Ask This Old House Season 23 Episode 23: Miami Airflow, Shellac Removal, and a Blacksmith Who Forged a Business

Season 23, Episode 23 of Ask This Old House sends Ross Trethewey to Miami, Mauro Henrique to a New England window, and Kevin to a Connecticut barn that now belongs to a metal fabricator. The house calls look unrelated: one is a comfort complaint, one is a finish failure, one is a career profile. But the first two both come down to diagnosis. Ross measures airflow before recommending equipment; Mauro tests alcohol on a small spot before touching the whole window. The third segment is about what happens when someone gets that kind of patient instruction early and keeps building on it.

Miami bedroom runs hot, and the numbers explain why

Khory's primary bedroom in Miami runs six or seven degrees warmer than the rest of the house. He had already tried a jump duct and remote thermostats. The jump duct improved things by a degree or two. The remote thermostat made the bedroom comfortable by making other rooms Arctic cold. Ross calls that what it is: the system is now sensing the bedroom and driving the whole house to satisfy one room.

Ross starts with a Manual J load calculation. Khory sent floor plans ahead of time, so Ross has a head start on room dimensions, windows, wall insulation, roof insulation, and the rest of the thermal envelope. That calculation tells him how much air the bedroom actually needs. Then he brings in local contractor Genry for a home performance assessment.

The blower door test measures air leakage. The prep matters: all interior doors open, all exterior doors and windows closed, exhaust fans, HVAC, and combustion devices off. The house comes in around 1,700 CFM50. Ross and Genry call that not great. With the HVAC running, the house depressurizes to -0.9 pascals. That points toward supply duct leakage pulling outdoor air into the living space. They also check pressure differences and want to see less than 3 pascals, which suggests the return-air pathway is not the main problem.

A flow hood measures the bedroom supply. With the bedroom door open, it reads less than six CFM. With the door closed, it reads 61.5 CFM. That is a clue, not a complete answer. At the three-ton air handler, static pressure sits in the yellow range. The unit is not moving as much air as it should. The bedroom gets about 135 CFM when the load calculation says it needs roughly 170. Overall duct leakage is about 20 percent, with losses in the garage and attic.

The good news: the three-ton system is correctly sized and only eight years old, with 15 to 20 years of expected life. Ross does not push a new condenser. He gives Khory a tiered plan. First, seal and resize the return side, including a proper filter and return-air grille, because the air handler is accessible in the garage and dropping static pressure there should move more air. Second, fix and seal the attic supply ducts so every room gets the right amount. Third, ideally, bring the HVAC unit into conditioned space by building an insulated, air-sealed closet around it.

If you have read the split heat pump water heater recap at /posts/ask-this-old-house-season-24-episode-13-split-water-heater-attic-ladder, you know Ross likes to test before replacing. Here that instinct saves Khory from buying equipment he does not need. The homeowner can replace filters, keep returns clear, and stop using a remote thermostat as a comfort fix. The duct sealing and load calculation are not weekend DIY. The blower door and flow hood are how you avoid guessing.

Shelby Barnhart forges a business from a childhood barn

The profile segment visits Shelby Barnhart, a metal fabricator in northern Connecticut. She works out of a country carpenters barn her parents put up in 1993. When she and her husband bought the property, they converted it into her workshop. The barn was her father's workshop and storage area for classic cars. She says she always wanted it for her own shop. Now she has it, and she is making new memories there with her kids.

Her path is specific. She practiced welding in auto shop in ninth, 10th, and 11th grade. The summer she turned 15, she volunteered at Mystic Seaport as a junior volunteer, working under Craig. That is where she learned traditional skills. He made her forge 100 hooks the way he wanted before she could start another project. After high school, she spent a year with a metal artist, Susan Madacsi, learning modern blacksmithing and propane forges instead of coal. She calls propane more efficient, easier, and cleaner.

She uses a 4x8-foot boiler plate welding table made by one of her mentors. She buys horseshoes and forges them into other things. She has made about 5,000 hinging rings, hundreds of horseshoe wine racks, decorative hooks, and fireplace cranes. Welding is her favorite process. She calls it soothing.

The business grew from local repair jobs and railings into an online store with hooks and wine racks, then handrails. Her dad suggested a handrail she could ship like her other products. She put them on her website, and they took off. She says she has made about 15,000 handrails and was picked up by major retailers to dropship. That is the turning point she describes.

Three kids and COVID forced her into lean manufacturing. She cut all material first, scrolled in batches, welded for days, then processed orders. Now that her kids are in school, she hopes to scale back up. She is also a certified teacher for the state tech school system. Her advice is blunt: find a mentor. She points out that many skilled tradespeople are retiring and not enough people are coming in to replace them.

There is no repair here to rate like a trim or a duct. But if you have ever thought about blacksmithing, the takeaway is not to buy an anvil first. Find a class, a mentor, or a tech school program. Shelby's shop exists because people taught her, and now she teaches.

Mauro removes shellac with alcohol, patience, and safety gear

Mark and Arch have gumwood trim with a heavy, scaly texture. Mauro identifies it as shellac that was applied improperly. Two likely causes: multiple coats without enough drying time, and applying finish in a cold New England house. Shellac dries fast, but not if you rush it or ignore temperature.

Mauro tests natural alcohol on a small spot with a brush. He leaves it for one or two minutes, then scrubs with a pad. It goes down to bare wood. Mark is surprised. Mauro then has them take down the blinds and tape off the area. They put on goggles, masks, and gloves. He applies alcohol, waits, and scrapes. He tells Arch this is a slow-process job. Working fast can damage the wood or scratch it.

Once the shellac is gone, they lightly sand with 220 grit, vacuum, and apply a water-based satin polyurethane. Mauro chooses water-based partly because it off-gasses less than oil, and there is a baby in the house. The finish is thin, so the wood will absorb it. He says two to three coats, with light sanding between coats. The first coat dries in about two hours. The reveal shows the difference between the textured old window and the cleaned new one.

In a previous recap of Mauro's paint-spill rescue at /posts/ask-this-old-house-season-24-episode-14-s24e14-3-way-switch-split-rail-fence-paint-cleanup, the rule was speed: act now before paint dries. Shellac removal runs the other way. Alcohol needs time to soften the finish, and the scraper needs a light hand. Same trade, opposite clock.

A homeowner can attempt this, but test first. Use natural alcohol in a ventilated space, wear eye and skin protection, and work a small area before committing to the whole window. If the trim is historically significant or the finish is unknown, call someone who knows old finishes.

DIY Confidence Scale

Miami airflow diagnosis and duct repair: 2/10 for DIY. You can change filters and keep returns clear. You should not guess at load calculations, static pressure, or attic duct sealing without training and tools.

Shellac removal and refinishing: 7/10 for DIY. It is slow, messy, and solvent-heavy, but the sequence is learnable. Test a hidden spot, ventilate, wear gear, and respect dry times.

Blacksmith business profile: 1/10 as a DIY project. 10/10 as a reminder to find a mentor before buying equipment. Metal fabrication is a trade, not a weekend kit.

Additional Resources

• Watch on PBS
• Official This Old House episode page

Ross does not sell Khory a new AC unit, and Mauro does not sand the window into dust. The episode is better for both choices. If your bedroom runs hot, would you rather buy another thermostat or pay someone to measure the ducts?