Cooking puts a lot of water vapor into a St. Louis kitchen. Boiling pasta, simmering soups, and running the dishwasher all release moisture, and frying adds grease to the air as well. A range hood is meant to pull that steam and smoke out of the room before it spreads to cabinets, ceilings, and the rest of the house. When the hood is weak, disconnected, or venting into the wrong place, the moisture stays put and shows up later as stains and peeling paint.
Find out where the hood vents
Range hoods work in one of two ways. A ducted hood pushes air through a metal duct to the outside. A recirculating hood pulls air through a filter and sends it back into the kitchen. A recirculating unit does little for humidity, since the water vapor stays in the room. Check the owner's manual, or look at the top or back of the unit to see whether a duct connects to it. If you cannot tell, follow the duct into the attic, a soffit, or a wall, and look for a vent cap on the outside of the house.
Check that the hood actually pulls air
Turn the hood on high and hold a tissue or a thin strip of paper near the front edge. It should be drawn firmly toward the opening. If the paper barely moves, the fan may be weak, the filter may be clogged, or the duct may be blocked.
- Clean or replace grease filters. Grease buildup slows airflow and coats the fan.
- Look for loose duct joints in the attic or crawl space. Tape or clamps should hold each joint tight.
- Check the outside vent cap. The flap should open when the fan runs and close when it stops. A flap stuck shut, or clogged with lint and debris, blocks the exhaust.
- Listen for rattling or a fan that sounds strained. Both can point to a bent blade or a motor that needs attention.
Signs the kitchen is holding moisture
- Stains or soft spots on the ceiling above the range, or near an exterior wall.
- Paint that bubbles or peels around the top of cabinets or along window trim.
- Condensation on kitchen windows during cold St. Louis mornings.
- A greasy film on cabinet doors and on the wall behind the stove.
- A musty smell that lingers in the kitchen long after dinner is over.
Habits that help during cooking
Turn the hood on before you start heating water, and leave it running through the cooking and for a while after the burners are off. Use lids on pots when you can, since they keep steam in the pot instead of the room. If you run the dishwasher or the dryer at the same time as cooking, the house has more moisture to move, so let the hood run longer.
Make-up air in tight kitchens
Many well-sealed homes in St. Louis resist a strong hood because the exhaust has no air to replace it. Signs include a whistling sound at the window or door, a hood that seems weak only when doors are closed, or a draft that pulls back into a nearby fireplace or water heater flue. Cracking a window a little while the hood runs can help. If you notice fumes, or a gas appliance seems to draw air down its flue, turn the hood off and have the appliance checked promptly.
When to get help
If the duct runs through an attic with no insulation, if the vent cap is hard to reach, or if the hood is loud and still moves little air, a homeowner should consider a professional check. Ask whether the fan is sized to the stove, whether the duct is smooth, and whether its route can be shortened. Also ask about combustion safety if there are gas appliances nearby.