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Dana1
Senior Member
Posts:6991
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26 Aug 2014 02:48 PM |
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Broadly speaking, a bump out is anything that breaks the shape of the house into something other than a perfect rectangle. It's been somewhat trendy these days to have the face of a house have a few step-backs of 2-6' for architictural interest, but that adds lots of corners. Corners end up being both thermal bridges and leak/weak points in the
air-sealing scheme, and it increases the exterior surface area to floor
area ratio. If you get rid of all those bumps arms & ells you get a lot more square feet out of the same exterior wall length (and wall area). A 2- story cube with a gable or pyramid-hip roof is the most energy efficient shape but kinda boring to look at. A
sprawling ranch with lots of ells bump-outs and set backs can be pretty lousy. Many Net Zero Energy houses or Passive Houses have the "shoe box with a gable" look, but it doesn't absolutely need to be so plain: A 2.5 story shoe-box with a gable: Contrast it to this house with 7-8 different planes on just the ront side of the house, between the bump outs and set backs bay, which is a lot of extra thermally bridging corners to air seal, and would need higher average R value to match the thermal performance of a shoe box with a gable: This one only has six, but really, is it all that exciting to look at? (The multiple roof planes are another issue too- looks like they built a snow & ice trap with the parallel ridges.)
There are happy mediums to be had- it doesn't have to be a shoe-box, but complexity adds both cost and risk to meeting performance goals. Fewer & simpler lines, and using porch overhangs for architectural interest can still perform well: |
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sailawayrb
Veteran Member
Posts:2270
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26 Aug 2014 04:48 PM |
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“Many Net Zero Energy houses or Passive Houses have the "shoe box with a gable" look, but it doesn't absolutely need to be so plain.”
Very true, the highly efficient shoe box house envelope should have a full hip roof with a wrap-around-porch or a gable-covered front/back porch and should be located on enough real estate to ground mount the PV panels out of sight. Less money should be spent on impressing the neighbors (which should be out of sight too) and the savings should be applied to having a home that generates a monthly utility income and that will last for generations. When home, most people spend more of their time looking out their windows as opposed to standing outside looking at their exterior architecture. So having a gorgeous view that varies with the seasons is often preferable to having unchanging showy exterior architecture.
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James02
New Member
Posts:49
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27 Aug 2014 09:56 AM |
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Dana1 - Great explanation of bumps. I read your post three times b/c it was solid education for me. I had no clue about that and will take all that into consideration as I browse house plans. Only if I could get my wife on board with the less aesthetic homes. You give some of the best detailed responses. Thank you. sailaway - You make a great point that we spend our time in-doors looking out, not out-doors looking in. My parents own 60+ acres and I'm considering moving there to build. I would be capable of doing as you stated with ground mount PV panels, and less need to impress the neighbors. Follow up question for anyone who has interest in answering. Q: I browse house plans on the internet, but very state they are made for SIP or ICF construction. Is this a limitation or is just about every house plan capable to be transformed from stick-frame to SIP/ICF? Thank you.
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Dana1
Senior Member
Posts:6991
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27 Aug 2014 11:20 AM |
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A house with a bunch of step-backs and corners can be a nightmare design for SIPs an ICFs, just as they can be for stick-built. Ideally with SIPs you'd be able to use fewer than a dozen distinct wall planes to limit the number of panels you'd have to marry. ICFs are perhaps a bit more flexible, but with every corner the blow-out risk during the pour increases. But just about any footprint COULD be done with SIPs or ICFs, but as the shape complexity increases, so does the cost. A simple L or T topology is fine, but anything more than 6-8 corners probably isn't going to be worth it. How messy do you want the footprint of a 200' house to be, anyway? My ~2400' 1920s 1.5 story bungalow has 14 corners to the footprint, which is NOT the way to go. Reducing it to 10 (which was the original ~1800' design before two additions were tacked on over it's history) would not challenge it's architectural charm in the slightest, even 8 would not have created a boring over simplification. You can add a lot of architectural interest by changing the surface/siding textures/colors and use of overhangs/porches, you don't need a step-back or bump out with every change in siding, but you don't want it to look random either. |
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Dana1
Senior Member
Posts:6991
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28 Aug 2014 11:17 AM |
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James02: As luck would have it, todays blog on the GBA site covered some of the complex-shape problem, with lots of pics. |
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James02
New Member
Posts:49
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28 Aug 2014 04:15 PM |
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Dana1: Thanks for the response. What you said, made a lot of sense to me. I read the blog post on the GBA site and it was pretty helpful. I need to see if I could get my wife to read that article as she is adamant on having a turret on our next home. I'm definitely going to keep this in mind as I review house plans. Thanks again Dana. |
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ICFHybrid
Veteran Member
Posts:3039
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28 Aug 2014 04:53 PM |
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On my build, putting in some bump-outs added strength and allowed the thickness of the foundation to be reduced. |
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Jelly
Veteran Member
Posts:1017
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28 Aug 2014 07:06 PM |
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I've seen a turret made out of steel SIPs. |
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Eric Anderson
Basic Member
Posts:441
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28 Aug 2014 08:12 PM |
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Turrets are a great architectural feature, especially on an ICF house. Ideally you want one on each corner of the house so you have interlocking fields of fire. Heavy Kevlar window shades add a nice touch. This is often referred by interior decorators as “Gaza strip Sheik” All kidding aside all houses are a compromise and there are no right or wrong answers when it comes to design. It does make sense to take a hard look at the details for airsealing and insulation, relative to any house you want to build. If you want irony, the owner of the biggest energy improvement company in CT just had his 13,000 sf house burn down- bummer http://www.rescue9photography.com/Fires-2014/Middlebury-structure-fire-7-3/ |
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Think Energy CT, LLC Comprehensive Home Performance Energy Auditing |
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Jelly
Veteran Member
Posts:1017
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28 Aug 2014 11:40 PM |
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eric, that is an awful disaster to befall that house. What do you think about posting a new thread, so we can respectfully discuss the details? |
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arkie6
Veteran Member
Posts:1453
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29 Aug 2014 12:30 AM |
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Posted By Eric Anderson on 28 Aug 2014 08:12 PM
If you want irony, the owner of the biggest energy improvement company in CT just had his 13,000 sf house burn down- bummer http://www.rescue9photography.com/Fires-2014/Middlebury-structure-fire-7-3/
An interesting line from that story: "The fire was investigated by the fire marshal and revealed that
Polyurethane foam insulation in the attic spontaneously combusted
causing the house to go up in flames and destroying the
multi-million-dollar mansion." |
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Lbear
Veteran Member
Posts:2740
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29 Aug 2014 12:31 AM |
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Posted By Jelly on 28 Aug 2014 11:40 PM
eric, that is an awful disaster to befall that house. What do you think about posting a new thread, so we can respectfully discuss the details?
That house is the subject of much discussion in the green building world. The issue at hand is that there have been many documented cases of polyurethane foam spontaneously combusted and creating infernos. The house in question was investigated by the fire marshal and the report
stated that polyurethane foam insulation in the attic spontaneously combusted. It has something to do with the heat that is generated during the chemical process of when the polyurethane is curing. It creates a condition that the foam then spontaneously combusts. It was discussed on Green Building Advisor HERE and HERE.The irony of it is that once polyurethane foam is cured, it is "fire resistant" and is rated as a Class A and Class 1 fire resistant material. It will not melt and only chars at temps above 800F. |
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sailawayrb
Veteran Member
Posts:2270
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29 Aug 2014 03:01 PM |
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Right, large-scale polyurethane curing is similar to large-scale concrete curing. Both are exothermic chemical reactions that can cause much grief if you don’t address heat removal. Pretty sad. |
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Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do! |
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Lbear
Veteran Member
Posts:2740
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30 Aug 2014 12:58 AM |
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My design is a 2-story with a 1st story that is basically square and a 2nd story that is a rectangle in order to keep the aesthetics interesting so my architect made the 2nd floor layout project over the 1st floor in some areas. This created dimensional appeal and gave me a covered porch. The walls are ICF and the floors are InsulDeck. All 2nd story balconies are 100% thermally broken. It took a lot of planning & work but it can be done. 1st Floor ICF Wall Layout 2nd Floor ICF Wall Layout |
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James02
New Member
Posts:49
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02 Sep 2014 11:16 AM |
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Lbear - what do you mean by "All 2nd floor balconies are 100% thermally broken"? Thank you. |
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Lbear
Veteran Member
Posts:2740
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02 Sep 2014 08:48 PM |
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Posted By James02 on 02 Sep 2014 11:16 AM
Lbear - what do you mean by "All 2nd floor balconies are 100% thermally broken"? Thank you.
The concrete balconies that transition into the 2nd floor interior spaces are thermally broken so that means there are no thermal bridges. This was accomplished by using Schock Isokorbs. |
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ICFHybrid
Veteran Member
Posts:3039
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03 Sep 2014 01:25 AM |
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Try saying that five times fast. |
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linelmarhao
New Member
Posts:17
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18 Sep 2014 04:12 PM |
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Dear Sir, I build several ICF homes and in all of them I have a woodburning fireplace. The key element is design. Nothing better than the roaring of a natural wood fire in the winter.
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ICFHybrid
Veteran Member
Posts:3039
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18 Sep 2014 11:48 PM |
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Maybe you could be more specific as to what type of a wood burning fireplace it is that you feel was such a fine design element in your ICF homes. |
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