A Visit to a LEED Platinum Office Building

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A Visit to a LEED Platinum Office Building

This high-rise building in Manitoba has high indoor air quality and low energy bills

Posted on Mar 10 2017 by Martin Holladay
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While I’ve designed a few single-family homes, I’m well aware that designing a high-rise office building is a whole ’nother kettle of fish. The challenge is far greater — at least an order-of-magnitude greater — requiring an experienced team that includes architects, structural engineers, mechanical engineers, and energy consultants.

I spent some time mulling the complexity of high-rise design during a recent tour of Manitoba Hydro Place, a 21-story office building in Winnipeg, Manitoba. I’m not in Winnipeg very often; I was in town because I’d been invited to give a presentation at a fenestrationTechnically, any transparent or translucent material plus any sash, frame, mullion, or divider attached to it, including windows, skylights, glass doors, and curtain walls. conference called FenCon 17. At the conference I met Harry Schroeder, a building systems engineer at Manitoba Hydro, and Schroeder offered to show me around his employer’s downtown headquarters.

A green showcase

What’s so interesting about this particular office building? Since it was completed in 2009 (and certified as LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. Platinum in 2012), Manitoba Hydro Place has received lots of international attention for its unusual green features and energy efficiency.

The high-rise office building is the headquarters of Manitoba Hydro, a utility that supplies the province with electricity and natural gas. The first floor of the building is mostly public space, including retail outlets. The lowest three floors, called the “podium,” have a bigger footprint than the tower above; the podium has a vegetated roof.

In hopes of encouraging employees to commute by bicycle and public transportation, the basement has only a limited number of parking spaces (see Image #2 at the bottom of the article). Some of the relevant specifications for the building are shown in the sidebar below.


ESSENTIAL INFO

Building name: Manitoba Hydro Place

Address: 360 Portage Avenue, Winnipeg, Manitoba

Winnipeg temperature range: -31°F in winter to 95°F in summer

Completion date: October 2008

Number of stories: 21

Capacity / number of employees: 2,000

Area: 695,000 square feet

Project cost: Cdn $ 278,000,000 ($400/s.f.)

Design Architect: Kuwabara Payne McKenna Blumberg Architects, Toronto

Architect of record: Smith Carter Architects, Winnipeg

Energy engineering: Transsolar Energietechnik GMBH, Stuttgart, Germany

Green certification: LEED Platinum (achieved May 2012)


Double envelope

Like many high-rise buildings, Manitoba Hydro Place has lots of glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill.. Three of its façades consist of all-glass curtain walls. The south façade is fairly conventional; it has double glazing. The only unusual features on the south side of the building: low-iron glass was specified (to maximize solar gain), and the windows were all fitted with computer-controlled motorized blinds.

The east and west façades are more unusual; they are “double-envelope” façades, with two layers of glazing separated by a 3-foot wide catwalk (see Image #3, below). The outer curtain wall consists of double glazing; the inner curtain wall consists of single glazing. As on the south side, the east and west sides of the building include computer-controlled motorized blinds that go up and down as needed to control glare and reduce overheating (see Images #4 and #5).

I asked Mark Pauls, a building energy management engineer for Manitoba Hydro, whether employees could push a manual override button to open the blinds when they are down, or close the blinds when they are open. “The blinds are on a sun-tracking system to adjust the extension and tilt of the louvers based on sun position, with a light level sensor retracting all blinds on an overcast day,” Pauls responded. “Individual employees can override blind position using a small computer application for three hours at a time.”

The exterior curtain wall includes operable windows with motorized actuators; like the blinds, these windows are opened and closed by a computer (see Image #6). The interior curtain wall includes manually-operated windows that can be opened and closed by the people who work in the building.

In the winter, the computer-controlled exterior windows on the east and west façades are mostly kept shut. During the summer, computer controls open these windows as needed to reduce the heat buildup between the two glass curtain walls.

Do these highly glazed façades make sense?

Since Winnipeg gets bitterly cold during the winter, many observers might wonder, “Why does this building have so much glazing?”

The building’s defenders claim that this highly glazed building uses less energy than a building with a more typical glazing ratio. In an article on Manitoba Hydro Place in Green Building & Design magazine, Benjamin Van Loon wrote, “Within the meteorological context of Winnipeg, a humid continental climate with hot summers and frigid winters, a glass office building is an unconventional choice in the extreme weather, but the design boasts revolutionary energy efficiency. It maximizes low-grade solar-thermal energy, natural wind, and year-round fresh-air exchange, and it has not only met but also exceeded energy-savings targets set by KPMB [the architectural team]. ‘The “submarine approach” will give you an average of 50 percent energy savings,’ [facilities manager Tom] Akerstream says. ‘Our original target for the Hydro Building was 60 percent better than the model national energy code for buildings, and we’re currently hitting 70 percent. When we get all of the bugs worked out, we expect to increase that.’”

For an opposing view, see the sidebar below (“Joe Lstiburek's Opinion”).


JOE LSTIBUREK’S OPINION

In an essay called “Prioritizing Green,” building scientist Joseph Lstiburek shared his opinion of double façade buildings. An excerpt follows.

“Many ‘green’ buildings ... have too much glass, they are over-ventilated, they are leaky to air, they are fraught with thermal bridges and they rely on gimmicks and fads rather than physics. …

“Here is the general premise behind the double façade. The outer façade creates a buffer space between it and the inner façade tempering the environment the inner façade sees. So we have to build two walls — not one — an outer wall and an inner wall with a bunch of space in between. Seems to me that if you built the inner wall correctly you don’t need the outer wall — and vice versa. We call that a ‘duh’ where I’m from. And then you get to use the space between them because there is no space between them — it is all inside — we call that rentable floor area where I’m from. Double façades are a low energy way to provide an all glass enclosure, but they always use more energy than a decent façade with less than 100 percent glass. Why ever go there?

“Oh, I forgot about all the passive ventilation ‘magic’ that happens between the two facades and the operable windows you can have between the inner façade and the ‘magic” space. ...

“I have got news for all you façadists — you can have operable windows in a single façade and you can get a lot more control and predictability with things called fans, ductwork and controls. Oh, by the way, you can get it at a lot less cost, using a lot less materials (i.e. ‘resource efficiency’) and using a lot less energy. But, but, fans use energy — it’s not natural to use fans. The other way, the ‘magic’ way uses ‘natural’ forces that are good because nature is good and man is inherently evil. Didn’t we have this argument over two hundred plus years ago with a dead French guy called Rousseau? If we taught architects more physics and less philosophy they wouldn’t fall for this garbage — and while I’m at it shame on you engineers for using bad physics to deceive gullible architects.”


A huge solar chimney

A dominant architectural feature of Manitoba Hydro Place is its towering 377-foot-tall solar chimney, glazed on the south side with single-pane low-iron glass (see Images #7 and #8). The “chimney” is significantly taller than the occupied floors of the building. The solar chimney has a post-and-beam frame made of concrete; between the concrete frame and the exterior claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. is a continuous layer of mineral wool insulation. (For more on solar chimneys, see Fans and Natural Cooling.)

The function of the solar chimney is to act as an exhaust fan for the building. Exhaust ventilation air from each floor is ducted to the solar chimney. The air in the solar chimney, heated by solar radiation, rises to the top of the chimney, driven by the stack effectAlso referred to as the chimney effect, this is one of three primary forces that drives air leakage in buildings. When warm air is in a column (such as a building), its buoyancy pulls colder air in low in buildings as the buoyant air exerts pressure to escape out the top. The pressure of stack effect is proportional to the height of the column of air and the temperature difference between the air in the column and ambient air. Stack effect is much stronger in cold climates during the heating season than in hot climates during the cooling season.. During the spring, summer, and fall, air is exhausted from open louvers at the top of the chimney. During the winter, fans pull air from the top of the solar chimney and deliver the warm air to the underground parking garage, warming the basement (see Image #9).

Installed near the top of the solar chimney are dozens of parallel lengths of 5-inch-diameter steel pipe filled with sand. The sand-filled pipes act as thermal massHeavy, high-heat-capacity material that can absorb and store a significant amount of heat; used in passive solar heating to keep the house warm at night. , ensuring that the stack effectAlso referred to as the chimney effect, this is one of three primary forces that drives air leakage in buildings. When warm air is in a column (such as a building), its buoyancy pulls colder air in low in buildings as the buoyant air exerts pressure to escape out the top. The pressure of stack effect is proportional to the height of the column of air and the temperature difference between the air in the column and ambient air. Stack effect is much stronger in cold climates during the heating season than in hot climates during the cooling season. continues encouraging air to rise up the chimney, even after the sun goes down.

Big buffer spaces to temper ventilation air

The upper 18 floors of the building are divided horizontally into three sections, each 6 stories high. Each of these sections has a 6-story glazed atrium.

These atria aren’t intended to be occupied; they are buffer spaces. The temperature in these atria ranges from a low of about 50°F to a high of about 86°F.

Fresh ventilation air passes through these atria before the air is delivered to the offices. In effect, the atria pre-condition outdoor air before the air is delivered. Each atrium has a “water feature”: a 6-story-high waterfall consisting of 280 mylar ribbons down which water is allowed to dribble (see Images #10 and #11).

During winter months, moisture from these waterfalls evaporates, humidifying the ventilation air.

During summer months, chilled water is delivered to the top of each waterfall. (The water is cooled by the building’s ground-source heat pumps.) As this chilled water dribbles down the mylar ribbon, humidity in the atrium air condenses on the cold water, increasing the volume of flowing water and dehumidifying the ventilation air.

That’s the idea, anyway. As it turns out, the design doesn't quite work. The current method of humidifying ventilation air during the winter is inadequate. On the day I visited, the indoor relative humidity in the offices was 22.7%; that’s relatively low. According to Mark Pauls, “My feeling is this [problem] is probably more to do with the temperature of the water than the surface area. Our system, as designed, can only get the water temperature up to 30°C [86°F], and we could probably use another 10 C° [18 F°] to get more humidification.”

Indoor air quality

At Green Building Advisor, we’ve recommended for years that residential ventilation systems be kept separate from heating systems. This idea — separating the “V” part of HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building., so that a ventilation system has dedicated ducts — is not yet common, however.

In a Globe and Mail article on Manitoba Hydro Place, reporter Vito Cupoli wrote, “Bruce Kuwabara, an architect whose Toronto-based firm KPMB led the project team, says the big idea was to separate ventilation from heating and cooling. As a result, air coming into an atrium is warmed or cooled, depending on the season. It is then drawn into workspaces, where it drifts up from floor vents. It leaves the building through an impressive solar chimney that soars above the structure.”

Rather than passing through ventilation ducts, the fresh ventilation air is distributed through a plenum area under each floor. (See Images #12 and #13.) This type of ventilation system is called a displacement ventilationVentilation that uses natural convection to move warm air up and out of a building; used in Scandinavia since the 1970s, it is being increasingly employed in the United States. system. In effect, this under-floor crawl space is one big ventilation duct (see Image #14).

A technical document prepared by Manitoba Hydro explains, “Air enters at floor level and moves slowly along the floor until rising in a plume generated by occupants or other heat sources. Fresh air is thus selectively delivered where needed, and stale air rises past the occupied level, where it moves along the ceiling to an outlet.”

By all reports, Manitoba Hydro Place has excellent indoor air quality. On the day of my visit, the indoor CO2 level was 502 ppm, which is quite low. Manitoba Hydro reports that the average employee at Manitoba Hydro place has 1.5 fewer sick days per year than employees working at other office buildings owned by the company.

Ground-source heat pumps

Space heating for Manitoba Hydro Place is provided by the largest closed-loop ground-source heat pump system ever installed in Manitoba. The system includes 280 drilled boreholes, each 6 inches in diameter and 380 feet deep. Inserted is each borehole is a U-shaped length of tubing running to the bottom of the borehole; the space between the tubing and the wall of each borehole is filled with grout. A glycol solution circulates through the tubing.

The heat distribution system is hydronic, via tubing embedded in concrete slabs that act as radiant ceilings. Water heated to 82°F circulates through the tubing during the winter. The radiant ceilings are also used for space cooling during the summer.

According to Schroeder, some employees in the building complain that desks near south-facing glazing are uncomfortable on sunny days due to overheating.

Lots of motorized components

The Globe and Mail article on Manitoba Hydro Place noted, “The building has 25,000 points of environmental control, including fans, sun blinds, lighting and operable windows.” It’s hard to tell whether this is an example of gee-whiz enthusiasm or foreboding.

According to Schroeder, he’s heard people say that the building has “too many moving parts,” and he’s also heard reports that there have been maintenance problems with some of the building’s hundreds of motorized blinds.

I asked Mark Pauls whether the motorized blinds and window operators have caused maintenance problems. “There are a few different systems of motorized blinds in the building,” Pauls answered. “The roller style have been trouble-free, and the louver-style in the double façade have been very reliable. We have had issues with the large louver blinds in the winter garden, where the shades are 7 meters in height (lots of weight on the motor) and are exposed to wide-ranging conditions and direct sunlight. In terms of the window operators, they’ve been fairly good. With almost 400 motorized windows in the building, we always have a few that require repair/replacement each spring. Overall, I think the key message is that our building has three building operators [maintenance employees] fully responsible for all 700,000 square feet, so the operations and maintenance costs are lower than what we’ve seen with our traditional office buildings.”

Energy performance

According to Wikipedia, “a typical office high-rise in the city [of Winnipeg] uses approximately 325 kWh/m² annually,” while Manitoba Hydro Place “targets electric usage [of] less than 100 kWh/m²/a.”

According to an article in High Performance Buildings magazine, the building’s site energy us is 29.3 kBTU1,000 Btus/ft². That’s equal to 92.3 kWh/m² — under the target mentioned in the article above. The High Performance Buildings article notes that the building uses 52% of the energy of a building complying with ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). International organization dedicated to the advancement of heating, ventilation, air conditioning, and refrigeration through research, standards writing, publishing, and continuing education. Membership is open to anyone in the HVAC&R field; the organization has about 50,000 members. Standard 90.1-2007.

According to the Globe and Mail article, “Hydro Place uses 60 per cent less energy than the model national energy code for buildings (MNECB), a government efficiency baseline for new buildings in Canada.”

Construction cost

Manitoba Hydro Place cost $400 per square foot to build in 2009. According to Wikipedia (citing Canadian Architect magazine), “This would place the cost of the building much higher than local building developers would typically target for a city that is not expanding rapidly.”

There are two reasons for the building’s high construction cost per square foot: the building includes features not usually found in ordinary office buildings (extra layers of glazing, for example, and motorized blinds); and the building includes substantial areas that aren’t usable as office space (the walkways between the inner and outer envelopes, for example, and the large atria) but which nevertheless increase the building's square footage.

What I noticed during my visit

Harry Schroeder and I drove to Manitoba Hydro Place in a Nissan Leaf. Pulling into the underground parking garage, Harry parked the car in one of the spots reserved for electric vehicles (see Image #15). As we walked to the stairwell, I noticed several bicycle racks. (Later, as we toured the upper floors, I noticed that the building provides shower facilities for its employees — a convenient feature for those who commute by bicycle.)

I'm under no illusions that my nose is a good judge of indoor air quality; like most people, I can't tell the difference between good and bad indoor air. But the indoor air was certainly unobjectionable.

Since it was a sunny day, the computer-controlled blinds were mostly down. This approach certainly addressed to problem of glare, but it also interrupted the view. I couldn't help wondering whether a more traditional, old-fashioned façade — mostly opaque, with a few (smaller) window offering a view of the city — might not be a better way to address glare.

Complexity vs. simplicity

The operation of Manitoba Hydro Place requires thousands of motorized blinds, motorized louvers, and motorized window operators, as well as sophisticated software and controls to ensure that everything is being opened and closed at the right time. This level of complexity increases the difficulty of building commissioning.

Installing these systems in a house would be an act of madness, but installing them in a high-rise office building isn’t necessarily insane. After all, a building this big already needs an on-site engineer and maintenance staff, whether or not there are as many motorized features as were included in Manitoba Hydro Place. The proof is in the pudding: operations and maintenance costs at Manitoba Hydro Place are relatively low, as are energy costs per square foot.

Designers of large office buildings, just like designers of single-family homes, have to decide what’s best: a rugged building with mostly passive features and simple HVAC systems, or a more finely tuned building with lots of active features and a complex HVAC system. If the more complex building uses less energy than the simpler building, designers have to weigh robustness against energy savings. Finding the perfect spot on this spectrum isn’t always easy.

The innovative features of this type of building could never have been evaluated unless a few brave pioneers had been willing to take chances and to see what happens. In my opinion, the designers of Manitoba Hydro Place are to be lauded for venturing into new territory as they pursued their goals of energy efficiency and high indoor air quality. For the most part, they succeeded.

Martin Holladay’s previous blog: “Three Superinsulated Houses in Vermont.”

Click here to follow Martin Holladay on Twitter.


Tags: , , , , , , , ,

Image Credits:

  1. Image #1: KrazyTea / Wikimedia Commons
  2. Images #2 through #6: Martin Holladay
  3. Image #7: Manitoba Hydro
  4. Image #8: Martin Holladay
  5. Image #9: KPMB Architects
  6. Images #10 and #11: Martin Holladay
  7. Images #12 and #13: Transsolar
  8. Images #14 through #17: Martin Holladay

1.
Mar 11, 2017 9:39 AM ET

Like fine wine...
by Armando Cobo

I'm worried that Joe is getting softer and subtle as he ages... decanter anyone? Love it!


2.
Mar 11, 2017 11:12 AM ET

Highly glazed facades
by Martin Holladay

Evaluating this building is tricky. While researching the article, I tried to contact John Straube, but he was busy and unreachable. Two days ago, I ran into John Straube at the NESEA conference in Boston, and as I guessed, he's very familiar with Manitoba Hydro Place.

I'm hoping he'll post a comment here. To summarize what he told me (and of course I don't want to put words in his mouth), Straube told me that the bulk of the energy savings that this building enjoys can be attributed to the massive ground-source heat pump system, and that these savings occur in spite of, not because of, the highly glazed envelope.

-- Martin Holladay


3.
Mar 12, 2017 2:55 PM ET

Aesthetics do matter too
by Robert Opaluch

Being less interested in large buildings, it took me a while before I bothered to read this article but found it very interesting.

Those of us who are engineers tend to design buildings that are conventional in appearance (at best) and sometimes just plain unattractive (to put it diplomatically). Architects can bring aesthetic sensibilities and beauty to buildings, as well as innovative design.

However I agree with Joe Lstiburek (and enjoy his jibes at this design). KISS, keep it simple, stupid! Maybe architects introduce some complexity and reduce some energy efficiency when making a building innovative and attractive. But at a cost. Maybe goes building goes too far, although I have to agree this is an interesting building from an energy management standpoint. I'd like to see an alternative building that is more energy efficient at half this cost, and see if an architect could make it at least as attractive as Manitoba Hydro Place.


4.
Mar 13, 2017 11:20 PM ET

Straube on Highly Glazed Enclosures
by Kohta Ueno

Martin--if Straube doesn't have time to comment, some of his key points can be found here:

BSD-006: Can Highly Glazed Building Façades Be Green?
https://buildingscience.com/documents/insights/bsi-006-can-fully-glazed-...


5.
Mar 14, 2017 6:04 AM ET

Response to Kohta Ueno
by Martin Holladay

Kohta,
Thanks for the link. My gut tells me that Straube and Lstiburek are correct: There is no advantage to designing a building with a façade that is 100% glazing.

-- Martin Holladay


6.
Mar 14, 2017 9:54 AM ET

Edited Mar 14, 2017 9:54 AM ET.

100% Glazed Facades
by Kohta Ueno

My gut tells me that Straube and Lstiburek are correct: There is no advantage to designing a building with a façade that is 100% glazing.

Yes--definitely agree with this. I know folks use the logic: "If you're designing a 100% glazed building, a double facade is a great solution." (actually, I believe that's wrong--if you crunch through the numbers and include the loss of floor space, something like a high performance triple glazed curtain wall makes more sense.)

But I'd push back on the basic premise--I consider their statement analogous to: "If you're going to smoke crack and rob liquor stores, perhaps you might consider enjoying the crack after your robberies, to be more alert during the action." True that it is *better*, but....


7.
Mar 14, 2017 10:17 AM ET

Liquor story robbery advice
by Martin Holladay

Love the analogy, Kohta.

-- Martin Holladay


8.
Mar 14, 2017 10:27 AM ET

One more point
by Martin Holladay

There's an irony in the design of Manitoba Hydro Place: The designers sought simplicity and passivity, and ended up with complexity and the need for lots of active features.

After all, why build an extremely expensive multi-story concrete solar chimney? Obviously, because it's "passive," and it saves the cost of operating a fan. (The solar chimney probably cost millions of dollars, enough to run fans for 2,000 years, but we'll leave that issue aside.) The designers ended up with a building that is anything but passive, however -- it's as twitchy as a harpsichord that needs to be tuned twice a day.

-- Martin Holladay


9.
Mar 14, 2017 10:41 AM ET

"twitchy as a harpsichord"
by Michael Maines

I'm going to have to try to find a way to work "twitchy as a harpsichord" into conversation.


10.
Mar 14, 2017 10:44 AM ET

Response to Michael Maines
by Martin Holladay

Michael,
My father was a piano tuner. For many years, he owned a harpsichord. No one should own a harpsichord unless they know how to tune it themselves.

-- Martin Holladay


11.
Mar 14, 2017 2:24 PM ET

Irony
by Charlie Sullivan

The glass in the solar chimney may be iron free but the irony is not only the overall complexity, but also that in the winter, they in fact run fans to bring the buoyant hot air down from the highest level to the garage. Right when the solar chimney's stack effect is most strongly driving the air upward, there is fan power being used to bring that same air downward.


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