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Alternatives to rock wool insulation of a wooden house?  RSS feed

 
adrian dwor
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Hello,

We have a small 17m2 garden house and we would like to insulate it to make it more livable in cold season. And preferably have it ready and functioning before I build a natural house on the other side of the garden.

Its a wooden house. I'm thinking about insulating all the walls, ceiling and floor with rock wool.

What are my alternatives for the price? I would prefer not to use and put a more environment friendly insulation but if the cost is too high or its simply not doable for me with simple work tools ill stick with rock wool.

Kindest regards,

-- Adrian
 
Brian Knight
Posts: 554
Location: Asheville NC
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Cellulose, fiberglass, spray foam

If youre not using spray foam, you will need to account for stopping air movement which is probably more important than the insulation.
 
Jay C. White Cloud
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Hi Adrian,

As far as a manufacture (industry based product) Rockwool insulation is probably one of the best. It is a very old product, over 140 years, so has a well proven tract record. It is a reclamation product taking waste out of the production stream, and has thermal characteristics that make it far superior to other products. Sheeps wool is another natural product, but only a few manufactures have gotten the "pest issue" sorted out...and it is much more expensive. Cellulose has really taken the insulation contracting world by storm...often without considering many factors. When (not if) it gets wet with the interstitial zones of a wall it just becomes a nightmare of a mess. Over the last 10 years we have ripped out 1000 of cubic feet of this product from walls that do not actually maintain the "air tightness" the contractor promise and moisture infiltration was trapped within the wall. In super insulation dense pack applications (over 300 mm thick minimum) and working in concert with perhaps another insulation like Rockwool board and not plastic wraps and vapor barriers you can achieve good results in net zero application with excellent permeability of the wall diaphragms. This later method is really advanced wall design and not generally for the novice to tackle as key elements have to all be well fitted to achieve zero drafts, and sealing around fenestration and other wall/roof openings must be expertly done. Superinsulation methods, achieving net zero architecture is the future form most well built homes.

So, for you project, I would recommend Rockwool, and/or urethane foam for a "commercial" insulative product, and perhaps a "light straw clay cobb" if you going the all natural route. Another nice aspect of Rockwool board is it can work in concert with all the natural materials to add additional insulation and draft proofing a structure. Clad the exterior walls in Rockwool board, then as you sheath the interior with horizontal boards you can infill with "light straw clay cobbing." Leave the boards as the interior finish or cover with paper plaster, lime plaster or related finishing system. Employ heavy boarding (50 mm to 150mm thick and you get the added bonus of more insulation and thermal mass combined. We have done several home this way with incredible results.

Good Luck and let us know if you have any other questions,

j
 
Bill Bradbury
pollinator
Posts: 684
Location: Richmond, Utah
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As usual, Jay is "on the money".
I use rock wool in the walls of nearly all my renovation/restoration work. In addition to the things Jay said, I like the way it fits in the bays(at least if it's framed tight) with no gaps and has a significant resistance to the internal air flow that can negate insulative ability in other products and it is just really nice to work with. I use an old bread knife.
For attic spaces, I like the ease and low cost of blown cellulose.
I also like to choose my own air/vapor barrier(smart membrane) and install it over the entire inside of the structure.
 
Dale Hodgins
gardener
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Location: Victoria British Columbia-Canada
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I'm in a wet environment and I seldom see problems with cellulose. Most of the houses that I demolish have been well maintained. Large overhangs are common and many of the older houses have no vapor barriers.

The most problematic insulation seems to be fiberglass. It's the perfect home for vermin and in a fire, it melts away like cotton candy. In sub zero conditions, fiberglass looses R value.
 
Jay C. White Cloud
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Thanks for posting this Dale......it really helps make my point!


I'm in a wet environment and I seldom see problems with cellulose...


Some (not most unfortunately today) are very well done. I have never had, nor colleagues, issues with our use of this material...is it the best available, that is subjective, yet my view and experience is cellulose works better in concert with other insulators if it is employed.

Large overhangs are common...


One of the most common denominators of every vernacular form of architecture I have ever studied...be it 200 years old or 2000 plus...You just can not beat large overhangs.

...and many of the older houses have no vapor barriers...


Boy...I can vouch for that!!!

Cellulose in a wall of a remodel in North Carolina...Some of the original cellulose from the late 60's early 70's no house wrap, no plastic vapor barrier inside either...Cellulose...bone dry and in good shape.

Two blocks away, bedroom and kitchen with bath near by, less than ten years old. Big mechanical venting system in the attic, and exterior "heat pump" cooling and heating system. Of course stick built and wrapped in Tyvek...I don't even want to describe the "ick" we found in the walls and rotting plywood from built up moisture...


The most problematic insulation seems to be fiberglass. It's the perfect home for vermin and in a fire, it melts away like cotton candy. In sub zero conditions, fiberglass looses R value.


Yep...and the biggest and longest running "con game" in the building industry...Couldn't agree more!!!
 
Dale Hodgins
gardener
Posts: 6795
Location: Victoria British Columbia-Canada
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I must have said something right, since I drew only friendly fire from Jay.

I used to work for Herman Goering (not the famous one, but he fought for Germany in WW2. Called himself Jakob). He couldn't get his head around the idea that moisture came from within the building. On a large horse barn insulated with cellulose, he laid the vapor barrier on top of the insulation. It brought the ceiling down within a year. The day I quit, he insisted that I should put a vapor barrier on the bottom side of 2x10 joists instead of on the soil in a crawl space. He cited the barn thing as evidence. I explained that the barrier had to be on the warm side. He said no, always on the bottom. I was 18 and Jakob was 65. He was really pissed off when the customer decided to do it my way. He got even madder when his son showed up and agreed with me. The horse barn incident bankrupted him. No insurance.
 
Jason Farnam
Posts: 1
Location: Upper Valley, NH
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Just ordered Sheeps Wool for two Tiny Houses I am building, was cheaper than fiberglass batts and/or rigid foam.
Will let you know how it goes!
 
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