Energy Improvement Measures (EIMs)
The EIM is one of the key components of the Glimpse Calculator methodology. The Glimpse Calculator models EIMs as a process. They encapsulate the performance of a given technology in many different situations. They take the building’s current state, and go through a series of steps to identify how and where to implement that technology or operational improvement in the building, based on what is already there.
Categories of EIM
EIMs are processes that can be implemented in a building to save energy. There are three main categories of EIM:
These are actions that do not require large investment projects but can still significantly reduce energy consumption. These can be things like HVAC control improvements or behavioral shifts.
These measures include the installation of a specific type of equipment, whether in addition to current systems or replacing current systems. These can be things like replacing current HVAC equipment with heat pumps, installing occupancy sensors for lighting control, or installing variable frequency drives on pumps and fans.
These measures include installing equipment on site to generate energy. Rooftop Solar Photovoltaics, solar thermal panels, or combined heat and power plants are major examples of this type of EIM.
EIMs are applied to the base case of a building model after it is constructed using user inputs and building stock data.
In nearly all Glimpse Calculator usage methods, the user is allowed to select a package of EIMs to apply to a building. The main packages are:
- Residential Building Renovation Package
- Commercial Building Renovation Package
If a package of EIMs is applied to a building, it’s possible that certain EIMs will not apply. For example, the “Heat Pump Clothes Dryer” package is only applicable to buildings that contain a clothes dryer. In the case that an EIM does not apply, that will be shown in the calculator as an EIM with 0 impact over all impact categories.
Standard EIMs
Heat pump water heaters heat water for sinks and showers without directly burning fossil fuels, at a much more efficient rate than traditional heaters.
Replaces all domestic hot water heaters with heat pump water heaters. Changes supply temperatures to 120F. Energy factor for the water heater is set at levels corresponding to ASHRAE 90.2 (2 for capacities less than 210L, 2.2 for capacities over).
Air-source heat pumps use energy contained in the outside air to keep your home at a comfortable temperature without directly burning fossil fuels.
The current HVAC system is retrofitted to replace heat generation equipment with heat pumps of greater efficiency than that specified in Table 5-1 of ASHRAE 90.2 (p9). Cooling equipment is also replaced with equipment of efficiency equal to that of the same table. Boilers are replaced with ground-source heat pumps, central furnaces are replaced with air-to-air heat pumps.
Electric induction stoves transfer heat required for cooking directly from the pan or pot to the food, wasting less energy than all conventional types of stove.
Assuming all ranges and ovens are a single unit, each range/oven is replaced with a unit with induction cooktops and well-sealed electric ovens. Efficiency of the upgrade range is equal to 85% (EnergyStar estimate) and that of the oven is 70% (EnergyStar estimate).
Insulation and high-performance windows keep out unwanted heat during Summer and keep heat from escaping during the Winter.
External post insulation on the walls and roof is added to reach the U-value specified by ASHRAE 90.2 (Table 7-1, p11) for the climate zone. Windows and glass doors are replaced with windows having U-values and SHGCs taken from ASHRAE 90.2 (Table 7.1, p11) envelope tables. Infiltration is reduced to 0.01 cfm/ft2 for the window portion of the walls (ref: Alpen TR-11 PH+ sales material).
Heat pump dryers operate at a lower temperature and can reuse heat many times within a single drying cycle, whereas conventional dryers waste energy by dumping excess heat into the surroundings.
The current dryer is replaced by a high efficiency heat pump dryer with a combined energy factor of 11 (ref. EnergyStar equipment database).
Air sealing your home keeps comfortable air from leaking outside, taking load off your HVAC system.
Envelope air tightness is reduced to 0.25 cfm/sf as specified by ASHRAE 198 2020 p88, section 10.6.
Insulation and keep out unwanted heat during Summer and keep heat from escaping during the Winter.
ASHRAE reference E1.1.1 and E1.8. External post insulation is added to the exterior walls and roof to reach the U-value specified by ASHRAE 189 2020 (p141) for the climate zone. Envelope air tightness is reduced to 0.25 cfm/sf as specified by ASHRAE 198 2020 p88, section 10.6.
High performance windows not only provide extra insulation, but they also control how much solar heat is allowed into your building. They can be used for extra solar heating in the winter or blocking all solar energy to help your cooling system.
ASHRAE reference E1.4.1, E1.4.4, and E1.4.6. Windows and glass doors are replaced with triple frame equivalents. Glass doors have a U-value of 0.14 (Alpen Zenith ZR-9 sliding glass door), non-operable windows have a U-value of 0.10 (TR-11 PH+), and operable windows have U-value of 0.11 (same product line). SHGCs are taken from ASHRAE 189 2020 (p141) envelope tables. Infiltration is reduced to 0.01 cfm/ft2 for the window portion of the walls (ref: Alpen TR-11 PH+ sales material).
VRF is an all-encompassing conditioning system which has efficiency like that of a high-performance heat pump system. It saves extra energy when it can cool interior spaces and use the same energy to heat perimeter spaces.
No ASHRAE 100 equivalent. The whole HVAC system is retrofit with a heat recovery air-source VRF system with the efficiency specified by ASHRAE 189 2020 table B-10 (p119). DOAS units with DCV and efficiency specified in table B-1 (p109) supply ventilation air to spaces.
Air-source heat pumps use energy contained in the outside air to keep your home at a comfortable temperature without directly burning fossil fuels.
ASHRAE reference E5.3.7. The current HVAC system is retrofit to replace all heat generation units with heat pumps. For rooftop units with gas or electric heating coils, an air-source heat pump is installed. For PTAC’s, a PTHP is installed. For boilers, ground-source heat pumps are installed and radiators resized to accommodate the new working temperature. For buildings with more than two unit heaters, a heat pump water heater is installed to serve all unit heaters. All installed heat pumps have efficiency as specified in ASHRAE 189 Normative Appendix B.
Cool roofs help reduce cooling energy by reflecting as much solar energy as possible, keeping it from getting inside your building.
E1.2.1. Roof exterior surface is replaced with a highly reflective material with the following properties: smooth surface, aged solar reflectance of 0.87 and aged thermal emittance of 0.88, corresponding to one of the highest performing surfaces in the coolroofs.org material directory.
Commercial EnergyStar refrigeration equipment uses technology such as variable speed fans, hot gas reheat, and high efficiency compressors to keep your products cool efficiently.
ASHRAE reference E3.1.2 and E3.1.3. Replaces all reach-in and walk-in refrigeration equipment with EnergyStar rated equivalents. All open refrigerated cases are replaced with reach-in refrigerated cases. Savings percentages are sourced from EnergyStar databases.
LED is a proven technology which converts electricity to light with very little waste energy. It also reduces the cooling load in your building by reducing the waste heat from lighting fixtures.
ASHRAE reference E6.5.4 and E6.3. Replaces all lighting with lighting power density which meets the 2020 ASHRAE 189 LPD levels.
High efficiency rooftop units and chillers provide the same cooling and often equal system connections but trade first cost reductions for lifetime energy reductions, often resulting in higher lifecycle benefits.
ASHRAE reference E5.2.1, E2.2.18, E2.2.34. Upgrades chillers to the efficiency specified in 2020 ASHRAE 189 Normative Appendix B. Upgrades RTU DX cooling, window PTAC/PTHP, and other AC units to efficiency specified in the same Appendix.
Variable speed drives ensure that pumps and fans in your building only work as hard as needed to condition and ventilate spaces.
ASHRAE reference E2.2.1, E5.2.2. Converts all CAV (constant air volume) systems to VAV (variable air volume) systems, including installing variable speed drives on fans, upgrading terminal units to include dampers, and upgrading the control system if necessary. All ventilation systems are controlled by DCV (demand controlled ventilation).
Heat recovery in your HVAC system prevents the heat in exhaust air from being wasted, instead using it to preheat the outdoor air being brought into your building for air quality.
ASHRAE reference E2.2.18, E2.2.36. Installs heat recovery on all ventilation units with general building and general space exhaust air. Restroom exhaust is not used for heat recovery.
Packaging EIMs
Each EIM is applied to the baseline individually, and their results correspond to only completing that single EIM in a building. Packaging EIMs, or calculating the impact of implementing two or more EIMs in a single building, is not as simple as just adding the savings of two separate EIMs.
Why Package Impacts Differ from Individual EIM Sums
Two main reasons account can lead to the combined impact of two EIMs being different than the sum of the two EIM’s individual savings numbers:
- Mutually exclusive EIMs. In some cases, two EIMs act on the same system in a building, meaning that only one or the other can be implemented in a given building. In the standard renovation packages, there are only two pairs of mutually exclusive EIMs: a) Commercial 3 and Commercial 4 (heating system upgrades) and b) Commercial 3 and Commercial 8 (cooling system upgrades).
- Mutually dependent EIMs. In some cases, the result of one EIM impacts the savings, or even the ability to implement, of another. This calculation is not straightforward and requires a separate model to be run. An example of this is Commercial 1 and Commercial 4: the implementation of insulation and sealing will significantly reduce the heating and cooling loads in the building. That will allow a smaller equipment replacement for Commercial 4 (reducing the initial cost of the measure), but also reduce the savings that can be incurred because the heat pump will be required to perform less heating, cooling, or both (compared to if Commercial 4 was the only EIM implemented).
Custom EIMs
EnergyPlus is the gold standard of energy modeling in the industry. It can model the energy usage or impact on building energy usage of almost any technology in a building. That means that specific manufacturers and models of heating, cooling, lighting, envelope, etc equipment can be precisely modeled.
Our enterprise clients, whether using the Glimpse Platform, API, or completing a building stock or portfolio study, can request that specific equipment be modeled. Some examples of this are as follows:
- The impact of a specific manufacturer/model of a cold climate heat pump or a shading solution is modelled in hotels and multifamily buildings in every climate across the country. Results provide insight on where that technology saves the most energy.
- A portfolio owner with prototypical buildings across the northeast U.S. requests that three specific makeup air units from three leading HVAC equipment manufacturers be modelled in their buildings. Results provide insight on which makeup air unit is the best investment in which geographic regions.
- A municipality considering implementing a performance standard (such as Colorado Regulation 28 or New York City Local Law 97) has a list of recommended EIMs for compliance. The savings of each of the recommended EIMs is tailored to their geographic location, and the analysis of the results enable the municipality to make their compliance routes more equitable and informed.