Weatherization and Draft Sealing Visit

Purpose

Air sealing is a combustion-safety job before it is an energy job. Every gap you close raises the depressurization an exhaust fan can pull on the house, and an atmospherically vented water heater or furnace vents on a few pascals of buoyancy. Tighten the shell around one and the flue can reverse, putting combustion products into the room the family sleeps above. That is why the monitor goes in before the caulk gun comes out.

The second thing this fixes is aim. Customers point at windows because that is where they feel the draft, but the air leaves through the attic plane and is replaced through the basement, so a visit spent on window trim gets a thank-you and no measurable change.

Scope

Covers a residential air-sealing visit in an existing house: combustion appliance inventory and monitoring, leak location and ranking, attic-plane bypass sealing, rim joist and basement sealing, door and window weatherstripping, and the combustion verification that closes the visit.

Does not cover insulation upgrades, duct sealing, ventilation design, any appliance repair or venting alteration, or a house with vermiculite in the attic. Regulated lead work belongs to the pre-1978 paint disturbance SOP, and exterior perimeter sealant to the caulking and sealant renewal SOP.

Roles and responsibilities

Procedure

1. Inventory the combustion appliances and put a monitor in the house before anything is sealed. Walk the house and list every fuel-burning appliance, its vent type (atmospheric into a chimney, induced draft, direct vent, unvented) and the room it sits in, and switch on a personal carbon monoxide instrument that reads in ppm. Acceptance: a written list with a vent type against each appliance, plus a baseline ambient ppm in the appliance room and in the main living space. Wrong looks like relying on the customer's ceiling alarm, which is built to a delayed response curve and is not a measuring instrument. Stop rule and shop default: any reading at or above 35 ppm in occupied space stops the visit, everyone goes outside, the house is ventilated and the appliance is shut off at its own valve or switch, and the customer is told in writing to call a heating contractor before it is relit. That default sits below OSHA's general-industry limit of 50 ppm as an eight-hour average at 29 CFR 1910.1000 Table Z-1, and at the NIOSH recommended time-weighted average, which also carries a 200 ppm ceiling. Hazard: carbon monoxide has no odor, so the instrument is the only warning, and it stays on the tech's body all day rather than in the bag.

2. Find the leaks and rank them by plane, not by where the customer feels them. Work the attic hatch, top-plate lines, chimney chases and penetrations, then the rim joist and basement, then doors and windows last, using a smoke pencil or an infrared scan on a day with a real indoor-to-outdoor temperature difference. Acceptance: a written list of leaks by location with a rough size, ordered attic plane, then basement plane, then openings, plus a worst-case depressurization reading in pascals taken before any sealing with the exhaust appliances running. Wrong looks like a list that starts at the windows, which is where the money goes and the air does not. Stop rule: no way to take a pre-work pressure reading means the post-work comparison cannot be made, so sealing runs in the basement and openings only and the attic plane is deferred. Hazard: none at this step beyond the attic access itself, which step 3 gates.

3. Gate the attic before you seal anything in it. From the hatch, before stepping in, look for loose pebble-like insulation, open knob-and-tube wiring, staining on the underside of the deck, and bath fans discharging into the space. Acceptance: each of those four looked for and answered in writing. Wrong looks like crawling in with a foam gun and finding the wiring afterwards. Stop rule: vermiculite is presumed asbestos-containing until sampled and nothing is disturbed, walked on or vacuumed, and that work leaves the shop under 29 CFR 1926.1101; open knob-and-tube stops sealing and insulating in that area, because NEC Article 394, in the edition your jurisdiction has adopted, does not permit concealed knob-and-tube in spaces enveloped by loose, rolled or foamed-in-place insulation, and it goes to an electrician. Hazard: the ceiling below is not a floor, so weight goes on joists or a laid plank only, the route is lit before it is walked, and attic heat is a real injury, so schedule the attic for the morning and come out at fixed intervals to drink water.

4. Seal the attic bypasses with a material rated for the clearance it lands in. Work the big holes first: open chases, dropped soffits, top plates and penetrations, using rigid material with sealant at the edges for anything larger than a hand, and a listed firestop assembly where a chase passes through the plane. Acceptance: every opening on the step 2 attic list closed and initialled, and at each flue or chimney the required clearance held with sheet metal and high-temperature sealant rather than foam or fiber, with the clearance value read from the vent's own listing or from the National Fuel Gas Code, NFPA 54 or ANSI Z223.1, in the edition your jurisdiction has adopted. Wrong looks like canned foam packed around a Type B vent, which is combustible material inside a listed clearance. Stop rule: a flue whose clearance cannot be held with the materials on the truck is left open and noted rather than closed with the wrong product. Hazard: foams carry isocyanates, a respiratory sensitizer that can leave a person reactive for good, so ventilate, follow the product's re-entry time, and take the respiratory protection its instructions and safety data sheet specify under a written program per 29 CFR 1910.134; fiberglass and cellulose being moved carry inhalation and skin routes, so long sleeves, eye protection and washing before eating.

5. Seal the basement and rim joist, then the openings the customer can see. Work the rim joist bays, the sill plate line and penetrations through the band, then move to door weatherstripping, sweeps, thresholds and window sash seals. Acceptance: every rim bay on the step 2 list treated, and at each door a strip of paper pulled through the closed seal with light drag at head, both jambs and sill, tested at three points per edge. Wrong looks like a door adjusted until the sweep drags on the floor, which the customer cuts off within a month. Stop rule: a door that will not seal because the slab or frame has moved goes to the interior or exterior door SOP rather than getting thicker weatherstrip. Hazard: the rim joist is where wiring and gas lines run, so nothing is stapled, screwed or foamed until the bay is lit and read, and no fastener goes into a bay you cannot see the back of.

6. Restore everything you disabled, then re-run the worst-case test and prove the appliances still draft. Turn back on anything switched off, replace the attic hatch dam and weatherstrip, reopen any covered register, confirm bath and range fans run, then set all exhaust appliances running and interior doors as the test protocol requires, take the house pressure with respect to outdoors again, and fire each atmospherically vented appliance while watching the draft hood or barometric damper. Acceptance: a restore line for every item recorded as switched off, removed or covered, matched one to one against the list made at the time; draft established with no spillage within 60 seconds of ignition as a shop default; ambient ppm in the appliance room after five minutes of run; and the before and after pressures on the ticket with their difference stated. Wrong looks like closing out on a mirror held near a hood for three seconds. Stop rule: spillage after 60 seconds, or ambient at or above the 35 ppm default, shuts the appliance off at its valve or switch, puts the finding in writing and routes it to a licensed heating contractor the same day; the shop does not restore draft by cutting a combustion-air opening, which is that contractor's design decision. Hazard: this step deliberately puts the house in the worst condition it will ever see with a burner lit, so the CO instrument stays on the tech's body, the occupants are out of the appliance room, relighting follows the appliance's own label instructions from the side of the burner compartment, and nothing that smelled of gas gets relit at all, because that is a leave-the-house-and-call-from-outside event.

The record this produces

The appliance list with vent type, baseline and post-work ambient ppm by room, the leak list ordered by plane, worst-case depressurization before and after with the difference stated, the four attic gate answers, the clearance value read at each flue with its source, the door seal result at three points per edge, the restore line for every disabled item, and the draft result per appliance.

The office reads the draft result when a customer calls about a smell, because a documented pass on the day is the difference between a callback and a claim. The next tech reads the before and after pressures to know how much tightening this house has already taken.

Worked pass: 1,600 sq ft ranch, atmospheric water heater in a utility closet

Step 1: gas furnace, induced draft, and a gas water heater, atmospheric into a masonry chimney, both in a closet off the kitchen. Gas range, unvented. Baseline ambient 0 ppm in the closet and 0 ppm in the living space.

Step 2: attic list carried nine items, the largest a fully open chase behind the chimney. Basement list carried the rim joist and two penetrations, doors and windows last. Worst-case depressurization before sealing, with the dryer, range hood and both bath fans running: 4.5 Pa with respect to outdoors.

Step 3: no vermiculite, no knob-and-tube, no staining, and the rear bath fan found discharging into the attic, recorded and left connected as found since re-routing it was out of scope.

Step 4: eight of the nine attic openings closed and initialled. The ninth was the chimney chase, where the clearance called for in the appliance vent listing was held with sheet metal and high-temperature sealant, no foam inside it.

Step 5: all rim bays treated. Front door pulled paper with light drag at head, both jambs and sill, three points per edge. Rear door failed at the strike jamb and was corrected with a shimmed strip.

Step 6 FAILED and took its stop rule. The restore list carried three items, all closed: the attic hatch dam and weatherstrip replaced, and both bath fans confirmed running, with the rear fan's attic discharge disclosed in writing. Worst case re-run under the same exhaust load then read 8.0 Pa. Against the 4.5 Pa recorded at step 2, 8.0 minus 4.5 leaves 3.5 Pa of additional depressurization added by the day's sealing. The water heater was fired and the draft hood still spilled at 90 seconds, past the 60 second default. Ambient in the closet was climbing but had not reached the 35 ppm action level when the tech shut the appliance off at its gas valve, so the leave-the-house rule was not triggered. The finding went to the customer in writing, the heating contractor was called that afternoon, and the shop did not cut a combustion-air opening. The sealing already done stayed in place, because reopening the attic plane is not a substitute for a correctly sized combustion air supply.

References

• 29 CFR 1910.1000 Table Z-1 for the OSHA carbon monoxide limit, with the NIOSH recommended limits as the tighter reference the shop default is set against
• 29 CFR 1910.134, which gates any respirator on a written program, and 29 CFR 1926.1101 for presumed asbestos-containing vermiculite
• NFPA 54 or ANSI Z223.1 (National Fuel Gas Code) and the vent manufacturer's listing for clearance to combustibles, in the edition your jurisdiction has adopted
• National Electrical Code Article 394 (concealed knob-and-tube wiring), in the edition your jurisdiction has adopted
• See related: Caulking and Sealant Renewal Visit; Exterior Door and Threshold Replacement; Pre-1978 Paint Disturbance: Stop and Assess