Your introduction to thermal bridging

| by Laura Dwyer
Your introduction to thermal bridging

Have you ever sat next to an old style aluminum window on a cold day? Or sat on cold metal bleachers at a fall football game? You've experienced thermal bridging.

Basically, heat moves from warm areas or materials to cold areas or materials. Like in and out of a home. You can't stop it, but you can slow it down a lot.

The insulation in a home is like a thick winter coat. It helps keep the warmth inside the home. But with most traditional frame construction styles, the coat has holes in it.

Warm air looks for ways to escape to the outside of the home in the winter.

No matter how much insulation you put in the bays between the studs, the heat moves through the wood studs and sheathing because the un-insulated wood is a bridge between the inside and outside of the home.

You can sometimes see the effect in a roof on a cold winter morning. If the attic is not insulated and sealed properly, you can see the lines of the roof trusses under the shingles. The trusses are warmer than the roof because they conduct heat through the wood under the shingles, melting any frost or snow.  In extreme cases, you may see it inside a home on dry wall. It's called ghosting, when you see stripes left when the wall framing gets cold, leading to condensation that attracts dust to the wall. Eventually faint vertical stripes form over the cold and wet wall studs.

In the average frame home, up to 25 percent of the wall surface is actually wood studs. So even if you put a high level of insulation in the walls, about a fourth of the wall actually has a very low R-value, in the 2 to 4 range. That's like leaving one wall un-insulated.

Modern building science and building codes recognize this flaw in the wall and are calling for continuous insulation.

Every home – new or existing – can increase its energy efficiency by including a high-quality WRB and a blanket of continuous exterior insulation over the walls and studs to help reduce thermal bridging. This keeps the conditioned air inside the house and outside air out, so homes can stay cool in summer and warm in winter and more comfortable year round. Continuous exterior insulation, such as DuPont™ Tyvek® ThermaWrap™ R5.0, complements the batt or spray foam insulation found between the studs.

Continuous insulation can help qualify homes under the ENERGY STAR® Qualified Homes program and other green home building programs. Tyvek® ThermaWrap™ R5.0 as a continuous insulation, can be used as part of a compliance package to meet energy codes that are currently adopted.

To meet these new requirements, DuPont launched Tyvek® ThermaWrap™ R5.0. This easy-to-install continuous insulation solution combines 1 1/2-inch-thick insulation, made with a mixture of polyester and polyolefin fibers with Tyvek® HomeWrap® the industry’s leading brand of water-resistive barrier. As a result, Tyvek® ThermaWrap™ R5.0 adds a continuous R-value of 5.0 to the exterior of the home and serves a breathable an air and water barrier which can help to further reduce energy usage while the improving the durability of the home.

Of course, energy savings in a particular home will depend upon many factors, including but not limited to: climate zone, house size, number of windows, energy use habits and so on.

Learn more about the fight against thermal bridging and continuous insulation.

Topics: Insulation, Thermal Envelope

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