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Question DetailsAsked on 12/29/2017

Is it possible to add a thermostat for a separate room in my upstairs zone? average cost?

My Family Room over the garage is always cold in winter and hot in summer. Is it possible to add a thermostat/zone for just that room? The room has 2 ducts and its own return. My house has dual zones already. One upstairs and one down stairs.

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Sounds like a tuck-under garage - so I am going to discuss this assuming upstairs is part of the second floor zone. (Makes no functional difference - adjust your thinking if I am wrong about this and garage is an underground garage under first floor, for instance.)

0) totally easiest solution in some cases, if viable for your life - regulate the 'sharing" or heat and cold with the rest of the upstairs by opening the door to the family room all the way, if currently commonly closed - so more upstairs air goes in there through the door. Incoming vent airflow to that room might have to be reduced somewhat if the airflow is out of the room rather than into it when door is open. This sounds counterintuitive - that shutting off some of the incoming flow to the room could heat or cool it better, but the reason is by stealing air from the upstairs to heat it, that keeps the upstairs from reaching shutdown temp as quickly, so the family room would get more overhall heating/cooling duration. Might be worth trying to see if ti works for you.

1) Next simplest solution, but primarily IF the family room problem is related to slow heating and cooling, NOT altogether too hot or cold at all times. But can result in more heat/cooling in the family room WHEN the central air system is running - will NOT cause the system to kick on when it gets too cold or hot - just causes more heat/cold air to go there WHEN the upstairs thermostat is calling for heat or cooling. Will cause slower heating/ cooling in the rest of the upstairs because you are basically "stealing" more of the airflow for that room. Anyway, this soluytion is adjusting (or installing adjustable ones, if rigid vents now) incoming vents in the other upstairs rooms so more of the air goes to the family room and less to the rest of the upstairs. Because that room is being underserved now, changing the incoming air vents (unless restrictive ones so less restrictive ones would let more air in) would not increase airflow, so putting adjustable vent on some or all the incoming vents elsewhere upstairs, to cut down the airflow to those competing areas, would be the solution so more airflow goes to the family room. Might only need it on one room, maybe more - but this WILL, because the family room will be soaking up more of the heat/ cooling, cause the overall cycle duration upstairs to lengthen some - i.e. will take more time for the upstairs thermostat to reach the desired temp and shut the system down. May be only a minute or so difference, but with large family rooms with poor insulation can lengthen the response several minutes.

2) If the problem is constantly too hot/cold depending on season, might be moving the upstairs thermostat to a location in or nearer to the family room so the temp there has more control over the upstairs turn on/off temp. This is commonly cheaper than putting in dampers and certainly cheaper than new duct runs. If you do that, be sure to have him leave the old wires installed and accessible in case you want to move the thermostat back later - putting in new wires for the new location (which might tap off the old wires if easiest that way).

3) Harder / more expensive way - yes you can create another zone in the family room if needed, though to truly work as a separate thermostat and dedicated zone the ducting for it would have to run all the way back to the furnace.

4) Another option is to put a thermostatically controlled damper in the duct running to the upstairs, typically at a wye with one part of the wye serving only that room, the rest (main duct branch run presumably) serving the rest of the upstairs. Then the thermostats (calling for heat/cooling or not) control the damper to determine whether the air is going to the main part of the upstairs or the family room. This assumes the family room ducts come off the main trunk before any of the rest of the upstairs for "full control".

5) This can also commonly be done cheaper using a manual damper in the duct at the intersection of the main and family room ducts - manually adjusting how much of the airflow goes to each part of the ducts. For a room generally not getting enough heat/ cooling, the damper would be in the main duct just "after" the branch to the family room, to force more air into that branch - closing the main duct off a bit, which sends less heat / cooling to the rest of the upstairs.

Manual dampers are easily adjustable and easy to put in and need no wiring. The key here is the family room duct is not carrying enough air to keep up with the rest of the upstairs - so either more air has to be forced into there by blocking some of the air to the rest of the upstairs, or by (rarely easy to do) increasing the supply AND return ducts to that room to allow a greater portion of the airflow to go there. Generally, a room imbalance situation like you describe can be solved by manual damper like this, generally (after some trial and error) not needing adjustment again, or sometimes seasonally because furnace and A/C have different BTU capacities.

Using a damper to regulate the airflow would be easiest if the branch to the family room is the first off the main duct - would be essentially ineffective if it is last, in-between if comes off mid-run.

6) if you already have a damper regulating airflow split between upstairs and downstairs (instead of two main ducts feeding directly to them off the blower plenum at the furnace, typically as a split or wye or octopus right "behind" the A/C evaporator coil), messing with the upstairs flow per above may also require adjusting that damper for better upstairs/downstairs temperature matching.

7) Other solutions - insulating that room better, insulating the garage, or making the garage fully part of the central air system - though thatlatter would increase the total heating/cooling load, which your system might not be able to handle without adversely impacting the rest of the house's performance.

If you check wall and ceiling and floor temps in that room versus the rest of the upstairs, you might find out it is not as well insulated (or attic might not be insulated at all) - so if the ceiling is significantly hotter/colder, improving the insulation in the attic might be all it needs - or if unvented, venting the attic roof like (assuming peaked roof) with eave and ridge venting if it does not have it now.

Likewise, though a bit harder to do but can be done with foam-in-place or blown-in insulation without tearing out the garage ceiling drywall, insulating the family room floor (garage ceiling) might help if the overheating/underheating is because the garage underneath is partly or fully outside of the "conditioned space", or maybe has uninsulated walls - in which case if hot/cold garage is the proximate cause of the cold/overhot family room, insulating the walls might be the best solution and would also reduce total energy expended in incidentally heating/ cooling it with heat radiated from the rest of the house.

Heating and A/C would be your Search the List category for a pro if monkeying with vent openings yourself does not do it. When you talk to prospective firms explain you are looking for a tech experienced in balancing or regulating temperature between rooms within a zone. I would expect this to run about $150-250 to diagnose your situation and look at alternatives, additional maybe $250-400 for a damper and individual thermostat installation, and certainly into the $500-1000 range and maybe more if ducting additions or changes are needed.

Answered 2 years ago by LCD

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