The biggest energy saving bang for a buck?
Last Post 08 Jan 2015 05:18 PM by jonr. 22 Replies.
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NewHoosierUser is Offline
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27 Nov 2014 03:31 AM
New code minimum house. If I want to spent 10k on improving energy efficiency what are the things to focus on? Walls, windows, roof?
Windows are a the worst part of a house from a energy pov I think, but raising their R value is very costly compared to wall or roof insulation.

Is there a general answer or are there so many things to consider only a professional calculation can answer my question?
Connersville IN - Lat 39.64 N - Zone 5A (near zone 4)
jonrUser is Offline
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27 Nov 2014 09:46 AM
Focus on getting software such as BEopt that will analyze this issue and give you the right answers. If not, then hire someone to do this.

A blower door test and thermal imaging during construction (while you can still remedy it) should have a good ROI.
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27 Nov 2014 10:56 AM
Is there a general answer o
Quality construction is the answer. No amount of planning and engineering will do any good if the actual execution is shoddy. The good news is that getting a conscientious contractor shouldn't cost more, it's just difficult.
LbearUser is Offline
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27 Nov 2014 04:52 PM
#1 - Air sealing - Making the house air tight is the first course of action. Unfortunately if the house is already built this can be very difficult due to the wall & roof cavity access.
#2 - Roof - Just like your head, the greatest amount of heat/energy loss is through the top of the home or the roof area. Heat rises and if you roof is leaky and/or has a low R-Value, you are basically creating a chimney effect.
#3 - Walls & Windows - This again appeals more for a NEW home build rather than a retrofit. Pay a little more $$ when building to get better walls and windows is worth it in the long run.


For $10k the best application of that money would be in air sealing (where you can) and then converting to LED lighting and having your HVAC systems inspected since they are your biggest energy hogs. Maybe a small PV solar system but for < $10k you will not get much even after rebates. 
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27 Nov 2014 06:14 PM
I think I wasn't clear enough. The house isn't built yet. So I want to take code minimum specs and spend 10k on improving things. 10k can just as well be 20k if I'm convinced it helps.
Anything can be messed up but what I have in mind is a airtight house from start. (ICF)
I think airtight is one of the cheapest and most effective ways to save energy. Even if I could afford 20k monthly heating bills I would make my house airtight and well insulated because it's more comfortable.

A PV system is on my list but isn't part of the 10k.

My question is mainly about finding a balance. Roof insulation is certainly a good thing Lbear. But an R100 roof with R15 walls likely isn't money well spend.
Connersville IN - Lat 39.64 N - Zone 5A (near zone 4)
LbearUser is Offline
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27 Nov 2014 07:48 PM
What climate zone are you building in?
Ranch or 2-story?
How many square feet?

If you are doing ICF walls, I would recommend a SIPs roof.
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27 Nov 2014 11:59 PM
https://energycode.pnl.gov/EnergyCodeReqs/?state=Indiana

Zone 5. Connersville IN, which is 70m east of indianapolis. So quite near zone 4.

1 story.

Rural.

ft2 depends on how much I can get the energy cost down. Realistically speaking I only need 1000 but want a bit more. That's just the house btw. no indoor garage etc. But I'm not against an attached garage (without connecting door).



Code minimum R13 wall, R30 floor, R38 roof.

If I put the max. amount of pv on my roof (16kW) Worst month (December) 815 kWh

http://pvwatts.nrel.gov/pvwatts.php



Regarding the SIP floor, I haven't set my mind on a floor tpe yet. I did a quick search and they look nice. All but one meet code minimum. the 12" panel nearly doubles it. Generally speaking I like the idea of a one step solution instead of low R ceiling and add extra insulation. Are they strong/handy to hand things on? Like a ceiling ventilator

For the same reason I wrote I want a ICF house. I want brick or concrete. But I'm not 100% sure it will be ICF because I simply don't know all the options. I for example also like cavity walls too. From an insulation pov the SIPs look great but they don't look as strong as concrete. Concrete is also airtight but SIP panels require sealing around the edges I think.


http://www.thermapan.com/products/floor.html



Connersville IN - Lat 39.64 N - Zone 5A (near zone 4)
Eric AndersonUser is Offline
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29 Nov 2014 08:55 AM
The big picture is that the house has to work well as a complete system, not just as a collection of unrelated things. You really need systems thinking to make it work well. In the abstract, it is hard to give advice as to what are the most useful upgrades.
The basic rules for energy efficiency are simple; build a small, efficient shape, airtight <1.5 ach50, use balanced mechanical ventilation, add as much insulation as you can stand, and finally, use right sized sealed combustion appliances.

Beyond that, you should build it with a roof line that faces solar south, preferably with an unobstructed view of the sun from 9-3 pm in the winter and longer in the summer. Try not to put chimneys or roof vents in this section for the roof. The cheapest solar is passive solar, if it is designed correctly.
As far as figuring out what is the most effective thing to upgrade, there are 5 factors I look at-
1. The cost of the upgrade.
2. The heat loss reduction by that upgrade.
3. How difficult it is to upgrade it later and how long it is effective for.
4. What other benefits are derived from the upgrade. IE comfort, maintenance, health, safety, durability
5. How would this upgrade effect other parts of the house

All these things generally require a reasonable energy model. I use Rem-design, which has limitations, but is good enough for my purposes. I would note that you should be interested in year round performance, not just maximum heat loss. For the record, a good excel spreadsheet and a bit of thought would be good enough for optimization purposes. I wish there were simple answers for this bet there are not. It takes a good bit of thought to get it really correct.
Up to a point, reduction in shell losses can result in smaller and simpler mechanical equipment required.

Take a window for example. A window provides light, a sense of openness, ventilation, solar gain. It affects the occupants by raising or lowering the mean radiant temperature. You want to factor in the size, r or u value of the window, solar gain of the window- (which depends on the orientation, distance to and size of the overhang, tree shading), air leakage of the window, condensation potential, egress requirements.
 
A window also affects the location of heat emitters needed, depending on the u value of the window. Deciding on a window depends on many things for instance, casement windows have twice the ventilation potential of a single hung window. This is much more important if you don’t have AC.



Think Energy CT, LLC Comprehensive Home Performance Energy Auditing
FarmboyUser is Offline
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30 Nov 2014 06:58 PM
Recommend considering casement windows for increase ventilation as Eric mentioned and reduced air infiltration over single or double hung windows. For our ICF home now under construction , we're planning a limited number of operable casements to meet egress and ventilation needs and the rest will be fixed. I vote for reducing air infiltration. One example is caulk under the sill seal between the top of wall and the 2x plate. Not only did it ensure no drafts between the plate and the concrete, it held the plastic in place while we muscled the wood into position. Might be a bit overkill, but that's the level of effort you'll need to consider to maximize your results. And caulk the joints between the plates.
jonrUser is Offline
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30 Nov 2014 10:09 PM
Wherever possible, I suggest using EPDM gaskets and/or a good tape instead of caulk.
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01 Dec 2014 12:43 AM
Design your home with all of the HVAC equipment and duct work (assuming it has duct work) located within the conditioned space.

Energy heel roof trusses are another energy saver that is relatively low cost.

Consider installation of a heat pump water heater (hybrid water heater). It will also cool and de-humidify the room where it is located. Even if you only operated it in heat pump mode during the warmer months of the year, there is still significant energy savings to be had. Some models also have duct kits for the cool exhaust that can be directed outside in cold weather.
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01 Dec 2014 03:38 PM
What jonr said.

The BeOpt software was specifically designed for answering this type of question, a financial overlay using DOE2 as it's fundamental energy use simulator (not perfect, but just fine for figuring this stuff out.)  The software itself is a free download (courtesy of the US taxpayers), but like any other tool, garbage-in=garbage out.

There is a bit of data-entry, and you have to estimate the installed cost of whatever you do, but once the data is entered it allows you to play "what if?" games, to see if increasing the R-value of the wall is going to have a better return than lowering the U-factor of the windows, etc.

Cleaning up and simplifying the design is the cheapest/easiest energy improvement. Reducing the number of corners on the exterior walls reduces thermal bridging while also lowering the exterior surface area to floor-area ratio. Reducing the amount of window area reduces peak heating & cooling loads, but depending on the U-factors & solar heat gain coefficients and the total thermal mass of the house sometimes increasing the window area on the south-facing side of the house can reduce the total energy use, etc.

No matter what the other aspects of the house may be, the cheapest energy performance improvement you can buy is air-sealing the house to the point that it is under 2 air exchanges per hour @ 50 pascals pressure (2ACH/50).  The IRC 2012 code max is 3ACH/50- not sure which revision of the code is currently active where this house is being built.  IRC 2009 had fairly loose air-tightness requirements, and before that there were none at all.  Hitting 3ACH/50 takes very little effort if it was designed & built with air-tightness in mind, 2ACH is a bit tougher, but still not difficult.  To hit the PassivHaus 0.6ACH/50 takes quite a bit of attention to detail.
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17 Dec 2014 02:56 PM
Are there any turn-key green designs out there? I have effectively the same question as the original poster, though it will be many years before I can realize building my dream home. So in the meantime, I try to read as much as I can to be better informed when the time comes.

As to my original question, I know "green" is of course vague, but what I'm getting at is this: I would expect that there ought to be existing, proven designs out there (i.e. "turn key") where, rather than making theoretical cost predictions based on some software model, you can actually assign real numbers. The historical performance and operating costs would of course have to be indexed to the region (for weather and electric/gas supply cost data), but that's easy.

At least in my personal case, all I really want is a (1) floorplan that works for my family, and (2) "green" features that demonstrably pay for themselves in say 10 to 15 years. Obviously there are countless pre-existing/turn-key designs out there, and no doubt many have agreeable floorplans. But I don't see a lot that have been designed with that second requirement in mind. That, or I'm not looking hard enough.

From my naive perspective, this seems like something the modular home companies could maybe execute really well.
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17 Dec 2014 05:14 PM
WannaBuildGreen:

The "...demonstrably pay for themselves in say 10 to 15 years..." part would not be prone to generic solutions, since financial payback depends a lot on your energy source costs, and how you use the house, how you heat & cool the house compared to how you MIGHT have done it with a code-min house etc. as well as the projected future energy costs (which are all over the place.)

IRC 2012 code minimums will usually (but not always) pay off over some lesser-insulated building in direct energy cost reductions within 10-15 years, but it could be as little as 6 years or as long as 25 years, depending on fuel costs, and what your presumed comparison-building was.

Rather than "easy", projecting the cost of energy over the next 10-15 years is actually quite difficult (some say impossible). Fifteen years ago propane was under a buck a gallon and heating oil was under two bucks. Ten years ago electricity in my neighborhood was about 12 cents/kwh, this week it's 25 cents/kwh. If you think you actually know what energy costs are going to be in 10 years, consider that a bit delusional. At the beginning of the summer some market analysts were predicting $100/bbl crude oil ramping up to $150/bbl by 2030 (and it still might, with some volatility along the way), but nobody was predicting $55/bbl (today's price) even as recently as September, yet some are boldly stating that it'll be in this range for months or years (based on their own dream-state vision, I suppose.) Did the natural gas glut catch you by surprise too? Will you be suprised if that glut dries up when oil-drilling in shale formations drops off due to the low price rendering it unprofitable? Energy markets are nuts, and can't be reliably predicted over the time spans you need for tweaks that "demonstrably pay for themselves in say 10 to 15 years".

Then there is the issue of the cost of money, and whether a bigger mortgage (the interest portion of which is subsidized in the tax code) can be more than offset by reduced energy costs (which are not subsidized by the tax code), and it makes a difference which tax bracket you're in. The financial modeling can be almost as complex as the thermal modeling of a simple home.

Rather than simply throwing up your hands and building a code-min house (== the lowest performing house that is legal to build), a useful starting place for design discussion, broken out by US climate zone can be found in Table 2, p10 of this document:

http://www.buildingscience.com/docu...mate-zones

Note, those are "whole assembly" R values, which take into account the thermal bridging of structural elements that cross through the insulation, such as stud framing, etc. For instance, for US climate zone 4 they recommend an R20 wall as the starting point. That isn't a 2x6 stick-built wall with R21 batts- the thermal bridging of the framing reduces that to only about R14 (R15 if using 24" o.c. studs and single top-plates to reduce the total framing fraction). But adding 1-1.5" of continuous rigid foam over the sheathing would get you there.

Also note, how you get to those whole assembly numbers can have widely varying cost structures. An R60 attic is really pretty cheap if you use blown cellulose at 3-4 cents per R per square foot, substantially more if you are using closed cell spray polyurethane at 17-18 cents/R-foot, which will have very different "payback" compared to a code min low-density batts between joists type of solution.

At the very least, making the house air tight, and insulated to IRC 2012 code-minimums isn't going to be a terrible energy hog and IS worth doing even if it happens that your state is still operating at IRC 2006 levels for insulation minimums, though in most cases there is a financial case for at least a LITTLE more, where it can be done cheaply.

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm

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17 Dec 2014 05:16 PM
What would be a green house in one climate might not be in another region. And locally available materials are part of the equation as well. Hauling materials thousands of miles somewhat negates the 'green' moniker. In other words, if you really want to be green, you have to design and build for your location. Obviously, there are some basics, such as keeping the house as small as possible, with a simple shape and quality construction. My house, in a fairly warm and sunny climate, has large roof overhangs, which would be a negative in a cold climate, where you are trying to glean every bit of solar gain.

The overall design of the house, such as the appearance and floor plan don't have that much impact on energy savings, unless it is an extreme shape with a lot of wall area, or walls of windows letting in excess heat or cold. A rectangle is good; a square is better, and a round house has the least wall area of all. Not very practical, though. Soaring ceilings are a waste, and how the house is sited on the land can be a major factor.

Really, you have to take all of the advances and recommendations you can find, and adjust them for your needs, and the requirements of your climate and individual lot. That is what a good architect can do for you. Built to known standards, the software should give you pretty good numbers. I would think any turn-key design would fall short somewhere.
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17 Dec 2014 06:33 PM
Wow, thanks for the incredibly detailed and informative replies!

For what it's worth, what prompted my question was this: I read a lot of high-level information about green home building, but it's (1) "academic" in nature (i.e. I have no practical experience), and it's (2) easily-accessible Internet information that I read when I have a few spare minutes here an there, i.e. probably not always the highest-quality information.* In my ideal world, I'd like to be able to lay out all the detailed specs of this future house I want to build, but in reality, I don't feel like I have the knowledge to do it. And with kids and full-time work, I don't think I'll ever have the time to dedicate shoring up my knowledge enough to be confident in a semi-DIY approach. In other words, I'd have to at least somewhat resign myself to hiring a professional architect or green building consultant. But that conflicts with my desire to save money. Hence, the desire for an "off the shelf" solution.

*Please don't take that comment as a slight! I'm not calling out this site or posters in particular, just making a general statement about using only the Internet for any kind of "serious" research (particularly in conjunction with unfocused sporadic free time). After typing that out, I realize it's simply one of those complex situations where you either put in the time to do acquire the knowledge, or pay for someone else's expertise.

Anyway, getting back to the original topic: is it right to say you could have the best design in the world, but a lousy implementation will negate many of the would-be benefits? And likewise, an average design could perform better-than-expected with top-notch construction techniques?

If so, it seems like the "biggest energy saving bang for a buck" would be to ensure the people actually executing the design are aware of the "green" goals, and have the experience, knowledge and attention-to-detail to actually make it happen, right? And maybe that's not even "bang for buck" so much as a fundamental requirement for maximizing the energy-saving potential of the house?
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18 Dec 2014 06:33 AM
I spent about 5 years doing research on house design and construction before I started building. If there's one thing I've learned, it's that many so-called professionals are hacks. I've read of really grievous mistakes made on high-end homes. One was even built on the wrong lot! My point is that if you want a well-built home for a reasonable cost, you'll want to learn as much as you can on the topic. A house is a huge investment to hand over to a virtual stranger.

I've done about 90% of the work on my ICF house myself, and had a hand in 100% of it. I even designed my own HVAC, although many people told me that I would have to hire a professional. I had one such 'professional' tell me what size HVAC I needed over the PHONE! His guesstimate was 300% of the size I needed, which would have wound up being an expensive, inefficient, and poor performing system.

You're right about a great design being screwed up by poor execution, and an average design being made very efficient by careful execution. Take the time to learn about general design, siting, appropriate construction methods for your climate, windows, insulation, HVAC, etc., etc. That way, you'll know (hopefully) whether your future house is being designed and built properly. I'm not sure if my house will pay off in my lifetime, even with the money saved by DIY, but there are other factors above and beyond simple ROI.
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23 Dec 2014 11:32 AM
WannaBuildGreen, where are you building?
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25 Dec 2014 09:48 AM
Posted By patonbike on 23 Dec 2014 11:32 AM
WannaBuildGreen, where are you building?

Only in my head right now, but eventually in central Illinois (in or around Peoria).  From the little research I've done, it looks like the climate there is effectively the same as the Chicago metro area (which I mention because it's such a large and heavily populated area, I figure there's a better chance of people being familiar with it versus "downstate").

But anyway: this is far enough in the future, that I couldn't even give a specific date, just the vague time frame of maybe three years from now at the absolute earliest, up to seven or eight years away.  But when I do build, the idea is to build my dream house.  So it's naturally a topic of interest to me, and fun to think and learn about.


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04 Jan 2015 04:27 PM
Not clear if you have a basement or not. If you do, insulate the floor and install a heavy vapor barrier under the concrete, and install poles foam on the concrete walls. A warm dry basement is the first step to a more comfortable house.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
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