Hello professional HVAC installers!
I live in a smallish duplex (just under 1300 sq ft) built in 1910, with radiator heat, no cooling. Original plaster walls, original windows with low-E storms in most rooms (and old storms in one room).
I live in climate zone 4a, normal highs are 87 to 89 June 24-Aug. 18; normal lows around 70/71 same period; average dew point 67-68 in July & August.
Even with this climate, we have avoided air conditioning 97% of the time our first two summers in the house! But we are thinking of installing minisplits for our upstairs and continuing to live with box fans and ceiling fans in the downstairs rooms.
I am a regular over on Greenbuildingadvisor.com, and have heard there that Daikin Quaternity is the best for dehumidification, which is our biggest concern. We discovered after a freakishly hot day in October that even a high of 95+ does not create uncomfortable sleeping by bedtime when dew points aren't high.
I very much dislike feeling too cold indoors in the summer, and so am a bit concerned that oversizing is going to create a comfort problem.
However, it seems there is no perfect option for our upstairs, since a 9000 btu unit would be plenty to cool the entire upstairs, but there is no good way to place it in a hallway to blow into the three small bedrooms (the hallway wall is not only backed to the staircase to the semi-conditioned attic, but it also is the side of the house that is attached to the other half of the duplex. (I only own my side.)
Coolcalc estimated my cooling load was only 2367 btu for those three rooms.
The master bedroom is 191 sq ft, including the full-wall length closet, 9 foot tall ceilings, three windows of 70 inches by 31 inches.
The second bedroom, which shares a wall with master, is 145 sq ft, with two windows same size as master
Third bedroom, which is used as a home office, is tiny, not even 90 sq ft, with one window 63 inches by 31 inches, but has a door onto the enclosed former sleeping porch, 54 sq ft, which has four modern windows, and no heat.
The three windows in the master are all facing north; the east facing, exterior wall has no windows. The south wall is the interior wall that backs up to the second bedroom.
The second bedroom has an extra deep closet, the rear wall of the closet backs up to the third bedroom wall. The closet is 37 inches wide; the Quaternity unit is 35 inches wide. That closet's east wall is the exterior wall, though the unit would be on the closet's south wall in order to blow into the room (and to be wide enough).
Putting the unit on the regular part of the south wall in the second bedroom is not possible because the chimney is behind it.
Exterior walls have no insulation, and are stucco over frame construction, except for sleeping porch.
So here's my question. Would it be better to put the 9,000 btu Daikin Quaternity on the internal wall between the two normal sized bedrooms, with a super short duct run? We are licensed foster parents, so room to room noise transmission could be a problem when we have kids sleeping in that second bedroom? Cooling is required in that bedroom per agency.
If that was the solution, we could have a Midea inverter a/c in the sleeping porch to serve both it and the home office, if needed. Or just leave the GE a/c if there's not enough energy savings to warrant the upgrade.
Or would it be better to put a Daikin Q. in the closet to serve the middle and small bedroom, again with short duct run? There are no noise issues there, because the third bedroom is not used as a bedroom.
In that case, we'd also have 9,000 BTU unit on the external wall of the master bedroom, which I'm sure would make installation simpler/cheaper.
Attic is sort of conditioned, but no return register. We installed flash and batt insulation along the roof line (2 inches closed cell foam covered by R23 rockwool; one inch of closed cell foam on the eave walls, with drywall over those walls. It's a walk-up attic with full flooring, and so I'm not sure how one could do a multisplit arrangement with ducts up there? Since the installation of the insulation, the attic only runs a few degrees hotter than the second floor, I think, with no cooling either place... but given the top floor is often in the mid-80s in the two hottest months, it's not exactly cool up there.
Sorry for the very long, detailed post, but I wanted y'all to have all the information I could so you could give the best advice!
I live in a smallish duplex (just under 1300 sq ft) built in 1910, with radiator heat, no cooling. Original plaster walls, original windows with low-E storms in most rooms (and old storms in one room).
I live in climate zone 4a, normal highs are 87 to 89 June 24-Aug. 18; normal lows around 70/71 same period; average dew point 67-68 in July & August.
Even with this climate, we have avoided air conditioning 97% of the time our first two summers in the house! But we are thinking of installing minisplits for our upstairs and continuing to live with box fans and ceiling fans in the downstairs rooms.
I am a regular over on Greenbuildingadvisor.com, and have heard there that Daikin Quaternity is the best for dehumidification, which is our biggest concern. We discovered after a freakishly hot day in October that even a high of 95+ does not create uncomfortable sleeping by bedtime when dew points aren't high.
I very much dislike feeling too cold indoors in the summer, and so am a bit concerned that oversizing is going to create a comfort problem.
However, it seems there is no perfect option for our upstairs, since a 9000 btu unit would be plenty to cool the entire upstairs, but there is no good way to place it in a hallway to blow into the three small bedrooms (the hallway wall is not only backed to the staircase to the semi-conditioned attic, but it also is the side of the house that is attached to the other half of the duplex. (I only own my side.)
Coolcalc estimated my cooling load was only 2367 btu for those three rooms.
The master bedroom is 191 sq ft, including the full-wall length closet, 9 foot tall ceilings, three windows of 70 inches by 31 inches.
The second bedroom, which shares a wall with master, is 145 sq ft, with two windows same size as master
Third bedroom, which is used as a home office, is tiny, not even 90 sq ft, with one window 63 inches by 31 inches, but has a door onto the enclosed former sleeping porch, 54 sq ft, which has four modern windows, and no heat.
The three windows in the master are all facing north; the east facing, exterior wall has no windows. The south wall is the interior wall that backs up to the second bedroom.
The second bedroom has an extra deep closet, the rear wall of the closet backs up to the third bedroom wall. The closet is 37 inches wide; the Quaternity unit is 35 inches wide. That closet's east wall is the exterior wall, though the unit would be on the closet's south wall in order to blow into the room (and to be wide enough).
Putting the unit on the regular part of the south wall in the second bedroom is not possible because the chimney is behind it.
Exterior walls have no insulation, and are stucco over frame construction, except for sleeping porch.
So here's my question. Would it be better to put the 9,000 btu Daikin Quaternity on the internal wall between the two normal sized bedrooms, with a super short duct run? We are licensed foster parents, so room to room noise transmission could be a problem when we have kids sleeping in that second bedroom? Cooling is required in that bedroom per agency.
If that was the solution, we could have a Midea inverter a/c in the sleeping porch to serve both it and the home office, if needed. Or just leave the GE a/c if there's not enough energy savings to warrant the upgrade.
Or would it be better to put a Daikin Q. in the closet to serve the middle and small bedroom, again with short duct run? There are no noise issues there, because the third bedroom is not used as a bedroom.
In that case, we'd also have 9,000 BTU unit on the external wall of the master bedroom, which I'm sure would make installation simpler/cheaper.
Attic is sort of conditioned, but no return register. We installed flash and batt insulation along the roof line (2 inches closed cell foam covered by R23 rockwool; one inch of closed cell foam on the eave walls, with drywall over those walls. It's a walk-up attic with full flooring, and so I'm not sure how one could do a multisplit arrangement with ducts up there? Since the installation of the insulation, the attic only runs a few degrees hotter than the second floor, I think, with no cooling either place... but given the top floor is often in the mid-80s in the two hottest months, it's not exactly cool up there.
Sorry for the very long, detailed post, but I wanted y'all to have all the information I could so you could give the best advice!
source https://hvac-talk.com/vbb/showthread.php?2226251-Cooling-small-bedrooms-with-minisplits&goto=newpost
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