2.5 Operable Windows (A07), Combustion Minimization (A10) & Source Separation (A11)

2.5 Operable Windows (A07), Combustion Minimization (A10) & Source Separation (A11)

Core Exam Takeaway: A07 Operable Windows (2 pt / Core 4 pt) has a two-part structure with a dependency and an eligibility gate. A10 Combustion Minimization (1 pt / Core 2 pt) includes the easily forgotten 30-second vehicle idling option. A11 Source Separation (1 pt / Core 0.5 pt) is where negative pressurization, self-closing doors and commercial kitchen hood geometry actually live.

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Feature A07: Operable Windows — Optimization (2 pt / WELL Core 4 pt)

WELL's framing is a genuine tension. Naturally ventilated buildings report fewer sick-building-syndrome symptoms than mechanically conditioned ones, and WELL cites a 7.7% productivity benefit associated with naturally ventilated spaces. But ventilating through windows "generally introduces more outdoor pollution than mechanical systems with filters," and human behaviour is among the top three factors affecting indoor pollutant persistence. A07 therefore pays for windows and for telling occupants when to use them.

The eligibility gate

[!IMPORTANT] Projects where the average outdoor $PM_{2.5}$ is 35 µg/m³ or higher may only achieve Part 1 in conjunction with Part 2. In a heavily polluted city, providing windows without a window-use management system earns nothing. Projects consult the WHO Global Urban Ambient Air Pollution Database to establish outdoor levels.

A07 Part 1 — Provide Operable Windows (1 pt / Core 2 pt)

Meet one of:

1. At least 75% of the regularly occupied spaces have operable windows that provide access to outdoor air; or
2. For each floor, the openable window area is at least 4% of the net occupiable floor area.

WELL Core guidance: whole building; for area calculations, projects may use assumptions of regularly occupied spaces in leased spaces.

[!WARNING] The 4% of net occupiable floor area figure belongs to A07 Part 1, not to A03's natural-ventilation pathway. A03 Option 2 governs natural ventilation through design standards (ASHRAE 62.1 Natural Ventilation Procedure, CIBSE AM10, AS 1668.4) plus outdoor air quality thresholds and window-control provisions — it sets no free-area percentage.

A07 Part 2 — Manage Window Use (1 pt / Core 2 pt)

Only achievable if Part 1 is also achieved. Meet one option:

Option 1: Outdoor air measurement. Outdoor $PM_{2.5}$, temperature and humidity are monitored at intervals of at least once per hour, based on a data-gathering station within 2.5 mi (4 km) of the building. The station may be operated by the project or by another entity such as a government.

Option 2: Window operation. Indicator lights at windows — at least one per room with windows — cue occupants when outdoor conditions are suitable for opening:

+-----------------------------------------------------------------------------+
|              A07 PART 2 OPTION 2: WINDOW-OPENING INDICATOR LOGIC            |
|                                                                             |
|   [Outdoor PM2.5 / temperature / humidity data]                             |
|                               |                                             |
|                               v                                             |
|     ALL THREE TRUE?   PM2.5 <= 15 ug/m3                                     |
|                       |Outdoor dry-bulb - indoor setpoint| <= 15 F (8 C)    |
|                       RH <= 65%                                             |
|                               |                                             |
|        +----------------------+----------------------+                      |
|        v YES                                         v NO                   |
|   INDICATOR CUES "OPEN"                       INDICATOR CUES "KEEP CLOSED"  |
|   (at least one light per room with windows)                                |
+-----------------------------------------------------------------------------+

[!WARNING] WELL v2 does not require window opening restrictors, maximum sash travel, one-hand latch operating forces, or magnetic contact switches interlocked to the building automation system. Those are code and energy-management practices. A07's requirements are the 75% / 4% provision test and the monitoring or indicator-light management test.

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Feature A10: Combustion Minimization — Optimization (1 pt / WELL Core 2 pt)

Combustion from space heating, cooking and nearby transportation is a major and often overlooked indoor pollution source, producing fine particles, nitrogen dioxide and carbon monoxide. Beyond nausea, loss of consciousness and death, elevated CO inhalation is linked to headaches, visual impairment and reduced cognitive functioning.

A10 Part 1 — Manage Combustion

For all spaces except commercial kitchen spaces, meet some combination of:

Option 1: Appliance and heater combustion ban. Combustion-based fireplaces, stoves, space heaters, ranges and ovens are not used in occupiable spaces.

Option 2: Low-emission combustion sources. Equipment used for heating, cooling, water heating, process heating or power generation — including back-up equipment if used for more than 200 hours per year — meets some combination of:

• Complies with California's South Coast Air Quality Management District (SCAQMD) emission rules;
• Is electric; or
• Is supplied by district heating or cooling.

Option 3: Engine exhaust reduction. Vehicle engine idling for more than 30 seconds is prohibited in all pick-up, drop-off and parking areas at the building site controlled by the project, with "No idling" signage present at those locations.

WELL Core guidance: whole building.

[!TIP] Two details reward precision. The 200-hour annual threshold determines whether back-up generators fall inside Option 2's scope at all, and Option 3's 30 seconds is the single most-missed number in the Air concept — candidates guess 3 or 5 minutes because that is what municipal anti-idling ordinances typically use. WELL also sets no exhaust-stack separation distance from intakes in A10; the only separation distance in the Air concept is A11's 10 ft (3 m) for dwelling-unit range hood outlets.

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Feature A11: Source Separation — Optimization (1 pt / WELL Core 0.5 pt)

A11's intent is to preserve indoor air quality and olfactory comfort by isolating and properly ventilating pollution sources and chemical storage. WELL's issue statement names the specific culprits: chemical storage closets emitting VOCs, copy rooms generating ozone, bathrooms encouraging mold and mildew, and kitchen particulate matter, VOCs and polycyclic aromatic hydrocarbons.

A11 Part 1 — Manage Pollution and Exhaust

For all spaces except dwelling units. For all bathrooms, kitchens, rooms for cleaning and chemical storage, rooms with high-volume printers and copiers, and high-humidity areas:

• (a) Meet one of: separated from all adjacent regularly occupied spaces with self-closing doors and/or vestibules, or negatively pressurized compared with adjacent regularly occupied spaces.
• (b) Utilize exhaust fans such that the return air is vented outdoors and not recirculated.

For commercial kitchen spaces, all of the following:

• Canopy hoods have side or partial panels, when allowable by code.
• Type II hood overhangs and setbacks comply with ASHRAE 154-2011 (Table 3, Minimum Overhang Requirements for Type II Hoods) on all open sides.
• The vertical distance between the front lower lip of the hood and the cooking surface is ≤ 4 ft (1.2 m).
• Makeup air velocity near or directed at the hood is < 75 fpm (0.38 m/s).
• Replacement air introduced directly into the exhaust hood cavity does not exceed 10% of the hood exhaust airflow rate.
• At least 50% of the air replacing exhaust air is conditioned transfer air, rather than makeup air.
• Appliances are grouped under hoods by effluent production per ASHRAE 154-2011 duty levels (light, medium, heavy, extra-heavy).
• Appliances have a rear seal between appliance and wall, when allowable by code.
• Appliances at the end of a cook line requiring > 300 cfm/ft (460 L/s/m) have a full side panel or end wall.

For dwelling units, for all ovens, cooking burners and stove-top appliances using a range hood:

• Exhaust air is vented directly to the outdoors.
• Exhaust outlets are separated from any air intakes by at least 10 ft (3 m), unless local code specifies otherwise.
• Minimum operating exhaust airflow is the greater of 100 cfm per linear foot (150 L/s per linear meter) of range hood width, or 200 cfm (94 L/s).
• The range hood, when operating, covers at least 75% of the burner area.

WELL Core guidance: meet A11 in non-leased spaces.

[!WARNING] A11 is not a "cleanable materials" feature. WELL v2 has no A11 requirement for non-porous surfaces, coved baseboards or sealed expansion joints. Surface hygiene and contact reduction live in the Materials concept (X11 Cleaning Products and Protocols, and the beta feature X12 Contact Reduction), not in Air.

How the three features interlock

A07, A10 and A11 form WELL's source-control triad: A11 removes pollution at the source (isolate and exhaust), A10 eliminates the source entirely (electrify, ban combustion, stop idling), and A07 brings in clean outdoor air but only when it is genuinely clean. That ordering — eliminate, then isolate, then dilute — is the hierarchy WELL states in A11's solutions: "the most effective way to curb air pollution in buildings is to eliminate individual sources or capture emissions at the source, before they spread to surroundings."