ENERGY STAR Homes: Common Reasons Some Candidate Homes Fail
Most ENERGY STAR candidate homes pass the required criteria for certification. Some don't, at least not w/out additional unexpected work or rework, schedule changes, extra site visits by the HERS rater (verifier) and maybe a little frustration for all involved.
Your HERS rater should work hard to let you know of the many criteria requirements for any candidate house. The ENERGY STAR criteria is regularly updated w/ new requirements that the builder and mechanical contractor and insulation / air sealing contractor need to be aware of. Part of the duties of being an ENERGY STAR partner such as the ENERGY STAR builder partner or the credentialed HVAC contractor is to keep up w/ ALL the itemized requirements that apply and will be verified by the HERS rater / verifier.
BELOW IS A LIST OF ITEMS, NOT IN ANY PARTICULAR ORDER, THAT OFTEN FAIL A CANDIDATE HOME, AT LEAST TEMPORARILY, FROM ENERGY STAR:
TOO MUCH DUCT LEAKAGE TO OUTSIDE: ITEM 6.5 OF THE CURRENT RATER FIELD CHECKLIST VERS. 3, REV. 8
Description: The rate must be less than 4 cfm per 100 sq ft. of conditioned floor area. It is extremely important that all parties agree on what the conditioned floor area is, before this testing. The rater is to field test this leakage rate at the rough or the final inspection. However, testing at the rough requires the house is pretty sealed up to do this test, therefor mostly done at final. However at final, it's sometimes difficult to remedy.
FIBROUS WALL INSULATION (fiberglass, cellulose, rockwool) NOT SEALED ON ALL 6 SIDES OF THE WALL CAVITY: ITEM 2 OF THE CURRENT RATER FIELD CHECKLIST VERS. 3, REV. 8
Description: All fibrous insulation in walls must be in complete contact w/ all 6 sides of the exterior wall cavity. 6 sides include: both vertical studs, top plate and bottom plate, outside wall sheathing, interior wall sheathing. This includes any wall that bounds a conditioned area to a non conditioned area. Kneewalls to attics, house walls to garages (whether heated or not) finished stairwell walls to unconditioned basements are all inspected for this.
CENTRAL AC AND / OR CENTRAL HEATING SYSTEM IS OVERSIZED: ITEM 4.2.8 OF THE CURRENT RATER DESIGN REVIEW CHECKLIST VERS. 3, REV. 8
Conventional ducted AC split systems must be sized in accordance with an accurate manual J load calculation that is conducted on the house. Load calculations are often shown to inaccurately represent the robust thermal building shell being built, falsely increasing the total projected heat gain on the house and subsequently increasing the amount of AC capacity that is installed. This can lead to rapid cooling but inadequate humidity control / reduction, leading to cool but damp or clammy conditions. Insist on reviewing the components and characteristics of window values and insulation values you intend to install, w/ the party running the load calc, and insist on minimizing the over-sizing of AC capacity installed.
INADEQUATE WHOLE HOUSE OR SPOT VENTILATION: ITEM 7 & 8 OF THE CURRENT RATER FIELD CHECKLIST VERS. 3, REV. 8
Kitchen and showered bathroom spot ventilation must be installed and must be field tested by the HERS rater to show adequate air flow rate, determined by ASHRAE 62.2 guidelines. Field tested flow rates for bathroom fans are often much weaker than manufacturer listed rates. Install ENERGY STAR labeled fans for best results and insist on clear exhaust runs of minimum length and turns.
Whole house ventilation must be installed. There are several ASHRAE 62.2 compliant strategies to do this. Flow rates here are sometimes the issue, especially on larger houses, but the system must have an adequate automatic control mechanism as well.
LACK OF ADVANCED EXTERIOR WALL FRAMING: ITEM 3.4.3 OF THE CURRENT RATER FIELD CHECKLIST VERS. 3, REV. 8
On conventional stick built / stud framed homes, ENERGY STAR requires minimized framing to increase insulated surface area.
All window and door headers need to be insulated to R5. There are some exceptions, refer to item 3.4.3 of the Rater field checklist, rev. 8 and its footnotes.
Framing limited at all window and door openings, limited to one pair of king studs, one pair of jack studs.
See further notes under section 3.4.3.
ICF wall construction and SIP wall construction generally aren't affected by these requirements. However there is generally some stick framed exterior wall construction in all houses that need advanced framing.
LACK OF ADEQUATE MANUAL AIR SEALING AT ALL ASSEMBLIES: ITEM 4 OF THE CURRENT RATER FIELD CHECKLIST VERS. 3, REV. 8.
Many areas of stick frame construction require manual air sealing using rigid sheet material, flexible sheet material, caulk, foam. Review item 4 of the rater checklist to see all the assemblies that require manual air sealing. It is substantial. ENERGY STAR is heavily focused on requiring very tight homes and then ventilating properly w/ spot and whole house ASHRAE guided ventilation strategies. Local minimum code compliance is also requiring the same air sealing strategies.
BEDROOMS NOT PRESSURE BALANCED: ITEM 6.2 OF THE RATER FIELD CHECKLIST VERS. 3, REV 8.
When a furnace fan comes on for heat and cooling, it may pressurize or depressurize any bedrooms where the door is closed. Excessive pressurization can lead to comfort problems and / or infiltration and ex-filtration issues. The rater is required to verify the pressure difference of the bedrooms in reference to the main body of the house and verify the difference is less than 3 pascals. If not, a duct return, transfer grill or door undercut will have to be installed to reduce the pressurization and satisfy ENERGY STAR compliance.
There are many more items that require compliance in order to achieve ENERGY STAR certification. Most builders today are complying with the majority of them whether they are looking for ENERGY STAR certification, or just local code compliance.
ENERGY STAR does not ask for more or higher insulation levels than minimum prescriptive code compliance and sometimes even less. They are asking for all building shell materials to be installed per manufacturers guidelines for reliable long term performance. They are requiring a review by a 3rd party of mechanical systems being installed, duct-work to be tight and for that duct-work to produce required airflow w/out excessive restrictions and noise. They are allowing customized solutions that minimize thermal efficiency of one part of the home as long as the energy consumption of the whole house is proven through software energy modeling to be less than the same house if it was built to modern minimum codes.
In other words, trade offs are allowed on one part of the building envelope or mechanical heating / cooling / hot water system as long as there are other components of the house that will maximize the thermal efficiency of the house, so the whole house, overall, will use less energy than if it was all built to minimum code compliance.
ENERGY STAR homes, on average, use 20% less energy, have more comfort, have better indoor air quality and less durability issues like ice dams and mold issues, than typical code built homes that are not 3rd party inspected by a certified HERS rater or other building science professional.