Ice dams, frost on the sheathing and a furnace that never rests all trace back to the attic floor. We seal it first, then insulate it to depth.
Tell us what the Des Moines property is doing and we'll take a look.
Warm air rises. In a house that is 22 F outside and 70 F inside, which is a normal January afternoon here per NOAA's 1991-2020 normals, the pressure difference pushes indoor air up through every opening in the ceiling plane: top plates, plumbing and wiring chases, recessed lights, the bath fan housing, the attic hatch, the gap around the chimney. That air carries heat and moisture into the attic. The heat warms the roof deck and melts snow. The moisture condenses or frosts on the underside of the sheathing.
This is the mechanism behind the metro's ice dam problem. The Building America Solution Center describes it directly: "When heated air from the house escapes into the attic, it can warm the underside of the roof deck, melting the snow on the roof above," and the melt "runs down the roof until it reaches the cold eaves where it refreezes." With about 36.5 inches of snow in a normal Des Moines season, there is plenty of raw material.
Adding insulation without sealing the floor helps some but leaves the leaks open. The same source calls air sealing "the most important step." University of Minnesota Extension says the same: "First, make the ceiling air tight so no warm, moist air can flow from the house into the attic space." We follow that order.
We start in the attic with a light and, in cold weather, an infrared camera. Frost lines, dirty insulation (a sign of air moving through it) and dark staining show where the leaks are. The existing insulation is raked back from those areas. Top plates get a bead of foam; chases and large openings get rigid foam or sheet metal with foam around the edges; recessed lights get airtight covers rated for the fixture; the bath fan gets a sealed housing and an insulated duct to the exterior. The hatch gets a gasket and an insulated cover.
Then insulation goes to depth. Iowa's energy code benchmark for new homes is R-49, which is roughly 14 to 16 inches of blown cellulose or fiberglass depending on the product. Baffles at the eaves keep the soffit vents open so the attic stays cold and dry, which is the third leg of ice dam prevention. If the attic has knee walls, a story-and-a-half layout or a finished room, the scope will show how each transition gets handled; those are where most retrofits fall short.
Where the attic is too shallow to reach R-49 with loose fill, or the roofline is finished, closed-cell foam on the underside of the deck converts it to an unvented assembly. That is a different design and the scope will explain the trade-offs before you choose it.
Nearly half of the city's housing units were built before 1960 according to the Census Bureau's 2024 American Community Survey. Attics in those houses tend to have shallow, settled rock wool or cellulose, open balloon-framed wall tops you can drop a tape measure down, chimneys with a gap around them, and sometimes knob-and-tube wiring. Knob-and-tube must be inspected by an electrician and either de-energized or confirmed safe to cover before insulation goes over it; we will not bury live knob-and-tube and neither should anyone else.
These attics reward careful work. Closing the wall tops and chases alone changes how the house feels on the second floor, and once the floor is tight, the insulation on top actually performs at its rated value.
Once the attic floor is sealed, attic ventilation is there to keep the roof deck cold and carry off the small amount of moisture that still gets through. Soffit intake with ridge or roof exhaust is the usual arrangement; the scope will note if the house lacks intake or has blocked soffits.
Inside the house, sealing the ceiling means humidity from cooking, showers and people no longer escapes into the attic. Bath fans must exhaust outdoors, not into the attic, and a tight house may need a set schedule of fan run time. We put that in writing so you know what changed.
Questions
Because the existing insulation is not stopping air. Loose fill on a leaky ceiling filters warm air on its way to the roof deck. Sealing first is what makes the added depth pay off and what actually addresses ice dams and frost.
Yes, and winter is when the leaks are easiest to find: frost and melt patterns on the sheathing and snow melt patterns on the roof point straight to them. Cold weather affects foam application, so the crew manages material and substrate temperature accordingly.
Attic ventilation stays in place and is often improved. Eave baffles keep the insulation from blocking soffit intake, and if the house lacks adequate intake or exhaust the scope will say so. Ventilation is the third part of ice dam prevention after air sealing and insulation.
Reducing air leakage and adding insulation reduces the heat your furnace has to replace. How much depends on how leaky the house was, how you heat it and how you live in it, so we do not quote a savings percentage. We will show you the specific leaks we found and closed.
Tell us what the house is doing and we will come look at where the heat is going.
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