One traditional window operation type is double or single-hung windows that slide vertically in a track. Double-hung windows allow both of the two sashes to move, while single-hung windows incorporate one fixed and one moving sash. Air infiltration control needs to be addressed on any movable sashes particularly where two movable sashes meet along their stiles since a tight seal is needed to keep out drafts. The particular appearance of single- and double-hung windows can vary depending on the manufacturer’s offerings with options for traditional, craftsman, or more contemporary design languages incorporated.

For building designs that seek a more contemporary look using a single operable sash in each window, then awning and casement style windows are appropriate. Casement-style windows are usually intended for a vertical orientation with the hinge on one side and the operational hardware on the bottom. Awning windows use the same components, just in a horizontal orientation with the hinge at the top and the hardware on the side or the bottom. The quality and appearance of awning and casement windows can vary by manufacturer, particularly in regard to the hardware that makes them operate, so it is advisable to review specific product details. The two common types of operational hardware are “push-out” systems (allowing the sash to be literally pushed outward) and a rotating handle (cranking the sash outward). Regardless, all casement and awning-style windows close and lock tightly against a weather seal around the entire perimeter of the single sash. This means they can usually provide better air infiltration control when compared to double-hung windows. The locking hardware is usually concealed in the frame and closes against the sash at multiple points.

Photo: Steve Wisenbaker Architects | Kasten Builders | Paul Dyer Photography; courtesy of Loewen Windows and Doors

Fixed glass or picture windows can be designed into custom sizes and shapes to provide daylight and views in conjunction with separate operable windows for ventilation.

Fixed Windows

Some building designs seek to maximize views and daylight while minimizing air infiltration. As long as there is enough natural or mechanical ventilation, then the use of fixed, picture, or direct set windows is an appropriate solution. They are usually available with the same sash and frame appearances and details to match the operable windows for a consistent look across a building facade.

One benefit of fixed windows is that they have the potential to be sized larger than operable windows depending on the window frame and sash details. There are limits based on the maximum practical area or code requirements for the glass too, but generally, a wide range of sizes and shapes can be considered. The style may allow for a minimal frame to create a clean aesthetic or for stylized frames and trim to match the overall design intent of the building. They also have the potential for very good energy performance by selecting high-performance glass, triple glazing, or other treatments.

In terms of coordinating large or oversized fixed windows with the rest of the building construction, it is worth noting that exterior-glazed products provide an easier on-site installation into wood framed walls. The alternative would be to install fixed glass into a site-built frame, from the interior, which would typically involve more time and effort. For high-performance buildings, some fixed windows can also work with “rain screen” principles which allow for water deflection and drainage behind the cladding.

RESIDENTIAL GLAZED CURTAIN WALL

Residential curtain walls are a more complete approach to fixed glass across a large wall area. Such systems can be fabricated from a variety of materials, but one preferred residential approach is to use wood timbers as the supporting frame. This accomplishes several things. First, the wood provides a predictable material to base engineering and support calculations on. Second, it provides the visual appeal of natural wood which is commonly used on the interior side of residential fenestration. Third, the wood material has better thermal performance than the use of an aluminum frame system.

Timber curtain wall (TCW) systems for residential applications are tailored to the specific requirements of each project by a fabricator using parts from a manufacturer. As such, every TCW is treated as a custom design that will go through a detailed shop drawing process to ensure that all the architectural and engineering specifications are met. Residential TCW units can be factory assembled and hand-prepped for improved quality control. Timber connectors, gaskets, and glass carriers can be pre-applied. Completed units are commonly predrilled, marked, and labeled. Each entire timber curtain wall unit is shipped in a knocked-down condition to the site ensuring accurate, easy assembly and field glazing. By comparison, conventional, or stick-built curtain wall systems require each horizontal section to be placed one after the other with a high degree of quality checking and field precision necessary for the installation.

Photo: Steve Wisenbaker Architects | Kasten Builders | Paul Dyer Photography; courtesy of Loewen Windows and Doors

Timber curtain walls provide large-scale glazing for residential buildings with aesthetics, strength, and environmentally friendly aspects all a consideration.

To ensure strength and resistance to warping and twisting, horizontal and vertical timber components should be either glue-laminated solid lumber or engineered core lumber with finished facings. Transoms or horizontal rails are the horizontal members of the curtain wall system. The mullions or vertical members are anchored to wood framing or a concrete slab. These components support the dead weight and wind loads of the curtain wall and transfer those loads to the building structure. The thickness of the timbers is commonly 2" - 2-1/8" with a timber depth of 4" to 9“, although these dimensions will vary based on wind load and structural criteria.

In designing and specifying a TCW system for a residential project, several things need to be kept in mind. First, engineering considerations need to be investigated with careful integration with adjacent elements such as floors, wall claddings, roofs, beams, and other building envelope components. Second, the configuration of the TCW needs to be accounted for since it can be fabricated for vertical wall systems, sloped roof systems, and corner conditions. They can also incorporate any combination of fixed and operable window and door units. Third, heavy gauge extruded aluminum is the most common choice for an exterior cover to the TCW system since it is most likely to retain its shape, resist denting, last longer, and be the most economical. It can be finished in some commonly available techniques including Class I anodic coatings (AAMA 611) or high-performance factory-applied fluoropolymer thermoset coatings (AAMA 2605). These finishes are known for their excellent resistance to weather and environmental degradation.

Glazing options for TCWs include a full variety of glass and coating selections, suitable for different climate zones or environmental concerns. These include monolithic glass, dual and triple-glazed sealed insulating glass units (IGUs), impact-resistant laminated glass, sound-attenuated glass, annealed, and tempered glass. Most glazed units are limited by maximum practical sizes for typical sealed unit glazing, although that will vary based on the glass specification. Larger sizes may be available, but costs and time schedules can increase significantly, so consultation with a manufacturer is advised.

In some residential timber curtain walls, there are no weep holes in the horizontal clad members. Instead, water that strikes a TCW is conducted through the exterior seal and gaskets, to the base/sill where it can percolate and drain out. Water control is determined by the design of the connectors and the integrity of the gasket system. Two or three-level, continuous EPDM gaskets with integrated drainage has become the industry standard.