PanelCrafters
Advanced Member
Posts:680
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| 20 Nov 2012 12:53 PM |
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I'm planning on building a small mountain shack(Coach House) in the Colorado Mountains this spring and I'm seeking ideas for the best(your idea) wall assembly to utilize.
Some Facts:
Environment:
Elevation........: 8,500'
Southern Exposure: Yes
Solar Insulation.: 6.50 KwH/ms/Day(Direct Normal Solar Radiation)
HDD..............: 7,000 - 8,000
CDD..............: 500
Climate Type.....: Semi Arid
Minimum Required R-Values:
Walls............: 50
Roof.............: 65
At this time nothing is 'set in stone'. I'm looking for a somewhat afforable solution that will provide me near Passivhaus standards.
I'm thinking of using SIPS(8" - R-30) for the outer layer due to their strength and their air tightness. Then maybe 2" of EPS(R-8) to eliminate thermal conductivity for the top and bottom plates and to increase the R-Value. Then finally an interior stud wall with another R-15 worth of batt insulation.
What are your ideas for the best wall assembly for this location?
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| ....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building? |
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Dana1
Senior Member
Posts:6991
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| 20 Nov 2012 02:05 PM |
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Sounds expensive. A Larsen Truss or double studwall approach with blown cellulose would usually be cheaper than SIPs + foam, but the latter is quicker to assemble. Keeping OSB clad SIPs truly air tight over the long term is also proving to be an issue in the field, which could be a problem for PassiveHouse-tightness over the course of a quarter-century or more.
The wall assembly that makes the most sense changes with the foundation type, since that affects the ease with which a good thermal break is achieved at the top of the foundation and foundation sill. The phrase "...eliminate thermal conductivity for the top and bottom plates..." has little meaning- it's all about the average R-value or U-factor. Having only R8 at the foundation sill & foundation would result in the heat loss of the above grade portion of the foundation exceeding that of all the rest of the wall area combined, assuming the rest of the wall is truly R50.
In a house with those R values the windows will by far dominate the heat loss, and it's worth doing the site & design math on the solar gain & thermal mass to keep from having to open the windows in the dead of winter to cool the place off. SIPs have very low thermal mass compared to high-R cellulose, but even with a Larsen Truss you'd still be wanting to design in some thermal mass to the rest of it.
I guess the problem is, you can't really spec a "best" wall system in a vacuum- it has to work well with the entirety of the building envelope. |
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PanelCrafters
Advanced Member
Posts:680
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| 20 Nov 2012 03:02 PM |
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Dana,
Thanks 4 the reply. This will be a 'Coach House' so the entire 1st floor will be a garage and storage areas. The garage slab will have somewhere around R-20 beneath it and will be isolated from the frost walls with probably 1"(R-5) styrofoam. Pex tubing will be encased in the slab.
The R-8 is on the upper level, and I was planning using a SIP rim to help eliminate the thermal conductivity there. The lower level walls are as yet undetermined until the foundation design is completed.
With the deep walls, I may go with double windows and an insulating shade/drape for nighttime. There will be pex placed in gypcrete for the heat up there(overkill, yes, but there is a reason for that).
For the roof I was thinknig about using 16" TJI's with EPS insulated webs and 2-high density R-30 fiberglass batts. And then 1"(R-5) under the drywall as a thermal break.
Any ideas or comments are welcome. |
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| ....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building? |
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SCIP Panels
New Member
Posts:12
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| 08 Dec 2012 05:00 AM |
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With all the house lost to fire in your area Are you or what are you considering to use to mitigate fire danger.
Building in the Colorado mountains and looking for affordable energy efficient system that also had strong fire resistant characteristics is what brought me to SCIP systems Structural Concrete Insulated Panels. |
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PanelCrafters
Advanced Member
Posts:680
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| 08 Dec 2012 06:15 PM |
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Posted By SCIP Panels on 08 Dec 2012 05:00 AM
With all the house lost to fire in your area Are you or what are you considering to use to mitigate fire danger.
Building in the Colorado mountains and looking for affordable energy efficient system that also had strong fire resistant characteristics is what brought me to SCIP systems Structural Concrete Insulated Panels.
Point taken. The lot is in the city and after grading finished there will be little remaining vegetation. My greatest fire danger will be from lightning.
My manufacturer does not supply SCIPs so therefore I'm probably going to go with OSB SIPS or maybe a custom hybrid wall.
Thanks! |
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| ....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building? |
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SCIP Panels
New Member
Posts:12
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| 08 Dec 2012 11:34 PM |
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Food for thought
80% of the houses started on fire from sparks flying in the air.
The sparks settled on the ridges, channels and fuzzy textured cedar siding.
Sucked into the attic from soffit and gable vents.
And a surprised to me sparks sucked up from the bottom plate line up between the siding/ stucco and sheathing/foam.
One home owner with a foam home was told foam homes will not burn down. Tell it to him now his did.
The majority of the remainder of the homes that burned down did so from flames jumping from home to home.
Look into wildfire glazing many of the window companies are not aware they even can offer such a product.
Fire stop venting is available as well.
If you want more information email me [email protected]
I will be adding a page to simsbuilt.com regarding fire prevention and building soon. |
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Lbear
Veteran Member
Posts:2740
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| 09 Dec 2012 02:32 AM |
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Posted By SCIP Panels on 08 Dec 2012 11:34 PM
Food for thought
80% of the houses started on fire from sparks flying in the air.
The sparks settled on the ridges, channels and fuzzy textured cedar siding.
Sucked into the attic from soffit and gable vents.
And a surprised to me sparks sucked up from the bottom plate line up between the siding/ stucco and sheathing/foam.
One home owner with a foam home was told foam homes will not burn down. Tell it to him now his did.
The majority of the remainder of the homes that burned down did so from flames jumping from home to home.
Look into wildfire glazing many of the window companies are not aware they even can offer such a product.
Fire stop venting is available as well.
If you want more information email me [email protected]
I will be adding a page to simsbuilt.com regarding fire prevention and building soon.
When you refer to "foam homes", are you referring to polystyrene or EPS? EPS is in and of itself not flammable but will burn/melt when exposed to an outside heat/fire source. ICF is also fire resistant, it has a fire resistant exterior coating (usually stucco or cement siding) and the 6" of concrete provides the core of fire resistance. Just like Steel SIPs, you basically have 26 gauge steel skins sandwiching EPS. SCIPs is comprised of EPS also, it is protected by the layer of concrete on each side. I would state that ICF, Steel SIPs and SCIPs are all fire resistant building practices. In the end, gable and soffit vents are the Achilles Heel of homes. The embers find their way into the gable and soffit vents and the rest is history. The best way to prevent this is to build an attic without vents, or a "hot" attic. Steel SIP roofs make for great ventless roofs. No gable or soffits, equals no embers to find their way in. |
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SCIP Panels
New Member
Posts:12
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| 09 Dec 2012 04:02 AM |
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LB
I am just calling it a foam home as I do not know first hand what EPS system it was made of. The owner thought he had a fire resistant home.
Not all foam homes are sufficiently treated on the exterior to withstand wild/brush fires.
Stucco and Cement fiber siding will not burn but will transfer heat to melt the foam. Wood siding will burn as we all know.
Most Stuccos only give a 30 minute fire rating compared the two hour ShotCrete fire rating on SCIP walls.
The Stucco homes and wood homes both had fires start between the exterior finished product and the osb sheathing. The burning embers were sucked up from ground level.
Wild fire glazing could have saved the houses that the fire entered through broken windows. If the home were better sealed at the plate line and soffit and gables the home loss could have been considerably less.
EPS foam home are only as fire resistant as the exteriors finish and its heat transferring properties.
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Lbear
Veteran Member
Posts:2740
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| 09 Dec 2012 04:14 PM |
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Posted By SCIP Panels on 09 Dec 2012 04:02 AM
LB
EPS foam home are only as fire resistant as the exteriors finish and its heat transferring properties.
Being that I am out in fire country the first thing is 30' defensible space to any and all structures. All brush and trees within 30' will be removed. The home itself will be 6" ICF with StuccoMax exterior coating, which is flame resistant and zero smoke spread and has I believe a 60 minute rating (need to verify). Without any "fuel" for the fire within 30' of the home, I am not worried about flames coming close to the home. I don't have Ponderosa trees, just juniper and they are around 10' in height. The roof will be 26 gauge Steel SIPs with the same SIPs providing the 24" soffit overhang, topped with a standing seam metal roof. There will be NO gable or attic vents and therefore no worries about embers finding their way into the attic, as I will not have an attic. Overall, I think the above design will be very fire resistant. The neighbor on the lot 1/2 mile away with his wood siding home, not so much. This years Colorado fire hopefully was a wake up call to those living in forest fire areas. I believe SCIPs are a great method but for now due to the very specialized techniques of SCIPs, its use is very regional. A few companies emerged but some went under and dissipated. I do hear that SCIPs is doing well in South America and here in the SouthEastern USA. One issue I hope they resolved was the thermal bridging caused by the steel trusses embedded in the EPS. Those trusses provide a thermal bridge from the outside Shotcrete coating to the inside Shotcrete coating. |
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Dana1
Senior Member
Posts:6991
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| 10 Dec 2012 02:25 PM |
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Posted By Lbear on 09 Dec 2012 02:32 AM
Posted By SCIP Panels on 08 Dec 2012 11:34 PM
Food for thought
80% of the houses started on fire from sparks flying in the air.
The sparks settled on the ridges, channels and fuzzy textured cedar siding.
Sucked into the attic from soffit and gable vents.
And a surprised to me sparks sucked up from the bottom plate line up between the siding/ stucco and sheathing/foam.
One home owner with a foam home was told foam homes will not burn down. Tell it to him now his did.
The majority of the remainder of the homes that burned down did so from flames jumping from home to home.
Look into wildfire glazing many of the window companies are not aware they even can offer such a product.
Fire stop venting is available as well.
If you want more information email me [email protected]
I will be adding a page to simsbuilt.com regarding fire prevention and building soon.
When you refer to "foam homes", are you referring to polystyrene or EPS?
EPS is in and of itself not flammable but will burn/melt when exposed to an outside heat/fire source. ICF is also fire resistant, it has a fire resistant exterior coating (usually stucco or cement siding) and the 6" of concrete provides the core of fire resistance. Just like Steel SIPs, you basically have 26 gauge steel skins sandwiching EPS. SCIPs is comprised of EPS also, it is protected by the layer of concrete on each side.
I would state that ICF, Steel SIPs and SCIPs are all fire resistant building practices.
In the end, gable and soffit vents are the Achilles Heel of homes. The embers find their way into the gable and soffit vents and the rest is history. The best way to prevent this is to build an attic without vents, or a "hot" attic. Steel SIP roofs make for great ventless roofs. No gable or soffits, equals no embers to find their way in.
Just to be clear, polystyrene sure as heck IS flammable, and will sustain it's own flame without an external heat source once the surface reaches ~750F or so when given the right amount of combustion air. But that is also a temp at which it's already a gooey flowing liquid mess with little resemblance to a solid, and by the time the EPS in a SIP core reaches that temp it's a foregone conclusion that the OSB skin is already on fire and the characteristics that gave the SIP's structure have been severely compromised. I'm not convinced that the steel skin of a steel SIP is an inherently better combustion barrier for the foam, and even though the steel won't light-off until truly extreme temps are reached, the thermal conductivity of the steel would make the EPS melt sooner than that of an EPS skinned SIP in a house surrounded by burning forest. A infra-red reflective surface finish would help some. (Can anybody point me to some specs or testing on that?) |
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sailawayrb
Veteran Member
Posts:2283
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| 10 Dec 2012 05:29 PM |
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Building with SIPs is one of the cheapest ways to build. So if you have a total loss due to fire, your $$$ loss will be less. However, I have never been a fan of SIPs for the reasons Dana described. Fires also often start from inside of the house. |
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jonr
Senior Member
Posts:5341
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| 10 Dec 2012 06:07 PM |
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I do hear that SCIPs is doing well in South America I think they would do better in cold climates if they started packing the center with cellulose. Greater R value per $. |
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SCIP Panel
New Member
Posts:50
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| 10 Dec 2012 07:35 PM |
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Oakridge National Labs rates Foam securely fastened to concrete on the interior side of the wall the most energy efficient wall system of the 16 they tested.
I am a big supporter of EPS building.
Sips and ICFs have their strengths; Wind and earthquakes yes but fire resistant’s is not one of the strengths.
Unless you apply a protective barrier, i.e. a non burnable layer to stop the heat and flame long enough for the flames to pass.
(I would state that ICF, Steel SIPs and SCIPs are all fire resistant building practices.)
Not if you do not protect the foam from flame and heat. It will disappear leaving you with sheets of metal or cement pixie sticks.
Put a torch to EPS and tell me what happens, Same thing that happened to the EPS home in the Colorado Springs Fire, PooF Gone. Gone is Gone flammable or not
SCIP out performs the rest because of the Concrete skin inside and out.
Outside gives you a 2 hour fire rating where regular stucco falls short.
Inside you have the same fire protection with thermal mass, the Flywheel effect that give a 50-70% energy saving over non thermal mass systems.
With all the SCIP systems I have seen except one the wire truss is embedded in the concrete so how much thermal bridging is there?
Fact the home I finished this year had the thermostat set at 55 last winter and the morning temperature never dropped below 60. So how much thermal bridging was there?
If you want to get technical others are way more knowledgeable than me. Engineer Merline Van Dyke in Lakewood Colorado for one. He has been designing and helping develop EPS systems since 1992 or before. I can pass on his contact information if you like. Few fifty year olds have his energy at 80, his knowledge base is vast.
Comparing un-finished walls paint ready to finished SCIP wall is apples to oranges cost wise.
When SCIP walls have its finish coats of Shot Crete it’s done.
When an ICF or SIP is done you need to hang drywall and siding and that is not a minor cost.
SIPS are the fastest and if the cost was the same and you were not in extreme weather conditions or fire area it would be a system in consideration after all I am a carpenter at heart.
Richard Sims
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PanelCrafters
Advanced Member
Posts:680
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| 10 Dec 2012 08:00 PM |
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Talk about a hijack.
Fire resistance is nice, but it's not my priority. When a wildfire such as the nature induced one that hit the Springs last summer occurs, all bets are off. Been there, saw that. A solid concrete house isn't in the budget. It's just going to be a cool Coach House...
Hybrid wall suggestions? |
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| ....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building? |
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