When there are hundreds of data points collected for each home and infinite variations of home energy components (and behavioral factors), can we realistically expect the data collection and energy predictions to be accurate?

In addition, quantification is great. But how do home energy ratings make a compelling reason to make home energy improvements when the energy savings is modest and the inherent value proposition of comfort, health and a modern lifestyle are not included in the home summary?

Keep in mind that I am asking about Ratings with software modeling, not Audits that are more subjective but still may use diagnostic tools like a blower door.

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I think so.  Ask one of the several national big home builders who recently decided to market their homes as Energy Star and have all homes built to meet Energy Star.  I can assure you that it is marketable if the big boys are involved.  While it is true that the energy predictions are only as good as the person collecting the data, RESNET has a quality assurance program designed to get everyone on the same page.  


As for improvements, are you talking about existing houses or new houses?  Energy Ratings usually refer to newly built homes.  Energy savings is not modest when you go from a code built house to an Energy Star house.  The requirements are becoming more stringent with time, and the savings in turn, more notable.  In addition, lifestyles will change as the price of energy continues to go up.  


When discussing existing homes, you must calculate a SIR or savings to investment ratio when making a recommendation.  Some investments cost more than they can reasonably save and should not be proposed by an energy auditor.  For example, windows - high cost, low savings- not a good SIR.  


Any home rating is geared to both measuring where you are now and making things better.  If this is the case, for an existing home (which is your question, I think) you have to know what is there to start - surface areas and R-values, air leakage, and equipment location and efficiency.  Specifically, if I am calcating a HERS rating, I get more accuracy if I use a blower door before and after any fixes than I do if I use the software defaults or guesswork.  

And SIR is not a good measure of payback.  This is a measure used by DOE and it calculates how many times an item pays for itself in its useful lifetime - they want 1 or higher.  So a fifty-cent item that last 6 months and saves fifty-cents in that 6 months gets an SIR of 1.  At the other end of the scale, added attic insulation that lasts 50 years and pays for itself in 50 years (say, adding R-8 to R-30 in my climate) also gets an SIR of 1.  

We use a simple payback - cost divided by annual savings.  It does not take into account the cost of money or increase in fuel costs, but is a number that a homeowner can understand.  So that 50 cent item gets a 6 month payback - excellent, and the 50 year item gets a 50 year payback - very poor, but they both have the same SIR.  We like 8-10 years as a payback, knowing that it will be better than that as fuel costs go up.  We operate in the Mid-Atlantic region.  And windows should not be on anybody's list.  

Cheers and happy saving.

Ed Minch


Two weeks ago here in Delaware, the state sold $83,000,000 in bonds to fix a couple of hundred state owned (commercial) buildings in less than 2 hours.  This is a first and a revolutionary concept, and it worked because there are 2 guarantees - the first one form the contractors guaranteeing because they CAN in a commercial setting, and the second from the state because they have the money they aren't spending on fuel.  The group that did this is now trying to work this magic in the residential sector, but the problems are just what you cited.  We as an industry have not yet been able to reliably guarantee savings (although my company has done it new houses for years).  Only when we get reliable savings and offer large groups of houses to even out problems can we find funding from the private sector and get away from this variable program funding (see New Jersey)

Ed Minch 

Tom, I disagree with this statement: 


"Some investments cost more than they can reasonably save and should not be proposed by an energy auditor."  


I guess the question becomes what is our job as energy auditor?  Is it to select only improvements that have high SIR for presenting to clients?  I don't think so.  I think our job is to present the homeowner with improvements and discuss the energy, comfort, health and safety benefits.  


Excluding energy opportunities from your modelling is not being comprehensive.  For example; windows on their own may be a terrible investment, but if the windows allow you to downsize replacement equipment, the windows value just jumped multifold. Now the equipment runs longer, which is more efficient.  The duct work to equipment ratio improved, more savings.  All kinds of things get better.  The savings is not based upon the energy not lost through the windows, but it is due to the windows, does that make sense?  I think the subtle interconnect here is lost on a lot of people, we need to make sure it's not lost on us!


"You want windows Mrs Smith, here is the energy benefit.  Let's discuss what other benefits you perceive and possible overall benefits because based upon the window savings alone that is not a great investment."  


I fear being less comprehensive misses interconnected or cumulative benefit opportunities.  Run the numbers and share them, or you risk becoming mediocre.  Presupposing what the homeowner will do leads to weak design.  Don't fall victim to mediocrity or our field suffers.  Excluding low energy savings improvements is a slippery slope that leads to taking shortcuts in our modelling.


I think we need to present improvements, educate and discuss how those improvements may or may not fit the needs of our clients.   Modelling things we assume they want or need, and eventually becoming less comprehensive, becoming sales people with impressive tools rather than true energy consultants.  


I generally agree, but on the topic of windows specifically, I don't. BPI, our Bible in the 5 states that we retrofit in, says a window with a storm is u-.49 and double pane replacement window is u-.49.  Looks like no recommendation can be made.  If we add Low-E, a calculation shows that natural gas or heat pump savings are about $4 per year, clearly not worth mentioning for a $3-700 investment.  New windows are great for ease of washing and lower maintenance, but the usual vinyl replacement has green issues that we should keep in mind.  You can now buy either interior or exterior triple track storms with hard coat Low-E for just over $100 - that might pass muster.

And In general, where do you stop when you give options? something that saves a buck or two regardless of cost?

Ed Minch

Ed & Ted,

You just made my original point.  Are we salesmen or energy raters and energy auditors?  Your approach may depend on whether you, or your company, also does the retrofit work.  Someone give me an authoritative organization that has done testing in the retrofit industry and has a better matrix for measuring energy improvement taking a "house as a system" approach.  In my humble opinion, the only reliable measure is the DOE's SIR.  A big stubling block for this industry is when we abandon science in favor of subjectivity, we run the risk of a loss of public confidence in the information and recommendations we make.  That hurts everyone.   


The bottom line is this: Did the $XX,000 Mr. Smith spend on energy improvements pay him back in a reasonable amount of time?  Or, did you just sell Mr. Smith a bill of goods?  Which approach garners public affection and which approach garners public shame? 

My point is that SIR does not do this - it merely says that the item will pay for itself over its useful life - something that is important to the government with the long view but useless to someone who has to justify the expense to himself in terms of comfort, investment and resale value.  My company started instrumented audits and retrofits in 1981 and I believe we are the oldest such business in the country.  In that time, we have refined our set of offerings to include only those things that are a good buy in our climate - let me repeat - in our climate. This allows us to offer these items at a very reasonable price because we can buy materials in bulk and we know just how long each item will take in labor.  We have done enough retrofits under enough programs that we have a good handle on expected savings.  We can do anything anyone wants, but we generally discourage long payback items.  We do not refer to SIR because of its limited usefulness.

Your mileage may vary.

Ed Minch

So, how do you measure success for the consumer?  Do you use a rating scale?  Do you offer a guarantee?   What assurances does a consumer have that what you come up with will save them money and will pay them back for the investment, make their homes more comfortable and raise resale value?  As a homeowner why should I invest in your proposal?


Tom Maides

So the bottom line is that as long as everyone is measuring lies equally and comparing lie to lie, we come up with truth.  Hence, a rating scale (like HERS) can measure to scale and then becomes marketable.  Genius! 



Ed Minch

I don't have a "Silver Bullet", but I know some companies are studying this very issue.  The solution will involve  a combination of things like: some statistical study of previous power bills of each home, an index or rating based on pure analysis (using visual inspection, blower door and duct blaster), and projections based on reasonable expectations given the previous data.  Index numbers don't lie and lifestyle changes can be detected using statistical analysis.     

Yeah.  Track savings and analyze results.  


You've done 100 jobs and I've done 100 jobs.  For every job I've done there is a promise of energy savings.  


Say for every $1 I promised I delivered $1.05.  Publish that.  Rate me on that. 


Say for every $1 promised you delivered $1.04.  Publish that.  Let consumers see it.  You get a gold star and I get platinum.  A marketing opportunity with transparent results, advertisements with theoretical percentages or vague savings.  


Guess what, now you and I are competing for RESULTS.  Instead of putting punitive pressure on quality there is reward pressure.  Good results for the homeowner mean good results for me.  Right now there is no transparency for results, utilities and program administrators lock that information DOWN.  


Who wins with results transparency?  Everyone but OPEC and big oil.  Consumers get better work.  Consumers can SEE that $1 invested has a real return, not a hypothetical one, so sales are simplified.  Improvements can now be quantified and taken to the bank, so access to money is simplified.  It's a win everywhere



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