Replacement Windows for Improved Energy Efficiency: A Walk-Through Case Study

Premier Inspection’s real estate inspectors Travis Hill and Bryan Hughes are often asked by friends and acquaintances to assess their homes and suggest the best ways to address whatever issues there might be. This is a story about one of those inspections.

During our walk-through, I encountered 12 single-glazed, aluminum-frame horizontal slider windows of 1970s vintage—not the best from a comfort or energy standpoint, but their factory finish is still in pretty good shape, and they’re fitted with screens and storm sashes. The exterior caulking around the frames is fairly worn out and cracking.

On our way inside, I noticed that the soffit panels at the eaves have all been taken off. I saw that the underside of the sheathing is water-stained. I’ll bet there was leaking from rain, and it’s ruined the soffits. They already had a new asphalt shingle roof put on.  I hope they flashed the eaves against leakage caused by moisture.

Looking at the windows from inside, We found some evidence of moisture infiltration around the jambs and sills. Was the source the damaged caulk?  Inadequate flashing in the original installation?  Leaks from moisture?

Better windows are available these days. In our market, it would probably cost him about $500 apiece to replace the sliders with vinyl low-E, gas-filled units. There’s also a big combination unit with fixed glass and double-hungs on the front of the house; replacement would cost about $2,000. But would replacement windows—properly installed—actually improve comfort, and preserve or add value to the house?

While mulling that over, we went into the living room to look at the sliding glass patio doors. They’re much newer than the other windows, as they have aluminum frames and insulating glass. They’re in great shape, but the sheer size of the glazed area explains why the house is so chilly in winter.

Premier Inspection’s advice to is this:

  • It wouldn’t make much sense to replace the horizontal sliding windows throughout the house. While they’re old and only single-glazed, they’re fitted with storm sashes, so their energy performance is roughly comparable to double-paned glazing. We have concerns about the evidence of moisture infiltration around the windows, but our guess is that the new roof may have corrected the problem. We would, however, renew the exterior caulking, and fill and paint the interior finished openings, as well as keep an eye on them to see whether evidence of moisture intrusion returns.
  • It wouldn’t make any sense to replace the sliding glass doors in the living room with new ones of comparable size. It would cost about $5,000 to upgrade them with doors with gas-filled glazing, and that would improve the energy performance from R-2 to R-4, but it would result in only a very small improvement in comfort, and probably no reduction in energy costs.
  • Finally, Premier Inspections would invest in thermal drapes for the living room and elsewhere to help keep his college grad and her roommates more comfy.
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