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Building Code Reference

Got a CRC R325.8 correction?

Minimum room heating

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CRC R325.8 requires every dwelling to have a permanent heating system capable of maintaining a minimum indoor air temperature of 68 degrees Fahrenheit, measured 3 feet above the floor and 2 feet from exterior walls in every habitable room. The heating system must be a fixed installation — portable space heaters do not satisfy this requirement. Residential permits covering new construction, ADU additions, and whole-house remodels almost always trigger a plan-check review of R325.8 because the plans must name the heat source for each habitable space.

How to fix it

  1. Identify every habitable room on the floor plan

    Go through your floor plan sheet by sheet and mark every room that qualifies as habitable space — bedrooms, living rooms, dining rooms, dens, offices, and any added or converted room that will be occupied. Hallways, bathrooms, closets, and garages do not count. This is your checklist of rooms that each need a heat source called out on the drawings before the plan-checker is satisfied.

  2. Show the heat source for each room on the mechanical or HVAC plan

    For every habitable room on your list, the drawings must call out the heat source. If you are using a ducted forced-air system, show the supply register location and the duct run on the HVAC plan. If you are using ductless mini-splits, show each head unit with its room assignment. Hard-wired baseboard heaters need to appear on both the electrical plan (circuit) and the mechanical or floor plan (unit location). A note that says "heating per manufacturer spec" without showing the equipment location is not enough — plan-checkers want to see it on the sheet.

  3. Remove any reference to portable heaters as the heat source

    Scan your plans and notes for any language about portable, plug-in, or movable heaters. If you have a note like "supplemental heat via electric space heater" in any habitable room, delete it and replace it with a fixed system. Portable heaters are not a code-compliant heat source under R325.8. If the fix means adding a hard-wired baseboard unit you did not originally plan for, update the electrical panel schedule accordingly.

  4. Add the heating equipment to the mechanical schedule

    Your mechanical schedule (or equipment list) should include every heat-producing unit in the project: furnace model and BTU output, mini-split indoor head model and heating capacity, or hard-wired baseboard wattage and room assignment. If the schedule is missing or incomplete, the plan-checker may flag R325.8 even if the floor plan shows the equipment locations. Each entry should show the room served, the unit model or spec, and the heating output.

  5. Confirm the system can hit 68 degrees at the design outdoor temperature

    R325.8 requires that the system can actually maintain 68 degrees in each habitable room under local design conditions, not just at mild outdoor temps. If a plan-checker questions the load capacity, you will need a Manual J residential load calculation (or the simplified calculation allowed by the California Mechanical Code) showing that the equipment is sized for the design day. Most software used by HVAC contractors, such as Wrightsoft or ACCA-approved tools, produces this report. Attach it as a supplemental sheet.

  6. Address converted spaces separately

    If the permit covers a garage conversion, sunroom enclosure, or any space changing from non-habitable to habitable, you cannot just assume the existing system covers it. Show on the plans either that a new supply duct or register serves the converted space, or that a new supplemental unit is being added. If the existing furnace is large enough to cover the added load, note that on the plans and attach the load calc showing available capacity. A statement like "existing HVAC to serve new room" is better than silence but not as strong as a load calc.

  7. Cross-reference your Title 24 energy compliance report

    Your CF1R or CF2R compliance report from the Title 24 energy analysis already lists the heating equipment and its rated output for each zone. Pull that report and make sure the equipment shown there matches what is on your HVAC plan and mechanical schedule. Mismatches between the energy compliance report and the mechanical plan are a separate flag, but catching them now saves a correction round later.

  8. Add a general note on the cover sheet or general notes sheet

    A single catch-all note on the general notes sheet makes it easy for the plan-checker to find R325.8 compliance quickly. Something like: "All habitable rooms are provided with a fixed heating system capable of maintaining 68 degrees F at 3 feet above floor and 2 feet from exterior walls per CRC R325.8. See mechanical plan for equipment location and schedule." This note does not replace showing the equipment on the drawings, but it signals to the reviewer exactly where to look and shows you know the requirement.

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Why you got flagged

Plan-checkers flag R325.8 most often when the heating system is missing from the plans entirely. On new construction and ADU projects, every habitable room must have an identified heat source on the mechanical or architectural drawings. If the plans show a bedroom, office, or living space without noting how it gets heated, the correction letter will come back citing R325.8 every time.

A second common flag is specifying a heating source that does not count as permanent. Contractors sometimes show a plug-in electric baseboard or a portable infrared panel as the room heat source. Those do not satisfy R325.8. The code requires a fixed system — hard-wired baseboard heaters, ducted forced-air furnaces, hydronic systems, or ductless mini-splits all qualify. A note that says heat is provided by a portable heater is an automatic correction.

Undersized equipment is the third scenario. R325.8 does not just require any heat source — it requires one capable of holding 68 degrees at 3 feet above the floor and 2 feet from exterior walls under design conditions. When the mechanical schedule shows a unit that cannot meet that load in the coldest design weather for the project location, the plan-checker will flag R325.8 and ask for a Manual J or simplified load calculation proving the equipment is adequate.

The fourth scenario shows up on remodel permits that add habitable space. If an existing home uses a central furnace that already heats other rooms, and the remodel converts a garage or sunroom into habitable space, the plans must show either that the existing system can serve the new room or that a supplemental heat source will be added. If the new room is just shown as habitable on the floor plan with no heat supply noted, expect a correction.

The official code

California Residential Code R325, Light, Ventilation and Heating (dgs.ca.gov)

Read the source →

Common questions

Does a ductless mini-split satisfy CRC R325.8?
Yes. A ductless mini-split in heating mode is a fixed, permanent heat source and fully satisfies R325.8 as long as it is properly sized to maintain 68 degrees under design conditions in the room it serves. Show the indoor head unit on the floor plan or HVAC plan, list it in the mechanical schedule with its heating capacity in BTU or watts, and you are covered. What does not work: calling out the mini-split on the architectural plans but leaving it off the mechanical schedule, or showing only one head for multiple habitable rooms when the airflow path between rooms is blocked by closed doors.
Do bathrooms and hallways need to meet R325.8?
No. R325.8 applies to habitable rooms only. The California Residential Code defines habitable space as space used for living, sleeping, eating, or cooking. Bathrooms, toilet rooms, hallways, laundry rooms, closets, and utility spaces are not habitable rooms under that definition, so they are exempt from the 68-degree heating requirement. You still need to serve them with heating if your Title 24 energy compliance requires it, but R325.8 will not be the citation used.
Can I use a wood-burning fireplace as the heat source for R325.8?
Not reliably. Plan-checkers generally do not accept a fireplace as the sole heat source for R325.8 compliance because a fireplace is not a thermostatically controlled, always-available permanent heater. It requires the occupant to actively operate it, and it cannot guarantee 68 degrees on demand. A gas fireplace with a thermostat is a gray area that some jurisdictions accept and others do not. If you want to use a gas fireplace as a primary or supplemental heat source, check with your local building department before submitting — do not assume approval.
What counts as a habitable room under CRC R325.8?
A habitable room is any room used for living, sleeping, eating, or cooking. In practice, that means bedrooms, living rooms, dining rooms, family rooms, dens, home offices, and kitchens. It does not include bathrooms, closets, hallways, garages, utility rooms, or unfinished spaces. When you convert a space from non-habitable to habitable, such as finishing a basement or converting a garage, that space immediately falls under R325.8 and needs a fixed heat source shown on the plans.
Do I need a Manual J calculation to pass R325.8 plan check?
Not always, but you need to be able to show that the heating system can meet the 68-degree requirement under design conditions. For straightforward projects where the equipment is obviously adequate, such as adding one bedroom to a house with an existing oversized forced-air furnace, the plan-checker may accept a note stating the existing system has sufficient capacity. If the project involves a new heating system, a significant addition, or a garage conversion, have your HVAC contractor produce at minimum a simplified load calculation. A full Manual J is the most defensible document if a plan-checker pushes back.
Does R325.8 apply to ADUs?
Yes. An accessory dwelling unit is a separate dwelling and must meet all R325 requirements independently. You cannot rely on the main house heating system to cover the ADU unless you can show a continuous, controlled supply of heat to each habitable room in the ADU. In practice, most ADU projects get their own mini-split or hard-wired baseboard heaters for each habitable room. Show each unit on the ADU floor plan and include it in the mechanical schedule. Missing this is one of the more common R325.8 corrections on ADU permits.

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