Canadian Consulting Engineer
One of the most beautiful buildings in the nation's capital has had its HVAC and other systems completely changed and upgraded. The challenge was to do the transformation without affecting the buildin...
One of the most beautiful buildings in the nation’s capital has had its HVAC and other systems completely changed and upgraded. The challenge was to do the transformation without affecting the building’s appearance.
When the Library of Parliament was opened in Ottawa in 1876, it was acclaimed both in Canada and abroad for its beauty and grandeur. Designed in the form of a Gothic chapter house and decorated with Victorian exuberance, the library sits on a promontory high over the Ottawa River, just a few metres away from the Centre Block of Canada’s Parliament Buildings.
The Library’s Reading Room has been called “the most beautiful room in Canada.” Yet by the late 1990s, virtually everything from the plastered dome above, to the intricate parquet floor and basements below, required conservation or upgrading. Also the storage space was inadequate — barely 60% of the books could be kept on site — and operational needs had changed, due to the increasing use of computers and other electronic devices.
The building has a total area of 3,000 square metres. At the centre of the symmetrical plan is the Reading Room, a large open space with a domed roof. Ornate wooden book stacks with two gallery levels surround the circular room. Around the building’s perimeter is a set of service spaces and offices.
The Library escaped a fire that destroyed the nearby Centre Block in 1916, but in 1952 a fire started in the dome and caused damage to the roof and the collections. Shortly after, the first major renovation was carried out.
Then, in 1998, Public Works and Government Services Canada contracted a team to undertake the second major overhaul. The design team had to make the building last 50 years and make it conform to current building codes. All these changes had to be done while preserving the architectural features of the historic building.
The project team decided the only way to accommodate the new systems and other needs was to expand the interior by digging deeper into the rock below by 9 metres. There
are now two spacious basements for the collections and support areas. An additional third basement was dug out for the new mechanical and electrical systems. (Golder Associates won a Canadian Consulting Engineering Award for their role in the geotechnical excavation — see October- November 2004.)
The Library building was entirely vacated in 2002 for the rehabilitation and officially reopened again in the summer of 2006. The total project cost was $136 million. The architects were a joint venture of Ogilvie & Hogg, Desnoyers Mercure et Associes, Spencer R. Higgins and Lundholm Associates.
MECHANICAL AND ELECTRICAL ENGINEERING , Pageau Morel & Associates
The challenge in upgrading the building’s services was having to do it while maintaining the integrity of the historic building’s architecture.
The new heating, ventilation and air conditioning (HVAC) systems required much more space than the old ones. Installing these larger systems was impossible to accomplish without extending the building, which was why the team proposed excavating underground to create a new mechanical-electrical room.
Using chilled water and steam from Ottawa’s centralized plant, Pageau Morel designed a system for the building with seven separated HVAC systems serving specific zones. From the principal air handling unit delivering 12,500 L/s of ventilation and providing cooling, dehumidification, a high filtration level, and heating to the Reading Room, through to the generation and storage of very low temperature glycol for dehumidification, all the equipment has been fitted under the existing building.
Since the new underground mechanical room is only 20 metres in diameter, whereas the existing building above is 30 metres in diameter, finding a way to supply the services to the spaces on the building’s perimeter without affecting the building aesthetics called for innovative approaches. The addition of visible ducts, for example, would not be allowed.
Pageau Morel proposed that the mechanical and electrical services should be installed on an angular perimetric distribution plan from the centre of the new basement up and to the outer spaces. To do this, the engineers proposed that a network of angled bore holes be drilled through the rock below the building to serve as electromechanical channels. The dimensions had to be large enough to house the HVAC equipment and silencers as well as plumbing, fire protection pipes, electrical, communication and security conduits. Then, to bring the HVAC services up into the offices on the perimeter, Pageau Morel proposed inserting a vertical distribution duct into the stone buttresses in each of the building’s 16 bays. To accommodate the ducts, a vertical channel was removed inside the buttresses.
The conservation rooms and Reading Room are supplied with air at the periphery, and the return air unit is in the centre of the Reading Room. This arrangement delivers optimal air diffusion and sweeping in the different sectors.
In the Reading Room, electro-mechanical components such as ventilation ducts, sprinkler piping and electrical services are installed behind the priceless 100-year old wood shelving. The 144 bookshelves have also been modified in their upper parts to integrate a ventilation plenum for air diffusion into the space.
Since durability is such an important issue, all the equipment is designed to last 50 years, compared to the standard 25-30 years. The ventilation ducts located under the concrete slabs are double-walled, and a chloride polyvinyl film covers the outside wall to ensure the longevity of the ducts and the thermal insulation between the walls.
Preserving the collections
The three worst enemies of the paper documents housed in the library are (a) exposure to ultraviolet (UV) rays, (b) an unstable ambient environment, and (c) exposure to fire and water.
In the Reading Room, all the existing light fixtures considered as “heritage” were retrofitted and the new fixtures have been strategically located where they are not visible. Each fixture that has a direct light diffusion towards the collections has been designed with a UV filter.
In the basement collections there needed to be a high number of lighting fixtures due to the variable position of the mobile shelving. The rooms were divided into several zones that are independently controlled by a sophisticated lighting management system. The system helps to ensure zones are only lit when necessary, thus reducing the documents’ exposure to UV rays.
Throughout the building light fixtures are interconnected through an automated control system. The system manages each individual fixture and lighting intensity, as well as lighting “scenarios” of specific area, such as the Reading Room, conference room, offices, etc.
Temperature and humidity
The temperature and humidity conditions in the conservation rooms and Reading Room where the collections are exposed had to be carefully stabilized. For example, the environment to be maintained for the “Security Collection” containing 100-year old documents must not exceed 20% to +/-2C, and 40% relative humidity to +/-3%. This percentage of variation is much smaller than for a standard traditional building.
Each of these spaces has been linked to an independent system to ensure that their particular environmental parameters are met and to allow for a diversity of environments within the building. As a back-up, the systems are interconnected.
Fire protection and alarms
Since fire and water are the worst enemies of documents, Pageau Morel put considerable energy into designing a system to minimize damage in a fire.
They designed a double interlock fire protection system that enables the entire network of sprinkler pipes to be filled with air, not water, until the system is triggered. As well, there is a two-stage alarm system that requires human action
before the sprinklers are activated, thus minimizing the risk of a needless and unwarranted sprinklering.
To protect the precious wood shelving in the Reading Room, a special 45-point air-sampler monitoring system provides early detection of traces of smoke in the air.
STRUCTURAL DESIGN , Adjeleian Allen Rubeli
The main vertical structural elements of the Library of Parliament are two concentric masonry walls: an outer ring wall of 45 metres diameter, and an inner ring wall of 26.5 metres diameter. Sixteen buttresses stiffen the outer ring wall, with flying buttresses arching above.
The structural engineers’ tasks were myriad, including restoring the masonry walls, which showed minor evidence of localized cracking, and a major water infiltration problem within the rubble core.
The construction of the underground mechanical room was the most challenging task. The mechanical room required excavating a large volume of rock 21.5 metres across and 8.9 metres deep, directly below the Library. Besides excavating for the new mechanical room as a third basement, the height of the two existing basement level slabs had to be reconstructed at new elevations.
The team decided that the floor slab of the Reading Room should remain in place during the basement construction. This was to avoid removbuildings ing the fragile book stacks and to allow work to proceed simultaneously in the upper space.
The column grid was increased from 2.7 m to 8.2 m, which reduced the number of columns from 76 to 12. The four central columns extend through the new mechanical room with an approximate height of 14 metres, plus a 2 metre socket.
The central columns have a central structural steel section, which provided the support during the excavation and construction. During a subsequent phase, the Reading Room slab support grid spanning between the 12 new columns was installed.
Once the new columns were in place, the next phase was the excavation of the new mechanical room. The excavation also involved creating an underground link to the House of Commons loading dock, and providing for a new emergency stair and lower elevator shaft.
Sloped holes in the rock were drilled to bring the mechanical-electrical ducts from the mechanical room up into the building’s perimeter. The inclined shafts were drilled by a raise bore technique.
The excavation and rock stabilization was by geotechnical consultant, Golder Associates. To avoid damaging nearby historical buildings, the excavation was done mechanically and carefully monitored. The mechanical room was excavated in 2-m deep concentric lifts, coordinated with local underpinning of the building’s inner ring wall.
Finally, the reinforced concrete walls of the mechanical room were poured, a reinforced concrete jacket was placed around the temporary steel columns, and reinforced concrete slabs were built at Level 0 and Level 1.
The seismic evaluation concluded that the overall building structure was adequate, provided that the stone mason- ry walls were sound and well bonded. However, the pinnacles and chimney had to be strengthened. The fragile upper sections of each pinnacle for example, were given a 12- metre long post-tensioned anchor in the centre.
Last year, Adjeleian Allen Rubeli received the Heritage Award for Buildings from IStructE, the Institution of Structural Engineers in London, U. K., for the project.
Owner: Public Works & Government Services Canada
Architects: Ogilvie & Hogg, Desnoyers Mercure et Associes, Spencer R. Higgins, Lundholm Associates, joint venture
Structural engineers: Adjeleian Allen Rubeli, Ottawa (Michael Petrescu-Comnene, P. Eng., V. Charles Fenton, P. Eng.)
Mechanical & electrical engineers: Pageau Morel and Associates, Gatineau, Que. (Sylvain Lavoie, P. Eng., Franois Laframboise, P. Eng.)
Geotechnical engineers: Golder Associates
General contractor: Thomas Fuller Construction