Changes to ENERGY STAR Version 3 Announced by EPA
At Building Science Summer Camp a few weeks ago, I heard from Sam Rashkin that changes to the ENERGY STAR Version 3 guidelines and implementation schedule were on the horizon. This week, the EPA announced those changes—and some are rather curious. The email I received on Monday listed four items that had changed. Two of the changes are perfectly fine:
At Building Science Summer Camp a few weeks ago, I heard from Sam Rashkin that changes to the ENERGY STAR Version 3 guidelines and implementation schedule were on the horizon. This week, the EPA announced those changes—and some are rather curious. The email I received on Monday listed four items that had changed. Two of the changes are perfectly fine:
- The period during which homes can qualify under Version 2.5 is extended. It had been slated to end at the end of 2011, but they’ve extended it to 30 June 2012 now. Only homes that get permitted before 2012 are eligible for this extension. The rationale is that the economic downturn has slowed down construction schedules, so they’re giving builders some leeway here.
- Home builders will be allowed to use worst-case orientation when they have plans used more than once in various orientations. The rationale is that builders said they need more time to get ready for this.
Those changes seem reasonable, mostly. I think it’s a bit odd that the ENERGY STAR folks relented on the worst-case orientation and not some of the other issues, but OK, relax the schedule a bit and ease everyone into a bit more.
The other two changes,
however, seem like they were inspired by aliens. Well, OK, not the aliens I know because they pass on only good ideas. I’m talking about the bad aliens now.
- Through the end of 2012, HVAC contractors and designers are allowed to do their Manual J load calculations with the design temperatures for the local area…plus or minus 5° F.
- Also through the end of 2012, pressure balancing of bedrooms by installing dedicated return vents, undercut doors, transfer grilles, or jumper ducts will not be enforced.
Really?! I mean, really, ENERGY STAR, of all the things you could have done, you chose these? Adding 5° F to a 15° F ΔT has a significant impact on the cooling loads. I’m baffled. (As does allowing worst-case orientation in some cases, but that’s only for builders who use the same plan many times.)
And not enforcing the pressure-balancing requirement? Why? Of all the new requirements in the Version 3 guidelines, this is one of the easiest to accomplish and has generated no backlash, at least none that’s made its way to me.
I wish I could say that I had some input into these changes and heard ENERGY STAR’s reasoning first hand, but I didn’t. I know the folks working in the program are constantly tweaking and trying to improve it, and they get a lot of feedback from a lot of people. It must’ve made sense to someone to make these changes, but it sure doesn’t to me.
Don’t get me wrong. I love the ENERGY STAR new homes program and think that it’s really raised the bar for energy efficiency in new homes. They’ve done a lot of good work with the program, and Version 3 will continue that good work.
As I’ve written here before, though, they’re going farther than the HVAC industry is ready to go, in my opinion. I hate seeing myself write that, but I also know what a struggle it is just to get accurate Manual J load calculations with Version 2 of the program. The complaint I have with these new changes, however, is that they’re relaxing the guidelines in the wrong places.
Well, that’s the news. I wish it were better. I guess some people might find it good.
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Photo of alien by mendhak from flickr.com, used under a Creative Commons license.
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I found a solution to the
I found a solution to the Manual J problem, we simply hire Energy Vanguard to do them for us. We have the software to do so ourselves but find that outsourcing this makes the most sense. (next lunch is on you Allison ;))
Lance:
Lance: Awww. You’re too kind, sir. It’s great working with you and VisViva, though, and sure, I’ll buy the next lunch.
Allison
Allison You’ve given me much to talk about here, but it’ll have to wait until later.
From a Load Calculation perspective, I could care less whether the outdoor design temperature was adjusted from 95 to 105 degrees in Atlanta. After completing Manual S, the additional cfm required is negligible (500-800 cfm).
The real difference in sizing equipment is the indoor design temperature. I’ve got builders screaming 75 degrees is too hot! Their rationale is that when the temperature is above design, their clients still want to be comfortable. However, when it runs non-stop at the design temperature, there is little capacity left when temperatures soar.
From my knot hole, allowing the next higher design temperature has little or no effect on the size of the equipment, but it sure does make the HVAC contractor feel good–even if it’s for the wrong reasons.
Sam: Hmmmm
Sam: Hmmmm. I must be missing something. How is it that increasing the outdoor design temperature has “has little or no effect” yet lowering the indoor design temperature makes a “real difference in sizing equipment”? I think that in the calculations, ΔT makes no distinction between indoor and outdoor temperatures. If you increase the ΔT by a third, it will make a difference, whether that increase comes from inside or out. Or am I misunderstanding what you’re trying to say?
Allison
Allison Our first lesson in Manual S equipment sizing was that the outdoor design temperature is nearly irrelevant. It stunned the California Energy Commission when they finally understood it. It only about 500-800 degrees in 10 degrees.
The real derating of equipment occurs when the entering dry-bulb temperature at the return plenum is dropped from 80 degrees to 75 degrees. Depending on the SEER of the equipment, the cfm difference is 600-1500 cfm per degree! That’s nearly a half ton!
I think from what you’ve reported here, only the outdoor design temperature is allowed to move. If that’s the case, I don’t care.
However, the real point of contention is moving the indoor design temperature from 75 to 72 or less. This is supposed to be a decision between the homeowner and the HVAC contractor, but the government has decided I have to be comfortable at 75. Not! I run mine at 72 degrees year round. If the indoor design temperature is allowed to move, then you can expect the size of equipment to dramatically increase!
A contrarian point of view
A contrarian point of view about sizing. It might be time to worry less about AC over-sizing and worry more about infiltration and duct leakage. I live in Texas where over-sizing is chronic and have looked for recent published research which measures benefits from changing to right-sizing. The degree to which this fails to show up, leads me to conclude the benefits from right sizing are often overstated.
I submit that duct leakage to unconditioned space is a far greater contributor to energy waste, and outside air infiltration is a far greater source of excessive humidity. Gross over-sizing may be a comfort problem, yes. But terrible duct design I submit is the bigger robber of capacity and comfort.
Too often people grasp a valid principle (in this case sizing) and then exaggerate how that is the solution to too many problems. I do believe in sizing as small as will do the job, but there can be over-sized systems which do quite a passable job. In my own house I have two AC systems, one is definitely over-sized and runs 9-11 minute cycle times in the peak of summer. Yet it gives fine humidity removal… after the AC technician found and fixed a TXV problem that had been overlooked for years.
Remember that every system is over-sized every day except the design day, which in many regions is only a few days per year. Do we have problems in May and June because the temperatures are not like July and August? I think not. In Texas you often just cannot buy the furnace that is right sized for our winter design conditions, and that is no big problem.
When you work on mitigating the ill effects the typical over-sized design, I believe you will make more progress toward comfort and energy efficiency than if you focus on sizing.
Allison I
Allison I hope the orientation of the building is a non-issue for spec builders. My Right-J software shows the heat load for 8 points of the compass.
The only folks I can see complaining about this one are those with older computer models. Perhaps they can be imported into the newer versions of software.
M Johnson
M Johnson In modeling the heat load for an existing house, I haven’t run across one that was oversized yet. Most of my complaints is that the house is too hot, even with what appears to be an oversized system.
I usually spend my time figuring out what I need to do the ductwork and building envelope to get it to fit the size of the equipment.
I find out about oversized equipment in other ways–oddly enough with rules of thumb. Those are always on houses built averagely.
I have found exactly one system with what appeared to be an oversize equipment issue in a high-performance house. However, that turned out to be a problem with miscalibrated equipment and a bad TXV.
I’m especially watchful for oversizing on high performance houses though. ENERGY STAR wants me to get wrapped around the axle for equipment 15% oversized.
15% oversized according to who? The problem with Manual J is that it assumes perfect insulation. You can imagine my surprise when I showed up for a Pre-Drywall Inspection to find the builder switched from blown cellulose wall insulation to batts. All the sudden, my load calculation was grossly invalid. The equipment became way undersized immediately. Is it any wonder why the HVAC contractor is leery of installing right-sized equipment? There are too many variables outside their control. Who gets the bad rap in this case? It certainly isn’t where the true fault lies.
Following Manual J and ENERGY STAR requirements already allows for excessively oversized equipment. Manual J is 10-20% when the modeller is agressive about making it as small as possible. ENERGY STAR allows 15% above that, which is up to 38% oversizing.
I know this, but my HVAC contractor naturally wants to make it even bigger. I can’t and won’t let them.
With 38% oversizing, it’s easy to address the HVAC contractor’s concern about a call back when the temperature gets hotter than design. In my experience with project teams who take this subject seriously, there hasn’t been one complaint about not being comfortable above design conditions.
The funny part is that HVAC contractors read the sensible heat load reported by Manual J and then look at the ARI data to figure out what system to install. I have to laugh because it’s usually undersized! I think they get it close to being right only because they don’t do Manual S when they convince themselves they need a bigger machine.
I only smile after quietly doing the load calculation and equipment sizing in the background to discover the equipment is well within the 95-115% tolerance–despite there best efforts to oversize the equipment!
I hate to see them backing
I hate to see them backing off of the implementation goals. Change is never going to be easy or please everyone. At some point you just have to say “we’re doing this, deal with it”. I guess enough builders complained and the EPA listened. Designers and Builders need to work to meet the goal…not the other way around.
My guess: EPA, concerned
My guess: EPA, concerned about not just loss of penetration ratio but also feeling the winds blowing around massive debt reduction proposals that would dramatically reduce their budget (remember, some have proposed outright elimination), is trying to keep their eye on the prize of environmental protection but giving some ground so as not to be seen as promulgating “onerous regulation that cripple business.” I am not arguing for that strategy necessarily,…. just sayin’…
Allison, most of this is news
Allison, most of this is news to me. So they’re backing off bedroom pressure balancing (verify return path) but NOT backing off air balancing? I would have thought they would get much more resistance on the latter.
@Sam, although I agree that the 75F indoor design temperature mandate is controversial, you are incorrect when you say outdoor design temp is nearly irrelevant. An equal change to indoor vs. outdoor has a nearly equal impact on the loads. (I say “nearly” because attic loads are partly determined by a fixed temperature assumption that depends on roof type, not outdoor temperature.)
The rest of your extended comments make several good points but mixed in are some half-truths and some outright nonsense. For example, “Depending on the SEER of the equipment, the cfm difference is 600-1500 cfm per degree! That’s nearly a half ton!”
Methinks you either need to go back to school or stop writing about things you don’t understand.
But I do like your passion!
David Butler
David Butler Sorry you think I’m crazy! I can prove my case with real world examples with ease. I was in the same position as the California Energy Commission until someone who knows a heck of a lot more than I do proved their point.
I won’t write about things I don’t understand or have real experience with. If I wrong, thanks for improving my understanding. It will help us all!!! I promise, I’ll admit it! If you’d like me to discuss anything I have here, please contact me!
Sorry for the delay in
Sorry for the delay in responding. I had to run off and teach real estate agents a little building science this morning and then had a meeting and errands in the afternoon.
Sam: The loads come from Manual J, and I agree with David Butler that it makes little difference which side you adjust. Yes, you do have to make some adjustments when you’re selecting equipment, but I don’t know where you get those numbers from (600-1500 cfm/degree). Even if you divide by 10, it still seems too high. Besides, ENERGY STAR gives no wiggle room on the indoor design temperature. It’s 75° F.
Mark J.: I think no one’s making claims (anymore) to big energy savings from right-sizing air conditioners. John Proctor had an article in the Jan/Feb 2010 Home Energy magazine that supports some of what you say. Have you seen it?
Hunter D.: I have to say that I agree with you completely regarding all the changes above.
Tom M.: That may well be one of the factors at work here.
David B.: I agree that their choice of which balancing requirement to delay is a bit mystifying. I’m sure most HVAC contractors would rather install dedicated returns than balance the airflow in all their ducts, so I really don’t know where this came from.
@Mark, energy waste due to
@Mark, energy waste due to oversizing (cycle loss) clearly depends on how badly the system is oversized. A system that’s 200% of load will consume perhaps 10-15% more energy than a system that’s 25% oversized. The impact will obviously be greater if the duct system is located in a hot attic, since the system must overcome the thermal inertia of the coil, air handler and ducts at the start of each cycle. (A big reason to keep ducts out of the attic.) And it’s not just the heat picked up by the metal. The air inside the ducts gets very hot during off cycles, and then gets dumped into the house. The larger the system is relative to the load, the more often this occurs.
But energy efficiency is not the main concern. Moisture control is an important factor in most of the country. Your point about part-load conditions is a false argument. In areas with large latent loads during part-load conditions, the RH will increase even with a perfectly sized system. This is indeed one of the arguments for multi-staging. However a properly sized single-stage system, in most areas, can keep RH within an acceptable range in part load conditions. It’s all relative (no pun intended).
As you may know, many homes have low airflow due to poorly designed and/or restricted ducts. Since low airflow increases latent capacity, this may keep some homes with oversized equipment out of trouble in terms of moisture removal. However, running a colder-than-necessary coil has an even larger impact on cooling costs.
You said you have two systems, one of which is short cycling but seems to keep humidity under control. Water vapor tends to diffuse evenly throughout a building, especially if any separating doors remain open at least part of the day. A properly sized system with excess latent capacity will pull more than its weight.
Of course, there’s also a first-cost penalty with oversized equipment. And then there’s the comfort issue. The impact on temperature swing is real but usually doesn’t become noticeable unless the system is egregiously oversized (say, 3x) and the indoor-outdoor delta-t is large (say, 50F), as often happens with furnaces in tight well-insulated homes. Again, it’s all relative. Some folks just accept these swings as normal.
My comment is already way too long, but I should point out that in an existing home, unless the system is near the end of its life or otherwise in poor condition, it usually makes no sense to replace just to get sizing correct. If moisture removal is the issue, there are less expensive options to consider after-the-fact to deal with that.
Bottom line, I do agree that some folks tend to focus on sizing at the expense of bigger issues, and there’s no doubt that poor duct system design and installation practice is by far the most serious problem for residential HVAC. By the same token, we must be careful not to suggest sizing is unimportant. It doesn’t have to be either-or, does it? It’s up to us to advocate for the system approach.
@Allison, having not read Proctor’s article I don’t know what he came up with, but it’s very difficult to glean useful data when the errors inherent in normalizing for differences in weather, home design, thermostat settings, etc. are larger than the thing you’re trying to study.
David B.:
David B.: It’s been a while since I read it, but I think it was mostly an update on his thinking from the ’90s about sizing issues. Back then, he claimed that right-sizing resulted in big savings. Now he’s backed away from that and says it’s more like 2-3% (as I recall), but that reducing the utility peak load is a big factor in addition to comfort and moisture management.
Error Correction<
Error Correction Okay y’all! I finally figured out why I had everybody so stirred up yesterday. Put it down to don’t proofread your own stuff when your excited and time limited.
I know cfm and Btus are not the same thing. No I wasn’t doing any magic trick. It’s a simple matter that my brain was saying Btus and my fingers were 5 thoughts behind saying cfm.
I’m sorry! Allison, that for showing me what was driving you nuts.
Sam:
Sam: Thanks for clearing that up. Replacing cfm (cubic feet per minute) with Btu/hour suddenly makes your numbers sound reasonable. I can believe 600-1500 Btu/hr for each degree of change.
About the time of John
About the time of John Proctor’s “Bigger Isn’t Better” article, FSEC published a 2006 study on retrofit AC downsizing in Florida homes. On reflection their findings now seem unsurprising: Operating costs didn’t go down, and RH didn’t go up, for downsized equipment with leaky ducts. There’s more than that, it’s worth a look http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1641-06.pdf
Bob S.:
Bob S.: That FSEC article you referenced (linked here for our readers’ convenience) is a great one, and last year I wrote an article based on it: An Oversized Cooling System Isn’t Always a Bad Thing. In new construction, ENERGY STAR homes shouldn’t have that problem, though, since they have to meet the duct leakage requirements.
I believe the thinking behind
I believe the thinking behind allowing for the worst-case orientation to continue (new requirement will have the load calcs in +/- 25% groupings) was really more about allowing builders more time to implement changes to current processes (linking more than one load calc to each plan) and inventory and the amount of time that it will take to re-run load calcs and stock equipment in half-ton increments. Some of the larger builders are big ships to steer, so to speak.
The “energy star”
The “energy star” solution is simple. Limit equipment size based on sq ft, adjusted for region. if you live in Atlanta you are “allowed” 1 ton per 1,000 sqft.Design the building envelope to make to work if you want the energystar rating.
Houses in “worst case orientation” will need to make the difference up with less west windows or other energy improvements, NOT by increasing HVAC size. or the builder could simply not offer certain floor plans in certain orientations.