How to Spot Red, Yellow & Green Flags in Your Energy Modeling Projects

Electric Resistance Heating add remove

• While electric resistance heat is technically 100% efficient (in that 100% of the energy is being used to create heat), it is not very effective at heating a space and is expensive.

No Slab Edge Insulation in Climate Zones 4 and Up add remove

• Slab edge is no longer required for Energy Star Homes, but you’d have a hard time passing without it. Without slab edge insulation heat leeches out of the home through the concrete slab, also making the floors colder than the home. 

2×4 Exterior Walls in Climate Zones 4 and Above add remove

• 2×4 walls only allow for 3.5 inches of insulation, which not enough to efficiently keep up with winters in Climate Zones 4 and above. Fiberglass batts (which are commonly used) can only get to R-15 in 2×4 walls, compared to the R-21 fiberglass batts that can fit in 2×6 walls. 

Missing Kitchen or Bathroom Ventilation add remove

• Kitchen and bath fans that exhaust to the outside are both required by the Energy Star Program. They must be able to pull 100 CFM and 50 CFM respectively, though there are some exceptions. 

Gas + AC Combined PTAC Units add remove

• Integrated gas furnaces with PTACs have become popular for multifamily construction. They tend not to be the most efficient, but their deficiencies can usually be made for elsewhere in the model. 

No Listed Continuous Ventilation Strategy add remove

• Energy Star requires all dwelling units to meet ASHRAE 62.2 which requires an amount of ventilation based on the climate, infiltration, size of the dwelling unit and number of occupants. While there are plenty of ways to meet the requirements, taking into account design considerations early allow you to more to do so more efficiently. 

80% AFUE Gas Furnaces in Climate Zones 1–3 add remove

• Climate Zones 1-3 have mild winters. Since buildings there won’t have their heat on very often, they can sometimes get away with using an inefficient gas furnace. That being said, if more efficient models are cost comparable, it’s still beneficial to opt for the better system.  

ERVs/HRVs add remove

• Energy recovery ventilation or heat recovery ventilation are ventilation systems that recover some of the energy/heat from the air when they exhaust air and reintroduce that energy/heat to fresh air being brought into the home. They can be extremely efficient and will always model better than exhaust only ventilation.  

Triple-Pane Windows add remove

• Windows are one of the most important parts of the energy models, because windows are the least efficient part of the home. An efficient window model can be U-.25, which is only equal to R-4 while the rest of the walls are R-15-21. Triple pane windows are very expensive but can get down to U.15 or lower. While that may not seem like a huge change, it has a big impact on energy modeling and energy efficiency. 

Air Source Heat Pump Water Heaters add remove

• Normal electric water heaters can have an efficiency of .92 UEF, while heat pump water heaters can have an efficiency of 3.00 UEF or even higher. They are more expensive than normal water heaters but many rebates and incentives are available to defray the increased costs. 

High-Efficiency Air Source Heat Pumps add remove

• Air source heat pump technology has come a long way in recent years. They have become extremely efficient with some having SEER ratings in the 20’s and HSPF ratings in the up teens. Newer cold climate models can deliver significant amounts of heat even at well below freezing temperatures. Using newer, more efficient heat pumps has a positive impact on all energy models, regardless of climate zones. 

Geothermal Heat Pumps add remove

• Geothermal Heat Pumps take advantage of different temperatures in the earth’s crust to produce heating and cooling. They are very efficient and homes that use them can take advantage of many rebates, tax credits and incentives to make them more cost effective.