Heating and cooling eat 40–50% of a typical home's energy bill. Most homeowners respond to that fact by buying insulation. Reasonable instinct, wrong order of operations. It's the kind of mistake that's invisible until you check the receipts against the thermostat.

Insulation slows heat transfer. It does nothing about air moving through gaps, cracks, and penetrations. A beautifully insulated attic sitting on top of a leaky ceiling is like a wool sweater with the zipper open: technically warm, practically useless. Air sealing first, insulation second, isn't a nice-to-have sequence. It's the sequence, full stop.

Notice what's not in that list: buying insulation first and hoping. This is the same logic behind almost every upgrade in this newsletter: the sequence determines the payoff more than any single product does.

A blower-door test quantifies how leaky your house actually is (measured in ACH50); paired with infrared imaging, it'll show you exactly where the bypasses are. Many utilities subsidize the audit. Get one before the work and after: "before and after" is the only honest way to know the sealing actually worked, and it's a reasonable thing to ask any contractor to show you.

Air sealing changes how moisture moves through your house. That's a feature, but only if you plan for it. Tight homes need deliberate ventilation (bath/kitchen exhaust fans at minimum, an ERV/HRV if you've sealed aggressively). And never insulate over an active roof leak or a damp basement wall. You'll trap the moisture problem behind a warm blanket, not solve it. (This is exactly the kind of shortcut that turns an energy project into a mold project. More on that intersection in a future issue.)

The federal 25C credit that used to cover 30% of insulation and air-sealing material costs no longer applies. It was eliminated for expenses incurred after December 31, 2025. Before you budget this project, check your state energy office and your utility directly; many still layer rebates on top of what's left of federal programs, and those vary a lot by state.

Feel a cold draft near an outlet or light switch on an exterior wall? That's not an insulation gap. That's an air-sealing bypass. No amount of blown-in fiberglass fixes it; a $2 foam gasket behind the cover plate does.

A HUGE arguments against air-sealing is the need for ventilation. That is absolutely important to take into consideration. ANOTHER large issue is detailing these during renovation/new construction. Someone has to physically carry this out and to do that they need to be trained to properly carry is out. The technology and knowledge is there. We have incredible ERVs and air supply/return that automatically can manage indoor air quality and CO2 levels.

There are stories of people moving into the Passivhaus directly after a fire. They closes the windows and doors, left, and when they came back after the smoke had cleared they had little to no smoke damage. If we lived in the countryside with access to lots of fresh air, I might say air-sealing is not necessary, and to skip it, building must breath. The issue is all the other details and the carry-out construct-ability of more traditional breathable membranes. This debate will continue with some interesting examples to come in the future, but for now I’m presenting you this information to carry out your own decision.

Opening the windows/doors in the Summer is so nice. I would never say not to. Depending on where you are (hopefully there is a screen), regardless some amount of dew is present in the air, especially in the early mornings. This actually brings in dust + mites, besides of course some moisture. Priority in the morning when its getting warm, please if the AC is running close all windows and doors, this will save energy (and $$) but also help dry things out. It’s a idea for health to wash sheets even more regularly in the hot months, pillowcases, upholstery needs a vacuum, and get a solid dusting in. Mites and the like can effect us in various ways but its another onslaught to the system, and we’re trying to build resilient homes here that help us to have more resilient bodies.