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Old 05-05-15, 08:34 AM   #11
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Gasstingy,

Yes, you can put in too much insulation. I have seen it done. I recommend about R40-R60 for the ceiling, in all but the most extreme lower 48. Walls max out at about R20-R30. One client insisted on doing R70 walls and R120 ceiling. I tried to explain that the return on this tripling made the pay off time literally about 200 -300 years. He would not buy it and spent far too much $ on this.

The performance data discouraged him. He though by putting in these large values, he could heat his home "with a lightbulb" - this was before CFLs or LEDS.

As an engineer, the major issue is "bang for the buck" with adequacy of design. With insulation, the return is not linear, but a 1/x relationship. So, for an attic, the return on the first inch is about one week, for the next four inches is 6 months, the next four inches about a few years and so on. Much beyond R-60 and you are just insulating with dollar bills.

If you look a U values, the inverse of R, then it is a linear relationship. In Europe, the U value is more widely used.

But basically it is just Ohm's law E=i/R or E=iU.

Steve

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Old 05-05-15, 09:03 AM   #12
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Originally Posted by gasstingy View Post
Some folks just don't get it. It's like trying to sell the idea of adding solar power to someone. They ask, what's the payback time? I say, "About ten years or less." They nix the idea because it "takes to long" to pay back.
If you DIY solar you can get payback 4-5 years. if your power company offers a rebate sometimes you can install it almost free after tax breaks.

my power company is going to offer rebates to install solar for the first time this year. They usually put stuff in their rebates like you have to use one of their listed installers or you don't get the rebate.

The give a rebate for installing efficient HVAC but they exclude Mini Splits but they still require you use their vendors and exclude DIY installs.


The last couple years I have increased my elect usage by a lot. Added EV car Added mini splits to heat with and added solar to cover it all.

people ask me about my solar all the time and I tell them it is cheaper to conserve then to install solar to cover what you are using now. Start down the conserving path now then determine how much solar you need.

They don't want to stat to conserve and most of them are never going to conserve or install solar they just like the idea of it.
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Old 05-05-15, 09:33 AM   #13
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I always recommend making efficiency / conserving first. It is exactly how we did our house. Followed by solar. Followed by changing from gas heat to a high SEER / HSPF central unit. {Still have natural gas water heater.} We use more electricity than ever now, but make much more than we use over the course of a year.

Now I am just biding my time until I can get into an EV.
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Old 05-05-15, 09:45 AM   #14
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I always recommend making efficiency / conserving first. It is exactly how we did our house. Followed by solar. Followed by changing from gas heat to a high SEER / HSPF central unit. {Still have natural gas water heater.} We use more electricity than ever now, but make much more than we use over the course of a year.

Now I am just biding my time until I can get into an EV.
Tell us about your solar array is it posted here?
if not pots it here
Solar Power - EcoRenovator


I don't want to side track AC post.

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Old 05-05-15, 10:29 AM   #15
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I think most of us agree that infiltration is the first thing to work on, then insulation (up to a point) and then lastly, installation of commercial "high efficiency" solutions.

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Old 05-05-15, 10:37 AM   #16
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This seems common knowledge here but people on the street don’t think this way.

Post your results for your savings over the years.

I guess the point is we seem more intune with conservation.

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Old 05-06-15, 11:54 AM   #17
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Spending a few grand on going from R20ish to R40ish seems worth it to me in Minnesota. It also allows for other options for heating versus natural gas. In my case with R40 or close to it, my heat load goes from about 17000btu/hr at design load to about half that with a well sealed 2100 sq ft house. I'm looking to add about 128sq ft of solar thermal and cutting the natural gas($144 in connection fees yearly and the MN PUC has a rate case for increasing the basic service charge) and using one of the super efficient mini-split heat pumps in its place will also let me lose ductwork losses and put the heat where I want it versus the whole house.

Insulation in my case is going to allow me to avoid spending $6000-8000 on replacing my existing 8.5 SEER AC and 30 year old natural draft natural gas furnace and instead spend it on one to three mini-split heat pumps that I can install myself much easier than installing a central system(gas furnaces are illegal to DIY where I live and I'd get no warranty coverage if I did and a mini-split is easier than a central AC too).

So in my case, blanketing the house in an additional 4" of XPS before replacing the siding and windows(both need to be replaced so it is a sunk cost anyway) makes sense.

If I was building a new place, I'd aim for R40 or so cellulose done with a double stud design with advanced framing with 24" on center in Minnesota. If I lived in a more comfortable place that doesn't need high latent reduction and high heat loads, comfy places such as Seattle or Portland, I'd probably be cool with 2x4 6" framing with R21 fiberglass or a cellulose fill with inverter mini-split heat pumps. Either way, I'd be looking for a well sealed enclosure ACH ideally under 2, especially so I can fight less latent gains in the summer.
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Old 05-06-15, 12:45 PM   #18
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I was hoping that this thread would encourage other EcoRenovators to post the real results of their own efforts... which was good and useful when it happened in the beginning. I was also hoping that the results would encourage others to see that the time, money and effort to upgrade was worth the considerable effort.

However, I'm now pained to see this thread devolve into a pontification of opinion regarding the undesirability of 'too much insulation'.

I really wish that this gumption-diluting turn of the thread had not happened, and I am puzzled and concerned why it has.

SH... I myself, have been a mechanical engineer for 43 years, during which time my career also included a 20 year stint as a college instructor of engineering: mathematics, thermodynamics, physics, manufacturing processes, etc.

It pains me to see your use of the phrase, "As an engineer...", and then to see the dubious advice that follows those words...

I know that it is regular, expected practice for engineers to substantiate their claims with clear mathematical proof. It would be a proper thing for you, if you are going to claim to be an engineer, to substantiate your assertions 'as an engineer' with clear mathematical proof, and not your local folklore.

(* I think that EcoRenovators need to be aware that oil-rich Oklahoma, the state where you live, has the lowest energy costs of any state in the USA, and also discourages solar energy and wind energy, and may be the reason that your folk-loric energy advice is so tepid. *)

I say all this because years ago, I made the mistake of accepting 'common wisdom' (folklore) and insulated my house with a 'reasonable amount' of insulation... I seem to recall that the same phrase "insulating with dollars" was used then, too. In the following decades, I did waste a very large amount of money through heat loss, because of the very large rise in fuel costs (which, in the long term will continue to rise). Now I am ripping out the 'reasonable amount' of insulation and putting in the most effective insulation I can possibly afford. My energy bills are beginning to speak to the success I am having.

SH, I would like you to please put me in touch with 'your client' who didn't listen to your advice. I would like to speak by phone or email to him (or her) myself to see just how much he regrets having wasted so much money on insulation. I'd like to see how much he regrets not joining his fellow Americans in shouldering the burden of foolish energy use.

It would be nice if you had an international perspective, if you were as progressive as Scandinavia in their energy conservation in their housing designs. It would be useful if you were as thorough as the Germans and actually understood at least the principles of Passive House design and planning, and realized the interplay between all the elements of heat conservation design.

It would be nice if you applied your engineering talent (if it exists) to initiating projects that typical EcoRenovators might benefit from, complete with photos and diagrams and actionable details. Your SIP barn is a start. I'm sure that it will be useful to others who also want to build a barn.

SH, will you please get back on track and show us the numerical details of how your efforts to conserve have reduced your energy use? If that has actually happened.

That is the purpose of this thread...

-AC
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Old 05-06-15, 12:57 PM   #19
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Quote:
Originally Posted by MN Renovator View Post
...If I lived in a more comfortable place that doesn't need high latent reduction and high heat loads, comfy places such as Seattle or Portland, I'd probably be cool with 2x4 6" framing with R21 fiberglass or a cellulose fill with inverter mini-split heat pumps. Either way, I'd be looking for a well sealed enclosure ACH ideally under 2, especially so I can fight less latent gains in the summer.
You might be interested to know that here in 'comfy Portland', 6" framing with R21 fiberglass or a cellulose fill, is pretty much the minimum code to get a building permit. (You also used the term "2x4 ". I'm not sure if you made an error, or if you meant to imply staggered framing.)

The progressive social atmosphere and forward-looking energy department strongly encourage and incentivize people to go much farther.

People here are very keen on being green. It not only saves money, but earns respect.

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Old 05-06-15, 01:51 PM   #20
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I meant to say 2x6 framing, that was an error. My headspace was thinking double-stud 2x4 wall framing. For what it's worth, I support the revised building codes that as soon as they are adopted in full requiring R25 with 2x6 construction with the IECC 2015, although some of that code is still draft such as windows requiring a u-value of 0.20 in climate zones 4 or colder which includes Portland. I think these are steps in the right direction, although code minimums as you said are minimums. I hope what I said wasn't included as 'too much insulation' talk and I'm also hoping I wasn't going off topic. How about I revise what I said for Portland to IECC 2015 standards or better. Even with that I think that window space should be minimized to reduce summer solar heat gain and allow for more insulation space or at least build attractive shutters or other solar reducing into the design(properly designed overhangs or solar screens) to not overheat in the summer.

More info here.
https://www.energycodes.gov/resident...sals-2015-iecc

I might be wrong but I thought I was fairly familiar with Portland's climate, I think our summers are roughly the same level of heat(mid-80 degree days for a month or so with some days touching 90s with dew points reaching the 80s.) with our winters being colder. I suppose this all changes with the quantity of sun and other factors. I think that it wouln't be too hard to go the supplementary solar space heating route whether air or water with 0.2 u-value windows and R25 or better insulation and still be fairly comfortable there, granted most people probably wouldn't bother but in my opinion it's cheap if done DIY and reduces the need to use outside energy for heating. Our once yearly night -20f temperatures and about a weeks worth of -10f nights that we get on a yearly basis makes my solar heating system inadequate for those coldest nights but I expect it to give a 30f average boost in temperatures on sunny days prior to adding insulation.

Unfortunately what's slowing me down is not being able to find 0.20 u-value windows with a 'special order' up-charge because the quantity they are produced at the moment is small. Once the IECC code takes effect I can get them cheaper and will follow through with my insulation and window plans but staying with the current windows and adding the insulation makes me move the windows out 4" and I'd rather put new improved windows in versus just moving them out because there really is no added effort to replacing the windows at the same time and it would allow me to use new construction windows instead of retrofit which could come at a better price and with a new building code would probably be easier to find. ...although if time and money finds me sooner, I'm looking at Zola windows, a builder in Wisconsin are used them for their 'almost passive house' when they presented at the MREA Energy Fair in Custer, WI last year.

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