HVAC Design Dilemma - long read but perhaps an interesting challenge - Boston Area
I was wondering if you’d offer me some help/advice.
I’ve had 3 different licensed HVAC pros to the house and can’t get a consensus on the best setup. I need to make a decision real soon so I don’t delay construction progress.
We are putting an addition on the house. The existing house is a 30x36 2 floor traditional saltbox built in the 1950’s. The house sits on a full basement. The existing heat is oil furnace hot air. One zone. Separate oil fired hot water heater. The furnace and HWH are about 6 years old and work great. No AC.
Attached to the existing house on its own foundation is an older one floor 16x36 in-law apartment addition with a 4’ crawl space below. The heat is HWBB. There is a full bath and mini kitchen as well as a small den and bedroom in the in-law. The in-law received its hot water and domestic HW from an oil fired boiler that was installed in the (old, now gone) garage. It was an older setup, but worked fine.
The addition we built tore down the old garage and put in a new 32x36 garage in its place with unfinished space above. Connecting the new garage to the existing house is two story new space appx 26x32 that has a large family room on the first floor and 2 bedrooms 2 baths on the second floor.
Option 1 is to leave the existing house as is and plumb a new direct vent oil boiler in the garage. That boiler would service the in law on one HWBB zone, the new family room with HWBB on zone 2, the bedrooms, etc on the second floor with zone 3. This is the least expensive heating setup but has two drawbacks. First, I’d need to install an expensive independent AC system to cool all the new space. Second, I really want ducting instead of HWBB (I know HWBB and a separate AC system are the most efficient - but they are also the most expensive). I want ducting because of the clean look, ease of furniture placement and rapid warming feel. Plus my boys seem to target the baseboards for dents and destruction… Especially in the bathrooms by the toilet!!
Option 2 is to leave the existing house as is and plumb a new direct vent oil boiler in the garage. That boiler would send hot water to the HWBB in the in-law and hot water to a new hydro-aire handler unit with AC in the addition’s attic. New ducting would be run in all the new space and the hydro-aire handler would heat and cool all the new areas (would not cool in-law as there would be no new duct work).
As good as that sounds, I would have a boiler in the garage which isn’t optimal (but I would get some free garage heat from the hot boiler).
Option 3 would be to put a properly sized natural vent boiler in the existing house basement. This means I’d have to remove a perfectly functioning furnace. From the existing basement new boiler, we would run a hot water pipe to the Hydro-Aire handler in the new addition attic and another hot water pipe to the HWBB in the in-law. Problem solved in those areas.
The existing house would need another hydro-aire handler installed in the basement. Connected to the existing duct work and replacing the existing furnace. No problem there except for cost. The real issue is that all the HVAC pros concurred that adding an AC coil to the handler in the basement would probably work only OK for cooling the first floor, but the second floor would likely not get enough AC air as the returns in the existing duct work are insufficient to allow the cold air all the way up.
Of course the easy solution would be to not add the AC coil to the existing house’s new Hydro-Aire handler and put in a separate stand alone AC system. Problem is, this set-up is huge $$$.
So, can any gurus here offer some advice or direction as to how to heat and AC the existing house, the in-law and the new addition in a well integrated manner that doesn’t require an organ donation?
Thanks for reading, I really appreciate any advice!!!!
option number 3 and add a couple minisplit heat pumps to assist in cooling the upstairs area. This is going to be a huge investment but i think it will benefit you the most. HWBB or radiant flooring is absolutely the best way to heat a house imo but you would still need ducting for ac so you may as well use HW coils in the air handlers for heat instead of installing radiators where needed in the existing house. Propane would probably be cheaper to operate than fuel oil if natural gas is not available. or heat pumps and get rid of oil/gas
Develop a full Life Cycle Cost analysis including the use of Heat Pump versus Oil.
Oil is likely upto 3X the operating cost of modern high-efficiency heat pumps.
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
Thanks guys, I have a pro coming over soon that I found on this forum. I appreciate you taking the time to help!