Category: Environment

Post #2083: Cold wave, heat pump, wood stove secondary heating.

 

Sometimes, all you need is a warm place.

Cold wave:  It’s going to get cold next week.

How cold?

In Vienna, VA, the National Weather Service is predicting a nighttime low of 4F, a week from now.

That’s rare but not totally unexpected.   

As of 1990, Vienna was at the edge of USDA plant hardiness Zone 6B, and could expected to see (and did see) occasional wintertime lows down to minus 5F

Three decades later, and we’re ten degrees warmer.  (In terms of our expected extreme low winter temperature).  As of the most recent USDA Hardiness Zone map, Vienna has moved into Zone 7B, with an expected extreme low of 5F.

That trend came through clearly in my analysis of annual low temperatures at nearby Dulles Airport.

So, it’s going to be cold, but it’s in line with expectations.

Heat Pump:  Cold weather remains the soft underbelly of air source heat pumps.

 

I fully grasp the irony of heating my house with an electrical appliance that, by design, quits working when it gets really cold outside.

Near as I can tell, all air source heat pumps all do this.  It’s just a question of how low can they go.  What I think of a “standard” home unit, as I recall, shuts down around freezing (32F).  Conversely, the “high heat” versions of heat pump I got will go down to -17F or some such.   This — super cold weather — is where ground-source heat pumps shine, as the ground loop temperature may be quite cold by that time, but nowhere near as cold as it is outside in a cold snap.   So the ground source is starting from much “warmer” material to extract its heat from.  Which, as you might well imagine, is an enviable position for a heat pump to be in.

But.

But 1, I didn’t think I’d hit that lower temperature limit the first winter I owned the thing.  The lower limit for mine is, in fact, 5F.  So, I will be looking at some (brief?) period when this new air-source mini-split may not run.  Not because it’s broken.  Just because it’s cold outside.

But 2, now I have to suss out the secondary heat.  Every heat pump system has secondary heat, I think.  (Or maybe it’s “should have”).  That’s what you use when the heat pump isn’t enough.  (Or to speed up the heating of rooms, when the heat pump alone would raise temperatures too slowly.)

Secondary heat for this mini-split is strictly DIY.  That’s by design.  It doesn’t come with — nor is is capable of activating — secondary heat of any sort, as far as I can tell.

So, just burn some natural gas …

White Clouds in Blue Sky ca. 1996

Secondary heat isn’t really a problem, because I can burn natural gas for heat.

But.

But 1, I can only do that — use the baseboard heating in that part of my house — by jury-rigging what’s left of my (still kind-of functioning) baseboard hot water heating.

But 2:  My fancy gas water-heater/furnace objects to serving as mere house heater.  (Another long story.)  It’ll work, but it’s bad for the device (as in, this is what burnt out the internal pump motor the first time.)

So I’m going with something simpler.

Buying a small quantify of firewood in the dead of winter.

 

I am now that guy.  That guy who is … per the title.

I wanted more than a shrink-wrapped bundle. But far less than a cord.  Where can I buy that, around here?  Preferably to pick up.

The right place for that turned out to be the Reston Farm Garden Market.  Where I paid $85 for an eight-of-a-cord, kiln-dried, stacked (by them) into the back of my hatchback Bolt.

So, $680 a cord, for kiln-dried hardwood, bought in small (one-eighth-cord) quantity.  I thought that was OK, in an area where a cord of kiln-dried hardwood, delivered, from my nearest source, would run $550 plus delivery fee.

Kiln dried or merely seasoned?  We go for kiln-dried now. It guarantees that it’s good firewood, but it’s a little too good. For sure, it burns more readily.  There are no bad logs.  But it burn faster and hotter than it ought, which means messing with the draft and relying on the air-tightness of the stove door gasket.  (FWIW, I’m convinced that the hotter burn nearly makes up for the fossil fuels used to dry the wood.  So the kiln drying step is not quite as much of an energy loser as it might seem at first.  And with all the pests harbored by firewood, it has to be kiln-dried to be moved more than a county or two away, anyway.)

FYI, the various shrink-wrapped or netted bundles of firewood for sale at local retail stores seem to work out to around $1600 a cord.

Apparently, this little out-of-the-way farm store moves tractor-trailer-loads of firewood, per year, through their yard.

That said, local air pollution aside, firewood is an expensive way to heat my house, given prices in my area.

As I recall, this is about what I found the last time I figured it.  Recognizing that for me, electricity is cheaper than natural gas, this means that firewood is my most expensive fuel option.

Short of this:

With the understanding that I’ve already shown that electricity remains my least expensive fuel, almost regardless of the outside temperature.*

* As long as the heat pumps will run.

Conclusion

My wife and I agree that there is just something comforting about having a full rack of dry firewood.

It’s not rational, practical, economical, or conducive to the public health.

But it is comforting.

And firewood is going to provide our secondary heat through this cold snap.  For the occasional night or two when we hit the extreme winter lows for this climate zone, it seems like the easiest solution.

Post #2082: One-in-1000 Californians just lost a home?

 

I started off trying to get the LA fires into perspective.

I just want a back-of-the-envelope number

 

I hate to sound blase, but, OK, parts of LA have burnt.

Not wholly unexpected.  Surely more likely to happen as climate change progresses.

But, it’s, you know, California.  Stuff happens in California.  Earthquakes.  Mudslides.  Wildfires.  Excess rain and snow events.  Droughts.

I’m from the Mid-Atlantic region, where the worst we typically face is 17-year locusts and the occasional dry spell.

And this is in no sense a slam on California.  California is about as good at dealing with stuff like that as can be.

I just want to know something along the lines of “how does the value of the damage from the current LA fires compare to other disasters?”

I’ll settle for a count of homes lost to fire

Source:  fire.ca.gov.  Cal Fire?

As of 1/16/2025, the overwhelmingly quoted number in news coverage is 12,000.  That appears to be from 12,300+ “structures destroyed”, from Cal Fire.  As I understand it, that’s a number from the government of the State of California.

At the same time, a couple of big local banks (Wells Fargo and Goldman Sachs, cited by ABC News) have already projected $30B in insured losses.

If that projected $30B cost is close, these LA fires will be by far the most expensive fire event in California history, more than twice as expensive as the (now) second-most-costly fire in California history, the 2018 Camp Fire.

Source:  Cal Fire statistics page, this is their top 20 list.

By the numbers, it’s clear that a high cost per structure contributes to the overall higher cost of the LA fires, compared to the Camp fire.  To know that the loss estimate for the 2018 Camp Fire was $12B (reference).  That the works out to a $600K cost per structure for the 2018 Camp Fire — the costliest California fire until now — versus about $2.4M per destroyed structure for the LA fires.   I’m not sure I fully understand why the difference would be that large, but that’s what the simple arithmetic says.  Bear in mind that the $30B estimate is just a preliminary estimate by a couple of big banks.

 

13.4 million households in California

So says the U.S. Bureau of the Census (reference).

If the Los Angeles area just lost 12,300 plus structures, and if all of that was housing, and assuming (the equivalent of) predominantly single-family homes, then, roughly speaking, (12,300/13,400,000 =~) 0.1% of California households just lost their place to live.

If I had to take it further, it looks like Californians on average pay about 0.4% of the value of housing as insurance premiums each year.  Inverting that, this one event — a total loss of 0.1% of California housing — would seem to amount to about a quarter-of-a-year’s property insurance premiums for the entire state of California.  But because those LA properties appear to be so expensive per dwelling, it’s entire possible that this one even could cost … about a year’s worth of property insurance premiums for all of California.

Conclusion

A plausible scale of insured costs of U.S. natural disasters puts 2005 Hurricane Katrina at #1 with more than $100B (reference).  That’s in current (2025) dollars, roughly speaking.

The $30B projected insured losses for the LA fires would put them 10th on that list, just past the 1994 Northridge earthquake, the one that shook down a section of freeway.

It’s California.  I’m sure they’ll deal with it about as well as it can be dealt with.

Post #2079: So, when will Greenland be ready?

 

To use, I mean.  For us to use.

Now that it’s on order.  Once we buy it, or take it, or whatever.

How long before we get to use it?

I appreciate the sentiment.

Republican policy, if I can infer such, is not merely to ignore global warming, but to encourage the consumption of fossil fuels.

And yet, even as they deny it, they seem to realize they’ve got to have a place to put people.  You know, once Florida is under water, the Great Plains have reverted to sagebrush desert, and so on.

But, we’ve got this big empty island, just offshore.  Kinda.

Buy the big empty island, set up resort destination with a few casinos, and problem solved.

It’s a no-brainer.

Plus, if we’re tired of NATO, there’s no better way to do away with it than to attack a NATO country.

It’s a no-brainer and a two-fer.

But I digress.

How long for the ice to melt?

At present, Greenland is 80% covered by a remnant of the North American ice sheet.  It’s a relic from the most recent ice age.  I vaguely recollect that the ice is two miles thick in places.

But on average, it’s under a mile-and-a-half thick.

 

Based on all sources available to it, Google’s AI thinks it’ll take at least 1000 years for the ice to melt.

If I specifically narrow it to the IPCC, Google tells me “a few thousand years”.

Admittedly, some real estate will open up before the ice melts fully.

But given the overall time line for global warming, and certainly the likely remaining lifespan of the USA, I don’t think the ice up there is going to melt in time to do us much good.

 

Post #2077: I opened the hood of my car.

 

Finally.  I finally opened the hood of my 2020 Chevy Bolt, a year after I bought it (Post #1924).

I never saw a reason to look under the hood, figuring I’d have no idea what I was looking at.  It being an EV, and all.

Now that I’ve opened the hood, I was not disappointed.

Not ringing a lot of bells with me.  I think I recognize a brake master cylinder and tan plastic reservoir mounted to the firewall, driver’s side.  But all those big metal thingies?  No clue.

Luckily, one can be ignorant and still drive a car.  That, proven daily, I’d say.

Even now, I wouldn’t have bothered to open the hood, ever, except that with the recent winter storm, and the resulting sloppy roads, I figured I should top off windshield wiper fluid.  Seeing as how that hadn’t been done in a year.

I was able to do that without reading the manual.  The hood release was in an obvious place, the hood emergency latch was easy to find, and (shown below) the right place for windshield wiper fluid is pretty clearly marked.  Even had a hood prop where I expected to find it.

So thumbs up to Chevy for making that much obvious.

Weirdly, I swear there’s a fan and radiator in there somewhere.  For sure, there are several little reservoirs that look like they hold coolant.  Plausibly that’s all part of whatever manages the temperature of the battery and the electronics.

It’s magic, as far as I’m concerned.

Plus it runs at a lethal 350V DC.  As long is to works, leave it be.

And pour carefully.

Post #2076: Snow day.

 

Today, Monday 1/6/2025, is a snow day.

From the sound of it, at 7:45 AM, we’re getting wintry mix here in Vienna.

It’s our favorite form of winter precipitation.

Can you keep yourself warm by burning sticks in your wood stove?

Yes.  Give me enough sticks, and I will stay warm indefinitely.  Proven.

But no, I’m never going to do this again.

Above left, note wheelbarrow full of (dry) sticks.  I started this winter with several such, along with a few trash cans and plastic totes full of similar material.  That,  courtesy of taking down a couple of small trees in my yard this past summer.

Above right, is the modern wood stove insert, with blazing fire made out of sticks.  Sticks, obviously, broken small enough to fit into the firebox.

Above, between, are the almost-empty firewood racks.  So there’s no doubt that it’s the sticks I’m burning.  And note the two fire extinguishers.  Because nothing says fun-at-home like a blazing fire right next to a big, loose pile of kindling.

I have no problem bringing my wood stove (insert) up to a good operating temperature by burning loads of sticks, instead of nice chunks of firewood.  In fact, dry sticks burn too well, so some of the work is keeping the fire down to a reasonable size.  No problem keeping it that hot for hours, with the circulating fan pumping hot air out into the room.

It’s just a real pain in the butt to maintain that fire.  Not quite a full-time job, but hardly a relaxing fire.  I have to toss in another handful of sticks every 15 minutes or so.  And it’s fiddly, with a handful of sticks being a less stable fuel source than a solid chunk of firewood.  Keeping a fire going with nothing but sticks is nothing at all like putting a couple of logs in the firebox once an hour.

I’m going to burn through the rest of my stock of sticks in the next couple of nights.  Then I’m never going do to this again.  This, being, burn up a large amount of small branches in my wood stove.  Not worth the effort, the indoor air pollution, and so on.

But, if I had to stay warm, and had no firewood, it’s good to know that a wheelbarrow of sticks will get me two, maybe three, hours of usable fire.  Burning it an open handful — call it a 5-inch bundle — at a time.

Conclusion

My wife and I were both reminded of that part of Little House on the Prairie, The Long Winter, where the Ingalls family stays alive by constantly feeding sticks of twisted straw into their wood stove.

I absolutely can produce a fine quantity of heat by feeding a steady stream of bundles of sticks to a modern (air-tight) wood stove.

Or, I could just turn up the heat pumps.

In any case, as a way to get rid of nuisance wood, to some good purpose, this is fine.  Or, if it were an emergency, likewise fine.

But doing this on purpose, now that I’ve done it once?  Nah.  Too much work, too much indoor air pollution.

I’ve thought about buying in more firewood, but for a lot of reasons, I’ve decided not to use my wood stove as a serious source of heat any more.  Not here in the ‘burbs of DC.

Maybe it was the Canadian forest fire smoke of (now) two summers ago, maybe it’s that I have a much-reduced need to “balance” heating and cooling from my ground-source heat pumps.

I will still burn wood occasionally, I guess.  And it’s nice to have as an ultimate back-up heat source.  But I’m no longer going to do what I used to do, which is burn through a couple of cords of wood over a winter.

But now I know I can keep my house from freezing, by burning sticks in my wood stove.

Yay?  I hope I never need to know that, practically speaking.

Post 2060: My life with a two-headed three-ton ductless mini-split.

 

I’m now the owner of a two-headed three-ton ductless mini-split.

And lovin’ it.

 

Pictured above:  Those boxes, on the wall, are the inside portion of my new ductless mini-split heat pump.

They blow hot air.  They blow cold air.  When you ask them to.  One per room is adequate, unless you dwell in a house of unusual size.  And one per room is required, if you want heat (and AC) in that room.

The outside, it’s about as attractive as you would expect, for a heat pump.  Slightly uglier than a standard system, owing to the need to run refrigerant and electrical lines up the outside of the house, to each of those interior boxes, connecting to the compressor unit at ground level.  Here, the line covers (the things that look like aluminum downspouts) blend right in with the electrical, phone, FIOS and whatnot already hanging off the vinyl siding at that end of the house.

For me, they were less expensive than my closest alternative. I paid $13K installed, $11K after the Federal tax credit.  If I’d replaced my dead ground-source heat pump, it would have been $25K, $17.5K net of (a much higher) tax credit.  I picked the contractor based on reputation, on a friend’s recommendation, and on the fact that we were immediately on the same wavelength, regarding a nice, simple installation.

Mine is a three-ton (36000 BTUH) compressor, hooked up to two 1.5 ton heads.  Took a day and a half to install, but the HVAC guy was training a couple of guys, so a one-day install would not have been out of the question if I’d been in a hurry.

These Mitsubishi units will produce heat down to 5F.  Below that, I think they automatically shut off.  At 5F, their heating efficiency will have fallen to the point that they were merely twice as efficient as an electric space heater (COP 2.1), instead of 3.5 times as efficient (COP 3.5) at 47F.

The same company (Mitsubishi) that makes these makes a “hyper heat” compressor that will run at outside temperatures down to -13F, but the outside pieces (the compressors) for those run about twice the cost of a standard compressor, near as I can tell.

We got a standard unit that’ll only function down to 5 degrees F.  But, thanks to global warming, that should do us, as this decade’s USDA hardiness zone maps bumped us from Zone 7A to 7B, meaning that 5 F is not a bad guess for the lowest temperature we’ll ever see here, ever again.  And if not, the old gas-fired hot water baseboards still work.

On paper, they’re as efficient as any other option I could get, including ground-source heat pumps.  I did an entire post on that earlier (Post #2032).  Once I got up an apples-to-apples comparison, the near-equality was obvious.

For typical winter temperatures around here, these ought to run at around COP 3.5, or, as noted, three-point-five times as efficient as an electric space heater.  In practice, they look like they’re going to do even better than I thought, owing at least to their “inverter” continous-speed technology.

I get the distinct impression that these heat pumps, with their variable-speed compressors and blowers, like being operated for long periods of time, at a relatively low load.  So I’m rethinking my life-long habit of nighttime temperature setbacks to save energy.  Don’t now what the outcome of that analysis will be.

The only thing you really need to install one is a place to put the compressor (near where the inside heads are), and some way to run a 220V electrical line there.  The electrical power for the interior heads is routed through the outside compressor unit.  So the electrical lines for the interior heads run right alongside the refrigerant lines.

And you need to have an empty 220V breaker in your electrical panel, of about the right size.  This three-ton unit needed a 25-amp breaker.  The installer just pulled the wires out of the breaker for the now-useless ground source unit, and put in the wires powering the new one.  The legally-required outside electrical cutoff comes with surge suppressor built in.

The refrigerant is R410A, which seems to be the only option for any HVAC equipment that I could buy.  It has greatly reduced ozone-depletion potential relative to old-school Freon (R22), but it’s still a potent greenhouse gas.  Less than ideal, but that’s what commodity heat pumps are using.

Some background follows.

 

Ductless mini-split.  A product clearly named by its competitors.

It’s just a normal heat pump.

The best way to describe it is by contrasting it with “normal” central heating/AC.  For a single-family home, the typical central heat/central AC set up is:

  • one hot/cold coil in the house
  • sitting inside a blower housing
  • typically in your basement or attic,
  • blowing conditioned air into your ducts, and from there to all the rooms of your house.

A mini-split is decentralized heating and AC, as far as the inside of the house is concerned.

  • one hot/cold coil in each room,
  • sitting in its own stand-alone blower cabinet,
  • blowing conditioned air directly into the room,
  • and so cooling or heating that one room.

Outside, by contrast, a typical mini-split system is more-or-less the same as central heating systems.  For reduced installation cost (and, I’d bet, better operating efficiency), you run multiple mini-split “heads” off one outdoor compressor unit.  This then requires you to run multiple sets of refrigerant lines to that one compressor, as opposed to the one set that would run to the compressor in central (ducted) forced-air system.

You pick the combination of outside compressor and inside head(s) to give you what you want.  My outside three-ton unit can take from two to four heads, as long as the total “ton” capacity of those heads is three tons of cooling (36000 BTUH).  Available compressors and heads both span a range of tonnages.

Nothing about the name “ductless mini-split” is even the tiniest bit helpful in understanding what it is.

First, it’s not mini.  It’s a full-sized HVAC unit, in terms of heat and cooling capacity.  Ours is a “three-ton” unit, meaning 36,000 BTUs/hour cooling capacity.  This is roughly the same as the heat pump it replaced.  In this climate, that’s enough for a small house, or, in our case, the first floor of a larger house.

The only “mini” part is that these units have compact, quiet outdoor part.  Two strong men can lift and carry one, and just bolt it down in place, as a unit.  So they are mini, in that the outdoor (compressor) piece of this isn’t a big louvered metal box that makes a hellacious racket when the AC or heat pump comes on.  Which is the tradition in the American ‘burbs.

Second, split just means “normal”.  As in, there’s an inside part, and an outside part, and some refrigerant lines and wires connecting the two parts.  Just like every suburban home central AC that you’ve ever seen.

Arguably, the only AC system you’ve ever seen that isn’t a “split” unit is a window air conditioner.  There, the outdoor and indoor components are in the same metal box.  But any home central AC you’ve ever seen is a split unit.

(And I now know why “split” is even a thing, for HVAC contractors.  For ground source heat pumps, you actually do have an alternative to split units, called “package” units, where the heat pump and the air handler (that blows the heated or cooled air into your duct work) are combined in a single box.  These units get a generally higher efficiency rating than split units, but I never did decide how real that was.  It almost seemed as if that might be a side-effect of the way these were tested.  Anyway, split versus packaged matters for ground-source heat pump options, but pretty much for nothing else having to do with home HVAC.)

Third “ductless” just means that the part that blows air around your house is a self-contained blower unit.  Typically, the “head” resides in a plastic cabinet, mounted high on a wall, as above.  But you can get them as console-type units.  Or as units that recess into the ceiling.  (And there are, in fact, ducted versions of these, where they are set up to be connected to a set of duct.  But that’s not their selling point.)

Not pushing air through ducts gives these a modest energy advantage, all other things equal.

But a downside of “ductless” is that there’s no air return in this system, as there is an a traditional central forced-air system.  Air does not flow out of the ducts, toward the return.  It just flows out into the room its in.  That limits these to heating essentially one open space per head.  OTOH, these units seem to have no problem throwing warm air for a considerable distance.

It’s a different heating and cooling gestalt

In the typical central forced-air heat or AC system, you blow air out the ducts, and suck it back up in some distant central air return.  This means that air flows through all the rooms, and you can count on that air flow both to mix the air, and to make the conditioned air travel the full distance from duct outlet to return inlet.  Ideally, the result is a uniformly heated or cooled living space, and no apparent breezes.

A ductless mini-split is a different beast entirely, and no nearly so elegant as central forced air.

There’s no air return.  This limits the “throw” of each unit to the space in which it can manage to blow its warm or cold air.  The result is that a) you definitely get a warm breeze if it’s really cranking, and b) the air temperature in the room is not as uniform as it is with central forced-air systems.

Neither of which bothers me in the least. I actually like both aspects.  And mine are strong enough to heat the living-dining room from one end to the other, which has to be 30-some feet.

The upshot is that if you want nice, uniform, breezeless heat throughout a room, these are not for you.  As far as the user is concerned, these are more like having the best space heater you’ve ever used, hanging on the wall of your house.  It works well, but not as nicely as a properly-configured central forced-air system.

(N.B., a 1.5 ton head is 18,000 BTUH, which equates to the heat you’d get from about a 5000-watt resistance space heater, where the biggest plug-in 120V space heater you can buy is 1500 watts.  The astute reader will recognize that 5000 watts at 120V would be … way more electricity than the entire compressor uses, if it sits on a 25-amp breaker.  Which is neither a violation of the laws of physics nor magic, but the whole point of using a heat pump, because the coefficient-of-performance (COP) is bigger than 1.0.  You do, in fact, get more heat out of it, than is embodied in the energy it takes to run it.  Because it’s not a heater, it’s a heat pump.)

 

The back story

In 2004, the previous owner of my house had a ground-source heat pump system installed.  Mile of pipe buried in the back yard, hooked up to two heat pumps, retrofit to the existing duct work, using the existing hot-water gas-fired baseboards as secondary heat for the heat pumps.

(Secondary heat is the additional heat source the system turns on if it looks like it’s taking too long for the heat pumps alone to bring the house up to temperature, or maintain temperature.)

In 2007 we bought the house thinking, neat, that’s the most efficient heating we can get.  Only after we lived with it for a while did we fully appreciate what a botched Frankenstein’s monster our heating system was.

This 1959 home was an energy use nightmare.  (Ah, bad dream, maybe.)  Rather than insulating the attic and ceiling spaces, or dealing with the huge air leaks, or the (believe-it-or-not) uninsulated walls, or the four big open fireplace chimneys, … the previous owner figured he’d just install his high-tech redneck heating system and be done with it.  And botched that install in several important ways, to boot.

For example, I ask you, what sane home buyer looks at a nice new high-end kitchen remodel, stone countertops, cherry cabinets, stainless high-end appliances and says, that’s a very nice kitchen, but, does that come with heating and cooling?

Because in my case, the answer was no.  They tore out the old hot-water baseboard heat and, to a very close approximation, replaced it with nothing.  Which, as the owner, you don’t really figure out until winter sets in, some time later.

What sort of person would do that, in their own kitchen remodel?  The same sort of person that did all the rest of the HVAC system.  Near as I can tell, absolutely no aspect of it was planned or executed well.  Let me omit the rest of the kvetching by saying that it has never worked well.  And the kitchen is always ass-freezing cold in the winter.  And that, upon closer inspection, that last problem seemed un-fixable.

So we let Frankenstein be.  And did a lot of baked goods in the winter.  Slow-cooker recipes.  And so forth.

FF to 2024.  The ground-source heat pump for the first floor is dead,and the one for the second floor is failing.  And I wasn’t shedding tear over its demise, given the miserable performance.

Until, that is, I found out it was going to cost me $50K to replace them.

But there’s nothing like a pending major expenditure to sharpen your focus, if not your wits.  For various reasons, my wife and I decided that it was stupid to spend $50K to repeat the previous owner’s mistakes with fresh equipment.  And that maybe, just maybe, for the first time since we moved in, we could actually have a warm kitchen.

Our solution was to ignore the dead ground-source heat pump, ignore the grossly under-sized duct work, the cobbled-up secondary heat, the @#@#$ wireless thermostat that worked sometimes.  Rather than try to work around the same problems that the last guy was unable to fix, we decided to start fresh with an air-source ductless mini-split that had nothing whatsoever to do with the existing Frankenstein of a system.

And that’s how we ended up here.

Post #2036: Replacing my heat pumps III: The tax angles.

 

Winter approaches. 

But no pressure, as I slowly work through the tax angles on this HVAC equipment replacement decision.  And bring somebody in for another quote for new equipment. And maybe, eventually, get everything working again.

If nothing else, this whole episode shows me that it’s good to have multiple heating systems in your home.

Even with one heat pump dead, we have some heat.

And that is way better than no heat. Continue reading Post #2036: Replacing my heat pumps III: The tax angles.

Post 2035: Oh for ducts’ sake!

 

This is a further installment in my two-dead-heat-pumps, gonna cost me $50K and up to fix it, saga.

Today’s punchline.  My 1959-vintage first-floor HVAC ducts are, objectively, way too small to work with a modern heat pump.  The main duct is roughly one-third the size (cross-sectional area) it needs to be.

We could put the best ground-source heat pump in the world at one end of those ducts, and the kitchen at the other end of the air duct would still freeze in the wintertime.

If feasible, we’re going to replace (one of) our dead ground-source heat pump(s) with a couple of ductless mini-split air-source heat pumps.  Just bypass the grossly undersized ducts entirely.

Sounds like a fundamentally stupid thing to do.  But not so, in this case.  I think.

Never make fun of the size of a mans ducts.

I finally got the bright idea to measure the size of my first floor ducts.  The ones that barely function. Admittedly, guessing about it was more fun.  And even if I knew the dimensions, figuring out the “right” size is an engineering black art.

But I had a hunch that a quick ballpark answer would be good enough.  The main duct measured out at 0.75 square feet in cross-sectional area.  The first floor of the house is about 1500 square feet.  Per two on-line rules of thumb, the original 1959 ducts are about one-third as big as they need to be.

That squares with the rest of it.  Not just their abysmal air delivery, but just by eye, the cross-sectional area of the main duct is about a third that of the plenum to which it is attached.

I can easily believe that the folks who originally installed my ground source heat pump installed a super-duper ground-source heat pump, then blithely hooked it up to grossly undersized duct work. It’s of-a-piece with the rest of the shoddy retrofit they did before selling the house.

But the ducts themselves appear to be much, much older.  They’re behind plaster walls, for one thing, and I’ll swear that plaster has never been disturbed.  They are in an unusual configuration, with both ground-level ducts, and ceiling-level ducts that must be fed by long risers.  The guy who built this house seemed to build pretty good houses.  How’d the original builder manage to put in such goofy undersized ducts in the first place?

I now think that these first-floor air ducts were originally designed and sized for use with a gas-fired hot air furnace.  The air coming out of one of those is very hot, and so quite energy-dense, compared to the lower-temperature air you would typically get with a heat pump.  Not only would you have to move less air to heat an area (thus requiring smaller ducts to move it),  you probably got a considerable “chimney” effect in the vertical risers that serve the many ceiling-level vents.  (Vents that, in the current system, seem to do absolutely nothing.)

In the end, it doesn’t matter.  A few simple checks all tell me that they are, in fact, just way too small for use with a modern HVAC system.   

Twenty years ago, they cut a major corner in the original ground-source installation.  For 20 years, system performance must have been sub-par as a result.  For sure, for 20 years, the kitchen has been freezing cold every winter.

It’s time to fix that as best I can.

Rule number 4:  Yes, they really can be that stupid.

 

A buddy of mine once gave me a little laminated list of rules for life.  Rule number 4 was as stated above.

At root, my biggest problem so far with this two-dead-heat-pumps fiasco is forgetting Rule #4.  Because, when I bothered to check, sure enough, the folks who retrofit this charming home with a super-expensive ground-source heat pump system then proceeded to hook one of those heat pumps up to grossly undersized ductwork. Which made the entire point of installing an efficient heat pump almost completely irrelevant.

And so it has remained for two decades.

And now, completely contrary to the conventional wisdom, it makes sense to  replace a worn-out ground source heat pump with an air-source heat pump.  If for no other reason than to bypass the undersized ducts.

Addendum:  Or duck the ducts.

I finally got it.  The story ends … and you can’t replace the duct, because a properly-sized main duct would stick down too far in the basement.  So not only didn’t they replace the ductwork, they couldn’t replace the ductwork without losing standing headroom right down the middle of the finished basement.

This situation is no-one’s fault.  It is what it is.  Deal with it.

Post 2032: Replacing my heat pumps, part II: How efficient are my ground-source and mini-split heat pump options?

 

The key question for this post is about as simple as it gets: If I have two choices for heat pumps, which one will use less electricity?

In my case, one option is the replacement ground-source heat pump that has been recommended, at a base installed price of about $25K per heat pump.  The other option is to replace my dead ground-source heat pump with a modern air-source mini-split heat pump, at somewhere around half that cost (call it 60% after adjusting for likely difference in equipment life, in my particular case).

This is a stupidly hard question to answer well.  As I explain at length below.

But, after doing all the homework that I care to do, for my house and my climate (with mild winters and an efficient gas-fired secondary heating system), the answer is that either style of heat pump (air-source or ground-source) will use roughly the same amount of electricity.  Or near as I can tell, based on published data.

That’s not due to the underlying physics of the situation.  If it were only about the physics, ground-source would win hands-down.  Instead, that appears mainly due to faster technological improvement in air-source units over the past decade or so, compared to ground-source units.  This seems to have fully offset the “natural” advantage of ground-source.  In effect, my real-world choice is between air-source using the current generation of technology, and ground source using older technology.  (The model of ground-source heat pump I have been offered was first introduced in 2016.)  Or, at least, using a less-efficient design for the heat pump itself, disregarding which heat sink (air, ground) is used.  That’s what makes it a tie ballgame, as of now.

This leads me to conclude that replacing one of my dead heat pumps with (e.g.) a name-brand air-source mini-split system:

  • Is substantially cheaper, even accounting for likely shorter equipment life.
  • Incurs no significant loss of efficiency compared to my ground-source option.
  • As a bonus, bypasses my house’s barely-functional 1959-era ductwork.

Ground source systems still have some clear advantages.  All the equipment is indoors, and so likely lasts longer.  They work well even extremes of cold or hot weather.

But the fact is, there just ain’t that many of them, particularly in a relatively mild climate like Virginia.  Of the roughly 4 million annual residential heat pump installations per year (in 2022), maybe 50,000 (call it 2.5%) were ground-source units.  That has big implications for how rapidly the units reflect improved technology, and how much choice you have for who installs and services your unit.

Unless some unforeseen problem arises, I will replace one three-ton dead ground-source heat pump with a pair of 1.5-ton mini-split air-source heat pumps.

And I will not feel the least bit guilty about doing so.

I was going to give full and excruciating details but the overall accuracy of the conclusion does not warrant that.  Below, I sketch out enough to summarize how I arrived at the numbers above.

SEER, EER, HSPF, COP, and all that jazz.

The efficiency of a heat pump varies, based on the how big a temperature difference it is trying to pump against, and how close you are to the maximum capacity of the system.  The bigger the temperature difference, and the closer to maxed out, the less efficiently the heat pump runs.

This means that, despite what you read from many internet sources, you cannot simply convert one heat-pump efficiency measure to another with a simple conversion-of-units number.  Yes, you must do that first, because some of these measures mix BTU/Hs and watts, and others don’t.  But in addition, you also have to make some sort of adjustment for how stringent the test is.

It’s very much like EPA mileage.  The MPG the EPA gets depends on how the car is driven.  Typically, EPA city mileage is much worse than EPA highway mileage.  If you compare the city MPG of one car to the highway MPG of another, you’re making a mistake.  So it is, in spades, with SEER, EER, COP, and HSPF.

Now we get to the hard part:  Things are hazy.

If you Google SEER, say, you’ll see the same zero-details definition everywhere:  It’s the ratio of the cooling power produced (in BTU/H), to the electrical power supplied (in watts).  But as to, how, exactly, that’s measured, it’s hard to find any information at all.  E.g., is the energy used to run the water pumps included, what indoor and outdoor temperatures were used for the test, how were ducts, water pumps, etc. factored in, and so on.

  • The details of the tests are proprietary and reside behind an expensive paywall.
  • For the same measure, ground-source and air-source heat pumps use different methods.
  • Certain aspects of overall energy use — duct system back pressure, water pump electricity use, and resistance electrical heating for backup heat — are either ill-specified, or not stated as to impact.

Among the things that I’ve seen hints for, but no definitive answer, is how these tests treat the waste heat of the electric motors themselves.  I saw at least one credible-looking website showing that ground-source heat pumps add the value of this waste heat to their heating output, as if that heat would make it into your ductwork.  But air source heat pumps do not.  That’s consistent with where the compressor is located (inside for one, outside for the other).  But it boils down to an assumption that the waste heat of the compressor motor somehow warms the air in your ductwork, which clearly isn’t the case for the units in my basement now.  I have yet to find a clear answer on that, and it matters materially to the comparison.

So you need to take the table above with a grain of salt.  My interpretation is that if there is a difference in efficiency across the three units I looked at, it’s small.

Definitions

Each of these measures compares output heating or cooling power, to input electrical power used.

EER (energy efficiency ratio).  Cooling.  Measured at a steady 35C outdoor air temperature, 26C indoor air temperature, and 50% relative humidity (for the outdoor air?).  Heat/cool is measured in BTU/H, electricity is in watts.  I think the test calls for the unit to run full-blast when this is measured.

SEER (seasonal energy efficiency ratio).  Cooling.  Near as I can tell, this is set up to simulate the range of temperatures you would see in a “standard summer”, so to speak.  Heat/cooling power output is measured in BTU/H, electricity input is measured in watts.

COP (coefficient of performance):  Heating:  Generically, COP is simply watts of heat out, divided by watts of electricity used.  Heat pumps have different COP values depending on the temperature tested, and how hard they were running.  But the EPA-reported COP appears to be for one temperature, and I think its with the unit running full blast.  Heat/cooling power is measured in watts, electrical input power is measured in watts.

HSPF (heating seasonal performance factor).  Heating.  Like SEER, this tests the units over a range of temperatures designed to be a sort of “standard winter”.  I believe that, where the unit has a resistance-heating secondary heater, if that clicks on during the testing, the electricity used in secondary heating is counted toward the total.  Heating power is measured in BTU/H, electrical use in watts.

The -2 suffixed versions of these appear to include a more realistic measure of the back-pressure of typical home ducts.  Best I can tell, in the typical situation, you’d expect the (e.g.) SEER2 rating of an appliance to be 5% to 10% lower than the SEER rating.

Accounting for test stringency:  SEER to EER conversion, units-adjusted HSPF to COP conversion.  Here, I found some sketchy internet sources suggesting that where you have SEER and EER for the same unit, SEER is typically 85% of the EER value, due to the more stringent testing cycle.  So I used that to adjust these all to a common EER-style basis.

Conclusion so far

Again, take this table with a grain of salt. There’s a whole lot I don’t know about the details of how each test is applied to each type of machine.  And probably never will know, particularly for the details of testing ground source machines, where tests specifying outdoor air temperature are irrelevant.

That said, if you adjust for the difference in units-of-measurement (BTU/H versus watt), and assume that the tests that use a broad range of conditions (SEER, HSPF) tend to run about 85% of the equivalent tests that use a single set of conditions (EER, and COP as EPA reports it), then you get the comparison above.

Which, honestly, is just about what I came up with, back-of-the-envelope, when I first looked into this some years ago.  The super-high-SEER Japanese-made heat pumps that emerged a decade ago seemed to eclipse (my estimate of) my existing ground-source heat pump’s efficiency.  SEER 25? Maybe I mis-recall.  But I do recall being startled with how high the available SEER ratings got, for air-source units.

Bottom line, efficiency-wise it’s a tossup.  If I weight each units two numbers by local degree-day (3x heating a cooling), I get my estimated all-year efficiency values of 3.6, 3.5, and 4.0 for the three heat pumps examined, respectively.)

If your location experiences lot of time at extremely cold or hot temperatures, ground-source heat pumps still seem to offer some significant efficiency advantages over air-source.  And, for sure, because the equipment is all inside, ground-source is likely to last longer.

But in my case — with a relatively mild climate, efficient (gas-fired) backup heat, and so on — it’s six of one, half a dozen of the other.

Finally, this pretty strongly suggests that the current tax law is out-of-date.  The huge advantage given to ground-source heat pumps might have made sense in 2004.  It appears to make no sense in 2024.

Once upon a time, ground-source heat pumps were king.  But not any more.  And the law has yet to catch up with that.