Convert 3-season cabin to permanent home

Hi y'all,

I'm spending this year looking for a site in New England for a homestead. I've found a very promising chunk of land in southern Vermont, and it has a 3-season hunting cabin. 24'x24', on cinderblock piers. It is 30 years old, square and dry, unheaved and in great shape. Board and batton siding over stick frame. There looks to be very modest rigid insulation beneath the interior 12" pine boards, but these boards are not shiplapped or tongue&groove. Roof is asphalt shingle over standard ply deck. Windows are fairly modern. Previous owner took good care with it. No water, no power.

I'm interested in this community's ideas : how would you tighten up this structure to make it livable and efficient through a VT winter? through many VT winters. I'm fairly good with tools, but not a professional, if you know what I mean. The feasibility of these ideas will effect my buying decision, but I really love the land that it is on. Good access, good water, good southern exposure.

Here's a few pics. If you have any ideas about efficiency, insulating, or general design thoughts, I'd love to entertain them.

Cheers!
VP

more pics.

https://energycode.pnl.gov/EnergyCodeReqs/?state=Vermont

Code min walls are R-20. Looks like 2x4 walls so you can get R-15 with Roxul, ThermaFiber, or JM mineral wool batts plus some rigid IS R5 boards. The 2x6 roof needs R-38 min, R-23 + R 15 (stacked & staggered) Roxul Comfortboard IS outsulation. That means remove the roof felt/shingles add the IS board on top of the sheathing, then add 1x4 furring strips as ventilation gaps, then add sheathing, then deck the roof with new shingles and a ridge vent. Add the same rain plane/ventilation gaps to the walls if $ allows. Add out riggers to create 24" overhangs, ventilated silicone sealed soffits/facias, gutters. Create a skirt around a sealed crawl space insulated with R-12 IS boards in the same plane as the walls. Add R-23 to floor joist, keep the R-3 reflective foam or move it to the roof to reflect heat in the summer and use IS board in it's place. If there are no National Fenestration Ratings(NFRC) on window labels and no values and they feel cold, add low E glass storm insulated windows, U-value < .30, SHGC > .45 and seal the windows up. South facing windows use a high SHGC as possible.


It's pay me now in insulation or later to the utility bills. Oh, and if there is any $ left get some power and water Power I'd go with a PV panels/batt to the south you say is good, tied to a small single handler miniplit HVAC or space heater, and a stove or mass heater is all the place need. At those insulation levels or higher and a good job air sealing on the wall finish you may only need the stove.



https://energycode.pnl.gov/EnergyCodeReqs/?state=Vermont

http://www.roxul.com/products/residential/products/roxul+comfortbatt

I read that closed cell foam insulation is r-6 per inch, so at 3.5 inches, that's R-21. Here's where I got it: http://www.icynene.com/en-us/architects/spray-foam-basics/compare-open-cell-closed-cell-spray-foam-insulations
At the roofline, we used some foam rafter vents to make sure there was air circulation near the top of our roof before adding insulation.

I'd stay clear of SPF's and most foam products. There is nothing "natural", healthy, or good for our environment about them. I been following open and closed cell for years and little has improved or is understood. In 2015 the EPA is still trying to understand the long term emmistivity, outgasing, of the carcinogenics, fire retardants, blowing agents, chemicals. I read horror stories of the stuff exploding, causing illness, and to dig it all out is expensive. The high density SPF is a vapor barrier so not if but when the wall does get wet it will not dry which will cause microbials. When it is rewetted, and under certain misunderstood conditions, it tries to re-cure that is when it can outgas. This product got popular due to it's air sealing capability a while back and it does not do that great of a job at that if the chemicals are not mixed and applied right, especially over time, now it has caused more bad than good as a toxic vapor barrier as well. The internet is full of warnings but the EPA and International Society of Indoor Air Quality are two good sources.

http://www.epa.gov/indoor-air-quality-iaq/committee-indoor-air-quality-webinar-slides-about-spray-polyurethane-foam

http://www.epa.gov/sites/production/files/2015-01/documents/spf_presentations.pdf

http://www.isiaq.org/

The last two summary bullets are interesting since the air sealing drives a ventilation requirement in itself under debate, add a toxic foam now we just made the required "long term HVAC" air exchange system more complex.

Terry,

thanks a ton for this detailed answer. It gives me a real starting point, and I'm going to go to go ahead with this property.

I had hoped not to hear "batting", as my timeframe to establish this site will be long (5 years) and interrupted, and I know how mice love this stuff when it's not completed quickly.

The roof info is great stuff, I wanted to start up there this summer anyway, to put on a metal roof, and had no idea how to think about insulating it. I would not have thought of doing it external to the decking. Now I have to wrap my brain around venting - most of what I've been reading pertains to attics and homes with different envelopes.

And building a skirt that aligns with grade. Thanks for giving me so much to chew on.

Cheers!
Virgil

Terry Ruth wrote:

Code min walls are R-20. Looks like 2x4 walls so you can get R-15 with Roxul, ThermaFiber, or JM mineral wool batts plus some rigid IS R5 boards. The 2x6 roof needs R-38 min, R-23 + R 15 (stacked & staggered) Roxul Comfortboard IS outsulation. That means remove the roof felt/shingles add the IS board on top of the sheathing, then add 1x4 furring strips as ventilation gaps, then add sheathing, then deck the roof with new shingles and a ridge vent. Add the same rain plane/ventilation gaps to the walls if $ allows. Add out riggers to create 24" overhangs, ventilated silicone sealed soffits/facias, gutters. Create a skirt around a sealed crawl space insulated with R-12 IS boards in the same plane as the walls. Add R-23 to floor joist, keep the R-3 reflective foam or move it to the roof to reflect heat in the summer and use IS board in it's place. If there are no National Fenestration Ratings(NFRC) on window labels and no values and they feel cold, add low E glass storm insulated windows, U-value < .30, SHGC > .45 and seal the windows up. South facing windows use a high SHGC as possible.

My family just got two semi loads of rigid foam board insulation, like new for free. All you have to do is find a big commercial building that is replacing the roof. Ours came from a hospital. The roofs on commercial buildings are often made of rubber. If it gets a leak anywhere, they tear the entire roof off and replace it. The insulation that comes off is normally just like new. I also got ten of thousands of square feet of commercial grade rubber roofing for free this way. A little leg work and you can easily insulate this house for nothing but your time and labor.

I've just gone through this exact process. I went with 5.5" sip panels wrapping the outside of the building. They were one sided renovation panels, so only osb on one side. It was reasonably priced, and added r24 to the building, plus whatever I do inside.

Hi Rob, that's one thing I hadn't thought of - I'd love to see more pics of the install, if you have them. I assume this gave you the opportunity to relocate windows, doors, and other features. I'm off to google these SIPS. Was routing for plumbing/electrical an issue?

Cheers,
Virgil

Not an issue for my house, the inside has 2x6 framing with roxul insulation between the posts on one half of the house, the other half was all glass and poor quality doors so it all came out. I will be adding some interior framing to that half eventually. I'll be putting in new windows and doors when it warms up a bit, but yes they can now go wherever I want.

Original crappy walls from inside


All torn out


Inside

Might want to read my blog in my signature about SIPS and metal roofs about half a ways down. Your back to everything that I posted on SPF above for one since that is how SIP panels are manufactured with die tooling. The neoprene, etc, seals in between panels do not compress properly nor seal, are not permeable enough, and moisture gets trapped in the cavities. Combine that with SPF and microbials will result. Open cell or closed cell foams have never mated well with the formaldehyde's in OSB, phenol or urea based, most pros know this. SIPS is not cheap either and there are some things to know about the construction methods again see my blog of a $20 million commercial job we did. In my blog I point to case studies of failures in the relatively short time SIPS has been in construction and there is not enough time to surface all it's issues. Some will say there is proven data dating back 30 years but that is sales hype since if you look at the design it is not what it is today and the tested configuration has been lost.

If you want SIPS type natural construction check into cast in place monolithic(no sealed seams) hemp or limecrete construction yielding high levels of insulation(~ 2-3 per inch), hygroscopic clean mass. I believe the mineral batts and boards I mention are insect and rodent resistant if I remember correctly. I also believe if your search or call a manufacture you can find eco friendly SIPS like those that use magnesium(MAG board), hemp, straw, or gypsum board bonded structural insulated panels. It also would not be that difficult to get some say MAG/GYMP board and bond some limecrete or hempcrete core to make a sandwich construction(board-crete-board) then assemble it to the studs you have as non-structural outsultaion. Fill in the gaps with lime. You'd just want to add more fibers than binders to keep the panels insulating and light. I'd question if SIPs on 2x6 rafters passed code for your roof loads and climate, I'd suggested looking at 2015 IRC or hiring a professional engineer to determine if the structure is capable.

I been posting on this site a while now and find it interesting how this section of the forums was once called "green building" that was changed to "natural" since we wanted to get away from the 'green" misnomer and focus on natural materials from mother nature. Now we are starting to get alot of the same suggestions of using mainstream toxic foams, plastics, OSB, etc, that the green sites suggest, that also produce CO2 rather than absorb it like lime. If you want to know more about SPF and OSB try Green Building Advisors in the Q&A section, ask for Martin Holliday. I call the site toxic "Foam Building Advisers" just for kicks and grins. You'll find alot of them are now seeking foam free construction due to all it's issues.

Not everyone has time to cobble a house together out of mud, straw, chunks of firewood and glass bottles. Lol I have been appreciating my modern toxic insulating layer when we hit - 20c for a few weeks.


How much would some sort of hybrid hemp board /misc eco board sandwich system cost? Don't get me wrong I would love to use something like that, but first off trying to source it, then trying to afford it.

There are noble ideas, and there is the real world. You have to find a balance between budget, time, and dreams.

Rob, first off the natural construction methods advocated on this site are cost effective especially when you factor in the life cycle cost (SIPS < 10-12 years) of maintenance and medical bills many are chemically sensitive to mold and mildew, bacteria, or "green" mainstream construction methods. Many if not all the natural methods and materials like lime or geopolymer MAG cements have dated back to the beginning of building time there is a ton of history on unlike PU SIPs. I forgot the cost of the SIPS we used ( I did not design BTW) but it was not cheap. Lime is very cheap and straw is cheaper and hemp shiv or herd can be sourced legally in some states now and is a rapidly growing market. I'd say material and labor for cast in place walls is going to be less than $3.00 SF hired less if DIY and of course that is dependent on location. The labor skill set is low, get a mortar mixer mix 70% straw or hemp to 30% s-type lime you buy for $.125/lb. Due to the monolithic bond of the binder to every thing it touches if you were to blower door test it compared to SIPs it will exceed the air changes per hour by far yielding less time and money in open cell foam and calking. Now you just dropped your HVAC loads and utility bills ~ 30%. Use the junk OSB as form work doing 3' courses starting at bottom. Virgil has construction time, the casting needs to dry in depending on time of year about 1-3 months you check for less than 20% MC @ center before you finish the build. It does not work for me a production home builder, I use faster natural methods. Goggle hemp or strawcrete homes all over the internet nothing new, no "dream' been said and done for centuries now. There are many high silica content grasses you source off your land free that work too.

Interesting, what do you think about using this method on the inside of the panels between my posts and beams? Would that seal off the sips toxicity and seal off any air passages?

Yes Sir, if possible get rid of the seals they are worthless. Take some high silica grass, straw, or hemp mix it in a mortar mixer or bucket then fill the SIPs cavities with it. Let it dry perhaps using a whole building dehumidifier inside and fans if there is not alot of heat and wind. Get one of those cheap agriculture moisture level meters drill a hole to the center of some different cavity areas you fill later. The moisture content should be less than 20%. You are now ready to install your clading (sheathing, wood panels, drywall, whatever floats your boat

If you read my blog like I suggested you see all the bandaids to deal with the seams so it will be critical to dehumidfy your interior space and maintain it to - 30-40% max constant relative humidity which will help keep your building healthy and sustained. The exterior 1X furred ventilation gap/rain plane I described above and in my blog will allow drying to the vent many subscribe to as well. If you have an OSB grade that is now being found to have air sealing issues by blower door testing or there are some test on the net, your build will pass air which if it is not that fast can aid in drying the seams, as well as at the same time if it is too fast you will lose conditioned air through the seams depending on where the low temperature and humidity levels are at, across the boundary (interior or exterior surface layers) so, it would not be a bad idea to surface coat all the OSB with a scratch and/or finish coat of lime. Keep the type s lime wet a couple of times per day until it cures (absorbs CO2) on the OSB for the time it takes to dry the limecrete in the SIPS cavities 1-2 months or depending on the moisture meter used for the cavities. Now clad as desired. Now you have a well bonded monolithic baidaide over SIPs which may not be that bad. Use the limecrete to seal window and doors or a silicone caulk is not bad since silicone vs latex is natural, permeable like lime. To get into small areas use a lime motor applicator.

Excellent... I might just do this! How thick on the outside scratch coat?

Thanks!

The reason I suggested lime is because when it gets wet and dries and that process recycles it absorbs CO2 as it cures and re-cures over the course of years it continues to get hard as a rock (since that is what it wants to covert back to) and remains very permeable, durable, hygroscopic. The adsorbtion of C02 self cures cracks that other products cannot that allow liquid water in. Once liquid water gets into a product, especially masonry or OPC, it can cause all kinds issues such as rust jacking of steel rebar, efflorescence, out gassing; break down of mechanical, physical, and chemical properties. Therefore, lime has a very long history of being an outstanding superior building product due to it's ability to absorb CO2 for these reason in part. I suggested the lime on SIPS also because as I clearly provided data on, polyurethane has been proven by the EPA to emit a harmful gas to indoor air, and the lime may help absorb and/or chemical stabilize the known formaldehyde issues with OSB. The inert lime will also act as a humidity and vapor buffer due to its ability to adsorb CO2 and isolate any chemical reactions to any cladding that is placed in contact with the OSB.

Rob Bouchard wrote:Excellent... I might just do this! How thick on the outside scratch coat?

Thanks!

As thick as you can get it and afford, I'd say at least an inch. If the lime won't stick at first since it is uncured and stubborn add about 30% sand and more lime or switch to a type n if it is very humid out, or conduct trial applications in a small area to get the mix to adhere. Keep wetting the lime so it can absorb C02. As it does the bond strength of the lime to OSB will get stronger and stronger in time. It may even be necessary to scratch the resign on the surface of the OSB with some sharp garden tool or or sand it with course using a OSHA mask or something to get it to adhere.

If you want a real great surface coat you can pigment with iron or earth oxides on the interior continue to build the lime up to 2". You could even add some kaolin or magnesium bentonite clay you get at local ceramic supply house or screened off your land to a fine grit to the mix with the lime to increase the vapor buffering ability and initial bond strength. If you can get a hold of some vapor buffering aggregates like pumice, scoria, vermiculite, perlite, etc, or a mixture of them, that will help further manage the interior humidity I mentioned without the use of a whole house dehumidifier. Use a humidstat.

Your welcome, glad I could help and good luck!

Thanks again Terry, hemp isn't readily available here, so I'm going to give straw a go and fill these interior cavities... Any problem with going 4" thick or thicker?

You're welcome. If you're getting it in the seams pack it in, if just on the surfaces all the test including my own I seen the first two inches has the most hygrothermal storage areas anything past 4" unless needed structurally is a waste of $. Wheat straw bonds best with lime but any will do don't use green and dry it in before clading. Sand can also be added, the whole idea for hygrothermal insulation and isolation is enough aggregates to keep the lime together and from cracking. Lime manages moisture and is the binder, straw provides r-value, sand helps hold together as does straw. Type S lime in most applications is best due to it's higher bond strength.