Category Archives: green

air-source mini-split heat pump capacity ratings explained

From the comments here:

“66. I’m going back to post #38 about minisplit capacity and dewpoint. The information in that post contradicted what I understood to be correct, so I checked in with my engineering contact at Mitsubishi. Here’s what he wrote:
“The only relevant factor in determining the available heating capacity is the outdoor wet bulb temperature. This graph below represents guaranteed heating capacities at various wet bulb temperatures.”
This graph shows that the Hyperheat models FE09 and FE18 produce 100% of their nominal capacity down to about 3F wet bulb, and the FE12 down to about 12F wet bulb (I’m eyeballing this graph). In the case of the FE18, I take this to be the capacity they publish at 47F dry bulb, 21,600 BTU/hour, which they show as the maximum capacity in their submittal sheet at 5F dry bulb as well. This graph states that it includes the correction for defrost.
He goes on to say:
“Rated capacity is the capacity as the equipment was tested in a lab setting to obtain the published efficiency values, maximum capacity is the actual capacity that the unit is capable of producing as it operates in the field, you should always use maximum capacity when selecting/sizing equipment for an application.”
So I don’t believe people need to be concerned about dewpoint of the outdoor air when sizing the Mitsubishi Hyperheats. Of course, at temperatures approaching 0F, the wet bulb and the dewpoint get closer together than they do at higher temperatures.”

I would also add my 2 cents to the comments at the article about heating a house solely with minisplits:

Issues which are being compounded:
1 – point source heating
2 – point source cooling
3 – ventilation/fresh air — intake vs exhaust in bedrooms
4 – ventilation — cost of options
5 – heating bedrooms
6 – cooling bedrooms
7 – window sizes effect
8 – low low temp performance
9 – reliability concerns
10 – supplementing w/ wood vs small gas heaters vs electric-resistance heat
11 – the effects of attachment parenting (young kids sleeping in the same room as parents) and/or dogs sleeping in the room

Commments (as someone who lived in such a house in MA for 3 years):

Point source heating works is fine. You can really compare minisplits to a wood stove, because there is almsot 0 temperature differential, which is frustrating because one can’t cozy up to a minisplit, or dry soaking wet clothes after sledding, or keep one room warmer or cooler than others.

Point source cooling is a bigger problem especially if you are co-sleeping and have 4 people in one room because that’s a lot of body heat and if you don’t have a minisplit right in the room it’s less than ideal in the summer even with the door open. 1 or 2 people was fine, even better if one switched the HRV direction I bet! Good idea.

… I like the idea of doing exhaust for ERV/HRV from bedrooms. That would probably be a good idea. Luckily it’s also easy to reroute the supply/exhaust ducts so an easy retro-project.

Even R-5 windows are cool in the winter if you have a small room and you a sitting or sleeping right next to one.

we never had problems with 0F heating even though our minisplits were only rated for 5F.

On the topic of back-up heat, I would probably go for a wood stove and off-grid/hybrid/grid tie solar PVs if I were still in the house. An all-electric house is kinda frustrating when the power goes out and it’s bright and sunny after the storm and your grid-tie PVs can’t do anything. :-) Those little honda generators seem nice but I hate changing oil/maintaining stuff. But honestly, a $50 inverter attached to a car battery ran the fridge just enough to keep things over a 4 day outage. So how much money does one really want to throw at a minimal problem? A cooler in the car would have worked fine too since it was winter, and it’s not bear country.

Parts can take a little while with a minisplit (control boards), but luckily things rarely happen. Our residential mitsu model was difficult to debug I guess (commercial models might have better troubleshooting tools?) so it was one easier to just replace a whole compressor unit.

Was minorly annoyed I couldn’t set back our mitu system below 59F I think it was for when we were occasionally away. Not that lower would have added up to much in $.

OK, other than that… minisplits in a superinsulated house were fine. Silent (as I sit here and listen to my current noisy forced-hot air system). Comfortable. Cheap/almost non-existent bills.

OK that’s it. Just wanted to chime in a little with little pros and cons.

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personal action vs legal action / living by example vs working toward effecting societal change

“The Hidden Life of Garbage is a two year old interview packed with great insights on the politics of waste, including this shocker: When we think about being “green,” reducing waste and so on, we almost always think in terms of stuff that we can do as individuals, and we almost never think about regulating manufacturing. Imagine: instead of making 50 million people feel guilty for using disposable cups at Starbucks, we could just pass a law prohibiting the manufacture of disposable cups. The reason we don’t is that in 1953 Vermont passed a law that banned disposable bottles, and polluting industries formed an organization called Keep America Beautiful, which has been working ever since to block that kind of law, and generally to make us think of waste “as an individual responsibility, and not one connected to the production process.” … the famous anti-litter commercial with the crying Indian…. It turns out that Keep America Beautiful made that ad!”
— Ran Prieur LINK


Going Green but Getting Nowhere
Published: September 7, 2011
Gernot Wagner is an economist at the Environmental Defense Fund and the author of the forthcoming “But Will the Planet Notice?”
(Commenter at amazon: Interesting book and easy to read. Author made one important point; the public will only nominally cooperate with environmental initiatives until doing so is in their best interest as individuals. If we want them to not spew carbon into the air there has to be a cost to doing so. Makes sense to me, but he could have said it in one chapter.)



– China vs US environmentalism: China’s Coal, etc.

– HANS ROSLING’s The magic washing machine

“I believe in the American system, and totally reject the idea that your vote doesn’t matter. You think it doesn’t matter because you haven’t discovered what it means. If you had a little faith in it, if 25 percent more people had more faith, it would work a lot better than you have imagined. Because given enough time, no matter how much they lie, we figure it out. Change will come slowly but it will come. But don’t tell me it can’t change if you haven’t even tried.”

“[Are you trying to do something] that your dead great grandfather, in the grave, can do better than you. You’re using fewer resources? Your great grandfather is using no resources, and if he could talk to you, he might say, “Stop doing stuff that a dead person can do. You’re alive — do something that an alive person can do.”

– Framing: Positive goals vs negative goals

– Shopping local vs the big store

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Filed under erik-green, legal action, local, personal action vs movements, vote

Competition and climate change

“Our programming has led us to where we are. Evolution, survival of the fittest, competitiveness. All this was good for the first 99 percent of human existence. But now we need a new kind of mind, one that does not view the self as all-important. It’s such a foreign idea, so hard to explain in words, precisely because our minds were designed to reject the idea of personal sacrifice. Our goal, which was a good one from an evolution standpoint, was to suck up as much resources as we can, so our offspring will have a better chance when fighting with nature, and competing against the other people’s offspring. This can no longer be the way we do things.”

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Filed under climate change, contrarian, erik-green, green

Heating Degree Days and NSTAR (our gas company)

NSTAR puts a nice 13 month chart of usage on your monthly bill (so one can see usage from the same month in the previous year). That’s nice. But… what would be even cooler is if they showed the HDD and CDD (heating degree days and cooling degree days) for these time periods. That way, when it says you used 100 units this year vs 140 last year, one could quickly tell if that was because it was a lot warmer this year or because of all that insulation you added!

Here’s and API for such data… Only $49/month for unlimited locations! Go to it NSTAR! Actually, surely they already have this data and probably much more because they already surely have to strategize about supply and demand and they probably consult historical data like usage and HDD and weather forecasts.

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What if there was good bicycle parking at McDonalds

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Filed under bikes, erik-green, green, structural

Amazon deforestation contributing to drought

Two recent articles about the drought in Brazil. Worst since 1930 made worse (probably much worse) by deforestation. Go humans.

“The Amazon works as a giant pump, channeling moisture inland via aerial rivers and rainclouds that form over the forest more dramatically than over the sea … It also provides a buffer against extreme weather events, such as tornados and hurricanes.”

“Natural forests act like giant sponges soaking up rain and gradually releasing it into streams,”

From 2009:
“Long-standing assumption: rain forests are a consequence of heavy rainfall. New hypothesis: some forested regions may produce conditions that lead to heavy rainfall. This “biotic pump” model contends that a vast forest such as the Amazon draws in large amounts of water vapor. Evaporation and condensation of the acquired water lead to a local atmospheric pressure drop. That decrease causes rain and attracts more water vapor to the forest, in a continuous positive feedback loop. “This theory could explain why continental interiors with huge rain forests remain so moist,” says Wildlife Conservation Society researcher Douglas Sheil, who in an April Bioscience paper revived the biotic pump model, originally proposed in 2006 by Anastassia Makarieva and Victor Gorshkov, both at the Petersburg Nuclear Physics Institute in Russia. “It could also underline the dangers of widespread deforestation.” Though promising, the model needs more data regarding air circulation patterns and vegetation types to support it, Sheil notes. —Steve Mirsky

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Filed under erik-green, nature / outdoors, trees

AI is problematic

Artificial intelligence (AI) is problematic. I mean, well, it just builds on the basic problem of computers in general. It allows people to do amazing things. So when someone is clever at using them to make money in one way or another, it can make them A LOT of money. Hence huge inequalities in income and wealth (and hence power and freedom).


1) eliminating the need for expensive human workers doing boring work
2) analyzing data in ways that we couldn’t before

and more and more…

3) And AI can/will allow for even fancier ways of doing more of 1 and 2.

THE PROBLEM is that these computers (and the AI) also can do cool stuff for individuals — computers can be used by individuals in many many amazing ways. So it seduces us into thinking we are getting a good deal. But the reality MIGHT be that on balance they (computers) are doing more harm than good when one looks at the overall picture. This is JERRY MANDER’s “limitation of the personal view” which he applies to all technologies. I personally think the jury is out on that. We might swing from one extreme to another, or we may not. I recognize we might look back and realize it’s rather obvious one way or the other.

So anyway, it’s funny that David Brooks is questioning and paints 2 scenarios since his final sentence answers his own question.

This sorta connects to a “PRETTY GOOD HOUSE” article I just read over at Point being that Passive Houses (kinda high tech/complicated to build) can be pretty amazing, but even more amazing is probably building a small and simple house that can get to maybe 90% of a passivhaus (depending on climate) but for a much lower price and complexity — meaning available to be built by more people, more local people, local matericals, etc. etc.

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Filed under computers, erik-green, future, passive house, person: Jerry Mander