Published on February 18, 2014
Sub-Title Regional Cost-Optimization Study of Progressively Improving Energy Efficiency Towards Net Zero Houses Phase One of a four-year project lead by Natural Resources Canada
Project Goal • The Regional Cost-Optimization Study of Progressively Improving Energy Efficiency Towards Net Zero Houses, is part of a (NRCan) four year initiative. • The project aim is to: • Develop a framework and methodology to carry out regionallysensitive recommendations to reach certain milestone reductions (ERS 80, ERS 85, ERS 80 – 50%, ERS 80 – 75%, and 100% reduction) • Specify a series of recommendations for builders in the 35 Model National Energy Code of Canada for Houses (MNECH) zones.
Archetype Houses • Four archetype houses were used from plans commissioned by NRCan Archetype Descriptions For GTA Region Study Descrip(on Liveable Area m² (s.f.) Archetype 1 One storey with full basement 177 (1900) Archetype 2 Two storey with full basement and > 15% window area 325 (3500) Archetype 3 Two storey slab on grade 195 (2500) Archetype 4 Two storey end row house with full basement 139 (1500)
Baseline and Progressive Reductions • Each archetype is modelled for: Baseline (ERS 75 – OBC 2006); ERS 80; ERS 85; ERS 80 – 50%; ERS 80 – 75%; 100% reduction • The following information is presented for each progressive level of reductions for each archetype: • • • • Summary of energy reduction measures Reductions on fuel consumption Impact of increased insulation levels Impact of Alternate Energy Technologies (AET) and Renewable Energy Technologies (RET) • Impact of load management • Cost optimization (10 and 20 years) - Projected Operating Costs with Estimated Premium for Energy Reduction Measures • Net Present Value
Fuel Rates • An average of current fuel rates was determined via an online survey of fuel and power providers in the GTA region, carried out in March 2009. • For illustrative planning purposes, the current rate was used to estimate fuel costs for years 1-5. For years 6-10 the initial rate was multiplied by 150% and for years 11-20, the years 6-10 rates were multiplied by 150%. Projected Fuel Rates Electricity kWh Years 1-‐5 0.085 Years 6-‐10 0.128 Years 11-‐20 0.191 Natural gas m³ 0.385 0.578 0.866
Assemblies and Mechanicals • A variety of possible superinsulated and advanced wall assemblies are created and costed. • Current installed costs associated with various mechanical systems are also compiled.
Energy Modelling Tools • Hot 2000 (v.10.31) is used to model the reductions in energy use. • Drainwater heat recovery reductions is measured using the online calculator developed by Natural Resources Canada and hosted at www.ceati.com/calculator/. • To get to Net Zero (100 on the Energy Resource Station [ERS] scale), the modified ERS rating developed for the EQuilibrium Housing Initiative is used. • The performance and sizing parameters for the 6m2 collector solar hot water system and the PV systems associated with each house in various scenarios are based on RETScreen results for such a system in Toronto as modelled in the CMHC study Approaching Net Zero in Existing Houses.
Financial Valuation Methods • Accepted methods of analyzing return on investment (Net Present Value in this instance) assess the attractiveness of an investment against the baseline ERS 80. • Planning assumptions for cost of capital are included in the calculation of ROI (Net Present Value). • A high hurdle rate of 7% is used in order to generate conservative results.
Archetype 2 – 2 Storey w/Basement
Energy Reduction Measures • The space heating scenarios for this archetype changes delivery systems: • The ERS 85 reduction scenario shows a 7 kW, COP 3 air-to-air heat pump, increasing the electrical load, but, in conjunction with further envelope improvements, reduces the space heating energy use by 13%. • In the 75% and 100% reduction scenarios, a combination solar thermal system with a high-efficiency instantaneous water heater is modelled to handle both space and water heating.
Reductions in Fuel Consumption • Envelope improvements from ERS 80 to ERS 85 drop natural gas consumption for space heating by 70%. • The ERS 85 shows the change in electrical use where an air-to-air heat pump is modelled. • Where the heating system changes to a lower-efficiency air handler (75% reduction), there is a less impressive drop in the space heating fuel use. The electrical load increases due to ventilation and the lower efficiency air handler.
Reductions in Fuel Consumption Reductions in Fuel Consumption Code 2006 ERS 80 ERS 85 ERS 80 -‐50% ERS 80 -‐75% ERS 80-‐100% Natural gas space hea(ng m³ 2,843 1,795 473 745 372 372 Natural gas DHW hea(ng m³ 711 406 406 406 83 83 1,392 893 6,005 1,074 1,049 0 233 545 776 914 914 0 8,761 8,761 8,761 8,761 8,761 0 Electric space hea(ng kWh Electric ven(la(on Electric baseloads kWh
Impact of Increased Insulation Levels • Most significant is the reduction in space heating requirements over the first four scenarios (Code 2006, ERS 80, ERS 85, ERS 80 – 50%) as these relate directly to the envelope improvements. • Where solar thermal is brought into play (75% reduction scenario, column 5 next page), the DHW and space heating loads are so low as to allow for a cost-effective system to supply up to 50% of the space heating requirements and 90% of the DHW needs. • Where ventilation (red bar) is a fairly constant, small portion of overall energy use, the more space heating can be integrated into a ventilation scheme (as opposed to ventilation being integrated into a space-heating system), the less electrical energy will be required.
Impact of Increased Insulation Levels 140,000 120,000 100,000 80,000 DHW 60,000 Ventilation Space Heating 40,000 20,000 0 2006 Code ERS 80% ERS 85% ERS 80-50% ERS 80-75% ERS 80-100% Aggregate Reductions in Space Conditioning Energy Use, MJ
Impact of Alternate Energy Technologies (AET) and Renewable Energy Technologies (RET) • The drainwater heat recovery unit can save up to 73 m3 of natural gas annually (equivalent to 2774 MJ, assuming 1 m3 = 38MJ), even more when the load is dropped by 150L/day. • AET and RET measures are carried out only in the 75% and 100% reductions after all envelope improvements are carried out. • The 6.8 kWp PV system introduced in the 100% reduction scenario produces enough power annually to compensate for the energy used by the natural gas fired water heater that provides back up to the solar thermal combination space and water heating system.
Energy Reductions Through AET and RET ERS 80 -‐50% ERS 80 -‐75% ERS 80 -‐100% Design heat loss Btu/hr 37,000 No change No change Design heat loss W 10,838 No change No change Space hea(ng MJ Ven(la(on MJ DHW MJ Baseload MJ Total MJ Total MJ PV produc(on 28,286 3,293 15,064 31,536 78,179 7,240 1,411 14,928 31,536 55,115 7,240 1,411 14,928 13,140 36,719 36,000 Target reduc(on from ERS 80 59,186 29,593 0
Impact of Load Management • A 7kW air-to-air heat pump is modelled in the ERS 85 reduction scenario to see how much electricity use increases when the envelope is reasonably improved. • The amount of electricity required for space heating and ventilation increases to just over 6,000 kWh annually (about 16 kWh/day). • If the baseloads are dropped from 24 kWh/day to 10 kWh/ day, this combination of envelope improvements and space heating system would only increase the electrical consumption by 2 kWh/day (730 kWh/year) over “typical” electrical consumption in a Canadian household of four.
Cost Optimization (10, 20 years) Projected Operating Costs with Estimated Premium for Energy Reduction Measures 2006 Code ERS 80 Diﬀerence in cost from ERS 80 ERS 85 ERS 80 – 50% ERS 80 – ERS 80 -‐100% 75% $7,750 $17,170 $30,857 $83,757 Current annual gas & electric cost Year 6: fuel cost increase 1 $2,133 $1,638 $1,477 $1,070 $944 -‐$5,246 $3,199 $2,458 $2,216 $1,605 $1,415 -‐$5,230 Year 11: fuel cost increase 2 $4,799 $3,686 $3,324 $2,407 $2,123 -‐$5,206 Total projected opera(ng costs over 10 yrs $26,660 $20,480 $18,465 $13,375 $11,794 -‐$52,380 Total projected opera(ng costs over 20 yrs $74,650 $57,340 $51,705 $37,445 $33,022 -‐$104,440
Net Present Value ERS 85 50% 75% 100% Year 0 from baseline NPV Year 20 Year 0 from baseline NPV Year 20 Year 0 from baseline NPV Year 20 Year 0 from baseline NPV Year 20 1 Storey -‐10,359.94 -‐6,473.23 -‐15,893.09 -‐7,662.99 -‐29,683.69 -‐18,533.49 -‐71,383.69 -‐4,818.43 2 Storey -‐7,749.69 -‐4,756.94 -‐17,170.49 9,389.59 -‐30,857.49 -‐18,110.85 -‐83,757.49 -‐1,216.93 2 Storey SOG -‐6,692.43 -‐5,853.76 -‐13,424.99 2,845.35 -‐25,259.75 -‐19,215.57 -‐74,059.75 -‐4,371.04 Row end -‐7,411.94 -‐2,861.27 -‐9,703.08 1,968.37 -‐22,335.56 -‐16,713.64 -‐63,935.56 12,457.08 The best investment for 2 Storey is 50%. This illustrates the importance of archetype in accessing best investment. Assumptions Cost of capital 7% (a high hurdle rate in order to generate conservative results) Initial investment in energy savings measures made at once at the beginning of Year 0 Consistent annual cash flows for Years 1…n
Some Key Findings
Improve Typical Assemblies First • The Ontario new home market is price/location driven first, and specification driven second (by consumers). • The production housing market in Ontario tends to deal poorly with dramatic changes. • Therefore… • The most effective starting point is to improve typical assemblies before looking at the use of different materials. • Modifying typical wall assemblies allows production builders to quickly and easily compare cost differences, as the original assembly is familiar and a revised assembly would be easy to benchmark within current costing databases.
Market and Labour Constraints • One way of reaching better air tightness goals is to use closed cell insulation in the stud cavities with a few inches sprayed on the attic side of the ceiling prior to loose fill being added. • ICF foundations would also likely need to be implemented to achieve NZE performance • However, in Southern Ontario, there are significant hurdles to overcome in order for production builders to bring down air leakage levels to achieve substantial reductions past ERS 80, including: • Extreme price sensitivity of the market (housing as a commodity) • Scheduling concerns • Labour and union resistance to new construction methods
Major Shift in Focus Away from Space Heating • As the envelope improvements reduce the heating load, the relationships between the various end uses change in the house. Appliances and other internal gains, such as occupants and available passive solar gain begin to play a stronger role in the space heating regime.
Space (inc fans/pumps) 46% Plug Loads 28% Ventilation 2% Water 24% Conventional Envelope, 4 to 5 ACH
Plug Loads 45% Space (inc fans/pumps) 30% Ventilation 8% Superinsulated envelope 1 ACH Water 17%
Preparation for Solar & PV Makes Sense • Solar ready features (preplumbing, prewiring) are achievable in cost-effective manners and also provide marketing opportunities. • Current costs for renewables, such as PV, are not in line with production builder pricing at this point, but preparation for these items makes sense as building envelope improvements are made.
ROI Analysis • The ROI analysis calculated Net Present Value (NPV) for all archetypes for all scenarios compared to the ERS 80 baseline. • The findings indicate the importance of the house type in determining the best investment in energy savings. • For example, current costs for materials, labour and fuel (as well as Ontario’s premium on green power production) show that the 50% reduction scenario is the best option for both Archetypes 2 and 3 (2 storey with basement and 2 storey slab on grade, respectively) • While the 100% reduction scenario is the best option for Archetypes 1 and 4.
Constraints Posed by Common Building Practices • The parameters required by the GTA builders who participated in the study required that, out of several proposed options, the most expensive wall assembly be used – a 2x6 assembly with 25mm (1”) rigid foam to the exterior and the stud cavity filled with a high-density closed cell foam (RSI 0.041/R-6 per unit thickness). • With better market penetration, the cost of the closed cell foams (or other, lower cost materials with equivalent high insulation and good air sealing qualities) could drop, making this type of wall assembly more cost effective. • Where material costs can be reduced, the ROI analysis would change dramatically.
Future Directions • Additional analysis carried out in other zones as part of The Regional Cost-Optimization Study of Progressively Improving Energy Efficiency Towards Net Zero Houses will assess the impact of zone on cost optimization and return on investment. • Future research may include sensitivity analysis and stochastic modelling for variables such as cost of capital and fuel costs to provide a more robust analysis of ROI.
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