe Community College who began their own company, Asheville Heat Pump Service. In the photograph, they are in the process of removing the 3 ton unit. David was great because he also helped to find another home for the unit. We remain optimistic about our final results.