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sbc62vols

Slab or Crawl-space

sbc62vols
7 years ago

We are in the preconstruction stages of building our farmhouse. My husband is trying to decide on a slab or crawl space foundation. The builder is pushing for slab to save money and for the ease of construction. I am hesitant. I would appreciate any advice.

Comments (73)

  • qbryant
    7 years ago
    last modified: 6 years ago

    Almost all new homes in new Oklahoma are on slabs.
    Just FYI

  • snoonyb
    7 years ago
    last modified: 6 years ago

    Renovator8

    Think they saw you coming?

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  • musicgal
    7 years ago
    last modified: 6 years ago

    qbryant- What is the common hiding place from tornados when the wind comes sweeping down the plains:-)

  • BJ
    7 years ago
    last modified: 6 years ago

    Most new construction and older homes are having storm shelters built underground in the garage. The shelter is relatively flat so there is no issue with parking cars over it when not in use. Another option is to build a "safe-room" at central locations in the house, like a large closet, which is a thick reinforced concrete room with a metal door.

  • musicgal
    7 years ago
    last modified: 6 years ago

    Hi Boomer- yes, we have the latter in our new build... reinforced master closet. Chances of getting hit by a tornado are very low where we live, but we managed to get hit by an F1 in 2003 anyway. So a safe room was a high priority in the new house.
    I saw the metal saferoom compartments that are installed in the garage floor when we were researching for different ideas. Really ingenious.

    This post was edited by musicgal on Thu, Jun 5, 14 at 10:12

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    nini804, I live and build in the southeast and would agree that ventilated crawlspaces are the most popular option but start talking to building science experts or energy auditors and you will find that they are certainly not preferred.

    I expect building codes will eventually require crawlspaces to be sealed and insulated in the future. I think dry climates are better suited to ventilated crawls but humid climates should always go un-ventilated. Thats great and possibly lucky that you never had problems with yours but its possible that you had problems and just didnt realize it. Moist sites are most at risk.

    The more and bigger problems I elude to are my bias of course and why I refer to them as attached caves. They can introduce LOTS of moisture to the home, Radon, and usually represent a significant energy penalty due to air-leaks, inadequate insulation and HVAC ducts that suck or blow air within this problem space.

    As for you sagging joists, wouldnt have happened on a slab. Another point on leaking pipes in the crawlspace. Crawlspaces are terrible places to work and its not surprising that plumbers, HVAC techs and others do substandard work in these locations and they can be very difficult to inspect and maintain. Having a crawlspace invites ductwork while more effort should be spent at keeping ducts inside the conditioned space. With a slab, you are forced to keep ducts out of any attached caves.

  • Lars
    7 years ago
    last modified: 6 years ago

    My sister had huge problems with the concrete slab foundation in the house that she bought in Austin, and she neglected to get my advice before buying. When getting my interior design degree, I was taught never to buy a house with a slab foundation, and I have always had pier and beam with crawl space, which I really appreciate. Slabs can have problems (especially with cracking, due to ground settling, etc) and they are then very expensive to repair. They are cheap up front and expensive ever after, unless you happen to be very lucky.

    At least the OP is getting emails of the follow-ups, but I am also interested in knowing the geography location, since this has a huge influence on how to build. I live in earthquake territory, but I have no danger from tornados or hurricanes here. I used to live in a tsunami zone, but I moved to higher ground, a bit further from the beach.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    I hear similar slab trash talk from time to time. Slabs are the most common form of building foundation in the country which includes residential, commercial and industrial buildings. I also happen to think polished and stained concrete is one of the best floor finishes available.

    I strongly disagree that they are more expensive in the future. Thermal mass benefits, healthier indoor air but most importantly, less air infiltration makes them one of the best choices for on-going energy and health costs. Any expensive problems resulting in needing to fix slabs was probably a result of inadequate design or installation. This message was brought to you by the Portland Cement Association... jk!

  • zkgardner
    7 years ago
    last modified: 6 years ago

    Where we are, in central california most houses are built on slab foundation. From my understanding
    , cracks and such are much to do with the concrete crew that did the pour.

  • renovator8
    7 years ago
    last modified: 6 years ago

    Slabs are common in commercial buildings because of requirements for greater floor loads and non-combustible materials not because they are more comfortable or energy efficient.

    I worked in an old mill building where a concrete topping had been poured over the old floor deck. After the first week I had to buy thick rubber soled shoes because my feet were so bruised I had difficulty walking. The best finish on a slab is wood on sleepers on the concrete. I can't imagine why anyone would want to expose a concrete floor in a living space.

    These foundation preferences are largely regional because the required depth of the perimeter foundation increases greatly from south to north. By the time you get to Canada you have effectively already built a basement.

    The first rule of problem solving is to define the problem so everyone can participate in the solution. This discussion is evidence of what happens when the problem is not defined and everyone volunteers their favorite solution without regard for the actual problem.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    Good points! With commercial I think affordability, durability, and ease of maintenance are other reasons. The same reasons you would expose them in residential spaces. There are few floor finishes as durable and easy to maintain as concrete. Not sure how many quality polished, exposed aggregate or stain jobs you have seen but its not surprising why its one of the fastest growing floor finishes out there. They can be every bit as beautiful as wood or stone and offer an incredible opportunity for the right client and decorative concrete professional.

    For passive solar designs, exposed concrete slabs on grade are the most affordable and effective forms of thermal mass.

    I hear the sore feet argument often but Iam just not quite convinced its an issue. I tend to think its an overblown concern of perception but could be convinced otherwise with some convincing data if anybody knows of any.

    Many if not most of the certified passive haus homes up north seem to be built without basements on raft foundations or frost protected shallow foundations. Just because one is building up north doesnt mean they are stuck with deep excavation. Although I do agree that basements tend to make more sense in walkout situations.

    I think its a great discussion of one the more important decisions facing those building a home. I will jump at any opportunity to talk someone out of building a cave below their home.

  • Oaktown
    7 years ago
    last modified: 6 years ago

    Brian_Knight, it is not just the feet but the knees too. Our current house is partly on slab and partly on crawlspace. I really notice a difference.

  • dekeoboe
    7 years ago
    last modified: 6 years ago

    And the back. Having back problems, including herniated discs, there was no way I was going to have an exposed concrete floor.

  • nini804
    7 years ago
    last modified: 6 years ago

    Just to clarify, Brian_Knight, in the example I posted regarding the fact that our contractor was able to get under the house to reinforce the joists...it wasn't because they were sagging. The house was originally built with carpeting in the family room. For some reason, the builder (production build) ran the joists in a different direction in that room, vs the rest of the downstairs that had HW floors. When we wanted to place HW in that room, we wouldn't have been able to run the floorboards the same direction as the rest of the house unless the joists were running the other way. Since we had a crawl, they could get under there and solve the issue.

    I do agree with you that sealing, insulating, and conditioning the crawl makes for better energy efficiency. It also has cut down on the movement in our HW floors as the seasons change. I imagine our sealed crawlspace is very similar to having a basement foundation. But I stand by my assertation that our previous home with its ventilated crawl space was perfectly fine and definitely dry! There was no mold whatsoever under there. When we sold it, the inspector spent a LOT of time under there...not a single issue on his report about the crawl space.

  • snoonyb
    7 years ago
    last modified: 6 years ago

    While slab foundations may be one of the most prevalent, they as well as thermal mass are area significant

    There use to be a significant number of threads on these boards regarding houses built on slabs which began leaning and employed mud-jacking as a cure mostly post war construction in Texas.

    Oklahoma has large areas subsurface shale.

    There was a community built on slabs on a 90% compacted landfill, which because of the increase weight and density began to subside.

    The entire development was vacated and demoed.

    Housing developments built on the inner bay have post tensioning slabs and essentially float, and actually do very well in earthquakes.

    John Wayne's house was one of those.

    Houses built on mild slope hillsides, slab or stem-wall, will usually have a down slope drag link.

    New developments are built on slabs, because it's cheaper, both in labor and the rapidity of framing to began.

    Building codes require that both attic and underfloor ventilation are maintained.

    There are also insulation requirements for raised foundations, the general term used for a stem-wall, pier and girder floor system.

    There are also stem-wall developments downslope from earthen dams which have mechanical underfloor ventilation.

    Sealing, insulating and ventilating underfloor areas would be another form of the government relieving you of the use of common sense, and then charging you for it.

  • sbc62vols
    Original Author
    7 years ago
    last modified: 6 years ago

    Hello! OP here! Sorry, I was on vacation! We are building in East Tennessee. The site of our home slopes gently on one side of the house. Thanks so much for all the advice. Especially Mr. Knight. You have been very helpful.

  • renovator8
    7 years ago
    last modified: 6 years ago

    "I will jump at any opportunity to talk someone out of building a cave below their home."

    The Kirkman family might offer a different perspective on that issue:

    "We were almost down the stairs when this two-by-four just came through the wall,” said Doug Kirkman. "We were almost down to that landing when that board came through, and he said, ‘what was that’ and I said, 'go, go, go.'" The father and son made it safely down into the basement just as the wind started tearing up their property.

    The design focus on cost efficiency in recent decades has caused many home builders to forget the most important issue: life safety.

    Here is a link that might be useful: storm

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    Youre welcome sbcvols glad something I rambled about proved useful.

    Life safety is another reason that falls in line with slab instead of crawlspace in my opinion. Iam guessing Ren is talking about basements which wasnt really in the OPs considerations but ok maybe it should be. Ive never heard of people taking refuge in a crawlspace.

    When I say cave Iam talking about ventilated crawlspaces. Maybe ventilated crawlspaces are ok in some very dry climates out west but I dont think most folks east of the Mississippi should be building on top of ventilated crawls.

    Nini, not trying to pick on you but even if your crawlspace was dry doesnt mean you didnt have issues. Increased energy use was likely compared to a slab and did you ever do a Radon test?

    According to the American Lung Association, Radon is the 2nd leading cause of lung cancer. Most ventilated crawlspaces do a very poor job of sealing the dirt off which resists radon entry. Sealed and insulated crawlspaces are much more likely to do a better job at this important life safety issue. Of course slabs, in my opinion, are even better which includes basements.

    Here is a link that might be useful: Oak Ridge National Labs fact sheet on sealed and insulated crawlspaces

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    As for the orthopedic concerns: sore feet, knees, back, etc can anyone out there point to some data or evidence that this is a legitimate concern with slabs? I think its possible but Ive just never seen it.

    Comparing old homes with wood framed floors to slabs isnt really fair. If you are building a new home to code then there will be no bounce whatsoever from normal walking. A true wood floor has no give at all. Now some of the engineered options or carpet with padding is entirely different.

    If this is a real concern then you should be wearing shoes with orthopedic insoles on hard surfaces. Ive actually glued orthopedic insoles to my rainbow sandals as Iam no stranger to worn joints. I always wear them in my old house which has wood floors and linoleum framed on very inadequate 2x6s with plenty of "give".

    I would love to set up a blind test that has people walk on concrete vs wood on newly framed floor. I theorize that people would have no idea which is which.

  • nini804
    7 years ago
    last modified: 6 years ago

    Yes, when we sold that home the buyer's inspector did a radon test. I can't remember the actual number, but it was negligible. The buyer's had 2 small children (as did we) and were expecting their 3rd. They were VERY interested in the "health" of the home regarding issues such as mold, etc.

    Honestly, I am surprised you are in TN which couldn't be all that different from NC. High end, custom homes here just aren't built on slabs here. A few entry level production builders may use them, and some condos...but not most and definitely not custom homes. Our custom home builder DOES seal and condition all crawl spaces, but doesn't do slabs.

  • musicgal
    7 years ago
    last modified: 6 years ago

    Brian- lived on slabs for over 45 years as well as taught aerobics for 15 of those years. Some classes on concrete and some on a springy wood floor- man, that thing was fun. You really could fly if you stepped down hard in the sweet spots.
    Ironically, nary an ache or pain in the lower extremities but two shoulder surgeries, so, go figure.
    I think sensitivity to hard surfaces varies from individual to individual. I like the thermal mass of a slab down here on warm days especially. The children will sometimes lie on the bare tile to absorb the "cool". But, we only have a couple months of coldish weather here during the year.
    Most people I know with slabs have a good portion of their home finished in wood and padded carpet, so there is a great deal of mitigation one can accomplish with finishing choices if so desired.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    Exactly. On passive solar homes I recommend people leave the sunlit areas exposed concrete or tile. Doing other floor finishes elsewhere is fine but none of my clients after living with them have bothered that I know of. Most people use area rugs to some degree.

    Nini, I am in western NC and almost all custom homes here have slabs because they are typically done on basements. Custom home sites that dont use basements can go either way but I havent seen a custom builder marketing themselves as green use a ventilated crawlspace around here in a long time. So your custom builder who does only un-vented crawlspaces wont build on a basement?

  • melsouth
    7 years ago
    last modified: 6 years ago

    We're in middle TN. Go Vols :)

    Almost everyone I know who has built here has built a basement if their site will allow it.
    It's probably because tornadoes are so common here.
    Also, our basement has the only rooms in our house that can be nice and cool in summer without running the HVAC.
    We've already had some miserably hot days here this year.

    The new office building I work in is on a slab.
    I don't have enough experience on it yet to complain about it or to praise it.

  • snoonyb
    7 years ago
    last modified: 6 years ago

    "As for the orthopedic concerns: sore feet, knees, back, etc can anyone out there point to some data or evidence that this is a legitimate concern with slabs? I think its possible but Ive just never seen it."

    Just look around.

    Ever noticed the shoes of hospital employees or wondered why, other than sanitation code, why there are wood and rubber mats in the areas where line cooks and bartenders spend their working hours?

    The prevalence of green design, is marginal at best, because of the requirements of architecture, glazing, orientation on the lot and climate zone.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    snooky, I agree that shoes and area rugs or mats are better options for orthopedic concerns.

    That cool feeling you get in a basement compared to upper floors is in part due to the thermal mass benefits of concrete and masonry, benefits shared by slab floors without a basement. Its good to insulate outside of slabs and basement masonry walls to separate them from the thermal mass of the earth which can hurt performance in the heating season.

  • sbc62vols
    Original Author
    7 years ago
    last modified: 6 years ago

    Brian, could you please tell me as much as you can about sealing the crawl space? How exactly is this done? I think you said gravel under poured concrete first. Our builder is older and doesn't know anything but a ventilated crawl space!

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    I will do my best but full disclosure is that Ive never personally done one because of the many reasons Ive outlined above. If you didnt see the ORNL link on June 7th in this thread, that would be a good place for you and your builder to start. If builders seem reluctant, I would take the angle of this being the future of building codes and healthy homes so they might as well jump on board for your project and be better prepared for the future and/or set themselves apart from the competition.

    Ive contributed to one of own pet peeves here by using improper terminology of "ventilated" instead of "vented". They are used interchangeably but I think "vented" is preferred because "ventilated" implies mechanical assistance.

    So for all those out there searching for similar information and subcontractors in their area try these terms: un-vented crawlspaces, crawlspace encapsulation, conditioned crawlspaces and home performance contractors. Increasingly, foundation waterproofing contractors are beginning to offer these services and I saw that Masterdry is a contractor advertising for East TN. Insulation contractors are also jumping into the game and the ones that offer closed cell spray foam are a natural fit for this type of work. I think this approach appeals to most builders because its one less sub to hire and manage.

    I think anyone building a custom home concerned about hidden quality, energy costs, health and comfort should be doing Energystar certification. The third party certifiers can be a great resource for qualified subcontractors as they see the good bad and ugly of work in their area.

    Passive radon mitigation systems are only possible with new construction. Be sure that your contractor is planning for this as its cheap at this stage and should be integrated with the foundation/sealed crawlspace work. Things get more complicated and expensive once things are built. The most recent Fine Homebuilding has a good article on this.

    Gravel layers are usually only included under slabs although I have heard of crawlspaces that use them below the vapor barrier and topped with a thin "rat slab". The gravel layer is one of the reasons I think slabs perform better from both a radon and moisture perspective. I tend to go overkill on this detail running an interior perimeter of perforated PVC that has a vertical stack of solid PVC on the high end and daylights on the low end. This does double duty performance as passive radon mitigation and subslab drainage. I also differ from typical construction by running the vertical stack outside of the slab/exterior walls which avoids the two building envelope penetrations and running all that PVC up through interior walls into the attic/roof. These details are pretty cheap at this stage of the game.

    The details for proper crawlspace encapsulation are probably a little much for this thread but the ORNL link is a good start and I will enclose a good but technical link from the Building Science corporation. There's not much need for you to learn all the proper details if you are doing a good third party certification like Energystar.

    Here is a link that might be useful: BSC Conditioned crawlspaces

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    A better look at that link tells me its not the right fit here unless you really like building science and tech talk. This one is better.

    Here is a link that might be useful: Green Building Advisor: Building Unvented Crawlspaces

  • sbc62vols
    Original Author
    7 years ago
    last modified: 6 years ago

    Thank you so much!

  • renovator8
    7 years ago
    last modified: 6 years ago

    Alternative crawl space ventilation has been allowed by the IRC since 2000 and the earlier CABO code since the mid 80's.

    In Tennessee the proper way to do it is described in the 2009 International Building Code which has been adopted by the state whether or not it is used in your municipality so your contractor should be familiar with it.

    Here is what it says:

    R408.3 Unvented crawl space.
    Ventilation openings in under-floor spaces specified in Sections R408.1 and R408.2 shall not be required where:

    1. Exposed earth is covered with a continuous Class I vapor retarder. Joints of the vapor retarder shall overlap by 6 inches (152 mm) and shall be sealed or taped. The edges of the vapor retarder shall extend at least 6 inches (152 mm) up the stem wall and shall be attached and sealed to the stem wall; and

    2. One of the following is provided for the under-floor space:
    - 2.1. Continuously operated mechanical exhaust ventilation at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7m2) of crawlspace floor area, including an air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
    - 2.2. Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2) of under-floor area, including a return air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
    - 2.3. Plenum in existing structures complying with Section M1601.5, if under-floor space is used as a plenum.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    Not included in the outdated 2009 code are insulation minimums now detailed in the 2012 IECC.

    Zone 4 would require R10 continuous insulation on the interior or exterior of the crawlspace walls. 2" of Closed cell spray foam from the interior is a common application. I would prefer XPS on the exterior but the termite details are admittedly a pain.

  • renovator8
    7 years ago
    last modified: 6 years ago

    2009 codes are not "outdated" if they have not been updated by the state or local municipality.

    However, there is nothing stopping the owner from increasing the insulation of the house to the level they want.

    No one should assume a building code is the best design for a house.

    This post was edited by Renovator8 on Tue, Jun 24, 14 at 17:02

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    Outdated in terms of international code only. Of course what's enforced locally and what you can get away with is anybodies game.

    I feel the current IECC energy codes are already outdated in many ways but generally not levels of insulation. There still might be some cost effective R value increases to be had but not before addressing other things like air-sealing and window performance.

    Un-vented crawlspaces in Zone 4 should absolutely be insulated. This is a particular area of international code performance that is very low hanging fruit.

    This post was edited by Brian_Knight on Tue, Jun 24, 14 at 14:12

  • renovator8
    7 years ago
    last modified: 6 years ago

    Designing a building well should not be equated with meeting the minimum prescriptive insulation requirements from the tables in section R402 of the latest edition of the IECC.

    These insulation amounts are often excessive and intended for smaller buildings or additions where a performance design approach is not worth the effort or beyond the capability of the designer.

    The best method for designing a new home is described in section R405 using simulated energy performance analysis software. A house has a complex envelope and hvac systems of many elements that should not be designed with simplistic "rule of thumb" standards for each element. The design should work as a whole.

    In the IECC, as an alternative to insulating floors over crawl spaces, crawl space walls are permitted to be insulated when the crawl space is not vented to the outside.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    The IECC energy code is part of the great International Building Code. It pretty much applies to all residential construction and its compliance is required just like the plumbing, electrical and structural codes.

    I disagree that a well designed building should not be equated with minimum prescriptive R values (at least!!!) from the most recent IECC. The other compliance paths are good because of design flexibility but they introduce an abuse factor.

    The alternatives are based on the prescriptive levels which are the intent of the code. In my experience, most designers will use the total UA path when making building envelope tradeoffs. I think using true simulated performance in most residential projects is rare and from my understanding, additions are not allowed to use it.

    Alternative compliance is meant for innovation, creativity and unique design. You can skimp in certain areas and details but it MUST be made up for in others to obtain equal baseline performance.

    The prescriptive values are the basis for this whole system approach. Performance software is easily misused and manipulated, certainly not intended to be used by people to downgrade their building envelope because a certain R value is viewed by them (or their software outputs) to be "excessive". Use alternative compliance very carefully and stick to the prescriptive levels closely to get baseline performance. I much prefer to see folks exceed code minimums!

    The 2012 IECC is not some pie in the sky energy requirement. Its the code. Its the poorest performance allowed by law. Most states eventually adopt it and among the states that currently have statewide adoption: DC, Illinois, Iowa, Maryland, Mass, RI, UT, WA, and the USVI. If you live in those states I feel it should be enforced locally.

    Keep in mind that this in NOT just about energy use. The 2012 IECC took an enormous step forward with the implementation of the first requirements of continuous insulative sheathing for wood wall framing in colder climates. This important step reduces the chances of condensation and mold on exterior sheathing and framing. There are also provisions for mandatory blower door testing and outdoor air introduction that if adopted and enforced (or voluntarily implemented by educated building teams), should have huge benefits to the Indoor Air Quality of our homes and future housing stock.

    The R value minimums in the 2012 IECC are actually pretty pathetic compared to many high performance projects in this country and code minimum performance in some of Europe. I personally feel they are getting close to cost-effective levels for most situations in the walls and roof/attic but not without achieving the Air-sealing and fenestration requirements too which are out of balance and overdue for an update, especially for airtightness.

    As for un-vented crawls, insulation should go on the walls not subfloor. Personally I feel the above grade portion of the crawlspace walls should be insulated to the same levels as the other above grade walls. I also think Zone 3 should require un-vented crawls to be insulated. TN is still stuck in the 2006 IECC but they are one of the many projected states to adopt the 2012 version soon although version 2015 is coming soon to a theatre near you..

    For those on this forum taking the time to build their home right, it shouldn't be about what's locally enforced. Even in locations with strict enforcement its easy as dirt to get away with less than minimum performance. If you value low energy costs, comfort, durability and Indoor Air Quality you should be doing more than the poorest performance you can get away with or what some may view as excessive. The minimums prescriptive values laid out in the 2012 IECC is a great guideline and building code to achieve this in a very cost-effective manner.

  • renovator8
    7 years ago
    last modified: 6 years ago

    It's a waste of time to argue about using the building code as a design manual.

    This post was edited by Renovator8 on Wed, Jun 25, 14 at 22:28

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    The building code is a minimum level of performance. If we cant do better at least we can achieve a minimum standard. I think well designed buildings strive for more than the minimum.

  • snoonyb
    7 years ago
    last modified: 6 years ago

    " If we cant do better at least we can achieve a minimum standard."

    Based upon who's opinion?

    Some bureaucrat that exists in a closed mechanically contrived atmosphere, or a common sense approach based upon the time adjustable climate zones?

    My preference is to throw open all the doors and windows and let the climate of the day envelope me.

    "I think well designed buildings strive for more than the minimum."

    Influenced, unfortunately, by mandated standards as well as political pressures prevalent in states administration, not necessarily shared.

  • renovator8
    7 years ago
    last modified: 6 years ago

    You are quite stubborn about your narrow-minded approach.

    The design of a building envelope should never rely on arbitrary code minimums for an approximated climate zone; it deserves a careful analysis that considers the precise location, the amount of glass, walls, and roof as well as the building orientation and the efficiency of the HVAC system. These things matter.

    For those who understand this I have provided a link to an online program that will allow anyone to design an energy efficient building envelope without needing to rely on arbitrary minimums derived from someone's idea of a typical house configuration and orientation anywhere in a large arbitrarily drawn climate zone.

    When I design a joist or beam I don't look at the code span tables that make rough assumptions for building configuration, the formulas are so simple I can use my own spreadsheet that allows me to alter the structural properties of the members and the span, spacing and depth and be able to consider alternate possibilities or to know when to exceed the code minimum when necessary. It should be the same for energy conservation. Never guess when you can know.

    Here is a link that might be useful: REScheck online

  • Bungalow14
    7 years ago
    last modified: 6 years ago

    Anyway...building on crawlspace foundations is common, even prevalent, in the NC Piedmont region. I dove deep prior to our build, and never found any reports of this being a problem or a shortcut. High end homes, built by the most meticulous and professional builders, sit on crawlspaces.
    I mean, if crawlspaces are so bad, surely there would be some sort of paper trail of substantiation??

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    I apologize for being dense but Iam just lobbying for people to build to code.. at the least. Prescriptive minimums are not arbitrary. They are the intent of the code.

    I understand and approve of alternative compliance and performance modeling as I use it on my passive solar projects to get around the fenestration requirements among other details. I also understand its limitations and how widely misused and abused that it has become.

    Yes, houses and climates are complex and the people who created the software are largely the ones setting the prescriptive minimums and ventilation standards. They have done a marvelous job for the most part. The software and results can be amazingly accurate in the hands of the right professional. Its the occupant behavior variable that tends to throw some things off. For example, take leaving all the windows open with the heating and cooling running..

    Be careful about using software or alternative compliance paths yourself or hiring those outside of their area of expertise. Hopefully, people can identify the correct team in their area to make the appropriate choices. I hope what we've covered here will help.

    Bungalow14 and others who may still be considering a vented crawlspace on the East coast. The paper trail of substantiation on vented crawlspaces is immense. The level of research and evidence of poor performance with vented crawls in humid climates, mainly on the East coast, is overwhelming. The building industry is notoriously stubborn about accepting improvements to the code. I find this to be especially true with older, experienced professionals with little education in building science.

    Advanced Energy in Raleigh has done a lot of good research for your specific area but unfortunately, the links they used to provide on it have been taken down. I strongly suggest you talk to a building science professional in your area before building an attached cave (vented crawlspace) below your home. I imagine that you could probably get in touch with someone about this at Advanced Energy. Have you considered Energy Star or NC Green Build certification?

    Here is a link that might be useful: Advanced Energy website homepage

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    This is a pretty good article explaining why vented crawls can be a problem

    Here is a link that might be useful: Home Energy: Scary Crawlspace

  • snoonyb
    7 years ago
    last modified: 6 years ago

    " For example, take leaving all the windows open with the heating and cooling running."

    Or, the common sense approach, leaving the heating and conditioning a appliances off.

    "The paper trail of substantiation on vented crawlspaces is immense. The level of research and evidence of poor performance with vented crawls in humid climates, mainly on the East coast, is overwhelming."

    In studies related to industries with a specific agenda and funded by supporters of that agenda.

    "The building industry is notoriously stubborn about accepting improvements to the code."

    "improvements to the code," By who's standards?

    "I find this to be especially true with older, experienced professionals with little education in building science."

    Who are also cognizant of the day to day operations of
    the municipality, inherent delays and cost in administration, let alone the cost/savings to the home owner, which may never be realized.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    Snoopy, you may have some points in your usual anti-gov rhetoric but its tough to pick a more unfortunate example than vented crawlspaces in this climate. The problem is more about humid air + cold surfaces than out of control bureaucrats.

    To me, vented crawlspaces in this climate are kind of like a time before building codes required insulation, or fire safety codes, or worse.

  • snoonyb
    7 years ago
    last modified: 6 years ago

    Since you insist, brain....,"Snoopy, you may have some points in your usual anti-gov rhetoric"

    You insist on missing the point, because you have an, "regulation," agenda, but act as if because some study payed for or funded by an organization pushing their product, is the next best thing to heated toilet seats, which is crap.

    And then to site Europe and an example, you are truly agenda driven, little of which has common sense as a tempering factor.

    "The problem is more about humid air + cold surfaces than out of control bureaucrats."

    Sorry brain, no sale. It's the out of control bureaucrats, who in their never exhausting effort to perpetuate themselves, tout stupidity as "the greater good", and the public ends up with conditioned crawl spaces forever.
    Which by the way, you have yet to disclose the specific cost of that little venture so that a cost/benefit analysis would reveal the years to break even.

    "To me, vented crawlspaces in this climate are kind of like a time before building codes required insulation, or fire safety codes, or worse."

    Siting fire safety is shameful, in lite of your agenda.

    There is no relationship.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    I understand that reply and feel your frustration. Allow me one last insist and I promise to stop, as I think the direction we are heading detracts from this thread.

    A few months ago I failed a framing inspection. No big deal really, Ive come to expect that city inspectors will usually find a violation or few on such a widely encompassing and important review. The reason? My electrician missed the draftstopping on a few of his plate penetrations. It wasnt egregious in my view or hard to fix but it was a fire safety violation. It certainly represented a certain amount of administrative cost and delay.

    Meanwhile down the street, a spec home is going up on a vented crawlspace, which is perfectly legal and represents no code violation whatsoever. A peek inside reveals very moist ground with inadequate slope to drainage underneath the pathetically placed plastic vapor retarder, fiberglass batts destined to succumb to gravity through their wire supports, and a maze of ductwork that I cant imagine will not suck or blow from this dark, humid, soil gas ridden cave of an airspace.

    I don’t mind that the inspector turned me down although it irks me that there are worse things going on that get the green tag with no problem. I appreciate a system that provides checks and balances even if it is imperfect. There are many traditional building details that don’t need fixing. Vented crawls in our climate are not one of them.

    In case you missed it, the expenses of correctly dealing with them are one of the many reasons I choose slab (or basement) over crawlspace.

  • renovator8
    7 years ago
    last modified: 6 years ago

    Here again the building code should not be an issue. Responsibility for quality design always rests with designers and builders not the building code or building inspectors. Building inspectors have no obligation to find code violations so the GC (and architect if appropriate) should inspect quality as well as code compliance before the building inspector arrives. The building code might be used as a checklist if you don't have a more complete one of your own.

    As for the vented crawlspace example, the major downside would be loss of energy from ducts in an unconditioned space. The upside is that the duct leakage would probably provide more than adequate drying regardless of the crawlspace design. Ironically many outdated design features can be mutually compensating so they are not seen as a problem.

  • Brian_Knight
    7 years ago
    last modified: 6 years ago

    There are more downsides than loss of energy. The upside of HVAC ducts drying out a vented crawlspace is shaky at best.

  • Oaktown
    7 years ago
    last modified: 6 years ago

    This is an interesting discussion. What I am taking away is that it is important to know enough to make an informed decision as to how things are being done. I was surprised that there have been times during our construction where the professionals could not unanimously agree on the "best" answer to a question. The foundation/crawlspace decision was one of those.

  • snoonyb
    7 years ago
    last modified: 6 years ago

    "A peek inside reveals very moist ground with inadequate slope to drainage"

    So, uninvited, you intruded their property, pulled the installed vapor barrier back to reveal, in your opinion, an inadequately drained crawl space.

    So, where was the bubble on the level you used to determine the grade of the slope?

    And did you re-establish the perimeter seal for the installed vapor barrier?

    "fiberglass batts destined to succumb to gravity through their wire supports,"

    Placed how far apart?

    "and a maze of ductwork that I cant imagine will not suck or blow from this dark, humid, soil gas ridden cave of an airspace."

    Which reminds me, you still have not provided a cost/benefit of conditioning a sealed crawl space so that the readers can determine the length of time to break even.

    "I don’t mind that the inspector turned me down although it irks me that there are worse things going on"

    In your opinion, not universally shared.

    "Vented crawls in our climate are not one of them."

    They will be a building standard of practice long after we are gone, as will the fluctuating climate.

    "I choose slab (or basement) over crawlspace."

    Which is your legitimate preference, however, it is dishonest to present only facts supporting your specific agenda, and not discussing the range of options open to the customer.

    It reduces you to just a salesman.