Temperature experiment: heat-reflective blanket wall lining

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Banff Martin
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Temperature experiment: heat-reflective blanket wall lining

Post by Banff Martin » Thu May 31, 2012 2:33 pm

Hello,

This idea came to me just after my solo 8' igloo camping in BC. I understand why you cannot get an air temperature above freezing in a standard igloo, but what if you lined the walls & floor with 'emergency blankets' such that the blankets didn't touch the walls?

At least 3 such blankets would be needed for an 8' igloo, and they would need to be taped together at the edges with packing tape or some similar clear tape.

Installation would be an adventure. Every couple feet the blanket would need to be anchored to the wall. This could be done by:
1. Drilling a pencil-thin hole through the igloo wall
2. Taping twine to a spot on the non-reflective side of the blanket
3. Running the line through a 'washer' that is non-conductive such as wood
4. Running the twine through the hole in the igloo wall, so the washer is between the blanket & igloo wall
5. Tying off the twine to a stick on the outside of the igloo wall

Alternatively, a shock-cord support system from the right shape of tent could work as well.

Now of course this is a lot of tedious work to see if you can get 5 or 10 degrees above freezing, but it would be a really neat experiment if it panned out..!

Aside from the method of suspending the blanket, does anyone have comments on the physics of it and the odds of the concept making a difference to the temperature inside an igloo? (it would be another adventure to line the igloo floor with cardboard and place a reflective blanket onto that)

Thanks!
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Igloo Ed
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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Igloo Ed » Fri Jun 08, 2012 5:54 pm

In our snowcave days, we used to build under rocks so the ceiling wouldn't sag through the winter.
One winter we did try using spaceblankets and they made it a lot warmer but we had problems with the rock dripping on the blanket and then the blanket got pulled off the ceiling. Quite a mess, just threw it away after that.
The liner would need to be adjustable because not every igloo turns out the same shape.
With the lost space, a larger igloo would need to be built. As a base camp, it'd probably be worth the effort.
I do get my igloo above freezing with no problems. Generally 48F. at ceiling and 38F. at the floor.
Here's a picture of the old snowcave, just hanging down that far helped a lot:
SpaceBlankets.jpg

Banff Martin
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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Banff Martin » Sun Nov 18, 2012 12:21 pm

Neat!

I don't expect to be able to re-use the setup created, but at such a low material cost it isn't a concern.

The only design edit I have so far is that for the floor, I'll first cut/fit double-thickness cardboard on the floor, then tape the mylar emergency blanket material to that. I may doctor up the trench to some degree as well.

I've been given permission to build at a local ski hill, 200M higher elevation than the town of Banff. While a few days ago there was only 4-6" of now in the parking lot I hope to build on the edge of, with the right shovel I shoule be able to harvest more than enough to build with. As soon as it is built I hope to start this experiment. This will also be a refresher before building another igloo on the company campus, though it may be a while before we've enough snow there.

Build starting in 6 days..!
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Igloo Ed
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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Igloo Ed » Sun Nov 18, 2012 7:15 pm

Banff Martin wrote:Neat!

I don't expect to be able to re-use the setup created, but at such a low material cost it isn't a concern.

The only design edit I have so far is that for the floor, I'll first cut/fit double-thickness cardboard on the floor, then tape the mylar emergency blanket material to that. I may doctor up the trench to some degree as well.

I've been given permission to build at a local ski hill, 200M higher elevation than the town of Banff. While a few days ago there was only 4-6" of now in the parking lot I hope to build on the edge of, with the right shovel I shoule be able to harvest more than enough to build with. As soon as it is built I hope to start this experiment. This will also be a refresher before building another igloo on the company campus, though it may be a while before we've enough snow there.

Build starting in 6 days..!
If you are going to try to keep the trench warm, the biggest different would be getting the top of the door below the level of the trench bottom. That can be problematic, it requires very deep snow or at least building on a very steep slant. I think the better alternative would be an insulated door. I often tell people "something like an old couch cushion. A piece of styrofoam would work well if fitted very carefully but just the tiniest little leak creates a draft.
Things that get wet and come in contact with the snow, for prolonged time, will freeze to the snow/ice and can't be removed without it tearing. Synthetic materials don't freeze to snow.
If you can get this all sealed up and fitting nice, you'll be able to sit around in a T-shirt with a couple candles going.
It sounds you are thinking of building from a parking lot plow pile of snow. If it is an old pile and the snow has frozen again, it will be a lot more work and can be a nightmare if the parking lot was slushy when plowed.
Here's hoping you get more snow before building. We are not forecast for snow for the next week.

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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Banff Martin » Mon Nov 19, 2012 10:48 am

Thus far the parking lot hasn't been plowed; the 4-6" of snow is standing in this reserve parking lot.

If they offer to plow some snow for me I'll try to take advantage of that to build the base with, but never for the igloo itself. I saw what happens when you've a rock in an igloo wall facing the sun - it conducts the heat into the wall and melts down in slow-mo. :) Any time a plow is involved I expect gravel to get mixed into the snow.

I'll keep watch for an old couch cushion - that worked well for me in February.

We've got snow in the forecast most of the week here in Banff Alberta, though it'll get just above freezing some days. At the spot I'm looking to it is 200M higher than the town, so no snow should be lost. I hope you get yours soon!
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Igloo Ed
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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Igloo Ed » Mon Nov 19, 2012 7:07 pm

We are forecast fair weather until a slight chance of snow Sunday night through Monday. To late for my annual Turkey Day igloo. Sad, first time since 1982 I haven't had a snowshelter on Thanksgiving due to lack of snow. I've taken a couple years off due to family but not due to lack of snow.
Glad to hear you are supposed to get snow.
Heh, ya the gravel, in the woods it's the pine needles. Sounds that you are getting it figured out pretty good, fun times.

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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Kevin Brooker » Sun Nov 25, 2012 6:50 am

Since you know the interior dimensions why not sew up a liner beforehand. The shape of each panel can be a simple rounded triangle. To make a pattern find a large excersize ball and cover a quarter of it with duct tape or masking tape. Draw on the panel as 1/x (whatever you feel works and conforms to the fabric you have) and remove the tape which will give a scaled down pattern. Add in tabs along the seams and attach parachute cord. Use and arrow or some other thin and stiff pole to drive the cord through the sidewall of the igloo. Tension the liner by pulling the cords from outside the igloo. Lay the cords onto the outside and cover them with snow. They will freeze into the shell. This method will put a sphere inside your catnary but with a bit of modification the fabric can be adjusted to a more cat-like shape. Most fabric shops sell coated ripstop. Tape doesn't stick too well in the cold and any snow dust will render the surface un-stickable.

The liner might take away the feel of the igloo. I've built 11 footers with 2nd grade kids and the structure lasted most of the winter. The igloo was an outside classroom and storytime space for the kids. We leave a bench along 1/3 of the diameter for the teacher to sit and the kids flop on the floor. Old carpet scraps work well to insulate them from the cold floor. Put the carpet scraps into the storage bin and inside to keep them from becoming tiles and have at it.

Most of the work gets finished by adults after the kids spend 35 seconds each packing before they lose interest. The kids are good at bringing snow to adults using a bucket to fill the form when the height becomes too tall for 7 year old kids. We have the build time down to about 5 hours with 5 adults. More people usually means more build time as the rhythm of the process gets broken. For the amount of time and hassle it takes to put up bracing/take it down/construct it/store it/etc. for an overnight stoppage you might as well just finish the build. To keep the group build moving, find jobs for everyone. Packing is just one job. Hauling snow, lifting snow, bringing hot drinks and snacks, taking photos, manning the campfire, etc. are the ancillary parts of a group build most people forget about. 10% of those in attendance are interested in building, the rest want to participate in some respect but the actual hands-on doesn't make their socks go up and down.

Have some people make ice glasses for drinks afterwards. Always fun to have a scotch in a container you smash afterwards. What about ice lanterns. Find activities for most people are able to contribute.

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Igloo Ed
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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Igloo Ed » Wed Nov 28, 2012 5:18 pm

Kevin Brooker wrote:Since you know the interior dimensions why not sew up a liner beforehand. The shape of each panel can be a simple rounded triangle. To make a pattern find a large excersize ball and cover a quarter of it with duct tape or masking tape. Draw on the panel as 1/x (whatever you feel works and conforms to the fabric you have) and remove the tape which will give a scaled down pattern. Add in tabs along the seams and attach parachute cord. Use and arrow or some other thin and stiff pole to drive the cord through the sidewall of the igloo. Tension the liner by pulling the cords from outside the igloo. Lay the cords onto the outside and cover them with snow. They will freeze into the shell. This method will put a sphere inside your catnary but with a bit of modification the fabric can be adjusted to a more cat-like shape. Most fabric shops sell coated ripstop. Tape doesn't stick too well in the cold and any snow dust will render the surface un-stickable.

The liner might take away the feel of the igloo. I've built 11 footers with 2nd grade kids and the structure lasted most of the winter. The igloo was an outside classroom and storytime space for the kids. We leave a bench along 1/3 of the diameter for the teacher to sit and the kids flop on the floor. Old carpet scraps work well to insulate them from the cold floor. Put the carpet scraps into the storage bin and inside to keep them from becoming tiles and have at it.

Most of the work gets finished by adults after the kids spend 35 seconds each packing before they lose interest. The kids are good at bringing snow to adults using a bucket to fill the form when the height becomes too tall for 7 year old kids. We have the build time down to about 5 hours with 5 adults. More people usually means more build time as the rhythm of the process gets broken. For the amount of time and hassle it takes to put up bracing/take it down/construct it/store it/etc. for an overnight stoppage you might as well just finish the build. To keep the group build moving, find jobs for everyone. Packing is just one job. Hauling snow, lifting snow, bringing hot drinks and snacks, taking photos, manning the campfire, etc. are the ancillary parts of a group build most people forget about. 10% of those in attendance are interested in building, the rest want to participate in some respect but the actual hands-on doesn't make their socks go up and down.

Have some people make ice glasses for drinks afterwards. Always fun to have a scotch in a container you smash afterwards. What about ice lanterns. Find activities for most people are able to contribute.
Nice first post, Kevin. Your experience shows.
I particularly like your take on mixed age groups. If everyone can find a task they can feel happy about doing, building the igloo can be a great time.

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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Hiatus » Thu Dec 20, 2012 11:29 am

I think the objective here is two fold. First, increase the thermal efficiency of the igloo. And second, prevent or reduce the melting of the interior surface of the igloo. I think the foil faced insulator is a good idea if you don't mind carrying the materials.

It would be easy to loft the insulator based on the size of the igloo you plan to build. Pieces of the insulator could be velcroed together. This would allow more compact packing and easy field assembly. Also, strips of velcro could be inserted between blocks as you construct the igloo and these could be used to suspend the insulator dome inside the igloo.

If you do build one of these, I recommend poking holes through at the base of the igloo and at the top of the igloo. Combined with a gap between the igloo wall and insulator you should be able to prevent melting/dripping inside the igloo. You can control the air flow by blocking lower holes for the night or other times when the interior temps are lower and you want to reduce the heat load.

It'll be interesting to hear how the idea develops and if it proves itself.

Regards,

Tom

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Re: Temperature experiment: heat-reflective blanket wall lining

Post by Hiatus » Fri Dec 21, 2012 12:47 pm

I computed out the loft pattern for a radiant barrier liner on an 8' igloo. Ed's web site says these igloos have an 8' inside diameter and are 61" at the highest point. Based on that information I fit a catenary curve to the base diameter and peak height. Assuming rolls of the radiant bubble wrap barrier come in 3' widths, I figured you will need nine pieces 6' 8" long. That's 60 feet total.

To cut a pattern for the gores you will need some butcher paper or brown wrapping paper at least 3' wide. Cut a length 6' 8" long (80"). Fold it in half, keep it folded, and mark lines perpendicular to the fold every 10". Starting from one end mark a hash line across the bottom edge then each perpendicular line and the top edge at the following distances: 17-1/4", 16", 14-5/8", 13-1/4", 11-1/2", 9-1/2", 7", 4-3/8", and 1-1/8". Join the intersections with a smooth line and cut or just cut a smooth curve through the intersections.

Open the pattern and use it to cut 9 pieces of the radiant barrier. Then use velcro tabs to join the pieces together with 1-inch overlap at each joint. When you put all the pieces together they should form a doom approximately the shape of the inside of an 8' igloo. It may even be self supporting. The barrier dome will have an approximately 2" diameter opening at the top to allow for a ventilation hole plus it's impossible to have an odd number of gores come together at a single convergence point cleanly.

I just looked on line and found that this foil faced bubble wrap has an R-value of just over 1. You're probably better off spending the money on higher quality gear.

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