Cabin design update

Oh, right. I have a blog.

Between a bit of a tenuous return to work after my flu episode (where I filled in for 2 people who quit and 4 more that also came down with seasonal plague) and the fact that I’ve been busy with a side project for a while, it’s been quite a few days since a real post.

I have been making a few strides in the cabin design in that I’ve finalized the overall layout of the interior and most of the left side framing layout is now complete. Which brings me to licensing: I want to make this design accessible to as many people as possible without making myself liable beyond the scope of due diligence. I.E. I want to do a good job making sure I cover all my bases with regard to structural integrity, but I don’t want to be sued into oblivion for my trouble.

The Cabin design will be Open Source

All the structural aspects of the cabin will be open to anyone to download (I’ll probably make a full download link available here), and modify for their own needs without having to pay me royalties. All I’m asking is for the copyright to remain intact.

That being said, I’ve been using a heavily modified ISC license for the past two times I’ve released any updates. This, I feel, isn’t really applicable to structure since these were originally meant for software. Being a software developer, naturally that was the first place I looked. I’m still using a heavily modified ISC license, but I’m open to suggestions on how I can license it.

I need to find or create a good license that will help me share my ideas without being subject to any sort of litigation. We’re talking about structure here and there’s a real risk of injury or worse if it’s done incorrectly. But I still want to let anyone feel free to modify it without too much legal wrangling while still indemnifying me.

Is it safe?

This has really been the question that’s stayed with me since I started on this journey.

I’m not a trained engineer, although I think I’ve taken reasonable steps to ensure everything is structurally sound, however I’m using OVE (Optimal Value Engineering) practices where applicable. I.E. 24″ On-center stud spacing, 6″ studs and using standard length materials (using 96″ studs as much as possible) to reduce weight, maintain proper insulation and still remain structurally sound to snow and wind loads. Also, I’m avoiding any cuts to the studs for the windows. The only cuts to the studs are at the front door and the bathroom entrance of the internal wall. I’m considering eliminating the center column by turning the bathroom wall into a load bearing one. We’ll see.

OVE is still somewhat controversial among builders for varied reasons. Some people believe it’s not as secure, others think you’re not really saving on materials, so there’s no “value”. My opinion is that the “value” comes with energy-saving. Granted you’re using less material, but this is not the primary benefit.

A sneak peek

Here’s the last sketch I did of the left side external framing layout. Note: The angle of the roof is approximately 50 degrees to accommodate year-round solar panels for the Northeastern U.S. This isn’t optimal since, ideally, you should be able to change the angle, but I don’t expect people to hop on the roof every few months to do that so this angle will have to do.

I’m still going with a 16″ x 16″ footprint with a 16″ x 8″ loft. Shaded in areas on the 1st floor are the support beams. See the previous foundation update for how they’re put together.

Left side cabin framing sketch

Left side cabin framing sketch

Special thanks to Kelly and her partner for offering me advice along the way.

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Pellet Stove 2.0

After yesterday’s post on designing my heating options for the cabin, I got a flood of the usual “you’re doing it wrong” emails. Not that I’m complaining, I actually found most to be very helpful and I’m grateful to everyone who took the time to write them.

Using some of the suggested improvements and a bit more browsing on YouTube, I came up with some modifications. One of the things that struck me after I made the initial post is that a pellet stove is basically a Rocket Stove on its side. It’s pretty much the same principle of thoroughly burning the fuel by mixing the air with the wood gas generated during the combustion process.

As with many pellet stove designs, this means it would benefit from a vortex generator; basically a static fan that sits in the flame allowing the gases moving past the blades to spin up (as opposed to an active fan which does the spinning). Also, the exhaust tube is much too small which can cause a potential backdraft through the cleanout or, more disastrously, out the hopper setting fire the rest of the fuel. The quicker I get the flames out the exhaust, the better it is. The gases will continue to combust in the exhaust tube as well, so really the burning process extends out the stove cabinet.

Stove 2.0 with improvements

It did surprise me that I didn’t really need a second starter burner to get the gases going up the flue. I thought this would have been absolutely essential to prevent a backdraft, but apparently, as long as the air is coming from below in the primary burner, the hot gasses will exit the larger opening. Flames travelling the path of least resistance and all.

One thing I overlooked in the previous design is how I’m going to clean the whole thing. No matter how “clean burning” Rocket Stoves are, I imagine eventually you’re gonna need to clean the tubes In the rare circumstance of an incomplete burn, perhaps due to incorrectly prepared fuel, you would still need the option of a cleanout. This is why I worry when I see elaborately constructed Rocket Stoves built into the dwelling. If things go wrong, you’re in a whole heap of trouble and have a humongous mess on your hands deconstructing the whole thing. A hole or two here and there to clean, couldn’t hurt.

I still have to decide how long I want the exhaust tube to be before connecting with the flue. Obviously, it can’t be too long since that runs the risk of a potential backdraft, but I also want to get as much heat into the living space before it leaves the cabin envelope. I’ll need to do some experimenting.

Now I need some welding lessons.

Heating the Cabin

This is just me thinking out loud. I may or may not use these ideas in my own cabin, but in case someone else is also looking for a place to start, they’re welcome to use them.

The space is so small, I can either easily turn it into a sauna or expend the same futile effort of a candle trying to heat a concert hall, so moderation is a big issue. Above all else, whatever method I choose has to be relatively self-governing since I don’t feel like waking up every 4 hours to replenish the heat (although I wake up every 4 hours anyway due to insomnia).

The first place I looked was, naturally, solar.

Electrical = No Dice

I quickly eliminated an electrical approach due to the excessive drain. No matter the output of any photovoltaic cell + battery combination, in-floor electrical heating or some sort of space heater would be too much of a drain on the power supply for the size of the cabin.  According to my current estimate of the South facing roof, I would have approximately 120 square feet to play with and even if I covered every inch of it with PVs, I don’t think it would be enough.

Also, if there is an extended period of overcast in the Winter, I’ll be in serious trouble trying to maintain the heat while toning down the drain of any other appliances. This sort of juggling feels like too much of a hassle and the whole point of this was to get away from stress. I want to enjoy those little luxuries like bright lights, induction cooker, a microwave and maybe a toaster every once-in-a-while without having to resort to Watt-pinching.

Solar Hot Air?

If this is supplementary to another method, then it works the best. There are countless examples on the web of solar heaters for the home, all with varying efficiencies and ease of construction. What I wanted was something that I know for sure I can build, won’t cost a fortune and will be reasonably effective without having to turn one whole wall into a collector.

And above all else I don’t want to have to notice that it’s there.

I then looked at solar heaters using Aluminum downspouts as collectors and came across the best iteration of it so far. What I really like about this concept is how low-profile it is. Granted he’s trying to heat a full house, basement and all, but I think I can get away with less than half this size since the overall cabin is small. Best of all, I don’t always have to look at it.

It would be a fairly simple affair to wire up a fan or two, a thermometer inside the cabin and one in the collector to a microcontroller and power the whole ensemble with photovoltaics. Computer fans typically run on very low power, most are fairly quiet and are designed for variable speeds making them the ideal choice, I think. Also, I can easily replace these parts without too much expense when they break down.

But as I mentioned above, this will only work as a supplement to something else for days that are overcast for long periods or (heaven forbid) if the cabin got struck by lightning and my arrester and breakers failed frying all the electrical stuff.

Small Stove

I’m a bit ambivalent about all the DIY stove designs floating around out there. On one hand, these are improvised designs, but on the other hand, these are improvised designs. There’s a reason why commercial stoves aren’t made of used air, Freon, LPG or similar pressurized tanks.

Regardless of origin, the traditional approach to a stove is basically a container to burn the fuel, a one-way air input control, a baffle to delay the hot gases existing before heating the surrounding air and finally, a flue. I think it’s time we started moving away from the traditional arrangements for this combination.

I want my stove to not look like a stove.

Traditional stoves have a quaint appeal that works well in rustic settings, but that’s not the look I’m going for. Besides the efficiency issues, traditional stoves take up more room and are fairly dangerous (especially for a clutz like me). In this vein, I’ve looked at these allegedly hyper-efficient Rocket Stoves which are all the rage these days.

They turn an ordinary flame into a twirling vortex of hot gasses inside the burn chamber, shoot inside an outer chamber warming the ambient air, then in turn can be vented under a bench for warmth before being exhausted outside. That’s quite a long list of opportunities to use the hot gasses for actual heat as opposed to conventional stoves where most of it is lost to the outside air.

Via Richsoil.com

Alas, the Rocket Stove also has the same problem: It looks like a stove.

If you need a demonstration of how one would construct such a stove simply, this gentleman had done so with ordinary household items. The demo is in Japanese, but the explanation is very well done visually so it should still be understandable.

It also takes up too much space and it feels like there’s way too much effort and mess to get an efficient heating system going. Besides that, it still needs that tendering that I don’t like so much as mentioned at the beginning of this post and the style is all wrong. For some reason, every Rocket Mass Heater I see reminds me of the structures on Tatooine.

I’m also more inclined to go with a biomass option for fuel since it gives me the greatest flexibility for automation. If I want my stove to shut off or limit itself by automatically (I’m fine with having to start it), then conventional — therefore odd sized — wood and sticks ain’t gonna cut it. I need a steady stream of fuel in a predictable size range that’s easy to manage while at the same time being environmentally friendly.

Pellets it is!

Not only do they offer the most flexibility in terms of fuel (I can use everything from grass, hard or soft wood to even plant fiber derived cellulose), it gives me the ability to control the flame without too much handling. More fuel + more air = more heat. Less fuel + less air = less heat. And that’s about it.

I’ve been thinking of applying the rocket stove idea to pellet fuel, but most of the rocket stoves I’ve seen require manual feeding of some sort. Besides, there’s the mess problem as mentioned above. I thought this can all be improved with something very simple like a chimney connected to a burn chamber by a tube of some sort that will act as the horizontal leg of the rocket stove.

Lo and behold, someone already came up with the same idea ages ago!

This video is also in Japanese, but the product demo is very visual as above.

What I really like about this is how simple it is and how inoffensive it is visually. Most of the hodgepodge rocket stoves I’ve seen look like they belong on Serenity, the spaceship, and not in a good way. While this is a testament to the improvisational capabilities of the builder, I don’t feel like I should improvise on safety.

By combining the Rocket Stove idea with some of the concepts of the above product, I figured I can build myself a stove that ran on pellets, doesn’t look like a stove (or at least is easy to hide that fact) and isn’t cumbersome to operate. So I set about designing a stove that does just that.

This is a quick sketch of all my ideas for an “automatic” pellet stove

If the pellet hopper has a lid, I can hide the whole thing as a piece of cabinetry or even use the top of the hopper as a small table. The air supply can be a feed from under the cabin so I don’t have to drill holes in walls and other nonsense. Also, by putting the air supply inside the cabinet, I can reduce the cold air leakage into the cabin from there.

Now that I look at this, I think the only “control point” necessary would be on the air supply. If I turn down the Oxygen, the burn rate goes down and so does the temperature. Though I’ll still need a shutoff for the pellets to completely stop the burner in an emergency.

I think I can hide the starter burner in a cabinet as well or I may not even need it if it turns out the length of the flue is enough. And the best thing about this design is that I don’t have to touch anything inside the cabinet until it’s time to clean the ashes. I’m sure I can automate this too somehow, but for now, this gives me the least amount of “homework” while operating the stove.

Just load with pellets, light it, walk away. Of course, I say that now, but we’ll see how well this will turn out.

Build Outside to Inside (goes for design as well)

This is an age-old adage that really should be hammered into every would be architect and amateur alike. Your interior, while you will be facing it more of the time, will depend on what’s done on the outside. That’s your envelope, your boundary, your line in the sand. Well, proving to myself that I am an amateur at this, I realised that my previous floor plan isn’t going to fit exactly within the walls.

New Plan

I’m not scrapping the 1st floor plan entirely, but I knew I’ll be moving things around a bit after I drew the cabin exterior in profile. Here’s the left side view, which will see a some more editing after this.

Left side profile of the cabin.

Note there are 13 steps to the loft and to center with the landing window, I had to move the stairs over. I don’t want to cut studs, add headers etc… to fit the window which will create thermal bridges (not to mention add more work), so I want to fit the windows between studs whenever possible. I can widen the stairs and make extra storage space below, or do something else with the space. We’ll see…

Cabin design: 1st floor update

Well, that was quick! I got a flood of emails from a lot of interested people overnight after the last post and it seems there are few resources on the web (or few that are easy to find) that provide specific details on laying out a cabin with exact measurements. I think the biggest complaint was that most designs don’t take into account realistic use and habitation. Elbow room cannot be taken for granted!

The second biggest complaint was that few, if any, are free. I can understand this since time x effort = money and most people wouldn’t want to work for free. But I do want to share everything I can here as I see a real demand for people who can’t afford to hire someone to design a cabin for them let alone spend money on building materials.

A few people offered to pay me to do a design for them. I’m not a trained architect (there’s a shock!), but I try to make the best effort when making sure the design is sound. So I can’t in good conscience charge people for something that a real professional should be doing. As mentioned in my previous post, you do need to run these by a certified architect or engineer before any construction can begin, but if you do use these as a starting point to your own design, I’d love to hear about it.

You’re doing it wrong!

A few of the emails were from people who have built cabins, worked with plans or have studied architecture. They almost universally were not happy with the way I drew the blueprints. Well, as I mentioned in the layouts post, I know nothing about blueprints! This is quite literally the first blueprint I ever drew so, of course, there will be “issues”.

Taking their suggestions into account, I redrew the layout with proper measurements this time and a few fixes here and there plus an added window at the bottom of the staircase. I know there are still some rough spots, but this is a better attempt since the first one was only a few hours of work.

Walls weren’t clear enough in the first one and measurements needed to be provided to the center of every opening (doors, windows etc…)

Apparently in my previous drawing, my walls were not as clear as they should have been and standard procedure calls for all openings to be marked from one corner to its center and then to the center of each neighboring opening. A perfectly sensible way of doing things that I didn’t know about until today.

Thanks to everyone who made the suggestions.

After going over and over this design, I think I may move things around to get more floor space and open it up more. Not sure how exactly I want to do that yet, but I see the toilet being sent to another location. We’ll see how that will work.

Update 7:40PM. Final changes

I did end up changing the bathroom by making it smaller and more space efficient. The dedicated closet space was eating up far too much room inside so I did away with that and moved the toilet and sink. I still want to make sure all major bathroom parts are accessible. Since the space under the window wasn’t being used, I moved it to just above the toilet seat. Since this will be a raised bathroom, I can still run supply and drain lines for the sink and shower without too much difficulty.

This also allowed me to move the stairs further back and away from the front door, giving more open space.

The opened up space between the end of the staircase and the wall to the bathroom may house the electrical panel.

Besides creating space for an electrical panel or other such utility feature, there is now more space beneath the window at the bottom of the stairs. This is an important safety consideration since you don’t want windows too close to the floor. This also means the front door is not crowded as it was before by the stairs and if someone tall uses the bathroom, they won’t feel like ducking when they get under the stairs (even though there would still be ample room overhead, this will be a psychological barrier to feeling comfortable). Head room (real or not), like elbow room, cannot be ignored.

Coming soon: The 2nd floor…