Looking for ways to heat a basement remodel. Sq Ft = 700. Have been looking at the Mr Slim. HVAC contractor came by and advised to tap off existing forced hot air system with a couple of ducts to save money. He says if that method dosen’t work than a Mr Slim type of heat could be installed.
I think this method may rob the second floor of heat during the cold winter in NE. Any thoughts or suggestions would be helpful.
If tapping off the main plenum method is supported, what would by the best way to run the ducts?
Thanks
Replies
Well, a step up would be to perform a room-by-room heat loss calc for the house and determine whether the existing system can serve the added area. Your HVAC guy is probably eyeballing the equipment and making an educated guess that it's big enough.
lose heat
No, if your hvac installer does the duct's s/he'll size and restrict them so that you don't get massive amounts of hot air in the basement (presumably quite close to the furnace) at the expense of the far away ducts feeding the 2nd floor.
Besides, the warm air from your basement will tend to make its way up to the 2nd floor through convection anyway, so unless you have a doorway blocking off the finished basement from the rest of the house you'll need quite a lot of heat to that area to keep it warm.
j
It all depends on the size of your heating system. If it's barely adequate for the existing load, then the added load will probably be a killer. But most heating systems are oversized by 20-30% and have plenty of extra to handle the relatively small load of a basement room (where most of the heat will rise into the rest of the structure anyway).
You might want to consider getting the system "zoned" (with electrically controlled damper valves in the ductwork) so that the three floors can have three separate thermostats. Will make for better comfort all around.
In recent years, I have begun to have serious doubts about zoned systems.
They used to sound good to me because of the obvious incompatibility of spaces like basement vs 2nd floor, etc. But, with a single furnace and cooling coil, it means that the entire airflow would, at times, be forced into a portion of the duct system that was never meant to handle the entire airflow.
There should be a bypass damper(s) instlalled, of course, but the bypassed air will not have significantly changed temperature, so it could possibly result in overheating the furnace's heat exchanger, or, in the cooling mode, inadequately unloading the coil, resulting in superheat problems.
Any thoughts, Dan? (Or anyone that has long-term experience with zoned sytems.)
I know they work to improve comfort, but my question is mainly in regard to how they might affect longevity of the equipment.
HVAC zoning
That is a dam# good question. I have often wondered about that, but figured they knew what they were talking about and/or doing. I liked the idea and it always made sense. I could see, especially in a heating and cooling system where the needs could change seasonally. Where the demand/need actually reversed say in a two story house from upstairs to downstairs and vica versa.
I sometimes feel that it is used in lieu of proper design and duct siziing though.
Maybe there are some HVAC contractors/engineers still looking in on this site. Most of the old hands seem to have sadly abondoned this sinking ship "FHB Breaktime".
Well, I'm very happy with our zoned system, but it's only two zones, and it's on a staged system.
I figure with more than 3 zones (or even 2-3 if they're not reasonably well balanced) you should have a "smart" system that would run at lower speed (and lower BTUs) when only one zone is calling for heat. Pretty sure there are systems like that, though I can't point to one.