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A GreenBuildingAdvisor forum poster planning an 1,120-square-foot North Texas granny flat argues that four single-zone mini-splits may suit the building better than a central ducted system. The post describes the builder’s reasoning and estimated equipment costs, but it is an individual’s plan and opinion, not a documented comparison or confirmed installation.
A builder planning an 1,120-square-foot granny flat in North Texas says they are leaning toward four single-zone mini-split heat pumps rather than the central ducted system recommended by others, raising questions about how HVAC design should fit a small, high-performance home. The GreenBuildingAdvisor forum post presents the builder’s arguments and preliminary cost estimates; it does not report a completed installation or measured comparison of the systems.
The planned home has two bedrooms and an 800-square-foot conditioned attic, according to the poster. They estimate a heating load of about 21,000 Btu on the coldest design day. The proposed layout uses one mini-split for each bedroom, one for the living room and kitchen, and one for the attic. The poster says they are considering four 9,000-Btu units, while 6,000-Btu models are also available.
The poster gives an estimated price of about $500 each for the 9,000-Btu units and says 6,000-Btu units start at $1,400, but the post does not specify whether those figures include installation or provide comparable, itemized quotes. The builder says other people in a separate group opposed the four-unit plan and favored a central system. Those comments are reported by the poster; the source does not identify the other participants or document their technical assessments.
The builder’s case centers on room-by-room temperature control, avoiding duct losses, and retaining some heating or cooling if one unit fails. They also question whether a central system would solve humidity concerns, saying they have seen high-performance homes in the climate zone install whole-house dehumidifiers. These are the poster’s observations and arguments, not independently verified findings about the proposed building or either system.
How System Choice Affects Comfort
The decision matters because HVAC capacity, distribution and controls shape comfort, energy use and upfront cost over the life of a home. A central system can distribute conditioned air through ducts, while multiple single-zone units allow separate settings in different spaces. Which arrangement performs better depends on the building’s loads, layout, equipment capacity, installation and how occupants use the rooms.
The poster highlights a practical issue for this floor plan: a sunny, south-facing living area may warm differently from north-facing bedrooms. A single thermostat may not reflect every room’s conditions, while separate units can provide more localized control. That does not establish that four systems will be cheaper or more efficient overall. Equipment, installation, maintenance, ventilation and humidity control all affect the comparison.
The post also raises resilience and maintenance concerns. Multiple units could leave some conditioning available if one fails, while ductless indoor units still require cleaning and upkeep. The source offers no reliability data, operating-cost estimates or indoor-air measurements, so readers should treat these points as questions for design review rather than proof that one system is superior.
mini split ductless air conditioner
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The Proposed Four-Unit Layout
The source is a GreenBuildingAdvisor question-and-answer forum post, not a published field study, contractor report or announcement of a finished project. The author is planning a small dwelling and describes why advice favoring a central unit has not persuaded them. The post does not give a construction schedule, final equipment selection or confirmation that the proposed design has been approved.
In addition to temperature control, the author asks about humidity, short cycling, filtration and duct cleanliness. They propose using an energy-recovery ventilator, or ERV, for outdoor-air exchange and filtration, citing a target of 0.35 air changes per hour. The source does not provide a ventilation design, filtration specification, humidity calculations or an expert assessment of whether that rate is appropriate for this home.
The poster also questions where a central thermostat should go in a home with passive solar gains, and argues that ducts can lose efficiency and accumulate debris. These concerns are relevant to the project’s design, but the post does not quantify duct losses or compare cleaning requirements. Its central point is a request to weigh system trade-offs for this particular layout, rather than evidence that ducted HVAC is unsuitable in general.
“I’m more convinced than ever that DUCTED hvac is not the way.”
— The homeowner planning the granny flat, in a GreenBuildingAdvisor forum post
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Costs and Performance Still Unverified
The forum post does not establish whether the four-mini-split proposal has been installed, what the final equipment capacities will be, or whether a qualified HVAC designer has reviewed the load calculations. The stated 21,000-Btu heating load is the homeowner’s estimate; the source supplies no calculation method or independent verification.
It is also unclear what the quoted equipment prices cover, how they compare with a complete ducted-system bid, or what the expected energy bills would be. The post does not provide cooling-load estimates, humidity data, equipment efficiency ratings, duct layout, ventilation plans or results from a short-cycling analysis. No response from a contractor, engineer or other expert is included, and the comments favoring a central system are not described in enough detail to evaluate their reasoning.
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Design Review Before Installation
The source does not announce a decision or a next construction milestone. The homeowner’s next step, if the project proceeds, is not stated. A meaningful comparison would require a room-by-room load assessment, equipment selection matched to those loads, and itemized installed-cost estimates for both options. The design would also need to address ventilation, humidity management, filtration, thermostat placement and maintenance.
Until those details are available, the post records a homeowner’s preference and the questions driving it—not a verified verdict on ducted or ductless HVAC. Any later report of the chosen system, installation costs or measured performance could clarify how the proposal works in practice.
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Key Questions
What HVAC system is the homeowner considering?
The poster is considering four single-zone mini-splits: one for each bedroom, one for the living room and kitchen, and one for the conditioned attic. The post does not confirm that the equipment has been purchased or installed.
Why does the poster question a central ducted system?
The homeowner cites separate room controls, possible duct efficiency losses, thermostat placement, maintenance and backup conditioning if one unit fails. These are the poster’s arguments, not independently established performance findings.
Are the equipment prices a confirmed installed-cost comparison?
No. The post gives estimated prices of about $500 per 9,000-Btu unit and says 6,000-Btu models start at $1,400, but it does not clarify what is included or provide matching installed quotes for a central system.
Has the four-mini-split design been shown to work better?
The source provides no installation results, energy-use data, humidity measurements or side-by-side comparison. It records a proposed design and the homeowner’s reasoning, so relative performance remains unknown.
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