Question 1

What is a mechanical plan for an ADU and what does it show?

Accepted Answer

A mechanical plan for an ADU is the permit-ready drawing set that documents the complete HVAC and ventilation design — the equipment, its sizing math, where every component goes, and how the air moves. It gives the plan reviewer everything needed to confirm the system is safe, correctly sized, and code-compliant, and it coordinates cleanly with your Title 24 report.What the drawing set containsA typical ADU mechanical set runs one or two sheets (M-1, M-2) and includes:Mechanical floor plan showing the indoor equipment, supply/return points, exhaust fans, and the outdoor condenser location with required property-line and window setbacks.Equipment schedule — a table listing each unit's manufacturer, model number, capacity in BTU/hr, and efficiency ratings (SEER2/HSPF2 for heat pumps), so the reviewer can verify Title 24 minimums.Heat-load (Manual J) summary establishing the peak heating and cooling loads the equipment is sized to.Mini-split head and condenser layout with refrigerant line-set routing drawn from each indoor head to the outdoor unit.Duct layout where a ducted system is used, including register locations and duct sizing.Ventilation design per ASHRAE 62.2 — the whole-building mechanical ventilation rate and equipment, plus local exhaust (bath fans, kitchen hood ducted to the exterior).Condensate drainage routing for the indoor units.General notes and a title block citing the applicable codes (CMC, CBC, Title 24) and identifying the project.What the plan proves to the reviewerPlan check is really verifying two things: that the system is safe and correctly sized, and that it matches the energy-compliance documents. The Manual J summary and equipment schedule together prove sizing and efficiency; the ventilation design, ducted exhaust, and condenser placement prove the design meets the California Mechanical Code and won't create a nuisance for neighbors. A mechanical plan is sized to your ADU's square footage and climate zone, not pulled from a template — the load calculation drives the equipment selection.What you receive — checklistMechanical floor plan with equipment locations and setbacks.Equipment schedule (make, model, BTU/hr, efficiency).Manual J load-calculation summary.Line-set and/or duct routing.ASHRAE 62.2 whole-building ventilation plus local exhaust.Condensate, general notes, and title block.Sheet counts, local amendments, and submittal requirements vary by jurisdiction — confirm with your local building department. Our mechanical plans start at $995 as a single discipline, scaled by ADU size, and you can pair them with electrical and plumbing in the size-scaled Full MEP package. See pricing or start your order.

Question 2

What HVAC system is most commonly used in California ADUs?

Accepted Answer

The most common HVAC system in California ADUs is the ductless mini-split heat pump — a two-piece system with one or more indoor heads connected by refrigerant lines to an outdoor condensing unit that provides both heating and cooling without any ductwork. It has become the default because it is all-electric, highly efficient, duct-free, and the path of least resistance to Title 24 compliance.Why mini-splits dominate ADU designNo ductwork. ADUs are small and ceiling space is precious. Eliminating ducts saves height, avoids attic-routing headaches, and removes duct leakage — historically one of the largest sources of HVAC energy loss and HERS test failures.All-electric. Mini-splits contain no combustion, so they comply with the all-electric reach codes adopted by Los Angeles, San Jose, San Francisco, Oakland, and dozens of other California cities, and they model favorably under the 2025 energy code.Zoning flexibility. A multi-zone system gives each room independent temperature control, so an occupied bedroom and an empty living room don't have to share a setpoint.High efficiency. Quality mini-splits typically exceed California's minimum SEER2/HSPF2 thresholds by a wide margin, which improves the Title 24 compliance margin.Climate fit. California's largely mild, Mediterranean climate is nearly ideal for heat-pump operation across most of the year.How configurations match the ADUADU typeTypical systemStudio / open-plan under ~600 SFSingle-zone mini-split (one head)1-bedroomTwo-zone mini-split (living + bedroom)2-bedroomThree-zone mini-split, or a ducted heat pump1,000+ SF, multiple roomsMulti-zone mini-split or ducted heat pump with central air handlerThe main alternativeOn larger multi-bedroom ADUs, a ducted heat pump with a central air handler is the principal alternative — same heat-pump technology, but air is distributed through a compact duct network to registers in each room with a single thermostat and no visible heads. It needs room to route ducts and the ducts must meet sealing limits verified by a HERS rater. Gas furnaces, by contrast, heat but don't cool, require a separate AC system for California summers, and are prohibited outright in cities with all-electric reach codes — so they rarely make sense for a new ADU.Code thresholds and local mandates vary by jurisdiction — confirm with your local building department. Our mechanical plans specify the exact system, sized to your ADU and climate zone, with the Manual J and equipment schedule included. See our mechanical guide for deeper detail, or start an order.

Question 3

What is a heat load calculation and why is it required?

Accepted Answer

A heat load calculation — performed using the ACCA Manual J method recognized by California building codes — determines the exact peak heating and cooling loads your ADU experiences at design conditions. It produces the BTU/hr the engineer uses to size the HVAC equipment, replacing guesswork with engineering, and it is increasingly required as part of the plan set itself.What it calculatesA Manual J models how heat enters and leaves the ADU at the worst-case summer and winter conditions for your climate zone, accounting for:Wall, ceiling, and floor areas and their construction.Window area and orientation (north/south/east/west), because solar gain varies dramatically by direction.U-factors — the thermal performance of each assembly and the windows.Air infiltration — how tightly the building is sealed.Internal heat gains from occupants, lighting, and appliances.Outdoor design conditions for the project's California climate zone.Duct location and leakage, for ducted systems.Why correct sizing matters so muchThe instinct to "go bigger to be safe" backfires with HVAC. Oversized equipment short-cycles — turning on and off too frequently — which hurts humidity control, comfort, and compressor life. Undersized equipment can't hold setpoint on the hottest or coldest design days. Manual J finds the right capacity so the system runs efficiently and comfortably.Why it is requiredPlan reviewers increasingly require the actual load calculation, not just an equipment schedule. Without it, the reviewer cannot confirm the system is correctly sized or that the equipment meets Title 24 — so a missing Manual J is one of the most common reasons a plan is kicked back. Including the calculation up front prevents that correction and lets the reviewer approve the equipment selection.Manual J is the engineering behind the equipment on your plans. The climate zone is determined automatically from the project address, and if insulation values are unknown the engineer applies California code-minimum defaults — keeping the calculation defensible while construction details are finalized.What the engineer needs from youA dimensioned floor plan with ceiling heights.A window schedule — size, location, orientation, and glazing type.Wall, ceiling, and floor construction — insulation R-values if known.The ADU type (detached, attached, garage conversion) and the project address.Any unusual conditions — large west-facing glass, vaulted ceilings, exposed floors.Design assumptions and code defaults vary by climate zone and code cycle — confirm specifics with your local building department. Our mechanical plans include the Manual J summary and the matching equipment schedule, so the sizing math travels with the drawings. See how it works, or start your order.

Question 4

Does California require separate mechanical permits for ADUs?

Accepted Answer

An ADU's mechanical work nearly always requires permitting, but whether it is issued as a separate mechanical permit or rolled into the combination building permit depends on your jurisdiction. For a new ADU, the HVAC and ventilation are typically reviewed and inspected under the same combination permit as the building, electrical, and plumbing scopes — but the mechanical scope still has to be shown, plan-checked, and inspected on its own merits.How permitting is usually structuredNew ADU construction: Most California cities issue a single combination building permit that covers building, mechanical, electrical, and plumbing (the "MEP" trades) together. The mechanical plans are part of that submittal and receive their own plan-check review and field inspections.Standalone HVAC work in an existing unit: Replacing or adding HVAC outside of a larger project often pulls a dedicated mechanical permit.Larger or phased projects: Some jurisdictions break the trades into separate trade permits issued to the licensed contractor performing each scope.The practical point is the same in every case: the mechanical design must be documented and approved. A combination permit doesn't reduce what the mechanical plans have to show.What the mechanical review checksRegardless of how the permit is packaged, the reviewer verifies the same items:A Manual J heat load calculation supporting the equipment sizing.A complete equipment schedule (make, model, BTU/hr, efficiency) meeting Title 24 minimums.ASHRAE 62.2 whole-building ventilation, designed and documented separately from heating and cooling.Local exhaust — bath fans and a kitchen hood ducted to the exterior.Outdoor condenser location with property-line and window setbacks.Refrigerant line-set or duct routing shown.Condensate drainage routing.Why it matters who pulls the permitIn many jurisdictions a licensed mechanical (C-20 HVAC) contractor pulls the mechanical permit and is responsible for the installation matching the approved plans. Homeowners acting as owner-builder may pull permits themselves where allowed, but the inspection standard is identical. Either way, the work must be inspected and the permit closed with a passed final — which also matters because most heat pump rebate programs require a closed permit before they release funds.Whether mechanical is a separate permit or part of a combination permit, the mechanical plans still must be complete. Bundling them with a Title 24 report keeps the equipment on the drawings consistent with the energy calcs and avoids the most common mismatch correction.Permit structures, fees, and which trades are combined vary significantly by jurisdiction — confirm the exact requirements with your local building department before you submit. Our mechanical plans are prepared to satisfy mechanical plan check whether issued standalone or as part of a combination permit, and the Full MEP package keeps all three trades coordinated. See how it works or start your order.

Question 5

What are the Title 24 requirements for HVAC in new California ADU construction?

Accepted Answer

Title 24 — California's Building Energy Efficiency Standards — governs the HVAC system in every new ADU. In short, the 2025 energy code treats heat pumps as the prescriptive baseline for space conditioning, sets minimum equipment efficiencies (SEER2/HSPF2), requires continuous whole-building ventilation per ASHRAE 62.2, and mandates field verification by a HERS rater. The mechanical plans must document all of this and match the Title 24 energy report.The core Title 24 HVAC requirementsHeat pump baseline. Under the 2025 code, heat pumps are the prescriptive baseline for new-construction space conditioning. Designing around a mini-split or ducted heat pump is the most direct route to a clean compliance run.Minimum equipment efficiency. The selected equipment must meet or exceed current minimum SEER2 (cooling) and HSPF2 (heating) thresholds. Quality mini-splits typically clear these by a wide margin, improving the compliance cushion.Whole-building ventilation. Continuous mechanical ventilation meeting ASHRAE 62.2, sized to floor area and bedroom count, is required in every new ADU regardless of size — and is not waivable.HERS field verification. A HERS rater field-measures and confirms required items, which commonly include refrigerant charge verification (required in all 16 climate zones), duct leakage for ducted systems, and ventilation airflow.Climate-zone-specific design. California's 16 climate zones — determined by parcel address, not ZIP code — set the outdoor design temperatures and efficiency requirements the equipment must satisfy.How compliance is demonstratedTitle 24 compliance for a new ADU is shown through an energy report (CF1R), and the equipment listed on the mechanical schedule must match the equipment modeled in that report. A mismatch between the drawings and the energy calcs is one of the most common plan-check corrections, so the make, model, and efficiency ratings have to be consistent across both documents.Climate-zone considerationsZone groupDesign emphasisCoastal & inland (1, 3, 5–13)Standard high-efficiency heat pumps perform excellentlyDesert (14, 15)Prioritize cooling capacity; size to high summer design temperaturesMountain (16) and cold edges of 1 and 11Specify a cold-climate-rated heat pump that holds capacity below freezingCompliance checklistConfirm the climate zone by parcel address.Run a Manual J for peak heating and cooling loads.Select heat-pump equipment meeting current SEER2/HSPF2 minimums.Design ASHRAE 62.2 whole-building ventilation as a separate system.Note HERS verification (refrigerant charge always; duct leakage if ducted; ventilation airflow).Keep the mechanical schedule consistent with the Title 24 energy report.Code thresholds and verification requirements change between code cycles and vary by jurisdiction — confirm current details with your local building department. Our mechanical plans are prepared to your climate zone, and a bundled Title 24 report (+$240) ties equipment selection to compliance in one coordinated pass. Start your order when ready.

Question 6

Can multiple mini-split heads share one outdoor unit?

Accepted Answer

Yes. A multi-zone mini-split connects one outdoor condensing unit to two, three, or more indoor heads, each serving a different room with its own temperature control. This is the standard way to condition a multi-room ADU with a single outdoor unit — and the engineer sizes the condenser and each head from per-room load calculations rather than installing identical heads everywhere.Single-zone vs. multi-zoneA single-zone system pairs one outdoor unit with one indoor head — ideal for compact, open-plan studios where air circulates freely. A multi-zone system feeds multiple heads from one condenser, typically with each enclosed bedroom getting its own head so it can hold temperature with the door closed at night. Total capacity is shared across the heads, which is the key design constraint.How head count tracks the floor planA single mini-split head conditions the air in the room it occupies; it cannot effectively push conditioned air around corners, through doorways, or into closed bedrooms. As a practical rule:ConfigurationBest forSingle-zone (1 head)Studios and open-plan ADUs under ~600 SFTwo-zone (2 heads)1-bedroom ADUs with a separate living area and bedroomThree-zone (3 heads)2-bedroom ADUs — one head for living/dining/kitchen, one per bedroomThe engineering that makes it workSharing one condenser is not as simple as wiring up identical heads. Two design rules govern a multi-zone system:Size each head to its zone's load. A south- and west-facing living room with large windows carries a far higher cooling load than a small north-facing bedroom; putting identical heads in both leads to one room that short-cycles and another that struggles.Size the outdoor unit to the combined connected load — not to the sum of nameplate maximums. The condenser's total capacity must cover the heads it serves at design conditions, with refrigerant line-set routing from each head back to the outdoor unit shown on the plans so the reviewer can confirm it is feasible.Multi-zone systems give room-by-room control off a single outdoor unit, which is why they're common in 1- and 2-bedroom ADUs. The trade-off is a visible head in each conditioned room and a higher installed cost than a single-zone system.Multi-zone design checklistCount the separately enclosed habitable rooms — bedrooms each want a zone.Run a per-zone Manual J to establish each room's load.Confirm the chosen outdoor unit's total capacity covers the sum of the connected heads at design conditions.Verify line-set routing from each head to the condenser is feasible and shown.Check that every habitable room receives heat — a California code requirement.System sizing and equipment availability vary by project and brand, and local rules vary by jurisdiction — confirm with your local building department. Our mechanical plans include the zone-by-zone load calculation, the head and condenser schedule, and refrigerant line routing. See pricing or order here.

Question 7

What are the ventilation requirements for a new ADU in California?

Accepted Answer

Every new ADU in California must include a continuous, whole-building mechanical ventilation system meeting ASHRAE 62.2 — incorporated into Title 24 — plus local exhaust at the bathrooms and kitchen. This is mandatory regardless of ADU size, is separate from heating and cooling, and is one of the most commonly missed items on incomplete ADU plans.The two layers of required ventilationWhole-building (dilution) ventilation: a continuous, mechanically driven supply of outdoor air sized to the dwelling's floor area and bedroom count. This is the headline requirement and the one most often missed. It is not waivable by size.Local (spot) exhaust: bathroom exhaust fans and a kitchen range hood ducted to the exterior (recirculating hoods generally don't satisfy the California Mechanical Code). These are in addition to whole-building ventilation, not a substitute.Typical ADU ventilation ratesThe required continuous rate rises with floor area and bedroom count. As rough benchmarks:ADU sizeApprox. continuous ventilation800 SF, 1 bedroom~30–40 CFM1,200 SF, 2 bedroom~45–55 CFMThe engineer calculates the exact target for your unit; these figures illustrate the order of magnitude.How ADUs meet the requirementSeveral approaches satisfy whole-building ventilation, and the mechanical plan must specify which one is used:Continuous exhaust: a quiet, energy-efficient bath fan rated for continuous duty, wired to run continuously. Simple and economical.Balanced ventilation with an ERV or HRV: an energy- or heat-recovery ventilator exchanges stale indoor air for fresh outdoor air while recovering most of the heat (and, for ERVs, moisture). The most comfortable and efficient option.Supply ventilation: ducting a measured amount of outdoor air to the HVAC air handler so incoming air is filtered and tempered.Why ventilation is non-negotiable in a tight ADUModern ADUs are built tight to meet the energy code, so they no longer "breathe" through gaps the way old construction did. Without deliberate mechanical ventilation, moisture, CO2, cooking byproducts, and VOCs from finishes accumulate indoors. That is exactly the problem ASHRAE 62.2 solves — and it is why a HERS rater field-measures the installed ventilation airflow to confirm the system delivers the required CFM. A system that looks right on paper still has to perform in the field.Ventilation checklist for ADU plansCalculate the required whole-building rate from floor area and bedroom count.Select a strategy (continuous exhaust, ERV/HRV, or supply) and specify equipment and CFM.Confirm the system is wired for continuous operation with appropriate controls.Add local exhaust: a kitchen hood ducted to the exterior and bathroom fan(s) — separate from whole-building ventilation.Note HERS verification of ventilation airflow on the plans.Ventilation rates and verification requirements vary by code cycle and jurisdiction — confirm current details with your local building department. Our mechanical plans include the ASHRAE 62.2 design, calculated rate, and equipment schedule, and pair cleanly with a bundled Title 24 report. See pricing or start your order.

Question 8

What happens if HVAC is installed differently than shown on approved plans?

Accepted Answer

If HVAC is installed differently than the stamped, approved plans, the work can fail inspection and the permit cannot close until the discrepancy is resolved. Minor field adjustments can often be handled with a field-change note, but a material change — a different system type, a relocated condenser, or a substituted equipment model — generally requires a formal plan revision approved before the work is done.Why the installation has to match the plansThe approved drawings are the legal basis for the permit. The inspector checks the installed system against them to confirm it is the same equipment, in the same locations, meeting the same Title 24 efficiencies and Manual J sizing that the plan reviewer signed off on. When the field condition doesn't match, the inspector has no approved basis to pass it — so the deviation, not necessarily a defect, is what holds up the final.Minor vs. major deviationsType of changeTypical pathSmall register relocation, minor duct rerouteField-change note / inspector discretionDifferent equipment model (same capacity & efficiency)May need a revision so the schedule and Title 24 report matchChanged system type (e.g., ductless to ducted)Formal plan revision before work proceedsRelocated outdoor condenser / new setbacksFormal plan revision before work proceedsLower-efficiency equipment than approvedRevision and re-check against Title 24 minimumsThe Title 24 and HERS connectionAn equipment substitution is rarely just a drawing change. The equipment on the mechanical schedule must match the equipment modeled in the Title 24 energy report, and a HERS rater field-verifies items such as refrigerant charge, duct leakage (for ducted systems), and ventilation airflow. If the installed unit differs from what was modeled, the energy compliance documents and the HERS verification may both need to be re-run — which is why a quiet field substitution can cascade into multiple corrections.How to avoid the problemGet the design right up front — a complete Manual J, equipment schedule, ventilation, and condenser setbacks before submittal.If the contractor wants to change equipment, confirm the substitute meets the same capacity and Title 24 efficiency before installing.For any material change, file a plan revision and get it approved before the work is done.Keep the mechanical schedule and the Title 24 report consistent so HERS verification matches the installed system.Designing the system correctly the first time is the least expensive path. A change discovered at final inspection costs far more in delay than coordinating it during design.Revision procedures and what counts as a minor field change vary by jurisdiction — confirm with your local building department before deviating from approved plans. Our mechanical plans include two revisions and city corrections at no extra charge, and we coordinate the schedule with your Title 24 report so the documents stay aligned. See how it works or order here.

Question 9

What is included in a mechanical equipment schedule?

Accepted Answer

A mechanical equipment schedule is the table on the plan set that lists every HVAC and ventilation component with the data a plan reviewer needs to verify Title 24 compliance — manufacturer, model number, capacity, and efficiency ratings for each unit. It is the bridge between the equipment drawn on the floor plan and the energy-compliance documents, and a missing or incomplete schedule is a common plan-check correction.What each schedule entry includesFor the space-conditioning equipment (heat pump condenser and indoor heads or air handler), the schedule lists:Manufacturer and model number — the exact unit, so the reviewer can look up its rated performance.Capacity in BTU/hr (or tons) for both heating and cooling, tied to the Manual J load.Efficiency ratings — SEER2 for cooling and HSPF2 for heating on heat pumps — so the reviewer can confirm the unit meets current Title 24 minimums.Electrical data — voltage, phase, and minimum circuit/breaker sizing, which coordinates with the electrical plans.Quantity and zone served — which head or register serves which room.Ventilation and exhaust entriesThe schedule also documents the ventilation equipment, since ASHRAE 62.2 whole-building ventilation and local exhaust are required and field-verified:Whole-building ventilation unit (continuous exhaust fan, ERV/HRV, or supply) with make, model, and rated CFM.Bathroom exhaust fans — model and CFM, ducted to the exterior.Kitchen range hood — model and CFM, ducted to the exterior (not recirculating).How a schedule reads — illustrative exampleTagEquipmentCapacityEfficiencyServesHP-1Heat pump condenser (multi-zone)24,000 BTU/hrSEER2 / HSPF2 per scheduleWhole ADUFC-1Indoor head (wall-mount)9,000 BTU/hr—Living/kitchenFC-2Indoor head (wall-mount)9,000 BTU/hr—BedroomVF-1Continuous ventilation fan——40 CFM whole-buildingEF-1Bath exhaust fan——Bath, ducted outThe capacities and ratings shown are illustrative — the actual values come from your ADU's Manual J and selected equipment.The schedule must match the equipment modeled in your Title 24 report. Keeping the make, model, and efficiency consistent across both documents prevents one of the most common plan-check corrections — a mismatch between the drawings and the energy calcs.Equipment schedule checklistEvery unit tagged and cross-referenced to the floor plan.Make, model, and BTU/hr capacity for heating and cooling.SEER2/HSPF2 efficiencies meeting current Title 24 minimums.Electrical data coordinated with the electrical plans.Ventilation and exhaust equipment with rated CFM.Consistency with the Title 24 energy report.Required schedule fields and local amendments vary by jurisdiction — confirm with your local building department. Our mechanical plans include a complete equipment schedule alongside the Manual J, and coordinate with electrical and Title 24. See pricing or start your order.

Question 10

Do I need a mechanical plan for a garage conversion if the garage already has a heater?

Accepted Answer

Almost always, yes. Converting a garage into an ADU triggers the full set of mechanical requirements for a new dwelling unit — and an existing garage heater rarely satisfies them. The conversion creates habitable space, so the code now requires a permanently installed system that maintains 68°F in every habitable room, whole-building ventilation, and Title 24 compliance, none of which a typical garage heater provides.Why an existing heater usually doesn't countA garage was never habitable space, so any heater already there was installed under a different, lower standard. When the garage becomes an ADU it must meet the requirements for a dwelling unit:Permanently installed heating to 68°F in every habitable room. The California Residential Code requires heating capable of maintaining at least 68°F at a point 3 feet above the floor and 2 feet from exterior walls in all habitable rooms. A single radiant garage heater or unit heater generally cannot demonstrate this across the new floor plan, and many such heaters are gas-fired units that don't meet current standards or local reach codes.Whole-building ventilation. Title 24 requires continuous ASHRAE 62.2 mechanical ventilation in the new unit — something garages never had.Cooling, effectively. The code mandates heating, not cooling, but in inland and desert climate zones cooling is essential for occupant safety, which a heater alone can't provide.Title 24 compliance. The conversion is new conditioned floor area and must be modeled, with equipment meeting current efficiency minimums.What the conversion typically needsIn practice, most garage-conversion ADUs replace the old heater with a ductless mini-split heat pump, which solves heating, cooling, and all-electric compliance in one unit, and adds a dedicated ASHRAE 62.2 ventilation system. The mechanical plan documents:A Manual J load calculation for the converted space (garages often have minimal insulation, which changes the load — the engineer applies code-minimum or upgraded envelope values).The heat-pump equipment schedule, sized to that load and meeting Title 24 minimums.The condenser location with property-line and window setbacks.ASHRAE 62.2 whole-building ventilation plus bath and kitchen exhaust ducted to the exterior.Condensate routing and refrigerant line-set routing.Garage conversions also usually require envelope upgrades — insulation, sometimes the slab and walls — to become habitable. Those upgrades change the heat load, so reusing the old heater without a load calculation is rarely defensible at plan check.The narrow exceptionIf — and only if — the existing system happens to be a permanently installed, code-compliant heat pump or furnace already sized for the converted space and meeting current Title 24 efficiencies, it might be retained. That is uncommon for a garage heater, and even then a mechanical plan is still needed to document sizing, ventilation, and compliance for the permit.Garage-conversion requirements and envelope rules vary by jurisdiction — confirm with your local building department before assuming any existing equipment can stay. Our mechanical plans for garage conversions include the Manual J, equipment schedule, and ventilation design sized to the converted space, and pair with a Title 24 report. See our mechanical guide or start your order.

Question 11

How do all-electric mandates affect mechanical plans?

Accepted Answer

In California cities that have adopted all-electric "reach codes," gas-burning HVAC is prohibited in new ADU construction — meaning the mechanical plan cannot show a gas furnace, gas space heater, or the gas piping and venting that serve them. The required alternative is all-electric equipment, most commonly a mini-split or ducted heat pump, which is why these mandates have made heat pumps the default on nearly every new ADU mechanical plan.What an all-electric mandate removes from the planDozens of California cities — including Los Angeles, San Jose, San Francisco, Oakland, Berkeley, and Sacramento — have adopted ordinances restricting natural-gas infrastructure in new buildings. Where these reach codes apply to ADUs, the mechanical plan cannot include:Gas furnaces or gas-fired space heaters.The gas piping, meters, and vent/flue systems serving mechanical appliances.Combustion-air provisions for those appliances (no longer applicable with no gas equipment).What the mechanical plan shows insteadUnder an all-electric mandate, the compliant ADU mechanical design centers on:Heat pump space conditioning — a ductless mini-split or ducted heat pump for heating and cooling in one all-electric unit, which also satisfies the code requirement to maintain 68°F in every habitable room.Electric-resistance backup or supplemental heat only where engineering justifies it.ASHRAE 62.2 ventilation — unchanged by the gas question, but always documented.Removing gas also simplifies the drawings: no flue routing, no combustion-air calculations, and tighter coordination with the electrical plans, since the panel must be sized for the higher all-electric load.An important nuance: it depends on your addressThere is no single statewide gas ban. Whether gas equipment is prohibited depends entirely on whether your jurisdiction has adopted an all-electric ordinance and how it is written — some apply only to new detached construction, some exempt certain appliances, and some are structured as energy-code amendments rather than outright bans. Because these reach codes change frequently and have been the subject of ongoing legal developments, confirm the current rule with your local building department before finalizing the mechanical design.Even in cities that still permit gas, the 2025 California Energy Code strongly favors heat pumps. Many owners choose all-electric voluntarily to future-proof against expanding restrictions and to simplify Title 24 compliance.All-electric mechanical checklistConfirm whether your city has an active all-electric reach code and whether it applies to your ADU type.If it applies, remove all gas appliances, piping, and venting from the mechanical plan.Specify a heat pump for space conditioning, sized from a Manual J.Coordinate the higher electrical load with the electrical plans (panel capacity).Keep the equipment consistent with the Title 24 energy report.All-electric ordinances and exemptions vary by jurisdiction and change frequently — confirm current details before you design. Our mechanical plans are built around your city's requirements, and the Full MEP package keeps mechanical, electrical, and plumbing coordinated under an all-electric design. Order here when ready.

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