Air sealing and insulation of walls and roofs are top priority in your energy retrofit project. Windows and doors, which can easily be a complex agenda, are the next priority in your home’s energy improvement plan.
For a window to perform its functions of ventilation, light transmission, security, a view on the world and aesthetic appeal, two main criteria come into play for optimum performance: infiltration and insulation. Of the two, tackling infiltration with good air sealing is the first priority item. Using this principal again, like you did when you upgraded your homes envelope, can have a considerable impact on reducing the cost of your retrofit project. Windows, being considerably colder than the adjacent insulated walls, chill the air and create cool convective air flows. These air currents can be very uncomfortable to sit or lie next to. You can increase the insulation value of your current window openings for more comfort. However, this does not necessarily equate to a dramatic reduction in your homes heating load.
To repair or to replace? Replacing an existing window can be very expensive. Dealing with exterior trim and siding, interior trim and wall finish can easily bring total material/labor costs in the range of $1000-$1500 per opening! Only when window components are seriously deteriorated, such as rotted sash, jambs or sills, will this course be practical.
With insulated sash, if condensation or fogging is now taking place, you may be able to get by with just replacing the sash.
Repairing the existing sash, painting, weather stripping and applying new operating hardware can bring you in the $200-$300 range per opening. Adding a new set of storm windows to single pane glass windows, which can offer sash protection, a stored in-place screen, can add another $200 to the package for a total effective energy upgrade of roughly $200-$500. This means you seal the drafts, provide for easier summer ventilation and maintain the original design elements of your home. I have done blower door tests on upgraded windows with new storms and weather stripping and have found air leakage to be minimal. Their total insulating value is fairly close to regular insulated glass units, in the R2-3 range. Newer triple pane insulated units can approach R8, but adding interior Window Quilts or insulated cellular shades can add another R4 to your window package at about $200-$500 per opening. This way you can maintain original architectural or historical design elements, obtain a more comfortable interior climate, and reduce heating loads for generally less money. In other words, a shorter payback period on your investment.
Without a doubt, new window units that have low maintenance features can be very appealing, but they come at considerable cost. Most of the time, total window replacement runs 1 1/2 to 2 times the expense of existing window repair and upgrade. Sash repair can also be especially important for historical preservation in older homes. It also has the added benefit of reducing the amount of material that ends up in the landfill.
Doors fall into the same evaluation process. For such a small opening in the homes envelope, weather stripping can be very cost effective.