With winter rolling in, plumbing and heating expert Richard Trethewey and home technology expert Ross Trethewey explain cost-effective ways to save money on heating to Kevin O’Connor.
After presenting the tendencies and physics of heated air, Richard and Ross discuss the importance of insulating the roof of a home.
3 Tips to Help You Save on Your Heating Bill
Tip 1: Heated Air is Predictable
Specific physics applies to heated air. First, it wants to move upward, often finding its way through the roof. Also, heated air will always move toward cold air, and the colder the air, the more it wants to move.
For instance, if it’s 70 degrees in the home but only 15 degrees outside, heated air will work even harder to escape through the top of the building. It can also try to escape through the walls.
Pro Tip: As Tom Silva, general contractor on This Old House, explains: “No matter how you deliver heat into the building, it wants to move its way upwards. A hot air balloon will lift. And that’s the same thing that happens inside the house.”
According to This Old House Magazine, cold air moving into a house and warm air exiting account for most of the heat a house loses. Sealing the pathways with caulk, foam, or tightly packed insulation is the first and most important step in lowering heating (and cooling) bills; filling walls and attics with insulation also reduces the amount of heat lost through conduction.
Tip 2: Insulate from the Top Down
Since warm air rises, you need to trap it in the home. Putting a warm hat on the building by insulating the attic is key. Fiberglass, rigid foam, and bubble pack insulation are great for the job. Just be sure that all the insulation is correctly in place, especially after any retrofit work might’ve occurred.
While many folks are satisfied with insulating between the floor joists in the attic, it’s not the best place. This is often where the heating and cooling mechanicals are, and leaving the attic space itself uninsulated makes it harder for them to work efficiently. Instead, consider insulating the roof itself.
Seen on a This Old House Project: During one project, the team found an HVAC system living in an uninsulated attic with 2×6 rough framing and no insulation. Richard Trethewey went up with a thermometer, and it was 120 degrees and climbing. In winter, the reverse is true — it’s freezing up there. That means the system is working overtime all year long, simply because no one insulated the roof when the space was converted.
Technique Tip: If you’re adding a second layer of insulation over existing batts in your attic, always use unfaced batts — either buy them unfaced or peel off the paper backing. Place the new layer perpendicular to the old one to cover any gaps in the lower layer. Never lay heavier batts, such as cotton, over lighter ones like fiberglass, as you’ll compress the lower layer and reduce its effectiveness.
Tip 3: Air Sealing is Just as Important as Insulation
There is a difference between insulating and air sealing, and when it comes to trapping heated air in, air sealing is critical. Issues like gaps between window panes, gaps under exterior doors, and even the space around an outlet in an exterior wall can allow cold air to penetrate the home while warm air pours out. A ¼-inch gap between window panes can equal as much as a hole the size of a baseball in an exterior wall. For ½-inch gaps under doors, that area can equal as much as a hole the size of a softball.
For leaky windows, installing new sash locks can help pull things tighter, but installing a shrink wrap kit around the window can help trap air and create a lot of insulation. Consider installing weather stripping around the side for doors with gaps and a door sweep at the bottom. For outlet or switch boxes in exterior walls, caulk around the gap between the box and the drywall to keep heated or cold air from passing through.
A Few Words of Caution
Many folks choose to shut heating zones off to save money during the winter. While this can be effective, pay attention to things that freeze within the space. Insulate any pipes in the unheated room or drain the pipes in completely unused areas to prevent freezing and splitting. Also, don’t forget to keep any radiators or heating vents clear from furniture to allow the mechanicals to heat the space efficiently.
A Cautionary Tale: This Old House Magazine recounted a memorable disaster where homeowners turned off the heat while away in winter: “The water was frozen, like a Niagara Falls of ice. We had to chip away at it for 20 minutes before we could even get to the door. The owners had turned off the heat, and the radiators had frozen and then split open.” The lesson? If you’re away in wintertime, keep the heat low—at 50 or 55 degrees—but don’t shut it off completely, especially if you don’t have good insulation.
