# Presentation: 034349

## Why HERS and Codes Have Historically Been (and Still Are) Hard to Mix

## Why HERS and Codes Don’t Mix—Scope Mismatches

- Space heating b
- Space cooling b
- Water heating ?
- Lighting ?
- Appliances ?

## Why HERS and Codes Don’t Mix—Mismatches between performance path and HERS rules

- Differences in reference house (baseline U-factors/SHGCs, distribution efficiencies, treatment of glazing area, assumed baseline system for electric heat, etc.)
- Different metrics of comparison (site energy vs energy cost vs normalized modified end use load)
- Differences in comparison methodology (e.g., AC modeled in home w/o AC?)

## Therefore...There is a HUGE disparity between code compliance and HERS scores

## Slide 5

## Why HERS and Codes Don’t Mix—”How much better” is irrelevant to the code

- Pass/fail only
- Performance calcs are a zero-sum game
- “Credit” for innovative features simply allows other features to be less efficient
- Upshot:  Tools to show code compliance can be much less sophisticated without compromising correctness
- Simplicity still rules

## Slide 7

## Ultimate HERS/Codes Vision

- A HERS Compliance Path in the IECC

## HERS Compliance Path—Why?

- Make “how much better” relevant—encourage builders to go beyond code
- Use DOE’s substantial codes infrastructure to promote beyond-code tools and programs (e.g., voluntary programs can lose their marketing pizazz)

## HERS Compliance Path—Why?

- Help work better-than-minimal efficiency into the residential construction/sales industry culture (e.g., would you buy a home that hadn’t had the plumbing pressure tested?)
- Help build up the necessary infrastructures so that the code can eventually require the really important things (actually-sealed envelopes and ducts, right ventilation, advantageous orientation, etc.)

## HERS Compliance Path—Problem:  Old Codes

## Slide 12

## HERS Compliance Path—Problem:  Old Codes

- Many are still in place
- Many will remain in place for many years to come
- Cannot be revised by IECC code changes
- Without impacting them, achieving HERS-in-code goal can take 10+ years

## Slide 14

## Idea:  HERS Mapping

- Mapping out the territory between HERS scores and code compliance

## HERS Mapping—Approach

- Identify which HERS scores comply with which codes, where, and under what conditions
- Basically, a massive simulation experiment covering
- All major extant codes
- All house types (size, shape, no. stories, foundation type, glazing percentage, etc.)
- All fuel/equipment types
- One (or two) HERS rulesets
- All U.S. locations

## HERS Mapping—Approach, cont’d.

- Would focus on prescriptive, not performance paths
- Find equivalence with what really happens in the field
- Avoid all the nasty nuances of old performance paths
- And...
- Would NOT seek to comply ALL houses

## HERS Mapping—Likely product

| Jurisdiction:  Philadelphia Area |  |  |
| --- | --- | --- |
| Code | Required HERS Score |  |
|  | To comply 75% of homes | To comply 90% of homes |
| MEC-95 | 81, no elec resistance | 82, no elec resist, no slabs |
| MEC-98 | 82, no slabs | 83 |
| IECC-2000 | 83, glazing < 17% | 84, glazing < 17%, no bsmts |
| IECC-2003 | 84 | 85 |

## HERS Mapping—Vision

- States/jurisdictions would use the resource to design HERS paths into existing codes
- DOE would develop generic recommendations/tools to help states
- DOE would use results to inform future code change proposals
- DOE would eventually propose a full HERS path to the code
- Energy Star link?