Comments on: Everything You Ever Wanted to Know about the HERS Index

By: Ken Riead

Ken Riead — Tue, 19 Jun 2012 22:05:58 +0000

Thank you, Sean. Your
Thank you, Sean. Your explanation makes perfect sense. I had envisioned a bloated reference home floating around in the Energy Star universe with no tether. (Did you like this visual I've now planted in your mind?)

I shall sleep better tonight.

By: Sean @ AlaGBS

Sean @ AlaGBS — Tue, 19 Jun 2012 21:55:19 +0000

Ken – while certain programs
Ken – while certain programs have floating “refrence homes” (based on size, etc…) it does not apply to the base target or refrence home. This base target home is the exact same home but based on 04/06 energy standards which would give you the HERS 100 number.

By: Thomas A. Peterson

Thomas A. Peterson — Tue, 19 Jun 2012 20:21:26 +0000

Thanks for this much
Thanks for this much simplified explanation of what a HERS analysis is. I well understood it, but I am not sure that the average home buyer would understand all of the details.

By: kim shanahan

kim shanahan — Tue, 19 Jun 2012 20:14:04 +0000

John, the inputs should not
John, the inputs should not be substantially different from one rater to another. If both are being honest and not gaming the system the ratings should be virtually identical. One rater should be able to verify the other's number and the rater's provider (who they work under) is obligated to guarantee the veracity of the reports.

One doesn't need to test to come up with a presumed number, but one absolutely needs to test to come up with a verified number. Only a verified number can be used to accurately describe the home. The tests include blower door, duct blaster (unless it is a non-forced air heating) and visual inspection of insulation. They should also be inspecting for Thermal Bypass and air-barrier details, but that is not yet required for RESNET. It is for Energy Star, however, and many HERS raters are coming up to speed on how to do those inspections.

By: John Proctor

John Proctor — Tue, 19 Jun 2012 20:01:08 +0000

The real problem is that no
The real problem is that no two raters rate the same home the same. Just like Manual J, the inputs of course change the outputs and there is a lot of difference between what raters enter into the equation.

Someone can help me here, but it used to be that you did not have to do blower door or duct blaster tests to end up with a rating. I still bet you don't have to test anything about the furnace or air conditioner.

By: Ken Riead

Ken Riead — Tue, 19 Jun 2012 19:32:16 +0000

Not hard to tell that this
Not hard to tell that this was written by a PhD! ;-)

On a more serious note, my understanding is that the reference home is not static anymore but is a 'floating' reference instead. I find this to be troubling since I can't see how a person can re-create a rating down the road unless the reference home is always static.

Allison, do you feel up to providing some clarification on this? It would be most appreciated.

By: kim shanahan

kim shanahan — Tue, 19 Jun 2012 18:51:48 +0000

Nice overview Allison. &
Nice overview Allison.

I know many Building Science pros lament the rising juggernaut of RESNET and its HERS rating, especially those in the Northwest who have developed the arguably superior Energy Performance Score(EPS), but it clearly is becoming the dominant national measurement tool. I, for one, say if you can't beat them join them. Here in Santa Fe, NM, where we have had mandatory HERS ratings on all new homes since 2008 and mandatory minimum ratings of 70 since 2009, we have a well-developed cadre of top-notch HERS raters who have become somewhat of a pain in the neck to RESNET as they constantly collaborate, question, and prod RESNET to improve the process.

Most, if not all of them, are active members of our local HBA and its Green Building Council, which has been a tremendous asset to our organization and the continuing education of our members. There are still some bugs to work out, such as giving passive solar and thermal mass its proper due (trombe walls are still seen as windows and heat loss)and my own personal pet peeve is that the reference house assumes 13 SEER air conditioning. So even when you have NO air conditioning, which is not unheard of in our Zone 5 at 7000 feet, the reference house still calculates energy use as if you were running the AC. Another troubling area for me was when we designed a hydronic heating system using the Life Breath Clean Air Furnace that made its hot water with a combination of solar thermal backed up by an on-demand water heater, the calculation for energy consumption was based soley on the AFUE of the back-up water-heater.

Minor quibbles. The good news is that RESNET seems to be more open to the inputs from its growing army of raters and their providers, which can only improve the data. The other good news is that they are creating a tremendous national data base that can show how much energy and dollars are saved with every drop in the HERS index for every climate zone and for every mix of local utility costs. This is valuable micro information as we determine the cost/benefit analysis of energy codes that are demanding ever greater energy savings and therefore lower HERS indices. The NAHB and DOE would do well to help RESNET develop and perfect that data base.

Thanks for the informative article for the newly initiated.