If you are not replacing windows there is still plenty you can do to increase your current window energy efficiency. Apply a low-e film to your existing windows
. Although Low-E coatings are usually applied during the manufacturing process, some are available for do-it-yourselfers. These films are inexpensive compared to total window replacements and have a useful life of 10–15 years. Reduce the air leakage around your current windows
. Most heat is lost thoguth convective heat loss -- leaks. By plugging all holes with caulk or using weather stripping on window sashes or other things that move (window sashes, doors), you can substantially reduce the amount of air infiltration and leakage around windows. See our Article Insulation and the Building Envelope: Controlling Heat Loss and Gain
for a full discussion of caulking and weatherstripping.
By being a bitmore radical without opening walls can have a big impact: for example, removing shoe molding or baseboards to seal all joints between the floor and wall wiht stop a substantial amount of leaks. Also, many old brownstone windows are surrounded by lovely wooden decorative moldings and often there is no insulation between these moldings and the sheathing. It is possible to have a carpenter remove, in tact, units of molding so that insulation can be placed or blown into cavities and then the molding replaced.
It also may be possible, depending on your window sash depth and the overall state of your windows, to take your existing old brownstone windows to a window fabricator who can use the original sashes and add an additional pane of glass, low-E coating and argon or krypton gas. This may be substantially more expensive than simply caulking and weatherstripping and/or adding storm windows, but it may be less expensive than complete replacement particularly if you have true mullioned divided lights or huge floor-to-ceiling parlor floor windows often found in brownstones, and you will keep your historic windows and will have a higher-end look than weatherstripping and storm windows may yield. Install Storm Windows
. Storm windows are a viable option even in historic landmarked areas because they are available to install on the inside as well as the outside of windows. Storm windows do not increase the insulating properties of single pane windows but they prevent air leakage and seepage and consequently reduce draughts, increase comfort and will help reduce heating costs. They range from the inexpensive plastic sheets or films designed for one heating season, to triple-track glass units with low-e coatings meant to be used for many years. The panes can be of glass, plastic such as plexiglass or acrylic. Glass provides greater visibility and does not deteriorate with age so will have a longer life but it is more fragile, whereas plastic options are lighter and stronger but may discolor and scratch. Interior storm windows are easier to install and remove and are better at reducing air leakage and infiltration than exterior storm windows because they make a tighter seal. Exterior mounted windows should be installed with a small “weep” hole at the bottom to allow moisture and condensation to escape, and although this reduces the energy efficiency it is necessary to avoid a moisture build that will cause a wooden exterior window frame to rot over time. Framing options present all the choices discussed earlier in this Article
under frame choices for new windows. Window Treatments
are not just for show. The right kind of window treatment, used properly, can dramatically affect heating and cooling loads. Window coverings will, of course, reduce the amount of light transmitted into the room and therefore may increase the need for artificial light thus reducing energy savings. You can also combine window treatments to increase insulating properties. Shades, Blinds and Draperies
can be quite effective in keeping the heat in or out. Honeycomb shades, for example, which consist of honeycomb-shaped pockets (one, two or three cells deep) that trap air and act as an insulating barrier, typically have R-values in the range of 3.0 to 3.9 and should be inside-mounted for greatest insulation. The Department of Energy notes that honeycomb blinds reduce air infiltration only slightly, however our personal experience with honeycomb blinds is that they make a noticeable improving in reducing draughts thereby increasing room comfort, and they substantially reduce solar heat gain in the summer which is key in those top floor south-facing brownstone bedrooms! Draperies should be mounted close to the window. Blinds do not help greatly with retaining heat but can help reduce solar heat gain in the summer. Blinds and shades can also be made with special liners to make them more or less reflective of solar heat. In winter coverings should be open during the day when the sun is shining on that side of the house to allow solar heat to enter, and closed at night; in summer do the opposite and close shades during the sunny part of the day. Insulating window panels
are essentially pop-in shutters that clip into the interior of a window frame and have R-values ranging from 3.5 to 7. No hardware or latches are required and seals can be made with Velcro or magnetic tape.
Mesh window screens, mounted on the exterior of the window frame, can diffuse solar radiation. Awnings and roof overhangs/eaves
can shade windows and reduce solar heat gain. Awnings on west and south windows can reduce solar heat gain between 65 to 77 percent. Eaves are simply not part of the brownstone architectural ethos, and awnings may be an option on the rear of your brownstone if you are in a landmarked zone but they will change the character of the building because these appendages were not original to brownstones. Window Shutters
. If you are lucky enough to have the original shutters that many brownstones were built with, or the space to retrofit new ones, then take advantage of their energy saving properties. Solid wood shutters reduce heat loss and summer solar heat gain; louvered shutters do not insulate against heat loss but help prevent unwanted solar heat gain.