The heat will come on in the next few weeks, and the house will start behaving strangely. Cold at the ankles downstairs. Stuffy and too warm upstairs.
Below: why those two are the same problem, the sealing order most people get backwards, where to move the reading chair, and why the air goes dry the week the furnace starts.
Reply and tell us: which room in your place is the cold one? We read every one.
Warm Air Leaves at the Top. Cold Air Comes In at the Bottom.
Image: The Home Wire
Two complaints, same house, same winter. The floors are cold. The top floor is stuffy. It reads like two problems with two separate fixes.
It's one problem, and it has a name.
Warm air weighs less than cold air, so everything your furnace heats drifts upward. It gathers against the top ceiling of the house and pushes, looking for a way out.
It finds one. Ceilings are full of holes nobody thinks about: the attic hatch, recessed light cans, the gaps where wires and pipes run up through the framing.
Air leaves at the top. And because a house can't hold a vacuum, the same volume of air has to come in somewhere else.
It comes in low. Along the sill plate where the wooden frame sits on the concrete foundation, around basement windows, through the holes drilled for the water line and the electrical service. That is the cold you feel at your ankles.
Building people call it the thermal stack effect. It runs all winter, on every cold day, whether or not a single window is open.
Cornell Cooperative Extension puts a number on it worth sitting with: air leakage driven by the thermal stack effect can account for 40% of the annual heating costs of a typical home.
Not 40% of the drafts. 40% of the bill.
Three things follow from that, and none of them are obvious.
The colder it gets outside, the harder it pulls. The engine is the temperature difference between inside and out, so the stack effect is mild in October and ferocious in January, exactly when heat costs the most.
The taller the house, the stronger the pull. Three stories over a basement moves far more air than a ranch does.
Windows are not the main event. They get blamed because you can feel them, and a draft at eye level is where your hand goes looking. The volume moves at the top and the bottom of the house.
Which changes what you'd do first.
Seal the Top of the House Before You Insulate It
Image: The Home Wire
This is the part people get backwards, and it's an expensive thing to get backwards.
Cornell's guidance is blunt: insulating an attic does little to reduce heat loss unless the air leaks are found and sealed first.
Insulation slows heat moving through a solid. It does nothing about heat riding out on moving air, and air blowing through loose fiberglass drags that heat right past it.
So the order is seal, then insulate. Never the other way around.
The leaks at the top of the house, roughly in the order they matter:
The attic hatch or pull-down stair. It's a door in your ceiling, and most of them seal against nothing at all.
Recessed light cans. Each one is a hole in the ceiling with a fixture sitting in it, and an older non-airtight can leaks around the clock.
Wire and pipe penetrations. Wherever a cable or a vent pipe runs up into the attic, there's a gap around it.
The tops of interior walls. In an older house the cavity inside a wall can run clear from the basement to the attic, open at both ends.
Chimney and flue chases. These need a heat-rated seal, and spray foam is the wrong material.
Then do the bottom. The sill plate where the frame meets the foundation, and every hole drilled through the rim for a pipe or a wire.
One real caution before you seal anything. ENERGY STAR warns that tightening a house can make combustion appliances backdraft, which means a water heater or a furnace pulling its own exhaust into the house instead of up the flue.
If you heat with gas, oil or propane, or you have a gas water heater, put a working CO alarm in place first and have a pro check the draft after any major sealing work.
Move the Chair Off the Cold Wall
Image: The Home Wire
Here's a free one, and it works tonight.
You lose heat to a cold surface by radiation, the same way you feel warmth standing near a fire, just running the other direction. Sit three feet from a big window on a January evening and your body is radiating heat straight into that glass, whatever the thermostat says.
That's why a room can measure 70 F and still feel wrong.
So look at where the furniture actually sits:
Pull seating in off exterior walls and away from large windows. A couple of feet is enough to feel.
Put the reading chair on an interior wall if the room allows it. That wall has heated rooms on both sides of it.
Heavy curtains, closed at dusk, put a layer between you and the glass. Open them again when the sun comes round to that side.
A rug on a cold floor over an unheated basement or crawl space does more for how a room feels than another degree on the thermostat.
None of this fixes the house. It changes where you sit in it, which is most of what cozy actually means.
The $3.89 Kit That Goes Behind Every Switch Plate
Every outlet and switch on an exterior wall is a rectangular hole cut through the drywall into the wall cavity. The plastic cover plate hides it. It doesn't seal it.
On a windy day you can feel it. Hold the back of your hand near a switch on the windward side of the house and the air is moving.
The fix is a thin foam gasket that sits between the plate and the wall. The one we'd point you to is the Electrical Outlet and Light Switch Plate Gasket Insulator Kit, at $3.89 for 24 of them: 16 cut for outlets and 8 for switches, each 4 by 2.5 inches, in Volara foam and made in the USA.
The job runs about two minutes a plate. Kill the breaker, take the plate off with a screwdriver, lay the gasket over the box, put the plate back. There's no wiring involved and nothing you can get wrong, and it comes off cleanly later, which makes it a renter's job as much as an owner's.
We haven't lived with this kit ourselves. The specs and the price come from the retailer's own listing.
This is a small leak, and everything above says so. Gaskets on interior-wall outlets do nothing whatever, because there's no outside on the other side of them. And 24 gaskets will never move the number the way a sealed attic hatch will.
Buy it as the thing you do while you're waiting for a free weekend to do the attic. Not instead of it.
Links in this post may be affiliate links. The Home Wire may earn a small commission if you buy through them, at no extra cost to you.
What Sealing a House Is Actually Worth
Some numbers, so you can size this job against a Saturday.
ENERGY STAR puts the payoff from a full seal-and-insulate job at about 15% of heating and cooling costs, which works out to roughly 11% of a total energy bill. In its homeowner guidance it states the same thing more simply, as up to 10% of your annual energy bills.
That figure is for the real version of the job. The assumption behind it is a 25% reduction in the house's total air infiltration, reached by sealing the attic, the foundation, and around windows and doors.
The range moves a lot with climate. ENERGY STAR's own regional table runs from about 5% to 16% of whole-house energy depending on where you are and what you heat with. Cold and expensive lands at the top of that range. Mild lands at the bottom.
Two things are worth knowing before you budget for any of it.
It compounds with everything else. A sealed house is what makes a thermostat schedule work, makes insulation work, and lets a heat pump be sized correctly. An unsealed house undoes all three without telling you.
Sealing is cheap and insulating is not. Caulk, foam, weatherstrip and a weekend cover the sealing. Blown-in attic insulation is a contractor and a four-figure quote. Getting the order right is the entire argument.
If you only ever do one thing to this house, make it the attic plane: the hatch, the cans, and the holes around the pipes.
Why the House Goes Dry the Week the Heat Comes On
Chapped lips, static off the carpet, a wooden door that suddenly swings loose in its frame. It shows up every year within days of the furnace first running, and the furnace gets the blame.
The furnace isn't drying your air. The stack effect is.
Cold air holds almost no water. Air at 20 F outside can be at 100% humidity, soaking wet by its own standards, and still carry a small fraction of the moisture that 70 F air can hold.
Your house pulls that air in all day long. Then it heats it to 70 F. The amount of water in it never changes, but the amount the air could hold shoots up, so the humidity you'd measure collapses.
That's the whole mechanism. Winter dryness is outdoor air that has been warmed up.
Which means the leaks and the dryness are one problem too. A tighter house keeps the moisture you make from showering, cooking and breathing, instead of flushing it out through the attic all day.
A humidifier treats the symptom, and it's a fair thing to own. It's just working against a draft you could close.
That's Wednesday: one mechanism behind cold floors, stuffy bedrooms, a big slice of the heating bill, and January's static.
The five-minute version is to go stand under your attic hatch and look at the edges of it.
Forward this to whoever in your house says the thermostat is broken.
See you tomorrow.
The Home Wire
This post may contain affiliate links. The Home Wire may earn a commission if you purchase through our links, at no extra cost to you. We only recommend products we believe earn their place in your home.
{{address_text}}