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Cs2074
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# Posted: 9 Aug 2018 12:33pm
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I am in the planning stages of a new cabin build. One of the reason I am building a new is because the current cabin in not insulated so it is too hot in the summer and too cold in the winter.
I want a cabin we can use year round.
I thought closed cell spray foam would be a good idea. I got a quote to insulate a 20x20 cabin.
The quote was for closed cell foam 3" thick in the walls ,floor, and roof.
The price was 8,000 . It seams really high to me. can anyone give me price per square foot that they paid for foam?
Has anyone used a diy kit to insulate their cabin?
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razmichael
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# Posted: 9 Aug 2018 12:49pm
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i can't actually provide you costs (don't remember and likely not worth comparisons) but Yes, it is expensive.. However, you might look at a mixture. I used Roxul (rock wool) in the main floor walls as it is really easy to work with (easy to cut and fit). Cathedral ceiling (hot roof design) and end walls in lofts were spray foamed - this reduced the overall cost and allowed for extra in the ceiling (to meet code although I did not need to do this).
Suggest you consider options on how much to foam but also get more quotes - nothing like a little competition.
I have seen examples of people trying to use the kits and it can be a complete disaster. It is one of those things that is not as easy as it looks. naturally some have had luck with the kits but when I priced them, the cost was way more than I expected and pushed me to just get the experts in to do it.
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fiftyfifty
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# Posted: 9 Aug 2018 01:25pm
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Price around here (northern US state) is about $1 per square foot 1 inch deep. So a 1ft x 1ft area 3 inches deep would be $3.
I did a combo approach- paid to have spray foam in the cathedral ceiling, put fiberglass myself in the walls. Wish I had just saved up and had the whole darn thing sprayed...
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razmichael
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# Posted: 9 Aug 2018 01:51pm
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Quoting: fiftyfifty I did a combo approach- paid to have spray foam in the cathedral ceiling, put fiberglass myself in the walls. Wish I had just saved up and had the whole darn thing sprayed...
 - i certainly considered the same thing. Timing, working on my own and other factors pushed me to do the main area with the Roxul - not sure I would have had such a "good" time if using fiberglass! I can't stress how effective the spray foam in my gambrel roof is! about 6" thick and along with great heat and cold insulation, cuts down noise and strengthens the roof.
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Cs2074
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# Posted: 9 Aug 2018 03:24pm
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Based on the $3 /sf it would be about 5 grand
I am not comfortable with DIY. I Think it would be like painting a car It requires some skill to get it right.
I plan on a metal roof with bubble warp and was going to spray under the bubble wrap.
Anyone ever use bubble wrap under the subfloor?
saw a YouTube video where they put wrap over the joist and put plywood on top. They also put a skirt around the cabin that used bubble wrap and t-111
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razmichael
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# Posted: 9 Aug 2018 04:39pm
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If you end up spraying the roof why the bubble wrap?
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Cs2074
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# Posted: 9 Aug 2018 09:55pm
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Not sure why bubble wrap I was thinking if the roof ever needed replaced it would be difficult if it was sprayed directly on the metal
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ICC
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# Posted: 9 Aug 2018 10:43pm - Edited by: ICC
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Quoting: Cs2074 Not sure why bubble wrap I was thinking if the roof ever needed replaced it would be difficult if it was sprayed directly on the metal
Yes to that. Foam sprayed on the underside would make roofing replacement difficult and expensive as the foam would be ripped off. That is but one of the reasons it is more usual to sheath the rafters or trusses with OSB or plywood first. Then the foam is applied to the underside of sheathing and the framing. The weatherproof barrier (tar paper (felt) or synthetic barrier) is then applied on top and the finish roofing, metal or whatever, applied on top of that. The sheathing also imparts structural rigidity to the roof assembly that most metal sheet roofing can not supply.
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ICC
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# Posted: 9 Aug 2018 10:53pm
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Is there a reason you want to insulate right up there under the roofing instead of insulating the ceiling? Three inches of even the best foam does not really provide sufficient R-value in a ceiling for almost any location in the USA. Most of PA is recommended to use R38, some R49 as a ceiling minimum. Link here.
Or are you planning to build it as a cathedral ceiling? If a well-insulated ceiling or roof is paramount a cathedral ceiling makes that task much more difficult.
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razmichael
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# Posted: 10 Aug 2018 05:58am
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Quoting: Cs2074 Not sure why bubble wrap I was thinking if the roof ever needed replaced it would be difficult if it was sprayed directly on the metal
Sorry - I was assuming you planned on a sheathing. When I said I sprayed the ceiling this was not directly on the metal.
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Cs2074
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# Posted: 10 Aug 2018 01:46pm
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I plan on cathedral ceiling and a loft. So at best I would only get about r-19 in the 2x6 rafters.
I have never sheeted a metal roof but always use bubble insulation under the metal.
I am not too worried about keeping warm in the winter because a woodstove in this size cabin would cook you out.
I am more concerned about keeping it cool in the summer without AC.
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Steve_S
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# Posted: 11 Aug 2018 04:58pm
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Hi there...
I'm in NE Ontario Canada & built a 20X24 off-grid cabin which is more or less hyper insulated and does exactly what you want. Cathedral Ceiling and loft is half the length.
In winter it takes nearly nothing to heat it as once the slab is up to temp, in Summer it uses no power to cool and is on average 10 degrees Celsius cooler inside then outside, as the Frost Protected Slab keeps the temps even. This summer we have had a heat wave here and one day it was 42C / 107F on my property (the hottest day yet) and it only reached 25.6C / 78F inside ! I have a digital thermometer sensor mounted to the north side, outside of my power house, always in the shade. PS: NO FANS, NO AC, JUST OPEN WINDOWS & DOORS !
Radiant Floor System from the Radiant Company.com, 5 min. per hour is all it takes to keep it there. LPG Fuelled Dedicated Takagi TH3M On Demand Heater.
FPSF (Frost Protected Slab Foundation)
I used this method for several reasons but mostly due to ease and energy efficiency gains that it offers. I have a REF below which explains the concept / method well. Mine has a couple of Variations though: I used 4" XPS RoofMate for R20 insulation underneath & up the sides. The slab Wings (extensions away from house) are 24" as well which retards frost from getting underneath. All this isolates the slab and prevents heat exchange between the ground / surface and the thermal mass which regulates your inside temp. More Up to Date we DID NOT USE SAND (that was proven to be a terrible idea - cracking slabs resulted) instead the entire slab sits on highly compacted A-Grade Fine and that also fills the raised section too. The 7/8" PEX Radiant Flooring is imbedded within to 8" of slab edge configured as 1 Zone & embedded temp sensor too... Always read the slab temp, never the air temp to regulate properly.
REF: http://publications.gc.ca/collections/collection_2011/schl-cmhc/NH15-457-1998-eng.pdf
Woodstove is a backup & convenience - ambiance.
Construction used is Advanced Framing Technique 2x6 24"-O.C. which reduces lumber waste & over use, optimizes headers & improves thermal efficiency plus. Energy Efficient Headers, double top plate. The roof is 2x8 @ 24oc , 9:12 pitch with a Ridge board along the centre, 24" overhangs and 24" deep eaves. The "Cool Roof" technique was used to finish it, so the on top of the sheathing there is a roofguard sheeting then 2x4 battens (on the flats) running up along every rafter with 1x6 cross battens ad then the tin. There is a 2-1/2" channel cut through the sheathing at the eaves (4" from the edge) that allows inbound cool air up and with the Vented Ridge Cap allowing the hot air out, it prevents thermal transfer between the tin & the roof, manages the air and moisture and sheds it away.
ADV Framing REF: Info at http://www.greenbuildingadvisor.com/cad/building-plans-advanced-framing & https://buildingscience.com/documents/insights/bsi-030-advanced-framing
Roof REF: Really Good Explanation of the method / concept.
http://www.houstoncoolmetalroofs.com/cool-roof-information/cool-roof-design-texas/
Finished Siding in my case is Eastern White Cedar, I used 8x1" "Barn Plank" with 2" space between and 1" thick Live Edge Face boards, all that on top of the 1x4 strapping. It's done as a rain screen install, allowing air flow from the bottom to rise and leave no damp spots. The key is air flow and moisture mitigation. This is also a Thermal Break from the heat / sun, cold, snow and blustery winds, again improving efficiency of the overall shell. I set mine up so that the air vents to the eaves, which is them ultimately sucked up through the roof and out the ridge vent... well that was the idea and it seems to work as intended.
INSULATION ! The gotcha that get's everyone.
I got mine from two different Commercial Roofing Companies in the local big city... well 200km / 120 miles. They are legislated to recycle all recyclables which includes the various foams used for roofs. They get credits and it works out to everyones best interest - including smart shoppers. Here's my list and it is in Canadian Dollars.... I had to cut all the pieces and stuff them into the built frame (my bldg. inspector was a PITA on this point, now he knows better).
Walls: Type-II High Density EPS, 5-1/2" thick, 4'x4': $10 ea.
Roof: 4"-4'x8' Fibre Paper Faced PolyISO sheets: $8 ea.
3.5"-4'x8' sheets: $7 ea.
Foundation: 4" Dow RoofMate HD Foam, 2'x4' $ 10. ea.
FYI: Foam Insulated = high efficiency and air tight ! You will HAVE TO EXCHANGE AIR with the outside !!! You will also have to ensure adequate air supply for any gas / wood burning appliances.
The Air Exchanger / Ventilator I used is based on this below... Works a treat, used 12V fans instead and solid aluminium centre pipe and a different end outside for a better look.
https://www.wildsnow.com/17884/how-to-build-air-cross-flow-heat-exchanger-budget/
Anyways, that's a quick summary, such as it is, I have most of this info posted here on this forum in my Cabin Build 2015 thread. I'm not that often on the board anymore as I check in once in a while, fairly busy these days with projects... I hafta get around to updated my thread but that will take quite a bit, so not likely before winter... Just too much to do ! I like it like that, especially when my chipmunks start telling me to chill, or I get weird looks from the other wildlife... Yeah, I'm deep in bush …
Good Luck and have fun !
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Wilbour
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# Posted: 12 Aug 2018 05:14pm
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Quoting: Steve_S FPSF (Frost Protected Slab Foundation)
Thanks for the link Steve!
A Passive Solar home on the Island used this method. I figure with a high water table in the spring this could alleviate some issues.
BTW. The Passive Solar home uses next to no heating to keep it warm in our cold Ontario winters. Amazing!
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