The cheapest work that actually changes things

Insulation resists heat moving through a material — that’s what R-value measures. Air sealing stops air physically travelling through gaps, carrying heat and moisture with it. A thick layer of fiberglass with air moving through it performs far below its rating, which is why sealing usually has to happen first. Spray foam is popular precisely because it does both at once.

A house can be too tight without ventilation — but the answer to that is ventilation, not leaving random holes in the building. Relying on leaks for fresh air means you get lots of it on a windy January night and almost none in mild weather, and the air arrives via the crawl space and the attic rather than anywhere you’d choose. On most existing homes here we don’t get anywhere near the tightness where this becomes a live issue. When we do, we say so and discuss mechanical ventilation.

Not always. If the problem is obvious — an uninsulated rim joist, an attic hatch you can see daylight around — testing costs more than it tells you, and we’ll just do the work. Testing earns its place on whole-house jobs, on houses where the symptoms don’t match the usual suspects, and where a rebate program requires before-and-after numbers.

Often, yes — it’s one of the few upgrades where the cheaper option is genuinely the right one for a lot of houses. If you already have reasonable insulation depth and the complaint is drafts and cold spots, sealing alone can solve it. If the attic has three inches of compressed fiberglass, sealing helps but you’re still under-insulated. We’ll tell you which house you have.

Some of it, genuinely yes. Sealing around outlets, weatherstripping a door, foaming the gap where a pipe comes through a basement wall — all reasonable weekend jobs, and we’d rather you did them than paid someone. What’s hard to do yourself is finding the leaks that matter, working safely in an attic, and knowing what not to foam. Flues, chimneys and older recessed cans need clearance and high-temperature materials, and that’s the part where DIY goes wrong.

It often helps, because the air being pulled into a leaky house comes from the crawl space, the attic and the wall cavities rather than through a filter. Sealing those paths means more of your indoor air is actually conditioned, filtered air. It isn’t a medical intervention and we won’t sell it as one, but the connection between a damp crawl space and how the house smells is real.

On a typical retrofit of an older home, usually not — you’re bringing a very leaky house to a reasonably leaky one. It becomes a real question on deep retrofits and on new construction, where the target tightness is much higher. If your project heads that way we’ll raise it during the assessment, along with what kind of system makes sense, rather than leaving you to discover it later.