Multifoil...............

[Jeremy Harris]

I have a bit of a problem in my workshop, in that the dark grey, "insulated" roller door works as a very effective radiator, heating the workshop up a great deal.  It faces near enough South, and gets very warm, so warm that when standing next to it inside, with the door down, it you can feel the heat being radiated from its surface.  I can't change the external appearance (I had a struggle just to get approval for the door, as it is directly opposite a Grade II listed building) so whatever I do has to be inside.  I don't need to open the door very often, as most of the time I use the side door.

 

So, what I'm thinking of doing is to buy some multifoil "insulation", and make up an internal roller blind.  I have some lengths of alloy tube, including some fairly big (4" diameter) stuff.  There's around 300mm of so of room at the inside top of the door to take the rolled up blind.  Rather than have the blind roll around the tube at the top, I'm thinking along the lines of having it rolled around the tube at the bottom, with some nylon tapes run via pulleys, so that the blind will roll itself upwards, lifting the tube as it goes (we used to have a bamboo blind that worked like this).
 

I know that it's pretty poor insulation, in terms of thermal conductivity, but multifoil is very good at reflecting out long wavelength IR, so it is ideal for keeping radiated heat out.  As the roller door isn't at all well insulated (the slats are around 20mm thick aluminium extrusions, filled with foam) and as the door is full of high conductivity thermal bridges, I'm hoping that reflecting heat back towards the door will result in it heating the door up and so increasing the outward heat flow.  I can't easily seal the edges, but could add some boards either side that the multifoil blind could sit against, and if it were trapped under a batten at the top that should seal that area up OK.

 

The questions are, firstly, will multifoil tolerate being wrapped around a tube and rolled up and down?  I suspect it may do, as it's basically just alumised mylar (as used in "space blankets") with some think polymer fleece material between the layers.  

 

The second question is how best to join sections of the stuff together.  I need to make up a 3m wide blind, and the widest rolls seem to be around 1.5m or 1.6m.  I don't trust the sticky tape, as I doubt that it will tolerate being wrapped around a roller, so perhaps I need to look at using an overlapping multilayer approach, a bit like slates on a roof.

 

Anyone any thoughts?

 

Edited August 26, 2017 by JSHarris

[Guest Alphonsox]

In terms of joining sections together i would have thought the stickiest tape known to man - air tightness tape - would give a reasonable robust joint. You must have a roll or two lying around.

[Jeremy Harris]

Thanks, that's a good idea - I've got the best part of a roll of tape left over, too.  I can't think why I didn't think of it - I was sort of focussed on the aluminium tape, that I don't think would work.

Edited August 26, 2017 by JSHarris

[Guest Alphonsox]

One other thought as this is boffins corner - I have friends in California who use fine mist water sprays as an outdoor cooling system. As your water is effectively free how about rigging an external spray head to direct a water mist onto the door.

 

[PeterW]

How about sticky velcro..? Or get MrsJSH to run it through her sewing machine..?

 

You could then velcro the edges to the frame and also to each other

[Jeremy Harris]

Just now, Alphonsox said:

One other thought as this is boffins corner - I have friends in California who use fine mist water sprays as an outdoor cooling system. As your water is effectively free how about rigging an external spray head to direct a water mist onto the door.

 

 

 

Like the big "swamp coolers"?  I've seen them used to cool big marquees in the US, with a fan and atomising ring of nozzles.  Might work, but it would need to run most of the time.

[Jeremy Harris]

2 minutes ago, PeterW said:

How about sticky velcro..? Or get MrsJSH to run it through her sewing machine..?

 

You could then velcro the edges to the frame and also to each other

 

 

That's an even better idea.  It should be easy enough to sew velcro down the edges, and then use that both to hold the centre join together and fix the edges to the boards I could run down either side.  That would improve the thermal performance, too, by helping to seal the blind up and preventing convection.

 

What amazes me is just how much heat is radiated from the inside face of this door.  Even on an overcast day the door gets seriously hot, and on a sunny day it's too hot to touch at times.

[Onoff]

Run some Pex-Al-Pex over the back face, PIR over that. Some flexible tap tails and USE that heat! 

[Guest Alphonsox]

5 minutes ago, JSHarris said:

What amazes me is just how much heat is radiated from the inside face of this door.  Even on an overcast day the door gets seriously hot, and on a sunny day it's too hot to touch at times.

 

It's a shame to waste all that energy - shame it can't be used as a pre-heat for the ASHP or MVHR

[PeterW]

18 minutes ago, Onoff said:

Run some Pex-Al-Pex over the back face, PIR over that. Some flexible tap tails and USE that heat! 

 

on a roller shutter door...??????

[Onoff]

Just now, PeterW said:

 

on a roller shutter door...??????

 

MISSED that bit, there was a lot to read so I just skimmed it! 

 

Still.....how about silicon rubber tubing?

[MikeSharp01]

+1 for sewing. I, Mrs mike sharp actually, sewe'd two lengths together for the vaulted ceiling in my study here. Not sure how good the insulation was at the join and mine is fixed in place but it held together well as I stretched it into place down the slot prepared for it. 

[Jeremy Harris]

Sewing it is, I think.  Just need to find a place that will sell me around 5 or 6m of 1.6m wide multifoil at a reasonable price.

 

Using the heat would be nice, but the workshop is detached, at the other end of the garden from the house.  Also, when the workshop is getting warm, the house has more than enough heat, and the solar panels are generating like mad, so I wouldn't be able to usefully use the heat.

 

It'll be interesting to see how multifoil works at keeping heat out.  My gut feeling is that it may well work well in this role, as the stuff is pretty good at reflecting long wavelength IR, so is ideal for reflecting heat back out from very hot, largely radiating, surfaces.

 

 

[SteamyTea]

Is it worth trying out some aluminiumised mylar first, seem to remember that it is pretty cheap online.

 

If you remember my old solar tile experiment over at the other place (several years ago now, April 2010), the old aluminiumised crisp packets worked well.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5643&page=3&Focus=80703

 

 

Edited August 26, 2017 by SteamyTea

[NSS]

For just a moment there I thought it must be 1st April 

[Jeremy Harris]

9 hours ago, SteamyTea said:

Is it worth trying out some aluminiumised mylar first, seem to remember that it is pretty cheap online.

 

If you remember my old solar tile experiment over at the other place (several years ago now, April 2010), the old aluminiumised crisp packets worked well.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5643&page=3&Focus=80703

 

 

 

 

That's a good idea.  I've never been convinced that multiple reflective layers was much more than plain BS, as alumised mylar has both a very high long wavelength reflectivity and a very low emissivity.

 

Rolls of reflective Mylar film are pretty cheap, and a quick look at the characteristics shows that a single layer will be around 95% as effective as multifoil in this application.  Plus, being thinner it will be easier to roll up.

 

In fact, looking at the physical properties, it's hard to see why, other than marketing BS, anyone contemplated stitching multiple reflective layers together.  There is a direct parallel with a mirror - putting several mirrors, one behind the one in front, does not produce a better or brighter reflection.

[Ferdinand]

Are you a furniture making area?

 

Around here I could probably find a small setup that would do me a custom job using their industrial sewing machine.

 

If you are worried about the stiffness of the multi foil try 110mm soil pipe as your wrapping tube.

 

Ferdinand

 

[Jeremy Harris]

I've settled on some fabric reinforced alumised mylar film, and will look at whether I can just glue it together to get the required 3m width, or whether I need to sew it.  Luckily I have a small industrial sewing machine.  Rather bizarrely, my former employer sent me on a sewing course at a factory on the industrial estate in Pool, where I spent two weeks learning to drive a sewing machine, making ladies underwear, as they felt that anyone designing parachutes should know how to sew (I can sew underwired bras, and do a mean gusset.......). 

 

Rather than use velcro down the sides, to fix it to planks fitted to either side of the opening, I've decided to try magnetic strips, the sort of stuff used for fridge door seals.

 

As for the roller tube, I have a couple of 5m lengths of 4" x 16g aluminium tube, plus a 5m length of 2" x 14g and, somewhere, a length of 2 1/2" x either 14g or 12g (I can't seem to find it at the moment.......).  I have a feeling that a length of the 4" tube may well be the best option.

 

The plan is to fix two nylon tapes under the top fixing batten, that also secures the foil blind.  These tapes will then run behind (on the door side) of the foil, around the tube at the bottom (to which the foil is wrapped around and glued) and then back up to a couple of pulleys at the top, and then to a guide pulley at one side and down to a securing cleat.  I may add a motor, linked to the door opener, if the blind works.

[MikeSharp01]

3 hours ago, JSHarris said:

've settled on some fabric reinforced alumised mylar film, and will look at whether I can just glue it together to get the required 3m width

If I recall my time working with the ink industry the foil you need is avaliable that wide already.  The people who print the crisp packets have in up to 4m wide rolls. If you can find such a printer the end of the roll would be more tham enough for you. 

[Jeremy Harris]

10 hours ago, MikeSharp01 said:

If I recall my time working with the ink industry the foil you need is avaliable that wide already.  The people who print the crisp packets have in up to 4m wide rolls. If you can find such a printer the end of the roll would be more tham enough for you. 

 

 

Thanks @MikeSharp01

 

I did some impromptu tests yesterday afternoon, on some stuff I had lying around.  The alumised film used for crisp packets is just too prone to tear.  It's pretty strong, but the moment there is a stress raiser introduced, like a small nick, it tears very easily.  A space blanket I had in an old caving survival pack (I found it tucked inside my old helmet!) was a lot tougher, but still very thin, and I'm not sure that it would last that long.  A bit of silver breather membrane looked good, very tough, but it's IR reflectivity was only around 80 to 85%, so not ideal.  The best compromise seemed to be the cheap silver bubble foil, the stuff that has a fabric layer between the two alumised outer skins.  As far as I can tell, the outer skins are not Mylar, but something that behaves very like polyethylene terephthalate (PET) and this has the advantages of being pretty tough, flexible and tear resistant.  A quick and dirty test seems to show that it has a long wavelength IR reflectivity of around 95%, which should make a significant difference.  The clincher when it came to choosing this stuff was a quick search around YouTube, that found loads of videos of people insulating garage doors with the same stuff, usually from the US, and usually to keep heat out.

 

The other nice thing about PET is that it is reasonably easy to bond to, so using adhesive or self-adhesive materials should result in a reasonable long-term bond.