Should I air seal before adding insulation?

Yes, and it is the thing that decides whether the money was well spent. Insulation slows heat but does nothing about moving air, and air passes straight through fiberglass — so insulation over an unsealed attic floor leaves the house working like a chimney and underperforms whatever the bag claims. Seal the attic floor, fit baffles at the eaves, then insulate. Doing it in that order also costs less overall, because once a foot of loose material is down, reaching the top plates and chases underneath is several times the work.

Where does a house actually leak air?

Almost never where people look. The big ones are the attic hatch — frequently the largest deliberate hole in the whole envelope — the top plates of interior walls, open chases behind a bath or around a chimney, the gap behind kneewalls, dropped ceilings over bathrooms and cupboards, plumbing and wiring penetrations, and recessed light fittings. At the bottom of the house it is the rim joist and the sill. Windows and doors get the blame and are usually a small share. None of the attic ones are visible from inside, which is why they survive decades of redecorating.

Why is my floor cold if the problem is in the ceiling?

The stack effect. Warm air rises and escapes through gaps at the top of the house, and that air has to be replaced, so outside air is pulled in at the bottom — through the rim joist, the crawl space, around the sill and under doors. The draft at your ankles is the consequence of a hole in your ceiling. It runs harder the colder it gets, which is why a house can feel fine in October and drafty in January. Sealing the top of the house is usually what fixes the bottom of it.

Can you insulate over recessed lights?

Not over non-IC-rated ones, and this is fire safety rather than preference. Older recessed fittings shed their heat into clear air and the required clearance is part of how they stay safe; burying them in insulation or sealing over them removes that. The options are replacing them with airtight IC-rated fittings, which is a licensed electrician's work, or boxing them to maintain clearance. If a company quotes blowing insulation across a ceiling full of old cans and never raises it, that tells you what kind of job you are buying.

My bathroom fan vents into the attic. Does it matter?

A great deal, and it is very common. It is a hole in your ceiling that is also delivering a bathroom's worth of warm, wet air into the coldest part of the house, where it condenses on the underside of the roof deck and on the framing. That is how attics grow mold and how insulation gets wet and stops working. There is an invoiced job on this company's books where exactly that was found — fans ducted into a roof vent — replaced with two independent insulated runs to the gable, each with its own hood and backdraft damper. Worth doing while somebody is already up there.

Your House Is a Chimney: Why the Draft at Your Ankles Comes From a Hole in Your Ceiling

Q: What is the gray pellet insulation in my attic?

If it looks like loose pellets rather than fiberglass or shredded paper — small, lightweight, gray-brown, sometimes shiny or accordion-like — it may be vermiculite, and much of the vermiculite used in American attics before about 1990 was contaminated with asbestos. Treat it as asbestos-containing until a sample says otherwise: do not move it, vacuum it, sweep it, seal over it or insulate on top of it. Close the hatch and get a sample taken. This is not work we take on.

Q: Will air sealing make my house too tight?

In a typical older Michigan house, no — these houses leak several times more than a modern one and sealing the attic floor does not get near the point where mechanical ventilation becomes necessary. The real concern is narrower and worth naming: tightening a house changes the air available to a natural-draft furnace or water heater and how its flue behaves, and that is a combustion safety question for a licensed mechanical contractor rather than something to assume away. Where there is an atmospherically vented appliance, that check comes first.

Q: Should I stuff insulation into the eaves to stop a draft?

No, and this is one of the most common well-intentioned mistakes in an attic. That gap is the roof's intake ventilation. Blocking it stops the roof deck being ventilated, which causes moisture problems and ice dams — the exact things people add insulation to fix. Baffles go in at every rafter bay first to hold that channel open, and only then does the depth go up.

Insulation slows heat. It does not stop air.

That one sentence explains why people spend real money insulating an attic and then report that the house feels much the same — and it is the reason air sealing comes first, not second.

Want somebody to look? Send photographs and we will tell you what you are dealing with. Somebody goes up there, lists what they find, and you get a fixed price in writing before anything starts. Book a free quote or call 517-505-7135.

Your house is a chimney

Warm air rises, finds the gaps at the top of the building, and leaves. That air has to be replaced, so outside air gets pulled in at the bottom — through the rim joist, the crawl space, around the sill, under doors.

This is the stack effect, and it runs harder the colder it gets outside. Which leads to the single most counter-intuitive fact in this subject:

The draft at your ankles is caused by a hole in your ceiling.

Blowing insulation over an unsealed attic floor does not interrupt that loop. Air travels straight through fiberglass. The insulation is doing its job — slowing conduction — while the air carrying most of your heat goes right past it.

Where a house actually leaks

Almost never where people look. Windows and doors get the blame and are usually a small share of the total.

The real ones, in rough order of size:

The attic hatch. Frequently the largest deliberate hole in the entire thermal envelope of the house. Also the cheapest to fix.
Top plates of interior walls. Every stud cavity in the house is open at the top unless somebody sealed it, and almost nobody did.
Open chases — behind a bath or shower, around a chimney, behind kneewalls, above a dropped ceiling or soffit over a bathroom or cupboard. These are often several square feet of straight hole.
Plumbing and wiring penetrations. Dozens of them.
Recessed light fittings. Each one is a vent, and older ones cannot simply be covered — see below.
The rim joist, at the bottom of the loop, in the basement or crawl space.

None of the attic ones are visible from inside the house. That is why they survive decades of redecorating, new windows, and a new furnace.

Four things that stop the job

These are not cautions. Each one is a reason to put the insulation bag down, and all four are common in Lansing housing stock.

1. Non-IC recessed light fittings. Older recessed cans are designed to shed their heat into clear air, and the required clearance around them is part of how they stay safe. Burying them in insulation or sealing over them removes that. They get replaced with airtight IC-rated fittings by a licensed electrician, or boxed to keep the clearance. If somebody quotes blowing insulation across a ceiling full of old cans and never mentions this, that tells you what kind of job you are being sold.

2. Knob-and-tube wiring. Same principle, worse consequence. It was designed to lose its heat to open air. Burying it is a fire risk, and it needs a licensed electrician to look at it before anything covers it. Houses of this age around here still have it.

3. Vermiculite. If what is up there is loose pellets — small, lightweight, gray-brown, sometimes shiny or accordion-like — rather than fiberglass or shredded paper, stop. A lot of the vermiculite used in American attics before about 1990 was contaminated with asbestos. Do not move it, vacuum it, sweep it, seal over it or insulate on top of it. Close the hatch and get a sample taken. This is not work we take on.

4. A fan that discharges into the attic. Extremely common, and it is both a leak and a damage source — a hole in your ceiling delivering a bathroom's worth of warm wet air into the coldest part of the house, where it condenses on the roof deck and the framing. That is how attics grow mold and how insulation gets wet and stops working.

We have an invoiced job on exactly that: bath fans ducted into a roof vent, replaced with two independent insulated runs to the gable, each with its own hood and backdraft damper.

Baffles before depth, always

It is tempting to stuff insulation into the eaves to stop a draft. Do not, and do not let anybody else.

That gap is the roof's intake ventilation. Block it and the roof deck stops being ventilated, which causes moisture problems and ice dams — the exact things people add insulation to fix. Baffles go in at every rafter bay first, then the depth goes up.

Will it make the house too tight?

In a typical older Michigan house, no. These houses leak several times more than a modern one, and sealing an attic floor does not get near the point where mechanical ventilation becomes necessary.

The real concern is narrower and worth naming properly: tightening a house changes the air available to a natural-draft furnace or water heater, and how its flue behaves. That is a combustion safety question for a licensed mechanical contractor, and where there is an atmospherically vented appliance, that check comes first rather than being assumed away.

What we will not promise

A dollar saving. A blower door reading before and after is a real measurement and you will get it honestly. A predicted saving depends on fuel price, weather and how a household lives — anybody quoting one is presenting a model as a fact.

Four Michigan programs pay toward this work and one has no income test at all; the energy rebates page sets out which is which and exactly where this company stands on each.

What to do on the next cold day

Walk the house with the back of your hand near the floor at exterior walls, at the rim joist, and around the attic hatch. Moving cold air is easy to feel.
Open the attic hatch and look at the perimeter. If you can see down the gaps between ceiling joists and the top of the wall below, that is the leak.
Count your recessed lights and look for a label inside one.
Find out where the bathroom fan goes. No hood outside means it goes into the attic.
Look at the material. Loose gray-brown pellets means close the hatch.
Check the eaves from inside. Insulation stuffed in them means the ventilation is already blocked.

Book it

Book a free quote · call 517-505-7135 · or read more about air sealing and draft proofing.
Then the depth: attic insulation. Ice at the gutters? ice dams are an insulation problem. Who pays? Energy rebates and grants.
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