Your home is basically just a big box that you want to keep the air inside a certain temperature. Heat always moves from warm to cold. So, in the Winter heat is flowing OUT of your home. The amount of heat flow is determined by the difference in temperature inside and outside and the thermal properties (insulation) of the structure.



Your walls usually do a pretty good job of reducing the heat loss. Walls have and inner air barrier (sheetrock), and outer air barrier (sheathing) and typically filled with wood studs and insulation to minimize air infiltration and heat flow outward.

The problem occurs in the attic. We still have the inner air barrier (sheetrock ceiling) and insulation (usually blown-in fiberglass or cellulose). However, most homes do not have an outer air barrier on top of the insulation above the ceiling. This is like taking the outer layer off a Winter jacket. With a little wind, the jacket becomes almost useless due to air movement inside the insulation.

So, how does a radiant barrier help in cold climates? Two ways: 1) Reduction of radiant heat loss & 2) Minimizing convective air looping inside the insulation.

By laying radiant barrier foil across your existing attic insulation, it works off the emissivity quality of pure aluminum. This is similar to wrapping a potato with foil to keep it hot. The stored heat in the potato is not easily converted to radiant energy.

The other benefit of installing a radiant barrier in cold climates is to reduce convective airflow inside the insulation. In a standard attic, the insulation is “Open” to the cold air inside the attic. The effectiveness of the insulation is greatly reduced since cold air is heavy and dense. The cold air will “fall” down through the attic insulation. Warm air close to the ceiling will rise and the result is a ‘convective loop” of air pumping through the attic insulation.

By installing radiant barrier over attic insulation it acts similar to the outer wind layer on a jacket. Air movement will be reduced resulting in higher r-value performance of your home insulation.

It is important to use a perforated radiant barrier to allow moisture in its vapor form to pass. Otherwise moisture can condense on the bottom of the foil and lead to wet insulation, mold and possibly wood rot. Make sure the ceiling is also sealed airtight. Holes from lights, and other fixtures can leave a path for warm-moist air to get into the insulation. This can result in moisture inside the attic insulation. It cannot be emphasized enough to use a perforated radiant barrier attic foil in cold climates.

Comfort is another reason to install a radiant barrier. By keeping heat from escaping, your home will feel consistently warmer from room to room. This will reduce your need for heating and save you money on your Winter heating bills.

Winter is the best time to install a radiant barrier either as a do-it-yourself project or to hire a professional installer.