Energy efficiency measures - Residential - Model National Energy Code for Buildings (MNECB)
The existing MNECB is a prescriptive standard for medium sized buildings that is presently in the process of revision. The current MNECB's envelope minimum requirements are tied to the regional costs of energy. It will remain in effect until 2012, by which time a new code should be ready to replace it. In the existing code there are six major building categories with one, two or three sub-types in each group. The categories (with examples in brackets) are:
This template presents an example of a proposed residential building, comparing it to a similar MNECB reference building for the same location. In most cases, reference building information is extracted directly from the MNECB for the location of the building.
Template assignment
The Multi-Unit Residential Building (MURB) is a four storey, 59 unit building, with a floor area of 9,000 m² located in Calgary, Alberta, Canada. The reference (base case) heating system for this building is an electrical boiler which is replaced in the proposed building (proposed case) by a ground-source heat pump. For cooling, a conventional chiller is replaced by a system that bypasses the heat pump and uses the ground-source heat pump's underground piping system directly as a heat sink. In both reference and proposed, an in-floor heating system delivers the space heating, and forced air units deliver cooling. Ventilation is provided by a combination of corridor pressurization with under-cut apartment doors (make-up air for gas appliances in apartments), and energy recovery ventilators in apartments.
Electrical equipment in the building includes lighting, pumps, fans and plug loads. Lighting and all electrical equipment will have an impact on the heating and cooling loads except for the pumps and fans
Base case
Fuels & schedules
Proposed case
Heating system
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
The existing MNECB is a prescriptive standard for medium sized buildings that is presently in the process of revision. The current MNECB's envelope minimum requirements are tied to the regional costs of energy. It will remain in effect until 2012, by which time a new code should be ready to replace it. In the existing code there are six major building categories with one, two or three sub-types in each group. The categories (with examples in brackets) are:
- Commercial (boutiques through supermarkets)
- Business (banks, offices, clinics, rental shops, hair dressers, etc)
- Buildings for meetings (theatres, cinemas, auditoriums, schools, churches, libraries, museums, etc.)
- Health and detention centres (hospitals, prisons, orphanages, rest homes)
- Industrial buildings (divided into low, medium and high risk industries)
- Habitation (apartments, college residences, dormitories, hotels, motels, multiunit housing)
This template presents an example of a proposed residential building, comparing it to a similar MNECB reference building for the same location. In most cases, reference building information is extracted directly from the MNECB for the location of the building.
Template assignment
The Multi-Unit Residential Building (MURB) is a four storey, 59 unit building, with a floor area of 9,000 m² located in Calgary, Alberta, Canada. The reference (base case) heating system for this building is an electrical boiler which is replaced in the proposed building (proposed case) by a ground-source heat pump. For cooling, a conventional chiller is replaced by a system that bypasses the heat pump and uses the ground-source heat pump's underground piping system directly as a heat sink. In both reference and proposed, an in-floor heating system delivers the space heating, and forced air units deliver cooling. Ventilation is provided by a combination of corridor pressurization with under-cut apartment doors (make-up air for gas appliances in apartments), and energy recovery ventilators in apartments.
Electrical equipment in the building includes lighting, pumps, fans and plug loads. Lighting and all electrical equipment will have an impact on the heating and cooling loads except for the pumps and fans
Base case
Fuels & schedules
- The MNECB occupancy schedule for apartment buildings of 16 h/d, 7 days/week, is assumed
- Temperature settings are the same as MNECB defaults, 21.1 ºC for space heating, and 23.3 ºC for space cooling. Temperature is allowed to vary by 2 ºC during unoccupied periods
- Heating/cooling changeover temperature is 16 ºC
- Electricity rate is $0.069/kWh, natural gas rate is $0.28/m³
- Space heating is provided by a 100% efficient electric boiler
- Domestic hot water system has a natural gas fired hot water tank, 80% efficient
- Cooling is provided by a central chiller with COP of 3.8
- Building north side faces northwest
- Wall areas are: north and south 1,080 m², east and west 300 m²
- Walls are insulated to 2.7 m²-ºC/W
- Roof area is 2,250 m²
- Roof insulated to 7.14 m²-ºC/W
- The overall window-to-wall ratio is approximately 18%
- Windows are fixed double glazed, vinyl frame with aluminum spacers
- Solar shading on all windows is 10% during the winter. During the summer it is 15% on the north, 20% on the east and west and 40% on the south
- Natural air infiltration is 0.35 ac/h, building volume is 27,000 m³
- MNECB requires two ventilation sources for this MURB, a make-up air unit for corridor (including public space) pressurization and ventilators in apartments
- Corridor portion (4% of total floor space) is a constant flow system at 3,000 L/s with 15% fresh air and system reheat
- Apartment portion can be treated as a single-zone system with no zone reheat, total air flow is 25,000 L/s with a quarter of the air fresh from outside, ventilation fans run constantly
- Lighting power density is 9 W/m² in the apartments. However, including common areas such as lobbies, stairs and corridors, the average lighting power density is only 8.7 W/m²
- To account for continuous operation of corridor lights, overall building lighting is assumed to be on 6 h/d
- Electrical equipment plug loads (appliances & equipment) are 5 W/m² for apartments only, for about 8 h/d
- There are two pumps in the building: 7 kW motor drives a pump for the heating and cooling water system and 3 kW motor is used for circulating domestic hot water, duty cycle in both systems is 60%
- Corridor air supply fan is 7 kW, corridor exhaust fan is 1 kW, duty cycle is 70% in both cases
- 250 W air supply fan for each apartment, duty cycle is 70%
- The building uses natural gas fired hot water tanks in each apartment
- Hot water set point temperature is 60ºC
- Building hot water use is 14,000 L/d
Proposed case
Heating system
- Boiler to be replaced by a ground-source heat pump with a seasonal efficiency of 415 % at an incremental cost of $600,000 and an annual maintenance savings of $5,000
- Domestic hot water heating replaced with 85% efficient gas fired boiler at an incremental cost of $2,000
- Chiller replaced by system that bypasses the ground-source heat pump and uses the cold ground water directly as a heat sink, a COP of 8 is used to model this process
- Extra cost for bypass installation and controls is $4,000
- Windows are double glazed with a low-e coating, frames are vinyl and wood, U-value is 2.2 (W/m²)/ºC, solar heat gain factor 0.6
- Wall insulation to be increased to 4.5 m²-ºC/W, asssume labour costs equal materials costs
- Air infiltration to be reduced to 0.15 ac/h through attention to improved sealing techniques during construction, extra costs for this are expected to be about $8,000 for the building
- Corridor air flow is to be reduced to 450 L/s, all fresh air
- Ventilation system in apartments is equipped with 62% efficient energy recovery ventilators and air flow is reduced by three quarters, but all is fresh air
- Incremental cost for energy recovery ventilators is $1,000 per apartment
- Install motion and heat sensors in each apartment to shut off lights when rooms not occupied, cost per apartment is $200, reduces effective on-time for apartment lights by 1.5 h/d
- MNECB modeling guidelines state that the proposed and reference building must have identical electrical equipment plug loads. Operating hours are the same as for the base case building
- Install primary heating /cooling variable speed loop pump, driven by a premium efficiency motor, duty cycle is 40%
- Install variable speed circulating pump for domestic hot water, driven by a premium efficiency motor, duty cycle is 40%
- Incremental cost for the two variable speed pumps is $1,000
- Secondary loop pump system is added for the heat pump, also variable speed, driven by a 10 kW premium efficiency motor, duty cycle is 40%, incremental pump costs included in incremental costs for installing ground-source heat pump system
- Install air supply forward curved fan of 1 kW, premium efficiency, with constant flow, duty cycle is 70%
- No proposed corridor air exhaust fan, any excess corridor air is expected to escape into the apartments
- Apartments supply air fans are part of energy recovery units in apartments which are approximately 100 W each
- Fan replacements result in decrease in costs of $1,500
- Install low-flow shower heads and low-flow aerators in all faucets, these are expected to reduce hot water use by one third, assuming one shower head and three hot water faucets in each apartment the total incremental cost is $9,300
- Hot water set point temperature reduced to 55 ºC
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
