Green Means

Selecting Quality Windows

By Shannon Scott

            Selecting windows for a home involves a whole lot more than just deciding upon price, brand, and color.  With glass a major expense for any home, time and care must be taken to find two things: manufacturers that produce quality, environmentally responsible, and energy wise products; and distributors that offer competitive prices and good customer service.

            Since we’ve begun our small straw bale cottage project I phoned several window distributors in and around our area asking for Sierra Pacific brand windows, though I was open to learning about other green savvy products as well.  While many manufacturers offer claims of environmentalism, Sierra Pacific was one of the first to show genuine concern for sustainable production, from responsible timber growth to using zero VOC (volatile organic chemical) paint finishes. 

            Nu Vu Glass in Twin Falls phoned  back the same day and within two days e-mailed preliminary prices.  Mark, their chief sales rep for our area, suggested that I look into Anderson Eagle series and Weather Shield.  Nu Vu carries Marvin and several other major window brands.  Delivery to our area is included in their bids.

            After some back and forth with Mark and internet research on window configuration and brands, I narrowed it down to Marvin, Andersen, and Sierra Pacific.  Marvin definitely had nicer finish details than the other brands, but with the corresponding higher cost.  Anderson offers many options and boasts some green qualities, but ultimately I stuck with the Sierra Pacific.  The convincing feature, besides sustainably harvested wood was the no VOC exterior finish.  Now it’s up to me to find zero VOC interior wood finish products, as it doesn’t appear that Sierra Pacific offers prefinished models.

            With brand selection out of the way I had to compare glass features.  Passive solar design necessitates south window glazing that allows sun’s warmth to penetrate during winter months, while maintaining a fair level of insulation to keep out summer’s heat.  No direct sun enters south windows during summer, but the ambient outdoor temperature can still migrate inside.

            All window manufacturers post technical specifications on their websites so customers can compare glazing data.  I compared various combinations of U-values - lower numbers mean greater insular quality; SHGC or Solar Heat Gain Coefficient which indicates the allowance or disallowance of solar heat to penetrate (for south windows I want penetration, for all other sides minimal penetration); a high VT or visible transmittance for a nice clear view; and low CR, the Condensation Rating that tells how well glass resists condensation build up. 

            Deciding upon the best combination of features involves compromise.  Ideally, I could run a northern Nevada construction laboratory, build three to four identical buildings side-by-side each with slightly different glazing option combinations to see which combination of U-factor, SHGC, and VT prove optimal.  Since I don’t have the luxury of a local construction physics laboratory, I’ve got to go with available data and my best guess for optimal interior year round comfort levels and energy efficiency. 

             Higher SHGC (solar heat gain) means reduced U-value (insulation).  The slightly reduced U-value should prove negligible.  I’m weighting warmth in winter as more critical for human comfort and energy efficiency than cooling in summer.  We have relatively fewer super hot days as opposed to colder winter and spring time temperatures.  Plus, during summer months windows can be opened at night to allow in cooling high desert temperatures then closed in early morning to block out the day’s heat.  This type of physical adjustment to the building envelop is not available during winter.

            After reading charts and graphs to near delirium, I decided upon Low E² 180 Cardinal double glazed for south side windows.  These offer decent, but not great, insulation value while allowing in solar radiant heat.  For the north, east, and west faces the two better, and budget minded glazing options are either Low E²  366 i89 or Low E² 272 i89.  The final decision here will depend on price difference.  There are more heat deflecting and insulating options, like triple glazing, but they cost more.  The difference in glass quality must be measured against heating and cooling energy costs.

            Mark Birrer from Nu Vu Glass had my back on most the tech stuff.  He had quoted prices on pretty much what I had selected before I provided technical specifics.  So much of the time, unless we customers do our homework, sales forces do not ensure that we get the exact right product for our needs.  Even if you like and trust a supplier, double check technical data and specifics on everything you order.

            Frankly, I’m happy if a supplier just returns phone calls, but actually figuring tech data and then, get this, driving out to the boonies where I live to show Rob and me samples was pretty nice especially considering that our project is so small.  Mark still championed for Andersen Eagle series, which are a nice window, but ultimately we settled on Sierra Pacific.  They seem to be the underdog of window manufacturers, smaller but more humble, sort of like our project. 

            Window selection is critical for energy efficiency, comfort, aesthetics, and home quality.  Shop widely and wisely.  If you need assistance make some calls.  Nu Vu has been good to work with.  They get back to customers right away and are thinking green.  Mark showed up in Elko driving a Nu Vu Glass company Prius.  You can reach them at 208-734-9877. 

              Shannon Scott is a LEED Green Associate and green home owner, designer, builder.  You can reach her with questions or for green building help at greenmeansnv@gmail.com

             

            

Green Means

Why I Love Cement

By Shannon Scott

            Environmentally concerned construction researchers put hard effort into finding energy saving, strong, and human safe alternatives to Portland cement.  Portland cement takes a lot of energy to produce, referred to as high embodied energy. 

            Fly ash and silica fume have been widely promoted amongst green building professionals as better alternatives to Portland cement.  Several months back I mentioned fly ash as a viable alternative.  I’m retracting that position.  Fly ash is dangerous.

            Fly ash, the bottom ash from coal fired power plants, contains mineral and chemical elements specific to the original coal bed.  Fly ash’s toxic make up depends on coal origin, but generally contains one or more of the following: arsenic, lead, mercury, thallium, dioxins and PAH compounds that have proven carcinogenic and mutagenic, and several other minerals. 

            Portland cement may take a lot of energy to produce, but at least risk of heavy metal exposure is nil. 

            Portland cement is simply lime, clay or shale, and gypsum in varying proportions.  Dust masks or respirators must be worn if mixing Portland cement, lime plasters, or any other powdered materials containing silica dust.  Of course there are minor risks associated with any cement mixing, but not heavy metal poisoning as with fly ash. 

            Silica fume, another alternative to Portland cement, proves extremely strong and has been used in many high rise construction projects.  Silica fume is a byproduct of producing silicon metals and ferrosilicon alloys (iron and silicon).  Since it’s essentially a leftover product, putting it to good use in construction eliminates the energy demanded to produce a new product like Portland cement.  Yet it is silica particulate so wear good quality dust masks. 

            Many green buildings, straw bale, cob, and other natural construction methods recommend lime plasters for exterior applications.  I’m not convinced that lime plasters have comparable durability and flexibility as compared to old fashioned cement-lime stuccos.  Yes, I’m aware they’ve been used for thousands of years all over the world, but to what level of maintenance and care?  I’m not interested in lime washing or recoating every so many years to ensure durability, cover small cracks, or to refresh the look. 

            Certainly lime stucco breathes allowing moisture to transpire in and out which makes for a healthier and more durable wall, and with a tablespoon of linseed oil added to each mix lime plasters can be less pervious to water, but not as minimally pervious as sand-cement-lime mixtures. 

            Dryvit, a commonly used synthetic stucco, has latex in it which helps resist cracks as opposed to sand-cement-lime stuccos, but this inhibits breathability.  Moisture cannot transpire out and often causes rot around windows, fireplaces, doors and elsewhere if not sealed or caulked extremely well.

            For now, I’m going with old fashioned Portland cement-lime-sand mixes for exteriors.  They take time to mix and apply, but can be colored to suit any taste and last decades.  Any cracks are easy to repair with another swipe or two of the mix or with clear caulk.  I can spot repair and not have to resurface an entire building.  I’ll continue to use nice breathable lime plasters for interior applications over straw and other substrate, but for now I love working with cement. 

            Finding green alternatives to long used industry standards is challenging, but with homework, time, and effort we can find structurally sound, attractive, and human safe products.  We’ll just keep looking and experimenting.

            Shannon Scott is a LEED Green Associate and green home owner, designer, builder.  You can reach her with questions or for green building help at greenmeansnv@gmail.com