Converting to hard walls.

[Corey]

Hell All,

We live in a 30' yurt year round in northern New England. After 8+ years we are ready for more stable temperatures within our yurt and to be able to travel during the winter. (We currently only heat with a wood stove.)

We are thinking of wrapping the exterior wall of the yurt in plywood and covering with t & g boards. For the inside we would use the 2x4s that support the rafters to frame out a curved wall. The wall would have a vapor barrier and insulation. For the ceiling I am thinking of leaving the canvas as-is on the outside and on the inside place insulation in between the rafters, place a vapor barrier on top of that and then place t & g boards over that.

It all works out neat and pretty in my head but I am uncertain about some things:
1. In a traditional house you would have soffit to let air circulate between the insulation and the roof to prevent mold/mildew. I don't see how to add soffit here. The few pictures I've seen of insulated yurt roofs do not seem to have any special ventilation. Is this something to consider or is there an approach that would mitigate the risk of mold/mildew?
2. The one video I have seen of converting a yurt to hard walls show the owners pulling down the canvas before putting up plywood. This seems like the right approach but I wonder if the canvas can be left in place. New construction uses housewrap and I wonder if the canvas could be used for the same purpose or just left up underneath the plywood. (I know housewrap is supposed to allow water vapor to pass.)
3. Is there something else to consider? Has anyone else here attempted this?

Thanks.

 

[Bob Rowlands]

Any roof system packed with insulation that has no way to ventilate, and can get moist air from a kitchen, is going to be prone to water condensation -its a roof and roof get cold- and resultant mold. Air needs to pass over the insulation and draw moisture to the outside.

Case in point, we had friend that packed insulation between their 2x10 cut rafters in the vaulted LR and second story loft. No air space between the roof sheathing and insulation, and no gable ridge vent.

Mold ensued and they literally had black streaks running down the ceiling T@G boards. I advised them beforehand to go one size under on insulation, 8" batts in their 2x10 cut roof.

No dice. Well the interior t&g got torn out, insulation redone, plastic sheeting stapled to rafter bottoms, strip soffit vents and full ridgeline vent. Problem solved. btw I helped frame their house and worked on the cut rafter roof for one day.

 

[Corey]

Any roof system packed with insulation that has no way to ventilate, and can get moist air from a kitchen, is going to be prone to water condensation -its a roof and roof get cold- and resultant mold. Air needs to pass over the insulation and draw moisture to the outside.

Case in point, we had friend that packed insulation between their 2x10 cut rafters in the vaulted LR and second story loft. No air space between the roof sheathing and insulation, and no gable ridge vent.

Mold ensued and they literally had black streaks running down the ceiling T@G boards. I advised them beforehand to go one size under on insulation, 8" batts in their 2x10 cut roof.

No dice. Well the interior t&g got torn out, insulation redone, plastic sheeting stapled to rafter bottoms, strip soffit vents and full ridgeline vent. Problem solved. btw I helped frame their house and worked on the cut rafter roof for one day.

Thanks Bob, that fits with what I assumed. In Northern New England our roof will be cold a large part of the year. We have 2x6 rafters so we can definitely put in lower profile insulation so the space isn't fully stuffed. Any thoughts on how to fashion a soffit and gable vent design in to a yurt's canvas roof?

Thanks.

 

[Jafo]

You are going to have to be extremely careful about moisture. The only way I could even think of getting around it is enclosing the dome somehow from underneath so it could vent the ceiling without venting the entire room. Then you would have to fashion some kind of through the wall kit to connect outside air to the space between the ceiling and whatever insulation you put in.

There would have to be a gap between the insulation and the ceiling for airflow.

 

[Bob Rowlands]

Corey, I don't have experience doing that on a yurt. It would merely be guesswork.

Somewhat off topic, Mongolians lay down a light fabric liner over the rafters and then lay thick felts on top of that, then the cover over the felts. It works for them. I know zip about 'Americanized' yurt insulation. Sorry.

 

[Corey]

Thanks for your thoughts on this Bob and Jafo. Yeah, this is definitely out of the norm. We're just starting our long winter up here and this is a good research project for when it's too nasty to get outside. If we come up with some inspirations we'll definitely post them.

 

[Bob Rowlands]

If I lived in my yurt year around I'd leave it as a soft sided tent insulated with felt. Woodstove heat. Mongolian style. Partition the interior of 24' or greater as necessary.

As a retired pro residential carpenter I can tell you wood sheathing or siding of a curved wall and conic roof is gonna be a real trip. Lots of waste of material. Working with material that just does not 'want' to bend, and patience testing non stop fitty fitty fitty fitty work. Like building a wood sailboat, slow and tedious to the max. I just do not have the patience for dealing with that.

Myself, if I wanted hard siding and roof I'd just build a small conventional stick framed building, with a sleeping loft. Fast easy and relatively affordable. Standard insulation. EASY. Doable by non pro carpenters. Work in all respects is a snap, in comparison to non stop curves of a yurt. JMO. YMMV.

MERRY CHRISTMAS to you and all reading this thread!