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This review reflects my initial impressions of these products. I should stress that they are without any real world tests as of yet. In the last two days I purchased a couple of 'Heat Sheets' brand name emergency blankets from Adventure Medical Kit and then went on to purchase the Thermolyte 2 Emergency Bivvy made by the same company. The emergency blankets were purchased in two sizes, a double and the single size. The costs were $6.50 for the large (2 person) and $4 for the 1 person model. The Thermolyte 2.0 emergency bivvy was $30.00.
Here is a shot of the three pieces in their packaging:
Weight and dimensions:
Bivvy is 6.5 oz, 84" x 36"
Emergency blankets: 3.5 oz, 96" x 60" (2 person) and 2.4 oz, 84" x 56" (1 person)
Review Heat Sheets Emergency Blankets
The heat sheets are packaged in this flexible plastic case (shown in the picture above) that is puncture resistant. You can ditch the case, but I think it provides a lot of additional protection at a small additional bulk. The case can be compacted more and packed tightly in confined spaces. I like the case and think it is worth the slight increase of volume. Also, having that extra bit of volume to the case makes folding the blanket and shoving it back in its container much easier. Has anybody every gotten a mylar one back in its original little ziplock? Having unfolded and folded up these blankets a couple of times, they are easy to use and re-use!
The blanket itself is reflective on one side and bright orange on the opposite side for high visibility. The orange writing on the back side contains emergency and survival tips for shelter building, fire and first aid. The writing, particularly on ways to set up your shelter is particularly helpful and well written. I think Siguy uses one of these on his outings - but I'm not sure.
This material is plastic, very much like a plastic garbage bag compared to the typical mylar emergency blanket. If you poke it with your finger, it deforms just like a typical kitchen garbage bag will behave. I didn't want to poke a hole through mine, but I imagine it has about similar overall strength to a kitchen garbage bag (single walled not doubled up). The package claims that the plastic heat sheets are 'more durable' than mylar ones. My guess is that the mylar ones are stronger in tensile strength but more prone to tearing, particularly when they have been folded for years in the original packaging. Once mylar starts to tear it quickly rips through the entire length. The heat sheets won't behave like this, it will deform and rip at the position where it is being pulled just like your garbage bag will behave. My opinion is that the material of the heat sheets will not be prone to degradation or fold memory while folded in its packaging.
Another advantage of the plastic material is that it is less noisy than mylar - which crinkles when it is rubbing against itself. That might not mean much when used in emergency scenarios, but if you are using it as a ground sheet or as a tarp, less noisy is better IMO. I don't know how well the heat sheets will behave if hit with sparks nor how this would compare with the behaviour of a mylar-type blanket.
Here is the double person version folded out, with my pack sitting on it:
It is a nice size! It can act quite nicely as a ground sheet or be configured into a small tarp for rain protection. The 8' length provides good coverage for different hanging configurations. Unfortunately, at only 5' in width, you won't be able to build a folded shelter that fully covers you. I wish they made an 8' by 6.5' size to provide a more versatile shelter with better hanging options. As a ground sheet, the size seems perfect! Also, used in its intended configuration - blanket wrapped around two shivering people - it is quite good.
The small sized one is similar but 7' x 4'8". It really isn't very useful as a tarp in itself, but could be effectively used to waterproof the roof of a natural material shelter. As a blanket it is a good size.
Overall Heat Sheets: These are good products at a bargain price. Sure, you could purchase a box of the large orange garbage bags but you won't get the advantages of the IR reflective material. Also the script on the orange side can be helpful, even if it is just to clear your head when a situation arises (the critical stop, think, and assess part). Likewise, they are a bit easier to refold and re-use than a mylar one and quieter during use. Unfortunately, durability will not be high for these things. They will work in a pinch but I wouldn't count on getting multiple uses of the emergency blankets when used in a tarp configuration or as a ground sheet. In other words - they are no replacement for an actual tarp but will work for multiple uses as a blanket. If deciding between the two - there is no question - get the 2 person heat sheet. It is much more versatile than the single person and only costs $1.50 more!
Review of Thermolyte 2.0 Emergency Bivvy
Now this is a really great product. An enclosed waterproof, windproof bag with some additional insulation value. At 6.5 oz and 84" x 36", it folds into a compact stuff sack. The material is far stronger than the heat sheets. You can tear it up with your hands if you tried. My guess is that it has the strength of about 3 sheets of garbage bag material. The bivvy comes in a small nylon stuff sak much like a sleeping bag stuff sac. It is light and small and won't take up too much room in your pack, or tied to the outside.
The bivvy is lined with a light fibrous inner coating that is supposed to provide additional thermal value beyond the heat reflection (IR) attributes provided by the silver coating. In other words, this bivvy has an R-value to it unlike the heat sheets which provide little or no insulative value on their own outside of reflecting IR. It is supposed to provide comfort to 50oF on its own. Provided you are wearing clothing (not-wet), the bivvy will provide a comfortable shelter in a variety of weather conditions.
The Bivvy is tube shaped about the same size as a long cut sleeping bag. It is slightly tapered, mummy style, but not aggressively tapered. I was able to enclose my entire body in it, including fully covering my head up with the material. I'm 5'10" and 200 lbs and there was enough room to take in a blanket or small sleeping bag. A 6' person could easily fit inside of one of these, you just wouldn't have the extra material wrap behind your head like I did. Since I was alone, here is a shot of the bottom half of the body in the bag itself. Lots of room!
The opening splits along the side about 1/3 of the length and is resealed once you are inside with glued on velcro tabs.
Finally, at the foot, there is a mesh window that can be opened up or sealed with velcro tabs to supply ventillation and keep condensation down.
The bivvy can be used as sleeping bag liner (i.e. inside the sleeping bag) to add about 10 degrees to the rating of the bag. If you have a small compact sleeping bag, quilt or wool blanket, you can fit it inside of the bivvy provided you aren't one of those guys whose bulk fill the entire bag.
I'm particularly impressed with how durable this product is. With a little care, e.g. using a ground sheet, I think it can safely be re-used over and over again. At this stage this is only opinion and I haven't used it in real world tests yet, but at least you know that I have enough confidence that I going to try doing this!
Overall - at $30 this is a good functional bivvy sak that transcends the 'emergency use only' designation. It has some ventilation design features which reflects one of the main improvements made over the initial release of the product, that and some weight savings. It is about half the weight of a designated full-on gortex-style bivvy sack but clearly is not in the same category of waterproofness, durability or options like mesh to keep out bugs. Couple the Thermolyte-2 Emergency Bivvy with the two person Heat Sheet (as a ground sheet and with some partial tarp covering over the head area) and I'd say you can have a nice shelter with a total weight of 10 oz or 300 g.
I'd highly recommend purchasing this product. It is small enough to throw in as a daypack without much consequence and can be used as an effective emergency shelter. Coupled with a sil-nylon tarp or the double heat sheet blanket, it can be used for ultra-light shelter!
Here is a shot of the three pieces in their packaging:
Weight and dimensions:
Bivvy is 6.5 oz, 84" x 36"
Emergency blankets: 3.5 oz, 96" x 60" (2 person) and 2.4 oz, 84" x 56" (1 person)
Review Heat Sheets Emergency Blankets
The heat sheets are packaged in this flexible plastic case (shown in the picture above) that is puncture resistant. You can ditch the case, but I think it provides a lot of additional protection at a small additional bulk. The case can be compacted more and packed tightly in confined spaces. I like the case and think it is worth the slight increase of volume. Also, having that extra bit of volume to the case makes folding the blanket and shoving it back in its container much easier. Has anybody every gotten a mylar one back in its original little ziplock? Having unfolded and folded up these blankets a couple of times, they are easy to use and re-use!
The blanket itself is reflective on one side and bright orange on the opposite side for high visibility. The orange writing on the back side contains emergency and survival tips for shelter building, fire and first aid. The writing, particularly on ways to set up your shelter is particularly helpful and well written. I think Siguy uses one of these on his outings - but I'm not sure.
This material is plastic, very much like a plastic garbage bag compared to the typical mylar emergency blanket. If you poke it with your finger, it deforms just like a typical kitchen garbage bag will behave. I didn't want to poke a hole through mine, but I imagine it has about similar overall strength to a kitchen garbage bag (single walled not doubled up). The package claims that the plastic heat sheets are 'more durable' than mylar ones. My guess is that the mylar ones are stronger in tensile strength but more prone to tearing, particularly when they have been folded for years in the original packaging. Once mylar starts to tear it quickly rips through the entire length. The heat sheets won't behave like this, it will deform and rip at the position where it is being pulled just like your garbage bag will behave. My opinion is that the material of the heat sheets will not be prone to degradation or fold memory while folded in its packaging.
Another advantage of the plastic material is that it is less noisy than mylar - which crinkles when it is rubbing against itself. That might not mean much when used in emergency scenarios, but if you are using it as a ground sheet or as a tarp, less noisy is better IMO. I don't know how well the heat sheets will behave if hit with sparks nor how this would compare with the behaviour of a mylar-type blanket.
Here is the double person version folded out, with my pack sitting on it:
It is a nice size! It can act quite nicely as a ground sheet or be configured into a small tarp for rain protection. The 8' length provides good coverage for different hanging configurations. Unfortunately, at only 5' in width, you won't be able to build a folded shelter that fully covers you. I wish they made an 8' by 6.5' size to provide a more versatile shelter with better hanging options. As a ground sheet, the size seems perfect! Also, used in its intended configuration - blanket wrapped around two shivering people - it is quite good.
The small sized one is similar but 7' x 4'8". It really isn't very useful as a tarp in itself, but could be effectively used to waterproof the roof of a natural material shelter. As a blanket it is a good size.
Overall Heat Sheets: These are good products at a bargain price. Sure, you could purchase a box of the large orange garbage bags but you won't get the advantages of the IR reflective material. Also the script on the orange side can be helpful, even if it is just to clear your head when a situation arises (the critical stop, think, and assess part). Likewise, they are a bit easier to refold and re-use than a mylar one and quieter during use. Unfortunately, durability will not be high for these things. They will work in a pinch but I wouldn't count on getting multiple uses of the emergency blankets when used in a tarp configuration or as a ground sheet. In other words - they are no replacement for an actual tarp but will work for multiple uses as a blanket. If deciding between the two - there is no question - get the 2 person heat sheet. It is much more versatile than the single person and only costs $1.50 more!
Review of Thermolyte 2.0 Emergency Bivvy
Now this is a really great product. An enclosed waterproof, windproof bag with some additional insulation value. At 6.5 oz and 84" x 36", it folds into a compact stuff sack. The material is far stronger than the heat sheets. You can tear it up with your hands if you tried. My guess is that it has the strength of about 3 sheets of garbage bag material. The bivvy comes in a small nylon stuff sak much like a sleeping bag stuff sac. It is light and small and won't take up too much room in your pack, or tied to the outside.
The bivvy is lined with a light fibrous inner coating that is supposed to provide additional thermal value beyond the heat reflection (IR) attributes provided by the silver coating. In other words, this bivvy has an R-value to it unlike the heat sheets which provide little or no insulative value on their own outside of reflecting IR. It is supposed to provide comfort to 50oF on its own. Provided you are wearing clothing (not-wet), the bivvy will provide a comfortable shelter in a variety of weather conditions.
The Bivvy is tube shaped about the same size as a long cut sleeping bag. It is slightly tapered, mummy style, but not aggressively tapered. I was able to enclose my entire body in it, including fully covering my head up with the material. I'm 5'10" and 200 lbs and there was enough room to take in a blanket or small sleeping bag. A 6' person could easily fit inside of one of these, you just wouldn't have the extra material wrap behind your head like I did. Since I was alone, here is a shot of the bottom half of the body in the bag itself. Lots of room!
The opening splits along the side about 1/3 of the length and is resealed once you are inside with glued on velcro tabs.
Finally, at the foot, there is a mesh window that can be opened up or sealed with velcro tabs to supply ventillation and keep condensation down.
The bivvy can be used as sleeping bag liner (i.e. inside the sleeping bag) to add about 10 degrees to the rating of the bag. If you have a small compact sleeping bag, quilt or wool blanket, you can fit it inside of the bivvy provided you aren't one of those guys whose bulk fill the entire bag.
I'm particularly impressed with how durable this product is. With a little care, e.g. using a ground sheet, I think it can safely be re-used over and over again. At this stage this is only opinion and I haven't used it in real world tests yet, but at least you know that I have enough confidence that I going to try doing this!
Overall - at $30 this is a good functional bivvy sak that transcends the 'emergency use only' designation. It has some ventilation design features which reflects one of the main improvements made over the initial release of the product, that and some weight savings. It is about half the weight of a designated full-on gortex-style bivvy sack but clearly is not in the same category of waterproofness, durability or options like mesh to keep out bugs. Couple the Thermolyte-2 Emergency Bivvy with the two person Heat Sheet (as a ground sheet and with some partial tarp covering over the head area) and I'd say you can have a nice shelter with a total weight of 10 oz or 300 g.
I'd highly recommend purchasing this product. It is small enough to throw in as a daypack without much consequence and can be used as an effective emergency shelter. Coupled with a sil-nylon tarp or the double heat sheet blanket, it can be used for ultra-light shelter!
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Just off the cusp, I'd say if your waist size is less than about 42" then I think you could get away with fitting in one of these things comfortably with clothes and mabey a blanket. 
