our drewexim windows and doors patiently await installation while sitting in a warehouse in bangor. we selected these windows primarily for their energy performance characteristics. in this house, these include heat loss (“R” value), solar heat gain coefficient (SHGC) and visible light transmittance (VLT). basically, our goals are to minimize heat loss (losing precious heat through the glass during the heating season), maximize heat gain during winter months (its that solar-thing, you know, capture the sun’s heat through the glass) and enjoy the benefits of natural daylight. fine-tuning the tri-pane glass to attain these goals is readily accomplished with this window.
so, here are the numbers….
R-value = 5. the triple pane glass is comprised of three layers of 4 mm glass separated by two, argon filled 10 mm air spaces. the glass has low emissivity (Low-E) coatings on the appropriate faces.
SHGC = 0.50. we could have upgraded to .62 (higher is better), but there were two factors working against us. one, it costs more – the minor increase in solar heat gain wasn’t sufficient to offset the added cost. second, the two large, primary solar-oriented window units had to be tempered glass (per code due to the adjacent stairway and proximity to floor level) and the SHGC upgrade is not available with tempered glass. we could have mixed the two types of glass in different units, but were concerned there might be a slight difference in appearance between the two glass types. again, the minor performance improvement did not warrant the the cost….cost as in the risk of an apparent visual difference (not aesthetically desirable).
VLT = 0.70. again, higher is better, and this is very good. we want abundant daylight because its good to have natural light and to minimize dependence upon artificial (electricity!) lighting.
another functional consideration is the construction of the window itself. a large, beefy wooden frame (about 3 1/2” square) encompasses the window unit. the exterior is painted aluminum applied to the wooden frame. this aluminum is a significant extrusion with an integral rainscreen that provides an airspace/drainage plane between the aluminum and the wood. so, any water (rain) that might penetrate behind the aluminum exterior will drain to the outside. thus, greatly decreasing the likelihood of wood deterioration/rot due to moisture infiltration. and, this aluminum exterior is attached in a manner that permits its removal and re-application should that be necessary for maintenance, repair, painting, etc. yeah, pretty cool!
this information summarizes the performance issues supporting our window choice. other deciding factors include aesthetics, operation and cost. these will be reviewed DREWEXIM DUO, a forthcoming post.
drewexim windows and doors are manufactured in poland (the country, not the town in maine!). all windows and doors are custom, as in made to order by size, configuration, finish, etc. nate campbell of fenestrations plus in bangor is the local distributor. you can reach nate at www.fenplus.com or call him at 207.631.5041.