Question from energy homeowner:
Contractor has recommended installing a two stage Water Furnace Envision w/desup NDV049A system into a 2700 square foot cape cod, 1000 square feet basement, 1000 square feet first floor, and a 700 square foot second floor. The house is all brick and was built in 1950, walls and attics are currently insulated using r 11. The blower door test gave a 2800 cfm reading at 50.
Contractor is recommending a 4 ton geothermal system, According to his comments it is a two stage system that will run at 60% capacity at the first stage and 100% at the second stage. Contractor feels the 4 ton system will provide more heat using the geothermal without going to the back up heat.,
If the system is over-sized to accommodate the heating season, does this make sense.? He says with a two stage system it does. Will the system operate efficiently. If we were installing a regular electric heat pump the manual J test called for a 3 ton system (single stage) Is the contractor correct in over-sizing the unit to provide more geothermal heat in the winter months?
One other question: What is the advantage of using galvanized ducts as compared to 1 inch rigid fiberboard ducts?
Thank you for responses
If the contractor doesn't calculate a manual J,D, and S worksheet for the house then he's merely guessing. Also, galvanized ducting last much longer, is easier to clean, and is more rigid that fiberboard.