A design for alternative housing

[Chuck Morrison]

On my web site I have posted a design idea for a house that I may never build. I thought I'd try putting a graphic of it on here and see if anyone else wants to pursue it.

http://www.greeleynet.com/~cmorrison/photos/spiral-house-east.jpg

The page that shows this and a few other views is http://www.greeleynet.com/~cmorrison/house.html

One of the reasons for a shape like this is to reduce the loading effect of the wind on the structure. The low side of the house would face the prevailing winds. In my case the winds are from the North, so the tall side can face South and absorb some passive solar.

Throughout the midwestern part of the US and Canada there are seasonal winds that can be brutal, often times hurricane strength. I've had several wind generators burn up or suffer other damage from too much wind out here. Flat rectangular walls take the full brunt of the wind where rounded walls will direct the wind around the structure. Unfortunately It's difficult to create a true round wall that one can put windows and doors into in most of these 3d computer programs, so I show flat walls in the drawings.

While the round structure can be interesting to build, the most challenging aspect of this design is the roof, which sits on an angled and spiraled wall. Just building a cardboard model is tough.

[Rob Beckers]

Hi Chuck,

It looks interesting!
In fact, it reminds me somewhat of the geodesic dome designs, yours is more practical to build and to use though. You get the same advantage of relatively small wall area (and heat loss) for the volume of the house. Roof construction shouldn't be an issue I would think, it is in effect just a regular level roof that's installed at an angle.

The downside that I can see is that passive solar would be more challenging. If you space those windows around the way you have them now you'll get overheating due to the rising/setting sun. I suppose one solution would be to carefully redistribute windows so they are predominantly south-facing. Another one is that you don't have much truly south-facing roof area for things like solar photovoltaics and solar hot water. Being off by a bit won't make much difference, but it might be beneficial to 'stretch' the south-side of the house a bit, instead of making a perfect circle. Along the same line of though, there's benefit in having a roof pitch equal to the latitude of the site. It would make it easy to mount solar electric/water.

Now, the part I don't understand is why you would be concerned about wind loading. Short of a tornado, it is not that hard to build a structure that withstands just about any normal wind of the mid-west. In the coastal areas hurricanes are another issue, even so it has been shown that proper building techniques can make a building very resistent. The current Florida building codes are an example of that.

-Rob-

P.S. We're up to about a dozen members at this time, so I suspect postings and replies will still be a bit slow. Please don't despair if you're not getting much response, yet. Your type of post is the thing this forum was meant for, so keep it coming and spread the word!

[Chuck Morrison]

Rob,
Thanks for the comments. I know it's a new forum and that is why I posted this. Hopefully we can all keep it a good place to exchange ideas on all the subjects listed.

About the design. I'm currently building a similar design, round, not spiral, with a 40 ft diameter. The house is enclosed except for the second floor south wall and the shingles are going on now. There is some insulation in the first floor ceiling. It's been pretty cold outside, as cold as -19F, and I've been able to make some guesses about passive solar heating in the round. I should mention that the round wall is constructed with "Perform wall (http://www.performwall.com)" Insulated concrete forms that are 12 inches thick. Lots of R value in the walls and some thermal mass as well. I have not yet installed the thermal mass under the first floor, so there is just dirt there.

The first observation is that it does not overheat at this point. The windows on the west side are loosing some heat while the east side is gaining it. So while there is heat gain during the entire day, it isn't as dramatic as you might think. I don't think modifying the circle for more southern exposure necessary as the only thing you'd be doing is concentrating the heat gain to a certain time of day (solar noon +/- a few hours).

What the windows are, size and coatings (if any) affects solar heat gain. This house has 5 3ft x 6ft windows and one 3ft x 5ft along the east/south/west sweep of wall. Only one of them has no coating (a 20 year old "new" window), the other five have a solar heat gain coefficient of .60, which was the best I could find in new windows without special ordering them. Most new windows have a SHGC of .32. There would be more gain with untreated windows, but also more heat loss, It seemed like a reasonable trade off since we got the windows for a very good price, but we'll see.

About PV, hot water, etc. My electrical needs are supplied by 1.3kw of PV panels mounted on the barn roof (about 125 ft away from the house) and on a zomeworks tracker in front of the barn. I have an old 3kw Jacobs wind turbine that I will put up sometime to add to additional electrical needs. It has been my intention to put solar hot water panels on an addition to the house, but we'll see where the money comes from. Back up will be probably be propane.

Yes, I'm paranoid about the wind. I live on the eastern plains of Colorado and have experienced over 80mph winds at this site for almost 5 years in a row. I grew up in a nearby town that experienced over 100mph winds almost every year. That is hurricane strength. I saw houses destroyed by the wind. We won't even mention what it does to trailers. Wind load is an important factor in this setting so designing to minimize wind damage is just a smart thing to do out here.

Another aspect of wind is that when the wind pushes on a flat surface, not only does it create a load, the increase in the pressure causes increased air infiltration. When it's a cold north wind it drains the heat in a house. I've lived in lots of houses that were fine until the wind blew and then it got really cold inside. A round building avoids those issues since the wind flows around it without building up that pressure. My experience with wind so far this fall is that it has very little heat draining effect on the building.

Chuck

[Rob Beckers]

Just a few notes...
My comment about concentrating windows on the south side had more to do with preventing overheating because of west-facing windows. Sounds like you're good though.

That old Jake wind genny is something to hold on to. They are good turbines!

So does this house have the sloping roof design you showed in the first post? If so, how is it being built? Stick-frame? SIPs? Other?

-Rob-

[Chuck Morrison]

Just a few notes...
My comment about concentrating windows on the south side had more to do with preventing overheating because of west-facing windows. Sounds like you're good though.


Yes, it is a concern. We have a fairly large window on the South west side but so far it's far enough south and not enough west to be an issue. It may be a spring/fall issue, but we'll have to see what happens when it's all insulated and livable.

That old Jake wind genny is something to hold on to. They are good turbines!


It's a nice unit. Pretty heavy though, One reason I've delayed putting it up is that I'll have to hire a crane to get it up on the tower, Michael Hackleman's wind genny raising techniques scare me when there's a 500 lb turbine involved.

So does this house have the sloping roof design you showed in the first post? If so, how is it being built? Stick-frame? SIPs? Other?


Yes, although it doesn't go across the entire circle, just the south 2/3s of it. Basically it's a dormer utilizing 4 of the 12 roof sections. I'll post some pictures of the structure and how its done in a separate section when I have time.

[James Jarrett]

There is a company that makes houses very much like that. Go to:

http://www.deltechomes.com/?src=overture

They are in Asheville, NC and my wife an I toured their fabrication factory floor. They don't use ANY particle board or OSB, all high grade plywood. And their walls are THICK and SOLID.

Althogh they were more expensive than I could afford I would HIGHLY recommend their product. They are built like tanks, and I loved their models.

If you find yourself in NC, look them up. Worth a trip

James

[Chuck Morrison]

There is a company that makes houses very much like that. Go to:

http://www.deltechomes.com/?src=overture


I'd also point out mandala homes (http://www.mandalahomes.com/), in Canada. I haven't seen either maker's homes personally, but I like what I see on the web site. There was another one in France I think that had some outstanding pictures of interiors, but I can't find it now.

Just to be persnickity I'll point out that none of these are actually round (including the design I submitted). They are multi sided buildings with flat walls of varying lenths. I only point this out because placement of windows and doors is limited. In the design I show I put windows and doors in the center of each wall panel and I see these builders do the same. In a truly round building you wouldn't have to adjust your floor plan or window/door placement to suit the wall shape.

[Joe Blake]

I'm a fan of the (true) geodesic dome myself.

Just for something to do I designed (to put it grandly) and built this little "weekend camper" made of PVC piping, in 1998. Although the plastic covering has been shredded by time and weather, the frame is still intact, still standing, exposed to the worst weather offered over here (particularly sun) and after nearly a decade is still strong and flexible enough to support my 100 kg mass (spreading the weight over the frame).

I've devised a new method of construction which means that I can do a lot of the tiresome assembly work in the comfort of my living room, rather than doing everything in the field, as in the current frame.

The entire structure was carried (in about 3 trips) on my small motorcycle.

I'm not thinking of living in a PVC frame permanently, but I think they would be very useful for emergency shelter, since they can be constructed using nothing more than a hand saw, pair of wirecutters, a hand drill with holecutter and paper and pencil (and maybe compass/dividers and set square for constructing the necessary pentagon and hexagon templates.)

The total cost was under $300 Australian.

My current design attempt is going to be slight larger (probably about 3 metres diameter) with concentric domes to give an airspace for fitting insulation. The idea is to have the longer struts in the inner dome the same length as the shorter struts of the outer dome so there will only be three different strut lengths in total.

The covering will probably be a lightweight canvas (machine sewn) and then "doped" with gloss house paint. I've had a piece of doped fabric hanging on my outside clothesline for over 3 years, and it still will not let water through or tear. I haven't even had to "re-dope" it in that time.

Joe

[Chuck Morrison]

Joe,

I like your hub idea. While I'm not a fan of geodesic domes in general, I dream of leaking roofs, I enjoy seeing creativity and new ways of doing things.

Is the hub two concentric pieces of pipe or is the larger one a cap ?

Chuck

[Joe Blake]

The two larger pipes are concentric hubs and the third piece of pipe sitting outside the hubs is actually a "footer" for the struts to rest on. Due to the difficulty of maintaining the footer in position during assembly, I found I had to "sew" it in place with fishing line, which you may be able to see in the top photo. Once the last strut was pinned into place everything became rigid and generally stayed in place. However, once this transformation had taken place, it then became obvious that the footer was redundant, since there is very little compression in the frame, only tension, and my next design has dispensed with the footer.

I don't have a photo to show you, but each strut has three "collars" made of PVC pipe of slightly larger diameter (not quite a tight fit - but it doesn't need to be) held in place by self-tapping screws. One collar is on the end of the strut "stub" inside the hub, the next collar is in between the concentric hubs and the third is on the outside of the hub, a longer piece of collar than the other two and I then slide the strut into this collar and use two self-tapping screws to hold it in place. This way I can use the same hubs to build a dome of any size, the only variable being the length of the strut. The theory is that the tension of each strut will be diffused over two hubs instead of just one, as in the first design with the wire pins. I must have realised this all the time, but couldn't see the obvious, because I used two hubs in the initial design but couldn't think of a reason why I had two when only one was needed. However, after a storm when the dome was blown over and hit a tree, one of the hubs fractured, apparently through torsion rather than straight tension, I decided that the second hub had a use and I'd better find out what it was. Further, I increased the length of the hubs to give more "meat" and hopefully strength to the structure.

I also needed to fix the dome in place. The rope you can see in the top piccy is part of a "bridle" arrangement which has two tent pegs crossing each of the 10 horizontal struts at ground level, with the bridle being held under the pegs, then rising up to go over the next "level" of the frame, back down to ground etc. I've found, with the right soil structure, this method of fixing seems able to hold the frame to the earth immovably. It's been there since assembly and has not shifted, and nor can I budge it. In my first posting the photo shows ropes going over the top of the dome. These are actually to hold the tarpaulin in place, not the dome (although they obviously do assist in this.)

To build two concentric hubs, I merely increase the length of one of the two hubs for the "pentagon" hub (ie those at the centre of the 6 hubs with 5 struts) so that the two domes are actually sharing common pentagon hubs. Two structures become one.

If ever I get one built, I'll post some piccies. ;)

Joe

[Chuck Morrison]

Very interesting and it looks like a lot of work. I'm curious why you didn't glue the pvc hubs together. I'm sure there's some fitting that needs to be done, but it would seem that with carefully cut/drilled parts and some jigs gluing might be feasible for a permanent structure.

[Joe Blake]

Yes, Chuck it IS a lot of work, but it's only in the repetitive cutting, cutting, cutting (using a hand mitre saw) and drilling, drilling, drilling. (Power drill here).

I never considered glue because I never designed the structure to be permanent. However, it has been up now for a VERY long time, and is still "shipshape and Bristol-fashion", and so I don't think the extra time and effort of gluing it together is worth the effort.

If you look at the first photo VERY closely you'll see that end of the strut stub which is next to the footer is trimmed at an angle. The theory was that this would reflect the dihedral of the struts, and give the maximum "footprint" resting on the footer. Why this was important I've no idea, but it seemed like a good idea at design stage. A couple of things rendered this nugatory. Firstly, as I discovered once the entire structure was tensioned, the footers themselves were totally unnecessary (probably a "belt-and-braces" approach on my part) and secondly once everything was tension, I observed that the PVC pipe, with its inherent flexibility, adopted the correct dihedral regardless of the shape of the strut end. And considering that I had to trim each end of each strut, and there were over 70 struts, that was more than 140 extra bits of work with the mitre saw work I didn't have to do.

Your comments about carefully cut/drilled are noted, and was actually my biggest worry before starting, that I didn't have the necessary hand/eye coordination to achieve such fine workmanship as I believed was required, but when all was said and done, I think in many respects you could take a "near enough is good enough" approach and still wind up with a very serviceable structure.

I made up templates for 5 and 6 hole hubs, in the two sizes of hubs by cutting rings of PVC pipe, cutting across them and opening them up, and sliding them over the outside of an unopened piece of pipe, like a circlip almost, and then marking the appropriate drill holes. Thereafter I simply slipped the template over an undrilled hub, drilled through each of the 5 (or 6) template holes with the centre bit of a hole cutter, and in a matter of seconds, I had the holes in place. It was only once I started assembling the thing in the field that I discovered that my inner 5-hole template was actually inaccurate and had placed one of the holes in the wrong position, so that all 6 of my 5-hole inner hubs were wrongly drilled. I felt my stomach drop a few inches, but I ploughed on, and the structure in the photos still has those little defects.

I suspect I could have been a lot more sloppy than I was and still have succeeded. It seems to be remarkably forgiving.

In fact I think it's the sort of project you could give to a bunch of first year manual arts students to build, and they'd probably all get it down, even the "klass klutzes".

Regards,

Joe

[Chuck Morrison]

hmm, so do you think the holes need to be angled at all on the hub pieces, due to the flexibility of the spars ? It would seem that if there was just enough oversize on the holes it might line up pretty well.

I have to admit I'm intrigued enough to try it out. I have a (large) dog house to build and this might be the ticket. Pull a tarp or two over it and there you have it.

Chuck

[Joe Blake]

Chuck,

I don't think there's any need to drill at fancy angles. As I say I think it's a pretty forgiving sort of structure.

I've attached a couple of photos I took this morning with my web-cam. Not the best, but hopefully it will give you an idea of my new design. By using the two collars this puts the load onto BOTH hubs in tension AND compression. Hence no need for the footer. The struts then slip inside the external stub and are held in place by two self-tapping screws. If you're going to make a structure you're not going to put up and knock down often, the holes can be drilled practically anywhere. However, unless you wish to mark each individual strut for specific placement it's best to use a template to drill the holes, because then it won't matter where the struts go. (Note: Because of the use of self-tappers and the "soft" nature of the PVC pipe you don't need to drill holes in the struts proper, just the external collar. Once the strut is seated in place, the action of the self-tappers will start the hole for you.)

The other piccy shows one of the prototype templates I made for drilling the holes in the hubs. The red circled holes are for the "5-hole" hubs and the blue holes are for a "6-hole" hubs. However, there is always the risk of drilling in the wrong hole, so it would be best to make separate templates.

If you're going to do this a lot, I'd suggest making the template out of metal pipe, because the constant drilling eventually causes the holes to enlarge and become increasingly more inaccurate.

I'd be interested to see your dog house.

Regards,

Joe

[Joe Blake]

An additional thought.

I've never thought about making a smaller dome (eg a doghouse) but always bigger, and it strikes me that you come across a problem with the limited flex in PVC. When I buy it, it comes in 5 metre lengths, and one of the fascinating things I show people is I pick up one end of the pipe, and there's so much flex, the other end stays on the ground, and they generally find it hard to accept that you can build ANY sort of structure with it, let alone one that will stand up for nearly a decade. But of course the degree of flex is linked to the length of pipe. The shorter the strut, the less flex.

So I'd suggest there'd be a practical "minimum size" of dome that one could easily build. That's probably when the fancy angles of dihedral might prove useful. I think you're marching into unknown territory, Chuck.

Be interested to see what happens.

Joe