Written by Rafal Olan
The “Home Energy Rating System” (HERS) is a nationally recognized system for an analysis of a home’s energy efficiency. This includes protocols for inspecting a home, various testing methods, and all the calculations needed for a most accurate breakdown of house’s energy usage. The outcome of all these inputs into a computer software generates a HERS Index Score which is almost like a home’s ‘MPG’ sticker. The lower the score the less energy it uses.
The HERS Index Score compares your specific home to a ‘reference home’. To get a house’s index score, a certified Home Energy Rater has to conduct a Home Energy Rating and design the inspected home into computer programming. This encompasses all the construction details, the home’s shape, size, all the surface envelope areas and their insulation values, equipment efficiencies, and the testing results. This software compares these given specifications to the reference home of the same size and shape but minimum insulation values and equipment efficiencies. This reference home is an average newly built home to the 2006 IECC, International Energy Code Council, code minimums and is scored at a HERS Index of 100. An easy way of looking at it is that this minimum code compliant home will use a 100% of the energy, an average new house. The U.S. Department of Energy established that a typical resale home should be scoring about HERS Index of 130. Therefore, that average existing house will use about 130% of the energy compared to new construction, average reference home. You will also need to keep in mind that every older home is different and this HERS 130 is just an industry average. Same goes for the reference home, if you live in the 2009 IECC code jurisdiction, then your average newly code built home could be HERS scoring in the lower 90’s.
The HERS Index Score is a great tool for determining and comparing the true efficiencies of a house, either for new construction or for existing homes. In both scenarios, we can use the Index Score to see any differences in proposed efficiency upgrades to construction details. The better we can design and build a home the lower its energy usage will be. A house with A HERS Index of 60 will use only 60% of the energy compared to our standard, reference home, making it 40% more efficient. A score of 20 will use 20% or be 80% more efficient. And finally, if one builds a home with HERS Index score of ZERO, that house will generate all its energy needs on site and will not require any outside sources of purchasing energy. Along with the Index Score a host of different building reports are also generated from the Energy Rating and the energy modeling. From all those we can analyze the building in depth and see exactly where the home’s energy needs are. The HERS Index Score is the ‘MPG’ sticker and then some for our homes.
This week’s article comes from one of our senior energy auditors, John Matejka (read his bio here). He’s been in the industry for years so he really knows his stuff. He picked a great topic that has great information for EVERYONE (I even learned some things)….analyzing your utility bill. If you’re like me, you just pay your utility bill each month without even looking at it. But it is good to dive into your bill and really break things out. Hope you enjoy this read.
In comes John…
Do you know how much energy your home uses on a daily basis? You may look at your utility bill when it shows up every month, but do you consider what used all of that energy? The amount used by your heating and cooling equipment changes based on the conditions outside, but the rest of the appliances in the house operate on a steady basis(with exceptions such as vacations and long-term houseguests). These two portions are called seasonal consumption and baseline consumption. The baseline includes things like water heating, refrigeration, lighting, entertainment, etc. You can estimate your baseline consumption by looking at a full year’s worth of bills. Find the three months with the lowest consumption(summer for gas bills, spring and autumn for electric), and average them out; that is your baseline. You can then subtract that amount from the other months to see your seasonal consumption. Let’s look at two examples of electric bills.
This is a 1700 square foot home, inhabited by a retired woman. Her stove and water heater are both gas-powered. She has mostly incandescent light bulbs. Her attic insulation is rated at R-17, and her duct system is leaking 50%. The usage in her three lowest months averages out to 558kWh, or roughly 18.6 kWh per day. Subtract that from 1601 in July and we see that she used 1043kWh to cool her home that month, or almost an additional 36kWh per day.
This is a 1500 square foot home, inhabited by a young woman and her husband. She works from home every day, and conserves energy by keeping the air conditioning set in the high 70s. The water heater is electric and all of the light bulbs are CFL or LED. Her attic insulation is rated at R-4, and her duct system is leaking about 15%. The three lowest month average out to 329kWh per month, or roughly 10kWh per day. Subtracted from the July bill, we see she used 531kWh to cool her home, or 16.6kWh per day.
So what does all of this tell us? Both women are at home during the day and using electronics(television for one, computer for the other). The homes are similarly sized. One thing we can take away from this comparison is how easily baseline consumption adds up, and also how easily it can be reduced. CFLs and LEDs normally use 75-80% less energy than incandescent bulbs of similar brightness; a light turned off in an unused room uses 100% less energy than one left on. Conservation is equal parts performance and behavior. Both homes have performance issues in their insulation and duct systems, but one woman was more willing than the other to sacrifice a few degrees of comfort in the interest of conservation.
The main point here is that you can learn a lot about your energy usage from your utility bills. Analyzing them and learning what is going on in your house on a daily basis is a good first step towards saving energy and money.
Okay, okay, okay. I am a day late on publishing this week’s article. Better late than never, right?
So each day I get phone calls from people asking questions about getting an energy audit performed on their homes. What are the benefits? How long does it last? What does it involve? But there is one question that gets asked about 75% of the time. Any guesses? Here it is…
Is this utility incentive program a scam?
I give the same answer every time….No. So this week I thought it would be good to show you a real life example of a house we recently completed an energy audit and the energy improvements.
Here is the profile of the home we audited:
This was a pretty big job so here is what we proposed:
Look at those utility incentives! More specifically look at the duct sealing 1 incentive. These are incentives offered by Entergy of Arkansas. Here is the summary breakdown of this project:
The incentives covered 53.7% of the costs!
So to answer the question of how to get your utility companies to pay for 54% of the costs of energy upgrades?
Simply get an energy audit. It’s free in most areas.
Although it may not be 54% (I’ve see both lower AND higher…..up to 100%), the energy auditor can tell you how much they will pay during the audit.
Most people think about many things when building a new home…….
What people rarely think about is how to build an energy efficient home. I’m going to turn it over to our expert energy rater, Rafal Olan (see his bio here) to explain why you should get an energy model done on your new home.
In comes Rafal…..
Energy modeling for residential new construction is the ideal way of predicting the annual operating cost of the home as well as lowering those costs by implementing the most cost effective construction detail measures. Every new home should incorporate design and planing along with an energy modeling software. Unfortunately they don’t. Most homes are built by residential developers or general contractors that only build to the code MINIMUM. That is another way of building home the worst possible legal way. You cannot build any worse than that unless you’re in violation of the building codes. A home built to code only will have the least efficient heating and cooling equipment, leaky duct systems, the whole house building envelope will not be sealed, minimum insulation (a lot of times less than minimum), and all the energy features that can be incorporated into building an efficient home are disregarded because they are not enforced. When we actually calculate and enter the plan information into the modeling software we can see through numerous reports where the most energy usage goes to and where potential savings can occur.
The first part of the energy modeling for a new home is sitting down with the homebuilder, whether with a homeowner, a contractor or both, and going over the plans. Most of the time we will look at a completed set of construction plans so energy modeling does not dictate the architectural design of the style of home, the plan layout, or change your dream house façade. The detailing inside the walls is what’s important: what R-value insulation will be in the walls, on the ceilings, vaults, around the slab or in the crawl space. Air, or whole house infiltration, and duct system sealing will be the next hurdles to tackle since most builders and subcontractors have never done it. Finally, equipment efficiencies will need to be decided to fit into each specific budget. However, a home with a well-sealed and insulated building envelope (the conditioned space of the home) will not require super-efficient equipment to be installed. The heat or cool air is already contained within the home so the equipment does not need to have a large capacity any more, thus lowering the overall need for it. So once we have the plans and know what is the proposed basic insulation and equipment to be installed we can enter all that data into home energy computer software to do all the calculating for us.
Now we have our computer model of a new home to be built. From all the proposed construction details and specification we can now see how this home should perform in climate specific zones, what parts of the home use the most energy and which use the least. The reports generated from the software tell us this information in Btu’s and dollar figures so it could be easy to see where potential improvements could be implemented. The energy rater can look at each specific component of the home and change their value to see what changes occur. We can analyze each change in dollars saved of the annual energy expanses. This will let us see how much savings will occur if, for example, we change the wall insulation from R13 to R15, if we add slab insulation to an typically uninsulated slab, or we we’d install a tankless water heater instead of a traditional 40 or 50 gallon tank. Each of these changes will calculate different annual cost estimation. The builder can estimate cost of installing each of these changes. Comparing the two expanses and savings will let you decide if a measure is worth changing to. Some measures will not cost any more to install, some will pay back for themselves within a year or two, while others may be of a longer duration or some not worth at all. The energy modeling allows us to see the home as it performs when it comes to annual energy usage.
Going over this pre-construction energy modeling process will educate and allow us to make important decisions how to best build the new home. An Energy Rater together with the builder, the prospective homeowner, and/or architect can establish best construction detailing into the design and to work into the construction budget. The Energy report will closely predict the finished home’s annual energy bills and generate appropriate documentation for an Energy Loan. Energy modeling gives the most accurate predictions of how well the newly built home will perform when it comes to everyday living costs associated with it. So why do Energy Modeling on a set of new plans? To get the best analysis of the home’s building features and to know all the costs associated with living in that home.
When we complete energy audits, we usually come across high duct leakage after we complete our tests. The #1 reason is because of a leaky return cavity (usually where you change out your filter). In this return, you can see the open floor joists.
Have you ever felt around your return air grill when your unit kicks on? It’s sucking air, right? That’s because the air inside your home is cycling back into your duct system. Well, in this project where the return is open to stud cavities, the air being sucked in is not only traveling back through your return ducts but into the floor cavities, where it doesn’t need to go.
This is bad because you are now paying for air to condition between your floor joists!
And it allows dirty air to be sucked through the HVAC system.
Here is the before picture:
Having open stud cavities can cause poor air flow and also restrict the coils from cooling properly in the summer. Together, these two issues will demand more work out of the system and will raise bills, decrease the life of the HVAC system, and poor air quality inside your home.
So to fix this issue, we simply blocked off and sealed the open stud cavities so the air is traveling directly to the duct system.
Here is the after picture:
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