What would a Class I, II, and III energy code look like ?
We are building a new house and struggling massively on the energy side. Architects and builders that we like don’t know much about energy efficiency (nor IAQ, Low VOC, etc.) and those that know energy efficiency largely build very contemporary styles. We may be faced with trying to marry the two which could be prohibitively expensive unless we can get them to fall in love with each other before work begins.
Even just communicating what we want is difficult. The easiest is air tightness where we can specify an ACH50 of 1 or 2.5 or 3.0. Thermal bridging OTOH gets complicated. “We don’t want any thermal bridging.” or ” We want less than 35% thermal bridging per sq ft of exterior surface.” Passive House (or Haus) is on the extreme end and I’m less and less inclined to believe it nearly as beneficial as it costs. Pretty Good House sounds like great ideas but nothing concrete ever came of it (though the discussions still likely advanced energy efficiency).
One saving grace for us is the new 2015 energy codes. At least it’s forcing builders to become familiar with air tightness and we know we’ll get an ACH50 of 3 or better and a somewhat decent level of insulation. Sadly not much in the way of anything else. What I would like is if code were ‘Class III energy efficiency’ and we could also say we want our house to be Class II or Class I.
What would a Class II or I house look like?
Class II: ACH50 = 2? Insulation of 20/40/60? Some reduction in thermal bridging? Windows of some certain spec on what faces?
Class I: ACH50 = 1? Insulation of 20/50/80? Some spec of solar gain in winter (in northern climes)?
Building an energy efficient home seems far more art than science. But can we get it to be science enough that even architects and builders can do it?
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Replies
W.,
If you want to build an energy-efficient house, someone on your team (the homeowner, the architect, or the builder -- or ideally, all three) needs to understand the topic well enough to address issues like thermal bridging. If you find that local builders and architects don't understand these issues, don't give up -- keep looking until you can assemble a team you can trust.
Thermal bridging matters for framed walls and framed cathedral ceilings, but usually not for the floors of unconditioned attics. The solutions for walls and cathedral ceilings are fairly well developed -- double-stud walls, for example, or SIPs, or wall assemblies and roof assemblies with exterior insulation. Choose a system you like.
The major remaining thermal bridging issues are penetrations like structural beams that penetrate the thermal envelope, or massive masonry chimneys. If you are alert to these issues, you should be able to nip errors in the bud.
To keep things simple, you might consider setting a HERS score goal/requirement for yourselves and your team....perhaps 50 or lower (not counting PV)...perhaps 40 or lower, if you want to be a bit more aggressive. Even with a Passive House, the lowest score you'll likely able to get (before PV) is in the low-30's for MN.
Side note on your post - I find it hard to professionally like architects and builders who are not up to speed on energy efficiency, IAQ, occupant comfort, cost, and other such things. I'm OK with liking them personally, though...
If you go with 0.5-0.7x IRC 2012 code-max U-factors on all building assemblies you wouldn't hit PGH levels until US climate zone 6, but would have a fairly high performance building. See Table N1102.1.3:
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm
So, where are you, climate-zone wise?
Another good starting point it Table 2, p10 of this document:
http://www.buildingscience.com/documents/bareports/ba-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones
Note, those are all "whole-wall" R values, with the thermal bridging factored in. eg: A 2x6/R20 24" o.c. wall with wood siding typically comes in around R15 whole-wall, or a U-factor of about 1/R15= ~U0.067.
The shape of the house makes a difference on how much exterior surface area there is per square foot of conditioned space, which affects efficiency at any given U-factor. But every corner also introduces thermal bridging and a potential air-leak point. Avoiding unnecessary bump-outs and dormers & bay-windows etc introduced only for architectural excitement, and try to limit the total number of corners to 6 or 8.
Orient the ridgeline & roof pitches to be able to take advantage of solar panels, even if you don't install them as part of the initial build (but don't rule out solar as part of the initial build, since that would enable financing it at mortgage type rates).
Mr. Ramsey, I echo the above responses from Mr. Holladay and Mr. Semmelhack. If a architect doesn't understand HERS ratings I wouldn't be using them if energy efficiency is important to you. If an architect can't design in the style you want then you have to pass them by as well. You can also use a "designer" instead of an architect. That's what I had to do. I did have to coach them a little, but I got a decent plan out of it.
You can assemble a team in a few different ways--one would be to include an energy efficiency consultant to advise the architect. Another would be to use an designer as Andrew suggests, perhaps using the money saved on the architect to hire the efficiency consultant. It's also possible that the architects whose work you don't like would be willing to design in a style you do like. If you discuss it and they are unwilling, drop it but it might be worth having the conversation if you haven't.
Thanks all. On a quick note I'm thinking about my own house but almost more about the 99.9% of houses that are built to code minimum because anything more is way too complicated.
If a consumer can go to their builder and ask how much it would be to build their house to Class II or Class I instead of code minimum Class III then I think we'd see a significant uptick in the overall quality of homes being built and in the knowledge that designers, architects, and builders have about building science.
W.,
Current options exist. There is nothing preventing a client from telling a builder, "I want an Energy Star house," or "I want a LEED Platinum house," or "I want a HERS 50 house," or "I want a Passivhaus."
There are plenty of standards out there. The last thing we need is a new tiered system of specifications for energy efficiency.
"Pretty Good House sounds like great ideas but nothing concrete ever came of it"
On the contrary; PGH is a term describing what is becoming a common method to build an affordable house based on Passive House techniques and also referencing Building Science's recommended R values of 5/10/20/40/60 (windows/under slab/basement walls/main walls/roof) which work well in the New England climate. (Although some of us increase the basement values). "Net Zero" is another term that often references the same standards.
Don't dismiss Passive House as being too extreme; rather, recognize that PH brought a better understanding of how houses work to the US. Following PH principles, even without using all of their climate determined R values will give you a radically improved house.
On 'style': If you sincerely want an energy efficient house you can't be too rigid about style, just as if you plan a cross country cycling trip you will hardly be advised to insist on an outfit that looks like a three piece business suit. If you don't like a contemporary look there are some traditional styles that work better for energy performance than others. A good architect or designer should be able to help you find the balance you want, but only if you are willing to bring a little flexibility to the table.
BTW, don't expect to save a lot of money, or get less performance value, by hiring a designer rather than an architect. Good ones cost just as much, and can do as good a job or better.
I think I understand the motivation for the what the class 1,2, and 3 rating system would be. It's probably not obvious to those of us who regularly haunt these forum premises but this is basically an insider group, no prejudice intended, for which the HERS, PH, and USPH prescriptions are useful. You have to already have a fair amount of knowledge to understand the prescriptive use of these standards. What he/she is saying, but maybe far too politely, is that those prescriptive descriptions are for us nerds.
That's right. You shouldn't have to have so much knowledge about construction techniques to still be able to get a high level energy efficiency for your money. There are many people who just don't share the interest in the level of minutia that most here care about, including me. We should make it easier for them, not harder, to get the optimum level of efficiency, design, and affordability that they can afford without forcing them to become nerds like us.
Eric,
There are lots of standards, but you don't have to use them if you don't want to. If you do want to, you can (for instance) ask your builder to build an Energy Star home without become a nerd.
Nerds develop new standards. Non-nerds are happy with the Energy Star label (or whatever local label is commonly promoted).
Martin, I respect your expertise enormously but I think you may have missed my point. The level 1,2,and 3 is all about the idea of a "spectrum" of energy efficiency levels. It would be sort of like the new levels being proposed by Passivehaus, except on a much more basic level. Perhaps the bottom level would be the latest IIRC code level. I think that idea is worth considering. As it is now you have all these different labels with each one trying to supplant the other and most of them having only one certification level. It gives people the impression, depending on the standard they've chosen, that they've reached the ultimate level when perhaps they haven't. Those with deeper pockets could likely do better than Energy Star or Leed. And those with shallower pockets would not have to necessarily accept code minimum if it was easily characterized and monetized in relationship with the next level up.
Eric,
You may well be right that the world needs a new scheme for certifying green buildings or energy-efficient buildings. But I'm doubtful.
If you want a green certification system with three or four tiers, there's LEED for Homes (which offers silver, gold, and platinum) or the National Green Building Standard (which offers silver, gold, and emerald).
If you want to dial in your energy efficiency level precisely, you can choose HERS 0, HERS 30, or HERS 60 -- or any number in between.
You may lament, "But many Americans haven't heard of these systems!" To which I might reply, "Precisely. That's because no one cares." So what makes you think they will care about the new certification system or standard that you are about to develop?
Well, you brought up a good point. It's all about education. The reason builders know about the IRC code is because they are mandated to abide by whatever version of it their locality has adopted. Perhaps rather than have a certification as such the IRC should define these higher levels of efficiency in broad categories such as levels I (bog standard), II, or III, or (OMG) IV. Along with learning about code minimum builders would then be required to learn about what would be involved in building with those advancing levels of energy efficiency and they would be required to pass a test to show competence. Builders could then be offered a certification with evidence of further competence in the different levels along with requirement that with each certification they have to offer pricing for and description of the higher levels to all prospective customers.
Yes, there would much bellyaching and complaining. So what.
Eric,
Traditionally, code inspectors have focused on life-safety issues. For example, major code concerns (historically) have included thermal barriers and the adequacy of exits in commercial buildings.
Ever since energy provisions were added to building codes a couple of decades ago, code inspectors have dragged their heels on enforcing these provisions, for a variety of reasons -- including the fact that our country hasn't invested much money in educating code inspectors on issues that are new to them. As a result of this problem, enforcement of code-mandated energy provisions is woefully inadequate.
You now propose to add a couple of new tiers to existing energy provisions in the code, and to use our existing system of inspectors to enforce it. Your proposal could conceivably be implemented, but it would be expensive, because it would require a serious investment in education. I see no signs that our country is willing to invest in this type of program.