What Is A HERS Score And Why Is That Important When Building A Home?

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What Is A HERS Score And Why Is That Important When Building A Home?

A HERS score is the recognized industry standard for determining the efficiency of a new home. So if a salesman for an energy efficient product tell you his company is selling something that you just have to have in your new home then he won’t mind sharing how using it will lower your HERS score or index. That’s usually when the salesmen sounds like Ralph Kramden from the old Honeymooners show, hamma, hamma, hamma. 

The HERS score levels the playing field when it comes to measuring the energy efficiency of a home or a product. Is the system perfect, not by a long shot but no system ever is. On the other hand, it’s the best system we have and it keeps getting better. 

So the next time you hear of some new energy efficient product that sounds like the best thing that happened since sliced bread ask, “how will this change my HERS score”? Then it’s time to listen carefully.

The next question should be, “how much will this new product save me on my monthly electric bill and what is my payback period? How long will it take before I start saving money over the cost of my initial investment”? Are you willing to wait that long?

Below is a example of questions we typically hear.

A. Is Spray Foam Insulation Worth the Investment?.

When it comes to energy efficiency, many of my Homeowners ask, Mike, how much "Green $$$" can you put in my pocket?

I respond, how much money are you willing to invest today for a potential payback sometime in the future? They usually respond, I'm willing to invest $10,000-$20,000 for energy saving features that have a payback period of 10 years or less.

Eventually, our conversation centers upon various insulation systems and the topic of spray foam attic insulation comes up.

Scenario 1:

Spray foam insulation applied to the underside of the roof sheathing in the attic, 5 inches thick, R- 15.

The attic space is sealed, soffit and roof vents are not required.

The attic becomes semi-conditioned air space instead of an over heated attic that reaches 150 degrees in the summer.

The air conditioning ductwork is installed in the attic that is now semi-conditioned air space.

Semi-conditioned because the attic is conditioned by air that leaks from the homes living space or cooled through contact with the ceiling drywall not by supply vents.

No insulation is installed on the attic side of the ceiling drywall.

An ERV (energy recovery vent) is installed in the attic to eliminate moisture build up.

System costs about $10,000 more than installing R-30, fiberglass insulation.

Scenario 2:

Blown in fiberglass insulation is installed on the attic side of the ceiling drywall to the depth of 10" for an R-30.

The attic space is ventilated, soffit and roof vents are required.

Even with ventilation the attic space can reach 150 degrees in the summer months.

The air conditioning ductwork is installed in this hot attic space.

An ERV is not required.

Evaluation:

Scenario 1's foam insulation seals better against air infiltration, the ductwork in run through semi-conditioned space, requires an ERV, its R value is lower and it costs $10,000 more that scenario 2. 

When both scenarios are evaluated by a Independent Certified Energy Rater taking into account all the various factors, they are considered equal.

Spray foam does not improve the HERS score at all over Scenario 2.

Summary:

So you can pay $10,000 more for scenario 1 and the payback period is never. 

I'm not a proponent of spray foam attic insulation due to its cost and payback period but I do install spray foam if my homeowners request that we do so. After all, it's their home and my job to provide information and assistance but they make the final decisions.  

B. What Insulation Package Do You Recommend 

Summary:

Exterior walls- concrete block, foam injected inside block cells, with radiant barrier applied over furring strips.

Attic- R-30 blown fiberglass with radiant-barrier roof plywood.

On 2 story homes- 2x6 exterior walls with R- 19 fiberglass batts.

The insulating systems outlined above provide excellent results with a payback period of less than 10 years. 

C. Should I Upgrade to Energy Efficient Windows?

How energy efficient are windows? Frankly, not very energy efficient at all!

Most single pane windows have an energy efficiency rating of R-1. Ok, so let's really make the windows energy efficient and install high efficiency, insulated, double pane, (Thermopane) windows. Wow, we just doubled their efficiency to R-2!

Now let's really get tough and add Low E glass! We just increased the efficiency to R-3!

Sure, you can add Argon and triple pane windows to your New Custom Built Home but how much energy will you really save? Last time I checked, the payback period for adding double pane, low E glass windows to your home is way over 15 years. That's 15 years before you save a dime!

I'm not against insulated windows but I think it's important to know what you're getting for your investment. I provide information to my homeowners, it's up to them to decide where they want to spend their $$$.

To put R values into perspective, most homes have R-30 insulation blown into the attic and insulated block walls an R-11.

If you want to save money on your future power bills look carefully at every window that the Architect draws on your plans. Don't make any exterior windows or doors any bigger than necessary. 

Remember, if you want to equal the efficiency of double pane, low E windows over single pane windows all you have to do is eliminate 18SF of glass on the outside of you home. That's just one 3' X 6' window!

One other thing to consider before you upgrade to double pane windows is seal failures. It's a common problem with insulated glass. Replacing one pane of insulated glass with a seal failure costs $200 each. 

There's a joke among Realtors, don't show a home with insulated windows until the afternoon. By then, the condensation in between the glass, due to broken seals, has evaporated.

If you decide to invest in insulated windows, check the warranty carefully to make sure that window seal failures are covered. Be careful of buying cheap windows as you usually get what you pay for.

D. Should I Upgrade My Air Conditioning System To A More Energy Efficient One?

Well, that depends? In the Orlando area the current building code requires a minimum SEER of 14 for your HVAC system. If you don't care how long it takes to recover your initial investment, get the highest SEER level that manufacturers make. On the other hand, if your goal is to recover your investment as quickly as possible, upgrading to a SEER 14 is the way to go.

 

Each home and it's variables (block, frame,type of windows, insulation etc.) are different. Most HVAC contractors have a Certified Energy Rater on staff that can run the numbers for you and tell you exactly how long the payback period is for each SEER level installed in your home.

 

For example, in a recent Central Florida Home we built, a SEER 14 level HVAC unit took just 5.5 years to recover their investment. On the other hand, the next highest SEER of 16 took 16 years. Way too long for most homeowners, unless they expect to live in their home 16 years or more.

 

I question whether a 16 SEER system will even last that long in the Orlando area?

 

I recommend a SEER level of 14 to my Customers as the cost for each additional SEER level has diminishing returns on additional dollars invested.

Below is more information on HERS score and Indexes from http://www.resnet.us/hers-index

What does a HERS Index score mean? A lower score means a more affordable, comfortable and energy efficient home.

The Home Energy Rating System (HERS) Index is the industry standard by which a home's energy efficiency is measured. It’s also the nationally recognized system for inspecting and calculating a home's energy performance.

What does a HERS rating say about a house?

The HERS Index measures a home's energy efficiency and there are a lot of great reasons to have a home energy rating performed on your house.

It can tell you so much about the home you live in, like how efficiently it’s operating and where you can make modifications for greater energy savings. When you're selling your home, a low HERS Index Score can command a higher resale price. And when you’re buying a home you can anticipate the costs of energy bills and efficiency upgrades.

How does the HERS Index work?

A certified Home Energy Rater assesses the energy efficiency of a home, assigning it a relative performance score. The lower the number, the more energy efficient the home.

The U.S. Department of Energy has determined that a typical resale home scores 130 on the HERS Index while a standard new home is awarded a rating of 100.

• A home with a HERS Index Score of 70 is 30% more energy efficient than a standard new home

• A home with a HERS Index Score of 130 is 30% less energy efficient than a standard new home

More on what the scores mean.

To calculate a home’s HERS Index Score, a certified RESNET HERS Rater does an energy rating on your home and compares the data against a 'reference home'– a designed-model home of the same size and shape as the actual home, so your score is always relative to the size, shape and type of house you live in.

Some of the variables included in an energy rating are:

• All exterior walls (both above and below grade)

• Floors over unconditioned spaces (like garages or cellars)

• Ceilings and roofs

• Attics, foundations and crawlspaces

• Windows and doors, vents and ductwork

• HVAC systems, water heating system, and your thermostat.

Public Access to RESNET National Rating Registry

RESNET has created a National Registry that contains information on certified RESNET HERS Raters and Home Energy Ratings. If you would like to confirm is HERS Rater’s certification is in good standing or the HERS Index Score of a home, this is the site for you.

Certified RESNET HERS Raters

The public can now access the following information on certified HERS Raters:

• The Name of the certified HERS Rater

• The Rating Company Name

• Location of the Rating Company

• Name and Contact Information of the Rating Quality Assurance Provider That Certified the Rater and is Responsible for the Quality Assurance Oversight

• Whether the Rater is Active or Has the Certification Been Suspended or Revoked

HERS Index Score of a Home

The public can now access the following information on rated homes:

• Address of Home Rated

• Rating Company Name That Rated the Homes

• Date That Rating was Completed

• HERS Index Score of Home

To access the RESNET National Rating Registry click on RESNET HERS Rater and Home's RESNET HERS Index Score Information

LEARN MORE

What is the HERS Index?