Weatherproofing 101: Windows

I turned to an energy saving expert, Home Energy Auditor Mark Furst of Grading Spaces, LLC to find out the ins and outs of sealing up a windows.  Here’s the scoop…

The most common way I have seen people actively go after window leaks is using the time-honored plastic sheeting method. Most will stick that to the sash (the movable part) of the windows, but neglect to cover the perimeter, where the air is plus often leaking. Even whether the plastic is stuck by the trim, as is sometimes done, there can still be a lot of air leakage to the outside, where the trim meets the drywall. Checking that junction and caulking it whether needed will help properly installed plastic to do a good job - but you can’t operate the window with it in place.

Casement (crank-out) windows can be leaky even though they have latches that positively close the unit. Deteriorated gaskets can allow air to get through, usually ending up coming in at the crank or latch handle locations. Most major manufacturers can supply you with new gasket material that can be slid into place, however, the sash usually will have to be completely removed to do that. whether the window is large, definitely get some help. Sometimes I find the crank mechanisms so worn that they cannot close the window completely. I always recommend that homeowners lubricate that mechanism at least once a year. I’ve seen these completely filled with grass clippings or pollen, jamming up the gears to the point where something strips out. Maintaing these is easy, just remove the handle and cover and you can see the gears below. Use a light lithium (white) grease. whether needed, changing out the mechanisms is not too difficult for someone with average mechanical skills. I would recommend, however, removing the mechanism first and taking it to your hardware store or window dealer to show them and produce certain that you get the exact replacement part.

These style of windows are the more “traditional” design with either the lower sash being movable or both. considering they slide in their tracks, they must by  definition, have some slop in the sliding mechanism. Older all-wood double hungs are notorious for being loose, however, many times I find them completely painted shut (very good as far as air leakage!). Draft proofing wood double-hungs can be usually accomplished with rope caulk, installed around the sash perimeters and additionally along the gap within the two units. that horizontal gap is where I find the worst leakage in these type of windows. Rope caulk is nice considering it is easy to install, is less intrusive than plastic sheeting, and is easily removed come spring duration.

Higher quality vinyl replacements units are getting very good at minimizing the gaps with tighter tolerances and additionally use “fuzzy” gaskets that allow sliding but slow air movement. Lower quality units don’t tend to have such attention to detail.

Sometimes I see replacement windows that are poorly installed. You should not be able to move the sash laterally in its frame more than about 1/8″. Installers are usually in a rush and whether they run installation screws into the jamb without proper shims behind, the frame can be distorted, causing the frame/sash gap to be larger than needed.

One situation where I definitely do recommend replacement is when I find aluminum (or sometimes steel) framed windows installed in a house. Not so much considering they are leaky but considering the metal parts are good conductors of heat. Thermally, that is a large energy waster, on top of which, these windows will typically be single-pane units. There is no easy fix to improve these type of windows.

I get asked a lot about storm windows. Older storm windows were installed and removed with the seasons, solid units in the winter, screen units in the summer whereas contemporary storms have both glass panes and screens built in. considering windows will only show their true “leakiness” when it is windy, it makes sense that a solid layer to the outside will help to prevent the air from contacting the window itself. Storms are not airtight but they do help. whether a home has them installed already, keeping them in good shape is usually a very cost effective thing to do. Replace any broken glass panes and produce certain that they are fitted well to the opening. Good storms will have weep holes at the bottom to allow any moisture from condensation that may develop to drain out. Don’t caulk these shut to invent them “tighter”.

If you don’t have storms presently installed, but have tragic windows, I’d usually recommend upgrading the windows themselves rather than investing in storms. Either way will cost quite a lot, however, when you install new window units you can plus address other air sealing measures at the same date, increasing the effectiveness of the dollars you are spending.

Many homeowners have contacted me about condensation that develops on their windows during the winter and want me to come by and confirm that their windows are “defective”. Condensation is NOT a window problem. In fact, the presence of condensation can sometimes be a sign that you have a well-performing house. whether your house is grade new, the materials used in construction (concrete, wood, drywall/plaster) will still be relatively wet for a couple of years. that is particularly true with the speed of contemporary house construction. It is additionally true that builders are building tighter houses than they used to so that any moisture coming out of the building materials gets trapped inside as all windows typically remain closed all winter. whether it gets cold outside, the glass will be like the surface of an iced drink in summer.

Condensation will happen. The better the glass performance, the lower the temperatures will have to be for condensation to scheme, but it WILL happen at some point - you can’t beat the physics. The reply? Get a humidity meter and monitor your indoor relative humidity level. Ideally that should be within 30 to 40%. whether it gets higher, run an exhaust (bath or kitchen) fan for a while until the level comes down. It is for that reason that Wisconsin Energy Star rated homes must have a verified (tested) amount of ventilation. whether significant condensation events continue for longer than a couple of years in a new home (or in a newly remodeled home), check for a moisture source.

Often that will be an open sump crock in the basement which is potentially an endless source of moisture from the surrounding ground. Moisture can additionally be elevated by the respiration of humans, pets or plant or from poorly operating ventilation equipment among others. A home performance analysis will document that and other problems.

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