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Posted this message in someone elses thread and got little response. Appreciate your opinions.
Building house on shores of upper Lake Mich. Sustained icy winds in the winter and cool breezes in the summer. Few week’s of AC. Basement (partially walkout) is ICF, first floor 2×6 frame with Vinyl siding, 15LB felf, 5/8 cdx, 1 in greenboard, 2×6 cavity filled with wet cellulose. Haven’t decided on interior vapor barrier between cellulose and drywall. Third plane between upper wall and ceiling about 5′ length with T&G because I couldn’t put in raised hip. Third plane will allow 12″ insulation right to wall. Windows are Hurd Monument vinyl with TC88 glazing.
Basement floor (including garages) have wirsbo tubing and planning on Wirsbo in gypcrete on 1st floor. Plan for heat source is closed loop geothermal (maybe Synergy 3 by WaterFurnace) but haven’t yet figured out how to move air. Maybe air exchangers. Being told by one HVAC contractor that my insulation is good enough that I won’t need spare electric toasters. Another is not so sure, but both tell me not to worry about horror stories. Today’s equipment is supposed to keep a place like mine comfortable and do it cheaply. Will get ref’s and will check them out, but have been really impressed with posts in this section so looking for input and education. Does my weather make this impossible even though I’ve insulated the heck out of this place? Don’t have gas to sight and don’t want a tank.
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Assuming that air leaks are under control, then to me, heating is primarily an equation of btu/h gained v btu/h lost. First you have to make sure that for a given temperature, you're producing more than you're losing, or else you'll get colder. That takes a belief in the production capacity of a unit, plus an accurate assessment of the house's heat loss. For capacity of geothermals, the heat pump is part of the equation, but another part is the way the ground loop is buried. For example, we theorized here that as the winter went on, we'd have a progressively harder time extracting heat as the temp of the ground got progressively higher from the colder water being circulated 800' down there. (David Thomas, is there a formal name for this? Saturation?) You measure this by temperature differentials coming in v going out at a given pump speed. Turns out our efficiency stayed constant, and leads us to theorize that an underground water flow keeps the soil temps constant despite our yanking out its heat all winter. Summary, once you account for extraneous things like weird drafts and potential lessening capacity of a ground loop toward the end of winter, it's a rather simple equation of getting enough capacity to exceed your heat losses at your design temperature. Ground-source, air-source pumps, boilers, etc can be all configured to produce the quantity of heat you'll need.
The second part of heating comfort is distributing that heat wherever you want it. Since you have Wirsbo stuff, they should spec placement and requirements to allow you to reach and maintain your desired room temps.
One thing that complicates the decisions is solar gain. For us, it makes a huge difference in the operation of the system on a sunny v cloudy day. Know your site and how much sun reaches the house and windows.
So, without a heat loss analysis, there's a lot of guesswork. With one, decisions are somewhat easier to make. I don't see any reason at all why a ground-source/RFH system can't work, as long as it's accurately specified. Other systems could certainly also work. Each system has cost and comfort implications.
*Thanks for the response, never thought about cooling the ground over the course of a winter. Don't really have a Wirsbo connection. A contractor many miles away sold me the tubing and I installed it myself under the slab. Looking for an experienced Geothermal guy but my place is so far in the backwoods can't seen to find anyone close who has done more than a few. That scares me, since service after might be needed. No Solar gain in the winter. Pine trees abound and nestled into a natural bowl with hills to the south just high enough to block winter sun. Opening is due west and NW where the winds come off the lake. What about air movement in winter and summer time A/C? Will Air Exchangers do the trick?Any knowledge of good HVAC guys that would take plans and do a heat loss study and make recomendations for a consulting fee? Would use that in conjuntion with a local bid.
*Cloud: The mathematics gets complicated quickly, but in the absence of groundwater flow, yes, the area around your vertical well would cool down during the winter. Post your submerged depth (total depth minus depth to water) and average BTU/hour load and I'll do the calcs. It is similar to pumping water from a well. Initially, you can get a higher flow rate at a higher head (less pumping work). As the well and surrounding saturated soils are dewatered, the max flow decreases and the pumped height increases. The graph of water height would develop over time just like a graph of temperature versus distance from the well.If you also run the unit as an air conditioner, then you'll be putting heat back in during the summer. In Bick's climate (or mine) that is an insignificant contribution. But in Reno, there's a long hot summer AND a long cold winter. They'd help balance each other.You may be right that a groundwater flow keeps your well at a constant temp despite winter-time heat extraction. Groundwater flows can range from 0.01 to 10 feet per day. But sight unseen, 1 foot per day is a reasonable number to pull out of the hat. Steep topology and high rainfall make for faster GW flows.But 800 feet is a deep well. If your house is pretty tight, the well may be a big enough heat sink that temperatures aren't lowered much through the year. A vadose (above the water table) loop is more suseptible to winter cooling. No water (just soil moisture) with it's large heat capacity and certainly no GW flow. And potentially shallow enough to get cold from winter surface cooling (city water mains can freeze at 14 feet deep in my town and we're in the banana belt compared to Fairbanks). -David
*Bick:"Don't really have a Wirsbo connection." They've got some good literature on design and installation. A plumbing supply house or Wirsbo ought to be able to provide that for you. Some plumbing supply houses get all uppity about non-plumbers doing radiant. Just take your business elsewhere. I don't give them flack about engineering systems without being a PE. Perhaps believing that only one's own in-laws can plumb a house properly is one of those little penis / big ego things."What about air movement in winter and summer time A/C? Will Air Exchangers do the trick?" Are you asking about keeping the house air fresh through the year? My house is so tight (0.07 air changes per hour), I definitely need a heat recovery ventilator (HRV). In milder climates, you can just crank a window. But -20F air coming in the house kills the house plants and is quite noticeable when you walk past.Since the HRV needs inlet and exhaust ductwork it can make sense to combine it with a central A/C. If your A/C need is small, maybe one or two room-sized units would suffice. My HRV (no A/C) was about $1000 plus $1000 labor and materials to install the ductwork. -David
*David, thanks for the feedback. Glad to see I listened fairly well when our expert explained stuff to me for the third time. (First two were waaaaaaaaay over my head.)The thing I don't know is submerged depth. We assumed no water, so this is a bonus. We _did_ figure on the summer A/C "reloading" the ground. The quick story is that I wanted to drink well water rather than city water. There was exactly one spot on our site to drill (drilling rig on 30-45 degree slope lot = disaster) and it literally took the rig a 30-point turn to position itself for that. 805' later we had 1/2 gal per minute. So much for water, and I whined to my HVAC contractor and friend about sunk money. He said, "Geothermal." I said, what's that. Long education and some good stories later (know how fast a weighted 805' of pipe shoots down a hole????), here we are, and I was damn lucky the depth was close enough to our heating/cooling needs. I suspect the water level is higher than first thought be/c we were in a drought and be/c of things we observed as we backfilled. (It was fun dropping rocks and golf balls down there to measure the time/distance to water.) Anyway, our unit is rated for 4.5 ton, and last year we measured be/t 5 and 5.25 (ok, x 12000 for btu/h, right?) in both Dec and Feb.Freeze at 14'??? Oh my god! Glad my visit there was in summer!Jim
*Could: Most groundwater flow is essentially horizontal. Yours may be vertical. Not naturally vertical, but vertical because you installed a well. You may have drilled through a water-bearing zone that was perched on top of a clay/silt layer. Water would enter the well screen at that location (as well as cascade down the sand pack) and then percolate into deeper soils towards the bottom of the well. A 1/2 gpm might be the rate at which the perched water pours in. Or it may be difference between the infiltration of perched water less the exfiltration at the bottom of the water. Got a microphone on a 800' cord? Sometimes you can hear the water falling. It certainly could explain the constant temperature within the well. And possibly the lack of change from a drought (lower flow of perched water, but not a drop in water level at the bottom). Or maybe you've got a hundred feet or more of saturated formation (below the water table) of well down there. Did it dewater at 1/2 gpm? That a pretty low flow and suggests a tight formation (i.e. not a high groundwater velocity). Was it rock or soil they were drilling through? -David
*It was rock almost all of the way, with just a couple of small, easy pockets (soil?) at 400' and somewhere lower than that. I'm guessing that the drilling temporarily "cauterized" the underground water flow at that point, they did their estimate of essentially no well water, and over the course of the next days/weeks, the sandy areas unplugged and we got better flow. By that time committed to geo. All this was guesswork based on the way water flows down the mountain be/t chunks of the granite, and there's no way to verify or not now. The lucky outcome, of course, is that we're getting more than the rated output from the heat pump.Gotta share a story. Had to send two 800' lengths of pipe down the well. Our expert tied them to rebar w/ duct tape, and started feeding it down the well. Slow going, even after filling them with water. Couldn't get beyond 530' despite all of our muscling it down there. Expert leaves for day, with opinion that the well filled with soil from the pipe scraping it and that's that. We face decision of trenching the remaining 300' or so. By pure coincidence, a steel erector and crane are on site. He says not so fast. He was evesdropping and thought we might not have straightened the end of the pipe enough. Offers to haul the tube out of the well. What the hell. Next am, we pull it out 50' at a time (probably 500+ lbs) and manage to not kink it. The end 20 ft has about a 12" curve to it, for a 6" well opening. So I suggest welding angle iron to 2 #6 bars and wiring that to the pipe. We drag the 800' of pipe up the mountain to make the slide easier (that sucked!). Then we raise the end, position it over the well, and let go. It took off like a bat out of hell. Probably 10ft a second. Three people--me with gloves and two with chokers--couldn't control it. It ripped the gloves off my hands. Crane had to lift w/ a choker to stop it. Went all the way to the bottom in nothing flat--well, about 790', where it bobbed like a bob on a fish line. That was quite the experience--still gets my heart racing! Scary, but worked out fine. Deep wells present interesting problems, and my contractor hadn't had one this deep before.
*Bick,Any luck on finding an HVAC guy to run loads for you? Where exactly is the house to be built? I am not offering my services, but that is what I do for a living (in N Illinois). You should be able to find someone in your area. To run block loads (as opposed to room by room) for a house should take an experienced individual an hour or 2, if you have the details. The going rate for engineering time here is $70-100/hour. An individual working "on the side" would probably charge you less. The details you need: window specs-shading coefficient and U value, wall construction details, roof construction details, possibly floor construction details, orientation and lot layout, color of roof and walls.
*Thanks for the responses. Should take me a week or so to understand your message to Cloud, but I’ll study it. Yes and A/C see note below. . Like you, won’t be able to crack windows in winter. Will need to do some research on HRV.(Tried to insert a bitmap image of floor plan but haven't got that fiurged out yet.)Summer A/C requirements present a dilemma. Probably only need it for one or two weeks per summer, but those weeks will probably be when aging relatives are visiting. Want a plan that includes some sort of cooling capability, at least for BR bedrooms. Window units: Because of strong winter winds, sand blasting effect (right on the dunes) etc. went with Hurd vinyl casements all the way around. Have never seen window units designed for casements. Because money has gotten in the way will probably leave main floor walls uncovered for a few years, so I will have time to decide on some A/C venting but was hoping to minimize. It is the smaller circle that has interior walls that presents some circulation problems. Circular design of both units makes routing through floor trusses (basement overhead) a real pain. Also, one side of the connector used lamb beams so I’ve only got one way to connect the two circles and it is getting filled up (with wiring & supply plumbing). One guy suggested the Air Exchangers that hang on an interior/exterior wall but vent to the outside. He suggested one for the main circle and one for the smaller circle, then use fans. Have not researched Air Exchangers yet.Soil Conditions: All Sand. House well was 62’ 18 sand, 22 sand and stones, 22 sand. My bet is the sand goes well beyond that. One estimate called for 6 bores @ 141’ each. Thanks for the comment about plumbing houses and non plumbers. Am real sensitive to that and appreciate the help I’ve been getting on this site. Have no real construction experience other than kid going to school doing concrete, iron foundry, steel mill and that sort of thing. Haven’t worked with hands (except a deck) since then. Subbed out the ICF basement but worked as a laborer for the sub. Glad I was there. Did the same with framer. Glad I was there. By the time this 10 year project is done I might develop a skill or two, but want the professionals there doing some things. This HVAC stuff is a bit complicated, but I'm getting there, with a little help from you guys.
*Thanks, not yet. There are very few in the area and have been doing web searches. I know of a couple but would like some third party validation. One of them sold me the Wirsbo tubing at about 4 times what I could have bought if for had I been more educated at the time. Needless to say if I end up using him, I'll want some third party input. Have all the info you mentioned and don't have a problem with the rate you mentioned. You said you were not offering your services, but I'm wondering if you'd be interested. I've read many of your posts and would be comfortable with your input.
*Woke up and saw the bottom of the page. Let's see if this works.
*Bick,Can a GSHP heat your home? Yes, but the devil is indeed in the details. Here in upstate NY we have a 4 ton ECONAR unit with forced air installed as a backup to our masonry heater for our 2800 sf + basement home. Like you intend, we used a closed loop system. Our GSHP also supplies all domestic hot water. Here's a few things to consider:1. MUST perform heat loss calc's for your home and balance against capacity of unit. This is not difficult, just tedious. I recommend "The Superinsulated Home Book" by J.D. Ned Nisson & Gautam Ditt. A bit dated, but your library should be able to get it for you. Our HVAC sub(professional right?) wildly miscalculated our needs. Or, . . ., simply wanted a bigger commission from a bigger unit than needed.2. The deeper you dig to place the loop the less seasonal variation in ground temperature you'll see. The above ref. gives some regional "deep ground" temperatures. This should help you figure out the efficiency of your GSHP.3. Our installer didn't understand HVAC duct sizing procedures either. I'm not as familiar w/ Wirsbo.4. Take a look at the International Ground Source Heat Pump Association info and make sure your supplier is trained by them or equal. (http://www.igshpa.okstate.edu/).5. Economics of a GSHP depend on your electric rate compared with your alternatives. When we live in PA, $0.09/kWh predicted a 4-6 year payback. Here in upstate NY @ $0.135/kWh its more a lifestyle choice!In my experience, you need to educate yourself first, because you can't depend on the "experience" of the professional you hire. Glad to reply to any more specific questions.
*>simply wanted a bigger commission from a bigger unit than needed.Or didn't want callbacks from possibly undersizing the unit. I've heard this regarding all types of heating units, not just GSHP.
*bc... i Here in upstate NY @ $0.135/kWh its more a lifestyle choice!High costs mean quick paybacks right... so what are you saying!?MY KW is the same as yours... thanks to Niagara Mohawk... You would think Niagara... meant.... water power... meant... lowest cost in the nation.... Nope... b highest!!!!near the rippoff stream,ajAnd it's totally NYC and Long Island's fault. We upstate subsidize them...or they would be paying $.25/KW!
*Thanks for the post. As luck would have it, the local library has the book on hand, so I'll check it out this weekend. I've got an unusual sequence of materials from outside to inside (vinyl siding, felt, cdx, 1" foamboard, then a 2x6 cavity that will probably have dense pack cellulose after seems are sealed with foam. What I've not been able to figure out is whether to put a barrier behind the drywall and T&G that I'll have on the inside. Perhaps the book will have encountered such a sequence. The dilema is that with the foamboard (and foam before I install cellulose) I should have a pretty good barrier from outside moisture. Since that is the case I'm wondering if I shouldn't do a barrier to protect from inside moisture as well, hoping that the combination will keep the cellulose cavity free of moisture.I know that's a bid of a departure from the subject of the string, but kind of related.
*ajDon't look at my post in the Electric Resistance heating thread unless you want to have a stroke.Bill
*aj first, then bickWhen you figure economics of GSHP, you need to compare it's cost and efficiency with your other options. For example GSHP w/ 300% efficiency & 0.135 / kWh makes generates a certain amount of heat. Oil, propane or gas at 90% eff. & some other cost makes a different amount of heat. Must end up comparing $/Btu, so higher electric costs for GSHP mean a less favorable comparison and a longer payback period. This assumes noone here in upstate NY is crazy enough to heat with electric resistance directly!Bick,If you're still at the stage where you're making some decisions on your wall x-section I'd recommend two more references.1. Canadian Home Builders Association Builders Manual (1995), ISBN 0-86506-054-1.2. http://www.buildingscience.com/housesthatwork/default.htmThe Canadian book is a little more up-to-date, has excellent illustrations and seems pretty comprehensive also. I'll also warn you that poly vapor bariers are a somewhat controversial topic. I wish I'd spent even more time researching this topic before I framed my house. You must consider potential dew point occurence in both summer and winter. Let me know if you have any questions.
*Thanks for the references. Have read thru #2, but not yet been able to see the fine print in the illustrations. My old printer can't print that small, so I'll print it at work. Will get my hands on the Canadian book, thanks again for the referral.I've been introduced to the controversy. Probably have read 500 notes in several threads on the subject. Most all of the decisions have been made except a few. Walls are up, with vinyl siding coming. So from the outside I've got vinyl, felt, cdx, 1"rigid foam in place. The only thing I could do before the siding arrives is to re-felt (been up since last June) or rip it off and use one of the other vapor barriers. Not inclined to do so after reading the threads. I do want to tape up the felt using 3m contractors tape (found that in one of the posts) but haven't been able to figure out exactly what the heck it is. The 3M site doesn't use that terminology. The rest is up for debate but I'm pretty well settled on dense pack cellulose. My reading tells me to build a wall that will survive moisture should the inevitable happen. That's what's got me stumped. The vapor barrier from "outsite to inside" is pretty good. I'll foam the seams of the 1" foamboard so I don't think anything will get from outside past the foam board. I'm can't decide if I should put a vapor barrier behind the drywall and T&G in an attempt to keep the cellulose cavity dry.I've read that drywall done right can provide a pretty good barrier, but my problem is that I've got one extra plane that leaves the vertical wall then connects to the cieling. That 5' (or so) section will be wood. I've also read that T&G or other wood leaks air and moisture like a sieve. Since I'm stuck with the sequence noted above I've been searching high and low to find that sequence used somewhere else to see what they did on the inside. No luck so far, but maybe the Canada book you referred to . Thanks again.
*No vapor barrier on the inside with DP cels. It can then dry to the inside.near the stream,aj
*2 questions 1. Don't know what that means2. Building Science Corp web site promotes concept of "Air Sealing / Air Drywall Approach" where drywall forms the inside air barrier and care is given to careful taping and sealing sheetrock at tops and bottoms to framing with caulk. Also around openings like elec outlets. If I used that approach (without vapor barrier) does it defeat your suggestion to allow it to "dry to the inside" ?Bick
*Dense-packed cellulose. Blown in to wall cavity so densely that air infiltration rates are reduced. As well as providing insualtion. Proponent claim the insulation is more throughly distributed in the cavity and also doesn't degrade over time as much as fiberglass batting.
*Air sealing is for use with fiberglass insulation. DP seals with out the need.near the stream,aj