Originally Posted by mijotter
Thanks for the link Big. So i just spent the last hour talking to my wife about everything we talked about last night J. She thinks getting a minisplit is an unnecessary expense. The room is already hooked up to the furnace with 2 supplies and 1 return. The room gets warm or cold quickly and i'm thinking will hold that temp fairly easily with it being so well insulated. She was thinking running the deadvent return and just have one supply that is hooked to the furnace and control the temp/airflow through the vent inself whether opening it all the way or closing it slightly. Was thinking of maybe putting a relay on the deadvent fan to always kick on when the furnace does, that way it's not constantly sucking air out of the room even if the supply isn't on.
I have a fairly modest budget and am still saving for a nice panasonic projector so multi zoning is out of the question, and those minisplits are a littler higher than I would like.
Does this seem like it would work? I'd say 80% of the time it'll just be her and I down there. Any critiques or tips would be most helpful thanks.
When you say the room is hooked up to the furnace with 2 supplies and 1 return... is that in addition to another return on the floor? The answer leads to 2 possibilities:
1) If you essentially have 2 parallel loops - supply & return for the theater, and supply & return for the rest of the floor... you're in pretty good shape. I would be inclined to just see how it goes. Air the furnace pulls in from the room will mix with the air pulled from the other return and you'll get "fresh" air, same as dead vent. Zoning a system like that should be relatively inexpensive. When you check prices, explain that you already have dedicated supply & return ducts run to the room and are just looking to make it a separate zone. I don't see a dead vent really buying you anything. A mini-split would be overkill.
2) If the only
return for the floor happens to be in the theater room, then things are more complicated. That would mean the 2 supplies
in your theater plus all the other supplies
on the floor were intended to return
through the theater room. In that case, at a minimum you'll want to put in a 1 way passive dead vent that will allow the other rooms to pass their air into the theater so it can be returned properly. If you don't, and your theater is sealed, you'll starve the furnace of return air. In turn it won't be able to supply as much. When you're cooling and have less than the designed airflow there is actually risk of the condensation removed from the air freezing on the coils. The ice blocks more air further compounding the airflow problem. It creates a vicious cycle, performance plummets, and there is risk of damaging the equipment (or having the unit shut itself down to prevent damage). So put a dead vent in and see how it goes. In this case, though, zoning is not as easy because they would have to run additional ducts (to create 2 parallel loops). Depending on your house layout it could range from more expensive to cost prohibitive. A minisplit could help if you placed it opposite the return, but that conditioned air would still make it back to the furnace return. Not a big deal unless the mini-split is trying to cool the room while furnace is set to heat (it would just be really inefficient).
For my room I considered putting a mini-split in a dead vent. That way I could control the temperature of the air coming into the room and control it locally. I decided against all the complication and just went with a conventional forced air heat pump with 2 loops - 1 for theater, 1 for the rest of the basement. I also have an ERV which I agree isn't necessary, but a nice to have in new houses that are tightly sealed. I'm going to see how it goes. My 2nd floor is zoned with the master suite on it's own zone. If I need to put the theater on its own zone, I will, but the HVAC contractor thought it was overkill.Edit: not saying those are the only 2 possibilities. For example, you might have 1 furnace for the entire house. But I don't feel like going through every possible permutation, so just assumed the 2 most likely cases.