TASKS REGARDING COMBUSTION AIR DETERMINE IF THERE IS ENOUGH COMBUSTION AIR FOR THE TYPES OF APPLIANCES IN THE CAZ Use one of two methods, depending on appliance type and whether or not you have a blower door test PLAN FOR ADDING COMBUSTION AIR As per NFPA 54 and NFPA 31, and the IRC The air can come from the outside or the inside
INADEQUATE COMBUSTION AIR CAN BE A BARRIER TO AIR SEALING AND INSULATING IN THE NATIONAL JOB TASK ANALYSES FOR ENERGY AUDITOR - It is part of an energy auditor s job to evaluate the need for, and supply of, combustion air
COMBUSTION AIR Natural draft heating systems (often referred to as atmospheric draft heating systems) require combustion air from the room where the appliance is located. If the room is too small to provide adequate combustion air: The chimney may not draft properly. Draft is a pressure measurement used to determine how well a chimney is exhausting combustion gases. The combustion process can be hindered. This can create unacceptable levels of CO. And, excess CAZ depressurization due to exhaust fans is more likely to occur, and cause spillage. An easy test is to open a window. If the draft pressure increases, combustion air is most likely needed.
COMBUSTION AIR The National Fire Protection Association s National Fuel Gas Code (NFPA-54) and NFPA- 31 for Oil state that combustion air must be provided for any combustion zone where the collective fuel input exceeds the calculated requirement. Make-up air can be provided from outdoors or from other zones of the building. Photo Courtesy of NRCERT
THERE ARE TWO METHODS TO CALCULATE COMBUSTION AIR REQUIREMENTS METHOD #1: In the cases where no blower door test will be done: Use the Standard Method: 50 cu. ft. of air volume must be provided for each 1,000 BTU input METHOD #2: In cases where a blower door test will be done, and when fan assisted appliances exist: Use the KAIR Method (Known Air Infiltration Rate Method) which uses Air Changes per Hour (ACHn) in the calculation. This may reduce the required combustion air The KAIR Method must be used if the building s ACHn is less than.4
METHOD #1, STANDARD METHOD: CALCULATING EXAMPLE WHERE NO WHOLE HOUSE AIR LEAKAGE MEASUREMENT (CFM50) IS AVAILABLE: AS IN THE CASE WHERE THERE ARE BARRIERS TO DOING WORK AND BARRIERS TO DOING A BLOWER DOOR TEST Calculate the required CAZ volume to provide sufficient combustion air for a furnace and water heater totaling 120,000 BTUH input. Fifty cubic feet of volume must be provided for every 1,000 BTUH of appliance input. BTUH Input 1,000 x 50 = cu. ft. of combustion air required BTU input 120,000 1,000 = 120 120 x 50 = 6,000 cubic feet of combustion air required
METHOD #2, KAIR METHOD: CALCULATING EXAMPLE WHERE A WHOLE HOUSE AIR LEAKAGE MEASUREMENT (CFM50) IS AVAILABLE Combustion air requirements non-fan-assisted appliance: Combustion air requirements fan-assisted appliance:
CONVERTING CFM50 TO ACHn EXAMPLE 3 story row home 3500 CFM50 17,000 cu. ft. volume If the answer is greater than.6 ACHn, use.6
COMBUSTION AIR REQUIREMENTS FOR COMBUSTION APPLIANCE ZONE STANDARD METHOD UNCONFINED SPACE: More than 50 cubic feet of volume per 1000 BTUH of gas input rating (all combustion appliances combined) ALL OTHER SPACES ARE CONSIDERED CONFINED
COMBUSTION AIR REQUIREMENTS FOR COMBUSTION APPLIANCE ZONE KAIR METHOD UNCONFINED SPACE: CALCULATION IS BASED ON BUILDING VOLUME, APPLIANCE INPUT, AND BUILDING ACHn ALL OTHER SPACES ARE CONSIDERED CONFINED
SOLUTIONS FOR INADEQUATE COMBUSTION AIR (CONFINED SPACE) Ducted, for confined spaces (refer to NFPA definition for confined space) Shared makeup air from the rest of the building Makeup air directly from outdoors
One opening must be located within 12" of the ceiling, and one must be located within 12" of the floor. MAKEUP AIR OPTIONS IN A CONFINED SPACE: FROM INSIDE THE BUILDING TO AN UNCONFINED SPACE The space where the appliances are located must INCLUDE 2 PERMANENT OPENINGS communicating with an unconfined space, each of which must have a minimum free area of 1 square inch per 1000 BTUH of the total BTUH input.
MAKEUP AIR OPTIONS IN A CONFINED SPACE: FROM OUTSIDE USING DUCTS The space where the appliances are located must include 2 PERMANENT OPENINGS COMMUNICATING WITH THE OUTDOORS, each with a free area of 1 square inch per 2000 BTUH of the total BTUH input. One opening must be located within 12" of the ceiling, and one must be located within 12" of the floor.
MAKEUP AIR OPTIONS IN A CONFINED SPACE: FROM OUTSIDE USING A SINGLE OPENING The space where the appliances are located can include 1 PERMANENT OPENING COMMUNICATING WITH THE OUTDOORS, each with a free area of 1 square inch per 3000 BTUH of the total BTUH input. It must measure no less than the total area of the vent connectors and must be located within 12" of the ceiling.
MAKEUP AIR OPTIONS IN A CONFINED SPACE: FROM OUTSIDE FROM VENTILATED CRAWL SPACE AND VENTILATED ATTIC The space where the appliances are located can include 2 PERMANENT OPENINGS COMMUNICATING WITH THE OUTDOORS, each with a free area of 1 square inch per 3000 (5000 for oil) BTUH of the total BTUH input. They must measure no less than the total area of the vent connectors.
MAKEUP AIR OPTIONS IN A CONFINED SPACE: FROM OUTSIDE USING A TWO OPENINGS TO THE VENTILATED ATTIC The space where the appliances are located can include 2 PERMANENT OPENINGS COMMUNICATING WITH THE OUTDOORS, each with a free area of 1 square inch per 3000 (5000 for oil) BTUH of the total BTUH input. It must measure no less than the total area of the vent connectors and must be located within 12" of the ceiling.
AUDIT STEP FLOW (add to the combustion safety testing protocol Action Table AND use the $500 allowance for combustion appliance repair) 1. Is there a natural draft furnace, boiler, or water heater? If yes, 2. Do you plan to do air sealing or insulation? If so, a. Measure the CAZ volume and complete the Confined Space Calculation worksheet. b. If inadequate combustion air, (confined space), make a plan for adding combustion air according to the worksheet If $500 takes care of the issue, add make-up air If $500 isn t enough money to fix the problem, complete the H&S form and require the customer to remediate the issue before air sealing or insulating Include the Confined Space Calculation worksheet in the job file