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Joined on August 20, 2009

Last Post on February 28, 2014

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@ July 1, 2013 9:28 AM in Solar Thermal is Dead

unless you ignore insurance, cleanup, and storage of waste.

as of now it is impossible to insure a nuclear reactor at any price. hard to think it'll be "3 cents" or whatever after all that is taken care of.

what's the cost for containment for thousands of years? oh right, we have no idea, because there is no such thing as reliable containment for thousands of years.

woulda coulda shoulda

@ June 28, 2013 8:51 AM in Solar Thermal is Dead

but didn't.

"But even were its commercial viability established, given 2010's soaring greenhouse gas levels, thorium is one magic bullet that is years off target. Those who support renewables say they will have come so far in cost and efficiency terms by the time the technology is perfected and upscaled that thorium reactors will already be uneconomic. Indeed, if renewables had a fraction of nuclear's current subsidies they could already be light years ahead."


@ June 21, 2013 4:56 PM in Sloped ceiling insulation problem

I kind of love for that.

fair enough

@ June 21, 2013 1:20 PM in Sloped ceiling insulation problem

good paper on the issue here:

I dunno

@ June 21, 2013 11:19 AM in Sloped ceiling insulation problem

I only know that venting cladding in any insulated roof assembly is kind of a strong recommendation.

I would add

@ June 21, 2013 9:50 AM in outdoor reset for radiant floor heat

that if you already have the indirects, keeping them is fine, they are good buffer tanks. mix off of them if you like.

I would hope this is a tank in tank style indirect as well... certainly not that you are pumping potable water through your radiant?

I don't see

@ June 21, 2013 9:48 AM in Sloped ceiling insulation problem

how spray foam helps compared to cellulose here. if you fill the bay right to the roof decking and the singles are on the other side, that's usually a problem unless the cladding (shingles in your case) is itself vented. if the shingles are vented underneath then you don't need venting in the insulation assembly under the deck. am I missing something?


@ June 19, 2013 12:49 PM in Condensor to Water conversion

those are intriguing but they don't seem to have that much water content so we'd still need to have a buffer tank to ensure proper runtime of the condensor. good people to talk to though I bet, thanks for the link.

for chilled water

@ June 17, 2013 3:54 PM in Condensor to Water conversion

a major benefit is being able to decouple the load from compressor operation and do real zoning. so a buffer tank is necessary to ensure adequate runtime from the compressors in most cases. inverter driven compressors can help but then it's a control issue I can't easily solve... they don't take 0-10vdc signals as of yet that I'm aware of...

but with external HE we have to prove flow before we let the compressor run, and it requires the HE, pump, flow switch that are not required if we put the HE *in* the tank like a top coil would achieve.

so if it works,I'd vastly prefer a top mounted coil in an indirect as a heat exchanger for this setup. drop a failure-prone flow switch and an energy-using pump and two major vectors for failure that could damage the compressor, plus a lot of assembly time and labor and wiring.

but I don't know if refrigerant will like that... the unit on the outside, the condenser, is basically a big coil of copper so I think it should work?


@ June 17, 2013 2:40 PM in Condensor to Water conversion

I imagine it would be something like

1. thermostat places cooling demand
2. energize tank cooling aquastat
3. when aquastat requires heat rejection, engage condensor
4. when aquastat is satisfied, turn off condensor.

ta daaaa!

if we do it with a heat exchanger external to our buffer tank, we have to use flow switches and an extra pump, plus a lot of install labor. thus the question about using a copper coil in the top of a tank...

we already do

@ June 17, 2013 2:19 PM in Condensor to Water conversion

with heat pumps. looking for a way to extend this more cost effectively to people who have more traditional heating equipment like boilers. or with larger cooling demands.


@ June 17, 2013 12:38 PM in Condensor to Water conversion

I'm trying to take a regular outdoor condensor unit and make it a chiller for chilled water applications like radiant cooling etc.

right now the upcharge to go chiller is pretty large... mostly because of the much, much lower volume of such units in production and all the testing etc required to sell them.

a cost effective method of utilizing more typical outdoor condensors would reduce the cost of chilled water systems.

Condensor to Water conversion

@ June 17, 2013 11:33 AM in Condensor to Water conversion

We are aware of people using brazed plate heat exchangers to turn a condensor into a "chiller", along with a buffer tank, flow switching, etc.

I am wondering... is there any reason we couldn't source a "top coil" indirect water heater, and pipe the refrigerant to the top coil, and do the same thing? this would eliminate several service items and significant cost, I believe. but I'm not sure how the refrigerant would like it.

I imagine the critical detail would be in selecting the temperature hysteresis and operation range to make sure you get the heat rejection you need to keep the compressor running and happy. but maybe there is more consideration than that?

there are 3 major issues with nuclear

@ June 11, 2013 8:46 AM in Solar Thermal is Dead

1- pollution from source extraction of uranium. not the hugest problem, but it's an issue.

2- safety. SWEI nailed this... when they can afford to privately insure, maybe it will make sense. with highly qualified and regulated insurers, of course.

3- storage. when we don't have a waste storage issue anymore, great. until then, even the best waste results I'm aware of stretch into timeframes longer than our country has even been a country. Seems unlikely we can ensure the safe storage of such waste. Maybe when we have a safe way to hurl it into the sun or something...

Hey, the sun. that's nuclear. it's in your backyard! Maybe we should stick with that ;)

Read it again.

@ June 7, 2013 1:45 PM in Delta-P/Delta-T Part #5

John is saying that 2 small zones running could run faster than all 3 zones calling. in his blog, condition "b" vs condition "c".

that is not possible in a real system with the equipment he is talking about.


@ June 7, 2013 1:23 PM in Delta-P/Delta-T Part #5

straw man there. I didn't say you couldn't change pressure.

I said: you cannot SPEED UP a pump by CLOSING zone valves. not in a real, operating system. but his analysis says, in fact, you can.

I have

@ June 7, 2013 11:01 AM in Delta-P/Delta-T Part #5

a lot of respect for john... he was the first trainer I ever experienced in this industry. he's a great guy.

but the fact is you cannot make a pump speed up by closing zones. can. not. happen. ever, in any circumstances, no matter what.

so he is NOT educating and he is NOT being even handed in this matter. he's wrong. and he's using sales BS... either intentionally, or mistakenly. but either way, this is a fluff piece, not serious analysis.

Delta T has a place. Delta P has a place. but Delta T doesn't get its place by being misleading about how Delta P operates.


@ June 5, 2013 7:37 PM in Icynene insulation!!!

HRV/ERVs do more than one thing. They reduce energy loss, that's true. and that's important. they can eliminate bath fans, which is a nice way to offset some of their cost and improve the economics of their usage. but they also can filter incoming air, which is a very nice benefit, and most importantly, they ensure good air quality to all areas you duct them too... at least as good as filtered outside air.

no leaky building can say the same. just because air leaks in... somewhere, under some conditions, at some speed, through a dirty wall cavity or floor cavity or whatever... that does not mean you have consistent or predictable good quality air. All you can say is that in climates where outside air is dry that you've mitigated some potential for moisture problems. but leakage where you don't want it can pose greater moisture risks in many cases than you solve. Exfiltrating 2nd floor air in the winter, for example... bad news. it's warm and moist. it crosses a dew point. consistently and for a long time, right there in the wall cavity. you carry WAY more moisture in the air than you do through simple vapor transmission through any material...

tight homes can screw up their building science too, and have rot and mold... absolutely. You still have to get it right. but almost everything I posted above is straight from and Joe knows his stuff pretty well. Certainly we know better than to build leaky homes in a high cost energy environment (i.e., the world, these days). And if you actually care about health, controlled fresh air delivery cannot be beat.

Fiberglass is poor. so why use it? cellulose is much better. cellulose with exterior rigid foam is a whole 'nother league. and not much more money. economics are excellent there.

Window upgrades are a separate issue, sure. double pane low-e is still pretty good. right now there aren't many economical triple pane options that make trading up worthwhile unless you have big glass near sedentary space and you want the comfort improvement. but there are some lower cost triple panes out there from what I've seen... are they any good? dunno. but at any rate just because building tight is the right thing to do, that doesn't mean that every possible energy upgrade you can do has good ROI... absolutely agreed on that.

I have a shop with all exterior rigid foam walls (over zipwall) and a cellulose ceiling.. we stuck with double pane low-e windows as well. only made sense. wish I'd planned my southern overhangs better and knocked out some western glass. blah. live and learn.

from a health, comfort, AND energy perspective all together though, ERVs do.

what I've seen and read say

@ June 5, 2013 1:44 PM in Icynene insulation!!!

1- never use an open cell foam product in a roof assembly unless it's a layer inside a layer of closed cell. too much of a chance of moisture intrustion and then you've got a huge moisture battery in your roof assembly. I've seen people really regret that decision.

2- always vent your cladding. this prevents any drying issues to anything important. Any time you are sealing well and using foam, vent the cladding.

3- never put more than one vapor barrier in. but where it is doesn't matter at all as long as the assembly can dry to one side.

4- insulation on the outside is better than on the inside. as Mr. Joe says, warm wood is happy wood. I have a shed outside my home right now, completely unheated, wood open to air on both sides. guess what? the wood rots anyway when it's near splashes and the ground. so control your water and worry a lot less about your vapor and dewpoints.

5- you can't "naturally breath" a house to good air quality. all you can do with "natural breath" is waste energy, reduce moisture related problems, and open up large vectors for moisture intrusion and rot. Seal it tight, vent it right... we learned this 40 years ago.

6- if you're still using fiberglass batts without an exterior foam layer, you're doing it wrong. Batts are poor quality insulation.

7- polyiso offgasses and loses R value as it gets colder. dont' waste the money. use EPS for rigid foam. it's greener too.

8- thermal bridging is serious business and so continuous rigid foam is better than cavity foam in almost all cases.

the marketing BS in this

@ June 3, 2013 5:08 PM in Delta-P/Delta-T Part #5


You absolutely cannot make a pump run faster in constant pressure mode by closing zones. That's a ridiculous statement. It will run as fast as it needs to in order to create a certain amount of pressure. opening up additional zones makes that a REQUIREMENT that it run faster to maintain the same pressure.

that's like saying you can fill up a bucket by drilling a hole in it.

Taco is losing a LOT of respect from me with their really, really bad arguments for the bumblebee. trying to claim you can make a boiler cycle less by slowing down flow... also a very poor argument.


@ May 29, 2013 8:07 PM in Solar Thermal is Dead

you said YOU have a 20 year payback. Are you going to sell that system to your customers at cost? No one but you, or another professional can install your system at your price. right? All my numbers so far have been installed retail. even IF your number is retail and not your cost every thing I've said still holds true, it's just less dramatically true.

Your analysis on chasing more energy is also not correct. Your price to collect 3x the solar is not 3x the cost. it's significantly more than 3x because you are trying to collect during time periods where the solar just ISN'T THERE. So your payback gets longer and longer because the cost to collect more of your load goes up and up faster than your collection does... because you are wasting more and more of the capability of every panel you add after your baseline DHW load is met at optimal summer tilt.

I agree that solar thermal SHOULD last a long time. Many do. but a lot of systems definitely don't... maine has a lot of abandoned solar systems that the local plumbers couldn't keep in service or didn't save enough to make it worthwhile. it's got moving parts and thermal stressed and maintenance requirements that PV doesn't have at all.

In 20 years energy probably will be more expensive. and I bet your solar thermal system against my PV that PV will be even cheaper then, solar thermal won't be as much cheaper, heat pumps will be significantly cheaper, and that there might even be something new in that time we have no knowledge of. But we're not talking about the system we'd put in, in 20 years. we're talking about today.

TODAY, if you want to do solar space heating, you should be looking at PV and a heat pump. That's all I'm trying to get through here. Solar thermal stops making sense after a DHW load is met... that's the only thing it can do more cost effectively than PV. Unless the very intriguing idea of solar cooling comes into play in a way I don't expect to see happen (but, like you, I've been wrong before.)


@ May 29, 2013 11:00 AM in Solar Thermal is Dead

I have seen a large number of solar thermal systems that didn't make it 15 years so I wouldn't get too snug in your assumptions there. but you misunderstand what I was saying with paybacks. the payback on PV itself is 15 years... it has a lifespan of 25+. That's pretty great.

the HEAT PUMP itself typically has a payback much faster than that (5 to 10 years), but it depends on what you compare it to... if we compare to natural gas in a heat only application, not so great. Compare to electric resistance doing heating and cooling, it's great. so pick your comparison. But if you want to compare it to the solar thermal system of a size you'd have to put in to offset the same amount of energy it does, then the heat pump doesn't need to talk about payback, it's cheaper up front and it will probably a similar level of service as the solar thermal system... i.e., not much. You need to save about 30 million BTUs/year to hang with the heat pump on that basis if you want to pencil out what that system looks like for my shop which is a heat load similar to many single family residences. I suspect you'll find that only the very smallest heat loads would shift that economic analysis.

I don't know what you're reading, but optimal economics for solar has to be for year round loads... that's DHW. Maybe if our energy was three times the cost it is now, like it is in europe, we'd see more space heat systems like that here too, especially in the past when PV was much more expensive than it is now so it would be the only solar option that really made sense. you get maximum production per square foot of panel you buy and per gallon of storage you buy (and thus, optimal return on investment) when you use everything you collect. You cannot do that by buying a lot of extra panel that is utterly useless for half the year.

HERE in america you will never pencil out a payback that makes any sense whatsoever for a solar thermal space heat system unless your labor or components are free, your subsidies are huge, or energy gets a lot more expensive than it is now. Plain, simple, fact. I will happily eat those words when you show me a payback less than 15 years on any solar thermal combo space heat/DHW system without subsidy, but you'll have to pardon me if I don't hold my breath while I wait, because quite simply I've looked at the numbers and I'm pretty sure that beast doesn't exist in the US and isn't going to anytime soon. If it does, it's certainly not the system in your house, which is awesome and great and cool and not going to save america very much energy because a 30 year payback is, one more time, a dead horse in this race. My hat is off to you for being willing to do it, of course. but I don't have many clients who would buy it. and I have a lot of green clients.

If you can do cooling, that would help a lot, but solar cooling is in two flavors, one is solar absorption chilling which is complicated and fantastically expensive here in the US, and one is night sky radiation which is limited in capacity, but might help. no evacuated tubes there, and I would love to see the performance of such systems in greater detail. Maybe that's your in, I don't know.

but right now, at today's pricing, PV is ready for prime time and dead simple to deploy. we hit the tipping point of grid parity a couple years ago and we're beating it now. significantly. moving into heating and cooling is as simple as deploying a heat pump and upsizing the array and pow, there you are.
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