Thermally Amazing Shell and System

jp_2

last october

can't say I remember the details but do remember the discussion.

I would like to look at the heating season load, look at the yearly Domestic load then think about it!

off hand i do see the advantage of a simple water heater here.
though I understand the Knight can modulate down to 10,000.

emitter efficiency:

first we have to agree on the common definition "efficiency"
a brief google search, backs up my common definition of the word.

output/input of system. of course then you can argue whats the system, and how many sub-systems are within the system?

how often has it been discussed here the negative effects of adding carpet to a radiant floor, reducing its output? doesn't this suggest poor efficiency?

if its "all" within the envelope, why insulate any of the piping? why insulate recirc lines? other than summer this should then have zero effects cause it balances with the heat plant of the house.

so I take it, a proper rad cover increased its convection and lowered the return water temp?

since we are on that topic, whats the difference between "efficiency" and "transmission efficiency"? since we are talking about heat transfer here, I see no difference.

Mike T., Swampeast MO

Fuel choice was not an option but the design allows the simple use of anything that can heat water.

There is an existing foundation under most of the house. The basement is the "loosest" part of this incredibly
tight house. There is a large functioning dirt floored root cellar and the door to the outside is just around the corner from the heat source. The HRV has an inlet to the basement.

I offered options for makeup air. Tjernlund termination with fresh air inlet or "hole in the wall" via a PVC inlet with termination.

This is a power vented appliance and can be called "high efficiency" in the conventional world.

jp_2

how can you say this Rob???????

"...propane could have been skipped entirely for the home and big bucks saved.. """""

how can you say this without know energy ratges and needed quantities?

I agree with what Mr bean said about small heatloads and simple cast iron boiler/buffer use oppose to mod/con.

if they want to cook with gas, and clothes dryer, doesn't propane then make sense?

Mike T., Swampeast MO

The "setting" of the water heater doesn't affect the heat loss of the house but it certainly affects the amount of possible emitted energy because it changes the temp available to the emitters. The annotated system photo shows the maximum possible--not actual output.

Perhaps the emitters are giving off significantly more energy than their rating. With so many things affecting the conditions under which an emitter operates, ratings are always relative.

The omitters are hot you know... The house does need some heat.

Unknown

I know energy rates (I'm from maine), but my whole point is that the energy usage here is so small what you use to meet the demand should be a moot point.

I personally would have skipped gas entirely to avoid ANY combustion and combustion by-products in the home. Certainly the stove, maybe not the dryer or heater if they are in a separate, ventilated mechanical space, but personally I would seal that up too and use electric for it all.

Unless you've got six kids or a spa shower, the operating cost differential should be unlikely to ever put a dent in the additional considerations of having to:

-Provide a tank and hook ups for propane
-Provide for makeup air for each combustion appliance
-provide for exhaust for each combustion appliance.

Nix all that, and you're ahead of the game. PERHAPS not if your propane equipment is not electric ignition and you're worried about power outage.. in his area, that might be a big concern. But the heating system still won't operate (maybe stove will though, which is significant).

I'd have opted for a generator backup in that case though.

Mike T., Swampeast MO

The first Bradford-White I specified had balanced combustion but, unfortunately it simply had space heating tappings, not an HX. No balanced combustion model was available for the tank with HX.

The mechanical room is approximately 16' x 12'.

Two exterior walls--one with door to outside. Rest approx 4' above grade.

All four walls of room poured cement. One interior 3' opening with door.

Mike T., Swampeast MO

Ventilation

Can an unconditioned outdoor air sourced be added into the HRV room air supply after its HX?

If so, I can use this to not only provide some net postive ventilation in nearly all outdoor conditions, but also relieve excessive solar and occupancy gains in any but their warmest weather.

jp_2

agreed

i'm not familiar with the utility costs out there.

where I sit I still would recommend propane if that house were down the street, well maybe.......

Unknown

HRV units typically must be in 50 deg + space.

Doug_7

Solar Compensated Outdoor Temperature

Mike - On your suggestion on placing outdoor temperature sensor on the South side of the house:

My outdoor temperature sensor (used for outdoor temperature reset) is in a vertical 4 inch white PVC pipe with a pipe cap on top and sealed at bottom - positioned on roof fully exposed to sun.

Works great - provides up to 8 degrees C higher temperature in bright sunshine, which appropriately compensates for solar gain.

Mike T., Swampeast MO

Very interesting Doug. Thank you.

Constantin

Hmm...

... I happen to like to cook on gas. Our dryer also runs on gas. That's it for gas consumption. Trouble is, if you're on NG, the minimum charges ($7) make those 3-4 therms a month pretty spendy. A LP Tank would last for a very long time here... but I've been told that most towns around here have made them illegal to avoid conflicts with the local monopoly.

Anyway, as far as water heaters go, I'm surprised that they didn't consider the vertex. Same number of moving parts as the BW, condensing, tappings for a FPHX, cooler exhaust temp. Plus, a 76kBTU input and 50 gallon tank for those long soaks in the tub.

Unknown

a lot of people like to cook on gas. a lot of people like to burn candles too (air quality nightmare), have huge window walls, and do lots of things that are less than ideal for a lot of reasons.

I'm not debating that. I'm saying if I built an airtight house, I wouldn't be burning stuff in it without makeup air

Mike T., Swampeast MO

What about deep snow? I didn't see much on the roof in the photo, but don't know if it's always that way.

Constantin

Hi Rob,

No argument out of me, an ideal house would have dedicated intakes and exhausts for all appliances that have a flue. For example, I'm surprised that no clothes dryer offers such an intake as an option.

My only point re: using Propane was that at least with a propane tank I would have control over the fill cycles, etc. and not get penalized for being a low-volume user. Fixed charges are lovely for utilities since they discourage homeowners from using multiple fuels. But I can see the accounting sense in setting them up initially.

Doug_7

Solar Compensated Sensor and Deep Snow

Housing is a 4 inch PVC pipe about 15 inches long, mounted vertically. Snow can pile up on top of the sensor if it wants, but the sides of the PVC pipe shed snow.

The sensor sees early morning sun after sunrise on the side of the PVC pipe. Much like the sun shining on the walls and windows of the house. By noon the sun is shining more straight down.

The sensor sees the sun in the morning and says - It is going to get hot so lets reduce the heat or shut it off.

The sensor also sees dark sky radiation at night and will run a few degrees cooler than actual air temperature.

PVC is a poor conductor of heat which stabilizes the temperature measurement when the sun goes behind a cloud.

Used several years - works great. In my opinion the sensor must see a combination of conduction and radiation - just like the house or building does.

Doug

jp_2

my cooking

for a single person, I used about 1lb of propane a month.

I really don;t worry about the little bit of by-product, I probably breath more crap when I use the snowblower or chainsaw.

Mike Dunn

side tappings

I have used those side tappings to heat the radiant side. I install a plate type HX and pump between the WH and the HX on the potable side and use the other side of the HX for the radiant load. Works great.

Mike T., Swampeast MO

Thanks again Doug. Very nice.

Had specified a mechanical control with sensing bulb/cap tube to avoid introducing electric control but will suggest to the homeowner who saying, "I like gadgets" was a bit disappointed with the simplicity of the heating system. Wiring to the sensor may be a significant issue.

Doug_7

Sensor Control

I have used a 24 volt tekmar 150 or 152 setpoint control with the outdoor sensor inside the 4 inch PVC pipe. Can adjust the tekmar setpoints very accurately to 1 degree accuracy.

Can control whatever you want with the tekmar 150/152 output.

I used white PVC pipe which gives about the right amount of solar compensation. Grey or black PVC would presumably give too much radiant compensation. I chose 4 inch pipe to give some air space to stabilize the internal temperature. The PVC pipe sort of models a building and picks up solar radiation from East, South or West.

A second tekmar sensor in the same sensor housing turns ON air conditioning through the first stage of another tekmar 152. A wall structural heat sensor hooked to the second stage of the tekmar 152 turn OFF the air conditioning.

This is a multi-family building which needs automatic control of when the heating and cooling equipment runs. Shutting down heating and cooling equipment saves lots of money in a multi-family building.

Doug

Steve Ebels_3

Nice Mike

With a heat load that small, the place could probably be heated with solar powered hydronics and an adequately sized storage tank.

Again, nice work!

Mike T., Swampeast MO

Control looks ideal. Won't UV yellow then kill white PVC?

Mike T., Swampeast MO

Thanks Steve.

When all the rads are installed and construction (with associated tool, light, body, etc. heat gone) complete with house at 70F (intended setting) the load will probably increase a bit.

An incandescent work light meets the -20F heat requirement in many rooms.

[Deleted User]

repeated deleted

[Deleted User]

if you haven't already,

check out james kachadorian's, 'the passive solar house'. he's a vermont native i believe. trombe wall, you name it, he covers it. he has one design that uses a water heater, in it's own 'mech' room, to heat a coil for forced air

and again, check out the century fireplace furnace. no matter what the elec, lp or nat boys do, i always have heat in exchange for some excercise. or if i choose, i pay a someone to excercise for me. anyway you look at it, it's the least expensive way to go. and many in this area have outdoor, wood-fired boilers

Doug_7

White PVC

I expect PVC has UV stabilizer. No problem with white PVC in sun after 4 years. If it does degrade I expect the surface layer will turn white not yellow.

jp_2

no reply mike?

Rich L.

Yellowing

Actually Mike looking around town most vent stacks on houses built in the last 25-30 years are white PVC and I don't see obvious signs of yellowing. That is a neat idea Doug.

Big Will

Confused

Sorry But the only thing that throws me is the AFUE of the water heater. I have used the combi core 2 before its great for low load aplications. The thing is I have always been told that the AFUE on the water heaters power vent or natural draft is terible. Around 54%. The energy factor for that water heater is .54 . The recovery factor is 80% but my understanding is that refers to a cold start. Am I way of on this are tank water heaters more effeciant that I have always thought. Tell me I am missing somthing. Also thats a amazing project. Just being involved with that is somthing to talk about. Regardless of what you use to heat it how many of us can say we have been involved in a house that effeciant. I really hope to build my own project like that some day. Kudos to you Mike.

Larry Weingarten

Perhaps I can...

... help answer some of your question. Energy factor is a standardized test that essentially is only useful in comparing similar heaters, sort of like a miles per gallon test. Your mileage will vary. It is not much like real life. Energy factors of good atmospheric, small heaters can be .60 to .62, roughly. GAMA produces a booklet of ratings. EF is a percentage of how much energy in the gas or energy supply actually is converted to heat coming out the hot water outlet. I'm unsure about "recovery factor". There is "combustion efficiency" which usually is more like 80%. It's why tankless are thought to be better energy-wise than tank-type heaters. A step above both is condensing. Of course, there is so much equipment out there that blanket statements and rules of thumb cannot fit everything.

I do agree, Mike's involved in a REALLY interesting project! There probably are many good lessons there. When there has been time to collect data, I'd like to see total energy use as BTU per square foot per year. Could beat Passive House standards.

Yours, Larry

Rich L.

Diminishing returns

Mike did they give any hints to cost per square foot for construction of this super insulated home? 1-2 btu/ft is amazing and I'm sure there will be a nice payback but I'm curious at what upfront costs....

Thanks, Rich L

scott markle_2

re: diminishing returns

Rich,

The very phrase came to mind today as I passingly thought about this house.

I'm often bothered by the lack of "holistic" thinking that sometimes effects projects like this. There is a very real environmental cost to building like this that will take some serious time to payback. One obvious issue is that the ratio of the structures exterior footprint to conditioned space is adversely effected by walls over 12'' thick walls. I'm a big advocate for building envelope investment, it just makes sense. Clearly though there is a threshold at which these investments begin to yield diminishing returns.

Energy markets will largely determine the what this line is, unfortunately these markets are uncertain at best. I'm a believer that intuition can be a good guide in these maters and that projecting various spreadsheet calculations is an unnecessary, and when it comes to calculating embodied energy costs a very difficult exercise.

My guess is that once a heating load has dropped significantly below the DHW load we might be crossing that line. Seems to me that the investment required to go significantly below that DHW load for heating could be better applied to solar DHW hardware.

Gordy

Threshold

One thing is certain energy will always be in an upward trend with some subtle declines along the way.

If one wants x amount of square footage then they have to allow for wall thickness in the planning. Yes it increases the foot print. The only way to get away from that is better insulation than what is out there today.

I think the threshold is a zero energy (fossil fuel dependent) home, with some sort of solar making up the difference anything above that zero threshold including DHW.

Gordy

Larry Weingarten

Average cost...

... of new housing around here (central California) starts around $250 per foot. I built a SIPS home, off grid, for about $100 per foot. I did do a lot of the labor myself. But, I just want to challenge the assumption that efficient must cost more. In commercial work, it's been demonstrated that a good shell will lower the cost below conventional construction because it reduces the heating/cooling equipment needed. That hurdle is higher in residential, but with a good enough shell, we're seeing the ability to eliminate conventional heating/cooling equipment and the distribution systems, saving space and dollars.

You're right that it's a bit silly to focus too tightly on energy performance. "House as a system" thinking is essential or you might build an efficient box that will slowly poison you or your client. The real trick is going to be converting existing housing to be far more efficient than it is now. That challenge makes efficient new construction a cake walk :~)

Yours, Larry

Steve_175

Hey Larry speaking of eliminating HVAC with a high performance shell:

http://www.inhabitat.com/2007/12/10/building-modelled-on-termites-eastgate-centre-in-zimbabwe/#more-7578

Mike T., Swampeast MO

The second shell added 3.5% to the footprint compared to single 2 x 6 construction.

Mike T., Swampeast MO

Since HO and wife are contractors and some barnraising style parties have been held, cost per sq.ft. would be almost meaningless.

HO mentioned "added" insulation costs of about that of the heat source.

Mike T., Swampeast MO

You're right--was thinking of grey UV stabilized required for outdoor electric.

[Deleted User]

how silly!

hiring termites

Mike T., Swampeast MO

Considered a plate HX but really liked the very low head HX inside the Combi model as it allows use of the full tank volume and guaranteed no more than 1 space heating cycle per hour @ Manual J output @ 170F average water temp.

Same should happen with the FPHX, but it would require an additional circulator and the added head on the emitter side would have likely have required a larger circulator there as well.

While any heat source can be used with this system, but its extremely low and slow nature make it highly suited to either direct connection to a tank or via a HX of the style in the Bradford-White Combi.

Oh what I would have done for a model that also included a bottom HX for alternate heat sources.

At the loads experienced, I can store nearly 8 1/2 hours of design load heat in the Bradford-White (72 gal) @ 40F delta-t.

A few square meters of evacuated tubes and wow!