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Q: We live in a late-1950s four-level split home, and for the 15 years we've been here, we have fought the cold chill that the main bathroom, which has a window in the bathtub wall, creates in the house. The porcelain tub and tile are original to the home. The window is updated, and we keep the shade pulled; we weren't sure how else to cover a window that's inside a shower. The tub and tile are so cold in the winter that when our children were little, we would drain the hot-water tank trying to warm the tub first so they could take a bath. The cold from the tiles and tub chills the room and hallway, too. The bathroom is four steps up from the kitchen, and the thermostat is located just outside the bathroom door. The room is too small to reconfigure. Any ideas for how to make this room more comfortable and energy-efficient?

A: It’s not uncommon to have a bathtub on an outside wall with a window above. Before bathroom fans became standard, a window there might have seemed like a good way to get steamy air out of the room after a shower. But a window in a wall with a shower is very prone to leaking. Windows are designed to keep out rain from the outside, but on a shower wall, spray can also blast the inside. Covering the window with a shade when someone is showering helps prevent water from getting into the trim and eventually rotting out the wall. Stick to that, even if you find better ways to make the room more comfortable.

Fixing the underlying problem will probably involve calling in a contractor who uses a thermal scan to pinpoint areas where cold air is leaking or insulation is lacking. But you might want to start by doing some sleuthing with a thermal-imaging camera, which you can borrow from the library at no charge and hook up to your smartphone. Montgomery County Public Libraries lends Flir thermal-imaging cameras, some for iPhones and some for Androids, to patrons 14 and older who have a library card. Many other public libraries have similar programs.

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Do the scan when there is at least a 20-degree difference between inside and outside temperatures. As you aim the camera at the room from outside and then repeat the scan inside, you’ll see hot spots show up as yellow, moderate areas as red and cold areas as purple. You might discover that the wall behind the tub is a big block of purple or yellow, depending on the season when you scan. That could indicate that the wall behind the tub is open, with nothing to stop cold air from blowing through. Or, if your house is like a lot of split-levels, with a garage tucked under living spaces, you may see purple or yellow on or near the floor on the wall shared with the garage, a tip that insulating the garage ceiling and sealing it against drafts could make your bathroom warmer in winter.

Of course, a professional who does scans frequently and understands building systems will probably see things you might not. For $100, Maryland residents can arrange for an energy audit through their utility company, which will probably include a thermographic scan, advice about how to seal air gaps and improve insulation, and a list of participating contractors who can do the work.

Improving insulation in a bathroom without ripping out your vintage tile and tub isn’t simple, however, and might not be possible. Seek out a contractor who works on vintage houses and strives to keep period touches. Perhaps it’s possible to insulate the wall with the window by going in from the outside.

If addressing the underlying problem is not feasible without remodeling, consider adding a heater to the room. Whether it will save energy depends on what you’re comparing. If you’re still draining the hot-water heater to prepare for a bath, you might come out ahead.

The least-expensive heating solution is a portable space heater, but look for one with a safety plug designed to cut off power almost instantly if there is a short — a concern whenever an electrical appliance is used next to water. For the plug’s protection to work, your bathroom outlet would need to have a grounded neutral wire. A house built in the 1950s might not have that, but you could probably add it by updating a two-prong outlet. This Old House gives good instructions; do a Web search for “Changing a Two-Prong Outlet to Three.” Lasko’s small portable ceramic space heater ($30.88 on Amazon) has a safety plug and other features that make it especially suitable for a small bathroom. It’s set to turn off after an hour, and it’s compact: eight inches tall, with a base just over six inches by six inches. You could set it on the floor, a counter or even a shelf.

Or you could install a heater on the ceiling or wall. If you already have an exhaust fan, it’s fairly simple to replace it with a unit that also provides heat. If you don’t have a fan, this might be a good time to install one (as a combination unit that includes a heater, fan and light). Vent to the outdoors, not into your attic, and buy a model sized for your bathroom. The Broan-NuTone 659 heater, fan and light combo, which is designed for bathrooms up to 45 square feet, is $123.05 on Amazon.

With a wall heater, the big issue in a small bathroom is finding wall space that isn’t covered when the door is open. The most compact wall heaters have a heating element and a fan covered by a grill; they tuck into the wall, using the space between studs. The Broan-NuTone 174 wall heater, with a grill about nine inches high and 12 inches wide, is $93.23 on Amazon. There are also panel-type heaters that work by convection or radiant heat, but they tend to be much bigger and harder to incorporate in small bathrooms.

Heated towel bars also add warmth, but they tend to be too large for small bathrooms. One relatively compact model, Ancona’s comfort dual six-bar electric hardwired and plug-in towel warmer ($387.79 at Home Depot) is about 20 inches wide and 31.5 inches tall. If you were remodeling the bathroom, you could install a heating system under the flooring. A remodeling-free alternative, if you have tile or stone on the floor, is to replace the bath mat with a heated mat, such Cozy Products’ Super Foot Warmer. It’s 36 by 16 inches and is available at Home Depot for $50.49.

Also: Try taking bubble baths. The air trapped in bubbles acts as insulation, helping to keep the water warm longer.

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