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Thermally Amazing Shell and System
Mike T., Swampeast MO
Member Posts: 6,928
[Just spoke with homeowner--he reviewed message and reminded me that the house was 2,800 sf + basement--not 2,600...]
No, less than 2 btu's sq.ft. at -25F with the initial high setting on the Bradford White.
System temps now 120F - 125F during such weather so rated emitter output is down even further with < 1 btu/hr/sf expected for 80% or so of the heating season.
Once complete, they do plan to keep the ground floor a bit warmer, but as he keeps saying, <B><I>"I haven't even insulated down there [the basement ceiling] yet."</B></I>
No, less than 2 btu's sq.ft. at -25F with the initial high setting on the Bradford White.
System temps now 120F - 125F during such weather so rated emitter output is down even further with < 1 btu/hr/sf expected for 80% or so of the heating season.
Once complete, they do plan to keep the ground floor a bit warmer, but as he keeps saying, <B><I>"I haven't even insulated down there [the basement ceiling] yet."</B></I>
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Comments
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LESS THAN 2 BTU/SF @ -25F OUTSIDE
Extreme N Maine; -20F design.
2,800 sf above ground; 2 full floors plus basement.
Double 2 x 6 shell; R 70 ceiling; good number of "super" windows chosen for orientation. Doubled 1/2" drywall on all exterior and partition walls.
Manual J loss 34 mbh; estimated heat requirement 10 mbh.
Heat source: Bradford-White tank water heater with rated hydronic HX supplying both DHW and space heating.
Homeowner and wife act as contractors and do much of the work. He laid tube, plumber the system. Intentionally simple with a single Taco 006 circulator, differential pressure bypass and TRVs.
I designed the heating system after he made an appeal at the wall for help with this extremely unusual shell. The floors have open web joists to allow warm air floor heat and the inner shell is fully sealed from the outer. When that proved impractical he decided to use hydronics.
About 1,500' of 3/8" pex tube. Notice that all of the pex is insulated and he's even insulating the short space between the manifold and tube guide!
On startup in mid-winter only the 2nd floor emitters are connected with three of them air locked. The ground floor is still being finished so the rads aren't installed.
Only 17' of 6" Myson pedestal baseboard functional in master suite and larger upstairs landing hall. Five of the seven 2nd floor spaces have functioning emitters.
About a week after startup he reports, "I've never had hot water heat and this is great. Upstairs it's 70F, downstairs it's 60F and perfect for working. Basement's a bit warm--60F--but I haven't insulted its ceiling yet. The guest rooms are 60F and the rads don't seem hot but that's not a problem. There's a bit of rushing water sound in some rads. I set the Bradford-White to max (180F) but it never gets that hot and the temps at the heating system are cooler still."
I reviewed the setting of the differential pressure bypass with him and found the scale was in atmosphere (bars) while I'd provided psi.
He set the differential pressure and a few days later reported that the noises were gone and provided the photos.
At the conditions shown in ArtM02.jpg the functioning emitters are rated to deliver only 5 mbh at the available supply temperature.
About two weeks after the photos were taken, he reported finding the suspected air pockets in the 3 non-functioning radiator circuits, the longest (abt 150' of 3/8") in the system.
He says, "[ground floor rads still not installed] The solar gain is fantastic and the performance is amazing. It almost gets hot on sunny days and I've turned the Bradford-White DOWN with 124F system temps in design conditions!!!"
He asked, "How do I stop the system when I don't need heat?"
Reminded him of the specified (but not yet installed) warm-weather shutdown and suggested a setting of 32F. [Yes, I suggested freezing as the shutdown point for the space heating system.]
A few days later and after observation in warmer weather reports that, "I think the shutdown needs to be lower than 32F. Especially when the sun is shining. What can I do?"
[Believe I'll suggest carefully placing the outside temp sensor on the south side of the house. suggestions/comments?]0 -
estimated
less than 2 btu's per sq ft at -20F?
what is it at 20F, -2btu's?
it almost suggests you'll need air conditioning when its 35F outside and sunny???
what do you figure is the solar gain here?0 -
re: Solar Gain estimate
House is very conventional in appearance with no apparent passive solar design measures. Very little glass to both the south and north. Generous but not greatly abundant glass to the east and west. An 8' deep porch overhangs the ground floor windows and surrounds the house on all but the west side.
As I told the homeowner, "It's not so much that you're getting any special solar gain--your shell just traps it so well and looses heat so slowly that even a 'typical' amount seems like a lot."0 -
WOW
This sounds amazing Mike. Even though my house I built a couple of years age is very efficient, it's nothing like that! Maybe the next one!
What are the "super windows" that they put in? Also, probably a dumb question but, how do you set up a differential bypass valve?
Thanks, Rich L0 -
That is excellent.
the detail to insulation is intense *~/:)
THAT wont make the Fuel companies Happy!
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That is excellent.
the detail to insulation is intense *~/:)
THAT wont make the Fuel companies Happy!
R-70 in the lid makes me habby *~/:)
Great job Mike 0 -
Air exchange
Is there an air exchange system? ERV/HRV?0 -
Certainly. I did not specify. Know HRV with three outlets.0 -
Outside Photos
Get ready to be wowed.
His offer includes a "trip to Maine for anyone who can design a system to work in this house."
The backyard photo seems aptly named by the owner. I've never been to "Vacationland" before but I now know why it has the name.
Obviously cold weather arrives before the skin was complete. The "special insulating" siding used over the occupied shell has at least an R-2 value. It's not required on the attic side walls.
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Exterior Photos - some current
Get ready...
The homeowners original offer includes a trip to Maine for anyone who can design a system for this unusual house.
I've never been to "Vacationland" before, but I see why it gets the name.
The non-current photo of the back yard seems aptly named by the owner.0 -
Exterior Photos - some current
Get ready...
The homeowners original offer includes a trip to Maine for anyone who can design a system for this unusual house.
Cold weather obviously arrived before the skin was complete. The siding used over the occupied space is "special insulating siding" with at least and R-2 value. Not needed over the attic space.
ArtM05.jpg is the east side. The two bedrooms with air locked rads are at either side of the top. The open area with functioning rads includes the two center windows. The master suite runs the length of the west wall with heat in all spaces.
I've never been to "Vacationland" before, but I see why it gets the name.
The non-current photo of the back yard seems aptly named by the owner.0 -
The circulator was chosen for about 6' of head at about 4 gpm.
0.15 bar = 2.1 psi required to deliver Manual J design output @ 140 awt through the most remote emitter.
The differential pressure bypass setting establishes the position the circulator will run on its curve and is set to the minimum required give flow through the maximum head loss of any circuit in the TRVd system.
An ECM circulator was considered for its low running cost, but with only an 006 it would have taken decades to recoup the cost--even at his high electric rates.
I anticipated considerable bypass and told the homeowner that I expected that a year-round water heater setting of about 130F would be sufficient.
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Insulation Photos
Of course the partitions are fully insulated. This is the landing hall. There are 2 x 3' baseboards.
Much of the of the loose fill looks like it's been compacted and smoothed by a mason.
Windows set back rather deeply to the outer shell level.0 -
Why insulate the partitions? And do the headers have insul breaks?0 -
Sound control? This is the upstairs with bathrooms. I'm not sure if the ground floor partions are insulated. There are few partition walls down with a large combined entry, living, kitchen and dining with study, laundry and 1/2 bath.
The inner 2 x 6 shell is structural, sheathed and with rigid insulation. An outer insulated 2 x 4 shell with sheating and insulation is applied to the sealed, structural inner.0 -
Where in Maine?
Is this an open system?0 -
Washburn, ME about 20 miles from Edmundston, New Brunswick, Canada. Closed system.0 -
At 1 btu/hr/sf heat requirement @ -20F, the difference between actual performance and assumptions given "high efficiency" design would [seem] to be logarithmic.
The home goes passive on clear days with temps in the teens.
Are there any comparables?0 -
Infiltration
Calculated at 0.2 ach with 10 mbh manual J loss as I was requested to design for some deterioration in the shell performance over its life.
I allowed 2 mbh loss for the HRV system. Perhaps too much?
They're going to have windows cracked when the children, spouses and kids gather at Christmas.
Can it be called a truly passive system when life-required ventilation loss is the only space heating load for more than 70% of the time when nighttime temps below freezing are common 9 months of the year?
Glad I suggested that only compact fluorescents be used due to the potential for overheating in "moderate" weather.0 -
Occupancy Gains
I have not yet asked the homeowner, but assume that the kitchen refrigerator (which I assumed would provide much of the required load in the general area) is not installed.
If so, then it might be fair to say that the refrigerator gain provides a significant offset to the heat recovery ventilation.
"The most efficient heat source is one that doesn't have to run."
The heat source--a tank-style water heater with rated hydronic HX coil supplying both DHW and space heating--is otherwise a conventional gas model with 70% seasonal (my design assumption despite somewhat higher AFUE (80%))) efficiency.
I expect annual heating costs no more than are typically assumed to be lost up the flue of a tank DHW water heater.
Is this a passive home?0 -
jp:
Do you still think that any other heat source would have been suitable?
Last October or so, I believe you suggested that a mod-con--or perhaps Voyager with FAR higher btu input--would better in an earlier thread when I stated that the Bradford-White was the only choice.
What's the efficiency of any emitter?
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why use gas of any kind? just introduces a flue, combustion, etc. for a load that small, electric would be a negligible cost.
kudos to the envelope builder though. that is truly amazing and inspiring.
though for an envelope like that... duct heaters in the IAQ ventilation system might be the most cost effective solution? Your MRT is unlikely to be anything less than room temp, ever, hydronic/radiator or not. Static load calcs and degree day comparisons might not point to that, but I bet if they watch their real energy usage, the negligability would render the advantages of hydronics fairly moot...
This is ALMOST passive. I've heard a lot about passive annual heat storage houses.. if you put up with some swing they are supposed to be completely passive.0 -
Homeowner requested LP due to high cost of electricity. Homeowner specified only LP for domestic hot water.
There's also an 80-gallon whirpool in the master bath.
I suggested electric radiant in the baths, but he had already considered, decided against and tiled the floors.0 -
Rob: The homeowners LOVE the comfort of the hydronics!
Please don't suggest hydronics are inappropriate for the ultimately comfortable and efficient heating system.
I could never in any conscience consider heating a house of this size in this climate via reaheat through the HRV.
When I'm thinking on a log scale, even a slight decline in performance of the shell becomes significant.
In some occasion he might have to crank the output to 5 mbh...
On what scale should "almost" be judged?0 -
Washburn Me
That is where my Gandmother was born, long haul from here though0 -
Perhaps the trick...
... would be to add a few hundred watts worth of photovoltaics to the house, feed that energy back to the grid and then call it a net zero home ;~)
I am beginning to believe we should determine what we want in our own (and clients) homes and build to meet those goals. It's nice to have something to look at for ideas, like LEED, but for example, would the ability to call this a net zero home make it more comfortable in some way?
Regardless, it's a wonderful project and was prolly fun to work on!
Yours, Larry0 -
Did you notice little snow on the roof despite feet on the ground? I'd sort of expected to see lots of snow up there as well.
High prevailing winds from lakeside and 12-12 roof slope.
Homeowner obviously enjoys this and may well consider PV once the interior is complete and funds are available.
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\"prolly fun\" -- but different
Of course it was fun--just like when you showed me the plans for your solar gravity wall radiant system at Wetstock and given your numbers had to say "it should work well".
This was my first paid hydronic engineering job and damn it feels good for this to be it...0 -
The design store is open.
Finest available value with comfort the highest consideration. Renderings, specification and consultation.
Regardless of use, size or scope, the simplicity of design inherent in my work is allowed by perfect engineering.0 -
You can't hit net zero if you use propane
Let's see, if I were this homeowner, I'd really have to ask myself if I would use propane if I built another house like this.
The cost for the propane tank and associated hardware and water heater is several times the cost of a simple electric water heater. Propane costs are approaching electric per delivered BTU in many parts of the country.
There will never be a way to generate propane on your roof.
I'm sure he loves his radiant system, but was it worth a complicated installation of something that hardly ever comes on? He could've heated that house with less than $1000 worth of resistance heaters.
If off-peak rates are available there, using ETS units like those from Steffes.com would make his heating costs LESS than propane.There was an error rendering this rich post.
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electric resistance
Unfortunately, in some markets the cost of electricity is lower than propane when burned in a 80% efficient device.
This is especially the case for low usage accounts which are often charged a much higher rate.
The brad white vents thru pvc not because it has such low stack temps but because it dilutes combustion byproduct with room air, to achieve pvc vent-able temperatures.
I would have some concerns about a combustion device that does not provide make up air in a building envelope that is so tight. Are there any airlets in the house? Panasonic makes these. it's just a one way hole in the wall that permits air entry from the outside when negative air pressures require it.
While your heating loads may by very low DHW is ever present. With all this investment in the building envelope it seems a bit week to use such a low end combustion device.
Are the trvs the only source of indoor feedback? what does the outdoor sensor control? I assume it just shuts off the circ. It's incredible that 32 is the WWSD temp.
I like the home rune 3/8'' arrangement nice and simple, was insulating these lines necessary, I would think of that lost heat as a radiant input as long as it's in proximity to occupied space.
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HRV
"I would have some concerns about a combustion device that does not provide make up air in a building envelope that is so tight. Are there any airlets in the house? Panasonic makes these. it's just a one way hole in the wall that permits air entry from the outside when negative air pressures require it."
Doesn't the HRV account for this out going air? And then does so by first "conditioning" the incoming air stream. At least that seems to be my experience with these units.
Of course you have to give the home owner what the home owner wants, but I also agree with an envelope like this it appears to be a big step back to use the LP gas DWH. LP is definately not as cheap as natural gas which I'm sure isn't available here. However in this application "high efficiency" electric would seem appropriate. With a shell like that it's a shame to have to put a flue through the side of the house and with the flue through the middle of the DWH there has to be greater standby losses than there would be with elec.0 -
hydronics verses electric resistance
With such a low load some talk as to whether or not hydronics is worth the effort.
I think the hydronics choice is the right choice. Owner still has the option to get off petro fuel, and go electric with less capital expendature to change the heat source.
With resistance you are bound to the heat source which the only alternative being how you get your watts...PV,Wind,pooptricity,ect. which require a larger capital investment.
Gordy0 -
HRV are flow-neutral. they exhaust as much as they supply. it is not a makeup air source except for the fact that if you negatively pressurize the house, it is a path for air to be drawn through, perhaps.
atmospheric LP was a mistake here unless the mechanical room is separated from the house and allows its own makeup air, IMHO.0 -
HRV
Rob, I agree completely that the HRV should be a nuetral pressure device and under normal operating conditions is. However I had an experience with a house that was very tight and had no HRV. When the bath fans turned on they would actually pull a reverse flow through the PVC DHW flue! This was the only out door opening (sealed combustion boiler). Of course when the bath fans were on there was usually a shower running, resulting in a call to the water heater equaling problems (stack saftey would open). We added an HRV to address humidity and air quality issues and it wound up providing a path for replacement air for the bath fans when operating. The DHW troubles went away. I understand the HRV isn't necessarily designed to handle a make up air situation but believe from personal experience it works well.
I know all this first hand, it was my previous house! Anyone I speak to about building new I highly recomend an HRV.0 -
that's a fairly extreme amount of negative pressure needed to pull makeup air through lord knows how much 6" duct.
That would not be adequate for most real negative pressure problems (backdrafting) and is definitely not a safe way to handle it.0 -
you're missing the point gordy.
Electricity could be ten times the price of propane; who cares, if it's not coming on 95% of the time, and your comfort is assured either way?0 -
But right now
The homeowner feels propane is the best value. So if they would have put in an emitter that is strictly electric then they are bound to that.
If the system is hydronic they can use what ever fuel/heat source they want, and change when the fuel market dictates the need, with minimal equipment change out. Thats all I'm trying to say.
In this case their domestic hot water use probably out way their heating demands....should be looking to solar to supplement that.
Gordy0 -
don't get it?
No, less than 2 btu's sq.ft. at -25F with the initial high setting on the Bradford White.
how does the "setting" on the water heater effect the heatloss of the house?
if the house has all R70 walls and ceilings, I get 4 btu's/sqft per hour at -25F. 7660btu infiltration and 3750 btus structure. didn't account for basement assumed no loss there.
ADDED:
did you include that "power vented" BW in the ACH calculations? thats the reason I do not like those power vented water heaters.
the pictures suggest fair solar passive gain.0 -
The homeowner is not a heating expert, and needs guideance.
Good point about DHW, though even so, as has been pointed out propane could have been skipped entirely for the home and big bucks saved.. lots of hot water there. Skipping open combustion in a house like this is worth some $$$ in my book as well. going sealed combustion, at least, would be recommended (again, unless the mech room is sealed off with its own makeup air).0
This discussion has been closed.
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