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A homeowner building a 1,120-square-foot granny flat in North Texas says they are reconsidering advice to install central ducted HVAC and are planning four single-zone mini-splits. The post outlines concerns about zoning, duct losses and backup during equipment failures, but does not provide test results or a completed system comparison.
A homeowner planning an 1,120-square-foot granny flat in North Texas is defending a proposed system of four single-zone mini-splits over a central ducted HVAC system, reopening a practical design debate for small, energy-efficient homes. The GreenBuildingAdvisor post reports the owner’s plans and concerns, but offers no independent performance data or confirmed final installation.
The planned building has two bedrooms and an 800-square-foot conditioned attic, according to the post. Its stated heating load is about 21,000 Btu on the coldest design day. The owner proposes one mini-split for each bedroom, one for the living room and kitchen, and one for the attic. They say they are considering four 9,000-Btu units, which they estimate could be bought and installed for about $500 each; the post says available 6,000-Btu units start at $1,400. It does not specify the basis for those prices or provide installation bids.
The homeowner says other participants in a separate discussion opposed the four-unit plan and favored a central system. In response, the owner argues that separate indoor units could let occupants condition bedrooms without cooling the entire home to the same temperature. They also suggest that when one mini-split might short-cycle under mild conditions, one or two units could provide cooling across more of the house. That is the homeowner’s reasoning, not a measured result for this building.
Other concerns raised include duct heat loss, thermostat placement where south-facing living areas receive winter sun, and the future cleaning or replacement of ductwork. The owner also points to redundancy: if one mini-split fails, the remaining units may still provide some heating or cooling. The post says the planned ventilation system is an ERV, or energy-recovery ventilator, intended to exchange air at a stated rate of 0.35 air changes per hour and provide filtration. No equipment specifications, design calculations, or filtration test results are included.
How System Choice Shapes Comfort
The choice affects more than equipment preference. A central system and several mini-splits distribute heating and cooling differently, influencing room-by-room comfort, controls and service needs. In a home with separate bedrooms, an attic and rooms with different sun exposure, the ability to set zones independently may appeal to occupants who do not want every space at the same temperature.
But the post does not establish that the proposed mini-splits would cost less over their life or work better than a properly designed ducted system. Equipment sizing, installation quality, the units’ operating range and how air moves between rooms all matter. A system with several indoor units can also involve more equipment and controls to maintain. The discussion matters to homeowners because broad claims that one system type is always superior can obscure the building-specific trade-offs that need to be checked before installation.
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The Design Questions Behind the Debate
The homeowner’s case is framed around a small, high-performance house with a relatively low stated heating load. The post questions common arguments for ducted HVAC, including humidity control, filtration and avoiding short cycling. It asks why some high-performance homes using central ducted systems also install whole-house dehumidifiers, but gives no examples or measurements to test that comparison.
The owner also raises a passive-solar design concern: south-facing living areas may warm in winter sun while north-facing bedrooms remain cooler. A single thermostat could respond to conditions in one location that do not match the rest of the home. The proposed ERV is intended to handle ventilation and filtration, though the post does not explain how its filtration would compare with a particular HVAC filter. These are questions to resolve through a system design for the actual building, rather than conclusions established by the post.
“I’m more convinced than ever that DUCTED hvac is not the way.”
— The homeowner, in the GreenBuildingAdvisor post
Costs and Performance Still Unverified
The post does not say whether the owner has finalized the design, received contractor quotes or installed any equipment. The stated $500-per-unit figure is not broken down, and it is unclear whether it includes all equipment, labor, electrical work and other project costs. The source also does not identify the exact models, their capacities under North Texas conditions, or whether four 9,000-Btu units are appropriately sized for the building.
No cooling load, humidity measurements, energy-use estimates or side-by-side comparison with a ducted system are supplied. The effectiveness of the ERV’s proposed filtration, the risk of short cycling, and the expected duct losses are also not quantified. The heating-load figure alone cannot settle those questions, and the claims in the post should be read as concerns and expectations, not verified outcomes.
A Final Design Needs Site Data
The next step described by the post is the homeowner’s ongoing system selection; it gives no installation date or follow-up results. A meaningful comparison would require finalized heating and cooling load calculations, equipment performance data, a complete installed-cost estimate and a plan for ventilation, humidity control and room-to-room air movement. The owner has not reported whether a designer or contractor has reviewed the proposed layout.
If the system is installed, later information on comfort, humidity, energy use, maintenance and reliability could show how the plan performs in practice. Until then, the post records a homeowner’s reasons for preferring multiple mini-splits, not evidence that ducted HVAC is unsuitable for similar homes.
Key Questions
What HVAC system is the homeowner proposing?
The post describes four single-zone mini-splits: one for each bedroom, one for the living room and kitchen, and one for the conditioned attic. The owner says the system is planned, not that it has been installed.
Why does the homeowner prefer mini-splits?
The owner cites independent room temperatures, potential operation of only some units in mild conditions, avoiding duct losses and having other units available if one fails. These are the homeowner’s arguments; the post provides no measured comparison.
Is the stated price confirmed as the full installation cost?
No. The post gives an estimate of about $500 to buy and install each 9,000-Btu unit, but does not explain what the estimate includes or provide contractor bids.
Does the post show that ducted HVAC performs worse?
No. It raises questions about duct losses, humidity, filtration and thermostat placement, but includes no test results or energy data establishing that the proposed mini-splits would perform better in this home.
Source: rss
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