Heat flows from warmer to colder—it’s a law of nature. So when it’s colder outside than inside, home heat loss is unavoidable. Even newer homes, built to stricter standards, lose heat. And older homes are likely to sustain significant heat loss, especially those over 40 years old.
However, there are measures you can take to reduce heat losses in just about any home, old or new. Read on to find out more about heat loss and what you can do about it.
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How Does a Home Lose Heat?
All homes lose heat directly through the foundation, roof, walls, ceilings, and windows. Warm air escapes through cracks in walls, ceilings, and floors. It disperses through openings in walls and ceilings around things like lights and switches. It also seeps out around doors and windows. Adding insulation and sealing gaps and cracks can reduce heat losses.
Heat loss occurs by several mechanisms: conduction, convection, and radiation.
One of the two main ways a home loses heat, conduction is where heat flows from a warmer material to a colder substance. The entire exterior of the house is in contact with another material—either air or the ground—which will suck heat out of the house if it is warmer inside.
All of the exterior parts of the house lose heat by conduction. Walls and roofs, windows, and doors contact air, which can conduct heat away. The house can lose heat directly through the floor into the ground and through basement walls if there is one.
Heat also flows from one area to another within a house, but it is contained and not lost to the outside.
Convection is the movement of air from a higher temperature to a lower temperature and is the other primary way your house loses heat. Warm air flows towards cold air through cracks and gaps, and warm air rises.
Your house is pressurized when the wind blows on one side of the house. It can force cold air in through cracks and gaps and force or suck warm air out on the other side. As a result, you lose heated warm air and have to heat the new cold air.
Some exterior components lose heat through convection, both direct and indirect. Much of the direct convective home heat loss can come from air leakage around poorly weather-stripped doors and windows. Another convective heat loss results from warm air escaping through cracks and gaps directly from the interior through walls or the roof.
Heat loss by convection from the house’s interior occurs when warm air leaks directly through openings around dryer vents, plumbing pipe, flue pipe penetrations in the roof and walls, vent fan exhausts, etc.
Significant convective heat loss results from warm air leaking into the walls from the interior, where it heats the exterior walls by conduction. The exterior walls then lose heat by conduction.
Interior leakage into the outer shell of the house can occur through gaps and cracks in walls, especially at joints; around switches, outlets, and lights, especially recessed lights; around the junctions between walls and window or door frames; and around any places where pipes or tubes penetrate walls.
The third way is radiation, which is how the sun sends us heat. Home heat loss from radiation is generally less than 10% of the total and is mostly through windows.
Heat loss through the different areas depends on too many factors to give overall numbers for each—the age of the house, the type of construction, the materials used, the climate, etc. But the best solutions are the same for avoiding heat loss, whatever the situation. The various solutions are detailed below.
Why You Want to Stop Heat Loss in Your Home
The two main reasons why you want to avoid home heat loss are money and comfort.
Heating a building is expensive, and lost heat is lost money. It is an ongoing extra expense that is avoidable. An investment in reducing heat loss pays back quickly in reduced heating bills, whether the heat is electric or from gas, coal, oil, or wood. There’s usually a reduction in the electricity bill, too.
Home heat loss is usually uneven throughout the structure. Some rooms are likely to be cooler than others, and some may be drafty. Some rooms may have to be overheated to produce comfortable temperatures in other rooms, so going from one to the other does not feel good.
How To Prevent Home Heat Loss Through Air Movement (Convection)
You can reduce convective home heat loss in several ways. Most you can do yourself; others might require work by a licensed contractor.
The easiest thing to do is find all the places where warm air can leave the interior and then seal them up. This process is called air sealing and requires a lot of sleuthing because there are many such places.
You can go around the house with a lit cigarette (whether you smoke or not) and put it close to the various places where things stick out of the walls and ceiling or are sunken into them and where surfaces join. If you see a movement of smoke towards those places or away from them, they leak.
Some places that lose the most heat are the openings around recessed lights, especially in the ceiling below the attic. You can buy gaskets for these lights as well as for electrical receptacles and switches.
Look at the edges (top, bottom, and sides) of all your doors to the exterior. You should weather-strip them if you can see the light coming through, including adding a sweep along the bottom. See if there is air movement around the door and window frames. There may be gaps between the frames and the walls that you can caulk with an acrylic latex caulk.
Check around pipes and ducts penetrating the bathrooms, kitchen, and laundry walls, including exhaust fans and the dryer vent. Caulk any gaps you find.
Whatever measures you take to make your house air-tight, ensure you have adequate ventilation to maintain a healthy environment.
Look for holes and gaps around the house’s exterior that you can caulk to prevent wind from blowing into the structure.
How To Prevent Your Home Heat Loss Through Conduction
The better-insulated walls, floors, and ceilings are, the less heat you will lose from conduction. You may be able to install insulation yourself if you have an accessible attic, crawl space, or basement. However, putting insulation in walls is likely to be a bigger job.
You can buy fiberglass batts that fit snugly between the floor joists under the house or ceiling joists in the attic.
Insulation must be in complete contact with all five sides of the structure under and around it, which is not easy to do, especially if there are pipes or wires in the way. As a result, improperly installed insulation will significantly reduce efficiency; even minor defects make disproportionate reductions in efficiency.
Before you install the batts, though, you should fill any holes around pipes and wires with spray foam and cover large openings like the one under bathtubs with a rigid material sealed around its edges.
Replacing old insulation is a good idea, too, since the insulation may have settled and lost much of its effectiveness.
If you have a basement, you can insulate the walls and floor with a rigid foam board and cover the foam boards on the floor with plywood.
Insulating exterior walls is a bigger job. However, if you have an old house with no insulation in the walls, you can have a professional spray foam insulation through small holes into the walls. Although expensive, professional spray foam application will make a big difference in reducing heat loss.
Otherwise, it is a major surgery to open up the walls to install insulation and a big deal to add it to the exterior somehow. So you would generally only do it as part of a significant remodel.
Replacing older doors and especially windows can reduce heat loss significantly. This kind of investment not only saves money by reducing heat loss but it makes your home more aesthetically pleasing and comfortable.
Although heat loss is unavoidable due to the laws of nature, you can reduce it. First, you can reduce heat loss by sealing up all the cracks and gaps where you can lose warm air.
Or, you can add or replace insulation in accessible areas to reduce heat loss. Both of these solutions are cost-effective, and most people can do them.