The Environmentally Responsible Construction and Renovation Handbook
Chapter 5 - Implementing Energy Efficiency Measures
The energy-related goals of the Green Office Building Plan are intended to support the overall goal of minimizing the impact of federal buildings on the environment. The Federal government is committed to reducing greenhouse gas emissions, and energy efficiency contributes to this goal. The four principles behind the activities described in this section are therefore:
- Create healthy environments for office workers: air, light, noise, temperature, humidity.
- Reduce energy waste.
- Reduce energy consumption.
- Increase equipment and system efficiency.
The focus is on measures that are practical and cost-effective for major retrofits of existing buildings. There is even more scope for improvement in new construction.
The base level of energy performance is the Model National Energy Code for Buildings (MNECB). A Green Office Building should incorporate, as a minimum, where viable the mandatory and prescriptive requirements of the MNECB. In addition, certain requirements of the Commercial Buildings Incentive Program (CBIP) Prescriptive Path for Offices have also been incorporated, such as high efficiency lighting design.
Projects intended to achieve higher levels of energy efficiency are encouraged to comply with the full requirements of the CBIP and establish an energy use target that is 25% lower than a building designed to the NECB requirements. The Natural Resources Canada C2000 program sets an even more stringent target of 50% below ASHRAE 90.1 requirements and is recommended for new construction projects with aggressive energy reduction targets.
The Model National Energy Code for Buildings is available from the Institute for Research in Construction at the National Research Council Canada. Tel 1-800-672-7990 or (613) 993-2462, fax (613) 952-7673.
Most of the publications on the NECB (other than the codes themselves) are online at Canada's Energy Efficiency Homepage.
5.1 Building Envelope Insulation
The insulation of the building envelope is the key method of limiting the greatest energy use in office buildings in Canada - space heating. The intent of this section is to bring renovated buildings up to the modest insulation levels required in the NECB, and not to impose criteria that would be difficult to justify in a renovation project. Should the opportunities arise, however, higher insulation levels should be considered, for example, when new exterior walls or new roofing are installed. In the renovation, attention must be focused on insulating the thermal bridges which degrade the overall insulation value below the nominal rating of the assembly.
- Insulation: Overall thermal transmittance (U-value) of walls, roofs and floors-on-ground must not exceed the values in Appendix A of the MNECB. Solid masonry exterior walls are not exempt and must also be insulated to this level.
- Thermal bridging: Determination of an assembly's U-value must account for thermal bridging due to framing members and other conduction paths.
- Concrete roof and floor penetrations of envelope: The U-value of a wall at a concrete floor or roof intersection shall not be more than twice that of the associated wall.
- Partial penetration of envelope by services: Recessed heaters, pipes and ducts that partly penetrate the building envelope, must be located on the conditioned side of the insulation and must not increase the overall U-value of the building envelope assembly at the partial penetration to more than the U-value of the overall wall.
- Radiant heating: If radiant heating sources are embedded in floors-on-ground or in walls, the assembly must be insulated to a level 20% better than the maximum overall U-value allowed by the MNECB tables.
- Attic/ exterior wall joint: Attic insulation must be continuous over the top plate of the wall bearing the roof, and must have a U-value not more than that of the associated wall.
- Insulation overlap: At envelope locations where two planes of insulation do not physically join, the two continuous insulations shall overlap for a length of at least 4 times the distance separating the two insulations.
- Full envelope penetration by walls: Where a concrete or masonry foundation wall, firewall or party wall penetrates an exterior wall or roof, it shall be insulated on both sides to a distance at least 4 times the wall thickness and to the same U-value as the exterior envelope assembly.
- Below-grade walls requiring insulation shall be insulated over their full height to the U-value in the NECB tables.
5.2 Fenestration and Doors
Windows are the weak link in the insulation and airtightness of most office buildings. Windows have also experienced the greatest technical advance of any building components in Canada in the last decade. In small office buildings, the thermal performance of windows to reduce heat loss will be most important. In large office buildings, concerns about solar heat gain, glare and condensation will dominate. High performance windows offer solutions for both sizes of building, compared to conventional, double-glazed, aluminum-frame windows, and must be evaluated in any project where existing windows are being replaced. Otherwise, in a renovation where the intent is to keep the existing windows, the minimum requirement for a Green Office is that windows at least meet the NECB requirements.
- Overall thermal transmittance (U-value) of windows shall not exceed the U-value in the NECB Appendix A. Airtightness rating shall be A2 or better.
- The space between the window frame and the rough wall opening shall be insulated and air-sealed for continuity of the air barrier.
- Skylights: The U-value of skylights shall not exceed the U-value for fenestration in the NECB Appendix A.
- Doors: Overall U-value of swinging doors shall not exceed the values in NECB Table 3.3.1.3. Airtightness must comply with NECB article 3.2.4.3.
- Vestibules: Vestibules are required for all doors that separate conditioned space from the outdoors, except where exempted in NECB article 3.2.2.3.
5.3 Envelope Airtightness
Improving the airtightness of office building envelopes has several benefits:
- Reduced outside air infiltration and resulting heating and cooling loads
- Reduced structural deterioration resulting from pressure-driven moisture movement through the walls and roof assemblies
- Fewer drafts and improved worker comfort
- Reduced stack effect and better control of building pressurization
Building air-tightness is an area of active development in Canadian building science, and objective, measurable targets for the airtightness are still evolving. However, the indications are that there are multiple benefits to improved airtightness and all efforts should be made to achieve the tightest envelope possible. However, it should also be noted that the tighter the envelope the greater care must be taken to provide sufficient air exchange for worker comfort and health.
- Air barrier systems shall be designed and installed in accordance with Part 5 of the National Building Code of Canada (NBC). Sheet and panel type materials intended to act as an air barrier shall have an air leakage rate of no more than 0.02 L/s-m² at 75 Pa.
5.4 Lighting
Lighting can be the single greatest load for electricity in many offices, and cost as much as space heating over the year. With the recent advances in lighting technology, lighting energy can be reduced significantly, even below NECB levels, and still provide required levels of illumination. In this area, the Green Office Building Plan exceeds the NECB. The CBIP Prescriptive Path for Offices has shown that lower Lighting Power Densities are cost-effective and are the single most important way to reduce electrical use in offices.
- Exterior lighting efficacy: All exterior lamps must provide at least 60 lm/W.
- Exterior lighting controls: Exterior lighting shall be controlled by schedule controllers and/or photocells.
- Façade lighting: Façade lighting must be less than 1.2 W/m² of face.
- Interior lighting: Overall building Lighting Power Density (LPD) shall not exceed 11.5 W/m².
- Controls: There must be one control per circuit, next to an entrance, in clear line of site, readily accessible and identified, unless centralized and identified in accordance with MNECB 4.2.4.3 (2). There shall be one control for each office.
- Occupancy controls: Lighting in spaces which are not continuously occupied, eg. washrooms, utility rooms, shall be controlled by occupancy sensors.
- Daylighting: Photoelectric and/or dimming controls shall be provided for lighting of common use areas greater than 40m² and within 6 m of the building perimeter. Apply recognized daylighting design techniques to improve daylight levels, increase daylight penetration while minimizing adverse effects such as glare. (see Annotated Bibliography for references)
- Task lighting: Task lighting (not in the ceiling) shall have a switch near the workstation.
- Exit signs: Exit fixtures shall be rated less than 12 W each.
- Ballasts: Fluorescent lamp ballasts shall comply with MECB 4.2.5.
- Documentation: A statement of design intent and operational recommendations must be provided for lighting systems and shall include
- A single-line diagram of the lighting control systems showing the location of each zone and associated switches
- A luminaire schedule indicating lamp ballast replacement specification
- Manufacturers' operation and maintenance instructions for installed automatic lighting controls.
5.5 Electrical Power
Electricity is the largest energy cost in most offices. Electric utility bills include both energy charges in kilowatt-hours and power demand charges in kilowatts. In addition, utilities penalize large facilities with low power factors that require the utility to provide power factor compensation. Opportunities exist in major renovations for improving efficiencies of electrical power systems. As a minimum, renovation projects should add the capability to install meters to measure the performance of the electrical system and to enable users to be aware and responsible for the electricity they consume. The system design should also include adequate controls to discourage waste of electricity. The best way to save electricity is to turn equipment off.
The efficiency of office equipment is also a key element in reducing electrical use.
- Meters: In new construction and additions, suites having all electrical loads supplied by a feeder to only that suite shall be individually metered.
- Energy Monitoring: Systems with capacity greater than 250 kVA shall be designed to facilitate the future installation of a system to monitor current and voltage of certain spaces and loads as per NECB 7.2.1.2.
- Power receptacles: Where exterior power receptacles are provided, all intended for intermitant use shall be controlled by a switch or timer from within the building and labelled accordingly.
- Where exterior power receptacles are provided for indoor/outdoor parking and are supplied through a panel board serving a suite, they shall be controlled by switches or timers accessible only to the tenants of that suite.
- Transformers: Transformers and their power loss characteristics shall comply with NECB 7.2.3.1.
- Motors: Three-phase motors and their efficiency must comply with NECB 7.2.4.
- Power quality: Evaluate and correct voltage imbalances, voltage deviations, poor connections, undersized conductors, poor power factors, insulation leakage, and harmonics.
- Documentation: Documentation of the electrical power system shall be provided and shall include:
- A single-line diagram of the building electrical distribution systems showing the location and means to monitor energy consumption
- Schematic diagrams of electrical control systems controlling systems other than HVAC
- Manufacturers' operation and maintenance instructions for electrical equipment.
5.6 Heating Ventilating and Air Conditioning (HVAC) Systems
HVAC systems improvements offer the greatest potential for energy savings in most buildings. The first step for reducing HVAC operating costs in large buildings is to reduce HVAC loads, through such measures as described above. "Greening" an existing building may also include replacing equipment with more efficient models, improving controls and operating procedures, and retrofitting existing equipment to operate more efficiently. It must be realized, however, that central plants contain many interrelated components, and upgrading them takes careful planning, professional engineering design, and careful implementation. Properly designed, installed and maintained HVAC systems are efficient, provide comfort to the occupants, and inhibit the growth of moulds and fungi.
Energy efficiency measures for HVAC systems required of a green office building are listed below.
5.6.1 Equipment
Buildings usually operate under less than full-load heating and cooling conditions. Therefore, the greatest overall annual efficiency improvements will result from giving special consideration to part-load conditions and selecting equipment accordingly. Chiller manufacturers now provide a standard ratings for part-load efficiency, reflecting the fact that chillers operate at less than full load 99% of the time. Staging multiple chillers or boilers to meet varying demand also greatly improves efficiencies at low and moderate building loads. Pairing different-sized chillers or boilers in parallel offers greater flexibility to central plant equipment. Units should be staged with microprocessor controls to optimize system performance.
Equipment Efficiency
- HVAC equipment must comply with efficiency requirements in NECB 5.2.13.
- Field-assembled equipment must meet overall efficiency requirements in NECB 5.2.13.
- Service water equipment used for space heating must comply with the efficiency requirements of NECB 6.2.2.1.
HVAC Design
- HVAC systems must be sized to meet the needs of conditioned spaces and designed in accordance with good engineering practice as described in ASHRAE 90.1.
- Equipment installed outdoors or in an unconditioned space must be designated by the manufacturer for such installation.
Ice and Snow Melting
Sidewalks and driveways should be designed so they can be manually cleared of ice and snow and should not rely on ice- and snow-melting heaters. Where ice- and snow-melting heaters are required, they must have automatic or accessible manual on/off controls. The controls are to be clearly labelled and provided with an indicator light.
Cooling with Outdoor Air (Air Economizer)
- "Air economizer" systems that reduce mechanical cooling energy by direct use of outdoor air must be able to provide outdoor air volumes from 100% of design supply air (S/A) down to the minimum outdoor air flow required for acceptable indoor air quality. These systems must mix outdoor air and return air to a temperature as near as possible to the S/A temperature required to condition the space, except when on-coil temperatures for D/X systems must be higher to prevent coil freeze-up.
- Air economizer systems are required on systems of more than 1500 L/s supply air or 20 kW cooling capacity.
Water Economizer (Alternate to Air Economizer)
"Water economizer" systems that reduce mechanical cooling energy use by using outdoor air to chill cooling distribution fluid must be capable of cooling supply air to provide 100% of the cooling load when:
- outdoor air wet bulb temperature is 7° C or below, if distribution fluid is cooled by direct or indirect evaporation, or both;
- outdoor air dry bulb temperature is 10° C or below, if distribution fluid is cooled by sensible heat transfer only.
Fan Power of Constant Volume Systems
Constant-volume fan systems with 10kW or more of combined nameplate supply return and relief fan power must not exceed 1.6 W per L/s of supply air delivered to the conditioned spaces (as calculated according to NECB Sentence 5.3.12[2]).
This requirement does not apply to fans that are included in the performance ratings cited in NECB Subsection 5.2.13.
Control of HVAC Systems
A supply air handler shall be able to achieve supply air temperature without:
- heating previously cooled air (unless for process humidity control for areas such as computer rooms, or when the reheat energy is not from electricity or fossil fuels)
- cooling previously heated air
- heating outdoor air, alone or in mixed air, which is in excess of the minimum required for ventilation
Except for systems with a minimum S/A of 2 L/s per m² of floor area, systems that control temperature of a space by heating or cooling previously cooled or heated air, respectively, must be equipped with S/A reset controls that will automatically adjust the temperature of:
- the cool air supply to the highest temperature that will satisfy the temperature control zone requiring the coolest air, and/or
- the warm air supply to the lowest temperature that will satisfy the temperature control zone requiring the warmest air.
| Design Cooling Capacity | Max. First Stage Cooling Capacity |
|---|---|
| 25 to 70 kW | 50% |
| >70 kW | 25% |
Multiple Boilers and Chillers
Multiple boiler systems must prevent heat loss through boilers when they are not in operation through the use of such items as vent dampers or water shut-off valves interlocked with the burners. In parallel systems, off-line equipment should be isolated from cooling towers and distribution loops. With reduced pumping needs, circulation pumps can be shut off or modulated with variable speed drives.
5.6.2 Air Distribution
Dampers
Every duct or opening intended to discharge air from a conditioned space to the outdoors or to an unconditioned space and every outdoor air intake duct or opening must be equipped with a motorized damper. Exceptions include: combustion air intakes, kitchen exhausts, continuously operated systems, and very small ducts (see NECB 5.2.3.1 [2] to [4]). The dampers described above are to have these characteristics:
- located as closely as possible to the plane of the building envelope;
- designed to close automatically when the system is not in operation;
- air leakage through closed dampers to be less than 15 L/s per m² of cross-sectional area at a pressure difference of 250 Pa;
- may be located inside the building envelope if the duct between the damper and building is insulated to the level prescribed for the walls;
- dampers in air intakes/outlets serving air-heating/cooling equipment located outside the building envelope can be located within the equipment.
Air Flow Control Areas
Each air distribution system, serving multiple temperature control zones, and having combined conditioned floor area more than 2 500 m²,,must be divided into air flow control areas of not more than 2 500m², or one storey, such that the supply of air to each air flow control area can be reduced or stopped independently of other air flow control areas. Areas requiring full flow continuously are exempt. The zones within a given air flow area must be on the same occupancy schedule and have off-hours setback or on/off controls. Where air flow control areas are served by VAV boxes, the central system must have at least a 50% reduction in fan power for a 50% reduction in air flow. All central HVAC equipment must operate properly when serving only one air flow area.
Fan Power for VAV Systems
- Variable-air-volume (VAV) systems with 10 kW or more of combined nameplate supply, return and relief fan power must not exceed 2.65 W per L/s of design supply air delivered to the conditioned space (as calculated according to NECB Sentence 5.3.1.2[2]).
- Any individual supply, relief or return fan in a VAV system must be capable of meeting the power reduction requirements shown in Table 2.4
| Fan Power Demand | Air Volume | % of Full Design Power |
|---|---|---|
| 7.5 to 25 kW | 50% | no more than 55% |
| >25 kW | 50% | no more than 30% |
System Design
- All duct systems must be designed so that they can be balanced.
- HVAC ducts and plenums must be sealed as per the SMACNA HVAC Duct Construction Standard and NECB Table 5.2.2.3 unless:
- they are return air (R/A) ducts in conditioned spaces or in R/A plenums, or
- they are S/A ducts in conditioned spaces and are downstream of coils/boxes, or
- they are tested and proven to leak less than allowed by NECB 5.2.2.4(2).
- Special Temperature and Humidity Requirements:
Spaces with special process temperature requirements, humidity requirements or both must be served by air distribution systems that are separate from those serving spaces requiring only comfort conditions. Exceptions to this requirement include when the "comfort" air is 10% or less of the total; or the total design air flow does not exceed 3000 L/s.
5.6.3 Piping for Heating and Cooling Systems
Piping for heating/cooling systems shall have the following characteristics:
- All hydronic systems to be designed so that they can be balanced
- Pipes containing fluid with design operating temperatures outside a range of 13° C to 40° C must be insulated as per NECB Table 5.2.4.3, unless exempted as per NECB Sentences 5.2.4.3(2) to (6). Insulation must be protected where it may be subject to mechanical damage, weathering or condensation.
Pumping System Design
For HVAC systems with a minimum total pump system motor power of 7.5 kW, variable flow pumping systems must be capable of reducing system flow to 50% of design flow or less. Exceptions to this requirement include equipment with higher minimum flow requirements, and single-valve and resetting systems.
Insulation of "Outdoor" Piping
HVAC piping outside the building envelope must be insulated to the maximum requirement of NECB Table 5.2.4.3
5.6.4. Controls
Controls systems can be added or upgraded to improve the overall performance of the building, including the HVAC equipment. The simplest measure is to turn equipment off or otherwise ensure that it is in setback mode during unoccupied times.
Temperature Controls
- Each system intended to provide comfort heating/cooling must have at least one automatic space temperature control device
- Thermostatic controls for comfort shall have the following characteristics:
- heating controls must be capable of adjusting the temperature of the space they serve down to at least 13° C
- cooling controls must be capable of adjusting the temperature of the space up to at least 29° C
- The sensors of wall-mounted thermostats must be installed in accordance with manufacturer's instructions and are to be located as per NECB 5.2.10.4.
- Heat pumps having supplementary heaters must be controlled to prevent supplementary heater operation when the heating load can be met by the heat pump alone, except during defrost cycles.
- If separate space-heating- and-cooling controls are used, simultaneous provision of heating and cooling must be prevented.
- The heating/cooling of a zone must be regulated by individual thermostatic controls located in the zone unless a perimeter system is used, in which case there must be at least one space thermostatic control per orientation (provided that the orientation is at least 15m long).
Seasonal Hydronic Shutdown
Seasonal pumping systems, such as heating and chilled water pumping systems, must have automatic controls or readily accessible and clearly labelled manual controls to shut down the pumps when they are not required.
Electric Heating Systems
Electric baseboard heaters must be controlled by remotely mounted thermostats. If line-voltage thermostats are used to control electrical resistance heater units, they must conform to CSA Standard C273.4.
Shut-off and Setback
- Each HVAC system with a heating or cooling capacity of 2 kW or more must have automatic equipment shut-off or temperature set-back controls for periods of non-use, unless the system is intended to operate continuously. Unoccupied setback of heating setpoint shall not enable cooling, and unoccupied setup of cooling setpoint shall not enable heating.
- Heating or cooling equipment with capacities below 2 kW may be controlled by accessible, manual controls.
Humidification
Humidifiers and dehumidifiers must be provided with an automatic humidity control device. If the purpose of the humidity control is comfort, the controller must be able to prevent the use of energy to increase relative humidity above 30% or to decrease it below 60%.
5.6.5 Service Water
Storage Vessels and Heating Equipment
- If service water heaters, boilers, storage tanks and pool heater included in the scope of NECB Table 6.2.2.1 are not covered by local efficiency regulations, they must comply with the relevant standard of NECB Table 6.2.2.1
- Service hot water storage tanks located outside or in unconditioned spaces must be covered with insulation having a maximum U-value of 0.55 W/m². °C.
- Hot service water storage tanks within conditioned spaces must be covered with insulation having a maximum U-value of 0.8 W/m².° C.
- Tank insulation located where it may be damaged must be protected
- Service water heating equipment, other than hot water storage tanks, must be installed in a conditioned space.
Piping
All hot service water piping in circulating systems, non-circulating systems without heat traps, and non-circulating systems with electric heat-tracing elements along the pipes must be insulated in accordance with NECB Table 6.2.3.1 and NECB Sentences 6.2.3.1(2) to (4).
Systems With More Than One End-Use Design Temperature
When less than 50% of the total design flow of service water heating system has a design discharge temperature higher than 60° C, separate remote heaters are required for those portions of the system with a design temperature higher than 60° C.
Controls
Service water heating systems with storage tanks must have automatic temperature controls capable of setting temperatures between the lowest and highest acceptable settings for intended use.
- Except for systems in which the storage capacity is less than 100L, each service water heating system must have a readily accessible and clearly labelled device to allow shutdown, including any electric heat trace elements installed along the pipes.
- Electric heat trace elements installed along service water pipes must have automatic controls that maintain hot water temperature within the required range.
5.7 Additional Energy Conservation Measures
Any green office building must be designed to meet or exceed the requirements of the NECB using whichever approaches are appropriate and feasible. Compliance would be demonstrated by simulating the energy performance of the proposed building using the NRCan COMPLY software. The following measures supplement the measures listed above and will help the designer to meet or exceed NECB minimum energy standards.
5.7.1 Boilers
Most medium to large offices use boilers to generate hot water or steam for space heating. Recent trends in boiler systems include installing multiple small boiler units, lowering system steam pressures, decentralizing systems, and installing direct digital control systems (DDC). Gas-fired boilers having rated steady-state efficiencies over 90% are available. For boilers to run at peak efficiency, operators must tend to a number of operation and maintenance needs, described in the Operation & Maintenance section of this document. The following modifications can be evaluated for implementation as part of renovations or retrofits.
- Add radiator controls to each radiator or group, to allow occupants to maintain winter comfort without opening windows. Radiators that operate "wild" at full output are common in older office buildings;
- Replace inefficient boilers;
- Decentralize systems. Several smaller units strategically located around a large facility reduce distribution losses and offer flexibility in meeting the demands of differing schedules and loads. Estimate stand-by losses by monitoring fuel consumption during no-load periods;
- Downsize. Work to lower overall heating loads through prudent application of energy conservation measures. Small boilers may be staged to meet loads less expensively than large central plants;
- Modernize boiler controls with DDC devices, which allow logic-intense functions such as optimizing fuel/air mixture based on continuous flue gas sampling, managing combustion, controlling feed drum levels, and controlling steam header pressure;
- Install an economizer in the flue to preheat boiler feedwater. Efficiency increases about 1% for every 5.5 C° increase in feedwater temperature. Ensure that stack temperature remains above the acid dew point and that excess stack temperature is not due to a maintenance problem such as scaling;
- Install an oxygen trim system to optimize fuel/ air ratio;
- Install automatic flue dampers to reduce heat loss through the flue during the boiler off cycle;
- Retrofit standing gas pilots with electronic ignition;
- Add automatic blowdown controls to reduce waste from uncontrolled continuous blowdown;
- Add waste heat recovery to blowdowns. Use recovery tanks and heat exchangers to preheat feedwater;
- Consider retrofitting boiler fire tubes with turbulators when re-tubing;
- Ensure boiler casing and boiler piping are insulated with at least 25 mm insulation.
5.7.2 Air Distribution Systems
Fan motors in air handlers can account for 20% or more of electricity used in an office building. Energy costs can be significantly reduced by converting constant-volume (CV) systems to variable-air-volume (VAV) or increasing the efficiency of existing VAV systems. Good candidates for VAV conversion are CV systems with dual ducts or terminal reheat that use backward-inclined or airfoil fans. On existing VAV systems, convert airflow controls from inlet vanes or outlet dampers to variable frequency drives (VFDs).
- Convert constant volume systems to variable-air-volume. In CV systems, a constant volume of air is moved and heated or cooled regardless of the temperature and humidity needs of the space. The inefficiencies of dual-duct and terminal reheat CV systems can be virtually eliminated by converting the system to deliver only the volume of air needed to meet the actual load;
- Install a variable frequency drive (VFD) on fan motors to continually match fan speed and torque to changing building load conditions. The power requirement drops significantly as a function of this motor speed;
- Match fan speed to reduced building loads. Assess fan performance by measuring the fan on a peak cooling day. Reduce the fan RPM if vanes or dampers are closed more than 20% on a peak day. Lower the fan speed by changing pulley sizes;
- Evaluate changing fan belts to timing belt type drives. "Cogged" drive belts experience less energy loss than ordinary V-belts, are much more durable, and require less maintenance;
- Replace existing motors with properly-sized energy-efficient motors whenever the motor is due for rewinding or replacement, the motor runs a significant number of hours per year, and/or is significantly below current efficiency standards. High efficiency motors run at a higher speed than standard efficiency motors. The drives must be adjusted to account for this difference;
5.7.3 Ventilation and Heat Recovery
Heating or cooling the relatively large amounts of outside air required by ASHRAE 62 and the NECB requires a significant amount of energy. Existing office buildings usually do not have the capacity to provide this amount of conditioned outside air. Heat recovery applied between the building general exhaust (typically washroom exhaust) reduces the ventilation energy load by about 60 % and reduces the required capacity and cost of heating and cooling equipment by a corresponding amount. Heat recovery can also make it feasible to deliver ventilation at greater than minimum rates required by Code. Energy recovery techniques include plate heat exchangers, rotary wheel heat exchangers (with or without desiccant coating for moisture and latent energy transfer), heat pipes, or run-around coils.
5.7.4 Continuous Improvement
As part of an ongoing continuous improvement process an energy use monitoring and efficiency improvement team should be established. The team should be charged with ongoing monitoring and analysis of energy use in the building or suite (as appropriate), investigation and cataloguing of new trends and technologies in energy efficiency and recommending improvements for additional reductions in energy consumption in the building. The team should investigate wasteful practices that may be part of building operation or employee habits. Investigation of concerns and suggestions, providing feedback to employees on successes and providing constructive comment on potential areas for improvements are all essential components of the team's work.
5.8 Case Studies of Energy Efficient Office Buildings
5.8.1 First Heritage Savings, Town Centre Branch, Abbotsford, British Columbia
Project Overview
The First Heritage Savings Credit Union deigned the branch at 32711 South Fraser Way to serve as their 'flagship' branch. The branch was designed to provide the latest in banking services while maintaining the credit union image of efficiency and stability. The building is a two-storey 1021.9 m² (11,000 ft²), structure that incorporates state-of-the-art building techniques and materials to improve the overall quality of the building.
The design team for the project instituted energy efficient products, systems and controls in the building design to achieve maximum energy efficiency. However, the owners also wanted to create a building that would provide a comfortable environment for both customers and staff.
Environmental Achievements
Energy Savings
- The steel building is constructed with curtain wall glazing, insulated metal wall panels and stone veneer walls.
- A large skylight located over the center of the building allows for utilization of natural daylight.
- Perimeter glazing consists of a thermally broken curtain wall frame system, double-glazed with low-e, gray tinted glass.
Interior glazed partitions allow for utilization of day light from both the perimeter walls and the skylight.- The metal clad and veneer walls contain R20 insulation.
- The roof has been insulated to R24.
- An entrance vestibule limits infiltration of outside unclimatized air.
- Sheer-woven fabric solar blinds have been installed to reduce the solar gain from the west orientated windows.
- Reducing the number of lamps resulted in a lower electrical load and lower air-conditioning requirements.
Energy Efficiency
- Luminaries contain reflectors to direct light downward onto work surfaces. This feature reduced the number of luminaries required to provide the desired level of illumination.
- Luminaries were fitted with electronic ballasts to provide for efficient energy use.
The recessed down-lighting and exit signs are 70% more efficient than standard incandescent lamps.- Photoelectric day-lighting controls were installed in the areas affected by the skylight and in the areas that receive daylight from the exterior perimeter glazing.
- All lighting is locally switched or photo-electrically controlled.
Economic Factors
As a result of the energy efficiency efforts during the design of this building, the building was awarded the 1993 Power Smart Design Excellence Award in the under 4645 m² (50,000 ft²) category for Commercial buildings. The following tables provides a summary of the energy saved by the incorporated features:
* Savings listed are given as a percentage of technology energy use when compared to standard building practices
5.8.2 Ontario Hydro's Thunder Bay Building, Thunder Bay, Ontario
Project Overview
Ontario Hydro adopted the principles of sustainable development and seeks to incorporate these ideals into their business practices. The Hydroelectric business needed a new centralized Service Centre to house both office and industrial workspace. The recommendation was to amalgamate both its operations and office staff into one facility to improve productivity. Several alternatives to building a new facility were considered. However, the studies on each alternative determined that significant expenditures were required in order to adapt existing facilities to meet the established needs. Therefore, a decision was made to build a new facility on Ontario Hydro's property in Thunder Bay.
The building is a 13,000 square foot facility bordering a wetland site. Two work areas are clearly defined - an office area and a workshop. The office area was designed to maximize the comfort of the people that would spend most of their time indoors. To maximize the total sun exposure, the office area was orientated to the southern direction. The shop area is used on an as needed basis. Daylighting was identified as a high priority since intricate and detailed work would be done on the shop floor.
Environmental
Energy Savings
- Summer breezes from the south and west blow across the wetland bathing the building in cool air to take advantage of the local microclimate zone.
- Trees protect the building from prevailing northwest winds in the winter.
- A low retaining wall with a raised planting bed wraps around the building to reduce heat loss during the winter.
- Awnings were installed above each window to control the incoming sun.
- The office area of the building envelope includes a masonry cavity wall to act as a thermal mass and help regulate internal temperatures.
- To maximize daylighting in the office area a light shelf was installed at each window. The light bounces off reflective surfaces on the light shelf and the ceiling, reducing the need for artificial lighting.
- Solar light tubes provide daylight throughout the day to brighten dark windowless areas.
- The windows are high performance, triple glazed argon filled units with fibreglass frames. The glass is separated with silicone edge spacers and coated with a spectrally-selective low E-coating.
- The building was equipped with an evacuated solar water heating tube system to provide the hot water for the building.
- A south facing wall is covered with a dark coloured perforated metal siding system that captures the solar energy falling on it and raises the temperature of ventilation drawn through it, 15 - 20 degrees Celsius depending on the solar intensity.
Energy Efficiency
- The building was designed to exceed the requirements of the ASHRAE 90.1 standards. Annual energy savings achieved an additional 140,000 kWh compared to a conventional building.
- The heating, ventilation and air conditioning system is a water loop heat pump system capable of using alternative energy. The heating system was built to permit dual energy in the future with the flexibility to use gas, electricity or biomass.
- The offices are heated and air-conditioned with individual heat pumps.
- There are seven zones in the building featuring a separate mechanical ventilation system with automatic balanced heat recovery.
- Most spaces have separate controls to allow for individual adjustments.
- Motion sensors have been installed in areas of occasional use such as washrooms and meeting rooms.
- During the heating season, ventilation air is drawn from the 'Solarwall' into a heat recovery ventilator. This provides the two stage of ventilation pre-heat.
- Air exhausted from the building is passed through the ventilation air heat recovery units where 60% of the energy is recovered and transferred to the incoming ventilation air as the second stage of pre-heat.
- The ventilation air is reheated by a hydronic coil and supplied to each heat pump and to the shop area at 18 degrees Celsius.
Achievements
Economic Factors
The initial capital costs of sustainable buildings are higher than those of traditional buildings, but the overall life cycle costs (from construction to operation and maintenance) are significantly less. A comparison of the Thunder Bay building to a similarly sized conventional building showed a saving of almost $300,000 in life cycle costs. In addition to long term cost savings, benefits on daylight, indoor air quality and aesthetic appeal/comfort, make sustainable buildings very cost effective.
5.8.3 Other Case Studies
Details on four energy efficient buildings in Canada are presented below.
Bentall 8, Richmond BC
Type: Speculative office, completed
Gross area & floors: 7,435 m², 3 floors
Energy consumption 92 ekWh/ m² per year, 51% of NECB reference bldg
Added capital cost: 7% actual
Structure & bldg envelope type: tilt-up concrete wall, steel frame, steel deck, concrete topping
Windows: Double-glazed, spectrally selective, low-e, thermally broken aluminum frames
Mechanical systems: Condensing gas boilers, air-cooled 110 ton chiller, 4 pipe fan coils, small zones
Lighting: T8 direct, maximum daylighting
Other: Low emission materials, leases written to encourage energy efficient use of building
BC Government Offices, Kamloops BC
Type: Government office, completed
Gross area & floors: 4,182 m², 3 floors
Energy consumption 124 ekWh/ m² per year, and as 45% of NECB reference bldg
Impact capital cost: 4% est. saving
Structure & bldg envelope type: manufactured wood frame, rainscreen wall, ADA air barrier
Windows: Double-glazed, spectrally selective, low-e, fiberglass frames, insulating spacers
Mechanical systems: Gas boilers, 55-ton ton chiller, heat recovery chiller, 4 pipe fan coils, small zones
Lighting: T8 direct/ indirect, maximum daylighting
Other: Low emission materials, capture of rain water
Green on the Grand Office Building, Kitchener,Ontario
Type: Speculative office, completed
Gross area & floors: 2,174 m², 2 floors
Energy consumption 106 ekWh/ m² per year (as built), 58% of ASHRAE 90.1 reference bldg
Added capital cost: 7% actual
Structure & bldg envelope type: manufactured wood frame, double stud walls
Windows: Triple-glazed, spectrally selective, double low-e, argon, fiberglass frames, insulating spacers
Mechanical systems: 30 T gas absorption chiller/boiler, latent/sensible heat recovery, radiant htg/clg, displacement ventilation
Lighting: T8 direct/ indirect, dimmable electronic ballasts, photoelectric & occupancy sensors, maximum daylighting
Other: Low emission materials, storm water retention pond used as cooling pond for chiller
Yukon Power Headquarters, Whitehorse Yukon
Type: Office and control centre, under construction
Gross area & floors: 1,200 m², 2 floors + partial 3rd
Energy consumption 249 ekWh/ m² per year measured, 28% of NECB reference bldg
Added capital cost: (12% under budget)
Structure & bldg envelope type: wood frame, slab-on-grade
Windows: Triple-glazed, spectrally selective, low-e, argon, fiberglass or vinyl frames
Mechanical systems: Combination oil and off-peak electric boilers, groundwater cooling, 4-pipe fan coils
Lighting: T8 direct/ indirect, electronic ballasts, single-step daylight control, occupancy sensors