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Seeking advice regarding designing and building an economical and efficient home on the North Shore of Oahu
Last Post 24 Apr 2012 12:01 AM by gtjp. 27 Replies. |
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SciGuy
New Member
Posts:33
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| 28 Jan 2012 08:43 PM |
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After spending nearly 60 years in the cold snowy northeast my wife and I
are considering buying a lot on the north shore of Oahu and building a
retirement home. Our only daughter has lived in Hawaii many years and we
would like to build a home to share with her and her significant
other. As you can imagine land is very expensive in the area so we're
looking at lots on the order of 3500 to 5000 square feet. It would seem
that building in two stories would make the most sense.
We're
looking for ideas about appropriate construction materials and designs.
Termites are a huge issue in the area. Cooling and humidity control may
be issues with virtually no need for supplemental heat unlike here in
the northeast. Hawaii requires the installation of solar hot water for
all new construction and also has very attractive solar incentives for
photovoltaics that we would love to incorporate from the get go.
So
the upshot, we're looking for your ideas in regards to designs and
materials that would yield a comfortable as well as economical to build
and maintain home in the region. We're considering a home of 1200 to
1600 square feet and would probably wish to build it in a way that half
of it could be easily rented out somewhere down the line when we've
passed on.
Thanks for your ideas and inspirations,
Hugh |
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Dana1
Senior Member
Posts:6991
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| 01 Feb 2012 05:29 PM |
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Moving to paradise, eh? That's gotta be tough to contemplate! In Hawaii's cooling dominated climate designing to limit direct solar gain, and having substantial thermal mass counts for both comfort and efficiency. SABS and SCIP are definitely better at controlling termite migration paths than ICF, and provides more thermal mass than framed structures. (SCIP is higher mass than SABS, sufficiently so that it's worth investigating. Finding an experienced contractor may be an issue.) Concrete or ceramic roofs are also useful for limiting the peak sensible-cooling loads. By having the EPS in the core rather than on the exterior it doesn't provide a tunneling path for termites. Concrete roofs can be done at much lower cost than tiles, but they're also more typhoon-proof. The aesthetics of concrete roof method vary, and may be objectional to some, but if you cover it with photovoltaic panels much of that argument goes away (as does most of your utility costs, if net-metered.) Putting PV on the roof also lowers the direct solar gain, enhancing the benefit of a mass roof. Summertime dew points in Oahu are remarkably similar to the mid-atlantic (think Baltimore or Washington D.C.) averaging in the high-60sF. If you build air-tight and use energy recovery ventilation you can lower that significant but not opressive latent load. Many folks in HI like to let the breezes flow at night, even if it's pretty sticky sometimes but there's no downside to going air tight and having the ability to both cool and dehumidify efficiently. It's probably not too tough to build to a Net Zero Energy standard in that climate, if you have a sun-exposed roof. Since you have zero freeze risk, doing the solar hot water with a SunDrum hybrid approach you can get more return out of a smaller roof area (which could be pretty small with a 1200' 2-story) since the thermal and PV share the same footprint. Ductless mini-split/mult-split technology is probably going to work efficiently at low up-front cost, especially if you have a high mass roof, a relatively open floor plan, and control the solar gains from windows & walls carefully. If you've killed the sensible load sufficiently a mini-split with a "dehumidify" mode would allow you to dehumidify without creating a chill. About half the heat gain through windows can be from reflected light (depends on the reflectivity of what's in the view) so low E even on the north side may be worthwhile. You need not live in a cave- allow for sufficient daylighting in every room, but you don't want any rooms to behave like a solar collector either. Like anywhere else, designing the house to the site-factors, climate, & shading, and MODELING the energy use with tools like DOE2 and/or optimizing it with tools like BeOpt can make a real difference in the ultimate price/performance picture. You don't need high R values to get there, but window performance selection & sizing can be critical. |
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SciGuy
New Member
Posts:33
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| 01 Feb 2012 07:05 PM |
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Dana,
Thank you so much for such a detailed and useful reply. We're currently in purchase related negotiations for a workable lot and are attempting to herd some of the ducks into line before we're too far down the line.
We greatly appreciate your wisdom.
Aloha,
Hugh |
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zehboss
Basic Member
Posts:216
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| 02 Feb 2012 06:25 AM |
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Hugh, You can build a high internal thermal mass, thermal climatic averaged house with nighttime cooling and an ERV system that can bypass at night and thermally exchange during the day. A dehumidification system should be part of the design. No direct solar gain, large overhangs and a cool roof, (radiant based steel). Well ventilate under roof. You should also build out of local bulk materials. An example, volcanic pumas should be readily available and cheap. Pumice is an all-natural, local, sustainable material that provides R-2 per inch and is much cheaper than other available insulation materials. Such a utility free home will save you $100,000 in reduced utilities over the next 30 years.If you are interested in building a low cost, self-cooled, zero energy home at a cost no greater than a custom home in the area contact me at [email protected] and we can help you ideas and or execution. Brian |
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Engineering, Designing, and Building Passive, Net Zero, Self-Heated, Self-Cooled, Self-Electrified, Low Cost Homes
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SciGuy
New Member
Posts:33
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| 02 Feb 2012 10:21 AM |
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Posted By zehboss on 02 Feb 2012 06:25 AM
You should also build out of local bulk materials. An example, volcanic pumas should be readily available and cheap. Pumice is an all-natural, local, sustainable material that provides R-2 per inch and is much cheaper than other available insulation materials.
Brian
Brian, While one might imagine this to be true, in actuality I've seen next to no use of pumice as a building material on Oahu and would hazard a guess that it would be substantially more expensive to obtain and find skilled artisans to work with. The Big Island on the other hand might be a more likely place to obtain pumice as well as people that might work with it. I do appreciate the spirit of your reply. Aloha, Hugh |
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zehboss
Basic Member
Posts:216
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| 02 Feb 2012 09:27 PM |
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Hugh,
In the US most people use materials that are heavily advertised and promoted, manipulation for profit. Materials that are advertised are profitable to package and sell and or have intellectual property from which excess profit can be made.
80% of the world uses natural materials to construct buildings. Natural materials can be purchased in bulk at low cost per ton. The majority of the people in the world cannot afford the additional cost of the heavily manufactured and industrialized materials, therefore they are not used. Natural materials properly used are superior to processed, packaged, and promoted materials in performance, quality, esthetics and cost.
View sire wall homes at http://www.sirewall.com/portfolio/ or some of the homes I have built at http://www.zehtalk.com/.
Your response is evidence of having been manipulated by the Jone's, wish to fit in and the advertising onslaught of the construction industry. Desiring a healthier, more attractive, more energy efficient, less embodied energy, greener, and more sustainable solution the answer is Holistic Integrated Design using Natural Engineered
Systems of the H.I.D.E.N Systems Approach. Contact me if you are interested in learning more.
http://www.zehtalk.com/
Brian
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ICF Solutions
Engineering, Designing, and Building Passive, Net Zero, Self-Heated, Self-Cooled, Self-Electrified, Low Cost Homes
Basic shell starting at R-50 Walls, R-80 Roof structures. for $30/square foot
(360) 529-9339
[email protected] |
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Dana1
Senior Member
Posts:6991
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| 03 Feb 2012 02:48 PM |
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I suspect the real issue for using pumice as insulation would be convincing the local code authorities that it met code for R value, since (like most naturally occurring insulating materials ) the actual R values would vary widely. More "interesting" building methods might be an easier sell in a rural location, but 3500-5000' building lots reads "in town" to me, where there are likely to be more hoops to jump through when going with something considered "exotic" to the local code authorities.
A double-slab wall or double CMU wall (w/concrete filled cores) with a pumice (or perlite) filled cavity between them might fly if you make the cavity deep enough. Sand is often utilized as a termite-barrier, and I imagine that a pumice-sand would be as effective as any. At the very modest wall-R requirements that you'd need in Oahu you might even be able to achieve that with dry sand. For a mass wall code min for Hawaii (US zone 1) is R3 for residential buildings under the Hawaii Model Energy Code, and R0 for commercial buildings. For a studwall (steel or wood-framed) they still call out R13 for cavity insulation.
The Sirewall approach with 4" rigid insulation in the center core is overkill compared to even a 2" core minimalist SCIP, but conceptually they're not too different. The Sirewall would have much more inherent thermal mass, but the performance value of mass drops off pretty rapidly- with rammed earth the considerable extra wall thickness is more about structure than thermal performance. It wouldn't surprise me if you could more than meet the R3 minimum using just pumice or sufficiently aerated lava sands as the material in a rammed earth structure with foot thick walls though.
Whatever the method, it has to fly from an earthquake resiliance point of view too, making it a harder sell too (even though rammed earth methods w/rebar & a higher cement content can be pretty rugged.)
The Building Science Corp folks seem to think that up to R10 whole-wall is cost effective for US zone 1, but that would be only true for low-mass wall construction. (R13 batts cellulose cavity fill in a studwall comes in at ~R10 whole wall, so effectively code-min would meet that.) But they also seem to think that R40 roof work there (again, true for low-mass, maybe not for a concrete roof.) See Table 2, p 10:
http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones
The heat-rejection ability of the roof & wall finishes and management of solar gains will make or break it far more than the absolute R values. A "cool roof" or mass roof will have a greater impact on the peak & average cooling loads than going from code-min to R40 (whole-roof) on the R30 between joists, vented roof or R19 between the rafters. If you literally cover the roof with PV, the PV becomes the shaded-ventilated outer roof. The albedo of PV is much lower than a cool-roof finish, but with any decent roof pitch the natural convection will keep the surface of the roof temp below that of a high-albedo roof. See: http://www.ases.org/papers/227.pdf
A mass roof with R15 continuous insulation (rigid foam or rigid rock wool panels) at the roof deck level would outperform the R19-between rafters low mass roof under any circumstances, and even more so under a full PV shade.
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zehboss
Basic Member
Posts:216
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| 03 Feb 2012 11:59 PM |
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Dana,
Pumice R-factor is easy to determine. There are published tables of pumice R-value as a function of density. Pumice is purchased in different grades which are air content and or density related. There are also standards for pumicecrete which is concrete filled with pumice aggregate. You can look up the standard values. The R-value range for pumice is between 1.75 and 2.25 that I have worked with. It works great for insulating under and around foundations. You can also use it to displace 1/2 of the volume of foam to save money. It will also drain out after a flood and its properties return.
30 inches of pumice under a poured slab is a lot cheaper than R-60 foam in a passive house. Bugs will not hurt it. If ground moisture is an issue it can drain the moisture till it is gone. There are many advantages. In walls, I have developed a method of building contained ballast walls. They have an outer skin which provides the sheer and are filled with ballast. Gravel, pumice, pearlite, non-organic soils, sands, recycled ridged foams, and other materials used to accomplish the desired functions.
High end homes tend to have thick walls. Monticello, Hurst castle, old world castles, the White house, Mt Vernon, and others all have 2 to 4 thick walls. Thick walls provide ability to layer, texture and provide visual interest. It also provides for built-ins, nooks, wide window seats and other custom features. The end product is superior. Straw bale, sandbag, SIRE, rammed earth, adobe, ballast filled, gabion based, and combinations of the above can be integrated where appropriate lowering the cost of the final construction. They also give you more options for low cost high mass and high insulation value walls.
The next benefit is the use of locally sourced, low cost, non-processed, available by the ton, and sometimes recycled materials. This is sustainable and green. These materials provide extra LEED points on several levels, if this concerns you.
Further, high internal mass reduces peak loading in most climates and can thermally average weather effects over days, months, quarters and even annually. This can eliminate the need for AC in the entire continental US. In combination with integrated design of appropriate insulation, windows, solar gain, HRV, proper sealing, ventilation and you can eliminate the need for heating as well.
These methods also allow you to build carbon neutral homes. Standard methods simply cannot get there. If you care about the earth, resources, cost, performance, quality, pollution, maintenance cost, catastrophe survivability, toxic materials elimination, VOCs, air quality, CO2 levels, utility costs, being independent to name a few advantages.
They also provide more flexibility in design. I can build straight, curved or snaked walls in any shape at no additional cost. This opens a whole new world of design options previously not available without a lot of extra costs.
I am obviously a believer, talker and walker of all of this because it works, is better, is lower cost, and is healthier than any other options I know. Philosophically every time I learn of an idea that claims a better outcome I try it, assess it and add it or reject it to the bevy of techniques. I have been doing this for 30 plus years. I can tell you why almost any alternative technique of construction is good, neutral, or a bad idea because I have built one or more of them. I know that if labor is of value in the project then an Earthship is not a great idea. There are more labor hours in filling the tires than it takes to complete an entire standard house. But if the client wants to do that part of the job with their labor then it is reasonable to work with them on the project. I have also developed economical ways to build a building that is not labor intensive and performs better than an Earthship.
Brian
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ICF Solutions
Engineering, Designing, and Building Passive, Net Zero, Self-Heated, Self-Cooled, Self-Electrified, Low Cost Homes
Basic shell starting at R-50 Walls, R-80 Roof structures. for $30/square foot
(360) 529-9339
[email protected] |
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SciGuy
New Member
Posts:33
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| 06 Feb 2012 03:15 PM |
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Posted By zehboss on 03 Feb 2012 11:59 PM
Dana,
Pumice R-factor is easy to determine. There are published tables of pumice R-value as a function of density. Pumice is purchased in different grades which are air content and or density related. There are also standards for pumicecrete which is concrete filled with pumice aggregate. You can look up the standard values. The R-value range for pumice is between 1.75 and 2.25 that I have worked with. It works great for insulating under and around foundations. You can also use it to displace 1/2 of the volume of foam to save money. It will also drain out after a flood and its properties return.
30 inches of pumice under a poured slab is a lot cheaper than R-60 foam in a passive house. Bugs will not hurt it. If ground moisture is an issue it can drain the moisture till it is gone. There are many advantages. In walls, I have developed a method of building contained ballast walls. They have an outer skin which provides the sheer and are filled with ballast. Gravel, pumice, pearlite, non-organic soils, sands, recycled ridged foams, and other materials used to accomplish the desired functions.
High end homes tend to have thick walls. Monticello, Hurst castle, old world castles, the White house, Mt Vernon, and others all have 2 to 4 thick walls. Thick walls provide ability to layer, texture and provide visual interest. It also provides for built-ins, nooks, wide window seats and other custom features. The end product is superior. Straw bale, sandbag, SIRE, rammed earth, adobe, ballast filled, gabion based, and combinations of the above can be integrated where appropriate lowering the cost of the final construction. They also give you more options for low cost high mass and high insulation value walls.
The next benefit is the use of locally sourced, low cost, non-processed, available by the ton, and sometimes recycled materials. This is sustainable and green. These materials provide extra LEED points on several levels, if this concerns you.
Brian,
The land we're considering building on costs between $50 and $100 per square foot. We're talking a cost of well over 2 million dollars per acre. One lot is only 38' wide and that doesn't take into account a 5' setback for the first floor and 7' for a second floor. Do you really think that 2 or 3 foot thick walls make any sense in this situation? It sounds as if your clients have had the luxury of cheap land as well as inexpensive natural resources near by.
I'm certain you would approve of the passive solar geodesic dome home my wife and I designed, built and have lived in for the last 30 years. We incorporated a huge amount of internal mass, Large south facing bead wall insulated windows, radiant floor heat, and a host of other energy saving but inexpensive features. Living in it mortgage free for 30 years allowed us to save enough to consider retiring to a small efficient house in Hawaii.
Thanks again for your thoughts.
Hugh
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Dana1
Senior Member
Posts:6991
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| 06 Feb 2012 05:51 PM |
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Brian: Pumice may have a known R values from standard vendors & densities, but in a climate zone with such low R requirements & codes, I'm skeptical that a local vendor exists or that the inspector would sign off on it. (BTW: Where do I find the tables for R values of pumice by density?) The only assembly requiring a significant R here is the roof, and the absolute R value is perhaps the least important aspect of the wall assemblies.
We're not talking R60 anywhere in this house, least of all sub-slab. With a minimalist mass wall (say, 4-6" of poured concrete) an inch of exterior EPS beats code by 33%. A minimalist SCIP would be quite decent, and a minimalist ICF would be extreme overkill (but would still perform well). It's probably easier to find an ICF contractor than a SCIP builder in HI though. I couldn't find any SCIP contrators on Oahu in a quick internet search, but several ICF and CMU wall builders. Given the number of swimming pool builders and other shot-crete applications I'd think that there's an adequate talent pool for doing a decent job with SCIP, just not the market, yet. SCIPs are available with as thin as 2" EPS (R8) which would be plenty, though 4" cores may be the most common. With 2" shot-crete on both sides of a 2" EPS core, and exterior stucco/interior plaster you'd be looking a a 6.5-7" thick wall, paint to paint.
On the big island there's at least one LEED Platinum SCIP house:
http://www.concretedecor.net/decorativeconcretearticles/vol-11-no-3-april-2011/project-profile-hiilani-ecohouse-kukuihaele-hawaii/
I don't know if any of the people involved could hook you up with a builder in Oahu.
There are rapidly diminishing returns on ever higher mass (even more so than ever higher R)- there's simply no point to going ultra-massive, or super-insulated here. SOME substantial amount of thermal mass definitely counts, but this isn't like passive solar where you need and want to store quite a lot of BTUs to average over a 24 hour period and need a LOT of thermal mass to do that comfortably. It's still designing for minimal solar gain and enhancing air tightness that will make or break it on thermal performance. In this case truly huge mass could act as a band-aid for a less calculated design, but that's not where to go first, and wouldn't sufficiently reduce the average load compared to a better-designed version. This is not a solar house in a heating-dominated climate that demands a large amount of mass to balance the gains & losses of a large amount of glazing.
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zehboss
Basic Member
Posts:216
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| 06 Feb 2012 09:02 PM |
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Dana,
You impress me with your knowledge on standard construction and techniques for energy star plus efficient homes. My sand box is a different one. I do not build standard homes. I only build homes that are passively heated and cooled. Quality carbon neutral at the lowest life cycle cost is the goal. I am a proponent of high internal mass homes made with local sourced materials, because in my 30 plus years of building net-zero, self-heated homes that are no more expensive than a standard home it has proven to be the best way to get there. I am always looking for better ways, but today that is where I am at in my journey.
I do not use loose pumice in an overhead system unless it is under a live roof or in a pumicecrete arch structure. Cellulose is cheap enough not to replace it. I did not sugjest pumice to be the only solution, just something to consider. The point of pumice is that you should consider local materials that are available by the ton at low cost. Pumice is typically $25 a ton, road base is about $7 per ton and waste fill is often free delivered to you lot from a neighbors basement or foundation dig. Using such low cost materials where appropriate can reduce the cost of a construction project dramatically.
In most of the US in cooling dominated environments a 3 foot thick soil based wall system will eliminate the need for an AC system all together. Most people simply do not understand seasonal dynamic thermal modeling. Obviously there is more to it than that but your statement about additional mass in a cooling dominant environment is incorrect. Why do you think adobe homes work well in hot climates?
In thin wall systems, the value of massing is negligible compared to extra insulation. In thick walls, two foot plus and the internal mass becomes more beneficial compared to extra insulation.
I am an engineer and do FEA analysis on such projects on a regular basis. The issue is long time constants that you have to deal with.
The physical properties of pumice are online, heat capacity, conductivity, and mass which allows anyone to calculate the R-values of the specific materials. Engineering handbooks, Wikis and other sources will give you the information you need.
Brian
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ICF Solutions
Engineering, Designing, and Building Passive, Net Zero, Self-Heated, Self-Cooled, Self-Electrified, Low Cost Homes
Basic shell starting at R-50 Walls, R-80 Roof structures. for $30/square foot
(360) 529-9339
[email protected] |
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SciGuy
New Member
Posts:33
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| 07 Feb 2012 06:45 AM |
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Posted By zehboss on 06 Feb 2012 09:02 PM
The point of pumice is that you should consider local materials that are available by the ton at low cost. Pumice is typically $25 a ton, road base is about $7 per ton and waste fill is often free delivered to you lot from a neighbors basement or foundation dig. Using such low cost materials where appropriate can reduce the cost of a construction project dramatically.
In most of the US in cooling dominated environments a 3 foot thick soil based wall system will eliminate the need for an AC system all together. Most people simply do not understand seasonal dynamic thermal modeling. Obviously there is more to it than that but your statement about additional mass in a cooling dominant environment is incorrect. Why do you think adobe homes work well in hot climates?
Brian
Brian, I challenge you to find pumice for anything on the order of $25 per ton on Oahu. You're off by at least a couple of orders of magnitude on that one. I would also contend that adobe homes work well in desert climates that are hot during the day but cool nicely at night so that the average is actually much more reasonable but do not do so well in perpetually warm and humid climates. Our own home with a high mass interior performs wonderfully during the summer with the exception of times when the night time temps and humidity become oppressive for several days in a row. When we return to cooler nights it takes several cool nights to shed the excess heat gained by the mass. Hugh |
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Dana1
Senior Member
Posts:6991
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| 07 Feb 2012 11:36 AM |
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Given that a minimalist SCIP wall (2" EPS core) is already at 267% of code for R value in a mass wall, with that approach there's not much argument for super-mass thick walls. SkiGuy has it rigth- adobe works well in hot climates with high diurnal temperature swings but relatively dry-air & clear nights with radiant cooling of the roof below the ambient air temperature, and comfortable outdoor lows. This is no a description of HI temp & humidity averages. Oahu isn't in a cooling dominated climate, it's a cooling ONLY climate (with single-digit annual base-65 heating degree days even in a cold year.) A totally passive cooling scheme with 3-foot mass walls in HI would mean you'd need to develop a tolerance for interiors north of 80F with interior air dew points in the ~70F range or higher during the peak cooling season.
Of course getting use to that is possible (it helps to wear traditional highly ventilated aboriginal Hawaiian clothing), but it's also possible to hit Net-Nero maintaining high-70s interiors & 50F dew point interior air with PV + mini-splits, and a low-gain/moderate-mass design.
I'n not at all averse to using pumice or pumicecrete, but find zero evidence of local vendors or contractors in HI who sell or use it as insulation. Evidence of SCIP contractors are also lacking, but the number of shot-crete contractors per capita is probably higher than most of the US (outside of swimming-pool rich CA/FL), and it wouldn't be much of a design or method stretch for Oahu contractors. An R40- ish SCIP roof (like the example on the big island) would be the biggest stretch in an all-SCIP approach.
The Hi’ilani EcoHouse makes use of the aerodynamics of the roofline to drive passive ventilation for cooling during the less-hot & drier part of the season which is something I hadn't considered, but that aspect probably isn't adaptable to the higher density neighborhood SciGuy is looking at. It's also completely off-grid, so it wouldn't surprise me if the peak humidity days got to be a bit uncomfortable, without benefit of compressors.
The notion that you could get rid of AC altogether US zone-2 gulf coast simply by going high mass-passive is also a bit of a stretch, given the peak latent loads. Without mechanical dehumidification a mass-only approach would be pretty moldy for the goods inside, with high rates of skin & respiratory fungal infections in the residents. It can work well in TX from the Pecos valley west, and most of the southwest though.
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zehboss
Basic Member
Posts:216
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| 08 Feb 2012 06:14 AM |
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Hugh,
Let’s be real for your case specifically.
I spent a couple minutes studying the Hawaii climate. It is very easy to build a self-cooled home in that climate. One foot thick rammed earth, poured concrete, adobe, or other high internal mass wall with 2 inches of polyurethane insulation and metal external siding in Hawaii will provide dihedral averaging. With only a moderate amount of nighttime ventilation internal temperatures in the mid-70s can be maintained with no HVAC other than HRV ventilation along with the high mass walls. This in conduction with complete sealing, R-60 roof, no solar gain windows, Radiant metal roof, good windows and doors and a desiccant based dehumidification system will self-heat cool and dehumidify in Hawaii. It would also have a long life, earth quake resistance, low maintenance, and almost no energy use for ventilation. The local termites will also not eat such a house.
Hope this is helpful,
Brian
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ICF Solutions
Engineering, Designing, and Building Passive, Net Zero, Self-Heated, Self-Cooled, Self-Electrified, Low Cost Homes
Basic shell starting at R-50 Walls, R-80 Roof structures. for $30/square foot
(360) 529-9339
[email protected] |
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BadgerBoilerMN
Veteran Member
Posts:2010
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| 08 Feb 2012 06:51 AM |
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Oh, that we all lived in Hawaii...
One has to feel sorry for the poor soul who has to face the challenges of being comfortable and ecologically responsible in such a demanding climate. But as usual, Dana can shed light on any construct, no matter how remote or obscure...kudos.
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GTJON
Basic Member
Posts:112
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| 17 Apr 2012 11:51 AM |
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seasonal dynamic thermal modeling
Dana1:
Where's your book ?
Thanks all, though.
When do I see a really practical HW Heater for his deHumidification, hybrid in?
some 30-year old 1-ton R!@ (that's R-12) 'Blue Bombs' are still running, heating HW to near 122
and running (start- 1.1/2gpm) on under 1 gpm, 52 deg water...
What I might ask is why not use those style, though 410a, "chiller" water-heaters as DeHumidifiers when needing HW , just a little more controlled with all the ERV, etc as ECRV (cooling air) or something - with a tiny recirc chiller-DeHum-Fancoil, if ventilating on a cold day, could add heat if rev-cyc ht pump used...
FINAL $ net vs ROI, etc and PERFECT COMFORT and resell-ability, ever?
And what's adding up to ENTIRE CONTRACT of all 'supplements' again
with a GeoThermal (TINY 200-300 ft ECL (gle) horizontal bore into slab with flow-center OEM BUILT-IN as Hydro-Temp.com does- 30x30 pad foot print under 90" high over a HW tank) also for the Cooling, DeHum, ECRV-blowerless, etc (heat and INSTANT HW) and small HW tank under the GT unit if for space-saving-
....?
Le'me see an off the shelf puzzle piece that does all 4 or 5 things and ads resail value possibly higher and a 'CLOSET' quiet central return. Yikes! Can do a miniscule radiant heat to keep bath floor warm while A/C is on... "leather interior payback" somewhat, but now how does 30% taxcredit apply..(to see?)
I have seen so many failures with wanna-heat-HW -that are mounted be on top tank reclaimers, that I am afraid to introduce something that others may appropriately apply , but perhaps misunderstanding H-T 1981 patent.
....JP
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jonr
Senior Member
Posts:5341
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| 18 Apr 2012 07:48 AM |
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Remember that passive internal mass is only effective to the extent that you are willing to let interior temperatures vary. Steady indoor temp = NO benefit to interior thermal mass. Some real disadvantages too. You ran the AC all day at 75F and now it's evening, 80F outside with a nice breeze and you want to open the windows? That's a bad idea with substantial mass (lots of expensive btus will be floating out the window - and you may get sustained condensation on the walls and floors). |
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zehboss
Basic Member
Posts:216
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| 18 Apr 2012 09:07 AM |
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Jonr,
Internal thermal mass leads to more stable indoor temperatures period. No internal mass means heating or cooling against the temperature differential that exists at any moment. This means the internal temperature has to be adjusted with energy input almost all the time. The more internal thermal mass the more weather you can average over. This means that the size of required equipment is down sized because peak needs are eliminated. High thermal mass means long thermal lag. This means you can put in the smallest amount of thermal input possible for the given climate. It requires smart controls that understand the thermal lag in the system and monitor the weather. Assuming the home is designed correctly and controlled correctly internal thermal mass is always better. Many homes have been built incorrectly, for example homes with a thermal lag cannot be controlled with simple air temperature thermostats. This is because the thermal mass temperature needs to be controlled and it will control the air temperature. You will over heat the thermal mass if the controls do not take the thermal lag into account, which would lead to poor temperature regulation. Anyone saying high internal thermal mass homes have poorly regulated temperatures has no experience with properly designed and regulated systems.
The higher the internal thermal mass the more the benefit period.
Brian
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BadgerBoilerMN
Veteran Member
Posts:2010
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| 18 Apr 2012 02:32 PM |
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If you want live in a cave maybe. If you have glass and passive solar gains, the controls get more elaborate, expensive and like thermal mass reach a point of diminishing returns. There are few absolutes in this world though the idea is ideal.
The more perfect the climate the less you need to mess with it. |
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| MA<br>www.badgerboilerservice.com |
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Dana1
Senior Member
Posts:6991
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| 18 Apr 2012 02:56 PM |
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"The more perfect the climate the less you need to mess with it."
... which is why you live in Minnesota? :-) |
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