Frequently Asked Questions
Why is it normal for water to be present in the window/door sill?
What causes frost or condensation on aluminum frames?
Why is it normal for water to be present in the window/door sill?
Windows and doors are designed to be a see-through section of the structure's envelope. Therefore, elements such as rain can enter this part of the wall and not harm the dwelling. Harm only occurs when water passes behind the inside leg of the window/door. As an illustration, stucco is designed to take water into the wall 1" deep. Then a protective membrane redirects the water down to weep away from the dwelling. Additionally, operable windows and doors are designed to manage the differential in air pressure during a storm because the negative pressure in a house is essentially "pulling" water inside and therefore restricting its drainage from the window. This is why water must be present in the window/door sill.
What causes frost or condensation on aluminum frames?
Frost is the transfer of ice from the exterior to the interior side of a metal frame during sustained times of severely cold temperatures. With insulated aluminum framing (thermal break) this only happens when a "bridge" exists that negates the insulation of the extrusions. E.g. metal stud straps, metal panning, etc...
Frost varies from condensation in a few ways but in practical terms the biggest difference is that condensation can occur regardless of whether the window frame is insulated or not. If properly installed, a truly insulated aluminum frame cannot transfer frost. Another widely unknown fact is that condensation can occur in frame materials that are naturally insulated, such as wood and vinyl. How?
Condensation is most commonly caused by excess moisture in the dwelling. In new construction it is common for building materials to have a one to two year “drying out” period. During this time the humidity levels are high because the building materials are out gassing water vapor. What exacerbates the condensation is that areas nearest the windows are typically the coldest places in the room and do not have good air circulation. These sections are therefore susceptible to humidity condensing on the frames and/or glass.
Fleetwood provides aluminum sill pans for all of its insulated frame products (Aspen, Westwood, Glacier, Kona, Atlantic and Norwood 3070-CR). If concerns exist for either frost transfer or condensation then we recommend taking steps to "de-bridge" the insulated framing of the door or window. One method is to place 3/16" thick plastic shims between the pan and product. This will remove the bridge. Another method is to wrap the aluminum pan with a rubberized asphalt material such as Bituthene. If neither of these methods are desired the builder may elect to install a custom panning system that will not bridge exterior cold to the interior.
Added measures to reduce condensation include:
*Modern HVAC systems which feature aspects that address the levels of humidity.
*Creating systems that circulate the air around the window or door (especially at the bottom where cold air collects).