Finishing a shed

[DIYDoug]

Hi folks, new to this forum and I need some opinions.  Bit of background, I have a cabin in Northern Saskatchewan (Canada) where winters get very  cold. Working on making it a 4 season cabin.  I just finished building a shed that will be used to house a water reservoir and pump. I built it with 2x6 so I will  be able to insulate it very well. A couple of things I'm trying to decide is 1 - how to finish the inside ie. Drywall (no mudding) or OSB and 2 - how to construct an insulated channel for the water line (pex) to run under and enter the  cabin? I have a 16ft run from the shed to where the line will enter the cabin. Can you provide me with some ideas? Thanks in advance.

[MountainDon]

Let's start with a question or two.

Okay, 4 season use, but full time or part-time?  Will the shed and water reservoir be heated?  If part-time use will the cabin be heated in between occupancies? 

As for the interior walls almost anything you like can work. 

[DIYDoug]

Part time use for now. Shed will be heated (need to figure out what kind of heater and how big as well) cabin also heated just enough so things don't freeze up. Thinking about running some kind of insulated  channel at ground level and come up into the cabin. Thoughts?

[Dave Sparks]

Don asked a good question. Part time is the most challenging to keep things from getting damaged in cold winters. Is there power?

[DIYDoug]

Yes, power is no problem. Just installed a subpanel in the shed. If there is some formula to figure out how big a heater I need (110v vs 220v and how many watts), that would help as well. Also radiant or forced air.

[DIYDoug]

Also, if it makes a difference, the cabin is on pilings and is about 2.5 ft above ground level with no protection from the elements under the cabin.

[MountainDon]

My solution to a part time use cabin (@8800 feet, frost depth maybe as deep as 36") was to install all the plumbing lines in a manner that ensured all lines drained to a few easily accessible low points. The low points were fitted with drain valves with tubing draining the water outside.

The water supply reservoir is buried outside. I built an insulated box above the manhole riser. I also insulated the ground above and around the buried cistern using XPS sheet foam, sealed and glued together with canned spray foam. It's like a box over the cistern, open end down. The side panels go to frost depth.  The water in the cistern stays at about 50 F from the heat of the earth rising up and being trapped by the insulation.

There is a small tank like found in an RV inside the cabin. I call that the "use" tank. We use a marine inline type submersible pump to transfer water from the cistern to the inside use tank. That pump has no foot valve so when it is turned off the water drains back down the supply line and into the cistern.  The cabin water distribution is handled by a Shurflo RV pump. That pump gets drained, the lines disconnected and blown out with compressed air when we leave the cabin. A drain line from the "use" tank, as well as one from the water heater, allows that water to be drained back into the cistern when shutting down.

That avoids the need to insulate the line from the cistern into the cabin.  Keep in mind that a water line that is not buried below frost depth will eventually freeze, even if insulated, unless heat is introduced into the water or the water is kept moving, or a combination of both.

There are some online calculators for estimating how many BTU's are needed. You enter size data and a few other things and they give an answer. Results vary. There is also a certain amount of guesswork. Like what is well insulated vs ordinary in terms of r-value and air sealing?

We did not have grid tie electric. Still don't. So, to me, it was easier to plan the build with no heating when we were absent. When we are there we have a wood stove and a propane wall heater.


Our cabin is elevated too, but only about 24inches between the ground and the lower edge of the floor joists. Ours is skirted with metal as a wildfire safety thing. Wildfires are common enough where we are and the winds a wildfire generate can blow large burning materials under a cabin and cause it to catch fire. For the same reason we used cement fiber lap siding, soffits and fascia, window and door trim and a metal roof.

When we arrive in winter we start the wood stove, fire up the propane heater, close the drain valves, pump water to the "use" tank, fill the water heater and turn its burner on. Then wait a few hours as the inside temperature climbs. We are insulated R25 floor, R20 walls, R50 ceiling and air sealed quite good. There is an exterior fresh air inlet for the wood stove. 

Leaving is more or less the reverse with the additional step of using the "hard plumbed" in-place air compressor to blow out the faucets and inside pump.

We are ten years into our mountain adventure and what we did has worked well for us. Ceramic tile floors. Walls are drywall and T&G pine. Ceiling T&G pine. The heat up and cool odd cycles have not produced any damages so far.

Oh, waste water drains to the septic and the sinks all use a waterless trap that is sometimes used in RV's. https://hepvo.com/   they may not be certified for residential use in many locales. Our toilet is a composting type, so no water used there, no toilet to winterize.

[DIYDoug]

Some good information there but several differences in the situations. My reservoir is above ground 300 gallons. I like the idea of the drain, just in case, but prefer to have it ready to go year round. Just looking for ideas to encase the supply line coming from the reservoir and going to the cabin (about 16 ft) so it doesn't freeze. Shed and cabin will be heated year round to just above freezing. Thinking about heat tape surrounding the line. Is that ok for pex? The line will then be boxed in and insulated. Any thoughts?

[NathanS]

If you don't want the water line to freeze, you will need to create an insulated enclosure that goes from the insulated shed, below grade and underground to the cabin, then another insulated enclosure from below grade up into the insulated cabin. Both enclosures need to be connected to the heated structures so they never freeze.

I'd go as deep as you can dig, then lay rigid foam on top that is at least 2' wide. Below grade, I would use XPS insulation. They say 1" is worth 1 foot of soil as a ball park. I would put down several inches.

If you read the frost protected shallow foundation guide for uninsulated structures, it would give you some intuition on how to protect that waterline.

I would use poly pipe and run it in flexible drainage pipe, you could always wrap it in heat tape that you could plug in if something ever goes wrong. The poly won't break if it freezes, any brass fittings will though. From shed to cabin I would use no fittings, just a straight run of poly.

This is all assuming you're not on permafrost.

[MountainDon]

I see the trench as a problem area. What is frost depth there? Can you go that deep? Can you place insulation in an inverted U shape with the two vertical legs going deep enough to trap Earth heat that will come from below?  Insulation only slows the heat flow from warm side to cold side. There must be some heat if it is just the natural heat from  below frost level.

I have been told, but not confirmed, that heat tape is okay with pex IF the heat tape does not have any adhesives. Fasten with zip ties. The reason given was the concern that chemicals in an adhesive may act detrimentally with the pex. But I have not verified the accuracy.

It may be just me but the energy used to keep an un_occupied space heated for longish periods goes against my nature. I explored several ideas involving heating and gave it up. Any foods we leave on site are stored in a "dry well" that has an insulated lid and upper section. Earth heat keeps them unfrozen.

Good luck. I'm interested in hearing how this works out. Maybe I worry too much.