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Birdman
Registered Users
Posts:20
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| 08/27/2008 9:51 AM |
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| I'm new to this forum and an architect - but don't hold that against me. I'm designing a house for myself on Block Island about 12 miles off the coast of Rhode Island. I am looking for some objective feedback on my current (subject to change) strategy for this house.
First the site:
Site is high and dry with silty but not clay soils that drain well. Slope will be away from the house in al direction with option to run foundation drain to daylight. Site is exposed to E & NE winter winds and a bit more sheltered on the W & SW. Fantastic views are to the E and N.
Climate:
Similar to mainland except the water tempers the air temp a bit (about 5-8 F warmer than mainland in winter and about the same cooler in the summer) Wind is an issue - IRC rated 120 MPH wind zone with wind born debris. Climate is very moist - not so much with rain but with very high relative humidity in spring and summer (mildew and mold will grow on just about everything. June and July have fog very common.
Wife:
Patient and loving but has sensitivity to mold, dust, chemicals in general.
Me:
Architect looking to build dream home for near term vacation rentals followed (in about 10 yrs or so) by our use from about April through November (but possibly for year round use). I have extension constuction experience and plan to "GC" this myself with help from local and off-island subs.
i am committed to green building and will be LEED certifying this house - hopefully Platinum but at least Gold. I am a LEED AP.
Island factors:
Wow, where to start! Island has 900 year round residents so no depth to the skills available although there are a few talented trades people here. On island cost of living is very high do to transportation costs, etc. so labor rates are huge. Off-island crews need to be housed at Owner's expense if they stay over to do a project (ferry is 1.2 hours each way and $25RT so "commuting" is also expensive)
This island now has the highest electric rates in the US (generated by diesel) July '08 rate was $0.62/kWh! No natural gas available, propane is very expensive too. The site has good wind resource and I plan to use a wind turbine as well as solar PV and solar thermal.
Concrete is a problem - only one guy makes it on island - can't bring readymix on the boat. Cost is about $190/cy. Mixed in a hopper truck (the "conrete-by-he-yard-type") Sophisticated mixes and admixtures are not his thing.
Goals for the house:
Design will be traditional island look with a bit of fun. Exterior will be white cedar shingles and "traditional" wood trim (fastening to ICF's?) Schematicaly it is a 32' x 28' 2 story box with four successively smaller "boxes" added to the gable end - the last box being only about 5' x 8' and just a shed. The main box and the first attached box will be 2 story, the second and third boxes will be one story and the last box is attached but not living space. The long axis of the house will run E-W, roof will be 10/12. My goal/hope is that with passive solar and active solar (and maybe some non-heat pump geo) the house can go through the whole winter without going below 40F inside and without burning ANYTHING for heat.
Considering:
ICF's for cellar walls and the first floor walls of either the whole house or the main box and first box. I want to use barjoists/meal deck and concrete for the floor decks (first and second) Floors would be concrete with local aggregate (which is beautiful) and then ground and polished. Radiant heat will be in the concrete decks (which will be insulated beneath). For the second floor walls I'm considering SIPS or stick with spray foam or possibly ICF's.
I have about a thousand questions but the keys ones are these:
I know the claims of ICF's providing thermal mass R's of 50+ are bogus, but it still seems in a high wind, fairly moderate temp (rarely below 0F) area the R20-22 plus the tightness seems to be a good choice. SIP make me nervous in such a high moisture environment as when the weather barrier fails (as all things eventually do) the sips will degrade rapidly and be super costly to repair/replace.
Moisture swings are tough here. Is there a chance in conditions where the outside temps swings above and below the inside daily (say in Spring) with a high RH that the inside walls will actually "sweat" With drywall interior finish this would kill my poor wife.Seems ICF have about zero moisture storage capacity.
With a radiant slab I don't like the idea of only having 2" of foam between my "radiator" and the exterior - any way to increas that - maybe a brick shelf on the inside to carry the joist seats?
There will be a porch on E, N, & S of the main box and the floor of the porch will be on grade (concrete? stone?) and flush with the inside floor - this will minimize exposed foundation and avoid steps between inside and outside to make a better flow. (no bugs or thieves here so in summer we leave doors wide open all the time) With shingle finish what is the best way to transition from below grade waterproofing to the 6" to 8" of wall between grade and bottom of the shingle? (I'm thinking stucco).
Whoever has read this far has my thanks! All comments appreciated.
Sam
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hugh jones
Registered Users
Posts:4
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| 08/27/2008 12:45 PM |
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| first of all, nicely detailed letter. Secondly, here we go. After building icf homes in coastal South Carolina I can say that "sweating" on the interior walls won't be a problem. We have two temps here, tolerable and hellfire miserable with high humidity--no sweating or mold yet on mine for last ten years. I would recommend an all icf house but I am biased--live in one and you'll never look back. Being in the south we use very little if any in floor radiant heat along the coast-too long of a heat up for rental properties but like I said we use very little if any here. From the description (size) of your new home, a wood stove insert with circulation fan will heat your house on about five pieces of wood per day if you're allowed to use wood in your area. Otherwise I would look into solar hot water with electric backup for heating. SC doesn't give any type of break on solar, and only electric co-ops here will do any type of buy back plan, so although we have a good climate for it we are relatively soler energy free. As for the transition from grade to siding, stucco, stone, brick or whatever you choosewill work |
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renangle
Registered Users
Posts:91
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| 08/27/2008 1:23 PM |
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Sam,
That was a well detailed post. I understand what you were saying about the R value of the walls being 50 is bogus and architect friend of mine and I got back in forth about it. They really have an "R value" of 26 or so, but when you take into account the thermal attributes and how "tight" the house becomes it operates at an equivalent R 50. I digress, I major problem I see with your house if considering ICF is getting the concrete into the walls. If a ready mix truck can't get there, how are you going to pump the concrete in to the wall. I think ICF would be great for that location, but it would become an extremely difficult builld (I think) if you can't get a pump truck there or at least a trailer pump (and that would be really difficult to work with as welll)!
renangle |
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gregj
Registered Users
Posts:168
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| 08/27/2008 3:11 PM |
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You'll need to understand your concrete supply issues well. How many yards can one hopper truck provide in one trip? Does he have more than one truck? Can he truck in the additional sand, rock and cement and feed it to his truck on site or does he need to head back for more supplies? Based on this info you'll have an idea of where you'll end up with cold joints and whether it is feasible. Can you get a pump truck to the island or a construction crane that can handle a concrete hopper?
Ask around to see what problems others on the island encounter when building and how they dealt with the issues. Any system will work well if properly done or will fail if not done properly. Make sure your contractors really understand the system you choose. With energy costs that high it everything you spend on good insulation and high efficiency such as geothermal will be well worth it |
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Birdman
Registered Users
Posts:20
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| 08/27/2008 3:26 PM |
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| Thanks for the replies.
It is possible to get a pump truck here so that is not an issue (except for $$!!) I'll check with the concrete guy to see how fast he can produce mix - I know he has at least 2 trucks and his pit is less than a mile from the site.
The seating issue still makes me a bit nervous as we don't always have the heat SC does. Last night here it went to 52. In june it can do the same - my fear is that will be enough to drop the temp of the concrete a couple degrees and that will put it below the dewpoint during the following day.
I plan to retain the roof runoff in a 10,000 gallon vault (insulated) - to keep the house above freezing in the winter I hope to use the heat in this vault through a heat exchanger to circ through the floors without bumping the temp up with a heat pump. I may be crazy on this one....
The island power company will sell me power at $.62 but it will buy it back at about half that - no net metering here!! Still, I think producing my own power makes sense.
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MDiver
Registered Users
Posts:28
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| 08/27/2008 9:21 PM |
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If ICF is out of the question for you maybe it is worthconsidering a system like this...
www.polycorecanada.com
I know that this is a Canadian product, but I'm sure there must be a local equivalent, and if not just ship it. |
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gregj
Registered Users
Posts:168
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| 08/28/2008 11:20 AM |
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| If you are primarily using during spring, summer and fall and just trying to keep it above freezing all winter I think you would be best served by a gethermal heat pump using ground loops and forget that 10,000 gallon tank idea. You could size the geo for your A/C needs and add some resistance for use in the event you want to visit in the winter. But check with local HVAC experts as I have no idea what your seasonal demands are like there. If your summer temps regularly plummet at night then the the ICF thermal mass will help a lot to keep A/C costs down. ICF is at it's very best when the day/night temperature swings oscillate above and below the desired house temperature. |
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Birdman
Registered Users
Posts:20
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| 08/28/2008 2:03 PM |
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| At $.62 per kWh there is no way I want to run a compressor or resistance heat - even for a minute. There won't be any AC - no need for it as it's balmy and breezy all summer here. That 62 cents is not a typo! We have the highest electric rate anywhere in the US - five times the mainland - makes wind and solar really attractive.
The water vault will also serve for fire protection (no ponds nearby) and for irrigation of a large vegetable garden and fruit trees so it's multi pupose. Back up heat for a winter vist or possilbe year round use would be propane to heat the hydronic radiant heating in the slab floors. |
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renangle
Registered Users
Posts:91
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| 08/28/2008 2:14 PM |
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Birdman,
With your 10,000 gallon tank would it make sense to place that in the basement of the ICF house? Especially if you are already going to use radiant heating in the slab floors.
renangle |
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gregj
Registered Users
Posts:168
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| 09/03/2008 5:00 PM |
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| I don't see how 10000 gallons of water is going to keep your pipes from freezing unless your highs in the winter are always well above freezing. Be sure to drain and winterize your house every winter so the pipes don't freeze. |
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colinmcc
Registered Users
Posts:5
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| 09/27/2008 3:20 AM |
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You write:" know the claims of ICF's providing thermal mass R's of 50+ are bogus," Why? Although most (all?) of the ICF manufacturers in the USA are indeed only using "2 and a bit" EPS walls, some like Quadlock from Canada offer 4"+ EPS walls which if used inside and outside give R40.. Quadlock are, I'm told, working on a 6" eps wall block which will go way over R40.
I recently immigrated to Canada from the UK where I had been building since 1992 with icf blocks from bicco, who in turn build their blocks under license from isorast http://www.isorast.de/ If you visit their website you'll see that since 1970 they have been offering blocks with 2", 4", 6", 8" and 10" outside eps walls, and 2" inside the 6" and 8" and 10" wall blocks offer U values that when converted to US R values far exceed 50..
So, it seems to me that with all the current energy crisis and heightened awareness of energy costs it is really up to the N American ICF block manufacturers(, with the exception of Quadlock who are definitely heading in the 'right' direction ), to get their heads round the concept of serious insulation, to step up to the plate and start looking at their European counterparts, and start realizing that their highly vaulted R values of 22 while being 'better' than the R of 9 to 11 that so called R19 stud framed buildings actually obtain are still offering only a fraction of what their product promises.
Sorry if this sounds like 'rant' but it really distresses me that in the year 2008 the icf manufacturers I'm researching here seem to be falling down badly and ignoring what could be a quantum leap in building and insulation technology.
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Birdman
Registered Users
Posts:20
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| 09/27/2008 11:36 AM |
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| Colin,
Thanks for the comment. We may be talking about two different things here. It seems you are referring to ICF's in which the additional R value is the direct and lineal result of increasing the thickness of the insulation component (be it EPS or Iso or Poly). I have no quibble with that and in fact was not aware of the European product with unequal walls of insulation. I'll be looking into it.
My comment was not regarding the insulation value of the system as a function of insulation thickness but rather claims made for the contribution of the thermal mass of the concrete. If, for example a manufacturer has an ICF with 2.5" walls and the EPS has an R of 4 per inch then the system R would be 5" of EPS x 4 = 20 (plus some negligable amount for the concrete) In this example some manufacturers claimed a System R of 40 or 50 based on the additional contribution of the "thermal mass" of the concrete. This is the part that is bogus and has been debunked by Building Science Corp. and many others yet some manufacturers still have this claim buried in their literature and web sites.
The thermal mass argument just doesn't work because the mass is buried in the insulation and particuarly because it is buried equally. As heat will flow (via conduction) from areas of higher concentration to those of lower concentation in a heating season heat "stored" in the concrete will flow toward the colder exterior and not back into the heated space as the claims maintained. Since the resistance to flow (insulation) was equal in both directions the unequal temperature differential rules and the heat flows to the colder exterior surface.
The one place where this might work would be a desert setting where on a DAILY basis the exterior temp is above the interior temp during the day and below it at night. In this case the heat flow is almost tidal - reveing direction twice a day.
In the system you describe, say double the insulation thickness on the exterior, the resistence would be less on the interior and so MIGHT allow some heat to travel back into the space BUT this is only the concept - a heat flow analysis would have to be done to account for the variables. The thing to remember is that for heat to flow from the concrete back to the heated space the concrete MUST be warmer than the space (flow is always from more concentration to less) so it begs the question - how does the conrete core get to be warmer than the room temp? - especially with constant heat loss to the exterior thus producing a dropping temperature gradient across the wall.
So, I'm not bashing ICF's at all. I will be buiding my own house with them (in part) so I must be a believer. But the manufacturers do themselves a diservice by making bogus claims. It's a good product with some real pluses and some minuses too. They should just tell it like it is.
And finally, I've see forum rants and your comment was certainly no rant. It was a good and thoughtful comment - thanks.
Sam |
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Jim Miller
Registered Users
Posts:5
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| 09/27/2008 3:09 PM |
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This is a great thermodynamic explanation of heat flow. The benefit of "insulation" is "containment" of the heat and the resistance to outside airflow, except through the desired entrances (Heat recovery). Passive solar design concepts are an example. Heat the interior space during the daylight hours, using thermal mass on the interior as a heat sink, and then benefitting from the heat when the sun sets. The ICF exterior will "help" contain the heat. The ICFs do not themselves contribute to the heating system unless heat is applied through some manner. This is simple thermodynamic physics.
A possible exception to this is a monolithic concrete structure. See http://static.monolithic.com/ for explanations of what happens when all of the insulation is on the outside of a concrete structure. |
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colinmcc
Registered Users
Posts:5
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| 09/27/2008 3:42 PM |
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Hi Sam,
You wrote "Thanks
for the comment. We may be talking about two different things here. It
seems you are referring to ICF's in which the additional R value is the
direct and lineal result of increasing the thickness of the insulation
component (be it EPS or Iso or Poly). I have no quibble with that and
in fact was not aware of the European product with unequal walls of
insulation. I'll be looking into it."
Yes, That's what I was refering to... QuadLock's sytem http://www.quadlock.com/ made here in N America is based on flat pannels of eps, available in 2 thicknesses (2¼" (57mm) and 4¼" (108mm)) They are linked together with High Density Polyethylene ties.
With 2.25 sheet inside and outside R=22 , 4.25 outside and 2.25 inside R=30, 4.25 inside and out R=40. When they bring their 6" thick sheet to market then even heigher results will be possible.
Since arriving in Canada I've been trying to investigate all the icf manufacturers and their product range is the one that stands out most in my estimation.
I've just been bringing myself up to speed at wikipedia on R values, being a Brit I'm more familiar with U-values.. and yes it seems that R values can be expressed in terms of more than just one thing.
I was amused to see this comment there "The U.S. Federal Trade Commission's R-value
Rule generally [b]prohibits calculating R-value per inch of thickness[/b]. (16
C.F.R. 460.20.) The FTC explained the reason for this prohibition:
Since the record demonstrates that R-values are not linear,
advertisements, labels, and other promotional materials that express a
product's thermal resistance in terms of R-value per inch deceive
customers. The FTC further explained that references to the R-value for
a one-inch thickness of the material will encourage consumers to think
that it is appropriate to multiply this figure by the desired number of
inches, as though R-value per inch were constant. (44 Fed Reg. at
50,224 (27 August 1979).)"
Every item I look at in the insulation world here specifies itself somewhere in the literature in R per inch of thickness, and as long as the material composition is constant I can see no reason why the energy 'flow' through it isn't linear so why should multiplying the R value per inch by the material thickness should be so frowned upon.. Obviously if the end material is a composite of varying layers it is a different kettle of fish!
It may be that as one 'passes' futher into the insulation the tempeture gradient between the outside and insulation at that point will vary, so the flow is not actually linear, in which case the FTC rule makes sense. But considering it as a whole, ie fixed temp one side of the block of solid insulation, fixed temp the other side, I'd assume(?) that once an equilibrium was achieved that the temp differential through the block would indeed be linear. Perhaps someone would care to comment?
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