Quoted from http://www.buildingscience.com/documents/insights/bsi-006-can-fully-glazed-curtainwalls-be-green/?topic=/doctypes/building-science-insights:

BSI-006: Can Highly Glazed Building Facades Be Green?

Insight By John Straube Building Science Insight 006: last updated 2009/05/22

When I see a fully glazed, floor-to-ceiling commercial or institutional building, I see an energy-consuming nightmare of a building that requires lots of heating and cooling at the perimeter just to maintain comfort. The result, on a cold winter day, is that offices exposed to the sun require cooling, while those in the shade need heat. Unless the control system is highly tuned, too many of the occupants will also be uncomfortable. Although it is well accepted that “green” buildings are above all low energy consumption buildings, there is a mistaken belief, almost a myth, that buildings with large expanses of glass are somehow green.

Glazing systems, including almost all modern high-performance ones, have very little ability to control heat flow and solar radiation.  Older windows also did little to control heat loss and solar gain.  Hence, most older buildings had restrained window-to-wall area ratios. Most of the tremendous performance gains in glazing technology over the past 25 years have been squandered on increased window area, not improved performance.

 

Photo 1: An all-glass “high-performance” thermally-broken curtainwall with low-e, argon-filled glazing units and R-12 spandrel insulation. Sleek appearance but dismal performance by any normal standard. The R-value of the combined spandrel and glazing is less than R-4, and the solar gain is high enough to require air-conditioning on cold sunny winter days.

 

Normal thermally-broken commercial aluminum windows and curtainwalls typically have U-values of about 0.5, corresponding to an R-value of two. By using the best available low-e coated, argon-filled double-glazed units (with a center-of-glass R-value of four) in thermally-broken aluminum frames, overall window R-values of three can be approached. If the goal is low-energy buildings, why cover large portions of any building with such a low R-value system, particularly in cold climates? Spandrel panels are not much better in this regard. Although often packed with three or more inches of insulation (providing a nominal R-12), the metal back pans and aluminum framing short-circuit the insulation so that their overall R-value is typically closer to only four or five. Most so-called “high-performance” curtainwalls with a mix of vision glass and spandrel panels have overall R-values of less than 4. It is difficult to understand how such a choice of exterior wall could be considered a “green” system, when a simple low-cost wall with only an inch of continuous rigid insulation will provide significantly better control of heat flow!

But the thermal qualities are only part of the story. Glazing lets light in. That, after all, is the primary reason we use glazing. The solar heat gain that results is the reason many buildings require air-conditioning. The size of a building’s air-conditioning plant is almost always defined by the glazed area: more glazing means more chillers, ducts, coils, and fans. In the past, thermally massive offices, schools and shops with limited glazing could tolerate little or no mechanical air-conditioning. It is a testament to the miracles of modern glazing (which uses low-e, low emissivity coatings to selectively allow more visible light than infrared heat radiation), that many buildings can have such large window areas and remain comfortable in the summer. Nevertheless, even very good commercial clear glazing still allows about one-third of the sun’s heat to enter.

It is true that daylight can offset the need for electric lighting and provide a psychologically healthy connection to the outdoors, but one doesn’t need floor-to-ceiling glass for that. In most occupancies and building types, there is no benefit to vision glass installed at floor levels (unless the occupants spend much of their time lying on the floor near the window), but there is a substantial energy penalty. Good daylighting design can reap all the benefits of glazing using vision glass covering less than half the enclosure. Numerous studies have shown there are no daylighting or energy benefits with window-to-wall ratios over 60 percent, and in most cases an area of between 25 and 40 percent is optimum (that is, lowest energy consumption). Even at these ratios, windows in a low-energy building should generally be high performance (triple-glazed in cold climates), with large thermal breaks (over 1/2″ thick) and some form of exterior shading (preferably operable).

 

Photo 2: Almost the entire façade of this condominium tower is covered with low R-value and high solar gain curtainwall. It is almost impossible to achieve a low energy, comfortable building with this approach.

 

How should one choose glazing for green, low energy commercial buildings? At the most basic level, there are three critical measures of performance that must be chosen in design, and specified in contract documents: The U-value (1/R-value), the Solar Heat Gain Coefficient (SHGC) and the Visible Transmittance (VT).

The U-value is the reciprocal of the R-value. A U-value of 0.33 is an R-value of 3 for example, (except that in the case of glazing systems the U-value includes the effect of surface films, unlike walls). As the climate becomes cold or very hot, a low U-value becomes important for energy savings and for comfort.  Buildings with low U-value windows and/or curtainwalls can dispense with special, and costly, perimeter heating even in very cold climates.

The Solar Heat Gain Coefficient (SHGC) is the fraction of solar radiation that hits the glazing that passes through the glazing and becomes heat inside the room. For example, if the SHGC of a glazing unit is 0.50, and the sun is shining on the window with an intensity of 250 Btu/hr/ft2, 125 Btu/hr/ft2 will enter the building as heat. The lower the SHGC the greater its shading ability. Although specially-designed houses in cold climates often can benefit from solar heat gain in cold weather (ie, passive solar heating), modern offices and assembly spaces should have sufficient insulation and airtightness that the interior heat generated by occupants and activities provide most of the heat, even in cold weather. Bright sunny days often cause overheating of over-glazed south-facing spaces during cold (e.g. -10 deg F) days, whereas during unoccupied nights, when heating is needed, the low R-values result in heating demand.  Operable exterior shading both obviates the need to choose a low SHGC window and provides much more control, but entails significant design effort, changes the appearance, and can be costly. Increasing opaque spandrel area, thereby reducing vision area, also reduces the total solar gain into the building of course.

 

Photo 3: Residential windows usually come with an affixed sticker providing verified and useful performance values: the U-value, Solar Heat Gain Coefficient and the Visible Transmittance. Commercial window specifiers need to define these performance metrics in their construction documents.

 

 

The third measure, visible transmittance (VT), reports the percentage of visible light transmitted through the glazing. A typical clear, double-glazed window will have a VT of 0.60, meaning it admits 60% of the visible light. When daylight in a space is desirable, as in showrooms, high VT glazing is a logical choice. In offices and classrooms, where glare is a real issue, mid-range VT may be specified for large glazing areas, or high VT for small glazing areas. Low VT glazings such as bronze, gray, or reflective-film windows were often used in office buildings of the past as they also reduced solar heat gain. Modern spectrally selective (SS) windows allow for both a high VT with a low SHGC (and always have a lower U-value than uncoated glass). These SS windows reduce allow for significant daylighting and psychological benefits while avoiding overheating during sunny days.

In the end, glazing is a classic design problem that requires one to balance the desire for thermal comfort, energy efficiency, and light quality (all of which require small window areas) with equally important desires for view, daylight, and connectivity with the outdoors (all of which benefit from large vision-glass areas). Less window / curtainwall area, and higher system performance is the low-cost, high performance prescription for buildings suffering from excessive glazing area. Carefully choosing, and then specifying, overall system U-value, SHGC, and VT is the best start to delivering high performance glazing on your next project.

Many designers have shown that beautiful and high-performance buildings can result from a proper balance of glazing quantity and quality. All too often, however, designers appear to choose all-glass curtain walls or floor-to-ceiling strip windows because they make it easy to create a sleek impression while leaving all the tricky details in the hands of the manufacturers. How much longer can we afford to pay the energy bills that result from that choice? It’s high time to revive the craft of designing beautiful facades that don’t cost the earth.

 

   
Photo 4: A modern office building with a near-optimal window-to-wall area for energy and daylight performance in Boston, MA

Post Script: The very best in commercial aluminum curtainwall and windows are capable of R6 to R9. There are super windows in research labs with R-values of 10, and even 12 with dynamically operable shading capable of reducing the solar gain to less than 0.10 during bright sun and opening up to 0.60 or more during dull days.  Other systems that incorporate light diffusing elements (such as Kalwall and Solera) and phase change materials (such as Glass-X) can reduce energy flows across daylight panels by a factor of ten!  Eventually such technology should become more affordable and available, opening up the possibility of high glazing area and high performance.

 

 

The impact of thermal bridging through commercial wall assemblies, and heat flow through window systems can be calculated with relatively good accuracy by calculating an area-weighted average of the R-values of the windows and opaque wall sections. The equation takes the form:   Uoverall= (WWR * Uwindow + (1 – WWR)* Uwall), where U = 1/R. The results of a number of scenarios are plotted in the chart below. Typical curtainwall systems have an R-value of only 2 or 3, with “high performance” systems (not shown) using highly insulated (say R12) spandrel panels and best-in-class double glazing (with low-e and Argon) may achieve R-4. Only a few systems, such as the Kawneer 7550 series or Visionwall, can achieve R-values of 6 or more.   Curve 1 above is for standard U=0.50 thermally-broken aluminum punched windows with air-filled double-glazed insulated glazing units in a R-12 batt-filled steel-stud brick veneer wall system (a true R-value of R-6 when thermal bridging is considered). The overall effective R-value of this wall is around 3 to 4 over the normal range of commercial window-to-wall (WWR) ratios of 25 to 50%. Curve 2 shows that Increasing the R-value of the opaque wall to R-11 by adding an inch of foam on the exterior results in an increase of only R-0.5 to R-1.5 for the overall R-value for the same range of WWR. Curve 3 shows how significant an impact window performance can make even if a good wall is provided. An externally-insulated R-16 wall, when mated with poor windows produces a vertical enclosure with an R-value of only R-3 to R-6 for the normal range of window areas. Curve 4 assumes a good-quality window frame with top quality glazing (low-e, argon-filled): the result for the overall vertical enclosure is still only R-4 to R-7. These first four curves cover the performance of a wide range of commercial enclosures with a wide range of cladding types. Despite what most designers and owners think, the simple conclusion is that modern commercial vertical enclosures actually have an R-value that is rarely over 7, and more likely in the range of 3 to 5! Curves 5 and 6 provide an idea of the significant improvements that are possible. Using best-in-class thermally broken aluminum frames and high-performance glazing (U=0.30), Curve 5 shows that even with an R-40 wall, the overall R-value will be in the 7 to 12 range for WWRs of less than 40% (the highest ratio recommended for high-performance buildings). Even though this is a low-level, it is still about significantly more than the alternatives. The grey curve below Curve 5 shows that decreasing the opaque wall R-value from 40 to 20 has little negative impact particularly at high glazing ratios. Curve 6 employs commercially-available low-e, argon-filled triple-glazed units in an insulated fiberglass frame, to deliver a U-value of only 0.14. Even with a wall insulated to “just” R-20, such a combination can deliver an overall R-value of 12-14, two to three times more than typical commercial vertical enclosures. In all cases, it can be seen that high glazing ratios generate enclosure walls that are expensive to purchase with very high heat loss and heat gain. This high ratio should be avoided in both individual spaces, such as meeting rooms, as for the whole building on average.

Building Envelope,Flood restoration,Renovations

Quoted from http://www.buildingscience.com/documents/insights/bsi-027-material-view-of-mold:

Insight Material View of Mold By Joseph Lstiburek Building Science Insight 027: last updated 2009/11/10

Mold is pretty easy to understand.  No water no mold.  Any questions?  Well, there are a few.  For one we have more mold today, but we don’t have more water.  What’s with that?  We’ve always built outside out of wet stuff.  Concrete comes in a big truck and we “pour it.”  We put “mud” in the joints of gypsum board.  That hasn’t changed.  The problem is that the same amount of water we’ve always had to deal with is hanging around longer and longer in building materials that can’t take it.  We have more insulation today and that reduces drying potentials because it reduces energy exchange.  That is one reason we have more problems with mold today.  The “more insulation” is responsible for the water “hanging around longer” part.  But there is another reason—the building materials “that can’t take it” part.  We used to build out of rocks and 1,000 year-old trees.  Not any more and that is a big deal, as we will see.

From an engineering perspective all that mold needs is carbon—to boldly go where no mold has gone before and seek out and find carbon.  But it wants the carbon in a very special form—it wants it in the form of sugar.  So, all the mold wants is the carbon in sugar.  Now, we don’t talk that way because we don’t want civilians to catch on.  We say that mold wants the carbon in a glucose polymer called cellulose—it makes us sound smarter.  So where is all the cellulose?  It’s in the plant kingdom.  So, all the mold wants is the carbon in the cellulose in the plant kingdom.  Pretty easy so far.  But there are certain rules that the mold has to follow—one of which is that the plant has to be dead first.  So what do we build out of?  Naturally, dead plants.1

We go out and kill the tree, butcher the tree – commit tree genocide.2 We used to cut the tree into timbers and large boards.  With timbers and board lumber we had few mold problems because mold could not burrow into the timbers and board lumber and access the carbon in the wood fiber.  Young, violent, vicious, aggressive mold could not break the board lumber down.  Mold was principally a surface phenomenon with these materials—you could wash the mold off the surface of the timbers and wood boards with soap and water and elbow grease and be done.  All those folks running around with HEPA vacuums, sanders, dry ice pressure blasting and negative pressure containment were just a “tax” on stupid people.3 What did P.T. Barnum say about never underestimating the stupidity of the average American consumer?

But we don’t build much out of timbers and board lumber anymore.  Instead of cutting the tree, we peel the tree and smush the layers together under heat and pressure.  We cook the raw wood meat to tenderize it and make plywood. The plywood goes out to the job site slightly brownish in color because we’ve caramelized the wood sugars—we’re making mold candy. If you’re mold and you have a choice between timbers, board lumber and plywood what are you going to choose?  Plywood.

But we don’t build much out of plywood anymore either.  Instead of peeling the tree, we flake the tree, add glues and waxes and the Colonels’ “eleven secret herbs and spices” and we smush all of that together and make Oriented Strand Board—OSB.  I call it “was-wood”—it was wood once, but it ain’t wood no more.  I call OSB the Spam of wood, actually I call Spam the OSB of luncheon meats.  If you are mold and you have a choice between OSB and plywood what are you going to choose?  OSB (see Photograph 1).

Photograph 1: OSB versus Plywood—At the University of Waterloo “skunkworks” an OSB panel and plywood panel are exposed to identical temperature and humidity conditions over the same time period—the panels were side by side in a climate chamber.  The OSB is covered with mold—the plywood is pristine.  Now don’t everyone run out and stop using OSB—we have to use OSB—get with the program—just learn to protect the OSB better.

 

Remember the old days—crawlspaces constructed with dimensional board lumber—2 x 10’s sheathed with plywood.  Now we have I-joists and OSB sheathing.  We almost never had mold in these assemblies in the old days—now when you mention crawlspaces mold is in the very next sentence.4

Are we done yet?  Not by a long shot.  When we flake the tree we now put the flakes in a giant pressure cooker, pressurize to a couple of atmospheres at a couple of hundred degrees, pop the lid and the flakes explosively decompress to create fibers in a process developed by William Mason early in the last century.  We then put the fibers in a vat, get a bunch of Witches that chant—“double, double, toil and trouble, fire burn and cauldron bubble”—and presto we get hardboard.  If you are mold and you have a choice between hardboard and OSB what are you going to choose?  Hardboard.

Now we can take the fibers and grind them up into sawdust and then compress them all together with glues and nitrogen.  And we get particleboard.  Where do we get the nitrogen?  From the back end of a cow—urea from cow urine. What do you think the particleboard smells like when it gets wet?  What do we make out of the particleboard?  Floor underlayment, cabinets, furniture, tables.  The nitrogen is like Cajun seasoning to the mold.  If you are mold and you have a choice between hardboard and particleboard what are you going to choose?  Particleboard (see Photograph 2).

 

Photograph 2: Grass Cabinetry—Greenie weenie compressed grass laminate used in kitchen cabinets didn’t fare very well in this “award winning” sustainable community.  Solution?  Get rid of the grass stuff?  Nope.  Back vent the cabinets.

 

What next?  We dissolve the fibers and reconstitute them and get paper.  Old mold with no teeth can eat paper.  What do we do with this paper?  We laminate it to both side of gypsum board.  We make paper-faced gypsum board.  And what do we do with this gypsum board?  We line the inside of our buildings with it.  If we build commercial non-combustible assemblies we line the outside of our buildings with it.  We build our demising walls, our shaft walls, our service walls, and our party-walls with it.  We are in essence building paper buildings.  Even the dumbest of the three little pigs didn’t build his house out of paper.

And then what do we do?  We color the paper green like we are going to fool the mold.  And then where do we put the greenboard?  In a shower.  Let’s put green paper in a shower and cover it with “lick and stick” tiles—there’s a good idea.  Coloring the paper green to protect it from mold is like putting lipstick on a pig—at the end of the day you still have a pig (Photograph 3).

 

Photograph 3:  Greenboard—It’s not a good sign when the mold is already on the greenboard before the tiles are installed.  What gives?  The waxes added to protect the paper from liquid phase water—to meet a ridiculous ASTM spec—are “mold food.”  When products are optimized to meet arbitrary ASTM specifications rather than optimized to meet the “real world” problems result.  Of course paper in a shower regardless of color is pretty dumb.

 

So what do we do?  Not use paper-faced gypsum?  No, paper-faced gypsum is one of the miracle products of the last century.  It made housing affordable and is the mainstay of commercial construction—it replaced wet applied interior finishes such as plaster and lath.  “Drywall” replaced “wet walls.”  What we have to do is not use it in wet areas.  Don’t put paper-faced gypsum in a shower or the outside of your building or in a party-wall that is constructed before the roof is on and the building is “dried in.”  We have other products such as glass-faced gypsum and cement boards for these applications.  Paper-faced gypsum is a fantastic material that we are going to use well into this century—but we are going to have to pick our spots where we use it better.

Let us now think about the big picture.  What has been going on over the last half century in the construction industry?  As we have moved down the process stream from timber, board lumber, plywood, OSB, hardboard, particleboard, to paper laminates – each step of the processing has made the products more water and mold sensitive.  Are we going to stop this trend?  What are the odds of going back and building out of thousand-year-old trees and rocks?  Not going to happen.  We have to come to terms with the fact that the building materials we use today are far more mold and water sensitive and are likely to remain so for the foreseeable future. 

Engineered wood products such as OSB and I-joists and other composites are here to stay—in fact they are more desirable as I believe they are significantly more environmentally responsible.  I believe that we are going to see a transition from a hydrocarbon-based economy to a carbohydrate-based economy.  We are seeing this in the energy sector and I think we will see this in the materials sector.

Getting our cellulose fibers in Iowa, Mississippi and Georgia on plantations makes a lot more sense than getting them in the Old Growth Forests in the mountains of Oregon and Washington State.  Managed forests and plantations are the way to go.  But there are problems with these cellulose based engineered materials as the preceding discussion shows.

We are going to have to be more careful in how we use them.  They have to be protected more during the construction process and the building assemblies these products are used in will have to be designed differently.  The micro-climates these materials are exposed to are going to have to be different from the micro-climates traditional building materials were exposed to if they are expected to last the service life of the building.  And if they get wet and damaged and become moldy—soap and water or painting them over is not going to do the trick.  They probably are going to have to be removed (and removed carefully) and discarded.  The old days of soap and water are probably gone where the new stuff is concerned. 

Photograph 4: Window Openings 1—Leaking windows and OSB are a match made in consultant heaven.  Notice the smile on the famous unidentified consultant.  Of course the EIFS cladding had a little to do with this as well.

 

Photograph 5: Window Openings 2—Notice the pan flashed opening.  The products are discretely left unidentified.

 

The trends are already obvious.  Every window and door opening will have a pan flashing because incidental water is no longer tolerable with engineered materials (Photograph 4 and Photograph 5).  We have committees and manufacturers going crazy figuring out installation practices for windows and doors.  No double vapor barriers allowed.5 Crawlspaces are going to have to be constructed “conditioned” or will have to have use rigid insulation to protect OSB based I-joists and OSB based sub-floor sheathing from exterior moisture (Photograph 6 and Figure 1).  Greenboard in wet areas has just been banned in the Model Codes6 (Photograph 7).  We are going to have to back vent our cabinetry.  And this is just the beginning.

 

Photograph 6: Conditioned Crawlspace—Constructing crawlspaces like mini basements locates the engineered products within the interior environment.

 

Figure 1: Protected Vented Crawlspace—Rigid, non water sensitive, vapor impermeable insulation is installed on the underside of the floor framing and floor sheathing creating a micro-climate suitable for engineered wood structural framing and sheathing.

 

 

Peak Ventures would like to thank the  Owners of Le Chamois Hotel and the following Consultants, Trade Contractors and Suppliers for the opportunity to deliver phase 1 On Time and On Budget.  Your commitment to quality and professionalism greatly enhanced the project.  We look forward to working together in 2010.

Alpine Lock & Safe Ltd.
Apex Building Sciences
BCT Fencing
Black Tusk Cranes Ltd.
Bull, Housser & Tupper LLP
Carney’s Waste Systems
Charles Plastering
Corona Excavations
Fastenal Canada
Fox Strata Management
Garibaldi Graphics
Greer Insulation
Griff Building Supplies Ltd.
Haakon Industries
Home Depot (Squamish)
JJ Mak Window Installation
Mountain Paint Whistler
Naicom Computer Services
Pacific West Systems Supply Ltd.
Platinum Property Management
Pocklington Building Systems
Postman Enterprises
Preswitt Manufacturing Ltd
Red Mechanical
Rocky Mountain
Rona Revy Inc. (Whistler)
Sabre Rentals Ltd.
Sea to Sky Courier & Freight
Sherwin-Williams Whistler
Steels Industrial Products Ltd
Viking Fire Protection Inc.
Western Safety Products Ltd.
Westland
Whistler Glass Ltd.
Whistler Welding Services Ltd.
Whistler’s Personnel Solution
Wildfire Fire-Equipment
Wildflower Lodge
Willpower Systems Inc.
Windsor Plywood