Getting a Maryland House Ready for Cold Weather

Schedule the heating tune up while the weather is still mild. A heating system that has sat idle since March is an unknown. Burners get dirty, flame sensors film over, ignitors weaken, blower wheels load up with dust, and heat pump defrost boards fail quietly in a way you will not notice until the first cold morning. Finding that in October means a scheduled repair on an ordinary weekday. Finding it in January means a no heat call on the coldest night of the year.

A real heating check is more than a filter swap. On a gas furnace it includes a combustion analysis, which measures what is actually coming out of the burner and is the only reliable way to catch incomplete combustion before it becomes a carbon monoxide problem. On a heat pump it means verifying the defrost cycle and the reversing valve, because a heat pump with a failed sensor will run expensive electric backup all winter while still keeping the house warm enough that nobody investigates.

Put in a new filter before heating season starts, then keep to a schedule instead of guessing. A one inch pleated filter in a normal house is a sixty to ninety day part. Media filters four or five inches deep usually go six to twelve months. Pets, carpet or a wood stove shorten those intervals. A loaded filter starves the blower, which raises static pressure across the system, and a gas furnace responding to that runs hotter than designed and can trip its high limit switch repeatedly.

Match the filter to the equipment rather than buying the highest number on the shelf. A very restrictive filter in a system not designed for it does more harm than a cheap one, because the airflow it costs shows up as lost capacity. Check that the arrow on the frame points toward the furnace or air handler. Then look for gaps around the filter slot, since air that slips around the filter is air the filter never cleaned.

Then walk the house and open the supply registers and clear the return grilles. Closing vents in unused rooms does not save money on a system sized for the whole house. It raises static pressure the same way a dirty filter does and pushes more air out through every duct leak. Furniture, area rugs and floor length curtains block registers as effectively as a closed damper. Returns matter even more than supplies, because a system that cannot get air back cannot deliver air out.

Clear a two foot working space around the outdoor unit before the leaves finish falling. Rake out what has piled against the coil, cut back shrubs and ornamental grasses, and move the trash cans and the firewood. If the unit sits under a roof edge with no gutter, that is where an ice sheet forms, and a falling one can bend the fan guard or flatten coil fins. Raising the unit on a taller pad is a reasonable fix in a house that has that problem every winter.

Here is the part people get wrong. A central air conditioner outdoor unit does nothing in winter, so a cover is harmless if you like the look. A heat pump outdoor unit is your heat source in winter, and it must never be covered, wrapped or boxed in. It has to move air across the coil and shed the water it produces during every defrost cycle. Covering it restricts airflow and traps moisture where it freezes. If you are not sure which one you have, leave it uncovered.

High efficiency furnaces and heat pumps both produce condensate, and that drain line freezes more often than people expect. A ninety percent plus furnace makes several gallons of mildly acidic water a day, and if part of that line runs through an unheated crawl space, a garage, or out through the rim joist, a hard freeze can plug it with ice. The system then backs up, hits its float switch and shuts down overnight. Insulating the exposed run and keeping the outdoor termination clear of mulch and snow prevents most of it.

Give the water lines the same walk. Look for supply piping along an exterior wall, in a crawl space, in an unheated garage, or inside a kitchen cabinet on an outside wall, and insulate what you find. Disconnect and drain every garden hose in the fall. A hose left attached to a frost free hose bib defeats that design, because water cannot drain past the valve seat, so the freeze happens inside the wall.

Before you leave for a week in January, set the thermostat back, but never shut the heat off. Fifty five degrees is the common recommendation and it is a good one. The heat while you are gone is not there for your comfort, it is protecting the plumbing inside the walls. Interior air temperature and the temperature inside an exterior wall cavity are very different numbers, and a house holding fifty five in the hallway can still have pipes in the low thirties behind a poorly insulated wall.

Do the rest of the trip prep too. Open the cabinet doors under sinks on exterior walls so warm air reaches the supply lines. Leave interior doors open so the system can move air through the house. Ask someone to look in every couple of days, and make sure that person knows where the main water shutoff is. If you have a smart thermostat, set a low temperature alert on your phone. That is the cheapest freeze insurance available.

Carbon monoxide detectors are the one item on this list that is genuinely about survival, and winter is when they matter most, because combustion equipment runs hardest and houses are sealed tightest. Put one on every level and near the sleeping areas, and press the test button monthly to check the horn and the circuit. Detectors themselves expire: most sensors are rated for five to ten years from the date of manufacture, not from the day you hung it. Replace the whole unit when that date comes due.

A hard freeze with the power out is worth planning for, because gas furnaces and boilers both need electricity for controls, ignition and the blower or circulator. If the outage looks long, open the sink cabinets, run a thin trickle of cold water at the fixture farthest from where water enters the house, and gather everyone into one room. Never heat a house with a gas range, a charcoal grill or an unvented outdoor heater, and never run a generator in an attached garage.