Pro-Seal Aluminum Glazing System In the News
From an article appearing in The Journal of Light Construction
There's nothing quite like a room with a full glass roof to capture the warmth of the sun. But all that overhead glazing can also collect a lot of condensed moisture when it's cold outside and warm within. On sloped glazing, the water drips and stains the woodwork; in extreme cases, the sunroom environment also supports mold growth and wood rot. A glazing system that allows condensation to weep to the outside is critical to the long-term success of a custom sunroom.
On a recent job, we built a custom, freestanding sunroom using Summit Geld-Wen, vinyl custom picture, awning, and trapezoidal units for the vertical glass, and three motorized Velux venting roof windows on the north-facing roof slope. Automatically controlled by thermostat and rain sensors, the roof windows allow cooler, fresh air to convect up from the low-mounted awning window vents. We also installed a separate, thermostatically activated power vent to further control indoor temperatures. For the array of 3x9-foot fixed glass panels on the south-facing side, we used Pro-Seal glazing bars (Abundant Energy, 800/426-4859,
www.abundantenergyinc.com,) a versatile glazing system for sloped and vertical applications. Pro-Seal's glazing bars are made of extruded aluminum in a white or bronze finish and fit various glass thicknesses from 1/4-inch single-pane to I-inch insulating glass. The bars come in 20-foot lengths, shipped by common carrier, or they can be factory-cut to lengths under 8 feet and shipped by overnight carrier. Since the components systems are field cut and installed, the shape of extn the glazing panels can be customized to sides suit eccentric or irregular openings. Panel size is limited only by the size of bevel glass that can be manufactured. The glazing bars come in various component profiles to make a complete system. On this job, we used perimeter extrusions on the top, bottom, and sides, and mullion profiles for the vertical divisions between glass panels. A bevel-topped purlin made for intermediate horizontal divisions is also available.
Each component of the assembly consists of four parts: a gasketed base, or bottom bar that rests against the framing and receives the glazing panel; a gasketed glazing cap that clamps over the glass; continuous EPDM (ethylene propylene diene monomer) rubber gasketing; and a trim cover to conceal and protect the clamping screws (see Figure 1). The perimeter glazing bar is available with or without a thermal break strip separating the inner and outer surfaces.
Pro-Seal is strictly a nonstructural, or "skin," system and must be fastened to a wood or metal supporting frame. On this frame, we used 4x8 Parallam rafters, lag-bolted over an 8x16 structural Parallam ridge beam. While certain solid lumber species, such as Douglas fir or cedar, may be acceptable, stability is crucial. A wood frame that shrinks, twists, or allows excessive movement will spell big trouble for any glazing system. For this reason, pressure-treated lumber and green lumber are especially poor choices.
On the south-facing side of the building, which is fully glazed, we joined the wall corners and mullion posts to the roof framing with customwelded 1/2-inch-thick steel moment connectors to resist wind racking. The north-facing walls and roof had conventional framing with enough sheathing to provide sufficient stiffrless.
There are no rough openings in a custom sunroom; it's finish work from the beginning. The upper edge of the sloped framing supports the glazing system and must therefore be as true and square as possible. Headers must be flush at the top with the rafters, and any bumps or crowns must be planed flat. Everything lays out on centerlines; the extruded aluminum bars are a consistent 21/2 inches wide and have full-length centerlines inscribed on them to help with alignment.
When we had completed the framing, we covered the rafter tops with a peel-and-stick membrane underlayment to prevent any possible condensation from contacting the wood (Figure 2). At the eaves, we installed custom-bent aluminum apron flashing that runs from the bottom edge of the roof opening over the edge of the roof.
Assembling the Parts
Before installing any of the extrusions, we pressed the EPDM gasket material into its intended raceways (Figure 3, previous page). Each gasket should seal tightly against intersecting and adjacent pieces. Therefore, it's a good idea to allow the gasket material several hours' rest before final trimming to recover from possible stretching. The first extrusion installed is the head member, which runs across the top of the openings, the full length of the glazing area. We predrilled the base of the perimeter bar with a series of holes, starting 2 inches in from each end and spaced 15 inches apart, for fastening the bar to the framing with the #lOx2-inch stainless-steel screws provided. The prescriptive spacing ensures that there'll be no conflict with the cap-bar screws that are installed later, on 12-inch centers. The inscribed centerline in the underside of the bar helped prevent the 7/32-inch drill bit from wandering off center. Each end of the head piece gets mitered to the perimeter sides.
The perimeter sides are square-cut at the bottom ends, while the intermediate vertical members are square-cut at both top and bottom.
Bottom perimeter members are cut to fit between the mullions. It's important to drill the required 3/16-inch weep holes, one at either end of each bottom bar, before installation. Drilling later risks punching through the extrusion and chipping the glass edge. Nicking the edge of tempered glass courts disaster, as the sheet may spontaneously shatter into thousands of glittering "dice." The weep holes drain the interior gutter system and prevent condensation from overflowing onto and staining the supporting wood frame. Because of the importance of positive gutter drainage, the Pro-Seal system should not be installed on roof pitches less than 3 in 12.
With the complete base-bar layout screwed to the frame and the gaskets set, we're ready for glazing. We use I-inch insulating glass, with a laminated interior panel and a tempered exterior panel. If, by chance, the glass is hit and breaks, the exterior panel will break into small, harmless pieces; a bonded plastic sheet prevents the interior panel from shattering and catches the fragmented outer panel, preventing harm to anyone below. We ordered the interior panel with a low-e coating on the side facing the insulating void, as much to help reduce interior condensation as to control heat loss.
Pro-Seal uses a pair of 4-inch-long rubber setting blocks, screwed to the bottom perimeter bar of each panel section, to fully support the double edge of the glass panels. Neglecting to support the entire edge of an insulating glass panel - both the inner and outer panes - is a major cause of seal failure in sloped glazing. If only the bottom (inner) pane is stopped at the base of the panel, the upper panel may "creep" downward and rupture the seal. Generally speaking, thermal glass fabricators Will not guarantee against seal failure in sloped glazing applications, especially when they're not in control of the installation. The glazing panels are heavy as well as fragile; four of us working together boosted them onto the staging and lowered them into place. We used glazier's vacuum cup grips to handle the panels (Figure 4). A pair costs around $150, well worth it if you frequently install glass panels or mirrors.
Because of the custom nature of each installation, flashing isn't included with the glazing bars. Pro-Seal recommends using minimum .032-gauge aluminum flashing to prevent rippling. We bent the profiles on a lO-foot brake, using bronze coil stock to match the system components. The manufacturer provides good detail drawings in its design manual.
The eaves flashing goes on first, before the extrusions are installed (Figure 5). After the glazing panels were in place~ we installed side flashings, which overlap the apron flashing with a 45-degree end cut, giving the appearance of a mitered joint. The overlap is set in silicone caulk and secured with a few stainless-steel screws. The design manual offers two methods for sealing the side flashing to the glazing system: by running it flat beneath the side perimeter bar, or by making up-andover right-angle bends and clamping it under the glazing cap and gasket. We decided to go with the second, more surefire method.
The head flashing breaks up and over the top perimeter bar to fully cover the glazing cap. A strip of foambacked tape between the flashing and cap bar closes any gaps and serves as a backer rod behind a final bead of silicone caulk.
The gasketed glazing cap serves as the primary barrier to water intrusion around the glass. Because you can expect aluminum to expand in hot weather, the design manual requires butt joints in the cap to have a mini- I mum lis-inch expansion gap, to be filled with silicone caulk. However, the EPDM gasket must be cut long to bridge the gap and butt snugly against adjacent gasketing. The glazing cap gets drilled every 12 inches for the l/4-inch gasketed stainless-steel machine screws that connect it to the base extrusion (Figure 6). A running depression in the cap creates a recess for the fastener heads. The heads are finally concealed by a snap-in trim cover strip that must be gently tapped into place with either a wood block and hammer or a rubber mallet. A good grade of silicone caulkon all the joints and intersections tops I up the glazing system.
The Pro-Seal design manual is detailed and clear. When properly installed, the system will remain leak free for a long time. We've been using this system for 15 years and have many satisfied clients.
John DeCiantis owns DeCiantis Construction in Stonington, Conn