I have no personal experience with radiant, but am planning to install it because I hear good things about it and I'm hoping to use solar for most of the heat load.  I agree with your comments, I'm tired of having cold feet, but that's partly because the floor could use some more insulation (current stacked around outside doing nothing - I should install it instead of typing these messages!).

I'm not advocating against radiant.  It is not the lowest cost heating solution, but I think that you get what you pay for.  The article covers a very small percentage of homes, but nonetheless raises some interesting points that I had never considered.

No solution is right for everyone.  Getting back to the original topic, I am kinda tired of listening to the pump noise from the furnace that feeds the hot water baseboards here, it seems to resonate through the all copper piping - not a normal radiant situation.  My original reason for posting was that I did like the direct vent heater because it is very, very quiet. 

I'm not trying to advocate too much FOR radiant either... I don't think it does make sense in all cases. just throwing out there that it's at least slightly more complicated than a BTU/sq ft number, that's all. I think very low loads over well heated spaces doesn't benefit much other than perhaps from a water temp perspective. but over a cold basement, more so.

good luck with your "solar for most of the heat load" thing though... that's a tough one to achieve for most people.

Sorry to be cynical Dan but when I graduated from High School  35 years ago the story was nearly identical. I suspect in another 35 years the % of our energy from gas, oil, coal and nukes will be similar to today. 

You can advocate for radiant, it is a radiant thread and I didn't really mean to hijack it. 


I'm also fighting the fact that my house is built the wrong way round.  The east and west walls are 75' and the (nearly) south wall is only 28'.

But darn it, there are about 450,000 BTU's hitting that wall on an average January day and if I can capture enough of those I can deprive the gas company of some revenue.  I'm not an environmentalist, just a cheapskate!

One thing I have high hopes for is an air panel that we're adding to the south wall.  About 100sq. ft. of glass.  The biggest problem with IT is getting the building inspector to sign off on it.  If the wall was stick-framed, he wouldn't have a problem, but since it's a SIP wall he wants an SE to stamp the design.  Have we really reached the stage where we need an SE to sign off on hanging something on the wall that is the weight of a bookshelf?  Certainly less than the weight of a kitchen cabinet.

There's a possible problem when the cost of home solar (or any other) generation becomes cost effective.  At the minute, the payback on PV is only just about there.  At half the price, a quarter of the price... it's going to become a very popular option.  It's a semiconductor technology and they have a habit of dropping - just look at computer prices.

You'll know when it's time to start looking at PV.  Wait until you see a massive push-back from the major utilities, preventing grid tie-ins, cutting prices paid for user generated power, etc. etc.  They'll be a big political uproar (and the utilities will get their way - at least for a while).  That's not cynical, just the nature of the business world they cling to obsolete technologies by political clout.

That's a  policy choice, subject to many influences. 

When you graduated from high school a huge amount of peak demand was met with #2 & #6 oil, and a significant amount of base load was met with #6 oil. (Almost none is today.)

When you graduated from high school there were hundreds of nukes at various stages of planning & construction that never got built. That was before Three Mile Island & Chernbyl, but most importantly...

...before the WPPS bond failure.

Now, even with government financing guarantees and disaster indemnity it's impossible to get private funding to build a nuke in the US. (Wall Street would STILL rather bet on sub-prime mortgages than nukes- go figure!?!!)

When you graduated from high school, shale & coal seam natural gas was a hazard & nuisance, not an exploitable resource.

When you graduated from high school there were NO micro cogenerator options, now there are several, including micro cogen systems designed to be under utility control to create grid tolerance & stability for a larger share of wind-power:  http://www.lichtblick.de/h/Ueberblick_286.php

When you graduated from high school China was a third world country with near-zero influence on international energy markets, building hydroelectric dams with coolie labor.

When you graduated from high school the US imported less than half it's oil consumption.

When you graduated from high school all utilities made their money by selling kilowatt hours and expanding capacity, before any were mandated to invest in efficiency whenever that was more cost-effective than new generation.

When you graduated from high school photovoltaics cost $200K/peak-kilowatt.  It's under $10K/pk-kw today, installed, and poised to crash as more CIGS & organic PV technology factories continue to come on line.  (NanoSolar claims to have already achieved price parity per kwh with coal with their stuff.)  Dovetailed with a more deeply electrified automotive fleet, cheap PV + smart-batteries are a grid game-changer.

If you think the energy mix is the same now as when you graduated from high school you've been sleeping in class! (You DID graduate, didn't you? :-) )  And if you think it's going to be remotely the same after 35 more years of economic growth in Asia, methinks you flagged Econ101 (but maybe didn't need it for graduation?)

Dana, Nice collection of observations,
Gregj, Had I graduated HS it would have been 1973, ( I do have a college degree though some times its hard to tell.. ).
We are in a different world then to now, the limitless Amazon has found a limit, the duck and cover kiss your ass good by is no longer part of the k-8 curriculum.
The infinite grasp of humanity has be clearly given limits.
I am not a big fan of 60 minutes on TV but recently saw there article on cyber terrorism and the concept of shutting down the grid is real.
Global warming, no doubt on the fast track.
From the capitalist point of view there is a huge marketing potential right now in the USA to set up co-generation appliances. solar PV, anything that can back feed the grid and provide some level of independence and fixed rate value for years forward. Some areas of the country naturally do not support these systems due to economic and or climate reasons.
Point is when we were in high school, there was a huge lost opportunity to push these system developments, now 35 years later it is here again but major fundamental changes are in place, there is money, technology and the great communist China has turned it machine from paper umbrellas to PV, Wind, Geo thermal, not to mention socks and teacups and tractors..... .
I read today the EU will look at %80 alternate energy in the 2050 years.
Down on the mechanics ground level there is a need to install these types of systems, and the right packages can make $ for the user and installer, go figure.
PV is headed for the $2.00 watt retail range, currently in container lots it is $1.75 watt. Installed pay back will be reduced, Honda and other manufactures are working on CO-gen with a hydronic heat domestic hot water byproduct, fuel efficiency on these units is in the %85 range.
A huge increase over current Coal, nuke,oil plants.
Enough for now
Dan

Original poster here...

Thanks for all the great posts on this thread.

Now I'm leaning toward using a simple wall-hung gas space heater (like the Robur #5002) in the main rom downstairs, then possibly it's smaller brother, the #TS-2000 in the master bedroom (or oil-filled electric baseboard), then small baseboard units in the other rooms and bathrooms. I would suspect these elec heaters would hardly ever be used, but are required to meet code. This seems like a much more simple, elegant solution to my heating problem than a complex radiant system or forced air.

I just received my numbers from the energy rater (who happens to be a consultant with Energy Star). Calcilated peak load: 14.3 kbtu; design load: 12.3 kbtu (what's the difference bewtween these two?). Annual consumption: 21.8 mmbtu. HERS rating of 52 (which should go lower if I use a high-efficiency water heater).

He used a 94% efficient forced air system in his model. The Robur unit is %82. But with no duct losses, I would assume it might be just as good...(?) Or maybe in an ICF house, duct losses are less significant?

Thanks,
-m

The Robur unit has a fan so will (obviously) have some noise associated with it.  I have no idea how much. I've heard that any unit more than about 80% efficient needs a fan, but you should have someone more knowledgeable than me confirm this.

I think that the electric heaters will be a big blow to your HERS rating because HERS does not consider usage patterns.  If you care about the HERS rating, you should remember that it's optimizing to a model and the model is not always accurate or sensible.

For example, adding an attic fan can take a few points off your HERS rating.  Where I live (high desert) an attic fan makes no sense.  Best plan is to open up the house at night, then close it up as the temperature rises during the day.  Blowing out the cold air with an attic fan and replacing it with hot outside air is not a sound cooling strategy.  So, I'll probably install an attic fan and make sure that it can be closed off completely since it won't see any use.

Solar domestic hot water is, so I hear, a good way to lower your HERS rating, and does make sense from an energy standpoint.  There's obviously a cost involved, and, at least at the moment with low natural gas prices, if your planning an energy efficient, tankless, natural gas, water heater then the financial return is probably not there - unless you need the HERS points.

If you care about the HERS rating, for instance if you plan to get a LEED rating, then you might ask the rater for suggestions as to how to lower the rating.

The rater used a 64% efficient water heater in his modeling. I assume if I just bumbed that to an 80% unit, it might lower me to 50 or below. If not, I'll add some insulation to a wall or something...

Do you know anything about the tax credit for houses with low HERS ratings? I understand they introduced sentae bill 1637 in August, whic would extend/expand it to $5000 for HERS ratings of <50.

Thanks,
-m

Check what gives you the best ROI.  I would imagine that a better water heater should be good since it's a year-round activity (and it should actually save you money).  If you're not already, consider tankless.  There really is no logic to keeping 50 gallons of hot water around and 80+% units are relatively common and not too expensive.  Check on an attic fans since I think they  are good and relatively inexpensive (we had an estimated 10 points+ for adding an attic fan).  There are probably other things in the model that will help. 
No, but I'd like to.  Here in NM you can get some good state tax credits for energy efficient homes.  Since ours is a remodel/extension we have to make at least LEED Silver to get the credit (new build is much easier).  It's worth more (close to $10K), but LEED Silver is much harder than HERS < 50, and more expensive.  I'd probably go for easier path and the smaller credit - unless, of course, I can get both.

tankless isn't a slam dunk really. standby losses for water heaters are small, and tankless heaters have significant efficiency loss during short demands. If you don't use much hot water, they can make sense (but then the payback isn't there) or if you need a huge amount of hot water that few tanks can produce. but for most homes, a decently insulated tank heater is just fine.

I live in a early 80's very well insulated home with an open floorplan and "electric heaters" in the back rooms. they needed to run, for sure, and without them running the rooms with them were uncomfortable. It may be possible to skip heat if you don't care about cold rooms, or if you go all the way to passive house building, but if you don't, don't assume you wont need heat in any room you want to be comfortable in.

Yes, but perhaps my "other rooms" will be easier to heat because they will be directly above the main heated area...?

With the money I save up front, I can invest it and use the proceeds to pay the electric bill. I was trying to squeeze the radiant system in for under $4k. With a lot of work on my part, not to mention trying to find a heating guy who would work with me without charging too much etc, I may accomplish this. It just seems like overkill in this small house. I can do a nice european gas space heater downstairs, then maybe a nother small one upstairs, or just baseboard everywhere else, for about $2k. Invest the 2k @ 10% (I can easily get this return) = $16.66/mo or $33.32/mo during the 6-month heating season, which would be way more than I'd actually use to heat those rooms. I currently use an elec space heater to heat a bedroom in the basement, and it only adds about 3KWH/day, or 3 x 30 = 90 x .12 cents = $10/mo. And this basement room only has 2" foam inside, none outside, none under slab etc...

Thanks for the discussion and making me think (for once --ha)
-m

I'm not advocating for radiant. However, in the house I spoke of, the 2nd floor was wide open to the 1st floor. both wing bedrooms up there were not really comfortable, though you might consider it "tolerable". the rear bathroom downstairs was positively cold, though open to the main room through the door of course.

radiant may be overkill, but that doesn't make "no heat" comfortable, that's all.

I think that tankless will always save, but you're right that the saving is lower for higher volumes and may not make economic sense given the higher initial cost. At the minute you can get a tax credit of 30% for installing high efficiency water heaters and only tankless are currently energy star rated.

Bradford White who sell storage water heaters, are even forced to conclude that tankless is more efficient.

I would have suggested this DOE page except that they kinda hurt their credibility with the statement:

For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient

The usage is quoted to two significant figures and the saving barely to one.  ("I want this stud cut precisely to 1/100 th of an inch, somewhere between 8 & 10 feet long")

In my search, I was reminded of a "Combi" boiler.  These are very common in Europe, but I haven't searched for such a thing in the US.  They heat water for both domestic hot water and heating, say radiant hydronic.  Basically, when there's demand for hot water they switch to that function and provide hot water for heating at other times.

Your links just support what I said: you save the most on low levels of usage, where usage would never justify the cost of the install. High levels of usage see significant narrowing of the savings, though for long continuous draws the tankless is still best.

tax credits may distort the economic reality of it, so be it, but ultimately they don't make that much sense for most people. the savings will either be more of a little, or less of a lot. and if you ever need service, all your savings is gone. Unless you are keeping the water heater in very cold space like a garage, I don't see much of a benefit for most people.

Combi boilers are tough to "do right". Typically you either undersize for domestic or oversize for the heat load, but it's very hard to hit both with one burner. this is why indirects are better, they allow a boiler sized for heating to do the (typically higher) domestic load as well, without upsizing your burner.

Personally, I'm not considering tankless for DHW anymore. My usage is quite low. And the thought that the unit has to turn on each time I use hot water would drive me nuts. I do a lot of cooking, so lots of small draws over a half hour or so..
But the main thing for me is very low usage overall. I use about 5 to 10 therms a month in the summer (non-heating), so the payback periiod would be way too long.

-m

I agree.  Although a very efficient storage heater is not much less expensive than a tankless heater.  Unless and until gas goes up in price significantly, there's probably no real ROI on either.  Certainly I don't think that it's worth changing out a working heater unless you have some other motivation.

To me, the physical dimensions of the heater is important. Our storage heater essentially takes a corner out of the kitchen ~3x3 9sq ft.  If you consider that a house is normally ~$100/sq ft. then there's almost $1000 of space that the water heater is occupying.  I think normally this wouldn't matter, the location would be more intelligent, but I'd like that space back in the kitchen.  A tankless can be mounted on the kitchen wall in a "cabinet" (not bottom), or similar small spot.

I also want to put a second heater on the wall of a remote bathroom.  Since the house is long and the current heater is at one end, I don't want to have to wait for the water to heat up and waste the water associated with that.  (A recirculator would slove the water problem but not the gas problem).  This probably doesn't make economic sense, but neither do granite counter-tops, I have to live in the house.

We also want to side-vent the heaters, which you can do with either, but only with the higher-end storage.

Good point on the combi boilers.

For summertime intermittent use you can still do pretty well with a cheap atmospheric-drafted, cheap B-vent, zero-standby no-electricity zero standby, 0.80EF relative cheapie like the Bosch 1600H.  With incoming water temps over 50F they do a decent job of delivering an endless 3.5gpm shower (or two 2.0gpm showers.) 

Aside from the slightly fatter gas plumbing to accommodate the 117KBTU/H max modulation, the installation costs aren't different from a tank heater. (The installation costs would be typically less than an electronic ignition tank heater 'cuz it's ignition is powered by the water flow.)

The minimum modulation is ~30K in, which may take some getting used to (poor temperature control when the hot water is running at a bare dribble, can even flame out), but it's not such a big deal to just run the dribbles faster, as a rule.

The inefficiencies of low draws vary with time between draws.  With bigger-deal power-drafted tankless units it's fairly substantial due to flue-purges robbing heat from the heat exchanger with every cycle, but even then "warm starts" are far more efficient than cold-starts.  With atmospheric-drafted units you don't have flue purges, and the impact of short draws are lower (and the "cold water sandwich" affect is much less pronounced.)  Even if they're all short draws, short-cycling an already warmed up atmospheric unit you still beat average tank efficiencies.  With 5 minutes between draws, even a flue-purging 0.82EF tankless beats 60% efficiency on half-gallon draws.  A non-purging atmospheric tankless would probably beat them on that sort of test.  See Figure 5 in this document:

http://www.energy.ca.gov/title24/2008standards/prerulemaking/documents/2006-05-18_workshop/2006-05-11_GAS_WATER.PDF


If you stick with a tank, there is much room to substantially reduce the standby loss situation.  Insulate ALL near-tank plumbing, including the cold line in and the down-tube for the pressure/temperature safety valve. (To at least 4 feet away on the cold side feed, 8 feet or more on the hot output side.)  Tankless or tank, insulating all of the hot water distribution is a good idea.  Distribution losses account for ~15% of the total hot water energy on average, something that never shows up in an EF test.

PG & E in CA are constantly testing/retesting stuff- here's a synopsis of some of the water heater testing under different use profiles (long/short draws, total volume, etc.):

http://www.aceee.org/conf/08whforum/presentations/1a_davis.pdf

Note just how badly low volume use standby kills typical American-style tanks!  More than half your 5-10 gallon summertime use is standby loss.  It may not be worth spending $1500 more to cut that in half, but when the installed costs are roughly equal...  Even if it's $200-400 more there can be a financial rationale for going with a slightly lower efficiency atmospheric-drafted unit like the 1600H, as long as it meets your hot water needs. (FWIW: I lived with a similar-sized even lower efficiency tankless unit in MA for 15 year and never ran out of hot water.  My late-winter incoming water temps are well below 50F.  I retired it fully-functioning only this year, replaced by an indirect/combi system.)

If you have hard/very-hard water you may need to descale it on an annual basis, but beyond that, the dumber-than-a-box-o'-rox tankless units are pretty low maintenance. (In similar water conditions you'd have to do annual maintenance on a tank too.)

Posted By Dana1 on 11/23/2009 1:05 PM

Aside from the slightly fatter gas plumbing to accommodate the 117KBTU/H max modulation, the installation costs aren't different from a tank heater. (The installation costs would be typically less than an electronic ignition tank heater 'cuz it's ignition is powered by the water flow.)

There are some smaller (1/2 gas input) units available, obviously the capacity is less.  For example, we've just installed a model from Excel America.  They have a atmospheric unit for just over $200:

ExcelAmerica

The units are very basic, no fancy digital display, remote, etc. but the efficiency seems to be pretty good.  The one we installed with the blower is noisy, but seems to work fine - so far.  The blower-less units use D-Cells for ignition so no standing pilot.  It's hard for me to judge the quality but they seem to have a good installed base, including a large number at high altitude in Chile (the units are spec'd to 9200ft).  Traditionally the lower cost tankless heaters have had problems with heat exchangers, but, hopefully that's been resolved for all the current generation of heaters.

Cycling could be an irritant with intermittent use.  Especially with the fan, it's a little disturbing to hear the unit kick in and then out again only a few seconds later.  I don't know the extent to which this hurts efficiencies or life expectancy or whether it's just a perception.