The coldest weather of the season has brought a real taste of winter to Iowa, and an energy-company spokeswoman says many people are thinking about winterizing their homes. Jan Zimmer with Aquila Energy says even if you’ve closed storm windows and checked the insulation, another way to warm up inside may be a matter of design. Just being sure the furniture is away from cold-air returns, so air can move around inside the home. In addition to keeping air vents clear and clean, many people add weatherstripping and check for leaks that can cause drafts. But with today’s high-efficiency insulation and tight home construction, Zimmer says your home may be buttoned-up too well. You want it tight to keep out winter cold, but the home does need some air coming in, especially if you have appliances that burn natural gas or propane. That stove, water-heater or other appliance will use oxygen, and Zimmer says proper ventilation could be a matter of life and breath. You want enough air to support that combustion, because without enough there’s a risk of carbon monoxide. Something clogging an appliance vent could do it, she says. Just like smoke and C-oh-two detectors, there are devices for the home that will sense a buildup of carbon monoxide and warn you. Zimmer says the detectors are available at most any hardware of home store.