Posts tagged needs

Question : HVAC needs for a home addition?
Ugh. Getting ready to add a level to our Central NJ home and having trouble getting a handle on my HVAC needs. Went to a home show this weekend, and no two answers were the same. We have a 1300 sqft ranch, with 800 sqft finished basement. We are adding 1000 sqft of bedrooms and baths on top. I’m looking to make sure things are tight, efficient and green as much as I can, but heard everything from dual units, to two stage high efficiency, etc. I’d really like to replace the 75000 btu 80% Ruud furnace with a single unit to heat the zones separately. I did this once before with my last house in Akron, OH and was really pleased with the results. Thoughts are appreciated, but proper formulas for size and such would be awesome. Thanks so much.
home staging nj

Best answer:

Answer by Breath on the wind
I am just reviewing the heat gain/loss calculations myself. The problem is that you don’t say what you have and adding an addition “green” usually has nothing to do with heat loss or gain.

Old calculations just added up windows and so much for wall and attic insulation and that’s it. Newer ones will take into consideration the items in the house that produce heat as a bi product and in larger commercial buildings the heat produced by people in the building.

The problem is that standard heating plants are put into non standard buildings. Design is one of the cheapest phases in construction. I would not build an addition today without taking into consideration and optimizing solar gain. Often this means far more south facing windows than on any other side of the building. A well designed building or addition will have minimal heating requirements.

On the other hand, with some familiarity I can say, the typical Central Jersey (Mercer County?) development homes were not known for their efficiently planned or executed structures. The winding streets of the typical development had more to do with frontage requirements than south facing windows. You speak much of square foot area but little of current heating satisfaction, planned R values, any retro upgrade to the existing structure and current heating problems. These are all important for determining heat loss calculations. The only thing you can do with square foot areas is use “rules of thumb” and guesswork. You need R values for the final product and surfaces exposed to the outside at a minimum. The type and direction of glazing is also significant.

Even double glazed Windows on non southern exposures are a heating disaster with an R value of less than 4. Insulating shutters can up this value to very close to standard walls. But if you are very concerned you will be looking at some sort of SIP construction or 2×6″ walls with an R value closer to 19 and attic insulation closer to 30.

A single unit vers two units for two zones often comes down to a question of ductwork. It is easier to balance a system with two units as the unit for the upstairs can be above and pushing air down to the space below ductwork runs are short (i.e. cheaper.) A single unit in the basement will have to have ductwork going up two floors. Longer runs mean more heat loss and greater static pressure. Additionally, zoning a forced hot air system requires a separate module and automatic zoning dampers. The unit must react if either zone demands heat. This is a level of complexity that not every hvac tech is immediately familiar with. Service will be more problematic with a duel zone forced hot air system than with two separate units.

Was your former home similar in design to the existing one?